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Background
Articular cartilage damaged through acute or chronic trauma or osteochondritis dissecans has limited ability to regenerate, resulting in persistent joint line pain, recurrent synovitis and altered joint mechanics most commonly in weight-bearing joints. Loose bodies may develop, which may then cause joint destruction, restricted mobility and/or locking. Long standing severe damage to the articular cartilage can lead to debilitating osteoarthritis, which ultimately may require a total knee arthroplasty. Current therapeutic options include lavage and debridement, which may offer pain relief for up to several years, but offer no prospect of long-term cure. Similarly, marrow-stimulation techniques such as drilling or microfracture of the subchondral bone of cartilage lesions and abrasion arthroplasty may fail to provide long-term solutions because these procedures usually promote the development of fibrocartilage, which may be less durable than the hyaline cartilage that normally covers articular surfaces.
Osteochondral autografts have been examined as an alternative to allografts for the treatment of osteochondral defects. Two related procedures have been investigated: (i) mosaicplasty, and (ii) the osteochondral autograft transfer system (OATS). Mosaicplasty is a reconstructive bone grafting procedure for the treatment of articular defects of the knee. In general, treatment of articular defect of the knee by mosaicplasty entails transplantation of small cylindrical osteochondral grafts (4 to 10 mm in diameter, 15 to 20 mm deep) from the less weight-bearing periphery of the femoral condyles at the level of the patello-femoral joint, and transplanting them in a mosaic-like fashion into a prepared defect site on the weight-bearing surfaces of the same knee. Its goal is to produce a smooth gliding articular surface of hyaline or hyaline-like cartilage in weight-bearing surfaces of the knee. Mosaicplasty is carried out either by an open approach or arthroscopically if the defect/lesion is small and not more than 4 to 6 grafts are needed. Both open and arthroscopic mosaicplasty require a relatively short rehabilitation period -- normal daily activity can be allowed after 5 to 8 weeks.
Animal studies and subsequent clinical trials have demonstrated the survival of transplanted hyaline cartilage. In addition, there are limited studies comparing the results of mosaicplasty with other established procedures. However, long-term data are limited and it is unclear whether mosaicplasty can prevent further deterioration in the affected articular cartilage.
In a review on treatment osteochondral injuries of the knee, Cain and Clancy (2001) stated that the treatment of osteochondral fractures and osteochondral lesions in the knee is controversial. Although the results of many reconstructive procedures (e.g., autologous osteochondral mosaicplasty and osteochondral allograft transplantation) are quite encouraging with early follow-up, the ultimate goal is to prevent long-term degenerative arthritis. Only well-designed prospective studies with long-term follow-up will determine the effectiveness of these procedures in reaching the ultimate goal.
In a review on management of osteochondral injuries of the knee, Alleyne and Galloway (2001) stated that the management of articular cartilage lesions has yet to reveal a “right answer”, and that long-term follow-up studies of all of the techniques reviewed are needed to give definitive answers about the durability of the repaired and transplanted tissues.
In a review on mosaicplasty for the treatment of osteochondral defects of the ankle joint, Mendicino and associates (2001) stated that this procedure shows excellent promise for use in the ankle and warrants larger investigational studies to assess outcomes. In a randomized, clinical trial (n = 100),
Guidelines from the American College of Rheumatology on management of osteoarthritis (OA) of the hip and knee state that autologous osteochondral plugs (mosaicplasty) is being investigated for repair of focal chondral defects, but that this procedure is “not currently indicated in the treatment of patients with OA” (Altman et al, 2000).
An assessment of mosaicplasty for knee cartilage defects from the National Institute for Health and Clinical Excellence (NICE, 2006) concluded: "Current evidence suggests that there are no major safety concerns associated with mosaicplasty for knee cartilage defects. There is some evidence of short-term efficacy, but data on long-term efficacy are inadequate. In view of the uncertainties about the efficacy of the procedure, it should not be used without special arrangements for consent and audit or research."
More recently, an assessment of mosaicplasty for knee cartilage defects by the Institute for Clinical Effectiveness and Health Policy (Pichon-Riviere, et al., 2009) concluded: "At present, there is not good quality evidence that would allow the assessment of mosaicplasty versus other techniques. There are few clinical trials, with different surgical techniques; different rehabilitation protocols and outcomes evaluated using different scales. Additionally, these studies presented different follow-up periods which does not allow result comparison with others where surgical follow-up was not performed; it does not it allow long-term morbidity assessment of the graft donation site either. Because of the poor methodological quality of the studies, it is not possible to make specific recommendations on its use, considering it as experimental."
