Articular cartilage repair in the adolescent athlete: is autologous chondrocyte implantation the answer?

Favourable clinical outcomes and low revision rate after M-ACI in adolescents with immature cartilage compared to adult controls: Results at 10 years

PURPOSE

The purpose of this study was to evaluate long-term survival, patient-reported outcomes (PROs) and radiographic results of matrix-associated autologous chondrocyte implantation (M-ACI) in adolescents with immature cartilage and compare them to adult controls.

METHODS

A retrospective matched-pair analysis was performed comparing the PRO after M-ACI for focal cartilage defect of the knee in cartilaginous immature adolescents to mature adults. Groups were matched for sex, body mass index, defect site and size, symptom duration and the number of previous knee surgeries. Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART 2.0) scores were assessed at least 60 months postoperatively. Patient acceptable symptomatic state (PASS) and clinical response rate in KOOS and KOOS subscores were calculated.

RESULTS

A total of 54 patients were matched. At a mean of 96 months (65-144 months), no surgical complications, graft hypertrophy or reoperations were noted in the cohorts studied. Adolescents showed superior PROs at the final follow-up (76.9 ± 14.1 vs. 66.4 ± 15.0, p = 0.03) and were significantly more likely to achieve PASS (74.1% vs. 55.6%; p = 0.02) compared to the adult cohort. The KOOS subscale analysis showed long-term benefits for adolescents in terms of symptom improvement, pain reduction, activities of daily living, sports and quality of life (p < 0.05). None of the patients in the adolescent group showed graft hypertrophy on magnet resonance imaging or signs of osteoarthritis on radiographs at long-term follow-ups.

CONCLUSIONS

M-ACI is an effective treatment for chondral defects of the knee in patients with immature cartilage with low revision rates and high patient satisfaction over the long term. Adolescents showed comparable clinical and radiographic results in the short and medium term, with slightly more favourable, clinically relevant functional results in adolescents in the long term. M-ACI can be safely used in adolescents, and consideration should be given to expanding the indication to include these patients.

LEVEL OF EVIDENCE

Level III.

Autologous chondrocyte implantation in the knee is effective in skeletally immature patients: a systematic review

PURPOSE

This systematic review evaluated the efficacy and safety of autologous chondrocyte implantation (ACI) for chondral defects of the knee in skeletally immature patients. Current available data from patients reported outcome measures (PROMs) and complications were collected, analyzed, and discussed.

METHODS

This systematic review was conducted according to the PRISMA guidelines. The following databases were accessed in May 2022: PubMed, Google scholar, Embase, and Scopus. All the clinical studies investigating the efficacy of ACI to manage chondral defects of the knee in skeletally immature patients were accessed. Articles treating patients with surgical procedures other than ACI were not eligible, nor were studies with a follow-up shorter than 12 months.

RESULTS

Data from 9 studies (251 procedures) were collected. 32% (80 of 251) of patients were females. The mean length of follow-up was 44.2 ± 29.4 (range, 12-115) months. The mean age of the patients was 16.4 ± 0.7 (range, 15-17) years. The Knee injury and Osteoarthritis Outcome Score (KOOS) and International Knee Document Committee (IKDC) increased of + 41.9/100 (P = 0.003) and + 33.2/100 (P =  < 0.0001) points, respectively. The Lysholm Knee Score improved of + 20.6/100 (P = 0.02) points. The Visual Analogue Scale (VAS) for pain reduced of - 3.6/10 (P = 0.004) points. The Tegner scale did not show any statistically significant improvement from baseline to follow-up (P = n.s.). The rate of graft hypertrophy was 12.5% (5 of 40 patients), and the rate of failure 5.6% (8 of 142 patients).

CONCLUSION

ACI for chondral defects of the knee is effective to improve PROMs in skeletally immature patients. The safety profile of ACI still remains controversial.

LEVEL OF EVIDENCE

III.

Surgical Fixation of Chondral-Only Fragments of the Knee: A Case Series With a Mean 4-Year Follow-up

Background:

Chondral-only fragments of the knee have traditionally been treated with excision, with or without cartilage restoration procedures. This is because of the historical assumption that cartilage has limited ability to heal to cancellous or subchondral bone. There is now a growing body of evidence supporting surgical fixation of these fragments.

Hypothesis:

We hypothesized that surgical fixation of chondral fragments would result in acceptable rates of healing with improvement in clinical outcome scores.

Study Design:

Case series; Level of evidence, 4.

