Treatment of Full-Thickness Chondral Defects With Hyalograft C in the Knee: Long-term Results

Sex does not influence the long-term outcome of matrix-assisted autologous chondrocyte transplantation

PURPOSE

Regenerative techniques for articular cartilage lesions demonstrated heterogeneous clinical results. Several factors may influence the outcome, with sex being one of the most debated. This study aimed at quantifying the long-term influence of sex on the clinical outcome obtained with a regenerative procedure for knee chondral lesions.

METHODS

Matrix-assisted autologous chondrocyte transplantation (MACT) was used to treat 235 knees which were prospectively evaluated with the International Knee Documentation Committee (IKDC), EuroQol visual analogue scale, and Tegner scores at 14-year mean follow-up. A multilevel analysis was performed with the IKDC subjective scores standardised according to the age/sex category of each patient and/or the selection of a match-paired subgroup to compare homogeneous men and women patients.

RESULTS

At 14 years, men and women showed a failure rate of 10.7% and 28.8%, respectively (p < 0.0005). An overall improvement was observed in both sexes. Women had more patellar lesions and men more condylar lesions (p = 0.001), and the latter also presented a higher preinjury activity level (p < 0.0005). Men had significantly higher IKDC subjective scores at all follow-ups (at 14 years: 77.2 ± 18.9 vs. 62.8 ± 23.1; p < 0.0005). However, the analysis of homogeneous match-paired populations of men and women, with standardised IKDC subjective scores, showed no differences between men and women (at 14 years: -1.6 ± 1.7 vs. -1.9 ± 1.6).

CONCLUSION

Men and women treated with MACT for knee chondral lesions presented a significant improvement and stable long-term results. When both sexes are compared with homogeneous match-paired groups, they have similar results over time. However, women present more often unfavourable lesion patterns, which proved more challenging in terms of long-term outcome after MACT.

LEVEL OF EVIDENCE

Level II.

Berberine oleanolic acid complex salt grafted hyaluronic acid/silk fibroin (BOA-g-HA/SF) composite scaffold promotes cartilage tissue regeneration under IL-1β caused stress

Since inflammatory cytokines cause stress to chondrocytes and the failure of cartilage defects repair with cartilage tissue engineering, it is necessary to develop a scaffold to maintain cartilage regeneration under inflammatory factors caused stress. Following a berberine-oleanolic acid (OA) complex salt (BOA) was grafted to hyaluronic acid (HA) to obtain water soluble BOA-g-HA, it mixed with silk fibroin (SF) to prepared 4 solutions, which contained 30 mg/mL SF and 0.75, 1.5, 2.25, and 3.0 mg/mL BOA-g-HA respectively. They were lyophilized to fabricate BOA-g-HA/SF-1, BOA-g-HA/SF-2, BOA-g-HA/SF-3, and BOA-g-HA/SF-4 composite scaffolds respectively. All prepared scaffolds displayed porous network structure and exhibited promising mechanical properties for tissue engineering applications. Among them, the BOA-g-HA/SF-3 composite scaffold showed the highest influence on maintaining chondrocytic phenotype of chondrocytes under IL-1β induced stress. Following SF, HA/SF, and BOA-g-HA/SF-3 composite scaffolds with seeded chondrocytes were treated with IL-1β induction for 1 week, specimens were incubated with cell culture medium for 3 week or were subcutaneously implanted into nude mice for 4 weeks. The results demonstrated that the BOA-g-HA/SF-3 composite scaffold promotes cartilage tissue regeneration in vitro and in vivo under IL-1β caused stress, suggesting that it can be potential applied for repairing cartilage defects in osteoarthritis patients.

A Photopolymerizable Biocompatible Hyaluronic Acid Hydrogel Promotes Early Articular Cartilage Repair in a Minipig Model In Vivo

Articular cartilage defects represent an unsolved clinical challenge. Photopolymerizable hydrogels are attractive candidates supporting repair. This study investigates the short-term safety and efficacy of two novel hyaluronic acid (HA)-triethylene glycol (TEG)-coumarin hydrogels photocrosslinked in situ in a clinically relevant large animal model. It is hypothesized that HA-hydrogel-augmented microfracture (MFX) is superior to MFX in enhancing early cartilage repair, and that the molar degree of substitution and concentration of HA affects repair. Chondral full-thickness defects in the knees of adult minipigs are treated with either 1) debridement (No MFX), 2) debridement and MFX, 3) debridement, MFX, and HA hydrogel (30% molar derivatization, 30 mg mL-1 HA; F3) (MFX+F3), and 4) debridement, MFX, and HA hydrogel (40% molar derivatization, 20 mg mL-1 HA; F4) (MFX+F4). After 8 weeks postoperatively, MFX+F3 significantly improves total macroscopic and histological scores compared with all other groups without negative effects, besides significantly enhancing the individual repair parameters "defect architecture," "repair tissue surface" (compared with No MFX, MFX), and "subchondral bone" (compared with MFX). These data indicate that photopolymerizable HA hydrogels enable a favorable metastable microenvironment promoting early chondrogenesis in vivo. This work also uncovers a mechanism for effective HA-augmented cartilage repair by combining lower molar derivatization with higher concentrations.

Autologous and Allogeneic Cytotherapies for Large Knee (Osteo)Chondral Defects: Manufacturing Process Benchmarking and Parallel Functional Qualification

Cytotherapies are often necessary for the management of symptomatic large knee (osteo)-chondral defects. While autologous chondrocyte implantation (ACI) has been clinically used for 30 years, allogeneic cells (clinical-grade FE002 primary chondroprogenitors) have been investigated in translational settings (Swiss progenitor cell transplantation program). The aim of this study was to comparatively assess autologous and allogeneic approaches (quality, safety, functional attributes) to cell-based knee chondrotherapies developed for clinical use. Protocol benchmarking from a manufacturing process and control viewpoint enabled us to highlight the respective advantages and risks. Safety data (telomerase and soft agarose colony formation assays, high passage cell senescence) and risk analyses were reported for the allogeneic FE002 cellular active substance in preparation for an autologous to allogeneic clinical protocol transposition. Validation results on autologous bioengineered grafts (autologous chondrocyte-bearing Chondro-Gide scaffolds) confirmed significant chondrogenic induction (COL2 and ACAN upregulation, extracellular matrix synthesis) after 2 weeks of co-culture. Allogeneic grafts (bearing FE002 primary chondroprogenitors) displayed comparable endpoint quality and functionality attributes. Parameters of translational relevance (transport medium, finished product suturability) were validated for the allogeneic protocol. Notably, the process-based benchmarking of both approaches highlighted the key advantages of allogeneic FE002 cell-bearing grafts (reduced cellular variability, enhanced process standardization, rationalized logistical and clinical pathways). Overall, this study built on our robust knowledge and local experience with ACI (long-term safety and efficacy), setting an appropriate standard for further clinical investigations into allogeneic progenitor cell-based orthopedic protocols.

Adhesive hydrogels in osteoarthritis: from design to application

Osteoarthritis (OA) is the most common type of degenerative joint disease which affects 7% of the global population and more than 500 million people worldwide. One research frontier is the development of hydrogels for OA treatment, which operate either as functional scaffolds of tissue engineering or as delivery vehicles of functional additives. Both approaches address the big challenge: establishing stable integration of such delivery systems or implants. Adhesive hydrogels provide possible solutions to this challenge. However, few studies have described the current advances in using adhesive hydrogel for OA treatment. This review summarizes the commonly used hydrogels with their adhesion mechanisms and components. Additionally, recognizing that OA is a complex disease involving different biological mechanisms, the bioactive therapeutic strategies are also presented. By presenting the adhesive hydrogels in an interdisciplinary way, including both the fields of chemistry and biology, this review will attempt to provide a comprehensive insight for designing novel bioadhesive systems for OA therapy.

Biological Reconstruction of Localized Full-Thickness Cartilage Defects of the Knee: A Systematic Review of Level 1 Studies with a Minimum Follow-Up of 5 Years

OBJECTIVE

The objective of this study was to evaluate the best available mid- to long-term evidence of surgical procedures for the treatment of localized full-thickness cartilage defects of the knee.

DESIGN

Systematic review using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines of Level 1 randomized clinical trials (RCTs), meta-analyses of RCTs and systematic reviews with a minimum follow-up of 5 years. Data extracted included patient demographics, defect characteristics, clinical and radiological outcomes, as well as treatment failures.

RESULTS

Six RCTs and 3 Level 1 systematic reviews were included. Two RCTs compared microfracture (MFx) to periosteum-covered autologous chondrocyte implantation (ACI-P), 1 to matrix-associated ACI (M-ACI) and 2 to osteochondral autograft transplantation (OAT). One study compared OAT to collagen membrane covered ACI (ACI-C). The 3 Level 1 systematic reviews/meta-analyses assessed the outcome of MFx, OAT, and various ACI methods in RCTs. OAT showed significantly better outcomes compared with MFx. In the 2 RCTs comparing ACI-P and MFx, no significant differences in clinical outcomes were seen, whereas significantly better outcomes were reported for M-ACI versus MFx in 1 study including patients with larger defects (5 cm²), and for ACI-C versus OAT in terms of Cincinnati Score. Higher failure rates were reported for MFx compared with OAT and for OAT compared with ACI-C, while no significant differences in failure rates were observed for ACI-P compared to MFx.

