Influence of sex on the outcome of autologous chondrocyte implantation in chondral defects of the knee

Analysis of Patients Who Undergo Index Arthroscopy With Biopsy but Not Implantation for Staged Chondrocyte Cell Transplantation

Background

Autologous chondrocyte implantation (ACI) and matrix-induced autologous chondrocyte implantation (MACI) are 2-stage procedures requiring an index full-thickness cartilage biopsy. Only a portion of patients ultimately undergo second-stage ACI/MACI.

Purpose

To identify patients with articular cartilage defects who underwent arthroscopic debridement with biopsy for ACI/MACI and compare those who did with those who did not proceed with implantation within 2 years after biopsy. Additionally, the authors sought to identify why patients did not proceed with implantation.

Study Design

Case-control study; Level of evidence, 3.

Methods

Patients who underwent arthroscopy and autologous chondrocyte biopsy from January 1, 2015, to December 31, 2019, and who had minimum 2-year follow-up data were grouped into those who proceeded with second-stage ACI/MACI (implant group; n = 97) and those who did not (biopsy group; n = 63). Demographic factors, cartilage defect characteristics, and preoperative International Knee Documentation Committee (IKDC) scores were analyzed. Patients in both groups were evaluated postoperatively using the IKDC, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Single Assessment Numeric Evaluation (SANE), and visual analog scale (VAS) for pain, and patients who did not undergo implantation were asked for their reasoning.

Results

Body mass index (BMI) (P < .001) and Outerbridge grades at index arthroscopy (P = .047) were significantly higher for the implant group than the biopsy group. Both groups had significantly improved IKDC scores from their initial presentation to final follow-up (implant group: 46.4 ± 16.2 preoperative vs 69.6 ± 20.6 postoperative [P < .001]; biopsy group: 47.2 ± 15.9 preoperative vs 70.7 ± 19.1 postoperative [P < .001]); however, the level of improvement did not differ significantly between groups. Postoperative WOMAC, SANE, and VAS pain scores were also similar between groups. In the biopsy group, 23 patients (37%) cited symptom resolution or activity level improvement after initial arthroscopy as the reason for not proceeding with implantation.

Conclusion

Patients who proceeded to the second stage of chondrocyte implantation via either ACI or MACI had higher-grade articular defects and higher BMI compared with those who underwent biopsy with concomitant debridement chondroplasty alone. Postoperative outcomes were similar between the groups.

Cell-free biomimetic osteochondral scaffold for the treatment of knee articular surface lesions: Clinical outcomes differ based on patient and lesion characteristics

PURPOSE

A cell-free biomimetic osteochondral scaffold was developed to treat cartilage knee lesions, with positive clinical results documented in small case series. However, clear evidence on patient and lesion characteristics that might affect the outcome is still lacking. The aim of this study is to analyse a large cohort of patients treated with this scaffold to investigate factors that could influence the clinical outcome.

METHODS

Two hundred and three patients (mean age 30.7 ± 10.9 years) treated with this scaffold were prospectively evaluated at baseline, 6-, 12- and 24-month follow-up. The clinical outcome was analysed using the International Knee Documentation Committee (IKDC) score, and the activity level was assessed with the Tegner score. The influence of patient and lesion characteristics on clinical outcomes was analysed.

RESULTS

Mild and severe adverse reactions were found in 39.0% and 1.5% of patients, respectively. The failure rate was 2.0%, increasing to 12.3% when including also clinical failures. The IKDC subjective score increased from 43.3 ± 15.9 to 61.0 ± 16.2 at 6 months, 68.3 ± 18.5 at 12 months and 73.8 ± 18.3 at 24 months (p < 0.0005). The Tegner improved from 2.5 ± 1.7 to 4.2 ± 1.7 at 24 months (p < 0.0005), without reaching the pre-injury level (6.0 ± 2.2) (p < 0.0005). The IKDC objective score changed from 68.5% normal and nearly normal knees before the treatment to 90.1% at 24 months. At 24 months, age showed a correlation with the IKDC subjective score (ρ = -0.247; p < 0.0005), women had a lower score (p < 0.0005), as well as patients with patellar lesions (p = 0.002). Previous surgery correlated with lower results (p = 0.003), while better results were found in osteochondritis dissecans (OCD) compared to degenerative lesions (p = 0.001).

CONCLUSION

This cell-free biomimetic scaffold is a safe and effective treatment for cartilage knee lesions, offering positive clinical results at 2 years with a low failure rate. Better outcomes were observed in younger patients, in lesions of the femoral condyles and in OCD, while joints affected by patellar lesions, patients who underwent previous knee surgery, and women may expect lower results.

LEVEL OF EVIDENCE

III, Cohort study.

Do reconstructive techniques for osteochondritis dissecans of the skeletally mature knee work? A systematic review and meta-analysis

PURPOSE

Osteochondritis dissecans (OCD) is a common cause of knee pain. Management for adult-onset OCD (AOCD) usually involves surgery. Surgical treatments include palliative, reparative and reconstructive techniques. The aim of this systematic review and meta-analysis is to evaluate the efficacy of reconstructive techniques for the treatment of OCD in skeletally mature knees.

METHODS

A systematic search was carried out on four databases up to November 2023 (Medline, Embase, Cochrane Library, Web of Science). The study was registered on international prospective register of systematic reviews and performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Clinical studies on skeletally mature patients were included, which utilised reconstructive techniques such as autologous chondrocyte implantation (ACI), matrix-induced autologous chondrocyte implantation, osteochondral allograft transplantation surgery or bone marrow-derived cellular transplantation. Demographical data, patient-reported outcome measures and postoperative complications were recorded. Quantitative outcome measures that were comparable across studies were pooled for meta-analysis. A random effects model was used. Heterogeneity was assessed using the I2 statistic and Cochran's Q test. Statistical significance was set at p < 0.05. Risk of bias was assessed using the risk of bias in non-randomised studies - of interventions tool for nonrandomised studies.

RESULTS

Sixteen studies were included with 458 OCD lesions in 432 patients. The average age was 24.9, and 62.6% were male. The mean follow-up time was 61.5 months. At 36 months follow-up, International Knee Documentation Committee (IKDC) subjective, Tegner and EuroQol-visual analogue scale (EQ-VAS) scores improved from 42.4 to 78.6 (standard mean difference [SMD]: 2.47; p < 0.001), 2.27-4.99 (SMD: 2.363; p = 0.002) and 30.4-57.5 (SMD: 2.390; p < 0.001), respectively. Overall complication rate was 8.9%. Smaller OCD lesion sizes resulted in a greater improvement in IKDC subjective (SMD: 2.64 vs. 2.01; p = 0.038), EQ-VAS (SMD: 3.16 vs. 0.95; p = 0.046) and Tegner scores (SMD: 3.13 vs. 1.05; p = 0.007) and had a lower complication rate (p = 0.008). Males showed a larger improvement in IKDC subjective scores than females (SMD: 2.56 vs. 1.56; p = 0.029), while younger patients had a larger improvement in IKDC subjective scores (SMD: 2.71 vs. 2.12; p = 0.045) and fewer complications than older patients (p = 0.003). There were no significant differences between cohorts treated with ACI and those treated with non-ACI reconstructive techniques. Publication bias was not detected (n.s.).

CONCLUSION

Reconstructive techniques used to treat OCD in the skeletally mature knee resulted in significant improvements in clinical and functional outcomes, with a low overall complication rate. Since a younger age leads to a greater improvement in IKDC subjective score and a lower complication rate, surgical intervention should not be delayed, especially in AOCD lesions which are more likely to follow a progressive and unremitting clinical course.

LEVEL OF EVIDENCE

Level III.

Chitosan-based scaffold augmentation to microfractures: Stable results at mid-term follow-up in patients with patellar cartilage lesions

Purpose

Patellar cartilage lesions are a frequent and challenging finding in orthopaedic clinical practice. This study aimed to evaluate a chitosan-based scaffold's mid-term clinical and imaging results patients with patellar cartilage lesions.

Methods

Thirteen patients (nine men, four women, 31.3 ± 12.7 years old) were clinically evaluated prospectively at baseline, 12, 24 and at a final minimum follow-up of 60 months (80.2 ± 14.7) with International Knee Documentation Committee (IKDC) subjective, Knee Injury and Osteoarthritis Outcome Score and Tegner scores. A magnetic resonance analysis was performed at the last follow-up using the Magnetic resonance Observation of CArtilage Repair Tissue (MOCART) 2.0 score.

Results

An overall significant clinical improvement in the scores was observed from baseline to all follow-ups, with stable clinical results from 24 months to the mid-term evaluation. The IKDC subjective score passed from 46.3 ± 20.0 at baseline to 70.1 ± 21.5 at the last follow-up (p = 0.029). Symptoms' duration before surgery negatively correlated with the clinical improvement from baseline to the final follow-up (p = 0.013) and sex influenced the improvement of activity level from the preoperative evaluation to the final follow-up, with better results in men (p = 0.049). In line with the clinical findings, positive results were documented in terms of cartilage repair quality with a mean MOCART 2.0 score of 72.4 ± 12.5.

Conclusions

Overall, the use of this chitosan-based scaffold provided satisfactory results with a stable clinical improvement up to mid-term follow-up, which should be confirmed by further high-level studies to be considered a suitable surgical option to treat patients affected by patellar cartilage lesions.

Level of Evidence

Level IV, prospective case series.

Factors Affecting Choice of Surgical Treatment of Cartilage Lesions of the Knee: An Analysis of Data From 5143 Patients From the German Cartilage Registry (KnorpelRegister DGOU)

Background

Symptomatic full-thickness cartilage lesions of the knee joint are considered an indication for cartilage repair surgery. Patient- and lesion-specific factors like age, nutritional status, etiology of defect, or integrity of corresponding joint surface remain controversial in indicating cartilage repair surgery. Furthermore, the selection of the most suitable cartilage repair technique for a specific cartilage lesion remains debatable.

Purpose

To evaluate indications and choice of treatment method for cartilage repair surgery, depending on patient- and lesion-specific data from the German Cartilage Registry.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A total of 6305 consecutive patients who underwent cartilage repair surgery of the knee evaluated and 5143 complete datasets were included in the analysis (follow-up rate, 81.5%). Patient-specific (age, body mass index, smoking status, previous operations, clinical leg axis) and lesion-specific (size, grading, location, etiology) data were provided by the attending surgeon at the time of surgery. Appropriate statistical tests were used to compare data depending on type and normality of data. Multivariable logistic regressions were calculated to investigate independent factors for the choice of specific cartilage repair techniques.

Results

The median size of treated cartilage lesions was 3.6 cm2, and most defects were of degenerative origin (54.8%). Of the registered patients, 39.2% were categorized as overweight and 19.6% as obese, while 23.3% were smokers. The most prevalently documented operative techniques were the autologous chondrocyte implantation (ACI) (52.4%), bone marrow stimulation (BMS) (17.3%), and BMS augmented with collagen scaffolds (9.3%). Independent factors that made the use of ACI more likely were bigger lesion size, previous surgery at the joint, and lesions located at the trochlea or the patella. On the contrary, BMS or augmented BMS were preferred in older patients, with damaged corresponding joint surface, and with more concomitant surgeries.

Conclusion

Cartilage repair surgery was indicated irrespective of nutritional status, smoking status, or etiology of the treated lesion. ACI was the most prevalent technique and was preferred for younger patients and patellar lesions. While older patients with degenerative changes to the joint were not excluded from cartilage repair surgery, the use of ACI was restricted.

Increased risk of reoperation and failure to attain clinically relevant improvement following autologous chondrocyte implantation of the knee in female patients and individuals with previous surgeries: a time-to-event analysis based on the German cartilage registry (KnorpelRegister DGOU)

PURPOSE

This study aimed to analyze the risk of reoperation following autologous chondrocyte implantation (ACI) of the knee utilizing third-generation ACI products in a time-to-event analysis and report on the associated patient-reported outcome measures (PROM) in case of reoperation.

METHODS

Patients undergoing ACI were included from a longitudinal database. Patient age, sex, body mass index (BMI), number of previous surgeries, lesion localization, lesion size, symptom duration, as well as time and type of reoperation was extracted. A cox proportional-hazards model was applied to investigate the influence of baseline variables on risk of reoperation. Reoperation was defined as any type of subsequent ipsilateral knee surgery, excluding hardware removal. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was utilized to compare PROM between patients with and without reoperation.

