Repair of osteochondral defects: efficacy of a tissue-engineered hybrid implant containing both human MSC and human iPSC-cartilaginous particles

Both mesenchymal stromal cells (MSC) and induced pluripotent stem cells (iPSC) offer the potential for repair of damaged connective tissues. The use of hybrid implants containing both human MSC and iPSC was investigated to assess their combined potential to yield enhanced repair of osteochondral defects. Human iPSC-CP wrapped with tissue engineered constructs (TEC) containing human MSC attained secure defect filling with good integration to adjacent tissue in a rat osteochondral injury model. The presence of living MSC in the hybrid implants was required for effective biphasic osteochondral repair. Thus, the TEC component of such hybrid implants serves several critical functions including, adhesion to the defect site via the matrix and facilitation of the repair via live MSC, as well as enhanced angiogenesis and neovascularization. Based on these encouraging studies, such hybrid implants may offer an effective future intervention for repair of complex osteochondral defects.

Adipose Tissue-Derived Mesenchymal Stem Cells as a Potential Restorative Treatment for Cartilage Defects: A PRISMA Review and Meta-Analysis

Cartilage defects are a predisposing factor for osteoarthritis. Conventional therapies are mostly palliative and there is an interest in developing newer therapies that target the disease’s progression. Mesenchymal stem cells (MSCs) have been suggested as a promising therapy to restore hyaline cartilage to cartilage defects, though the optimal cell source has remained under investigation. A PRISMA systematic review was conducted utilising five databases (MEDLINE, EMBASE, Cochrane Library, Scopus, Web of Science) which identified nineteen human studies that used adipose tissue-derived MSC (AMSC)-based therapies, including culture-expanded AMSCs and stromal vascular fraction, to treat cartilage defects. Clinical, imaging and histological outcomes, as well as other relevant details pertaining to cartilage regeneration, were extracted from each study. Pooled analysis revealed a significant improvement in WOMAC scores (mean difference: −25.52; 95%CI (−30.93, −20.10); p < 0.001), VAS scores (mean difference: −3.30; 95%CI (−3.72, −2.89); p < 0.001), KOOS scores and end point MOCART score (mean: 68.12; 95%CI (62.18, 74.05)), thus showing improvement. The studies in this review demonstrate the safety and efficacy of AMSC-based therapies for cartilage defects. Establishing standardised methods for MSC extraction and delivery, and performing studies with long follow-up should enable future high-quality research to provide the evidence needed to bring AMSC-based therapies into the market.

An additional lysis procedure during arthrocentesis of the temporomandibular joint

BACKGROUND

Arthrocentesis of the temporomandibular joint (TMJ) is an easy, highly efficient, minimally invasive procedure for treating temporomandibular joint disorders (TMDs). However, in some cases of mouth opening limitation (MOL), routine arthrocentesis is ineffective due to severe fibrotic adhesion in the superior joint space of the TMJ. In this condition, mechanical lysis of the adhesions might be needed to resolve the MOL, as well as other symptoms, such as chronic pain. Currently, this can be achieved by arthroscopic surgery or open TMJ surgery. The objective of this study was to introduce and evaluate our trial of the adhesion lysis procedure during arthrocentesis of the TMJ using normal 18-gauge needles.

RESULTS

In this study, 40 patients with MOL due to disc derangement underwent conventional arthrocentesis at first and then physical detachment was conducted using the same needle. The change in maximum mouth opening (MMO) and the pain at the TMJ were recorded before, during, and after treatment according to our protocol. The mean increase in MMO after conventional arthrocentesis was 6.6 ± 4.2mm. The mean increase in MMO after the detachment procedure with the same needle was 4.2 ± 2.0 mm. The MMO in ten patients was significantly increased after the detachment procedure than after arthrocentesis alone. In all cases, the pain intensity in the TMJ significantly decreased over time, whereas the MMO increased over time. No adverse effect was observed in all joints during our observation periods.

CONCLUSION

We confirmed that our simple lysis procedure with the same needle of the arthrocentesis of the TMJ could not only improve the MMO more than after a conventional arthrocentesis but also resolve severe adhesion of the joint space that was ineffective by conventional arthrocentesis. Although this additional lysis procedure is simple, it might reduce the number of cases of more invasive procedures such as arthroscopic surgery or open TMJ surgery.