The osteochondral autograft transfer system is a procedure employed for medium sized areas of discrete damage (mosaicplasty is employed for even larger but discrete areas of damage).
The OATS procedure focuses on chondral defects that are associated with chronic tears of the anterior cruciate ligament (ACL), using an arthroscopic approach that can provide access to both the ACL for reconstruction and performance of the autograft. The orthopedic surgeon uses an apple-corer like instrument to core out a circle of damaged cartilage and replaces it with a piece of normal cartilage from a less important part of the same knee. The underlying principal is that the transferred cartilage will grow to cover the edges of the core with proper cartilage cells and not the weaker fibrocartilage cells.
Bobic (1996) reported the results of a case-series study (n = 12) regarding the use of OATS in patients with ACL-deficient knees. The series examined arthroscopic osteochondral autograft transplantation in conjunction with ACL reconstruction using bone-patellar tendon-bone autograft. Eight procedures were primary, and 4 were revisions of failed synthetic grafts. Chondral lesions in this series ranged from 10 to 22 mm in diameter. Donor site was selected prior to notchplasty, and 3 to 5 osteochondral cylinders, 5 to10 mm in diameter, 10 to15 mm long, were harvested. The author stated that improved surgical technique, tubular cutting instruments enabling minimal damage to harvested articular cartilage, and press-fit insertion yielded promising uniform results in 10 of 12 cases with 2 years' follow-up.
Wang (2002) reported a retrospective study of 15 patients with 16 knees who underwent osteochondral autografts for focal full thickness articular cartilage defects of the knee. Two to 4 years follow-up of these patients showed 80 % good or excellent clinical results. There was no correlation of the clinical results with the underlying diagnoses, including osteonecrosis, osteochondritis dissecans and traumatic cartilage defect, or a size of the lesion smaller than 600 mm2. However, cartilage lesions larger than 600 mm2 were associated with increasing fibrous tissue formation and fissuring between the grafts and the host tissues and poor results. The improvement in symptoms appeared time-dependent, ranging from 6 to 16 weeks, suggesting that post-operative protection of the graft is warranted. There was no radiographical progression of degenerative changes of the knee on the medium-term follow-up.
The BlueCross BlueShield Association Technology Evaluation Center (2003) stated that autogenous osteochondral transplantation (OATS or mosaicplasty) are not established treatments for chondral defects. “Although preliminary reports” of autogenous osteochondral transplantation (OATS or mosaicplasty) “appear favorable, only limited outcome data are available on this technology.”
Sharpe et al (2005) reported their 3-year post-operative findings on the use of a combination of autologous chondrocyte implantation (ACI) and the OATS procedure as a treatment option for the repair of large areas of degenerative articular cartilage. Osteochondral cores were used to restore the contour of articular cartilage in 13 patients with large lesions of the lateral femoral condyle (n = 5), medial femoral condyle (n = 7) and patella (n = 1). Autologous cultured chondrocytes were injected underneath a periosteal patch covering the cores. After 1 year, patients had a significant improvement in their symptoms and after 3 years this level of improvement was maintained in 10 of the 13 patients. Arthroscopic examination revealed that the osteochondral cores became well integrated with the surrounding cartilage. These investigators concluded that the hybrid ACI/OATS technique provides a promising surgical approach for the treatment of patients with large degenerative osteochondral defects.
Scheibel and colleagues (2004) performed 8 osteochondral autologous transplantations from the knee joint to the shoulder. All patients (2 women and 6 men; mean age of 43.1 years) were documented prospectively. In each patient the stage of the osteochondral lesion was Outerbridge grade IV with a mean size of the affected area of 150 mm2. All patients were assessed by using the Constant score for the shoulder and the Lysholm score for the knee. Standard radiographs, magnetic resonance imaging and second-look arthroscopy were used to evaluate the presence of glenohumeral osteoarthritis and the integrity of the grafts. After a mean of 32.6 months (8 to 47), the mean Constant score increased significantly. Magnetic resonance imaging revealed good osseo-integration of the osteochondral plugs and congruent articular cartilage at the transplantation site in all but 1 patient. Second-look arthroscopy performed in 2 cases revealed a macroscopically good integration of the autograft with an intact articular surface. The authors noted that osteochondral autologous transplantation in the shoulder appears to offer good clinical results for treating full-thickness osteochondral lesions of the glenohumeral joint. However, they also noted that the findings of their study suggest that the development of osteoarthritis and the progression of pre-existing osteoarthritic changes cannot be altered by this technique.