RESULTS

A total of 2039 patients were included with 1359 (66.7%) having a minimum follow-up of 24 months. There were overall 243 reoperations (prevalence 17.9%). Minor arthroscopic procedures (n = 96, 39.5%) and revision cartilage repair procedures (n = 78, 32.1%) were the most common reoperations. Nineteen patients (0.9%) reported conversion arthroplasty at 17.7 (10.4) months after ACI. Female sex (HR 1.5, 95% CI [1.2, 2.0], p = 0.002) and the presence of 1-2 previous surgeries (HR 1.5, 95% CI [1.1, 2.0], p = 0.010), or more than 2 previous surgeries (HR 1.9, 95% CI [1.2, 2.9], p = 0.004) were significantly associated with increased risk of reoperation following ACI. Significantly less patients surpassed the minimal clinically important difference (MCID) in the reoperation group at 24 months regarding the KOOS subscores pain (OR 1.6, 95% CI [1.1, 2.2]), quality of life (OR 2.2, 95% CI [1.6, 3.2]), symptoms (OR 2.0 [1.4, 2.9]), and sports (OR 2.0 [1.4, 2.8]).

CONCLUSION

Female patients and individuals with a history of previous surgeries face an elevated risk of requiring reoperation after undergoing ACI, which is associated with failure to attain clinically relevant improvements. A thorough evaluation of the indications for ACI is paramount, particularly when patients have a history of previous surgeries.

LEVEL OF EVIDENCE

Level III.

Comparison of Hydrogel-Based Autologous Chondrocyte Implantation Versus Microfracture: A Propensity Score Matched-Pair Analysis

Background

Few studies exist for large defects comparing matrix-associated autologous chondrocyte implantation (M-ACI) with other cartilage repair methods due to the limited availability of suitable comparator treatments.

Purpose

To compare the clinical efficacy of a novel hydrogel-based M-ACI method (NOVOCART Inject plus) versus microfracture (MFx) in patients with knee cartilage defects.

Study Design

Cohort study; Level of evidence, 3.

Methods

Propensity score matched-pair analysis was used to compare the 24-month outcomes between the M-ACI treatment group from a previous single-arm phase 3 study and the MFx control group from another phase 3 study. Patients were matched based on preoperative Knee injury and Osteoarthritis Outcomes Score (KOOS), symptom duration, previous knee surgeries, age, and sex, resulting in 144 patients in the matched-pair set (72 patients per group). The primary endpoint was the change in least-squares means (ΔLSmeans) for the KOOS from baseline to the 24-month assessment.

Results

Defect sizes in the M-ACI group were significantly larger than in the MFx group (6.4 versus 3.7 cm2). Other differences included defect location (no patellar or tibial defects in the MFx group), number of defects (33.3% with 2 defects in the M-ACI group versus 9.7% in the MFx group), and defect cause (more patients with degenerative lesions in the M-ACI group). The M-ACI group had higher posttreatment KOOS (M-ACI versus MFX: 81.8 ± 16.8 versus 73.0 ± 20.6 points) and KOOS ΔLSmeans from baseline to 24 months posttreatment (M-ACI versus MFX: 36.9 versus 26.9 points). Treatment contrasts in KOOS ΔLSmeans from baseline indicated statistical significance in favor of M-ACI from 3 to 24 months posttreatment (P = .0026). Significant and clinically meaningful differences in favor of M-ACI at 24 months were also found regarding International Knee Documentation Committee (IKDC) score ΔLSmeans from baseline (37.8 versus 30.4 points; P = .0334), KOOS responder rates at 24 months (≥10-point improvement from baseline; 94.4% versus 65.3%; P < .0001), IKDC responder rates at 24 months (>20.5-point improvement from baseline; 83.3% versus 61.1%, P = .0126) and MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) score in a subgroup of patients (LS means, 86.9 versus 69.1; P = .0096).

Conclusion

In this exploratory analysis, M-ACI using an in situ crosslinked hydrogel demonstrated superior clinical and structural (MOCART) 24-month outcomes compared with MFx in patients with knee cartilage defects.

Scaffold-associated procedures are superior to microfracture in managing focal cartilage defects in the knee: A systematic review & meta-analysis

BACKGROUND

Debate continues as to whether surgical treatment with chondral-regeneration devices is superior to microfracture for focal articular cartilage defects in the knee.

PURPOSE

To evaluate the superiority of scaffold-associated chondral-regeneration procedures over microfracture by assessing: (1) Patient-reported outcomes; (2) Intervention failure; (3) Histological quality of cartilage repair.

STUDY DESIGN

A three-concept keyword search strategy was designed, in accordance with PRISMA guidelines: (i) knee (ii) microfracture (iii) scaffold. Four databases (Ovid Medline, Embase, CINAHL and Scopus) were searched for comparative clinical trials (Level I-III evidence). Critical appraisal used two Cochrane tools: the Risk of Bias tool (RoB2) for randomized control trials and the Risk of Bias in Non-randomized Studies-of Interventions (ROBINS-I). Study heterogeneity permitted qualitative analysis with the exception of three patient-reported scores, for which a meta-analysis was performed.

RESULTS

Twenty-one studies were identified (1699 patients, age range 18-66 years): ten randomized control trials and eleven non-randomized study interventions. Meta-analyses of the International Knee Documentation Committee (IKDC), Knee Injury And Osteoarthritis Outcome Score (KOOS) for pain and activities of daily living, and Lysholm score demonstrated statistically significant improvement in outcomes for scaffold procedures compared to microfracture at two years. No statistical difference was seen at five years.

CONCLUSION

Despite the limitations of study heterogeneity, scaffold-associated procedures appear to be superior to MF in terms of patient-reported outcomes at two years though similar at five years. Future evaluation would benefit from studies using validated clinical scoring systems, reporting failure, adverse events and long-term clinical follow up to determine technique safety and superiority.

Sex-dependent variation in cartilage adaptation: from degeneration to regeneration

Despite acknowledgement in the scientific community of sex-based differences in cartilage biology, the implications for study design remain unclear, with many studies continuing to arbitrarily assign demographics. Clinically, it has been well-established that males and females differ in cartilage degeneration, and accumulating evidence points to the importance of sex differences in the field of cartilage repair. However, a comprehensive review of the mechanisms behind this trend and the influence of sex on cartilage regeneration has not yet been presented. This paper aims to summarize current findings regarding sex-dependent variation in knee anatomy, sex hormones' effect on cartilage, and cartilaginous degeneration and regeneration, with a focus on stem cell therapies. Findings suggest that the stem cells themselves, as well as their surrounding microenvironment, contribute to sex-based differences. Accordingly, this paper underscores the contribution of both stem cell donor and recipient sex to sex-related differences in treatment efficacy. Cartilage regeneration is a field that needs more research to optimize strategies for better clinical results; taking sex into account could be a big factor in developing more effective and personalized treatments. The compilation of this information emphasizes the importance of investing further research in sex differences in cartilage biology.

Injectable autologous chondrocyte implantation in acetabular cartilage defects: 2-year minimum clinical and MRI results

INTRODUCTION

Early results using injectable autologous chondrocyte implantation (ACI) for the treatment of full thickness acetabular cartilage defects have been promising. However, so far there is no information on radiological results after injectable ACI using spheroids. The purpose of this sturdy was to (1) investigate the quality of tissue repair on MRI and (2) investigate the correlation between the MRI results and clinical results at a minimum follow-up of 24 months after third generation ACI in full thickness acetabular cartilage defects. It was hypothesized that ACI shows good MRI results in patients with large full thickness acetabular cartilage defects 24 months after surgery. It was also hypothesized that there is a correlation between postoperative clinical and MRI morphological results at a minimum follow-up of 24 months.

STUDY DESIGN

Retrospective case series.

MATERIALS AND METHODS

Patients with ACI for full thickness acetabular cartilage defects > 2 cm² were evaluated by preoperative and postoperative clinical scoring tools including the modified Harris Hip Score (mHHS), the International Hip Outcome Tool (iHOT-33), and the Subjective Hip Value (SHV) as well as a high resolution indirect arthro-MRI 24 months after surgery utilizing an identical imaging protocol for all patients. The magnetic resonance observation of cartilage repair tissue (MOCART) scoring system was used to classify the repair tissue on MRI. Demographic patient data was evaluated for influencing factors for pre- and postoperative clinical as well as radiological results.

RESULTS

Thirty six consecutive patients (5 women/31 men, average age 32.9 years) had undergone two stage ACI procedure. The average size of the cartilage defect was 5.0 (2-6) cm². The average follow-up was 29.9 (24-42) months. Four patients were not available for the final follow-up (follow-up rate 89%). The postoperative average MOCART score was 82.2 (± 14.2). MOCART score showed medium correlation of the item defect fill and the postoperative mHHS (r = 0.384, p = 0.043). There was no correlation of the other items or the total score with postoperative results. The patients showed significant improvement in the outcome measurements between preoperative and postoperative in the mHHS, the iHOT-33, and the SHV.

CONCLUSIONS

Despite the large acetabular cartilage defects included in this study, ACI showed good MRI results with complete defect fill in 87.5% after a minimum 24-month follow-up. Statistically significant correlation of MRI and clinical results could only be seen with the item defect fill. Further research with longer follow-up is needed to evaluate the long-term results of ACI in acetabular cartilage defects.

Practical Relevance of Institutional Guidelines in Translational Large Animal Studies of Cartilage Repair-A Multidisciplinary Survey

Background and Objective: Translational large animal models are inevitable to transfer cartilage repair methods into clinical practice. Guidelines for these trials have been published by guiding agencies (FDA, ASTM, EMEA) including recommendations for study descriptors and study outcomes. However, practical adherence to these recommendations is not achieved in all aspects. This study includes an assessment of the recommended aspects regarding practical relevance in large animal models for cartilage repair by professionals in the field. Materials and Methods: In an online based survey, 11 aspects regarding study design and 13 aspects regarding study outcome from previously published guidelines were evaluated (0-10 points, with 10 being most important) by study participants. Additionally, the survey contained questions related to professional experience (years), professional focus (preclinical, clinical, veterinarian, industry) and the preferred translational large animal model for cartilage repair. Results: The total number of survey participants was 37. Rated as most important for study design parameters was lesion size (9.54 pts., SD 0.80) followed by study duration (9.43 pts., SD 1.21); and method of scaffold fixation (9.08 pts., SD 1.30) as well as depth of the lesion (9.03 pts., SD 1.77). The most important aspects of study outcome were considered histology (9.41 pts., SD 0.86) and defect filling (8.97 pts., SD 1.21), while gene expression was judged as the least important (6.11 pts., SD 2.46) outcome. A total of 62.2% of all participants were researchers, 18.9% clinicians, 13.5% veterinarians and 5.4% industry employees. Conclusions: In translational research, recommendations published by guiding agencies receive broad theoretical consensus within the community, including both clinically and preclinically orientated scientists. However, implementation into practical research lacks in major aspects. Ongoing re-evaluation of the guidelines under involvement of all stakeholders and approaches to overcome financial and infrastructural limitations could support the acceptance of the guidance documents and contribute to standardization in the field.

Prognostic factors for the management of chondral defects of the knee and ankle joint: a systematic review

Purpose

Different surgical techniques to manage cartilage defects are available, including microfracture (MFx), autologous chondrocyte implantation (ACI), osteoarticular auto- or allograft transplantation (OAT), autologous matrix-induced chondrogenesis (AMIC). This study investigated the patient-related prognostic factors on the clinical outcomes of surgically treated knee and ankle cartilage defects.

Methods

This study followed the PRISMA statement. In May 2022, the following databases were accessed: PubMed, Google Scholar, Embase, and Scopus. All the studies investigating the outcomes of surgical management for knee and/or talus chondral defects were accessed. Only studies performing mesenchymal stem cells transplantation, OAT, MFx, ACI, and AMIC were considered. A multiple linear model regression analysis through the Pearson Product–Moment Correlation Coefficient was used.

Results

Data from 184 articles (8905 procedures) were retrieved. Female sex showed a positive moderate association with visual analogue scale at last follow-up (P = 0.02). Patient age had a negative association with the American Orthopaedic Foot and Ankle Score (P = 0.04) and Lysholm Knee Scoring Scale (P = 0.03). BMI was strongly associated with graft hypertrophy (P = 0.01). Greater values of VAS at baseline negatively correlate with lower values of Tegner Activity Scale at last follow-up (P < 0.0001).