The effectiveness of platelet-rich plasma gel on full-thickness cartilage defect repair in a rabbit model

AIMS

The present study investigates the effectiveness of platelet-rich plasma (PRP) gel without adjunct to induce cartilage regeneration in large osteochondral defects in a rabbit model.

METHODS

A bilateral osteochondral defect was created in the femoral trochlear groove of 14 New Zealand white rabbits. The right knees were filled with PRP gel and the contralateral knees remained untreated and served as control sides. Some animals were killed at week 3 and others at week 12 postoperatively. The joints were harvested and assessed by Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) MRI scoring system, and examined using the International Cartilage Repair Society (ICRS) macroscopic and ICRS histological scoring systems. Additionally, the collagen type II content was evaluated by the immunohistochemical staining.

RESULTS

After 12 weeks post-surgery, the defects of the PRP group were repaired by hyaline cartilage-like tissue. However, incomplete cartilage regeneration was observed in the PRP group for three weeks. The control groups showed fibrocartilaginous or fibrous tissue, respectively, at each timepoint.

CONCLUSION

Our study proved that the use of PRP gel without any adjuncts could successfully produce a good healing response and resurface the osteochondral defect with a better quality of cartilage in a rabbit model. Cite this article: Bone Joint Res 2021;10(3):192-202.

Surgical Management of Osteochondral Defects of the Knee: An Educational Review

PURPOSE OF REVIEW

Numerous surgical techniques are available to treat osteochondral defects of the knee. The aim of this review is to analyse these procedures, including their methodology, outcomes and limitations, to create a treatment algorithm for optimal management.

RECENT FINDINGS

Osteochondral defects of the knee significantly alter the biomechanics of the joint. This can cause symptomatic and functional impairment as well as considerable risk of progressive joint degeneration. Surgical interventions aim to restore a congruent, durable joint surface providing symptomatic relief and reducing the risk of early arthritic changes. These methods include fixation, chondroplasty, microfracture, autologous matrix-induced chondrogenesis, autograft transplants, allograft transplants and autologous chondrocyte implantation. There is currently much debate as to which of these methods provides optimal treatment of osteochondral defects. The overall evidence supports the use of each technique depending on the individual characteristics of the lesion. New technologies provide exciting prospects; however, long-term outcomes for these are not yet available.

Managing Chondral Lesions: A Literature Review and Evidence-Based Clinical Guidelines

BACKGROUND

Articular cartilage lesions are becoming increasingly common. Optimum diagnosis and management of chondral defects cause a lot of dilemma. A number of surgical methods have been reported in the literature for treating focal cartilage defects. There is a lack of consensus on the most effective management strategy, with newer surgical and cell-based treatments being advocated regularly.

STUDY DESIGN AND METHODS

A clinical review is constructed by appraising the published literature about clinical evaluation and diagnostic modalities for articular cartilage defects and subsequent surgical procedures, management strategies employed for such lesions. Prominent available databases (PUBMED, EMBASE, Cochrane) were also searched for trials comparing functional outcomes following cartilage procedures. Synthesis of a practical management guideline is then attempted based on the evidence assessed.

RESULTS

Systematic examination and optimal use of diagnostic imaging are an important facet of cartilage defect management. Patient and lesion factors greatly influence the outcome of cartilage procedures and must be considered while planning management. Smaller lesions < 2 cm² respond well to all treatment modalities. Autologous osteochondral transplants (OATs) are effective in high activity individuals with intermediate lesions. For larger lesions > 4 cm², newer generation autologous chondrocyte implantation (ACI) has shown promising and durable results. Stem cells with scaffolds may provide an alternate option. Orthobiologics are a useful adjunct to the surgical procedures, but need further evaluation.

CONCLUSIONS

Most treatment modalities have their role in appropriate cases and management needs to be individualized for patients. The search for the perfect cartilage restoration procedure continues.