Tsuda and co-workers (2005) reported the use of osteochondral autograft transplantation in 3 cases of non-throwing athletes with osteochondritis dissecans of the capitellum. Pre-operatively, these patients complained of elbow pain during sports activities (rhythmic gymnastics, table tennis, and basketball, respectively). Magnetic resonance imaging (MRI) showed a completely separated osteochondral fragment or a full-thickness cartilage defect. All 3 patients were treated with transplantation of an osteochondral autograft harvested from the lateral femoral condyle. They returned fully to their sports activities within 6 months of surgery. The continuity of the cartilage layer between the osteochondral graft and the capitellum was shown on MRI taken at 12 months post-operatively. The authors believed that osteochondral autograft transplantation provides successful results for non-throwing athletes with end-stage osteochondritis dissecans of the capitellum.
Shimada and associates (2005) stated that the treatment of large, advanced osteochondritis dissecans of the elbow is controversial. To determine if better results could be obtained using osteochondral autografts, these researchers retrospectively reviewed the results in 10 young athletes (mean age of 14.3 years with a range of 12 to 17 years) who were followed-up for a mean of 25.5 months (range of 18 to 45 months). After abrasion of the fragments, cylindrical osteochondral bone plugs were transferred from a lateral femoral condyle. They were evaluated clinically by the Japanese Orthopedic Association (JOA) elbow score and radiologically by radio-capitellar congruity. All patients achieved bony union in 3 months. The average JOA elbow score was 80.6 points before surgery and improved to 93.8 points at follow-up. The average percentage of radio-capitellar congruity was 35.7 % before surgery and improved to 64.2 % at follow-up. Clinical and radiological results were excellent in 8 patients and poor in 2. Poor results may be dependent on pre-existing osteoarthritis and technical difficulty related to the location of the lesion. In 8 patients, a durable load-bearing elbow was obtained with this procedure, which made hyaline-like cartilage resurfacing with healthy subchondral bony support possible. The authors concluded that osteochondral autograft is a reasonable surgical option for an advanced lesion of osteochondritis dissecans of the elbow, although long-term follow-up is needed to ascertain if the early results persist. The scientific evidence supporting the use of osteochondral autografts to repair the elbow and shoulder consists mainly of single case reports. The authors stated that currently available published studies are small, non-randomized, and lack long-term follow-up. Thus, further investigation is needed to ascertain the clinical value of osteochondral autografts for repairing the elbow and shoulder.
The Institute for Clinical Effectiveness and Health Policy (Pichon-Riviere et al, 2006) evaluated the literature on the effectiveness of OATS and mosaicplasty on ankle bone cartilage lesions. The assessment concluded: "There is still not enough evidence available on the efficacy of mosaicplasty or the OATS procedure for the treatment of talus cartilage joint lesions. There is very little published about the assessment of the osteochondral grafting viability. There is not enough evidence determining whether the tissues coming from places that do not carry weight could absorb the stress of weight bearing areas, neither the degree of donor site morbidity. Patient inclusion criteria are not well settled in the literature, and there is no uniform consensus on the procedure's indication. ...Only well designed prospective clinical trials with long follow-ups could determine the efficacy of these procedures to relieve the symptoms caused by osteochondral lesions, improve joint function and achieve the final objective, which is the prevention of secondary arthrosis."
Easley and Scranton (2003) stated that long-term outcome of the OATS procedure for osteochondral lesions of the talus is not yet available.
Aurich and colleagues (2008) noted that ankle sprains are one the most common injuries of the lower limb. Fractures, ligamentous lesions, and cartilaginous damage are often associated. Nevertheless, the injury is often mis-judged and concomitant chondral lesions are assessed late. In the case of a symptomatic osteo-cartilaginous lesion of the talus, which can be illustrated by MRI or X-ray, operative intervention is indicated. Methods such as microfracturing, mosaicplasty, and autologous chondrocyte transplantation (ACT) are in clinical use. The latter is well-known and being established as the treatment of choice for large cartilage defects in the knee. Due to the good results in the knee and the technological improvements (three-dimensional tissue constructs seeded with autologous chondrocytes) this method is being increasingly applied for cartilage lesions of the talus. In contrast to the mosaicplasty, donor site morbidity is low and the size of the defect is not a limiting factor. The current studies about ACT of the talus show a stable repair of the defect with mostly hyaline-like cartilage and high patient satisfaction. Therefore, the procedure can be recommended for lesions less than 1 cm2. Concomitant treatment of post-traumatic deformities (malalignment), ligamentous instabilities, and especially the reconstruction of bony defects are compulsory.