Conclusion

The clinical outcomes were mostly related to the patients’ performance status prior surgery. A greater BMI was associated with greater rate of hypertrophy. Female sex and older age evidenced fair influence, while symptom duration prior to the surgical intervention and cartilage defect size evidenced no association with the surgical outcome. Lesion size and symptom duration did not evidence any association with the surgical outcome.

Utilization of Autologous Chondrocyte Implantation in the Knee is Increasing While Reoperation Rates Are Decreasing Despite Increasing Preoperative Comorbidities

PURPOSE

The primary purpose of this study was to assess the use of autologous chondrocyte implantation (ACI) procedures in the knee during last decade, and the secondary aims of the study were to determine reoperation rates after ACI and to identify associated risk factors.

METHODS

A retrospective cohort study from 2010-2020 was performed using the PearlDiver database. The database was queried for the Current Procedural Terminology (CPT) code for ACI performed in any knee location, including the patellofemoral and tibiofemoral joints. Reoperation was defined as interventional knee procedures or total knee arthroplasty after ACI. Reoperations were identified using CPT and International Classification of Diseases codes. Univariate and multivariate logistic regression were used to identify risk factors for reoperation. Significance was defined as P < .05.

RESULTS

Among the 2010 patients included in this study, there were 90-day and overall reoperation rates of 2.24% and 30.4%, respectively, with an average follow up of 4.8 ± 3.3 years. The most common reoperations included chondroplasty, meniscectomy, and microfracture. There was an increased rate of ACI performed from 2017-2019 (5.53/100,000) compared to 2014-2016 (4.16/100,000; P < .001). ACI surgeries performed in 2017-2019 were associated with decreased risk of reoperation within 2 years relative to 2014-2016 (odds ratio [OR] = 0.70; 95% confidence interval [CI], 0.52-0.94; P = .019). In the entire ACI cohort, older age (OR = 1.07; 95% CI, 1.05-1.09; P < .001) and tobacco use (OR = 2.13; 95% CI, 1.06-3.94; P = .022) were associated with increased risk of conversion to arthroplasty. Male sex was associated with decreased overall reoperation rates (OR = 0.73; 95% CI, 0.60-0.89; P = .002).

CONCLUSIONS

There has been increasing use of ACI in the knee with decreased risk of reoperation since 2017 and the introduction of matrix-associated autologous chondrocyte implantation. Older age and tobacco use were predictors of increased risk of conversion to arthroplasty. Male sex was associated with decreased risk of reoperation.

LEVEL OF EVIDENCE

Level IV, retrospective cohort design; database study.

Males and Females Exhibit Comparable Outcomes Following Treatment of Osteochondritis Dissecans Lesions of the Knee: A Systematic Review

PURPOSE

The purpose of this study was to evaluate the impact of patient sex on outcomes after treatment of osteochondritis dissecans (OCD) lesions of the knee through a systematic review of current evidence.

METHODS

This review was conducted according to the PRISMA guidelines using the PubMed, PubMed Central, Embase, Ovid Medline, Cochrane Libraries, and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases. Relevant outcomes included functional (e.g., International Knee Documentation Committee and Subjective Knee Evaluation, Lysholm Knee Score) and clinical outcomes (e.g., symptom/pain resolution, reoperation rates) for males and females after operative or nonoperative treatment of knee OCD lesions.

RESULTS

Ten articles with a total of 691 (73%) males and 260 (27%) females were included. Mean age ranged from 11.3 ± 2.1 years to 34.5 ± 10.3 years, and follow-up ranged from 6 months to 16.3 years. In four studies reporting functional outcomes, no significant differences were found between males and females in any metric assessed (all P > .05). Seven studies reported clinical outcomes after treatment of knee OCD lesions. One study determined males were more likely to have a successful nonoperative outcome than females (OR: 1.85, 95% CI: 1.00-3.40). Another study found males had a lower risk of developing symptomatic knee pain following operative or nonoperative treatment at a mean 14-year follow-up (HR: 0.24; 95% CI: 0.07-0.81). The remaining 5 studies reported statistically comparable clinical outcomes between males and females (all P > .05).

CONCLUSION

The present systematic review found mostly comparable clinical and functional outcomes between males and females following treatment of knee OCD lesions. Despite sex-related differences in the prevalence of these lesions and limited evidence of differences in clinical outcomes, these data suggest that sex does not independently predict outcomes after treatment.

LEVEL OF EVIDENCE

III, systematic review of Level II and III studies.

Sexual Dimorphism in the Extracellular and Pericellular Matrix of Articular Cartilage

OBJECTIVE

Women have a higher prevalence and burden of joint injuries and pathologies involving articular cartilage than men. Although knee injuries affecting young women are on the rise, most studies related to sexual dimorphism target postmenopausal women. We hypothesize that sexual dimorphism in cartilage structure and mechanics is present before menopause, which can contribute to sex disparities in cartilage pathologies.

DESIGN

Bovine knee was used as a model to study healthy adult cartilage. We compared elastic moduli under compression, abundances of extracellular and pericellular matrix (PCM) proteins using proteomics, and PCM constituency with tissue immunofluorescence. The gene expression of matrix-related genes under basal, anabolic, and catabolic conditions was assessed by quantitative polymerase chain reaction (qPCR).

RESULTS

The equilibrium modulus was higher in male cartilage compared with female cartilage. Proteoglycans were not associated with this biomechanical dimorphism. Proteomic and pathway analyses of tissue showed dimorphic enriched pathways in extracellular matrix (ECM)-related proteins in which male cartilage was enriched in matrix interconnectors and crosslinkers that strengthen the ECM network. Moreover, male and female tissue differed in enriched PCM components. Females had more abundance of collagen type VI and decorin, suggesting different PCM mechanics. Furthermore, the activation of regenerative and catabolic function in chondrocytes triggered sex-dependent signatures in gene expression, indicating dimorphic genetic regulation that is dependent on stimulation.

CONCLUSIONS

We provide evidence for sexual dimorphism in cartilage before menopause. Some differences are intrinsic to chondrocytes' gene expression defined by their XX versus XY chromosomal constituency.

Incidence, Timing, and Risk Factors for 5-Year Revision Surgery After Autologous Chondrocyte Implantation in 533 Patients

BACKGROUND

Autologous chondrocyte implantation (ACI) can be used to treat focal, full-thickness chondral defects of the knee. However, there is limited large-sample evidence available regarding the incidence, timing, and risk factors for revision surgery after ACI.

PURPOSE

To assess the 5-year incidence, timing, and risk factors for revision surgery after ACI in a large national cohort.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

The 2010-2020 PearlDiver database was queried for patients aged 20 to 59 years who underwent primary ACI of the knee without previous chondral procedures or knee arthroplasty. Revision surgery was defined as subsequent revision ACI, osteochondral allograft transplantation, osteochondral autograft transfer, unicompartmental knee arthroplasty, or total knee arthroplasty within 5 years. Kaplan-Meier analysis was used to assess both incidence and timing of revision surgery. Risk factors evaluated for revision surgery included patient age, sex, body mass index (BMI), Elixhauser Comorbidity Index (ECI) score, and previous or concomitant bony realignment procedures.

RESULTS

In total, 533 patients underwent primary ACI and met inclusion criteria. The 5-year incidence of revision surgery was 10.3%, with 63% of revisions occurring in the first 2 years after surgery. Risk factors associated with revision surgery included female sex (odds ratio, 2.58; 95% CI, 1.22-5.45; P = .013) and BMI ≥35 (odds ratio, 2.24; 95% CI, 1.01-4.94; P = .047). There was no relationship between age, ECI score, or previous or concomitant bony realignment procedures and revision surgery at 5 years (P > .05).

CONCLUSION

In an analysis of 533 patients who underwent ACI, 10.3% required a subsequent articular cartilage procedure or conversion to knee arthroplasty in the first 5 postoperative years. Revision surgery was greatest in the first 2 postoperative years. Female sex and severe obesity (BMI, ≥35) were associated with increased risk of revision surgery, while age, ECI score, and previous or concomitant bony realignment procedures were not. These findings suggest that treatment of chondral defects of the knee with ACI is associated with durable outcomes at the 5-year follow-up.

Chitosan based scaffold applied in patellar cartilage lesions showed positive clinical and MRI results at minimum 2 years of follow up

PURPOSE

New scaffold-based cartilage regeneration techniques have been developed to improve the results of microfractures also in complex locations like the patello-femoral joint. The aim of this study was to analyse the results obtained in patellar lesions treated with a bioscaffold,  a mixture composed by a chitosan solution, a buffer, and the patient's whole blood  which forms a stable clot into the lesion.

METHODS

Fifteen patients with ICRS grade 3-4 cartilage lesions of the patellar surface were treated with a chitosan bioscaffold. Fourteen patients were clinically and radiologically evaluated prospectively for a minimum follow-up of 2 years with IKDC, KOOS, Tegner score, and MRI. The mean age of patients at the time of surgery was 31.8 ± 11.9 and nine patients presented degenerative aetiology, four patients with previous trauma, and 1 patient with osteochondritis dissecans.  RESULTS: The IKDC subjective score improved from 46.2 ± 19.3 preoperatively to 69.5 ± 20.3 (p < 0.05) and 74.1 ± 23.2 (p < 0.05) at 12 and 24 months, respectively. Also KOOS Pain, KOOS Sport/Rec and KOOS QOL showed a significant improvement from baseline to 12 months and to the final follow-up. MRI evaluation showed a complete filling of the cartilage defect at the final follow-up in 70% of the lesions, obtaining a total MOCART 2.0 score of 71.5 ± 13.6 at 24 months after surgery.

CONCLUSION

Chondral patellar lesions represent a complex pathology, with lower results compared to other sites. This bioscaffold represents a safe surgical treatment providing a significant clinical improvement at 24 months in the treatment of patellar cartilage lesions.

LEVEL OF EVIDENCE

IV.

Global Variation in Studies of Articular Cartilage Procedures of the Knee: A Systematic Review

OBJECTIVE

The objective of this study was to determine whether there are significant differences in terms of indications, techniques, patient variables, and objective and subjective outcome scores as a function of the geographic locale of published studies of knee articular cartilage surgery.

METHODS

An electronic database search was performed of clinical studies evaluating knee articular cartilage procedures from 2000 to 2021. Studies were separated into global regions (Europe, Asia, North America, and South America) based on the study country. All cartilage-based treatments in each region were recorded. Patient age and sex, mechanism of injury, cartilage lesion size and location, follow-up time, failure rate, and knee outcome scores utilized were summarized and compared by region.

RESULTS

A total of 2,923 studies were analyzed. Eighty level 1 and 2 studies met the inclusion criteria. The majority were from Europe (n = 60), followed by Asia (n = 11), North America (n = 7), and South America (n = 2). The majority of procedures in European and North American studies were cell-based and marrow-stimulation procedures. In Asian studies, the most common procedures were marrow-stimulation, experimental, and biologic procedures as defined by the authors. Asian countries had a higher proportion of females (P < 0.001) and an overall older patient population (P < 0.001). Regional variation was also seen in terms of lesion location, mechanism of injury, and failure rate.

CONCLUSION

Most high-level evidence for articular cartilage-based procedures of the knee comes from European countries. These studies vary by patient age and sex, anatomic location, and mechanism of injury. Global variation should be taken into consideration when interpreting and applying studies of knee articular cartilage surgery.

Treatment of Large Cartilage Defects in the Knee by Hydrogel-Based Autologous Chondrocyte Implantation: Two-Year Results of a Prospective, Multicenter, Single-Arm Phase III Trial

OBJECTIVE

To evaluate the clinical outcome of a hydrogel-based autologous chondrocyte implantation (ACI) for large articular cartilage defects in the knee joint.

DESIGN

Prospective, multicenter, single-arm, phase III clinical trial. ACI was performed in 100 patients with focal full-thickness cartilage defects ranging from 4 to 12 cm² in size. The primary outcome measure was the responder rate at 2 years using the Knee Injury and Osteoarthritis Outcome Score (KOOS).

RESULTS

Two years after ACI treatment, 93% of patients were KOOS responders having improved by ≥10 points compared with their pre-operative level. The primary endpoint of the study was met and demonstrated that the KOOS response rate is markedly greater than 40% with a lower 95% CI (confidence interval) of 86.1, more than twice the pre-specified no-effect level. KOOS improvement (least squares mean) was 42.0 ± 1.8 points (95% CI between 38.4 and 45.7). Mean changes from baseline were significant in the overall KOOS and in all 5 KOOS subscores from Month 3 (first measurement) to Month 24 (inclusive) (P < 0.0001). The mean MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) score after 24 months reached 80.0 points (95% CI: 70.0-90.0 points) and 92.1 points in lesions ≤ 5 cm².