Methods:

Data were collected on 15 surgically fixed chondral-only fragments in 14 patients. We retrospectively collected participant demographic information, lesion characteristics, primary mechanism (osteochondritis dissecans vs traumatic shear injury), fixation methods, reoperation information, second-look arthroscopic information, and clinical outcome scores. The mean clinical follow-up was 3.96 years, with a minimum of 1-year follow-up. All patients underwent follow-up magnetic resonance imaging at a mean of 2 years after the index procedure.

Results:

The mean age of our cohort was 17.7 years. We found an 80% survival rate for fixation of the fragments at a mean 4-year follow-up. There were statistically significant improvements in postoperative Knee injury and Osteoarthritis Outcome Score and Tegner scores compared with preoperative scores. Follow-up magnetic resonance imaging scans showed complete healing in 10 knees, partial healing in 2 knees, and loss of fixation in 3 knees. Second-look arthroscopic surgery of 3 knees for reasons other than fragment symptoms showed healing of the fragment, while arthroscopic surgery of 3 symptomatic knees showed loss of fixation.

Conclusion:

Surgical fixation of chondral-only lesions showed an 80% success rate with improvements in the KOOS and Tegner scores.

Osteochondral Autograft Transplantation for Hand and Wrist Articular Problems

Management of hand and wrist avascular necrosis with osteochondral fragmentation or focal arthritis can be a challenging problem with a variety procedures described for its treatment. Osteochondral autograft transplantation systems have been utilized in various focal defects of the knee, ankle, elbow, and wrist. The same principle for the treatment of focal defects of the proximal scaphoid, proximal capitate as well as metacarpal head as an alternative treatment is described. The main indication for this treatment is to address focal or partial osteochondral defects where the size of the defect is smaller than the isthmus of the involved bone to accommodate a cylindrical osteochondral graft that can be press fit. Larger and complete defects are contraindications to this treatment. We discuss the surgical technique as well as its main indications and expected outcomes.

Fixation of Traumatic Chondral-Only Fragments of the Knee in Pediatric and Adolescent Athletes: A Retrospective Multicenter Report

Background:

While traditional biological principles have suggested that fragments consisting of cartilage alone cannot be reaffixed to bone with expectable long-term healing, case reports of successful healing after fixation in younger patients indicate that this concept remains incompletely explored.

Purpose:

To evaluate the presenting features, techniques, healing rates, and clinical and radiological results in a cohort of pediatric and adolescent athletes who underwent fixation of traumatic chondral-only fragments in the knee.

Study Design:

Case series; Level of evidence, 4.

Methods:

Patient registries at 2 tertiary care children’s hospitals were reviewed to identify patients ≤18 years old who underwent fixation of a “chondral-only” fragment in the knee, defined as the inability to visualize the fragment on injury radiographs or discern bone on the articular portion of a fragment intraoperatively. The mechanism of injury, fragment features, fixation technique, and postoperative clinical course, including timing of sports clearance, healing on postoperative magnetic resonance imaging (MRI), and any complications or reoperations, were assessed.

Results:

Fifteen patients with a median age at surgery of 12.7 years (interquartile range [IQR], 11.7-14.2 years) and median follow-up of 12.0 months (IQR, 6.0-19.2 months) were analyzed. All patients sustained an acute knee injury before surgery. The injured sites, as assessed on MRI, were the patella (n = 6), trochlea (n = 5), and lateral femoral condyle (n = 4). The median fragment surface area was 492.0 mm² (IQR, 400.0-787.5 mm²). Fixation with bioabsorbable implants was performed in all patients at a median of 1.6 weeks (IQR, 1.0-2.6 weeks) after the injury. One patient (7%) sustained a fall 8 weeks postoperatively, requiring secondary surgery for excision of a dislodged fragment, and 1 patient (7%) underwent unrelated patellar stabilization surgery 3.4 years postoperatively, at which time the fragment was found to be stable. MRI was performed in 9 of 14 patients with retained fragments (median, 12.0 months postoperatively), with 5 patients (56%) showing restoration of the cartilage contour and the resolution of subchondral edema; 2 patients showed thinning but intact cartilage, 1 had cartilage thickening, and 1 had subchondral edema, fissuring, and cystic changes. The median time to return to sports for all 15 patients was 26.0 weeks (IQR, 22.8-40.9 weeks), including 2 patients who required second surgery and returned to sports at 26.1 and 191.1 weeks.

Conclusion:

Fixation of traumatic chondral-only fragments using bioabsorbable implants may result in successful short-term healing in the majority of pediatric and adolescent athletes.