In a systematic review, Magnussen et al (2008) examined if ACT or osteochondral autograft transfer yields better clinical outcomes compared with one another or with traditional abrasive techniques for treatment of isolated articular cartilage defects and if lesion size influences this clinical outcome. These researchers performed a literature search and identified 5 randomized, controlled trials and 1 prospective, comparative trial evaluating these treatment techniques in 421 patients. The operative procedures included ACT, osteochondral autograft transfer, matrix-induced ACT, and microfracture. Minimum follow-up was 1 year (mean of 1.7 years; range of 1 to 3 years). All studies documented greater than 95 % follow-up for clinical outcome measures. No technique consistently had superior results compared with the others. Outcomes for microfracture tended to be worse in larger lesions. All studies reported improvement in clinical outcome measures in all treatment groups when compared with pre-operative assessment; however, no control (non-operative) groups were used in any of the studies. The authors stated that a large prospective trial investigating these techniques with the addition of a control group would be the best way to definitively address the clinical questions.
Zengerink and colleagues (2010) compared the effectiveness of treatment strategies for osteochondral defects (OCD) of the talus. Electronic databases from January 1966 to December 2006 were systematically screened. The proportion of the patient population treated successfully was noted, and percentages were calculated. For each treatment strategy, study size weighted success rates were calculated. A total of 52 studies described the results of 65 treatment groups of treatment strategies for OCD of the talus: 1 randomized clinical trial was identified; 7 studies described the results of non-operative treatment, 4 of excision, 13 of excision and curettage, 18 of excision, curettage and bone marrow stimulation (BMS), 4 of an autogenous bone graft, 2 of trans-malleolar drilling (TMD), 9 of OATS, 4 of ACI, 3 of retrograde drilling, and 1 of fixation. OATS, BMS and ACI scored success rates of 87 %, 85 %, and 76 %, respectively. Retrograde drilling and fixation scored 88 % and 89 %, respectively. Together with the newer techniques OATS and ACI, BMS was identified as an effective treatment strategy for OCD of the talus. Because of the relatively high cost of ACI and the knee morbidity seen in OATS, the authors concluded that BMS is the treatment of choice for primary osteochondral talar lesions. However, due to great diversity in the articles and variability in treatment results, no definitive conclusions can be drawn. They stated that further sufficiently powered, randomized clinical trials with uniform methodology and validated outcome measures should be initiated to compare the outcome of surgical strategies for OCD of the talus.
Lu and Hame (2005) noted that treatment options for chondral and osteochondral defects of the patella have been few and results have been inconsistent at best. Autologous osteochondral transplantation presents a new way to revisit these patellar defects. These researchers reported the case of a young female softball player with a simple cyst in the patella and an osteochondral defect that serves as the indication for autograft osteochondral transplantation.