Unfavorable Contribution of a Tissue-Engineering Cartilage Graft to Osteochondral Defect Repair in Young Rabbits

A stem cell-based tissue-engineering approach is a promising strategy for treatment of cartilage defects. However, there are conflicting data in the feasibility of using this approach in young recipients. A young rabbit model with an average age of 7.7 months old was used to evaluate the effect of a tissue-engineering approach on the treatment of osteochondral defects. Following in vitro evaluation of proliferation and chondrogenic capacity of infrapatellar fat pad-derived stem cells (IPFSCs) after expansion on either tissue culture plastic (TCP) or decellularized extracellular matrix (dECM), a premature tissue construct engineered from pretreated IPFSCs was used to repair osteochondral defects in young rabbits. We found that dECM expanded IPFSCs exhibited higher proliferation and chondrogenic differentiation compared to TCP expanded cells in both pellet and tissue construct culture systems. Six weeks after creation of bilateral osteochondral defects in the femoral trochlear groove of rabbits, the Empty group (left untreated) had the best cartilage resurfacing with the highest score in Modified O’Driscoll Scale (MODS) than the other groups; however, this score had no significant difference compared to that of 15-week samples, indicating that young rabbits stop growing cartilage once they reach 9 months old. Interestingly, implantation of premature tissue constructs from both dECM and TCP groups exhibited significantly improved cartilage repair at 15 weeks compared to those at six weeks (about 9 months old), indicating that a tissue-engineering approach is able to repair adult cartilage defects. We also found that implanted pre-labeled cells in premature tissue constructs were undetectable in resurfaced cartilage at both time points. This study suggests that young rabbits (less than 9 months old) might respond differently to the classical tissue-engineering approach that is considered as a potential treatment for cartilage defects in adult rabbits.

Fiber Reinforced Cartilage ECM Functionalized Bioinks for Functional Cartilage Tissue Engineering

Focal articular cartilage (AC) defects, if left untreated, can lead to debilitating diseases such as osteoarthritis. While several tissue engineering strategies have been developed to promote cartilage regeneration, it is still challenging to generate functional AC capable of sustaining high load-bearing environments. Here, a new class of cartilage extracellular matrix (cECM)-functionalized alginate bioink is developed for the bioprinting of cartilaginous tissues. The bioinks are 3D-printable, support mesenchymal stem cell (MSC) viability postprinting and robust chondrogenesis in vitro, with the highest levels of COLLII and ACAN expression observed in bioinks containing the highest concentration of cECM. Enhanced chondrogenesis in cECM-functionalized bioinks is also associated with progression along an endochondral-like pathway, as evident by increases in RUNX2 expression and calcium deposition in vitro. The bioinks loaded with MSCs and TGF-β3 are also found capable of supporting robust chondrogenesis, opening the possibility of using such bioinks for direct "print-and-implant" cartilage repair strategies. Finally, it is demonstrated that networks of 3D-printed polycaprolactone fibers with compressive modulus comparable to native AC can be used to mechanically reinforce these bioinks, with no loss in cell viability. It is envisioned that combinations of such biomaterials can be used in multiple-tool biofabrication strategies for the bioprinting of biomimetic cartilaginous implants.

Failure After Osteochondral Allograft Transplantation with the Chondrofix Implant: A Report of Two Cases

CASE

This report describes 2 cases of failed decellularized "off-the-shelf" Chondrofix (Zimmer Biomet) osteochondral allografts within a year after implantation in a 44-year-old man and a 50-year-old woman.

CONCLUSION

Although it is a successful technique for cartilage repair, the use of osteochondral allograft transplantation has been limited by the availability of fresh grafts; therefore, decellularized osteochondral allografts recently have been developed. Physicians should be cautious when considering the use of these implants for the repair of articular cartilage lesions.

Treatment of Articular Cartilage Defects With Microfracture and Autologous Matrix-Induced Chondrogenesis Leads to Extensive Subchondral Bone Cyst Formation in a Sheep Model

BACKGROUND

Microfracture and the autologous matrix-induced chondrogenesis (AMIC) technique are popular for the treatment of articular cartilage defects. However, breaching of the subchondral bone plate could compromise the subchondral bone structure.

HYPOTHESIS

Microfracture and AMIC will cause deleterious effects on the subchondral bone structure.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 36 sheep received an 8-mm-diameter cartilage defect in the left medial femoral condyle. Control animals (n = 12) received no further treatment, and the rest received 5 microfracture holes either with a type I/III collagen scaffold implanted (n = 12; AMIC group) or without the collagen scaffold (n = 12; microfracture group). Macroscopic infill of defects, histology, and histomorphometry of the subchondral bone were performed at 13 and 26 weeks postoperatively, and micro-computed tomography (CT) was also performed at 26 weeks postoperatively.