Arthroscopic Transplantation of Osteochondral Autograft for Treatment of Cartilage Defects in the Wrist

Focal chondral lesions are a common cause of chronic wrist pain, with no ideal treatment. The authors developed arthroscopic transplantation of osteochondral autograft from lateral femoral condyle to distal radius with satisfactory outcome in 4 consecutive patients between December 2006 and December 2010. In all cases, graft incorporation was completed by 3 months to 4 months postoperation. All patients showed improvement in wrist function with no pain at follow-up at an average of 70.5 months (range 24-116 months). Second-look arthroscopy in 3 patients confirmed the preservation of normal articular cartilage. Patient satisfaction was high with no complications.

Autologous Chondrocyte Implantation Improves Knee-Specific Functional Outcomes and Health-Related Quality of Life in Adolescent Patients

BACKGROUND

Existing studies of autologous chondrocyte implantation (ACI) in adolescent patients have primarily reported outcomes that have not been validated for cartilage repair and have failed to include measures of general health or health-related quality of life.

PURPOSE

This study assesses validated knee-specific functional outcomes and health-related quality of life after ACI in adolescent patients.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients younger than 18 years who underwent ACI between 1999 and 2011 with a minimum 2-year clinical follow-up were identified from a prospectively collected database. A total of 37 patients were included in the analysis. Patient demographic data and pre- and postoperative functional outcomes scores were collected and chondral lesion characteristics were assessed. Primary outcome measures were the International Knee Documentation Committee (IKDC) subjective score and the Knee Injury and Osteoarthritis Outcome Score-Quality of Life (KOOS-QOL) subscore; secondary outcome measures were Short Form-12 (SF-12) and other KOOS subscores. In subgroup analyses, we assessed whether primary outcome results differed based on lesion location, concurrent meniscal allograft transplantation (MAT), and subsequent surgery after ACI.

RESULTS

Study patients had a mean 4.6 ± 2.4 years of follow-up, a mean age of 16.7 ± 1.5 years, and a mean lesion size of 4.0 ± 2.2 cm². The IKDC subjective score improved from 34.9 preoperatively to 64.6 postoperatively (mean improvement, 29.7 points [95% CI, 20.7 to 38.7 points]; P < .001) and the KOOS-QOL subscore improved from 24.3 to 55.3 (mean improvement, 31.0 points [95% CI, 21.3 to 40.7 points]; P < .001) at final follow-up. All other KOOS subscales and the SF-12 physical component score also showed significant improvements ( P < .008 in all cases), whereas the SF-12 mental component score showed no improvement ( P = .464). There was a 37.8% rate of subsequent surgery after ACI (most commonly, chondral debridement [54%], meniscectomy [11%], microfracture [9%], and loose body removal [9%]). Subgroup analysis showed no effect of lesion location, concurrent MAT, or subsequent surgery on improvement in IKDC subjective scores and KOOS-QOL subscores ( P > .05 in all cases).

CONCLUSION

ACI is an effective treatment for adolescent patients with symptomatic, large chondral lesions, resulting in significant improvements in knee-specific functional outcome scores and health-related quality of life scores. Although patients must be cautioned on the relatively high reoperation rate (37.8%) and limitations in knee function even after ACI, all patients in this study exhibited improvements over preoperative knee function at the most recent follow-up regardless of ACI location, concurrent MAT, or subsequent surgery.

Structural variations in articular cartilage matrix are associated with early-onset osteoarthritis in the spondyloepiphyseal dysplasia congenita (sedc) mouse

Heterozgyous spondyloepiphyseal dysplasia congenita (sedc/+) mice expressing a missense mutation in col2a1 exhibit a normal skeletal morphology but early-onset osteoarthritis (OA). We have recently examined knee articular cartilage obtained from homozygous (sedc/sedc) mice, which express a Stickler-like phenotype including dwarfism. We examined sedc/sedc mice at various levels to better understand the mechanistic process resulting in OA. Mutant sedc/sedc, and control (+/+) cartilages were compared at two, six and nine months of age. Tissues were fixed, decalcified, processed to paraffin sections, and stained with hematoxylin/eosin and safranin O/fast green. Samples were analyzed under the light microscope and the modified Mankin and OARSI scoring system was used to quantify the OA-like changes. Knees were stained with 1C10 antibody to detect the presence and distribution of type II collagen. Electron microscopy was used to study chondrocyte morphology and collagen fibril diameter. Compared with controls, mutant articular cartilage displayed decreased fibril diameter concomitant with increases in size of the pericellular space, Mankin and OARSI scores, cartilage thickness, chondrocyte clustering, proteoglycan staining and horizontal fissuring. In conclusion, homozygous sedc mice are subject to early-onset knee OA. We conclude that collagen in the mutant’s articular cartilage (both heterozygote and homozygote) fails to provide the normal meshwork required for matrix integrity and overall cartilage stability.