Nho et al (2008) stated that autologous osteochondral transplantation (AOT) has been successfully used in the femoral condyle and trochlea and is an attractive treatment option for full-thickness patellar cartilage lesions. These investigators hypothesized that patients treated with AOT for the repair of symptomatic, isolated patellar cartilage lesions will demonstrate improvement in functional outcomes and post-operative MRI appearance. In a case-series study, patients with focal patellar cartilage lesions treated with AOT were prospectively followed. The mean age at the time of surgery was 30 years. Clinical assessment was performed with the International Knee Documentation Committee (IKDC), activities of daily living of the Knee Outcome Survey (ADL), and Short Form-36 (SF-36) at baseline and most recent follow-up. Magnetic resonance imaging was used to evaluate the cartilage repair morphologic characteristics in 14 cases. Twenty-two patients met the study criteria with a mean follow-up of 28.7 months (range of 17.7 to 57.8 months). The mean patellar lesion size was 165.6 +/- 127.8 mm(2), and the mean size of the donor plug was 9.7 +/- 1.1 mm in diameter with 1.8 +/- 1.4 plugs/defect. The mean pre-operative IKDC score was 47.2 +/- 14.0 and improved to 74.4 +/- 12.3 (p = 0.028). The mean pre-operative ADL score was 60.1 +/- 16.9 and increased to 84.7 +/- 8.3 (p = 0.022). The mean SF-36 also demonstrated an improvement, from 64.0 +/- 14.8 at baseline to 79.4 +/- 15.4 (p = 0.059). Nine patients underwent concomitant distal re-alignment and demonstrated improvement between pre-operative and post-operative outcomes scores, but these differences were not statistically significant. Magnetic resonance imaging appearance demonstrated that all plugs demonstrated good (67 % to 100 %) cartilage fill, 64 % with fissures greater than 2 mm at the articular cartilage interface, 71 % with complete trabecular incorporation, and 71 % with flush plug appearance. The authors concluded that patellar AOT is an effective treatment for focal patellar chondral lesions, with significant improvement in clinical follow-up. This study suggested that patients with patellar mal-alignment may represent a subset of patients who have a poor prognostic outlook compared with patients with normal alignment. This was a small case-series study; its findings need to be validated by well-designed studies.
Colvin and West (2008) stated that recurrent patellar instability can result from osseous abnormalities, such as patella alta, a distance of greater than 20 mm between the tibial tubercle and the trochlear groove, and trochlear dysplasia, or it can result from soft-tissue abnormalities, such as a torn medial patellofemoral ligament or a weakened vastus medialis obliquus. Non-operative treatment includes physical therapy, focusing on strengthening of the gluteal muscles and the vastus medialis obliquus, and patellar taping or bracing. Acute medial-sided repair may be indicated when there is an osteochondral fracture fragment or a retinacular injury. The recent literature does not support the use of an isolated lateral release for the treatment of patellar instability. A patient with recurrent instability, with or without trochlear dysplasia, who has a normal tibial tubercle-trochlear groove distance and a normal patellar height may be a candidate for a reconstruction of the medial patello-femoral ligament with autograft or allograft. Distal re-alignment procedures are used in patients who have an increased tibial tubercle-trochlear groove distance or patella alta. The degree of anteriorization, distalization, and/or medialization depends on associated arthrosis of the lateral patellar facet and the presence of patella alta. Associated medial or proximal patellar chondrosis is a contraindication to distal realignment because of the potential to overload tissues that have already undergone degeneration.
Matricali et al (2010) stated that in order to perform an osteochondral autologous transplantation (OAT) or an autologous chondrocyte implantation (ACI), the integrity of healthy intact articular cartilage at a second location needs to be violated. This creates the possibility for donor site morbidity. Only recently have any publications addressed this issue. These researchers reviewed the current knowledge on donor site morbidity after an OAT or an ACI. Reports were identified by searching Medline and PubMed up to March 2010. Donor site morbidity was described mostly considering a clinical outcome, both in a qualitative (parameters in history or physical examination) and/or quantitative way (knee status reported by means of a numerical score). An increasing rate of problems is noted when using quantitative instead of qualitative parameters, and when donor site morbidity is the focus of attention, affecting up to more than 50 % of the patients, especially for an OAT procedure. The decision to harvest an osteochondral or cartilage biopsy to perform a repair procedure should therefore be taken with caution. This also underscores the need for further research to identify safe donor sites or to develop techniques that eliminate the need for a formal biopsy completely.
The Washington State Health Care Authority Technology Assessment Program (2011) commissioned a technology assessment of Osteochondral Allograft Transplantation and Autograft Transfer System (OATS/mosaicplasty). In commissioning the assessment, the Program stated: "Significant questions remain about the safety, efficacy and effectiveness, and cost effectiveness of OATS/mosaicplasty cartilage surgery. The choice of suitable patients for OATS/mosaicplasty surgery is controversial because the size and number of damage sites for which it is functional are not well defined, because the harvesting of cartilage from another site or cadaver tissue adds risk and healing issues, and because other, less invasive procedures may be equally effective in the short term (autologous chondrocyte injection). Effectiveness questions particularly center on whether the potential beneficial outcomes of long term pain and functional improvement, prevention of osteoarthritis or further joint deterioration occur with this surgical intervention."