CONCLUSIONS

Overall, hydrogel-based ACI proved to be a valuable treatment option for patients with large cartilage defects in the knee as demonstrated by early, statistically significant, and clinically meaningful improvement up to 2 years follow-up. Parallel to the clinical improvements, MRI analyses suggested increasing maturation, re-organization, and integration of the repair tissue.

TRIAL REGISTRATION

NCT03319797; EudraCT No.: 2016-002817-22.

Timing of postoperative weightbearing in the treatment of traumatic chondral injuries of the knee in athletes - A systematic review of current concepts in clinical practice

BACKGROUND

Surgery aims to stimulate healing and enable a safe return to sport in athletes with symptomatic cartilage lesions of the knee. Timing of postoperative weightbearing is crucial, balancing a stimulation of the healing and avoiding reinjury.To explore current concepts of timing to partial and full weightbearing and rate of return to sport in athletes after articular cartilage surgery of the knee.Systematic Review of studies with level of evidence I-III.

METHODS

Four databases (Pubmed, Web of Science, Scopus and Embase) were searched using a predetermined keyword strategy. Two independent reviewers screened results according to inclusion and exclusion criteria. Modified Coleman Methodology Score (mCMS) was used for the quality assessment.

RESULTS

5294 records were found. Data from ten studies was extracted after duplicate removal, title and abstract screening and full-text evaluation. Eight of the ten studies included a detailed rehabilitation protocol, including 336 out of a total athletic population of 401. 62% began partial weightbearing (PWB) 1-2 weeks postoperatively, while 38% began within 3-4 weeks. The studies that had a later PWB all returned to full weightbearing (FWB) within 6-8 weeks. One study with early PWB returned to early FWB, while the other two returned 10-12 weeks postoperatively. "Return to Sport" (RTS) was the most common reported outcome measure, with most studies reporting RTS at 80% or higher.

CONCLUSION

There is no clear evidence that the timing of weightbearing (WB) affects the outcome and return to sport in athletes after surgery for focal full-thickness cartilage lesions of the knee. On the other hand, there seems to be no adverse effects in adopting an early WB strategy, currently defined differently by different authors. Further studies directly comparing the timing of WB for specific surgical procedures in athletes and with relevant control groups is recommended. There is a need for a consensus in regard to more exactly defining "early" vs "late" weightbearing in relation to a universal and precisely defined state of healing.

Cartilage Restoration of Patellofemoral Lesions: A Systematic Review

PURPOSE

This study aimed to systematically analyze the postoperative clinical, functional, and imaging outcomes, complications, reoperations, and failures following patellofemoral cartilage restoration surgery.

METHODS

This review was conducted according to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). PubMed, EMBASE, and Cochrane Library databases were searched up to August 31, 2018, to identify clinical studies that assessed surgical outcomes of patellofemoral cartilage restoration surgery. The Methodological Index for Non-Randomized Studies (MINORS) was used to assess study quality.

RESULTS

Forty-two studies were included comprising 1,311 knees (mean age of 33.7 years and 56% males) and 1,309 patellofemoral defects (891 patella, 254 trochlear, 95 bipolar, and 69 multiple defects, including the patella or trochlea) at a mean follow-up of 59.2 months. Restoration techniques included autologous chondrocyte implantation (56%), particulated juvenile allograft cartilage (12%), autologous matrix-induced chondrogenesis (9%), osteochondral autologous transplantation (9%), and osteochondral allograft transplantation (7%). Significant improvement in at least one score was present in almost all studies and these surpassed the minimal clinically important difference threshold. There was a weighted 19%, 35%, and 6% rate of reported complications, reoperations, and failures, respectively. Concomitant patellofemoral surgery (51% of patients) mostly did not lead to statistically different postoperative outcomes.

CONCLUSION

Numerous patellofemoral restoration techniques result in significant functional improvement with a low rate of failure. No definitive conclusions could be made to determine the best surgical technique since comparative studies on this topic are rare, and treatment choice should be made according to specific patient and defect characteristics.

LEVEL OF EVIDENCE

Level IV, systematic review of level II to IV studies.

Does Gender Influence Outcome in Cartilage Repair Surgery? An Analysis of 4,968 Consecutive Patients from the German Cartilage Registry (Knorpel Register DGOU)

The goal was to examine gender differences of patient characteristics and outcome after cartilage repair based on a collective of nearly 5,000 patients. Patient characteristics, accompanying therapies, and outcome (Knee Injury and Osteoarthritis Outcome Score [KOOS], reoperations, patient satisfaction) of 4,986 patients of the German cartilage register DGOU were assessed by t test for possible gender differences. P values <0.05 were considered statistically significant. Women were older than men (38.07 ± 12.54 vs. 26.94 ± 12.394 years, P = 0.002), more often preoperated (0.30 ± 0.63 vs. 0.24 ± 0.55, P = 0.001), and had a longer symptom duration (25.22 ± 41.20 vs. 20.67 ± 35.32 months, P < 0.001). Men had greater mean leg axis malalignment than women (3.24° ± 3.26° vs. 2.67° ± 3.06°, P < 0.001), less favorable meniscal status (P = 0.001), worse defect stage (P = 0.006), and a more severely damaged corresponding articular surface (P = 0.042). At baseline (59.84 ± 17.49 vs. 52.10 ± 17.77, P < 0.001), after 6 months (72.83 ± 15.56 vs. 66.56 ± 17.66, P < 0.001), after 12 months (77.88 ± 15.95 vs. 73.07 ± 18.12, P < 0.001), and after 24 months (79.311 ± 15.94 vs. 74.39 ± 18.81, P < 0.001), men had better absolute KOOS values, but women had better relative KOOS increases 6 months (14.59 ± 17.31 vs. 12.49 ± 16.3, P = 0.005) as well as 12 months postoperatively (20.27 ± 18.6 vs. 17.34 ± 17.79, P = 0.001) compared with preoperatively, although 12 and 24 months postoperatively they were subjectively less satisfied with the outcome (P < 0.001) and had a higher reintervention rate at 24 months (0.17 ± 0.38 vs. 0.12 ± 0.33, P = 0.008). In summary, the present work shows specific gender differences in terms of patient characteristics, defect etiology, defect localization, concomitant therapy, and the choice of cartilage repair procedure. Unexpectedly, contrary to the established scientific opinion, it could be demonstrated that women show relatively better postoperative KOOS increases, despite a higher revision rate and higher subjective dissatisfaction.

Typical MRI-pattern suggests peak maturation of the ACI graft 2 years after third-generation ACI: a systematic review

PURPOSE

The purpose of the present article was (1) to systematically review the current literature and (2) to collect data regarding the postoperative magnetic resonance imaging (MRI) appearance of third-generation autologous chondrocyte implantation (ACI) grafts and (3) to provide an overview of imaging findings at various postoperative time points.

METHODS

A systematic review of the literature in Medline (Pubmed) and Embase was performed using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Articles which reported the post-operative MRI morphological outcomes following the use of third-generation ACI for treatment of knee cartilage lesions were included. All MRI results were allocated to six different time intervals: ≤ 3 months, > 3-6 months, > 6 months-1 year, > 1 year-2 years, > 2-5 years and > 5 years after surgery.

RESULTS

A total of 22 studies were included and the study populations ranged from 13 to 180 patients adding up to a total of 951 patients. Parameters such as defect fill, border integration, surface contour, graft morphology and integrity of the subchondral lamina all improve gradually with a peak two years following surgery suggesting complete graft maturation at this time point. After this peak, a statistically insignificant decline is noted for most of the parameters. Signal intensity was found to gradually shift from hyperintense to isointense in the first 36 months and to hypointense later on. Contrarily, subchondral bone edema is not only a postoperative feature of the procedure but also can reappear or persist up to ten years after surgery. As graft failures can appear after two years, consequently, the MRI composite score is also affected.

CONCLUSION

Recurring patterns in postoperative MRI appearance were observed in certain parameters including defect filling, graft signal intensity and structure, border integration of the graft while parameters like subchondral bone tend to be unpredictable. Given the heterogenous findings in terms of clinical correlation, and relating that aspect to the patterns found in this review, an MRI is justified at three months, one year, two years and five years after surgery, unless the clinical symptomatology and individual patient needs dictate otherwise.

LEVEL OF EVIDENCE

IV.

Accurate Reporting of Concomitant Procedures Is Highly Variable in Studies Investigating Knee Cartilage Restoration

OBJECTIVE

Successful clinical outcomes following cartilage restoration procedures are highly dependent on addressing concomitant pathology. The purpose of this study was to document methods for evaluating concomitant procedures of the knee when performed with articular cartilage restoration techniques, and to review their reported findings in high-impact clinical orthopedic studies. We hypothesized that there are substantial inconsistencies in reporting clinical outcomes associated with concomitant procedures relative to outcomes related to isolated cartilage repair.

DESIGN

A total of 133 clinical studies on articular cartilage repair of the knee were identified from 6 high-impact orthopedic journals between 2011 and 2017. Studies were included if they were primary research articles reporting clinical outcomes data following surgical treatment of articular cartilage lesions with a minimum sample size of 5 patients. Studies were excluded if they were review articles, meta-analyses, and articles reporting only nonclinical outcomes (e.g., imaging, histology). A full-text review was then used to evaluate details regarding study methodology and reporting on the following variables: primary cartilage repair procedure, and the utilization of concomitant procedures to address additional patient comorbidities, including malalignment, meniscus pathology, and ligamentous instability. Each study was additionally reviewed to document variation in clinical outcomes reporting in patients that had these comorbidities addressed at the time of surgery.

RESULTS

All studies reported on the type of primary cartilage repair procedure, with autologous chondrocyte implantation (ACI) noted in 43% of studies, microfracture (MF) reported in 16.5%, osteochondral allograft (OCA) in 15%, and osteochondral autograft transplant (OAT) in 8.2%. Regarding concomitant pathology, anterior cruciate ligament (ACL) reconstruction (24.8%) and meniscus repair (23.3%) were the most commonly addressed patient comorbidities. A total of 56 studies (42.1%) excluded patients with malalignment, meniscus injury, and ligamentous instability. For studies that addressed concomitant pathology, 72.7% reported clinical outcomes separately from the cohort treated with only cartilage repair. A total of 16.5% of studies neither excluded nor addressed concomitant pathologies. There was a significant amount of variation in the patient reported outcome scores used among the studies, with the majority of studies reporting International Knee Documentation Committee (IKDC) and Knee Injury and Osteoarthritis Outcomes Score (KOOS) in 47.2% and 43.6% of articles, respectively.

CONCLUSIONS

In this study on knee cartilage restoration, recognition and management of concomitant pathology is inadequately reported in approximately 28% of studies. Only 30% of articles reported adequate treatment of concomitant ailments while scoring their outcomes using one of a potential 18 different scoring systems. These findings highlight the need for more standardized methods to be applied in future research with regard to inclusion, exclusion, and scoring concomitant pathologies with regard to treatment of cartilage defects in the knee.

Autologous Matrix-Induced Chondrogenesis for Treatment of Focal Cartilage Defects in the Knee: A Follow-up Study

Background:

Autologous matrix-induced chondrogenesis (AMIC) is a well-established treatment for full-thickness cartilage defects.

Purpose:

To evaluate the long-term clinical outcomes of AMIC for the treatment of chondral lesions of the knee.

Study Design:

Case series; Level of evidence, 4.

Methods:

A multisite prospective registry recorded demographic data and outcomes for patients who underwent repair of chondral defects. In total, 131 patients were included in the study. Lysholm, Knee injury and Osteoarthritis Outcome Score (KOOS), and visual analog scale (VAS) score for pain were used for outcome analysis. Across all patients, the mean ± SD age of patients was 36.6 ± 11.7 years. The mean body weight was 80.0 ± 16.8 kg, mean height was 176.3 ± 7.9 cm, and mean defect size was 3.3 ± 1.8 cm². Defects were classified as Outerbridge grade III or IV. A repeated-measures analysis of variance was used to compare outcomes across all time points.