Factors predictive of outcome 5 years after matrix-induced autologous chondrocyte implantation in the tibiofemoral joint

BACKGROUND

Matrix-induced autologous chondrocyte implantation (MACI) has become an established technique for the repair of full-thickness chondral defects in the knee. However, little is known about what variables most contribute to postoperative clinical and graft outcomes as well as overall patient satisfaction with the surgery.

PURPOSE

To estimate the improvement in clinical and radiological outcomes and investigate the independent contribution of pertinent preoperative and postoperative patient, chondral defect, injury/surgery history, and rehabilitation factors to clinical and radiological outcomes, as well as patient satisfaction, 5 years after MACI.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

This study was undertaken in 104 patients of an eligible 115 patients who were recruited with complete clinical and radiological follow-up at 5 years after MACI to the femoral or tibial condyles. After a review of the literature, a range of preoperative and postoperative variables that had demonstrated an association with postoperative clinical and graft outcomes was selected for investigation. These included age, sex, and body mass index; preoperative 36-item Short Form Health Survey (SF-36) mental component score (MCS) and physical component score (PCS); chondral defect size and location; duration of symptoms and prior surgeries; and postoperative time to full weightbearing gait. The sport and recreation (sport/rec) and knee-related quality of life (QOL) subscales of the Knee Injury and Osteoarthritis Outcome Score (KOOS) were used as the patient-reported clinical evaluation tools at 5 years, while high-resolution magnetic resonance imaging (MRI) was used to evaluate graft assessment. An MRI composite score was calculated based on the magnetic resonance observation of cartilage repair tissue score. A patient satisfaction questionnaire was completed by all patients at 5 years. Regression analysis was used to investigate the contribution of these pertinent variables to 5-year postoperative clinical, radiological, and patient satisfaction outcomes.

RESULTS

Preoperative MCS and PCS and duration of symptoms contributed significantly to the KOOS sport/rec score at 5 years, while no variables, apart from the baseline KOOS QOL score, contributed significantly to the KOOS QOL score at 5 years. Preoperative MCS, duration of symptoms, and graft size were statistically significant predictors of the MRI score at 5 years after surgery. An 8-week postoperative return to full weightbearing (vs 12 weeks) was the only variable significantly associated with an improved level of patient satisfaction at 5 years.

CONCLUSION

This study outlined factors such as preoperative SF-36 scores, duration of knee symptoms, graft size, and postoperative course of weightbearing rehabilitation as pertinent variables involved in 5-year clinical and radiological outcomes and overall satisfaction. This information may allow orthopaedic surgeons to better screen their patients as good candidates for MACI, while allowing treating therapists to better individualize their preoperative preparatory and postoperative rehabilitation regimens for a best possible outcome.

Inflammatory markers associated with osteoarthritis after destabilization surgery in young mice with and without Receptor for Advanced Glycation End-products (RAGE)

HtrA1, Ddr-2, and Mmp-13 are reliable biomarkers for osteoarthritis (OA), yet the exact mechanism for the upregulation of HtrA-1 is unknown. Some have shown that chondrocyte hypertrophy is associated with early indicators of inflammation including TGF-β and the Receptor for Advanced Glycation End-products (RAGE). To examine the correlation of inflammation with the expression of biomarkers in OA, we performed right knee destabilization surgery on 4-week-old-wild type and RAGE knock-out (KO) mice. We assayed for HtrA-1, TGF-β1, Mmp-13, and Ddr-2 in articular cartilage at 3, 7, 14, and 28 days post-surgery by immunohistochemistry on left and right knee joints. RAGE KO and wild type mice both showed staining for key OA biomarkers. However, RAGE KO mice were significantly protected against OA compared to controls. We observed a difference in the total number of chondrocytes and percentage of chondrocytes staining positive for OA biomarkers between RAGE KO and control mice. The percentage of cells staining for OA biomarkers correlated with severity of cartilage degradation. Our results indicate that the absence of RAGE did protect against the development of advanced OA. We conclude that HtrA-1 plays a role in lowering TGF-β1 expression in the process of making articular cartilage vulnerable to damage associated with OA progression.

Autologous chondrocyte implantation in children and adolescents

PURPOSE

Autologous chondrocyte implantation (ACI) is a well-established treatment method for cartilage defects in knees. Age-related grouping was based on expression data of cartilage-specific markers. Specificities of ACI in the different populations were analysed.

METHODS

Two hundred and sixty-seven patients undergoing ACI in the knee between 2006 and 2010 were included in this analysis. Cell characteristics and expression data of cartilage-specific surface markers as CD44, aggrecan and collagen type II were statistically analysed for age association. Epidemiological data of the defined groups were compared. Course of treatment was evaluated using MRI.