RESULTS

Microfracture and AMIC resulted in subchondral bone cyst formation in 5 of 12 (42%) and 11 of 12 (92%) specimens at 13 and 26 weeks, respectively. Subchondral bone changes induced by microfracture and AMIC were characterized by an increased percentage of bone volume, increased trabecular thickness, and a decreased trabecular separation, and extended beyond the area below the defect. High numbers of osteoclasts were observed at the cyst periphery, and all cysts communicated with the microfracture holes. Cartilage repair tissue was of poor quality and quantity at both time points and rarely reached the tidemark at 13 weeks.

CONCLUSION

Microfracture technique caused bone cyst formation and induced severe pathology of the subchondral bone in a sheep model.

CLINICAL RELEVANCE

The potential of microfracture technique to induce subchondral bone pathology should be considered.

Osteochondritis dissecans of the knee

Osteochondritis Dissecans (OCD) is a condition for which the aetiology remains unknown. It affects subchondral bone and secondarily its overlying cartilage and is mostly found in the knee. It can occur in adults, but is generally identified when growth remains, when it is referred to as juvenile OCD. As the condition progresses, the affected subchondral bone separates from adjacent healthy bone, and can lead to demarcation and separation of its associated articular cartilage. Any symptoms which arise relate to the stage of the disease. Early disease without separation of the lesion results in pain. Separation of the lesion leads to mechanical symptoms and swelling and, in advanced cases, the formation of loose bodies.

Early identification of OCD is essential as untreated OCD can lead to the premature degeneration of the joint, whereas appropriate treatment can halt the disease process and lead to healing. Establishing the stability of the lesion is a key part of providing the correct treatment. Stable lesions, particularly in juvenile patients, have greater propensity to heal with non-surgical treatment, whereas unstable or displaced lesions usually require surgical management.

This article discusses the aetiology, clinical presentation and prognosis of OCD in the knee. It presents an algorithm for treatment, which aims to promote healing of native hyaline cartilage and to ensure joint congruity.

Take home message: Although there is no clear consensus as to the best treatment of OCD, every attempt should be made to retain the osteochondral fragment when possible as, with a careful surgical technique, there is potential for healing even in chronic lesions

Cite this article: Bone Joint J 2016;98-B:723–9.

Knee Articular Cartilage Repair and Restoration Techniques: A Review of the Literature

CONTEXT

Isolated chondral and osteochondral defects of the knee are a difficult clinical challenge, particularly in younger patients for whom alternatives such as partial or total knee arthroplasty are rarely advised. Numerous surgical techniques have been developed to address focal cartilage defects. Cartilage treatment strategies are characterized as palliation (eg, chondroplasty and debridement), repair (eg, drilling and microfracture [MF]), or restoration (eg, autologous chondrocyte implantation [ACI], osteochondral autograft [OAT], and osteochondral allograft [OCA]).

EVIDENCE ACQUISITION

PubMed was searched for treatment articles using the keywords knee, articular cartilage, and osteochondral defect, with a focus on articles published in the past 5 years.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 4.

RESULTS

In general, smaller lesions (<2 cm(2)) are best treated with MF or OAT. Furthermore, OAT shows trends toward greater longevity and durability as well as improved outcomes in high-demand patients. Intermediate-size lesions (2-4 cm(2)) have shown fairly equivalent treatment results using either OAT or ACI options. For larger lesions (>4 cm(2)), ACI or OCA have shown the best results, with OCA being an option for large osteochondritis dissecans lesions and posttraumatic defects.

CONCLUSION

These techniques may improve patient outcomes, though no single technique can reproduce normal hyaline cartilage.

Impact of lesion location on the progression of osteoarthritis in a rat knee model

To investigate how surgically created acute full-thickness cartilage defects of similar size and location created on the medial versus lateral femoral condyle influence progression of spontaneous cartilage lesions in a rat model. Full-thickness cartilage defects of 1 mm were surgically created on the medial or lateral femoral condyles on the right leg of 20 rats (n = 10/group). Ten rats served as controls. Spontaneous lesion progression on the ipsilateral and contralateral surfaces was examined using a high-resolution digital camera along with H&E and Safranin-O staining. Chondral defects were scored grossly and histologically. Control femur displayed no cartilage disruption. Surgically treated knees exhibited created and spontaneous cartilage defects with no evidence of healing unless subchondral bone was penetrated. Ipsilateral spontaneous lesions on the lateral condyle were significantly more severe on average (p = 0.009) compared to medial lesions on gross examination. Histological examination found contralateral lesions on the lateral surface following surgically created medial lesions to be more severe (p = 0.057) compared to contralateral lesions. A trend toward more susceptible chondral damage to the lateral condyle was observed following acute lesion creation on either medial or lateral condyles. Mechanisms behind this pattern of spontaneous lesion development are unclear, requring further investigation.