CONCLUSION

Restorative cartilage procedures (ACI-C or M-ACI and OAT) are associated with better long-term clinical outcomes including lower complication and failure rates when compared with reparative techniques (MFx). Among the restorative procedures, OAT seems to be inferior to ACI especially in larger defects after longer follow-up periods.

LEVEL OF EVIDENCE

Level I: Systematic review of Level I studies.

The immune microenvironment in cartilage injury and repair

The ability of articular cartilage to repair itself is limited because it lacks blood vessels, nerves, and lymph tissue. Once damaged, it can lead to joint swelling and pain, accelerating the progression of osteoarthritis. To date, complete regeneration of hyaline cartilage exhibiting mechanical properties remains an elusive goal, despite the many available technologies. The inflammatory milieu created by cartilage damage is critical for chondrocyte death and hypertrophy, extracellular matrix breakdown, ectopic bone formation, and progression of cartilage injury to osteoarthritis. In the inflammatory microenvironment, mesenchymal stem cells (MSCs) undergo aberrant differentiation, and chondrocytes begin to convert or dedifferentiate into cells with a fibroblast phenotype, thereby resulting in fibrocartilage with poor mechanical qualities. All these factors suggest that inflammatory problems may be a major stumbling block to cartilage repair. To produce a milieu conducive to cartilage repair, multi-dimensional management of the joint inflammatory microenvironment in place and time is required. Therefore, this calls for elucidation of the immune microenvironment of cartilage repair after injury. This review provides a brief overview of: (1) the pathogenesis of cartilage injury; (2) immune cells in cartilage injury and repair; (3) effects of inflammatory cytokines on cartilage repair; (4) clinical strategies for treating cartilage defects; and (5) strategies for targeted immunoregulation in cartilage repair. STATEMENT OF SIGNIFICANCE: Immune response is increasingly considered the key factor affecting cartilage repair. It has both negative and positive regulatory effects on the process of regeneration and repair. Proinflammatory factors are secreted in large numbers, and necrotic cartilage is removed. During the repair period, immune cells can secrete anti-inflammatory factors and chondrogenic cytokines, which can inhibit inflammation and promote cartilage repair. However, inflammatory factors persist, which accelerate the degradation of the cartilage matrix. Furthermore, in an inflammatory microenvironment, MSCs undergo abnormal differentiation, and chondrocytes begin to transform or dedifferentiate into fibroblast-like cells, forming fibrocartilage with poor mechanical properties. Consequently, cartilage regeneration requires multi-dimensional regulation of the joint inflammatory microenvironment in space and time to make it conducive to cartilage regeneration.

Safety and Efficacy of Matrix-Associated Autologous Chondrocyte Implantation With Spheroids for Patellofemoral or Tibiofemoral Defects: A 5-Year Follow-up of a Phase 2, Dose-Confirmation Trial

Background:

Matrix-associated autologous chondrocyte implantation (ACI) is a well-established treatment for cartilage defects. High-level evidence at midterm follow-up is limited, especially for ACI using spheroids (spherical aggregates of ex vivo expanded human autologous chondrocytes and self-synthesized extracellular matrix).

Purpose:

To assess the safety and efficacy of 3-dimensional matrix-associated ACI using spheroids to treat medium to large cartilage defects on different locations in the knee joint (patella, trochlea, and femoral condyle) at 5-year follow-up.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

A total of 75 patients aged 18 to 50 years with medium to large (4-10 cm²), isolated, single cartilage defects, International Cartilage Repair Society grade 3 or 4, were randomized on a single-blind basis to treatment with ACI at 1 of 3 dose levels: 3 to 7, 10 to 30, or 40 to 70 spheroids/cm² of defect size. Outcomes were assessed via changes from baseline Knee injury and Osteoarthritis Outcome Score (KOOS), International Knee Documentation Committee score, and modified Lysholm assessments at 1- and 5-year follow-up. Structural repair was evaluated using MOCART (magnetic resonance observation of cartilage repair tissue) score. Treatment-related adverse events were assessed up to 5 years for all patients. The overall KOOS at 12 months was assessed for superiority versus baseline in a 1-sample, 2-sided t test.

Results:

A total of 73 patients were treated: 24 in the low-dose group, 25 in the medium-dose group, and 24 in the high-dose group. The overall KOOS improved from 57.0 ± 15.2 at baseline to 73.4 ± 17.3 at 1-year follow-up (P < .0001) and 76.9 ± 19.3 at 5-year follow-up (P < .0001), independent of the applied dose. The different defect locations (patella, trochlea, and weightbearing part of the femoral condyles; P = .2216) and defect sizes (P = .8706) showed comparable clinical improvement. No differences between the various doses were observed. The overall treatment failure rate until 5 years was 4%. Most treatment-related adverse events occurred within the first 12 months after implantation, with the most frequent adverse reactions being joint effusion (n = 71), arthralgia (n = 14), and joint swelling (n = 9).

Conclusion:

ACI using spheroids was safe and effective for defect sizes up to 10 cm² and showed maintenance of efficacy up to 5 years for all 3 doses that were investigated.

Registration:

NCT01225575 (ClinicalTrials.gov identifier); 2009-016816-20 (EudraCT number).

Matrix-Associated Autologous Chondrocyte Implantation with Spheroid Technology Is Superior to Arthroscopic Microfracture at 36 Months Regarding Activities of Daily Living and Sporting Activities after Treatment

OBJECTIVE

Matrix-associated autologous chondrocyte implantation (ACI) and microfracture (MF) are well-established treatments for cartilage defects of the knee. However, high-level evidence comparing microfracture and spheroid technology ACI is limited.

DESIGN

Prospective, phase III clinical trial with patients randomized to ACI (N = 52) or MF (N = 50). Level of evidence: 1, randomized controlled trial. Both procedures followed standard protocols. For ACI 10 to 70 spheroids/cm² were administered. Primary outcome measure was the Knee Injury and Osteoarthritis Outcome Score (KOOS). This report presents results for 36 months after treatment.

RESULTS

Both ACI and MF showed significant improvement over the entire 3-year observation period. For the overall KOOS, noninferiority of ACI (the intended primary goal of the study) was formally confirmed; additionally, for the subscores "Activities of Daily Living" and "Sport and Recreation," superiority of ACI over MF was shown at descriptive level. Occurrence of adverse events were not different between both treatments (ACI 77%; MF 74%). Four patients in the MF group required reoperation which was defined as treatment failure. No treatment failure was reported for the ACI group.

CONCLUSIONS

Patients treated with matrix-associated ACI with spheroid technology showed substantial improvement in various clinical outcomes after 36 months. The advantages of ACI compared with microfracture was underlined by demonstrating noninferiority, in overall KOOS and superiority in the KOOS subscores "Activities of Daily Living" and "Sport and Recreation." In the present study, subgroups comparing different age groups and defect sizes showed comparable clinical outcomes.

Scaffolds for Knee Chondral and Osteochondral Defects: Indications for Different Clinical Scenarios. A Consensus Statement

OBJECTIVE

To develop patient-focused consensus guidelines on the indications for the use of scaffolds to address chondral and osteochondral femoral condyle lesions.

DESIGN

The RAND/UCLA Appropriateness Method (RAM) was used to develop patient-specific recommendations by combining the best available scientific evidence with the collective judgement of a panel of experts guided by a core panel and multidisciplinary discussers. A list of specific clinical scenarios was produced regarding adult patients with symptomatic lesions without instability, malalignment, or meniscal deficiency. Each scenario underwent discussion and a 2-round vote on a 9-point Likert-type scale (range 1-3 "inappropriate," 4-6 "uncertain," 7-9 "appropriate"). Scores were pooled to generate expert recommendations.

RESULTS

Scaffold (chondral vs. osteochondral), patient characteristics (age and sport activity level), and lesion characteristics (etiology, size, and the presence of osteoarthritis [OA]) were considered to define 144 scenarios. The use of scaffold-based procedures was considered appropriate in all cases of chondral or osteochondral lesions when joints are not affected by OA, while OA joints presented more controversial results. The analysis of the evaluated factors showed a different weight in influencing treatment appropriateness: the presence of OA influenced 58.3% of the indications, while etiology, size, and age were discriminating factors in 54.2%, 29.2%, and 16.7% of recommendations, respectively.

CONCLUSIONS

The consensus identified indications still requiring investigation, but also the convergence of the experts in several scenarios defined appropriate or inappropriate, which could support decision making in the daily clinical practice, guiding the use of scaffold-based procedures for the treatment of chondral and osteochondral knee defects.

A Systematic Review of Focal Cartilage Defect Treatments in Middle-Aged Versus Younger Patients

Background:

Focal cartilage defects are often debilitating, possess limited potential for regeneration, are associated with increased risk of osteoarthritis, and are predictive for total knee arthroplasty. Cartilage repair studies typically focus on the outcome in younger patients, but a high proportion of treated patients are 40 to 60 years of age (ie, middle-aged). The reality of current clinical practice is that the ideal patient for cartilage repair is not the typical patient. Specific attention to cartilage repair outcomes in middle-aged patients is warranted.