RESULTS

A correlation analysis showed statistically significant associations between age and aggrecan or collagen type II expression in all patients <30 years. A cluster analysis could predict age-dependent expression of these markers separating groups with an average age of 18.1 ± 2.3 and 23.6 ± 4.2 years, respectively (p < 0.02). Discriminance analysis suggested the age border between adults and juveniles at about 20 years. There was no influence of age on cell characteristics or CD44 expression. In the 19 of 267 patients with an age ≤18 years, gender distribution was not different compared to adults, but patella was significantly more affected. Cartilage lesions were mainly caused by osteochondritis dissecans (OCD) and trauma. The Knee Osteoarthritis Scoring System in MRI reached 4.8 ± 2.3 points before, declining to 3.3 ± 2.3 points 6 and 12 months after the operation.

CONCLUSIONS

Age-related expression of cartilage-specific markers allows definition of adolescents in cartilage regenerating surgery. Chondromalacia in these patients is mainly caused by OCD or trauma.

LEVEL OF EVIDENCE

Case series, Level IV.

Comparison of osteochondral autologous transplantation, microfracture, or debridement techniques in articular cartilage lesions associated with anterior cruciate ligament injury: a prospective study with a 3-year follow-up

PURPOSE

To compare the concomitant treatment of articular cartilage damage in the medial femoral condyle with osteochondral autologous transplantation (OAT), microfracture, or debridement procedures at the time of anterior cruciate ligament (ACL) reconstruction.

METHODS

Between 2006 and 2009, 102 patients with a mean age of 34.1 years and with an ACL rupture and articular cartilage damage in the medial femoral condyle of the knee were randomized to undergo OAT, microfractures, or debridement at the time of ACL reconstruction. A matched control group was included, comprising 34 patients with intact articular cartilage at the time of ACL reconstruction. There were 34 patients in the OAT-ACL group, 34 in the microfracture (MF)-ACL group, 34 in the debridement (D)-ACL group, and 34 in the control group with intact articular cartilage (IAC-ACL group). The mean time from ACL injury to operation was 19.32 ± 3.43 months, and the mean follow-up was 36.1 months (range, 34 to 37 months). Patients were evaluated with the International Knee Documentation Committee (IKDC) score, Tegner activity score, and clinical assessment.

RESULTS

Of 102 patients, 97 (95%) were available for the final follow-up. According to the subjective IKDC score, all 4 groups fared significantly better at the 3-year follow-up than preoperatively (P < .005). The OAT-ACL group's IKDC subjective knee evaluation was significantly better than that of the MF-ACL group (P = .024) and D-ACL group (P = .018). However, the IKDC subjective score of the IAC-ACL group was significantly better than the OAT-ACL group's IKDC evaluation (P = .043). There was no significant difference between the MF-ACL and D-ACL groups' IKDC subjective scores (P = .058). Evaluation of manual pivot-shift knee laxity according to the IKDC knee examination form showed similar findings for the 4 groups immediately postoperatively and at 3-year follow-up, and the findings were rated as normal or nearly normal (IKDC grade A or B) in 29 of 33 patients (88%) in the OAT-ACL group, 28 of 32 patients (88%) in the MF-ACL group, 27 of 32 patients (84%) in the D-ACL group, and 31 of 34 patients (91%) in the IAC-ACL group.

CONCLUSIONS

Our study shows that intact articular cartilage during ACL reconstruction yields more favorable IKDC subjective scores compared with any other articular cartilage surgery type. However, if an articular defect is present, the subjective IKDC scores are significantly better for OAT versus microfracture or debridement after a mean period of 3 years. Anterior knee stability results were not significantly affected by the different articular cartilage treatment methods.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

Ability to return to sports 5 years after matrix-associated autologous chondrocyte transplantation in an average population of active patients

BACKGROUND

Cartilage injuries often occur during sports activities, and return to sports after cartilage surgery is an important outcome parameter for different treatment methods in the competitive as well as the recreationally active population.

HYPOTHESIS

At the time of midterm follow-up after matrix-associated autologous chondrocyte transplantation (MACT), return to recreational sports at the preinjury level will be possible.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Seventy patients (51 men, 19 women; age [mean ± standard deviation], 34.9 ± 8.6 y; range, 18-55 y) were clinically evaluated 5 years after MACT through subjective clinical scores such as the Knee Injury and Osteoarthritis Outcome Score (KOOS) sport and recreation subscales, the Tegner activity scale, and the Noyes sports activity rating scale. The level of sports participation was included in the investigation.