Biomaterials for tissue engineering

Biomaterials serve as an integral component of tissue engineering. They are designed to provide architectural framework reminiscent of native extracellular matrix in order to encourage cell growth and eventual tissue regeneration. Bone and cartilage represent two distinct tissues with varying compositional and mechanical properties. Despite these differences, both meet at the osteochondral interface. This article presents an overview of current biomaterials employed in bone and cartilage applications, discusses some design considerations, and alludes to future prospects within this field of research.

MATRIX-INDUCED AUTOLOGOUS CHONDROCYTE IMPLANTATION FOR TREATMENT OF CHONDRAL DEFECTS OF KNEE: A PRELIMINARY REPORT

Objective: To present clinical experience on matrix-induced autologous chondrocyte implantation (MACI), we hereby reported treatment with MACI for 3 patients suffering from chondral lesion of the knee, each of them has been followed for a minimum of 10 months.

Methods: Ages of 3 patients were 25, 15 and 32 years old respectively. And the cartilage defect size ranged from 6cm2-10.5cm2). IKDC2000 score was used for knee functional evaluation. Magnetic resonance imaging (MRI) and arthroscopy were performed preoperatively and postoperatively. A biopsy of the regenerated cartilage from one patient was histologically evaluated 15 months after MACI.

Results: In the postoperative period, no associated complications were observed. Each patient showed improvements both in clinical and functional status after surgery. MRI and arthroscopy showed the presence of hyaline-like cartilage at the site of implantation. The cartilage biopsy on the first patient showed a high ratio of hyaline-like cartilage tissue to fibrocartilage tissue which was 2 to 1.

Conclusion: The clinical outcome and histological evaluation suggest that MACI is able to relieve pain and restore the function of the knee, also is capable of regenerating hyaline cartilage. In conclusion, MACI appears a promising method for the treatment of chondral defects of the knee.

Arthroscopic De Novo NT(®) juvenile allograft cartilage implantation in the talus: a case presentation

Osteochondral defects of the talus are a challenging subject facing foot and ankle surgeons. The available treatment options have relatively good subjective outcomes; however, they are limited by the ability to reproduce hyaline cartilage, the need for multiple surgeries, and high morbidity. We present a new technique using DeNovo NT(®) juvenile allograft cartilage implantation introduced into a talar lesion arthroscopically in a single procedure to repair a posteriomedial talar osteochondral defects in a healthy, active 30-year-old female. The patient tolerated the procedure well. At the 6-month follow-up visit, the patient had returned to full activity, and at 24 months, she remained completely pain free.

Management of focal chondral lesion in the knee joint

Articular cartilage does not contain vascular, nervous and lymphatic tissue and chondrocytes hardly participate in the healing or repair process of chondral tissue because of being surrounded by plenty of extracellular matrix. Therefore, the injury to articular cartilage frequently requires an operative treatment. The goal of surgical repair of articular cartilage is to regenerate nearly normal chondral tissue and prevent degenerative arthritis caused by the articular cartilage defect. Microfracture is a kind of cartilage repair procedure that makes a fibrin clot containing mesenchymal stem cells in the chondral lesion. Microfracture is a simple procedure but it has a disadvantage that the repaired tissue is fibrocartilage. Autologous chondrocyte implantation has an advantage that it implants fully differentiated chondrocytes to the lesion, which theoretically produces hyaline cartilage. Its disadvantages are that it is a two stage and a costly procedure. Osteochondral autograft transplantation is a one stage procedure and repairs the lesion with hyaline cartilage. But its limitation is the lack of donor site availability. Surgeons who understand the theoretical background, indications, surgical methods, rehabilitation, complications, and clinical course of cartilage repair procedures can achieve the goal of preventing degenerative arthritis.