Results:

The median follow-up time for the patients in this cohort was 4.56 ± 2.92 years. Significant improvement (P < .001) in all scores was observed at 1 to 2 years after AMIC, and improved values were noted up to 7 years postoperatively. Among all patients, the mean preoperative Lysholm score was 46.9 ± 19.6. At the 1-year follow-up, a significantly higher mean Lysholm score was noted, with maintenance of the favorable outcomes at 7-year follow-up. The KOOS also showed a significant improvement of postoperative values compared with preoperative data. The mean VAS had significantly decreased during the 7-year follow-up. Age, sex, and defect size did not have a significant effect on the outcomes.

Conclusion:

AMIC is an effective method of treating chondral defects of the knee and leads to reliably favorable results up to 7 years postoperatively.

Wide Variation in Methodology in Level I and II Studies on Cartilage Repair: A Systematic Review of Available Clinical Trials Comparing Patient Demographics, Treatment Means, and Outcomes Reporting

BACKGROUND

The management of complex cartilage pathology in young, otherwise healthy patients can be difficult.

PURPOSE

To determine the nature of the design, endpoints chosen, and rate at which the endpoints were met in published studies and ongoing clinical trials that investigate cartilage repair and restoration procedures.

STUDY DESIGN

Systematic review.

METHODS

A systematic review of the publicly available level I/II literature and of the publicly listed clinical trials regarding cartilage repair and restoration procedures for the knee was conducted adhering to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Seventeen published studies and 52 clinical trials were included. Within the 17 published studies, the most common procedure studied was microfracture (MFX) + augmentation (N = 5; 29.4%) and the most common comparison/control group was MFX (N = 10; 58.8%). In total, 13 different cartilage procedure groups were evaluated. For published studies, the most common patient-reported outcome (PRO) measures assessed is the Knee Injury and Osteoarthritis Outcome Score (KOOS) and Visual Analog Scale-Pain (VAS) (N = 10 studies, 58.8% each, respectively). Overall, there are 10 different PROs used among the included studies. Ten studies demonstrate superiority, 5 demonstrate noninferiority, and 2 demonstrate inferiority to the comparison or control groups. For the clinical trials included, the most common procedure studied is MFX + augmentation (N = 16; 30.8%). The most common PRO assessed is KOOS (N = 36 trials; 69.2%), and overall there are 24 different PROs used among the included studies.

CONCLUSIONS

Recently published studies and clinical trials evaluate a variety of cartilage repair and restoration strategies for the knee, most commonly MFX + augmentation, at various time points of outcome evaluation, with KOOS and VAS scores being used most commonly. MFX remains the most common comparison group for these therapeutic investigations. Most studies demonstrate superiority versus comparison or control groups. Understanding the nature of published and ongoing clinical trials will be helpful in the investigation of emerging technologies required to navigate the regulatory process while studying a relatively narrow population of patients.

Patellofemoral Cartilage Restoration: A Systematic Review and Meta-analysis of Clinical Outcomes

BACKGROUND

Many surgical options for treating patellofemoral (PF) cartilage lesions are available but with limited evidence comparing their results.

PURPOSE

To determine and compare outcomes of PF cartilage restoration techniques.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

PRISMA (Preferred Reporting Items for Systematic Meta-Analyses) guidelines were followed by utilizing the PubMed, EMBASE, and Cochrane Library databases. Inclusion criteria were clinical studies in the English language, patient-reported outcomes after PF cartilage restoration surgery, and >12 months' follow-up. Quality assessment was performed with the Coleman Methodology Score. Techniques were grouped as osteochondral allograft transplantation (OCA), osteochondral autograft transfer (OAT), chondrocyte cell-based therapy, bone marrow-based therapy, and scaffolds.

RESULTS

A total of 59 articles were included. The mean Coleman Methodology Score was 71.8. There were 1937 lesions (1077 patellar, 390 trochlear, and 172 bipolar; 298 unspecified). The frequency of the procedures was as follows, in descending order: chondrocyte cell-based therapy (65.7%), bone marrow-based therapy (17.2%), OAT (8%), OCA (6.6%), and scaffolds (2.2%). When compared with the overall pooled lesion size (3.9 cm²; 95% CI, 3.5-4.3 cm²), scaffold (2.2 cm²; 95% CI, 1.8-2.5 cm²) and OAT (1.5 cm²; 95% CI, 1.1-1.9 cm²) lesions were smaller (P < .001), while chondrocyte cell-based therapy lesions were larger (4.7 cm²; 95% CI, 4.1-5.3 cm²; P = .039). Overall, the instability pool was 11.9%, and the anatomic risk factors pool was 32.1%. Statistically significant improvement was observed on at least 1 patient-reported outcome in chondrocyte cell-based therapy (83%), OAT (78%), OCA (71%), bone marrow-based therapy (64%), and scaffolds (50%). There were no significant differences between any group and the overall pooled change in International Knee Documentation Committee score (30.2; 95% CI, 27.4-32.9) and Lysholm score (25.2; 95% CI, 16.9-33.5). There were no significant differences between any group and the overall pooled rate in minor complication rate (7.6%; 95% CI, 4.7%-11.9%) and major complication rate (8.3%; 95% CI, 5.7%-12.0%); however, OCA had a significantly greater failure rate (22.7%; 95% CI, 14.6%-33.4%) as compared with the overall rate (6.8%; 95% CI, 4.7%-9.5%).

CONCLUSION

PF cartilage restoration leads to improved clinical outcomes, with low rates of minor and major complications. There was no difference among techniques; however, failures were higher with OCA.

An Expert Consensus Statement on the Management of Large Chondral and Osteochondral Defects in the Patellofemoral Joint

Background

Cartilage lesions of the patellofemoral joint constitute a frequent abnormality. Patellofemoral conditions are challenging to treat because of complex biomechanics and morphology.

Purpose

To develop a consensus statement on the functional anatomy, indications, donor graft considerations, surgical treatment, and rehabilitation for the management of large chondral and osteochondral defects in the patellofemoral joint using a modified Delphi technique.

Study Design

Consensus statement.

Methods

A working group of 4 persons generated a list of statements related to the functional anatomy, indications, donor graft considerations, surgical treatment, and rehabilitation for the management of large chondral and osteochondral defects in the patellofemoral joint to form the basis of an initial survey for rating by a group of experts. The Metrics of Osteochondral Allografts (MOCA) expert group (composed of 28 high-volume cartilage experts) was surveyed on 3 occasions to establish a consensus on the statements. In addition to assessing agreement for each included statement, experts were invited to propose additional statements for inclusion or to suggest modifications of existing statements with each round. Predefined criteria were used to refine statement lists after each survey round. Statements reaching a consensus in round 3 were included within the final consensus document.

Results

A total of 28 experts (100% response rate) completed 3 rounds of surveys. After 3 rounds, 36 statements achieved a consensus, with over 75% agreement and less than 20% disagreement. A consensus was reached in 100.00% of the statements relating to functional anatomy of the patellofemoral joint, 88.24% relating to surgical indications, 100.00% relating to surgical technical aspects, and 100.00% relating to rehabilitation, with an overall consensus of 95.5%.

Conclusion

This study established a strong expert consensus document relating to the functional anatomy, surgical indications, donor graft considerations for osteochondral allografts, surgical technical aspects, and rehabilitation concepts for the management of large chondral and osteochondral defects in the patellofemoral joint. Further research is required to clinically validate the established consensus statements and better understand the precise indications for surgery as well as which techniques and graft processing/preparation methods should be used based on patient- and lesion-specific factors.

Third-generation autologous chondrocyte implantation after failed bone marrow stimulation leads to inferior clinical results

PURPOSE

Third-generation autologous chondrocyte implantation (ACI) is an established and frequently used method and successful method for the treatment of full-thickness cartilage defects in the knee. There are also an increasing number of patients with autologous chondrocyte implantation as a second-line therapy that is used after failed bone marrow stimulation in the patient's history. The purpose of this study is to investigate the effect of previous bone marrow stimulation on subsequent autologous chondrocyte implantation therapy. In this study, the clinical results after the matrix-based autologous chondrocyte implantation in the knee in a follow-up over 3 years postoperatively were analysed.

METHODS

Forty patients were included in this study. A total of 20 patients with cartilage defects of the knee were treated with third-generation autologous chondrocyte implantation (Novocart® 3D) as first-line therapy. The mean defect size was 5.4 cm² (SD 2.6). IKDC subjective score and VAS were used for clinical evaluation after 6, 12, 24 and 36 months postoperatively. The results of these patients were compared with 20 matched patients with autologous chondrocyte implantation as second-line therapy. Matched pair analysis was performed by numbers of treated defects, defect location, defect size, gender, age and BMI.

RESULTS

Both the first-line (Group I) and second-line group (Group II) showed significantly better clinical results in IKDC score and VAS score in the follow-up over 3 years compared with the preoperative findings. In addition, Group I showed significantly better results in the IKDC and VAS during the whole postoperative follow-up after 6, 12, 24 and 36 months compared to Group II with second-line autologous chondrocyte implantation (IKDC 6 months p = 0.015, 1 year p = 0.001, 2 years p = 0.001, 3 years p = 0.011). Additionally, we found a lower failure rate in Group I. No revision surgery was performed in Group I. The failure rate in the second-line Group II was 30%.

CONCLUSION

This study showed that third-generation autologous chondrocyte implantation is a suitable method for the treatment of full-thickness cartilage defects. Both, Group I and Group II showed significant improvement in our follow-up. However, in comparing the results of the two groups, autologous chondrocyte implantation after failed bone marrow stimulation leads to worse clinical results.

LEVEL OF EVIDENCE

III.

Comparative Effectiveness of Cartilage Repair With Respect to the Minimal Clinically Important Difference

BACKGROUND

Recent studies demonstrated a 5% increase in cartilage repair procedures annually in the United States. There is currently no consensus regarding a superior technique, nor has there been a comprehensive evaluation of postoperative clinical outcomes with respect to a minimal clinically important difference (MCID).

PURPOSE

To determine the proportion of available cartilage repair studies that meet or exceed MCID values for clinical outcomes improvement over short-, mid-, and long-term follow-up.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

A systematic review was performed via the Medline, Scopus, and Cochrane Library databases. Available studies were included that investigated clinical outcomes for microfracture (MFX), osteoarticular transfer system (OATS), osteochondral allograft transplantation, and autologous chondrocyte implantation/matrix-induced autologous chondrocyte implantation (ACI/MACI) for the treatment of symptomatic knee chondral defects. Cohorts were combined on the basis of surgical intervention by performing a meta-analysis that utilized inverse-variance weighting in a DerSimonian-Laird random effects model. Weighted mean improvements in International Knee Documentation Committee (IKDC), Lysholm, and visual analog scale for pain (VAS pain) scores were calculated from preoperative to short- (1-4 years), mid- (5-9 years), and long-term (≥10 years) postoperative follow-up. Mean values were compared with established MCID values per 2-tailed 1-sample Student t tests.

RESULTS

A total of 89 studies with 3894 unique patients were analyzed after full-text review. MFX met MCID values for all outcome scores at short- and midterm follow-up with the exception of VAS pain in the midterm. OATS met MCID values for all outcome scores at all available time points; however, long-term data were not available for VAS pain. Osteochondral allograft transplantation met MCID values for IKDC at short- and midterm follow-up and for Lysholm at short-term follow-up, although data were not available for other time points or for VAS pain. ACI/MACI met MCID values for all outcome scores (IKDC, Lysholm, and VAS pain) at all time points.

CONCLUSION

In the age of informed consent, it is important to critically evaluate the clinical outcomes and durability of cartilage surgery with respect to well-established standards of clinical improvement. MFX failed to maintain VAS pain improvements above MCID thresholds with follow-up from 5 to 9 years. All cartilage repair procedures met MCID values at short- and midterm follow-up for IKDC and Lysholm scores; ACI/MACI and OATS additionally met MCID values in the long term, demonstrating extended maintenance of clinical benefits for patients undergoing these surgical interventions as compared with MFX.

Equivalent 10-Year Outcomes After Implantation of Autologous Bone Marrow-Derived Mesenchymal Stem Cells Versus Autologous Chondrocyte Implantation for Chondral Defects of the Knee

BACKGROUND

The use of bone marrow-derived mesenchymal stem cells (BMSCs) in cartilage repair procedures circumvents some of the limitations of autologous chondrocyte implantation (ACI), but long-term outcomes for this newer procedure are lacking. The authors previously reported comparable outcomes for the 2 procedures at 2-year follow-up.