RESULTS

The results 5 years after MACT showed mean values of 60.1 for the KOOS-sport, 67.4 for the Noyes, and 3.8 for the Tegner scores, meaning that regular sports activity such as cycling or running on flat ground, as well as medium-level manual labor, is possible. We noted that 74.3% of our patients returned to at least their preinjury sports level.

CONCLUSION

Midterm postoperative results after MACT show that in a moderately active population, participation in regular sports is possible for most patients, at least at their preinjury recreational level and intensity, and there is a good rate of return to sports.

Knee chondral injuries: clinical treatment strategies and experimental models

Articular cartilage has a very limited capacity to repair and as such premature joint degeneration is often the end point of articular injuries. Patients with chondral injury have asymptomatic periods followed by others in which discomfort or pain is bearable. The repair of focal cartilage injuries requires a precise diagnosis, a completed knee evaluation to give the correct indication for surgery proportional to the damage and adapted to each patient. Many of the surgical techniques currently performed involve biotechnology. The future of cartilage repair should be based on an accurate diagnosis using new MRI techniques. Clinical studies would allow us to establish the correct indications and surgical techniques implanting biocompatible and biodegradable matrices with or without stem cells and growth factors. Arthroscopic techniques with the design of new instruments can facilitate repair of patella and tibial plateau lesions.

Cartilage restoration in haemophilia: advanced therapies

Current treatment of joint cartilage lesions is based either on conventional techniques (bone marrow stimulation, osteochondral autograft or allograft transplantation) or on newly developed techniques (chondrocyte implantation and those based on cell therapy that use bioreactors, growth factors, mesenchymal stem cells [MSCs] and genetically modified cells). The aim of this article is to review the therapeutic strategies above mentioned and to determine whether the chondral damage seen in haemophilia could benefit from any of them. The different conventional techniques have shown similar results whereas autologous chondrocyte implantation, which is in common use at the present time, has not been shown to produce any conclusive results or to lead to the formation of hyaline cartilage. MSCs hold promise for the repair of joint cartilage given their differentiation capacity and the therapeutic effect. The use of bioreactors and growth factors, which stimulate cartilage formation, may optimize such strategies in the context of reimplantation of chondrocytes, differentiated MSCs and cartilage progenitor cells. The aim of cell therapy is restoration of function through the repair of damaged tissue or the stimulation of growth factor synthesis. Implantation of autologous chondrocytes or MSCs was up to now able to address only highly localized chondral lesions. Adequate control of the differentiation process as well as the use of growth factors and appropriate bioreactors could transform cell-based therapies into a more efficient and longer term treatment even for patients with haemophilia. Nevertheless, raising false expectations in these patients should be avoided. There are a number of approaches to cartilage restoration in haemophilic arthropathy, which are currently being explored for other joint related degenerative disorders. If it can be proven to be effective for the disorders in which clinical trials are ongoing and costs could be limited, it might be an useful palliative approach to haemophilic arthropathy. However, we still have a long way to go for use in haemophilic arthropathy.

Acute traumatic and sports-related osteochondral injury of the pediatric knee

Adolescents are predisposed to osteochondral (OC) injuries in the knee. The medial facet of the patella, the femoral trochlea, and the lateral femoral condyle are the most common sites of injury. Most of these injuries are classically traumatic but noncontact injuries. Surgery is warranted in most cases of OC fracture. Depending on size, condition, and location of the lesion, options include OC fragment reduction and internal fixation or excision and cartilage resurfacing. Understanding of how to diagnose and treat OC fractures will help optimize outcomes.

Cartilage matrix formation by bovine mesenchymal stem cells in three-dimensional culture is age-dependent

BACKGROUND

Cartilage degeneration is common in the aged, and aged chondrocytes are inferior to juvenile chondrocytes in producing cartilage-specific extracellular matrix. Mesenchymal stem cells (MSCs) are an alternative cell type that can differentiate toward the chondrocyte phenotype. Aging may influence MSC chondrogenesis but remains less well studied, particularly in the bovine system.

QUESTIONS/PURPOSES

The objectives of this study were (1) to confirm age-related changes in bovine articular cartilage, establish how age affects chondrogenesis in cultured pellets for (2) chondrocytes and (3) MSCs, and (4) determine age-related changes in the biochemical and biomechanical development of clinically relevant MSC-seeded hydrogels.