The systematic evidence review prepared for the Washington State Health Care Authority (Skelly, et al., 2011) reported that two small randomized controlled trials (RCTs) (level of evidence IIb) in younger populations compared OAT with microfracture and three RCTs (or quasi RCTs, level of evidence IIb) compared OAT/mosaicplasty with ACI in general (older)populations. The review found substantial differences in patient populations, lesion sizes, comparators and outcomes measures used across studies, making it difficult to draw overall conclusions. Compared with microfracture (MF), OAT was associated with better patient-reported (based on International Cartilage Repair Society (ICRS) cartilage repair assessment), and clinician-reported (based on the Hospital for Special Surgery (HSS) Score) functional outcomes in young athletes and children based on two small RCTs (total n = 104) (citing Gudas, et al., 2005; Gudas, et al., 2009). For comparisons with ACI, three poor quality RCTs in general (older) populations reported functional outcomes. Two small, poor quality RCTs suggest that function based on patient-reported outcomes (Lysholm Knee Scoring Scale and a modification of it) was better for OAT compared with ACI; however statistical significance was reached in only one of the RCTs (n = 40) (citing Horas, et al., 2003) and in the other RCT (citing Dozin, et al., 2005), conclusions are difficult given the significant loss to follow-up (50%). The largest RCT (n = 100) (citing Bentley, et al., 2003) reported that a significantly smaller proportion of participants receiving mosaicplasty had excellent or good results based on the author’s modification of the Cincinnati Rating Scale. One of the smaller RCTs reported no significant differences in the Meyer score. Both these studies included substantial proportions of participants who had prior surgeries (94% and 45% respectively).
The assessment (2011) found that there were substantial differences across studies with respect to populations, lesion sizes, comparators and outcomes measures making it difficult to draw overall conclusions. The indications for OAT versus mosaicplasty, autograft versus allograft appear to be based on case series primarily. The majority of studies are in populations less than 50 years of age. The overall quality of the literature is poor, particularly with respect to evaluation of autograft.
The Washington State Health Care Authority Agency Medical Directors (2011) concluded that there is some evidence of benefit of osteochondral transplantation procedures in cases failing conservative management. The agency noted that the evidence of effectiveness and efficacy of osteochondral transplantation procedures is of low quality and shows variable outcomes. The agency found that the case selection criteria for osteochondral transplantation procedures is uncertain and that there are no long-term outcomes data. They stated that osteochondral transplantation is an evolving technology with a weak evidence base, and that the long-term safety and effectiveness are uncertain. They noted the potential for overuse and misuse given the lack of patient and technique selection criteria. The agency recommended coverage of osteochondral transplantation procedures only for the knee (and possibly talus) in person less than 50 years of age who have failed conservative management and who do not have arthritis.
The Washington State Health Care Authority Health Technology Clinical Committee (2012) has concluded that osteochondral allograft/autograft transplantation for the knee is a covered benefit when the following conditions are met: 1) age less than 50 years, older at the discretion of the agency; 2) excluding malignancy, degenerative and inflammatory arthritis in the joint; and 3) single focal full-thickness articular cartilage defect. The Committee stated that osteochondral allograft/autograft transplantation is not covered for joints other than the knee.
Non-autologous mosaicplasty has been proposed as an alternative to conventional mosaicplasty. Non-autologous mosaicplasty entails a series of small holes drilled into the area of the osteochondral defect. The holes are then packed with a synthetic polymer (as a bone void filler); providing a scaffold for the growth of new bone. The synthetic graft is gradually resorbed by the body and replaced with bone. The proposed advantage of this procedure over conventional osteochondral autograft transplantation is the elimination of the need for harvesting bone and cartilage from a donor graft site. However, there is currently insufficient evidence to support the use of non-autologous mosaicplasty for repair of osteochondral defects.
Minced cartilage repair is considered a 2nd generation technique that does not require in-vitro cell expansion and is described as a single-staged minimally invasive procedure. The procedure uses minced pieces of cartilage seeded over a scaffold that allows for even distribution of the chondrocytes to expand within the defect providing structural as well as mechanical protection. The first clinical application of the minced cartilage technique was the cartilage autograft implantation system (CAIS) developed by DePuy Mitek. A second technology, DeNOVO NT Graft ("Natural Tissue Graft"; Zimmer Inc., Warsaw, IN/ISTO Technologies Inc.) is another application for cartilage regeneration using minced donated juvenile (less than 12 years of age) fresh allograft cartilage tissue obtained from human cadavers. Randomized trials that compare the outcomes of minced articular cartilage repair with standard methods have not been published. Well-designed studies are needed to establish the safety and effectiveness of this approach over standard methods of cartilage repair.