PURPOSE/HYPOTHESIS

The purpose was to compare the long-term clinical outcomes of ACI versus BMSCs. It was hypothesized that there would be no significant difference between the groups in terms of patient-reported outcome scores and safety outcomes at 10-year follow-up.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Seventy-two patients who underwent either ACI or BMSC implantation-matched in terms of age and lesion site- were followed up to a median of at least 10 years. Patients were assessed with the 36-item Short Form Health Survey (SF-36), the International Knee Documentation Committee knee evaluation form, the Lysholm Knee Score, and the Tegner Activity Scale. In addition, information was obtained regarding any additional surgical procedures as well as safety data, with particular attention to infection and tumor formation.

RESULTS

There was an improvement in all patient-reported outcomes scores apart from the Mental Component Summary of the SF-36 after cartilage repair surgery. There was no significant difference in any of the patient-reported outcomes between cohorts at any time point. Six and 5 patients in the ACI and BMSC groups, respectively, underwent subsequent surgical procedures, including 1 total knee replacement in the BMSC group. None of the patients in either group developed any deep infection or tumor within the follow-up period.

CONCLUSION

BMSC implantation used for the treatment of chondral defects of the knee appears to result in equivalent clinical outcomes to first-generation ACI at up to 10 years, with no apparent increased tumor formation risk.

Analysis of Defect Size and Ratio to Condylar Size With Respect to Outcomes After Isolated Osteochondral Allograft Transplantation

BACKGROUND

Osteochondral allograft transplantation (OCA) is a successful knee joint preservation technique; however, the effects of defect size and defect size:condyle ratio (DSCR) are poorly understood.

PURPOSE

To quantify clinical outcomes of isolated OCA of the knee based on defect size and DSCR.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Data from patients who underwent OCA of the knee without major concomitant procedures by a single surgeon were analyzed at a minimum follow-up of 2 years. Osteochondral defect size was measured intraoperatively, and femoral condyle size was measured with preoperative imaging. Patient-reported outcomes, reoperations, and survival rates were analyzed per defect size and DSCR, comparing males and females and patients <40 and ≥40 years old.

RESULTS

Sixty-eight patients were included, of whom 57% were male (mean ± SD: age, 34.5 ± 10.3 years; follow-up, 5.2 ± 2.6 years). Mean osteochondral defect size and DSCR were 3.48 ± 1.72 cm² and 0.2 ± 0.1, respectively. Defect size was larger among males as compared with females (3.97 ± 1.71 cm² vs 2.81 ± 1.16 cm², P = .005), while DSCRs were not significantly different between sexes ( P = .609). The cohort as a whole demonstrated improvements in the following scores: Lysholm, International Knee Documentation Committee, Knee injury and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, and 12-Item Short Form Health Survey Physical ( P < .05). There were 27 reoperations (39.7%) at a mean of 2.5 ± 1.92 years and 8 failures (11.8%) at a mean of 2.62 ± 1.3 years. Mean DCSR was higher among patients with graft failure (0.26 ± 0.20 vs 0.19 ± 0.07, P = .049). After stratification by age, failures among patients ≥40 years old were associated with a larger defect size (mean 5.37 ± 3.50 cm² vs 3.22 ± 1.32 cm², P = .03) and higher DSCR (mean 0.30 ± 0.25 vs 0.19 ± 0.06, P = .05) when compared with nonfailures. Failures among patients <40 years old were not significantly associated with defect size or DSCR ( P > .05) as compared with nonfailures.

CONCLUSION

Patients undergoing isolated OCA transplantation demonstrated significant clinical improvements and a graft survival of 88.2% at 5.2 years. Failures overall were associated with a larger DSCR, and failures among patients ≥40 years old with a larger DSCR and larger defect size. Increasing defect size among males was positively correlated with some improved outcomes, although this was not maintained in analysis of the DSCR, suggesting similar prognosis after OCA regardless of sex.

CLINICAL RELEVANCE

Failed osteochondral allografts are associated with larger defect sizes and defect:condyle ratios in this study, providing additional information to surgeons for appropriate patient consultation.

Changing trends in the use of cartilage restoration techniques for the patellofemoral joint: a systematic review

PURPOSE

The patellofemoral (PF) joint contains the thickest articular cartilage in the human body. Chondral lesions to this area are often misdiagnosed and can predispose to secondary osteoarthritis if left untreated. Treatment options range from arthroscopic debridement to cartilage restoration techniques such as microfracture (MFx), autologous chondrocyte implantation (ACI), and osteochondral autograft transplantation. The purpose of this study was to systematically assess the trends in surgical techniques, outcomes, and complications of cartilage restoration of the PF joint.

METHODS

This review has been conducted according to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). The electronic databases PubMed, MEDLINE, and EMBASE were searched from January 1, 2007 to April 30, 2018. The Methodological Index for Non-randomized Studies (MINORS) was used to assess study quality. A two-proportion z test was used to determine whether the differences between the proportions of cartilage restoration techniques used from 2007 to 2012 and 2013-2018 were statistically significant.

RESULTS

Overall, 28 studies were identified, including 708 patients (824 knees) with a mean age of 39.5 ± 10.5 years and a mean follow-up of 39.1 ± 16.0 months. Majority of patients were treated with ACI (45.5%) and MFx (29.6%). A significant increase in the use of the third generation ACI occurred with a simultaneous decreased usage of the conventional MFx over the last 5 years (p < 0.001). All techniques had significant (p < 0.05) improvements in clinical outcomes. The overall complication rate was 9.2%, of which graft hypertrophy (2.7%) was the most prevalent.

CONCLUSIONS

ACI was the most common restoration technique. The use of third generation ACI has increased with a concurrent decline in the use of conventional MFx over the latter half of the past decade (p < 0.001). Overall, the various cartilage restoration techniques reported improvements in patient reported outcomes with low complication rates. Definitive conclusions on the optimal treatment remain elusive due to a lack of high-quality comparative studies.

LEVEL OF EVIDENCE

Level IV, Systematic Review of Level-II-IV studies.

Autologous Chondrocyte Implantation and Tibial Tubercle Osteotomy for Patellofemoral Chondral Defects: Improved Pain Relief and Occupational Outcomes Among US Army Servicemembers

BACKGROUND

The occupational and functional results of patellofemoral autologous chondrocyte implantation (ACI) are underreported. This investigation sought to establish clinical outcomes and rates for return to work in a predominantly high-demand military cohort undergoing this procedure.

PURPOSE

To determine the return-to-work, pain relief, and perioperative complication rates in a high-demand athletic cohort undergoing patellofemoral ACI.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

All military servicemembers from 2 military medical centers undergoing ACI for high-grade patellofemoral chondral defects between 2006 and 2014 were identified, and data were abstracted from their medical records and clinical databases. Demographic and surgical variables were obtained for patients with at least 2 years of postoperative follow-up, and perioperative complications, rates of return to work, and survivorship from revision were quantified.

RESULTS

Seventy-two patients (72%) had >2-year follow-up and had patellofemoral ACI for high-grade chondral defects, with 66 knees (91%) undergoing a concomitant offloading tibial tubercle osteotomy. Mean follow-up was 4.3 years (range, 2.0-9.9 years). The mean ± SD age was 34.4 ± 6.1 years; 86% were male; and 57% were involved in military occupational specialties of heavy or very heavy demand. Second-generation patellofemoral ACI with a type I/III collagen membrane was used for 85% of knees. Most defects were isolated to the patella (n = 40, 55%). The mean total defect surface area was 4.5 ± 2.9 cm² (range, 2.7-13.5 cm²). Fifty-six servicemembers (78%) returned to their occupational specialties. Three patients (4.1%) were classified as having surgical failures, requiring subsequent knee arthroplasty (n = 2) or a revision chondral procedure (n = 1). Mean visual analog scores improved significantly from 6.5 ± 1.5 to 3.2 ± 2.1 ( P < .0001). Multivariate analysis identified use of a periosteal patch as the only significant independent predictor for surgical ( P = .013) and overall ( P = .033) failures. Age <30 years ( P = .019), female sex ( P = .019), and regular tobacco use ( P = .011) were independent predictors of overall failure.

CONCLUSION

For patellofemoral chondral defects without a failed primary procedure, second-generation ACI successfully returned to work 78% of patients of moderate to very heavy occupational demand with significantly decreased patient-reported knee pain. Risk factors after ACI for patellofemoral articular lesions for overall failure were age <30 years, female sex, and tobacco use, while surgical and overall failures were associated with periosteal patch use.

Revision Surgery After Cartilage Repair: Data From the German Cartilage Registry (KnorpelRegister DGOU)

Background:

Various operative strategies have been introduced to restore the integrity of articular cartilage when injured. The frequency of revision surgery after cartilage regenerative surgery remains incompletely understood.

Purpose/Hypothesis:

The purpose of this study was to identify the reasons for revision surgery after cartilage regenerative surgery of the knee. We hypothesized that in a large patient cohort, revision rates would differ from those in the current literature.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

A total of 2659 complete data sets from the German Cartilage Registry were available for analyses. In brief, baseline data were provided by the attending physician at the time of index surgery. Follow-up data were collected using a web-based questionnaire inquiring whether patients had needed revision surgery during follow-up, which was defined as the endpoint of the present analysis.

Results:

A total of 88 patients (3.3%) reported the need for revision surgery as early as 12 months postoperatively. Among the most common causes were arthrofibrosis (n = 27) and infection (n = 10). Female patients showed a significantly greater complication rate (4.5%) when compared with male patients (2.6%; P = .0071). The majority of cartilage lesions were located at the medial femoral condyle (40.2%), with a mean defect size of 3.5 ± 2.1 cm². Neither the location nor defect size appeared to lead to an increased revision rate, which was greatest after osteochondral autografts (5.2%) and autologous chondrocyte implantation (4.6%). Revision rates did not differ significantly among surgical techniques. Chi-square analysis revealed significant correlations between the number of previous joint surgeries and the need for revision surgery (P = .0203). Multivariate regression analysis further confirmed sex and the number of previous surgeries as variables predicting the need for early revision surgery.

Conclusion:

The low early revision rates found in this study underline that today’s cartilage repair surgeries are mostly safe. Although invasiveness and techniques differ greatly among the procedures, no differences in revision rates were observed. Specific factors such as sex and the number of previous surgeries seem to influence overall revision rates and were identified as relevant risk factors with regard to patient safety.

Treatment of Knee Osteochondritis Dissecans With a Cell-Free Biomimetic Osteochondral Scaffold: Clinical and Imaging Findings at Midterm Follow-up

BACKGROUND

Osteochondritis dissecans (OCD) is a developmental condition of subchondral bone that may result in secondary separation and instability of the overlying articular cartilage, which in turn may lead to degeneration of the overall joint and early osteoarthritis. Biphasic scaffolds have been developed to address defects of the entire osteochondral unit by reproducing the different biological and functional requirements and guiding the growth of both bone and cartilage.

PURPOSE

To evaluate midterm clinical and imaging results after cell-free osteochondral scaffold implantation for the treatment of knee OCD.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Twenty-seven patients (8 women, 19 men; mean age, 25.5 ± 7.7 years) were treated for knee OCD, with International Cartilage Repair Society (ICRS) grade 3 to 4 lesions with a mean size of 3.4 ± 2.2 cm² (range, 1.5-12 cm²), and prospectively evaluated for up to 5 years using the ICRS classification system and the Tegner score. Eighteen patients underwent magnetic resonance imaging (MRI) at 24 and 60 months of follow-up, and the graft was evaluated using the magnetic resonance observation of cartilage repair tissue (MOCART) score for the cartilage layer, while a specific score was used for subchondral bone.

RESULTS

All patients significantly improved their clinical scores at each follow-up until their final evaluation. The mean International Knee Documentation Committee (IKDC) subjective score improved from 48.4 ± 17.8 to 82.2 ± 12.2 at 2 years ( P < .0005), and it then remained stable for up to 5 years postoperatively (90.1 ± 12.0). The mean Tegner score increased from 2.4 ± 1.7 preoperatively to 4.4 ± 1.6 at 2 years ( P = .001), with a further increase up to 5.0 ± 1.7 at 5 years of follow-up ( P < .0005 vs preoperatively), reaching almost the preinjury level (5.7 ± 2.2). The MOCART score showed stable results between 24 and 60 months, whereas the subchondral bone status significantly improved over time. No correlation was found between MRI findings and clinical outcomes.