METHODS

Native bovine articular cartilage from fetal (n = 3 donors), juvenile (n = 3 donors), and adult (n = 3 donors) animals was analyzed for mechanical and biochemical properties (n = 3-5 per donor). Chondrocyte and MSC pellets (n = 3 donors per age) were cultured for 6 weeks before analysis of biochemical content (n = 3 per donor). Bone marrow-derived MSCs of each age were also cultured within hyaluronic acid hydrogels for 3 weeks and analyzed for matrix deposition and mechanical properties (n = 4 per age).

RESULTS

Articular cartilage mechanical properties and collagen content increased with age. We observed robust matrix accumulation in three-dimensional pellet culture by fetal chondrocytes with diminished collagen-forming capacity in adult chondrocytes. Chondrogenic induction of MSCs was greater in fetal and juvenile cell pellets. Likewise, fetal and juvenile MSCs in hydrogels imparted greater matrix and mechanical properties.

CONCLUSIONS

Donor age and biochemical microenvironment were major determinants of both bovine chondrocyte and MSC functional capacity.

CLINICAL RELEVANCE

In vitro model systems should be evaluated in the context of age-related changes and should be benchmarked against human MSC data.

Autologous chondrocyte implantation in the adolescent knee

BACKGROUND

Autologous chondrocyte implantation (ACI) has been shown to have favorable results in the treatment of symptomatic chondral and osteochondral lesions. However, there are few reports on the outcomes of this technique in adolescents.

PURPOSE

The aim of this study was to assess pain relief and functional outcome in adolescents undergoing ACI.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Thirty-five adolescent patients undergoing ACI or matrix-assisted chondrocyte implantation (MACI) were identified from a larger cohort. Four patients were lost to follow-up, leaving 31 patients (24 ACI, 7 MACI). The mean age was 16.3 years (range, 14-18 years) with a mean follow-up of 66.3 months (range, 12-126 months). There were 22 male and 9 female patients. All patients were symptomatic; 30 had isolated lesions and 1 had multiple lesions. Patients were assessed preoperatively and postoperatively using the visual analog scale (VAS) score for pain, the Bentley Functional Rating Score, and the Modified Cincinnati Rating System. At 1 year postoperatively, patients were recalled for a diagnostic biopsy, which was successfully attained in 21 patients.

RESULTS

The mean pain scores improved from 5 preoperatively to 1 postoperatively. The Bentley Functional Rating Score improved from 3 to 0, while the Modified Cincinnati Rating System improved from 48 preoperatively to 92 postoperatively with 84% of patients achieving excellent or good results. All postoperative scores exhibited significant improvement from preoperative scores. One patient underwent graft hypertrophy and 1 patient's graft failed and was revised. Biopsy results revealed hyaline cartilage in 24% of cases, mixed fibro/hyaline cartilage in 19%, and fibrocartilage in 57%.

CONCLUSION

Results show that, in this particular group who received ACI, patients experienced a reduction in pain and significant improvement in postoperative function after ACI or MACI. The authors believe that ACI is appropriate in the management of carefully selected adolescents with symptomatic chondral and osteochondral defects.

Improved bioengineered cartilage tissue formation following cyclic compression is dependent on upregulation of MT1-MMP

The generation of bioengineered cartilage tissue suitable for transplantation is a potential therapy to treat damaged cartilage. We have shown previously that the physical and biomechanical properties of bioengineered cartilage can be improved by the application of 30 min of cyclic compression by a mechanism involving sequential upregulation of gene and protein levels of membrane type-1 matrix metalloproteinase (MT1-MMP) and MMP-13. In the current study, we demonstrated that MT1-MMP is critical to this response, as blocking the upregulation of MT1-MMP prevented the improvement in tissue formation. MT1-MMP seems to act by inducing tissue remodeling as evidenced by the presence of aggrecan degradation products by Western blot analysis and increased release of matrix molecules into the media. Release of these molecules was diminished when MT1-MMP upregulation was prevented. This matrix degradation was likely due to MT1-MMP, as under conditions where MMP-13 expression is maintained (stimulation in the presence of MT1-MMP siRNA) the release of these matrix molecules into the media was still prevented. It also appears that MT1-MMP does not regulate MMP-13 gene expression, as MT1-MMP-siRNA pretreatment had no effect on MMP-13 expression following mechanical stimulation. Further analysis of the anabolic genes and proteins involved in mechanically stimulated cartilage will lead to better understanding of the mechanism(s) underlying tissue formation yielding improved bioengineered cartilage.