Purpose:

To systematically review available literature on knee cartilage repair in middle-aged patients and include studies comparing results across different age groups.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A systematic search was performed in EMBASE, MEDLINE, and the Cochrane Library database. Articles were screened for relevance and appraised for quality.

Results:

A total of 21 articles (mean Coleman Methodology Score, 64 points) were included. Two out of 3 bone marrow stimulation (BMS) studies, including 1 using the microfracture technique, revealed inferior clinical outcomes in middle-aged patients in comparison with younger patients. Nine cell-based studies were included showing inconsistent comparisons of results across age groups for autologous chondrocyte implantation (ACI). Bone marrow aspirate concentrate showed age-independent results at up to 8 years of follow-up. A negative effect of middle age was reported in 1 study for both ACI and BMS. Four out of 5 studies on bone-based resurfacing therapies (allografting and focal knee resurfacing implants [FKRIs]) showed age-independent results up to 5 years. One study in only middle-aged patients reported better clinical outcomes for FKRIs when compared with biological repairs.

Conclusion:

Included studies were heterogeneous and had low methodological quality. BMS in middle-aged patients seems to only result in short-term improvements. More research is warranted to elucidate the ameliorating effects of cell-based therapies on the aging joint homeostasis. Bone-based therapies seem to be relatively insensitive to aging and may potentially result in effective joint preservation. Age subanalyses in cohort studies, randomized clinical trials, and international registries should generate more evidence for the large but underrepresented (in terms of cartilage repair) middle-aged population in the literature.

Matrix-assisted chondrocyte transplantation with bone grafting for knee osteochondritis dissecans: stable results at 12 years

PURPOSE

To document clinical and radiological results of arthroscopic matrix-assisted autologous chondrocyte transplantation (MACT) combined with bone grafting for the treatment of knee osteochondritis dissecans (OCD) at long-term follow-up.

METHODS

Thirty-one knees in 29 patients (20.4 ± 5.7 years) were treated for symptomatic unfixable OCD lesions (2.6 ± 1.1 cm²) and prospectively evaluated at 2, 5, and 12 years (average, minimum 10 years). Patients were evaluated over time with IKDC subjective score, EQ-VAS, and Tegner scores. Failures were also documented. At the final follow-up, MRI evaluation was performed in 14 knees with the MOCART 2.0 score.

RESULTS

Beside 4 early failures, an overall clinical improvement was documented: the IKDC subjective score improved from 39.9 ± 16.8 to 82.1 ± 17.0 and 84.8 ± 17.2 at 2 and 5 years, respectively (p < 0.0005), and remained stable for up to 12 years (85.0 ± 20.2). EQ-VAS and Tegner scores presented similar trends, but patients did not reach their original activity level. Worse results were obtained for lesions bigger than 4 cm². At MRI evaluation, subchondral bone abnormalities were detected in over 85% of knees at long-term follow-up.

CONCLUSIONS

Arthroscopic bone grafting followed by MACT for unfixable knee OCD can offer a promising and stable clinical outcome over time in lesions smaller than 4 cm², with a low failure rate of 13%. Persistent subchondral alterations were documented at long-term MRI evaluation, suggesting the limits of this approach to regenerate the osteochondral unit in patients affected by knee OCD.

LEVEL OF EVIDENCE

IV.

Deep learning enables the automation of grading histological tissue engineered cartilage images for quality control standardization

OBJECTIVE

To automate the grading of histological images of engineered cartilage tissues using deep learning.

METHODS

Cartilaginous tissues were engineered from various cell sources. Safranin O and fast green stained histological images of the tissues were graded for chondrogenic quality according to the Modified Bern Score, which ranks images on a scale from zero to six according to the intensity of staining and cell morphology. The whole images were tiled, and the tiles were graded by two experts and grouped into four categories with the following grades: 0, 1-2, 3-4, and 5-6. Deep learning was used to train models to classify images into these histological score groups. Finally, the tile grades per donor were averaged. The root mean square errors (RMSEs) were calculated between each user and the model.

RESULTS

Transfer learning using a pretrained DenseNet model was selected. The RMSEs of the model predictions and 95% confidence intervals were 0.49 (0.37, 0.61) and 0.78 (0.57, 0.99) for each user, which was in the same range as the inter-user RMSE of 0.71 (0.51, 0.93).

CONCLUSION

Using supervised deep learning, we could automate the scoring of histological images of engineered cartilage and achieve results with errors comparable to inter-user error. Thus, the model could enable the automation and standardization of assessments currently used for experimental studies as well as release criteria that ensure the quality of manufactured clinical grafts and compliance with regulatory requirements.

Hyaluronic Acid-Based Shape-Memory Cryogel Scaffolds for Focal Cartilage Defect Repair

Traumatic joint injuries can result in significant cartilage defects, which can greatly increase the risk of osteoarthritis development. Due to the limited self-healing capacity of avascular cartilage, tissue engineering approaches are required for filling defects and promoting cartilage regeneration. Current approaches utilize invasive surgical procedures for extraction and implantation of autologous chondrocytes; therefore, injectable biomaterials have gained interest to minimize the risk of infection as well as patient pain and discomfort. In this study, we engineered biomimetic, hyaluronic acid (HA)-based cryogel scaffolds that possess shape-memory properties as they contract and regain their shape after syringe injection to noninvasively fill cartilage defects. The cryogels, fabricated with HA and glycidyl methacrylate at -20°C, resulted in an elastic, macroporous, and highly interconnected network that provided a conducive microenvironment for chondrocytes to remain viable and metabolically active after injection through a syringe needle. Chondrocytes seeded within cryogels and cultured for 15 days exhibited enhanced cell proliferation, metabolism, and production of cartilage extracellular matrix glycosaminoglycans compared with HA-based hydrogels. Furthermore, immunohistochemical staining revealed production of collagen type II from chondrocyte-seeded cryogels, indicating the maintenance of cell phenotype. These results demonstrate the potential of chondrocyte-seeded, HA-based, injectable cryogel scaffolds to promote regeneration of cartilage tissue for nonsurgically invasive defect repair. Impact statement Hyaluronic acid-based shape-memory cryogels provide a conducive microenvironment for chondrocyte adhesion, proliferation, and matrix biosynthesis for use in repair of cartilage defects. Due to their sponge-like elastic properties, cryogels can fully recover their original shape back after injection while not impacting metabolism or viability of encapsulated cells. Clinically, they provide an opportunity for filling focal cartilage defects by using a single, minimally invasive injection of a cell encapsulating biocompatible three-dimensional scaffold that can return to its original structure to fit the defect geometry and enable matrix regeneration.

Long-term Results of Arthroscopic Matrix-Assisted Autologous Chondrocyte Transplantation: A Prospective Follow-up at 15 Years

BACKGROUND

Matrix-assisted autologous chondrocyte transplantation (MACT) procedures have been developed to overcome some of the limits of first-generation autologous chondrocyte implantation. However, while good autologous chondrocyte implantation results have been documented over time, data are scarce on the long-term MACT results.

PURPOSE

To evaluate long-term clinical results of a large cohort of patients treated with hyaluronic acid-based MACT for articular cartilage defects of the knee.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A long-term evaluation of 113 patients was performed (91 men, 22 women; mean ± SD age, 29.0 ± 10.6 years) for 115 knees affected by chondral and osteochondral lesions of the femoral condyles and trochlea. Of these, 61 knees had undergone previous surgery, while other procedures were combined during the same operation in 48 knees. These patients were prospectively evaluated before surgery and at 2, 5, and 10 years after surgery, as well as at a final mean follow-up of 15 years (range, 12-18 years), with various clinical scores: International Knee Documentation Committee (IKDC), EuroQol visual analog scale (EQ-VAS), and Tegner. Both surgical and clinical failures were documented.

RESULTS

The IKDC subjective score increased from the basal level of 39.9 ± 14.6 (mean ± SD) to 77.3 ± 20.5 (P < .0005) at 2 years; results remained stable up to the 15-year follow-up (76.9 ± 20.5). EQ-VAS and Tegner scores showed a statistically significant improvement up to 10 years, with a further significant improvement at the final follow-up. A failure rate of 15.0% was documented, which increased to 21.7% when clinical failures were also considered. A worse outcome was found for older age (P < .0005), female sex (P = .002), degenerative lesions (P < .0005), longer duration of symptoms (P = .005), and previous surgery (P < .0005).

CONCLUSION

Arthroscopic MACT offered good and long-lasting results that were stable over time and resulted in a limited number of failures and reinterventions for up to 15 years of follow-up. Several factors were identified as having a prognostic value: a worse outcome could be expected in older patients, female patients, those affected by lesions with a degenerative cause, those having a longer duration of symptoms, and patients who underwent previous surgery.