CONCLUSION

This 1-step cell-free scaffold implantation procedure showed good and stable results for up to 60 months of follow-up for the treatment of knee OCD. MRI showed abnormalities, in particular at the subchondral bone level, but there was an overall improvement of features over time. No correlation was found between imaging and clinical findings.

Do Outcomes of Osteochondral Allograft Transplantation Differ Based on Age and Sex? A Comparative Matched Group Analysis

BACKGROUND

The effect of patient age or sex on outcomes after osteochondral allograft transplantation (OCA) has not been assessed.

PURPOSE

To determine clinical outcomes for male and female patients aged ≥40 years undergoing OCA compared with a group of patients aged <40 years.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A review of prospectively collected data of consecutive patients who underwent OCA by a single surgeon with a minimum follow-up of 2 years was conducted. The reoperation rate, failure rate, and patient-reported outcome scores were reviewed. All outcomes were compared between patients aged <40 or ≥40 years, with subgroup analyses conducted based on patient sex. Failure was defined as revision OCA, conversion to knee arthroplasty, or gross appearance of graft failure at second-look arthroscopic surgery. Descriptive statistics, Fisher exact or chi-square testing, and Mann-Whitney U testing were performed, with P < .05 set as significant.

RESULTS

A total of 170 patients (of 212 eligible patients; 80.2% follow-up) who underwent OCA with a mean follow-up of 5.0 ± 2.7 years (range, 2.0-15.1 years) were included, with 115 patients aged <40 years (mean age, 27.6 ± 7.3 years; 58 male, 57 female) and 55 patients aged ≥40 years (mean age, 44.9 ± 4.0 years; 33 male, 22 female). There were no differences in the number of pre-OCA procedures between the groups ( P = .085). There were no differences in the reoperation rate (<40 years: 38%; ≥40 years: 36%; P = .867), time to reoperation (<40 years: 2.12 ± 1.90 years; ≥40 years: 3.43 ± 3.43 years; P = .126), or failure rate (<40 years: 13%; ≥40 years: 16%; P = .639) between the older and younger groups. Patients in both groups demonstrated significant improvement in Lysholm (both: P < .001), International Knee Documentation Committee (IKDC) (both: P < .001), Knee Injury and Osteoarthritis Outcome Score (KOOS) (both: P < .001), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) (both: P < .001), and Short Form-12 (SF-12) physical (both: P < .001) scores compared with preoperative values. Patients aged ≥40 years demonstrated significantly higher KOOS symptom ( P = .015) subscores compared with patients aged <40 years. There were no significant differences in the number of complications, outcome scores, or time to failure between the sexes. In patients aged <40 years, female patients experienced failure significantly more quickly than male patients ( P = .039). In contrast, in patients aged ≥40 years, male patients experienced failure significantly more quickly than female patients ( P = .046).

CONCLUSION

This study provides evidence that OCA is a safe and reliable treatment option for osteochondral defects in patients aged ≥40 years. Male and female patients had similar outcomes. Patients aged <40 years demonstrated lower KOOS symptom subscores postoperatively compared with older patients, potentially attributable to higher expectations of return to function postoperatively as compared with older patients.

Matrix Production Affects MRI Outcomes After Matrix-Associated Autologous Chondrocyte Transplantation in the Knee

BACKGROUND

Matrix-associated autologous chondrocyte transplantation (MACT) has been an effective therapy for large, full-thickness cartilage lesions for years. However, little is known about how graft maturation is affected by characteristics of transplanted chondrocytes.

PURPOSE

To investigate the influence of gene expression of chondrocytes at the time of transplantation on MRI outcomes up to 2 years after MACT.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This study included 25 patients with 27 symptomatic traumatic defects of articular cartilage, who had undergone MACT in the knee. Postoperative MRI examinations were conducted at 3, 6, 12, and 24 months after surgery. Biochemical graft maturation was assessed by measuring T2 relaxation time values of the transplant and healthy native cartilage areas. The MOCART (magnetic resonance observation of cartilage repair tissue) score was used to evaluate the morphological quality of regeneration tissue. Gene expression (collagen type I, collagen type II, aggrecan, versican, and interleukin-1β) was determined by real-time polymerase chain reaction (PCR) in transplant residuals at the time point of transplantation and was correlated with MRI outcomes using Spearman's rank correlation coefficient. A Friedman test with post hoc analysis (Wilcoxon signed rank test) conducted with a Bonferroni correction was applied to compare scores at different time points.

RESULTS

T2 relaxation time of regeneration tissue improved from a mean ± SD of 74.6 ± 20.1 milliseconds at 3 months to 47.9 ±13.3 milliseconds at 24 months ( P < .003). These values were similar to the T2 relaxation times of the native surrounding cartilage (50.9 ± 15 ms). The calculated T2 index (ratio of regeneration tissue to native cartilage) improved from 1.63 ± 0.76 at 3 months to 1.0 ± 0.4 at 24 months ( P < .011). The MOCART score increased from 51.6 ± 15 points to 72.4 ± 12.2 points ( P < .001). Improvement of the T2 index over time significantly correlated with aggrecan, COL1A1, COL2A1, and versican expression ( r_s = 0.9, P < .001; r_s = 0.674, P < .012; r_s = 0.553, P < .05; and r_s = 0.575, P < .04, respectively). No correlation was found for IL-1β.

CONCLUSION

These data demonstrate that matrix production in transplanted chondrocytes affects maturation of MACT grafts in MRI 2 years after surgery.

Development of a Tool to Predict Outcome of Autologous Chondrocyte Implantation

Objective The study had 2 objectives: first, to evaluate the success of autologous chondrocyte implantation (ACI) in terms of incidence of surgical re-intervention, including arthroplasty, and investigate predictors of successful treatment outcome. The second objective was to derive a tool predicting a patient's arthroplasty risk following ACI. Design In this Level II, prognostic study, 170 ACI-treated patients (110 males [aged 36.8 ± 9.4 years]; 60 females [aged 38.1 ± 10.2 years]) completed a questionnaire about further surgery on their knee treated with ACI 10.9 ± 3.5 years previously. Factors commonly assessed preoperatively (age, gender, defect location and number, previous surgery at this site, and the preoperative Lysholm score) were used as independent factors in regression analyses. Results At final follow-up (maximum of 19 years post-ACI), 40 patients (23.5%) had undergone surgical re-intervention following ACI. Twenty-six patients (15.3%) underwent arthroplasty, more commonly females (25%) than males (10%; P = 0.001). Cox regression analyses identified 4 factors associated with re-intervention: age at ACI, multiple operations before ACI, patellar defects, and lower pretreatment Lysholm scores (Nagelkerke's R² = 0.20). Six predictive items associated with risk of arthroplasty following ACI (Nagelkerke's R² = 0.34) were used to develop the Oswestry Risk of Knee Arthroplasty index with internal cross-validation. Conclusion In a single-center study, we have identified 6 factors (age, gender, location and number of defects, number of previous operations, and Lysholm score before ACI) that appear to influence the likelihood of ACI patients progressing to arthroplasty. We have used this information to propose a formula or "tool" that could aid treatment decisions and improve patient selection for ACI.

An ex vivo human cartilage repair model to evaluate the potency of a cartilage cell transplant

Background

Cell-based therapies such as autologous chondrocyte implantation are promising therapeutic approaches to treat cartilage defects to prevent further cartilage degeneration. To assure consistent quality of cell-based therapeutics, it is important to be able to predict the biological activity of such products. This requires the development of a potency assay, which assesses a characteristic of the cell transplant before implantation that can predict its cartilage regeneration capacity after implantation. In this study, an ex vivo human cartilage repair model was developed as quality assessment tool for potency and applied to co.don’s chondrosphere product, a matrix-associated autologous chondrocyte implant (chondrocyte spheroids) that is in clinical use in Germany.

Methods

Chondrocyte spheroids were generated from 14 donors, and implanted into a subchondral cartilage defect that was manually generated in human articular cartilage tissue. Implanted spheroids and cartilage tissue were co-cultured ex vivo for 12 weeks to allow regeneration processes to form new tissue within the cartilage defect. Before implantation, spheroid characteristics like glycosaminoglycan production and gene and protein expression of chondrogenic markers were assessed for each donor sample and compared to determine donor-dependent variation.

Results

After the co-cultivation, histological analyses showed the formation of repair tissue within the cartilage defect, which varied in amount for the different donors. In the repair tissue, aggrecan protein was expressed and extra-cellular matrix cartilage fibers were present, both indicative for a cartilage hyaline-like character of the repair tissue. The amount of formed repair tissue was used as a read-out for regeneration capacity and was correlated with the spheroid characteristics determined before implantation. A positive correlation was found between high level of aggrecan protein expression in spheroids before implantation and a higher regeneration potential after implantation, reflected by more newly formed repair tissue.

Conclusion

This demonstrated that aggrecan protein expression levels in spheroids before implantation can potentially be used as surrogate potency assay for the cartilage cell transplant to predict its regenerative capacity after implantation in human patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1065-8) contains supplementary material, which is available to authorized users.

Matrix based autologous chondrocyte implantation in children and adolescents: a match paired analysis in a follow-up over three years post-operation

PURPOSE

The aim of this study is the investigation of the clinical results after third generation autologous chondrocyte implantation in the knee in a follow-up over three years post-operation. Our primary focus is on the effects of this procedure on children and adolescent patients as there is a lack of knowledge regarding the clinical outcomes in children/adolescents in particular when compared with adults.

METHODS

A total of 40 patients (43 defects) <20 years with cartilage defects of the knee were treated with third generation ACI (Novocart® 3D). These defects were caused by osteochondritis dissecans (n = 13), acute trauma (<12 months) (n = 9), old trauma (>12 months) (n = 5) or unknown pathology (n = 13). The mean defect size was 5.2 cm². IKDC subjective score and VAS (at rest and during activity) were used for clinical evaluation after 6, 12, 24 and 36 months post-operatively. The results of these patients were compared with 40 matched adult patients. Match paired analysis was performed by numbers of treated defects, defect location and defect size. All cartilage defects were arthroscopically classified with IKDC grade III-IV. All adult patients in the control group were treated with matrix based autologous chondrocyte implantation.

RESULTS

All patients showed significantly better clinical results compared with the pre-operative findings in the follow-up over three years. We observed significantly better results in the IKDC score and VAS during the whole postoperative follow-up in children and adolescents after six, 12, 24 and 36 months compared with the adult control group. The IKDC score improved from 46.5 preoperative to 77.5 (+31) after three years in children and adolescents. Similarly, significantly lower stress pain after six months and one, two and three years was found in this group.

CONCLUSION

This study showed that third generation autologous chondrocyte implantation is a suitable method for the treatment of full cartilage defects in children and adolescents.

Therapeutic potential of mesenchymal stem cell based therapy for osteoarthritis

Osteoarthritis (OA) is a chronic degenerative disease affecting articular cartilage in joints, and it is a leading cause of disability in the United States. Current pharmacological treatment strategies are ineffective to prevent the OA progression; however, cellular therapies have the potential to regenerate the lost cartilage, combat cartilage degeneration, provide pain relief, and improve patient mobility. One of the most promising sources of cellular regenerative medicine is from mesenchymal stem cells (MSCs). MSCs can be isolated from adipose tissue, bone marrow, synovial tissue, and other sources. The aim of this review is to compile recent advancement in cellular based therapy more specifically in relation to MSCs in the treatment of osteoarthritis.

Impact of guidance documents on translational large animal studies of cartilage repair

Promising therapies for cartilage repair are translated through large animal models toward human application. To guide this work, regulatory agencies publish recommendations ("guidance documents") to direct pivotal large animal studies. These are meant to aid in study design, outline metrics for judging efficacy, and facilitate comparisons between studies. To determine the penetrance of these documents in the field, we synthesized the recommendations of the American Society for Testing and Materials, U.S. Food and Drug Administration, and European Medicines Agency into a scoring system and performed a systematic review of the past 20 years of preclinical cartilage repair studies. Our hypothesis was that the guidance documents would have a significant impact on how large animal cartilage repair studies were performed. A total of 114 publications meeting our inclusion criteria were reviewed for adherence to 24 categories extracted from the guidance documents, including 11 related to study design and description and 13 related to study outcomes. Overall, a weak positive trend was observed over time (P = 0.004, R(2) = 0.07, slope = 0.63%/year), with overall adherence (the sum of study descriptors and outcomes) ranging from 32 ± 16% to 58 ± 14% in any individual year. There was no impact of the publication of the guidance documents on adherence (P = 0.264 to 0.50). Given that improved adherence would expedite translation, we discuss the reasons for poor adherence and outline approaches to increase and promote their more widespread adoption.