Lu and colleagues (2006) stated that traumatic articular cartilage injuries heal poorly and may predispose patients to the early onset of osteoarthritis. One current treatment relies on surgical delivery of autologous chondrocytes that are prepared, prior to implantation, through ex-vivo cell expansion of cartilage biopsy cells. The requirement for cell expansion, however, is both complex and expensive and has proven to be a major hurdle in achieving a widespread adoption of the treatment. These researchers presented evidence that autologous chondrocyte implantation can be delivered without requiring ex-vivo cell expansion. The proposed improvement relies on mechanical fragmentation of cartilage tissue sufficient to mobilize embedded chondrocytes via increased tissue surface area. The authors’ outgrowth study, which was used to demonstrate chondrocyte migration and growth, indicated that fragmented cartilage tissue is a rich source for chondrocyte re-distribution. The chondrocytes outgrown into 3-D scaffolds also formed cartilage-like tissue when implanted in mice homozygous for the scid mutation (SCID mice). Direct treatment of full-thickness chondral defects in goats using cartilage fragments on a resorbable scaffold produced hyaline-like repair tissue at 6 months. Thus, delivery of chondrocytes in the form of cartilage tissue fragments in conjunction with appropriate polymeric scaffolds provides a novel intra-operative approach for cell-based cartilage repair
An alternative to allografting that has been proposed by some researchers is the synthetic graft. Synthetic bone void fillers can be categorized into 3 groups: (i) ceramics, (ii) composites, and (iii) polymers. Ceramics are osteo-conductive and are composed of calcium; total degradation time depends on the composition. Composite grafts combine osteo-conductive matrix with bioactive agents that provide osteo-inductive and osteogenic properties. Polymers are osteo-conductive and when used with marrow could provide a biodegradable osteo-inductive implant for repairing large defects.
Baker and colleagues (2011) noted that the development of synthetic bone graft substitutes is an intense area of research due to the complications associated with the harvest of autogenous bone and concerns about the supply of allogeneic bone. Porous resorbable polymers have been used extensively in hard tissue engineering applications, but currently lack load-bearing capacity.
Vundelinckx et al (2012) reported that under arthroscopic control and guided by fluoroscopy, a TruFit Plug was successfully implanted to repair an osteochondral lesion of the head of the femur. The procedure was evaluated clinically using the HOOS score and MRI of the hip. The short-term (6 months) clinical results were encouraging: the HOOS score improved clearly and the patient was satisfied. Interpretation of MRI images in the early post-operative period was very difficult: in the early months history and clinical examination prevail in the evaluation.
Joshi et al (2012) evaluated prospectively short- and medium-term results in patients with osteochondral patellar defects treated with synthetic re-absorbable scaffolds. Patient outcome scores (Short Form 36 [SF-36] and Knee injury and Osteoarthritis Outcome Score [KOOS]), demographics, prior surgeries, and data from a physical examination were collected at baseline (before implantation) and at 6, 12, and 24 months after surgery. Defect characteristics were collected during implantation. Diagnosis and monitoring were performed by MRI. A total of 10 patients with a mean age of 33.3 years (range of 16 to 49 years) were evaluated prospectively at 24 months' follow-up. The number of plugs used for each patient ranged from 1 to 4. At 1-year follow-up, the results were satisfactory in 8 of 10 patients, and poor in 2, according to clinical assessment (KOOS, visual analog scale, and SF-36). At 18 months of follow-up, all patients except 1 complained of pain and knee swelling. Re-operation rate for implant failure at final follow-up was 70 %. Magnetic resonance imaging at final follow-up showed a cylindrical cavity of fibrous tissue instead of subchondral bone restoration. The authors concluded that a synthetic implant can improve symptoms and joint function, especially for small lesions, only for a short period of time. However, 2 years of monitoring has shown its failure in restoring the subchondral bone despite the formation of predominant hyaline cartilage from synthetic resorbable scaffolds. Under current conditions and according to the authors’ experience, they do not recommend TruFit synthetic implants for osteochondral patellar defects in active patients.