Mechanotransduction and Stiffness-Sensing: Mechanisms and Opportunities to Control Multiple Molecular Aspects of Cell Phenotype as a Design Cornerstone of Cell-Instructive Biomaterials for Articular Cartilage Repair

Since material stiffness controls many cell functions, we reviewed the currently available knowledge on stiffness sensing and elucidated what is known in the context of clinical and experimental articular cartilage (AC) repair. Remarkably, no stiffness information on the various biomaterials for clinical AC repair was accessible. Using mRNA expression profiles and morphology as surrogate markers of stiffness-related effects, we deduced that the various clinically available biomaterials control chondrocyte (CH) phenotype well, but not to equal extents, and only in non-degenerative settings. Ample evidence demonstrates that multiple molecular aspects of CH and mesenchymal stromal cell (MSC) phenotype are susceptible to material stiffness, because proliferation, migration, lineage determination, shape, cytoskeletal properties, expression profiles, cell surface receptor composition, integrin subunit expression, and nuclear shape and composition of CHs and/or MSCs are stiffness-regulated. Moreover, material stiffness modulates MSC immuno-modulatory and angiogenic properties, transforming growth factor beta 1 (TGF-β1)-induced lineage determination, and CH re-differentiation/de-differentiation, collagen type II fragment production, and TGF-β1- and interleukin 1 beta (IL-1β)-induced changes in cell stiffness and traction force. We then integrated the available molecular signaling data into a stiffness-regulated CH phenotype model. Overall, we recommend using material stiffness for controlling cell phenotype, as this would be a promising design cornerstone for novel future-oriented, cell-instructive biomaterials for clinical high-quality AC repair tissue.

High-Grade Patellar Chondral Defects: Promising Results From Management With Osteochondral Autografts

Background:

Patellar chondral defects represent up to 34.6% of defects found during routine arthroscopy. Surgical management has evolved during the past 20 years in an effort to develop techniques to replace hyaline cartilage. Currently, the only technique that achieves this is osteochondral autologous transfer (OAT). Although good and excellent results have often been reported at midterm and long-term follow-up for femoral lesions, little is known about isolated patellar defects.

Purpose:

To assess clinical and imaging results of patients treated with OAT for high-grade patellar defects.

Study Design:

Case series; Level of evidence, 4.

Methods:

This was a retrospective study on all patients who received OAT for high-grade symptomatic patellar chondral defects between 2010 and 2018 at our institution. The study included patients younger than 40 years of age with anterior knee pain and a grade 4 International Cartilage Repair Society patellar chondral defect between 1 and 2.5 cm². Patients with surgery in other knee compartments, concomitant anterior cruciate ligament ruptures, infection, rheumatoid arthritis, and degenerative lesions were excluded. Six months postoperatively, all patients underwent magnetic resonance imaging (MRI) to allow assessment of graft integrity via the MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) score to evaluate morphologic features and integration. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Kujala scores were used to assess functional outcomes at final follow-up.

Results:

A total of 26 patients who received a patellar OAT were included. Most patients were male (88.4%), and the mean ± SD age was 28.5 ± 9.7 years. Patellar chondral defects had a median size of 180 mm² (range, 64-250 mm²), and patients received a median of 1 autograft (range, 1-3). Functional outcomes assessed at a minimum of 1 year after surgery showed a mean Kujala score of 90.42 ± 6.7 and a mean WOMAC score of 95 ± 3.6. MRI revealed a median MOCART score of 75 points (range, 20-90 points).

Conclusion:

To our knowledge, this is the largest series to date regarding isolated patellar OAT. At midterm follow-up, most patients reported good and excellent results regarding symptoms and activity levels. Most autografts showed good osseous integration and excellent filling of the chondral surface, as evidenced on MRI. OAT is a good alternative to treat high-grade patellar chondral defects, especially among young patients.

Biological Regeneration of Articular Cartilage in an Early Stage of Compartmentalized Osteoarthritis: 12-Month Results

BACKGROUND

Biological regeneration in an early stage of osteoarthritis (OA) is an important clinical challenge. An early-stage compartmentalized OA model was used to evaluate different biological regeneration techniques.

HYPOTHESIS

Biological regeneration in an early stage of compartmentalized OA is possible.

STUDY DESIGN

Controlled laboratory study.

METHODS

A 7-mm cartilage defect was surgically created in 24 sheep. After 3 months, by which time early OA had set in, the sheep were randomized into 4 different treatment groups and operated for the second time. One group (CONTROL) served as a long-term follow-up group for the further development of OA. The other 3 groups (regeneration groups) each underwent a different regeneration procedure after abrasion of the subchondral bone (defect size: 20 × 10 mm with a depth of 2.5 mm): spongialization alone (SPONGIO), spongialization followed by implantation of an unseeded hyaluronan matrix (MATRIX), or spongialization followed by implantation of a hyaluronan matrix seeded with autologous chondrocytes (MACT). Then, 12 months after the second operative procedure, the animals were euthanized and the defects subjected to macroscopic and histological grading. Historical 4-month data were compared with the 12-month results.

RESULTS

After 12 months of follow-up, advanced cartilage degeneration was observed in the CONTROL group. On the other hand, all regeneration groups improved significantly compared with the 4-month results using the Mankin score. Cartilage quality in the MACT group was significantly better than in the MATRIX group, as determined by the Mankin and the O'Driscoll scores.

CONCLUSION

There are no existing clinical options for preventing early OA from progressing to a severe disease. This study provides important information on how a surgical intervention can forestall the development of OA.

CLINICAL RELEVANCE

OA of the knee is very common. Total joint replacement is not an acceptable option for active patients. Biological regeneration in OA is successful for focal cartilage defects; however, a long-term follow-up for biological regeneration in OA is missing. It is essential to have long-term results for a regenerative procedure involving cartilage, which is a tissue with a very slow turnover.

Clinical outcome after treatment of single and multiple cartilage defects by autologous matrix-induced chondrogenesis

PURPOSE

Characterized cartilage lesions have a distinct impact on postoperative clinical outcome, which is still being evaluated. The purpose of this study was to assess the postoperative clinical outcome of autologous matrix-induced chondrogenesis (AMIC) for characterized cartilage lesions.

METHODS

Fifteen patients with articular cartilage (AC) defects of the knee were included in the study. AC defects were characterized intraoperatively by International Cartilage Repair Society score. Grade III-IV AC lesions were treated with AMIC; grade I-II lesions were left untreated. Patients were divided into subgroups and clinically evaluated by subjective autologous matrix-induced chondrogenesis (IKDC) and Tegner scores at median follow-up of 4.5 years.

RESULTS

Twenty-eight AC defects were diagnosed (1.9/patient). Multiple subgroup had larger diagnosed (7 ± 2.3 cm², p = 0.022) and untreated (3.1 ± 2.3 cm², p = 0.012) lesion areas than the single subgroup. Partly treated subgroup had larger untreated defect areas (3.6±2.3 cm², p = 0.025) than the Treated subgroup. Average subjective IKDC values of total group and individual subgroups improved significantly at follow-up. More patients restored their previous activity levels ( p = 0.026) and had higher incremental subjective IKDC scores ( p = 0.014) in the single subgroup than the multiple subgroup. Diagnosed defect size negatively correlated to subjective IKDC incremental ( r = -0.624, p = 0.023) and postoperative scores ( r = -0.545, p = 0.054) in total group.

CONCLUSIONS

AMIC can have a clinically relevant outcome for patients with single or multiple knee AC lesions; however, clinical outcome is superior in patients with a single defect per knee. Patients with single defects returned to previous physical activity levels significantly faster than patients with multiple defects. Diagnosed AC defect areas negatively correlate to clinical improvement at follow-up.

Editorial Commentary: Autologous Chondrocyte Implantation Versus Microfracture for Knee Articular Cartilage Repair: We Should Focus on the Latest Autologous Chondrocyte Implantation Techniques

The clinical efficacy of autologous chondrocyte implantation (ACI) versus microfracture (MFx) for repair of articular cartilage lesions in the knee has gained significant attention in the orthopaedic sports medicine community in recent years. Bone marrow stimulation with MFx often is considered a first-line treatment option, given the ease and low cost of the procedure, as well as the good short-term outcomes. However, multiple studies have recently shown the outcomes of knee MFx to worsen after 5 years postoperatively, particularly for larger lesions. Because of this, ACI has been proposed as a first-line rather than salvage procedure for focal chondral defects in the knee. Although it is important to understand the differences in clinical outcomes between ACI and MFx at mid-term follow-up, longer-term outcomes need to be further investigated. In addition, it may be more appropriate to focus on the comparison of MFx with newer-generation techniques of chondrocyte implantation matrix-associated ACI rather than a collation of historical 2-step ACI using periosteum and newer techniques.

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.

Osteochondral Autologous Transplantation for Treating Patellar High-Grade Chondral Defects: A Systematic Review

Background:

Patellar cartilage defects account for 34.6% of defects found during routine arthroscopy. These defects pose a challenge in orthopaedic surgery because they have been associated with worse outcomes after surgical repair compared with other chondral lesions within the knee.

Purpose:

To systematically review the literature for evidence on results of osteochondral autologous transplantation (OAT) for the management of isolated patellar cartilage high-grade defects (International Cartilage Repair Society [ICRS] grade 3-4).

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A systematic review of the literature was performed to find studies that addressed outcomes regarding OAT to treat patellar high-grade cartilage defects (ICRS grade 3-4). Studies addressing patient-reported outcomes, return to sports, or magnetic resonance imaging (MRI) at follow-up after isolated OAT procedures for patellar cartilage defects were included.