Incomplete defect filling after third generation autologous chondrocyte implantation

INTRODUCTION

Third generation autologous chondrocyte implantation (ACI) is a suitable method for the treatment of cartilage defects in the knee joint. However, knowledge about the development of graft thickness and the clinical relevance of incomplete defect filling in the postoperative course is low. This prospective study analyses the graft integration into the surrounding cartilage, with special consideration of the graft thickness.

MATERIAL AND METHODS

A total of 71 consecutive patients with 79 cartilage defects were treated with third generation autologous chondrocyte implantation (NOVOCART 3D) in the knee. Follow-up magnetic resonance imaging (MRI) was performed at 0.25, 0.5, 1 and 2 years. Graft thickness was measured compared to the surrounding healthy cartilage. The International Knee Documentation Committee (IKDC) scoring system and the visual analogue scale (VAS) were used for clinical evaluation. Cartilage defect filling was classified as the percentage of the surrounding cartilage.

RESULTS

The average graft thickness showed a significant increase between 3 and 6 months after autologous chondrocyte implantation. Incomplete defect filling occurred in 44 (55.7%) cases. Of these, 33 cases showed incomplete defect filling grade I (> 75%), 10 cases were grade II (> 50%) and one case grade III (> 25%). Incomplete defect filling grade IV (< 25%) was not observed. Incomplete defect filling occurred significantly more often in women (p = 0.021), without worse clinical results.

CONCLUSIONS

Graft thickness after third generation autologous chondrocyte implantation shows increasing graft thickness over the period of 2 years postoperatively. A high rate of incomplete defect filling in the surrounding cartilage was observed, without worse clinical results.

Symptoms and function in patients with articular cartilage lesions in 1,000 knee arthroscopies

PURPOSE

Focal chondral lesions of the knee are commonly occurring. A lot is known about their frequency, size and localisation in arthroscopic series, but less about the symptoms they elicit and little about how the arthroscopic findings and symptoms correlate. The purposes of the present study included to investigate the relationship between articular cartilage lesion factors and patient factors, and to compare the symptoms and function of cartilage lesion patients to those of patients with a deficient ACL.

METHODS

A prospective registration was conducted of preoperative data including Lysholm knee score and perioperative findings in 1,000 consecutive patients undergoing an arthroscopic procedure of the knee-including microfracture of articular cartilage defects and ACL reconstructions.

RESULTS

Chondral or osteochondral lesions were found in 57 % of the arthroscopies. The mean Lysholm score in this subgroup was 55. The mean Lysholm score was significantly lower in women (50, SD 19) compared to men (59, SD 18, p < 0.001). Among the chondral lesion factors, only kissing (vs. non-kissing) lesions and multiple (vs. single) lesions influenced symptoms and function to a more than negligible degree. Microfracture in one or two articular cartilage defects was performed in 187 patients. The microfracture group had a significant lower mean Lysholm score (54, SD 18) than a group of patients (N = 71) undergoing ACL reconstruction group (67, SD 17, p < 0.001).

CONCLUSION

The study confirms that articular cartilage lesions are both common and cumbersome. Women seem to have more problems than men, whereas chondral lesion factors-such as localisation and size-seem to influence symptoms and function to a small degree. These aspects should be addressed when designing outcome studies, and should also be of interest to the orthopaedic surgeon-in the day-by-day clinical work. When treating these patients, our prime focus need to be on knee function rather than the cartilage defect as the relationship between the latter and the former is unclear.

LEVEL OF EVIDENCE

Case-control study, Level III.

Gender Differences in Outcome After Modified Broström Procedure for Chronic Lateral Ankle Instability

BACKGROUND

The modified Broström procedure is commonly used for anatomic repair of chronic lateral ankle instability. However, no studies have compared outcomes of gender-based differences after the modified Broström procedure. We compared outcomes of the modified Broström procedure in men and women.

METHODS

A total of 155 patients (155 ankles) treated with the modified Broström procedure for chronic lateral ankle instability constituted the study cohort. The 155 ankles were divided into 2 groups: a men's group (94 ankles) and a women's group (61 ankles). The Karlsson score, American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score, talar tilt, and anterior talar translation were used to evaluate clinical and radiographic outcomes. The mean follow-up duration was 42.8 months (range, 24-101).

RESULTS

Mean preoperative Karlsson scores were 53.6 points (39-65) in the men's group and 54.9 points (39-65) in the women's group, and these improved to 93.2 (72-100) and 92.2 (80-100), respectively, at the final follow-up. Mean preoperative AOFAS ankle-hindfoot scores were 62.4 points (44-79) in men and 63.6 points (49-77) in women and 93.7 (72-100) and 92.3 (79-100), respectively, at the final follow-up. Mean preoperative talar tilt angles decreased from 11.9 degrees (2.5-27.5) in men and 11.4 degrees (0.9-24.7) in women to 6.0 (1.0-11.5) and 6.0 (2.3-11.9), respectively, at the final follow-up. Mean preoperative anterior talar translation in men and women improved from 8.6 mm (5.1-14.6) and 8.7 mm (2.3-11.9) to 6.0 (4.3-8.7) and 5.8 (3.3-9.9), respectively, at the final follow-up. No significant differences were found between men and women in terms of Karlsson scores, AOFAS scores, talar tilt angle, and anterior talar translation.

CONCLUSIONS

The modified Broström procedure showed similar good functional and radiographic outcomes in men and women. These results suggest that the modified Broström procedure is effective and reliable for treating chronic lateral ankle instability regardless of gender.

LEVEL OF EVIDENCE

Level III, retrospective comparative cohort study.

Significantly worse isokinetic hamstring-quadriceps ratio in patellofemoral compared to condylar defects 4 years after autologous chondrocyte implantation

PURPOSE

Detailed biomechanical analysis including isokinetic muscle strength measurements after autologous chondrocyte implantation (ACI) are still rare, but might be of crucial importance for long-term outcomes. The present prospective study was performed to evaluate whether defect location had any influence on clinical and biomechanical outcomes 4 years after ACI.

METHODS

Forty-four patients with full-thickness cartilage defects ICRS grade III B and C underwent ACI and were assigned to two groups, the femoral condyle group or the patellofemoral joint group. Clinical scores were gathered preoperatively and 6, 12 and 48 months after implantation using the International Knee Documentation Committee (IKDC) score and the International Cartilage Repair Society (ICRS) form. Isokinetic strength measurements were performed 48 months postoperatively comparing healthy and operated knee joint of each patient.

RESULTS

Clinical scores (ICRS, IKDC) showed continuous significant (p < 0.05) improvement over the study period for both groups. Isokinetic muscle strength measurements showed significantly reduced maximum strength capacities for the operated knee joint compared to the healthy knee in both groups (p < 0.05). Hamstring-quadriceps ratios of the operated extremity revealed a significant change in physiological muscle balancing (ratios >1.0) based on significantly impaired extensor muscle strength in the patellofemoral joint group.

CONCLUSION

All patients showed significant strength deficits on the operated extremity 4 years after ACI. Furthermore, the patellofemoral compartment in particular showed significantly worse hamstring-quadriceps ratios compared to condylar defects. Consequently, more efforts should be made to restore muscular strength especially of the quadriceps and the rehabilitation protocol should be adjusted accordingly.

LEVEL OF EVIDENCE

II.

Are surface antigens suited to verify the redifferentiation potential and culture purity of human chondrocytes in cell-based implants

Cell expansion in vitro is a prequisite to obtain a sufficient quantity of cells for cell-based cartilage repair of articular cartilage lesions. During this process verification of redifferentiation potential of highly expanded chondrocytes is required. Furthermore, cellular impurities of chondrocyte cultures have to be excluded. For this purpose, redifferentiation of expanded human chondrocytes in passage 3 or 5 was initiated in bioresorbable polyglycolic acid-fibrin (PGA-fibrin) scaffolds and selected potential markers were analysed during the process of cell expansion and redifferentiation. Chondrocyte expansion was accompanied by a decrease of collagen type II and COMP and an increase of collagen type I expression indicating cell dedifferentiation. Redifferentiation of chondrocytes in PGA-fibrin scaffolds was accompanied by an increase of collagen II/I ratio. Flow cytometric analyses revealed that in contrast to CD44 and CD49e, CD63 and CD166 showed significant changes in the number of positive cells during redifferentiation. CD14 and CD45 are not expressed by chondrocytes and are therefore possible candidates to detect specifically monocytes or haematopoetic cells in chondrocyte cultures. Characterization of surface antigen expression revealed two promising candidates (CD63 and CD166) to describe the process of redifferentiation, while CD14 and CD45 are suitable markers to exclude impurities by monocytes or haematopoetic cells.

Revision surgery after third generation autologous chondrocyte implantation in the knee

PURPOSE

Third generation autologous chondrocyte implantation (ACI) is an established treatment for full thickness cartilage defects in the knee joint. However, little is known about cases when revision surgery is needed. The aim of the present study is to investigate the complication rates and the main reasons for revision surgery after third generation autologous chondrocyte implantation in the knee joint. It is of particular interest to examine in which cases revision surgery is needed and in which cases a "wait and see" strategy should be used.

METHODS

A total of 143 consecutive patients with 171 cartilage defects were included in this study with a minimum follow-up of two years. All defects were treated with third generation ACI (NOVACART®3D). Clinical evaluation was carried out after six months, followed by an annual evaluation using the International Knee Documentation Committee (IKDC) subjective score and the visual analogue scale (VAS) for rest and during activity. Revision surgery was documented.

RESULTS

The revision rate was 23.4 % (n = 36). The following major reasons for revision surgery were found in our study: symptomatic bone marrow edema (8.3 %, n = 3), arthrofibrosis (22.2 %, n = 8) and partial graft cartilage deficiency (47.2 %, n = 17). The following revision surgery was performed: retrograde drilling combined with Iloprost infusion therapy for bone marrow oedema (8.4 %, n = 3), arthroscopic arthrolysis of the suprapatellar recess (22.2 %, n = 8) and microfracturing/antegrade drilling (47.3 %, n = 17). Significant improvements of clinical scores after revision surgery were observed.

CONCLUSION

Revision surgery after third generation autologous chondrocyte implantation is common and is needed primarily in cases with arthrofibrosis, partial graft cartilage deficiency and symptomatic bone marrow oedema resulting in a significantly better clinical outcome.

Bone Marrow Edema in the Knee and Its Influence on Clinical Outcome After Matrix-Based Autologous Chondrocyte Implantation: Results After 3-Year Follow-up

BACKGROUND

Third-generation autologous chondrocyte implantation (ACI) is an established method for treatment of full-thickness cartilage defects in the knee joint. Subchondral bone marrow edema (BME) is frequently observed after ACI, with unknown pathogenesis and clinical relevance.

PURPOSE

To investigate the occurrence and clinical relevance of BME after third-generation ACI in the knee joint during the postoperative course of 36 months.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 38 circumscribed full-thickness cartilage defects in 30 patients were included in this study. All defects were treated with third-generation ACI (Novocart 3D). A standardized MRI examination was carried out after 1.5, 3, 6, 12, 24, and 36 months. Bone marrow edema was observed in 78.9% of defects over the postoperative course, with initial occurrence in the first 12 months. The size of the BMEs were determined according to their maximum diameter and were classified as small (<1 cm), medium (<2 cm), large (<4 cm), and very large (diffuse; >4 cm). Clinical outcomes in patients were analyzed by use of the International Knee Documentation Committee (IKDC) scoring system and a visual analog scale for pain.

RESULTS

There were 5.3% (n=2) small, 28.9% (n=11) medium, 34.2% (n=13) large, and 10.5% (n=4) very large BMEs. In a subgroup analysis, cartilage defects of the medial femoral condyle showed significantly higher frequency of BME than did patellar defects. Clinical scores showed significant improvements throughout the entire study course (P<.05). Clinical patient outcome did not correlate with presence of BME at any time period (P>.05).

CONCLUSION

Midterm clinical results of the matrix-based third-generation ACI showed a substantial amount of BME over a 36-month follow-up, but this did not correlate with worse clinical outcome. Patients with femoral cartilage defects were more often affected than were those with patellar cartilage defects.