Hindle et al (2014) evaluated functional outcome of patients using the EQ-5D, Knee Injury and Osteoarthritis Outcome Score (KOOS) and Modified Cincinnati scores at follow-up of 1 to 5 years. There were 66 patients in the study (35 TruFit and 31 mosaicplasty): 44 males and 22 females with a mean age of 37.3 years (SD of 12.6). The mean body mass index (BMI) was 26.8; 36 articular cartilage lesions were due to trauma, 26 due to osteochondritis dissecans and 3 due to non-specific degenerative change or unknown. There were no significant differences between the 2 groups in terms of age, sex, BMI, defect location, or etiology. The median follow-up was 22 months for the TruFit cohort and 30 months for the mosaicplasty group. There was no significant difference in the requirement for re-operation. Patients undergoing autologous mosaicplasty had a higher rate of returning to sport (p = 0.006), lower EQ-5D pain scores (p = 0.048) and higher KOOS activities of daily living (p = 0.029) scores. Sub-group analysis showed no difference related to the number of cases the surgeon performed. Patients requiring re-operation had lower outcome scores regardless of their initial procedure. The authors concluded that the findings of this study demonstrated significantly better outcomes using 2 validated outcome scores (KOOS, EQ-5D), and an ability to return to sport in those undergoing autologous mosaicplasty compared to those receiving TruFit plugs.
Quarch et al (2014) examined if the potential donor site morbidity for large defects could be reduced by means of TruFit plugs. An autologous OCT was performed in 37 patients and the cylinders were received from the dorsal medial femoral condyle. The donor site defects of 21 patients (average defect size 5.5 cm(2)) were filled with artificial TruFit cylinders (study group); the donor site defects (average defect size 4.6 cm(2)) were left untreated for 16 patients. In the study group, the Tegner, Western Ontario and McMaster Universities (WOMAC), knee society score, and visual analog scale pain scores improved from pre-operatively 3.2 (± 0.8), 60.9 (± 41.6), 133.6 (± 27.1), and 4.8 (± 2.3) points, respectively, to 3.9 (± 0.6), 35.5 (± 27.1), 177.8 (± 16.6), and 3.3 (± 2.9) points, respectively, at the time of the second follow-up; the control group's pre-operative score values came to 2.8 (± 0.9), 73.3 (± 50.2), 123.8 (± 41.5), and 5.3 (± 2.7) points, respectively, and changed to 3.6 (± 0.8), 41.4 (± 28.8), 179.3 (± 17.5), and 3.1 (± 2.0) points, respectively, at the time of the second follow-up. The smaller the initial chondral defect was in the study group, the better the WOMAC score values became (p < 0.05). The modified Henderson score at the study group's donor sites improved from 19.2 (± 3.3) to 13.7 (± 2.1) points (p < 0.001); the control group's score values for the donor sites were 18.3 (± 3.4) and 15.4 (± 4.4) points (p = 0.0015). The authors concluded that OCT is an effective therapy even for large chondral defects greater than 3 cm(2). By filling the defects with TruFit implants, no clinical improvements could be found since the donor site morbidity was already low anyway. However, the regeneration of defects filled with TruFit implants took more than 2 years.
Gelber et al (2014) evaluated the relationship between MRI findings and functional scores of patients with osteochondral lesions of the knee treated with TruFit. Patients were evaluated with MOCART score for MRI assessment of the repair tissue. Knee injury and Osteoarthritis Outcome Score, SF-36 and VAS were used for clinical evaluation. Correlation between size of the treated chondral defect and functional scores was also analyzed. A total of 57 patients with median follow-up of 44.8 months (range of 24 to 73) were included. KOOS, SF-36 and VAS improved from a mean 58.5, 53.9 and 8.5 points to a mean 87.4, 86.6 and 1.2 at last follow-up (p < 0.001). Larger lesions showed less improvement in KOOS (p = 0.04) and SF-36 (p = 0.029). Median Tegner values were restored to pre-injury situation (5, range of 2 to 10). Mean MOCART score was 43.2 ± 16.1. Although the cartilage layer had good integration, it showed high heterogeneity and no filling of the subchondral bone layer. The authors concluded that TruFit failed to restore the normal MRI aspect of the subchondral bone and lamina in most cases. The appearance of the chondral layer in MRI was partially re-established. This unfavorable MRI appearance did not adversely influence the patient's outcome in the short-term and they restored their previous level of activity. There was an inverse linear relationship between the size of the lesion and the functional scores.
There is currently insufficient evidence to support the safety and effectiveness of synthetic resorbable polymers as an alternative to allograft or autograft for the repair of osteochondral defects.
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