Results:

A total of 5 studies were included in this review. We were not able to perform a meta-analysis as no studies had available data. A total of 102 patients who received an isolated OAT for a patellar chondral defect were included in these 5 studies. All patients showed significant improvement at final follow-up based on the following patient-reported outcome scores: Lysholm, International Knee Documentation Committee, Kujala, Tegner, and 36-Item Short Form Health Survey. We found that 4 studies used MRI during the first postoperative year to assess osteochondral plug integration and positioning. The results demonstrated that most plugs were integrated and correctly positioned when evaluated at follow-up, conducted on average after 12 months. Whether patients were able to return to sports was queried in 2 of the included studies, revealing that patients could return to their previous level in most cases (Tegner score, 5-9 at 2 years after surgery).

Conclusion:

Results indicate that OAT is a safe and reliable technique to treat patellar high-grade osteochondral defects, allowing for significant improvement in patient-reported outcomes and return to sports.

[Research progress of scaffold materials for tissue engineered meniscus]

Objective

To summarize and analyze the research progress of scaffold materials used in tissue engineered meniscus.

Methods

The classification and bionics design of scaffold materials were summarized by consulting domestic and foreign literature related to the research of tissue engineered meniscus in recent years.

Results

Tissue engineered meniscus scaffolds can be roughly classified into synthetic polymers, hydrogels, extracellular matrix components, and tissue derived materials. These different materials have different characteristics, so the use of a single material has its unique disadvantages, and the use of a variety of materials composite scaffolds can learn from each other, which is a hot research area at present. In addition to material selection, material processing methods are also the focus of research. At the same time, according to the morphological structure and mechanical characteristics of the meniscus, the bionic design of tissue engineered meniscus scaffolds has great potential.

Conclusion

At present, there are many kinds of scaffold materials for tissue engineered meniscus. However, there is no material that can completely simulate the natural meniscus, and further research of scaffold materials is still needed.

High Rate of Failure After Matrix-Assisted Autologous Chondrocyte Transplantation in Osteoarthritic Knees at 15 Years of Follow-up

BACKGROUND

Chondral and osteochondral lesions in osteoarthritic knees of young patients remain challenging for orthopaedic surgeons, due to a combination of high functional demands and limited indications for joint replacement in this population. The possibility of extending the indication of cartilage regenerative procedures to these patients may allow the delay of metal resurfacing.

PURPOSE

To analyze the potential of a cartilage regenerative approach to provide clinical benefits in young patients with osteoarthritic knees, documenting outcomes in terms of clinical improvement as well as failures, in particular regarding knee replacement, at long-term follow-up.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 41 patients (mean ± SD age, 43 ± 9 years) who had cartilage lesions (4 ± 2 cm²) in osteoarthritic knees (Kellgren-Lawrence grade 2 or 3) underwent matrix-assisted autologous chondrocyte transplantation (MACT) as a salvage procedure. Patients were evaluated with International Knee Documentation Committee (IKDC), EuroQol visual analog scale (EQ-VAS), and Tegner scores before surgery; at 1, 2, 5, and 9 years after surgery; and at a final follow-up at a mean of 15 years after surgery (range, 14-18 years). Failures were also recorded.

RESULTS

An improvement was observed in all scores after surgery, but a progressive worsening over time was noted. The mean ± SD IKDC score improved from 38.6 ± 16.2 to a maximum of 66.0 ± 18.6 at 2 years (P < .0005), with a subsequent deterioration until the final evaluation at 56.2 ± 21.7 (P = .024). A similar trend was confirmed by EQ-VAS scores. Tegner scores improved at all follow-up points but did not reach the preinjury level. Patients who underwent combined surgery obtained significantly lower results. Only 13 patients (32%) had an IKDC score higher than 70. During the follow-up period, 21 patients underwent reoperation (18 with knee replacement) and 3 more patients experienced clinical failure, for a total surgical and clinical failure rate of 59% at 15 years.

CONCLUSION

The use of cartilage regenerative surgical procedures, such as MACT, as salvage procedures for young, active patients affected by chondral and osteochondral lesions in osteoarthritic knees led to a limited improvement, with the majority of patients experiencing failure at long-term follow-up. Although a minor subpopulation experienced favorable and stable improvement, the use of MACT for such a challenging indication remains questionable until responding patients can be profiled.

Osteochondral Allograft Transplantation of the Femoral Condyle Utilizing a Thin Plug Graft Technique

BACKGROUND

Previous studies showed clinical benefit and durable results of osteochondral allograft (OCA) transplantation for the treatment of femoral condyle lesions. However, the majority of these studies are difficult to interpret owing to the mixed results of different techniques and anatomic locations.

PURPOSE

To evaluate the outcome of OCA transplantation with thin plug grafts for treatment of isolated femoral condyle osteochondral lesions.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This study included 187 patients (200 knees) who underwent OCA transplantation for isolated osteochondral lesions on the femoral condyle between 1999 and 2014. For all cases, a thin plug technique was used with commercially available surgical instruments and the minimum amount of bone necessary for fixation. Evaluation included International Knee Documentation Committee score, Knee injury and Osteoarthritis Outcome Score, and patient satisfaction. Frequency and type of further surgery were assessed. Failure of the allograft was defined as further surgery involving removal of the allograft.

RESULTS

Mean follow-up was 6.7 years (range, 1.9-16.5 years). The mean age of patients at the time of surgery was 31 years, and 63% were male. The medial femoral condyle was affected in 69% of knees. A single thin plug graft was used in 145 knees (72.5%), and 2 grafts were used in 55 knees (27.5%). Mean allograft area was 6.3 cm², and graft thickness was 6.5 mm (cartilage and bone combined). Further surgery was required for 52 knees (26%), of which 16 (8% of entire cohort) were defined as allograft failures (4 OCA revisions, 1 arthrosurface, 6 unicompartmental knee arthroplasties, and 5 total knee arthroplasties). Median time to failure was 4.9 years. Survivorship of the allograft was 95.6% at 5 years and 91.2% at 10 years. Among patients with grafts remaining in situ at latest follow-up, clinically meaningful improvement in pain, function, and quality of life was reported. Satisfaction was reported by 89% of patients.

CONCLUSION

OCA transplantation with a thin plug graft technique is a valuable procedure for the treatment of femoral condyle osteochondral lesions, resulting in significant improvement in clinical scores, high patient satisfaction, and low reoperation and clinical failure rates.

Emerging therapies for cartilage regeneration in currently excluded 'red knee' populations

The field of articular cartilage repair has made significant advances in recent decades; yet current therapies are generally not evaluated or tested, at the time of pivotal trial, in patients with a variety of common comorbidities. To that end, we systematically reviewed cartilage repair clinical trials to identify common exclusion criteria and reviewed the literature to identify emerging regenerative approaches that are poised to overcome these current exclusion criteria. The term “knee cartilage repair” was searched on clinicaltrials.gov. Of the 60 trials identified on initial search, 33 were further examined to extract exclusion criteria. Criteria excluded by more than half of the trials were identified in order to focus discussion on emerging regenerative strategies that might address these concerns. These criteria included age (<18 or >55 years old), small defects (<1 cm²), large defects (>8 cm²), multiple defect (>2 lesions), BMI >35, meniscectomy (>50%), bilateral knee pathology, ligamentous instability, arthritis, malalignment, prior repair, kissing lesions, neurologic disease of lower extremities, inflammation, infection, endocrine or metabolic disease, drug or alcohol abuse, pregnancy, and history of cancer. Finally, we describe emerging tissue engineering and regenerative approaches that might foster cartilage repair in these challenging environments. The identified criteria exclude a majority of the affected population from treatment, and thus greater focus must be placed on these emerging cartilage regeneration techniques to treat patients with the challenging “red knee”.

Cell-free cartilage repair in large defects of the knee: increased failure rate 5 years after implantation of a collagen type I scaffold

INTRODUCTION

Cartilage defects of the knee remain a challenging problem in orthopedic surgery despite the ongoing improvements in regenerative procedures such as the autologous chondrocyte transplantation. Due to the lack of donor-site morbidity and the single-stage procedure cell-free scaffolds are an interesting alternative to cell-based procedures. But as currently mid- and long-term data are lacking, the aim of the present study was to present mid-term clinical, radiological and histological results of a cell-free collagen type I scaffolds for cartilage repair.

MATERIALS AND METHODS

Twenty-eight patients were followed prospectively. Clinical evaluation using patient-reported outcome measures (KOOS, IKDC; VAS for pain, Tegner score for activity) as well as radiologic evaluation of the repair tissue (MOCART) was performed at 1 year, 2 years and 5 years. Histologic evaluation of the repair tissue was done in case of revision surgery using the ICRS II score for human cartilage repair.

RESULTS

In these large cartilage defects with a mean defect size of 3.7 ± 1.9 cm², clinical failure necessitating revision surgery was seen in 5 of 28 patients (18%). While the remaining patients showed good-to-excellent clinical results (KOOS, IKDC, VAS, Tegner), the radiologic appearance of the repair tissue showed a reduction of the MOCART score between the 2- and 5-year follow-up. Histologic evaluation of the repair tissue showed a cartilage-like appearance with no signs of inflammation or cell death but an overall medium tissue quality according to the ICRS II Score.

CONCLUSION

The use of this cell-free collagen type I scaffold for large defects showed increased wear of the repair tissue and clinical failure in 18% of cases at 5-year follow-up.