Rehabilitation after autologous chondrocyte implantation in athletes

Over the years a variety of cartilage restorative procedures have been developed for athletes to address focal, full-thickness cartilaginous defects in the knee joint, including microfracture, osteochondral autografts, osteochondral allografts, autologous chondrocyte implantation (ACI), and most recently, next-generation ACI involving scaffolds or cell-seeded scaffolds. Since its introduction, ACI has yielded some very promising results in athletes and nonathletes alike. Rehabilitation following ACI requires an in-depth understanding of joint mechanics, and knowledge of the biologic and biomechanical properties of healing articular cartilage. A patient-, lesion-, and sports-specific approach is required on the part of the trainer or physical therapist to gradually restore knee joint function and strength so that the athlete may be able to return to competitive play. This article reviews the rehabilitation protocols for injured athletes following an ACI procedure.

Treatment of chondral defects in the athlete's knee

PURPOSE

To determine which surgical technique(s) has improved outcomes and enables athletes to return to their preinjury level of sports and which patient and defect factors significantly affect outcomes after cartilage repair or restoration.

METHODS

We conducted a search of multiple medical databases, evaluating studies of articular cartilage repair in athletes.

RESULTS

We identified 11 studies for inclusion (658 subjects). Only 1 randomized clinical trial was identified. All other studies were prospective cohorts, case-control studies, or case series reporting results after either microfracture or autologous chondrocyte implantation (ACI) or osteoarticular transplantation (OATS). Eight different clinical outcomes measures were used. Better clinical outcomes were observed after ACI and OATS versus microfracture. Results after microfracture tended to deteriorate with time. The overall rate of return to preinjury level of sports was 66%. The timing of return to the preinjury level of sports was fastest after OATS and slowest after ACI. Defect size of less than 2 cm(2), preoperative duration of symptoms of less than 18 months, no prior surgical treatment, younger patient age, and higher preinjury and postsurgical level of sports all correlated with improved outcomes after cartilage repair, especially ACI. Results after microfracture were worse with larger defects. The rate of return to sports was generally lower after microfracture versus ACI or OATS, and if a patient was able to return to sports, performance was diminished as well.

CONCLUSIONS

Management of chondral defects in the athlete is complex and multifactorial. There is little high-level evidence to support one procedure over another, although good short-term and midterm outcomes with a fair rate of return to preinjury level of sports can be achieved with cartilage repair and restoration in the athlete.

LEVEL OF EVIDENCE

Level IV, systematic review.

A prospective, randomized clinical study of osteochondral autologous transplantation versus microfracture for the treatment of osteochondritis dissecans in the knee joint in children

PURPOSE

The aim of this study was to compare the outcomes of the arthroscopic mosaic-type osteochondral autologous transplantation (OAT) and microfracture (MF) procedures for the treatment of osteochondritis dissecans (OCD) defects of the femoral condyles of the knee joint in children under the age of 18 years.

TYPE OF STUDY

Prospective, randomized clinical study.

METHODS

Between 2001 and 2005, a total of 50 children with a mean age of 14.3 years (12 to 18) and with symptomatic lesions of the OCD in the femoral condyle of the knee were randomized to undergo either the OAT or the MF procedure. Only those children with grade 3 or 4 (OCD) in the medial or lateral femoral condyle (according to International Cartilage Repair Society, ICRS) were included in the study. Forty-seven patients (94%) were available for follow-up. There were 25 patients in the OAT group and 22 patients in the MF group. The mean duration of symptoms was 23.54+/-4.24 months and the mean follow-up was 4.2 years (range from 3 to 6 y), and none of the children had prior surgical interventions to the affected knee. Children were evaluated using ICRS score, x-rays, magnetic resonance imaging, and second-look arthroscopies.

RESULTS

After 1 year, both groups had significant clinical improvement (P<0.05) and the ICRS functional and objective assessment showed that 23 of 25 (92%) patients had excellent or good results after OAT compared with 19 of 22 (86%) after MF (NS), but 19 of 23 (83%) after OAT and only 12 of 19 (63%) after MF procedure maintained excellent or good results after 4.2 years (range from 3 to 6 y). The MF group showed significant deterioration over the 4.2 years follow-up (P<0.05), but still had significant clinical improvement compared with pretreatment evaluation (P=0.004). There were 9 of 22 (41%) failures in the MF group, and none in the OAT group. Magnetic resonance imaging evaluation according to the ICRS evaluation system showed excellent or good repairs in 19 of 21 patients (91%) after OAT compared with 10 of 18 (56%) after MF.

CONCLUSIONS

At an average of 4.2 years follow-up, our prospective, randomized, clinical study in children under the age of 18 years has shown significant superiority of the mosaic-type OAT over MF for the treatment of osteochondritis dissecans defects in the knee. However, our study has shown that both MF and OAT give encouraging clinical results for children under the age of 18 years.

LEVEL OF EVIDENCE

Level 1: randomized controlled trial, significant difference.