Treatment of articular cartilage lesions of the knee

Treatment of articular cartilage lesions in the knee remains a challenge for the practising orthopaedic surgeon. A wide range of options are currently practised, ranging from conservative measures through various types of operations and, recently, use of growth factors and emerging gene therapy techniques. The end result of these methods is usually a fibrous repair tissue (fibrocartilage), which lacks the biomechanical characteristics of hyaline cartilage that are necessary to withstand the compressive forces distributed across the knee. The fibrocartilage generally deteriorates over time, resulting in a return of the original symptoms and occasionally reported progression to osteoarthritis. Our purpose in this study was to review the aetiology, pathogenesis and treatment options for articular cartilage lesions of the knee. At present, autologous cell therapies, growth factor techniques and biomaterials offer more promising avenues of research to find clinical answers.

Matrix-Induced Autologous Chondrocyte Implantation (MACI) grafting for osteochondral lesions of the talus

BACKGROUND

Articular cartilage is limited in its ability to repair itself. Matrix-induced Autologous Chondrocyte Implantation (MACI) is an established treatment method for such articular cartilage defects in the knee. Recently the technique has been used in the ankle. We present a series of patients treated with MACI for osteochondral defects of the ankle, and assess the functional and clinical results.

MATERIALS AND METHODS

From August 2003 to February 2006, 20 patients underwent MACI grafting for osteochondral defects in the ankle. Age ranged from 19 to 61 (mean, 36) years. Mean followup was 21.1 months. Clinical and functional evaluations were conducted using the AOFAS scoring system.

RESULTS

The mean size was 233 mm(2). There was a significant improvement in mean AOFAS score from 60 (range, 25 to 87) to 87 (range, 41 to 100) (p < 0.0001). Overall improvement in pain scores was also significant (p < 0.0001). All osteotomies healed. Four patients required hardware removal and two underwent arthroscopic debridement for anterior impingement. There were two failures which are awaiting subsequent procedures.

CONCLUSION

We believe MACI is a reliable treatment method for talar osteochondral defects. The method usually requires an intra-articular osteotomy, although this proved to be a reasonably simple aspect of the procedure for the treatment of cartilage defects of the talus.

Matrix-induced autologous chondrocyte implantation in sheep: objective assessments including confocal arthroscopy

The assessment of cartilage repair has largely been limited to macroscopic observation, magnetic resonance imaging (MRI), or destructive biopsy. The aims of this study were to establish an ovine model of articular cartilage injury repair and to examine the efficacy of nondestructive techniques for assessing cartilage regeneration by matrix-induced autologous chondrocyte implantation (MACI). The development of nondestructive assessment techniques facilitates the monitoring of repair treatments in both experimental animal models and human clinical subjects. Defects (Ø 6 mm) were created on the trochlea and medial femoral condyle of 21 sheep randomized into untreated controls or one of two treatment arms: MACI or collagen-only membrane. Each group was divided into 8-, 10-, and 12-week time points. Repair outcomes were examined using laser scanning confocal arthroscopy (LSCA), MRI, histology, macroscopic ICRS grading, and biomechanical compression analysis. Interobserver analysis of the randomized blinded scoring of LSCA images validated our scoring protocol. Pearson correlation analysis demonstrated the correlation between LSCA, MRI, and ICRS grading. Testing of overall treatment effect independent of time point revealed significant differences between MACI and control groups for all sites and assessment modalities (Asym Sig < 0.05), except condyle histology. Biomechanical analysis suggests that while MACI tissue may resemble native tissue histologically in the early stages of remodeling, the biomechanical properties remain inferior at least in the short term. This study demonstrates the potential of a multisite sheep model of articular cartilage defect repair and its assessment via nondestructive methods.

Influence of surgical preparation on the in-vivo response of osteochondral defects

Cartilage has an extremely poor capacity to heal, which has lead to intensive research into biomaterials and tissue engineering for the purpose of regenerating cartilage in vivo. Many of these techniques have shown great promise in vitro; however, the results do not always carry across to the in-vivo scenario. Healthy cartilage autografts often do not integrate with the adjacent cartilage, suggesting that cartilage is rarely capable of healing even under ideal conditions. It is hypothesized in this study that the surgical creation of defects in cartilage causes significant damage to the adjacent tissues, leading to further degradation of the cartilage and poor outcome for the repair in general. This study compares the healing response of osteochondral defects created with either a punch or a drill in the weight-bearing region of the sheep knee at 4 and 26 weeks following surgery. The use of a drill to create the defect creates a more aggressive inflammatory response at 4 weeks compared with a punch. However, by 26 weeks, defects created with a punch scored higher on the O'Driscoll cartilage grading scale. Tissue damage at the time of surgery plays an important part in the sequence of events for healing of cartilage defects. This knowledge will help to characterize and refine the ovine model for cartilage regeneration and may have an influence on surgical technique and instrumentation for clinical cartilage repair.