Polysaccharide Based Scaffolds for Soft Tissue Engineering Applications

Soft tissue reconstructs require materials that form three-dimensional (3-D) structures supportive to cell proliferation and regenerative processes. Polysaccharides, due to their hydrophilicity, biocompatibility, biodegradability, abundance, and presence of derivatizable functional groups, are distinctive scaffold materials. Superior mechanical properties, physiological signaling, and tunable tissue response have been achieved through chemical modification of polysaccharides. Moreover, an appropriate formulation strategy enables spatial placement of the scaffold to a targeted site. With the advent of newer technologies, these preparations can be tailor-made for responding to alterations in temperature, pH, or other physiological stimuli. In this review, we discuss the developmental and biological aspects of scaffolds prepared from four polysaccharides, viz. alginic acid (ALG), chitosan (CHI), hyaluronic acid (HA), and dextran (DEX). Clinical studies on these scaffolds are also discussed.

Chasing Chimeras - The elusive stable chondrogenic phenotype

The choice of the best-suited cell population for the regeneration of damaged or diseased cartilage depends on the effectiveness of culture conditions (e.g. media supplements, three-dimensional scaffolds, mechanical stimulation, oxygen tension, co-culture systems) to induce stable chondrogenic phenotype. Herein, advances and shortfalls in in vitro, preclinical and clinical setting of various in vitro microenvironment modulators on maintaining chondrocyte phenotype or directing stem cells towards chondrogenic lineage are critically discussed. Chondrocytes possess low isolation efficiency, limited proliferative potential and rapid phenotypic drift in culture. Mesenchymal stem cells are relatively readily available, possess high proliferation potential, exhibit great chondrogenic differentiation capacity, but they tend to acquire a hypertrophic phenotype when exposed to chondrogenic stimuli. Embryonic and induced pluripotent stem cells, despite their promising in vitro and preclinical data, are still under-investigated. Although a stable chondrogenic phenotype remains elusive, recent advances in in vitro microenvironment modulators are likely to develop clinically- and commercially-relevant therapies in the years to come.

Microfracture Versus Autologous Chondrocyte Implantation for Articular Cartilage Lesions in the Knee: A Systematic Review of 5-Year Outcomes

BACKGROUND

Microfracture (MFx) and autologous chondrocyte implantation (ACI) are 2 surgical treatment options used to treat articular cartilage injuries of the knee joint.

PURPOSE

To compare the midterm to long-term clinical outcomes of MFx versus ACI for focal chondral defects of the knee.

STUDY DESIGN

Systematic review.

METHODS

A systematic review was performed by searching PubMed, the Cochrane Library, and Embase to locate studies (level of evidence I-III) comparing the minimum average 5-year clinical outcomes of patients undergoing MFx versus ACI. Search terms used were "knee," "microfracture," "autologous chondrocyte implantation," and "autologous chondrocyte transplantation." Patients were evaluated based on treatment failure rates, magnetic resonance imaging, and patient-reported outcome scores (Lysholm, Knee Injury and Osteoarthritis Outcome Score [KOOS], and Tegner scores).

RESULTS

Five studies (3 level I evidence, 2 level II evidence) were identified that met the inclusion criteria, including a total of 210 patients (211 lesions) undergoing MFx and 189 patients (189 lesions) undergoing ACI. The average follow-up among all studies was 7.0 years. Four studies utilized first-generation, periosteum-based ACI (P-ACI), and 1 study utilized third-generation, matrix-associated ACI (M-ACI). Treatment failure occurred in 18.5% of patients undergoing ACI and 17.1% of patients undergoing MFx ( P = .70). Lysholm and KOOS scores were found to improve for both groups across studies, without a significant difference in improvement between the groups. The only significant difference in patient-reported outcome scores was found in the 1 study using M-ACI in which Tegner scores improved to a significantly greater extent in the ACI group compared with the MFx group ( P = .003).

CONCLUSION

Patients undergoing MFx or first/third-generation ACI for articular cartilage lesions in the knee can be expected to experience improvement in clinical outcomes at midterm to long-term follow-up without any significant difference between the groups.

Current concepts in treatment of early knee osteoarthritis and osteochondral lesions; the role of biological augmentations

Early knee osteoarthritis and chondral lesions are a common cause of disability in younger patients. Surgical options, such as microfractures, ACI and OAT, provide good, but not fully satisfying, outcomes. Recent advance in biological knowledge introduced two different methodological approaches of delivering growth factors and stem cells into the articular environment. Platelet-Rich Plasma and Mesenchimal Stem Cells are supposed to change the way to approach early knee osteoarthritis and chondral lesions, though their indications and limits are yet to be determined.

Current concepts in treatment of early knee osteoarthritis and osteochondral lesions; the role of biological augmentations

Early knee osteoarthritis and chondral lesions are a common cause of disability in younger patients. Surgical options, such as microfractures, ACI and OAT, provide good, but not fully satisfying, outcomes. Recent advance in biological knowledge introduced two different methodological approaches of delivering growth factors and stem cells into the articular environment. Platelet-Rich Plasma and Mesenchimal Stem Cells are supposed to change the way to approach early knee osteoarthritis and chondral lesions, though their indications and limits are yet to be determined.

Functional outcomes after patellar autologous osteochondral transplantation

PURPOSE

The aim of the present study was to assess clinical evaluation of patients who underwent autologous osteochondral transplantation of the patella.

METHODS

This prospective study assessed outcomes of 20 patients who underwent patellar autologous osteochondral transplantation at four time-points: preoperatively, 3 days, 6 months, and 2 years after surgery. The following outcomes were assessed at each time-point: pain (VAS), gait, swelling, trophic status, muscle strength, patellar mobility, and range of motion. The Tegner scale was also applied for each time-point.

RESULTS

All parameters improved, except for patellar mobility, which did not show any change. Pain score decreased from 7.1 (SD 2.3) to 2.4 (SD 2.6) at the 2-year assessment; limping decreased from 70 % before surgery to 15 % 2 years later; swelling scores decreased from an average of 1.8 (SD 0.8) 3 days after surgery to 0.5 (SD 0.7) at the 2-year assessment; muscle strength increased from 3.9 (SD 0.8) to 4.7 (SD 0.7) points at final follow-up; and the range of motion increased from 84 (SD 16.2) to 132 (SD 10.7) degrees 2 years later. Tegner score before surgery ranged from 0 to 5, and after 2 years, it ranged from 5 to 9.

CONCLUSION

Autologous osteochondral transplantation for the treatment of patellar chondral lesion was associated with significant improvement in pain, gait, swelling, and range of motion 2 years after surgery, achieving scores similar to uninjured knees. Most of them were able to return to sports activity after 6 months (recreational level) and 2 years (competitive level).

LEVEL OF EVIDENCE

IV.

Synthetic Poly(Vinylalcohol)-Based Membranes for Cartilage Surgery and Repair

Cell-based therapies for cartilage repair are continually being developed to treat osteoarthritis. The cells are either introduced directly by intra-articular injection or via a cell-seeded matrix scaffold. Here, poly(vinylalcohol)-based membranes are developed to be used for mesenchymal stem cell implantation in cartilage repair procedures, having controllable physicochemical properties such as porosity, mechanical strength, and permeability, and a unique self-sealing property. The membranes possess a bilayer structure with a less porous layer providing mechanical strength and selective permeability, exhibit an elastic modulus of between 0.3 and 0.9 MPa, and are permeable to molecules <40 kDa, which is in the range of cartilage permeability. Three different peptide ligands with the sequences Ac-GCGYGRGDSPG, Ac-GCG(OPG)4REGOFG(OPG)4, and Ac-GCG(OPG)7, respectively, are conjugated to the membranes and subject to in vitro cell adhesion and differentiation assays. Col I/Col II gene expression ratios indicated that the collagen-mimetic peptide, Ac-GCG(OPG)7, best supported mesenchymal stem cell differentiation into the chondrogenic lineage. Although low retention of the membrane is observed in vivo in a rabbit knee model, results suggest that the membrane was able to facilitate mesenchymal stem cell implantation and differentiation to chondrocytes. These PVA-based membranes provide a feasible, synthetic, off-the-shelf material for the delivery of stem cells, and can be modified for other surgical applications.

Age Is Not a Contraindication for Cartilage Surgery: A Critical Analysis of Standardized Outcomes at Long-term Follow-up

BACKGROUND

Age is commonly accepted as a negative prognostic factor in cartilage surgery, and cutoff values of 30 to 40 years have been previously suggested as treatment indication. However, the lower outcome scores documented in older patients do not take in consideration the decreasing requirements of an aging joint.

PURPOSE

To analyze the real effect of age in terms of recovery with respect to the functional level expected for different age categories of patients treated for cartilage lesions.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients with International Cartilage Repair Society (ICRS) grade 3-4 defects, involving femoral condyles or trochlea without osteoarthritis, were treated with arthroscopic matrix-assisted autologous chondrocyte transplantation; 157 patients were evaluated with IKDC subjective and Tegner scores before surgery and then after 2 and 10 years. Results were first evaluated by dividing patients into 2 age groups according to the generally approved cutoff value of 40 years. The analysis was then repeated after the scores of each patient were standardized according to the score achievable per the normative data in healthy patients for the corresponding sex and age category.

RESULTS

A significant improvement in all scores was observed. IKDC subjective score improved from 38.9 ± 14.5 to 74.7 ± 21.8 at 10 years. When a cutoff value of 40 years was used, older patients reached a significantly worse IKDC subjective value at 10 years (65.8 ± 24.3 vs 77.2 ± 20.4, P = .007). However, different findings were obtained after the scores were standardized. Although optimal results were still found in younger patients (<30 years), patients older than 40 years also appeared to benefit from the treatment, and no significant differences were noted compared with the younger population.

CONCLUSION

The benefit of cartilage treatments in patients with increasing age but without any sign of osteoarthritis was higher than previously reported in literature. In fact, when the decreasing functional level expected by an aging population was considered, standardized results showed an overall benefit after cartilage treatment in patients older than 40 years that was not significantly different from the outcome achieved in younger patients. Thus, age is not a strict contraindication as previously suggested, and future studies should consider standardization of data to prove the real age limit of cartilage treatments.

Terapias Celulares y Productos de Ingeniería de Tejidos para el Tratamiento de Lesiones Condrales de Rodilla

El cartílago articular es un tejido vulnerable a las lesiones de diferente etiología; siendo uno de los más afectados,  el cartílago de la rodilla. Aunque la mayoría de los tratamientos convencionales reducen los síntomas, generalmente conducen a la formación de fibrocartílago; el cual, posee características diferentes a las del cartílago hialino de las articulaciones.  Son pocas las aproximaciones terapéuticas que promueven el  reemplazo del tejido dañado por cartílago hialino funcional; las más exitosas son las denominadas terapias avanzadas, que aplican células y  productos de ingeniería de tejidos con el fin de estimular la regeneración del cartílago. La mayoría de ellas se basan en colocar soportes  hechos con biomateriales de diferente origen, que sembrados o no con células exógenas o endógenas, reemplazan al cartílago dañado y promueven su regeneración. Este  trabajo revisa algunas de las aproximaciones terapéuticas enfocadas en la regeneración del cartílago articular de rodilla; así como, los biomateriales más empleados en la elaboración de soportes para terapia celular e ingeniería de tejido cartilaginoso.

Failure of Autologous Chondrocyte Implantation

Long-term results of autologous chondrocyte implantation and matrix-assisted autologous chondrocyte transplantation in the knee are satisfying, but not enough attention has been paid to the evaluation of failures. Thus, a systematic review of the literature was performed, underlining a failure rate in the 58 included articles of 14.9% among 4294 patients, most of them occurring in the first 5 years after surgery, and with no difference between autologous chondrocyte implantation and matrix-assisted autologous chondrocyte transplantation. Failures are very heterogenously defined in the current literature. A widely accepted definition is needed, and a comprehensive definition taking into consideration the patient's perception of the outcome, not just the surgeon's or researcher's point of view, would be advisable. Finally, there is no agreement on the most appropriate treatment of failures, and further studies are needed to give better indications to properly manage patients failed after cartilage procedures.

LEVEL OF EVIDENCE

Level IV.

The Good the Bad and the Ugly of Glycosaminoglycans in Tissue Engineering Applications

High sulfation, low cost, and the status of heparin as an already FDA- and EMA- approved product, mean that its inclusion in tissue engineering (TE) strategies is becoming increasingly popular. However, the use of heparin may represent a naïve approach. This is because tissue formation is a highly orchestrated process, involving the temporal expression of numerous growth factors and complex signaling networks. While heparin may enhance the retention and activity of certain growth factors under particular conditions, its binding 'promiscuity' means that it may also inhibit other factors that, for example, play an important role in tissue maintenance and repair. Within this review we focus on articular cartilage, highlighting the complexities and highly regulated processes that are involved in its formation, and the challenges that exist in trying to effectively engineer this tissue. Here we discuss the opportunities that glycosaminoglycans (GAGs) may provide in advancing this important area of regenerative medicine, placing emphasis on the need to move away from the common use of heparin, and instead focus research towards the utility of specific GAG preparations that are able to modulate the activity of growth factors in a more controlled and defined manner, with less off-target effects.

Matrix-Assisted Autologous Chondrocyte Transplantation in the Knee: A Systematic Review of Mid- to Long-Term Clinical Outcomes

Background:

Matrix-assisted autologous chondrocyte transplantation (MACT) is a surgical treatment option for articular cartilage lesions of the knee joint.

Purpose:

To investigate mid- to long-term clinical outcomes of MACT in the patellofemoral (PF) and tibiofemoral (TF) joints.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A systematic review was performed by searching PubMed, Embase, and the Cochrane Library to find studies evaluating minimum 5-year clinical outcomes of patients undergoing MACT in the knee joint. Search terms used were knee, matrix, and autologous chondrocyte. Patients were evaluated based on treatment failure rates, magnetic resonance imaging, and subjective outcome scores. Study methodology was assessed using the Modified Coleman Methodology Score (MCMS).

Results:

Ten studies (two level 1, one level 2, one level 3, and six level 4 evidence) were identified that met inclusion and exclusion criteria, for a total of 442 TF patients and 136 PF patients. Treatment failure occurred in 9.7% of all patients, including 4.7% of PF patients and 12.4% of TF patients (P = .037). Weighted averages of subjective outcome scores, including Knee injury and Osteoarthritis Outcome Score, Short Form–36 Health Survey, and Tegner scores, improved from baseline to latest follow-up in both TF and PF patients. The mean MCMS was found to be 57.4, with a standard deviation of 18.5.

Conclusion:

Patients undergoing MACT in the knee show favorable mid- to long-term clinical outcomes. A significantly higher treatment failure rate was found in patients undergoing MACT in the TF joint compared with the PF joint.

Repair Potential of Matrix-Induced Bone Marrow Aspirate Concentrate and Matrix-Induced Autologous Chondrocyte Implantation for Talar Osteochondral Repair: Patterns of Some Catabolic, Inflammatory, and Pain Mediators

OBJECTIVE

The low regenerative potential of cartilage contributed to the development of different cell therapies aimed to improve the clinical outcome in young patients with Osteochondral Lesions of the Talus (OLT). This study is designed to assess the regenerative potential of autologous matrix-induced Bone Marrow Aspirate Concentrate (mBMAC) and matrix-induced Autologous Chondrocyte Implantation (mACI) evaluating, on a small number of osteochondral biopsies, the expression of some catabolic, inflammatory, and pain mediators.

DESIGN

Twenty-two patients with OLT were analyzed in this study; 7 were treated with mACI and 15 with mBMAC. Informed consent was obtained from all the patients. Clinical assessments were performed pre-operatively and at 12, 24, and 36 months after surgery using the American Orthopedic Foot and Ankle Society (AOFAS). Histology and immunohistochemistry were used to assess cartilage repair at 24 months. Data were analyzed using non-parametric Wilcoxon-Mann-Whitney and Spearman tests.

RESULTS

A remarkable improvement in AOFAS score was noticed for both treatments up to 36 months; however, patients treated with mACI reported the best AOFAS score. Various degrees of tissue remodeling were observed by histological analysis for both cell strategies. However, mBMAC treatment showed a higher expression of some fibrous and hypertrophic markers compared to mACI group. A mild positivity for nerve growth factor, as pain mediator, was noticed for both treatments.M.

CONCLUSIONS

Our findings demonstrated the best histological and clinical results following mACI treatment since different fibrotic and hypertrophic features were evident in the mBMAC group at 24-month follow-up.

Cartilage repair in the degenerative ageing knee

Background and purpose - Cartilage damage can develop due to trauma, resulting in focal chondral or osteochondral defects, or as more diffuse loss of cartilage in a generalized organ disease such as osteoarthritis. A loss of cartilage function and quality is also seen with increasing age. There is a spectrum of diseases ranging from focal cartilage defects with healthy surrounding cartilage to focal lesions in degenerative cartilage, to multiple and diffuse lesions in osteoarthritic cartilage. At the recent Aarhus Regenerative Orthopaedics Symposium (AROS) 2015, regenerative challenges in an ageing population were discussed by clinicians and basic scientists. A group of clinicians was given the task of discussing the role of tissue engineering in the treatment of degenerative cartilage lesions in ageing patients. We present the outcomes of our discussions on current treatment options for such lesions, with particular emphasis on different biological repair techniques and their supporting level of evidence. Results and interpretation - Based on the studies on treatment of degenerative lesions and early OA, there is low-level evidence to suggest that cartilage repair is a possible treatment for such lesions, but there are conflicting results regarding the effect of advanced age on the outcome. We concluded that further improvements are needed for direct repair of focal, purely traumatic defects before we can routinely use such repair techniques for the more challenging degenerative lesions. Furthermore, we need to identify trigger mechanisms that start generalized loss of cartilage matrix, and induce subchondral bone changes and concomitant synovial pathology, to maximize our treatment methods for biological repair in degenerative ageing joints.

A Randomized Multicenter Trial Comparing Autologous Chondrocyte Implantation with Microfracture: Long-Term Follow-up at 14 to 15 Years

BACKGROUND

The management of cartilage and osteochondral lesions in the knee remains problematic and controversial. Our group reported the 2-year and 5-year results of a randomized controlled trial comparing autologous chondrocyte implantation (ACI) and microfracture in patients with focal femoral cartilage injuries. The objective of the present study was to report the long-term results.