Crushed bone grafts and a collagen membrane are not suitable for enhancing cartilage quality in the regeneration of osteochondral defects—An in vivo study in sheep

Hyaline joint cartilage has only a limited potential for self-repair. Some of the published techniques for osteochondral defect therapy try to improve that potential. In this study, it was hypothesised that one of those surgical techniques, the crushed transplanted bone graft together with a collagen membrane, accelerates significantly the reconstruction of the subchondral bone plate and improves the mechanical and histological quality of repaired cartilage in osteochondral defects compared to an empty control defect. In order to test this hypothesis, defects were created in the left knee of 12 sheep and filled either with autologous crushed bone graft or left empty. The animals were sacrificed after 3 (n = 6) and 6 (n = 6) months. No differences were found either macroscopically or histomorphometrically between the bone graft and empty control defects. The biomechanical as well as the histological results of the bone graft defects were inferior to the control defects with inflammatory processes caused either by bone graft or membrane remnants. Based on the results in this sheep model, the filling of subchondral bone defects with compacted cancellous bone should be carefully reconsidered.

Articular cartilage defects of the distal femur in children and adolescents: treatment with autologous chondrocyte implantation

PURPOSE

Procedures aimed at biologically repairing cartilage injuries may have the greatest potential benefit in young patients because of their long-life expectancy and high-functional demands. Most cartilage-repair studies focus on older patient populations. This study assesses the outcomes of patients who were treated with autologous chondrocyte implantation before the age of 18.

STUDY DESIGN

This is a Registry-based, multicenter, observational, cohort study of 37 patients from whom follow-up data was prospectively collected. Patient-rated assessments of overall condition, pain, and swelling were measured using modified, 10-point scales of the Cincinnati Knee Rating System.

RESULTS

Mean age was 16 years (11-17); 22 boys and 15 girls. Twenty-three patients underwent at least 1 cartilage repair procedure before the cartilage harvest, including 11 who had a marrow stimulation procedure. Fourteen patients were diagnosed with osteochondritis dessicans lesions. Thirty-five patients had single defects (mean size, 5.4 cm). Thirty-two patients completed self-evaluations at a minimum of 2 years after implantation (mean follow-up = 4.3 years). The mean change in scale scores measuring overall condition, pain, and swelling were 3.8, 4.1, and 3.4 points, respectively. One patient had an implantation that failed.

CONCLUSIONS

Results highlight significant clinical improvements from baseline to follow-up for 32 patients who submitted follow-up data, including 28 patients who reported a minimum 1-point improvement in the overall condition score.

CLINICAL RELEVANCE

These results suggest that autologous chondrocyte implantation may be an effective option for children and adolescents with large symptomatic chondral lesions of the distal femur.

Autologous chondrocyte implantation versus matrix-induced autologous chondrocyte implantation for osteochondral defects of the knee

Autologous chondrocyte implantation (ACI) is used widely as a treatment for symptomatic chondral and osteochondral defects of the knee. Variations of the original periosteum-cover technique include the use of porcine-derived type I/type III collagen as a cover (ACI-C) and matrix-induced autologous chondrocyte implantation (MACI) using a collagen bilayer seeded with chondrocytes. We have performed a prospective, randomised comparison of ACI-C and MACI for the treatment of symptomatic chondral defects of the knee in 91 patients, of whom 44 received ACI-C and 47 MACI grafts.

Both treatments resulted in improvement of the clinical score after one year. The mean modified Cincinnati knee score increased by 17.6 in the ACI-C group and 19.6 in the MACI group (p = 0.32). Arthroscopic assessments performed after one year showed a good to excellent International Cartilage Repair Society score in 79.2% of ACI-C and 66.6% of MACI grafts. Hyaline-like cartilage or hyaline-like cartilage with fibrocartilage was found in the biopsies of 43.9% of the ACI-C and 36.4% of the MACI grafts after one year. The rate of hypertrophy of the graft was 9% (4 of 44) in the ACI-C group and 6% (3 of 47) in the MACI group. The frequency of re-operation was 9% in each group.

We conclude that the clinical, arthroscopic and histological outcomes are comparable for both ACI-C and MACI. While MACI is technically attractive, further long-term studies are required before the technique is widely adopted.