METHODS

Eighty patients with a single symptomatic chronic cartilage defect on the femoral condyle without general osteoarthritis were included in the study at the time of the index operation (January 1999 to February 2000). We used the International Cartilage Repair Society (ICRS), Lysholm, Short Form-36 (SF-36), and Tegner forms to collect data at the time of inclusion and at follow-up evaluations. Standing weight-bearing radiographs were evaluated for evidence of osteoarthritis according to the method described by Kellgren and Lawrence. For the long-term follow-up in 2014, we used the Synaflexer frame to standardize the radiographs. The operation was considered to have failed if a reoperation was performed because of symptoms from a lack of healing of the treated defect.

RESULTS

At the long-term follow-up evaluation, no significant differences between the treatment groups were detected with respect to the results on the clinical scoring systems. At the 15-year evaluation, there were 17 failures in the ACI group compared with 13 in the microfracture group. We observed that more total knee replacements were needed in the ACI group than in the microfracture group (6 compared with 3). The surviving patients in both groups, i.e., those who had not had a failure, had significant improvement in the clinical scores compared with baseline. Fifty-seven percent of the surviving patients in the ACI group and 48% of such patients in the microfracture group had radiographic evidence of early osteoarthritis (a Kellgren and Lawrence grade of ≥2); the difference was not significant.

CONCLUSIONS

The survivors in both groups improved their clinical scores in the short, medium, and long-term evaluations, and no significant difference between the groups was found at the long-term follow-up. The risk of treatment failure and the frequency of radiographic osteoarthritis are problematic. Our findings raise serious concerns regarding the efficacy of these procedures in delaying osteoarthritis and preventing further surgery. Continued basic and clinical research is needed in this field.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Cell-based tissue engineering strategies used in the clinical repair of articular cartilage

One of the most important issues facing cartilage tissue engineering is the inability to move technologies into the clinic. Despite the multitude of current research in the field, it is known that 90% of new drugs that advance past animal studies fail clinical trials. The objective of this review is to provide readers with an understanding of the scientific details of tissue engineered cartilage products that have demonstrated a certain level of efficacy in humans, so that newer technologies may be developed upon this foundation. Compared to existing treatments, such as microfracture or autologous chondrocyte implantation, a tissue engineered product can potentially provide more consistent clinical results in forming hyaline repair tissue and in filling the entirety of the defect. The various tissue engineering strategies (e.g., cell expansion, scaffold material, media formulations, biomimetic stimuli, etc.) used in forming these products, as collected from published literature, company websites, and relevant patents, are critically discussed. The authors note that many details about these products remain proprietary, not all information is made public, and that advancements to the products are continuously made. Nevertheless, by understanding the design and production processes of these emerging technologies, one can gain tremendous insight into how to best use them and also how to design the next generation of tissue engineered cartilage products.

Cell-based tissue engineering strategies used in the clinical repair of articular cartilage

One of the most important issues facing cartilage tissue engineering is the inability to move technologies into the clinic. Despite the multitude of current research in the field, it is known that 90% of new drugs that advance past animal studies fail clinical trials. The objective of this review is to provide readers with an understanding of the scientific details of tissue engineered cartilage products that have demonstrated a certain level of efficacy in humans, so that newer technologies may be developed upon this foundation. Compared to existing treatments, such as microfracture or autologous chondrocyte implantation, a tissue engineered product can potentially provide more consistent clinical results in forming hyaline repair tissue and in filling the entirety of the defect. The various tissue engineering strategies (e.g., cell expansion, scaffold material, media formulations, biomimetic stimuli, etc.) used in forming these products, as collected from published literature, company websites, and relevant patents, are critically discussed. The authors note that many details about these products remain proprietary, not all information is made public, and that advancements to the products are continuously made. Nevertheless, by understanding the design and production processes of these emerging technologies, one can gain tremendous insight into how to best use them and also how to design the next generation of tissue engineered cartilage products.

Long-term Results After Hyaluronan-based MACT for the Treatment of Cartilage Lesions of the Patellofemoral Joint

BACKGROUND

Cartilage lesions of the patellofemoral joint are a challenging condition. Hyaluronan-based matrix-assisted autologous chondrocyte transplantation (MACT) has been shown to offer a significant improvement in the short term but has a tendency to worsen at midterm follow-up.

HYPOTHESIS

Patients treated with MACT for lesions of the articular surface of the patellofemoral joint will present further clinical worsening at long-term follow-up.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Thirty-two patients with full-thickness chondral lesions in the patellofemoral joint were treated with hyaluronan-based MACT and were prospectively evaluated preoperatively and at 2-, 5-, and 10-year follow-up. The mean defect size was 4.45 cm(2). There were 20 lesions located on the patella and 8 on the trochlea, and 4 patients had multiple lesions: 3 with patellar and trochlear lesions and 1 with patellar and lateral femoral condyle lesions. Results were evaluated using International Knee Documentation Committee (IKDC) subjective scores, EuroQol visual analog scale (EQ VAS) scores, and Tegner scores. Surgical and clinical failures were documented.

RESULTS

All scores showed a statistically significant improvement at 2-, 5-, and 10-year follow-up with respect to the preoperative level. No worsening was observed at the last follow-up, and results were stable up to 10 years. The improvement in mean (±SD) outcome scores from preoperatively to 2-, 5-, and 10-year follow-up was as follows: IKDC, from 46.0 ± 19.8 to 77.1 ± 17.4, 72.0 ± 20.4, and 78.6 ± 16.4, respectively; Tegner, from 2.5 ± 1.4 to 4.7 ± 1.8, 4.7 ± 1.6, and 4.4 ± 1.5, respectively; and EQ VAS, from 56.9 ± 18.4 to 81.7 ± 13.2, 79.2 ± 17.9, and 78.9 ± 1.7, respectively. Four patients did not achieve significant clinical improvement, and 1 of these patients required further surgical treatment. All failures were female patients with patellar defects, and 3 of them had degenerative lesions and underwent a previous or combined realignment procedure.

CONCLUSION

The clinical results of hyaluronan-based MACT treatment of chondral lesions of the patellofemoral joint do not worsen over time but remain stable and show a low rate of failure at long-term follow-up.

Evaluation of an injectable thermoresponsive hyaluronan hydrogel in a rabbit osteochondral defect model

Articular cartilage displays very little self-healing capabilities, generating a major clinical need. Here, we introduce a thermoresponsive hyaluronan hydrogel for cartilage repair obtained by covalently grafting poly(N-isopropylacrylamide) to hyaluronan, to give a brush co-polymer HpN. The gel is fluid at room temperature and becomes gel at body temperature. In this pilot study HpN safety and repair response were evaluated in an osteochondral defect model in rabbit. Follow-up was of 1 week and 12 weeks and the empty defect served as a control, for a total of four experimental groups. At 12 weeks the defect sites were evaluated macroscopically and histologically. Local lymph nodes, spleen, liver, and kidneys were analyzed for histopathological evaluation. HpN could be easily injected and remained into the defect throughout the study. The macroscopic score was statistically superior for HpN versus empty. Histological score gave opposite trend but not statistically significant. A slight tissue reaction was observed around HpN, however, vascularization and subchondral bone formation were not impeded. An upper proteoglycans rich fibro-cartilaginous tissue with fairly good continuity and lateral integration into the existing articular cartilage was observed in all cases. No signs of local or systemic acute or subacute toxicity were observed. In conclusion, HpN is easily injectable, remains into an osteochondral defect within a moving synovial joint, is biocompatible and does not interfere with the intrinsic healing response of osteochondral defects in a rabbit model. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1469-1478, 2016.

Failures and Reoperations After Matrix-Assisted Cartilage Repair of the Knee: A Systematic Review

PURPOSE

To quantify the reported failures and reoperations for the emerging technique of matrix-assisted cartilage repair at short-term and midterm follow-up.

METHODS

We conducted a systematic review of 3 databases from March 2004 to February 2014 using keywords important for articular cartilage repair. Two authors reviewed the articles, the study exclusion criteria were applied, and articles were determined to be relevant (or not) to the research question. All studies with a minimum of 2 years' clinical follow-up were reviewed for all reported reoperations. The reasons for reoperations were recorded.

RESULTS

We reviewed 66 articles from the 301 articles identified in the original systematic search. There were 60 articles on matrix-assisted cartilage transplantation and 6 articles on matrix-induced chondrogenesis. The matrix-assisted cartilage transplantation studies reported on a total of 1,380 patients at 2 to 5 years' follow-up. Among these, there were 72 reoperations (5%) including 46 treatment failures (3%). These numbers increased to an 11% reoperation rate and 9% treatment failure rate at minimum 5-year follow-up of 961 patients. The most common procedures performed other than revision cartilage surgery or arthroplasty were manipulation under anesthesia for arthrofibrosis (0.7%) and debridement for graft hypertrophy (1.2%). The matrix-induced chondrogenesis studies reported on 163 patients. Among these, there were 15 reoperations (9%) that included 4 treatment failures (2%), 9 manipulations under anesthesia (6%), and 2 debridements for graft hypertrophy (1%).

CONCLUSIONS

Treatment failure rates for matrix-assisted cartilage repair increase from short-term to midterm follow-up, with 11% of patients having undergone further surgery at a minimum of 5 years' follow-up. These data can be used to counsel patients on the potential need for further operative intervention after this emerging cartilage repair technique.