Hyaline cartilage is a flexible, elastic tissue that covers the articular surface of bone and allows smooth articulation of the joint. Chondral injuries of a joint may present with pain, swelling, clicking, and joint instability. Even when these injuries are small, they often progress to more extensive damage and degenerative conditions. Treatment is difficult due to the limited repair capability of articular cartilage.
Osteochondral defects (OCD) of the knee or ankle often fail to heal on their own and are often associated with pain, disability, loss of function, and long-term complications of osteoarthritis. Various methods of cartilage resurfacing have been investigated, including marrow-stimulation techniques such as subchondral drilling, microfracture (MF), and abrasion arthroplasty. These procedures are considered standard therapies and attempt to restore the articular surface by including the growth of fibrocartilage into the chondral defect. However, fibrocartilage does not share the same biochemical properties as hyaline cartilage. Compared to the original hyaline cartilage, fibrocartilage has less capability to withstand shock or shearing force. It can also degenerate over time, which results in symptom recurrence. Therefore, various treatment strategies for chondral resurfacing with hyaline cartilage have been investigated.
Osteochondral autograft transplantation (OAT) (also known as osteochondral autograft transplant system [OATS] or autogenous osteochondral mosaicplasty) involves harvesting osteochondral cylinders that include overlays of normal articular hyaline cartilage from minimal-weight-bearing areas of the knee and transplanting them into articular sites. Lesions can be treated using one osteochondral plug or a series of small plugs that are press-fitted in a mosaic-like pattern (mosaicplasty). The use of multiple grafts in the mosaicplasty technique allows more tissue to be transplanted and permits contouring of the new surface, thus avoiding alteration of the biomechanics of the joint. When multiple grafts are used, the defect is thought to fill with up to 80 percent hyaline cartilage, but the procedure requires a high degree of surgical skill to recreate the normal curvature of the femoral condyle. Donor sites fill with fibrocartilage and, when the sites are small, have not resulted in unexpected morbidity.
Depending on the size of the lesion being treated, OAT can either be performed as open surgery or arthroscopy. Any malalignment or ligamentous instability that may have produced or contributed to the lesion should be corrected prior to, or concurrent with, treatment of the defect and included in the rehabilitation plan. Rehabilitation can take up to 12 weeks, and continuous passive motion may be used postoperatively to improve the joint surface contour.
Limited donor sites, and the potential for morbidity at the donor site, restrict the size of the lesion that can be treated with OAT. Although some clinicians advocate treating defects up to 4 cm, general agreement in the published literature confirms that OAT should be reserved for lesions between 1 and 3 cm² that are surrounded by healthy articular cartilage. Based on literature, recommendations from relevant medical societies, and clinical input, OAT should be performed only on young individuals who have reached skeletal maturity (e.g., 15 years of age or older) and individuals who are too young to be considered an appropriate candidate for total knee arthroplasty or other reconstructive knee surgery (e.g., 55 years of age or younger), who have full-thickness, unipolar defects of the femoral condyle or patellar articular surface in stable knees with intact menisci. Contraindications for OAT include degenerative or rheumatoid joint disease and diffuse lesions or joint space narrowing. Knee instability or malalignment is also considered a contraindication if it will not be corrected at the time of surgery.
According to the American Academy of Orthopaedic Surgeons (AAOS), most candidates eligible for articular cartilage restoration are young adults with a single injury or lesion. Older individuals, or those with many lesions in one joint, are less likely to benefit from osteochondral autograft transplantation.
OAT is primarily employed to treat OCD of the knee. However, treatment strategies for OCD of the talus (ankle) have substantially increased over the last decade. These include non-surgical treatments with rest or cast immobilization, surgical excision of the lesion, excision and curettage, excision combined with curettage and drilling/microfracturing (i.e., bone marrow stimulation, BMS), placement of an autogenous (cancellous) bone graft, antegrade (transmalleolar) drilling (TMD), retrograde drilling, fixation, and newer techniques such as OAT and autologous chondrocyte implantation (ACI). The last two techniques focus on replacement and regeneration of the hyaline cartilage, respectively. The goal of these treatment strategies is to diminish symptoms such as pain and swelling, while improving function.
OAT has been introduced as an alternative to allografts for the treatment of talar OCDs. It is a reconstructive bone grafting technique that uses one or more cylindrical osteochondral grafts from the less weight-bearing periphery of the ipsilateral knee to transplant them into the prepared defect site on the talus. The goal is to reproduce the mechanical, structural, and biochemical properties of the original hyaline articular cartilage which has become damaged. It can be performed using an open or arthroscopic approach.
PEER-REVIEWED LITERATURE
OSTEOCHONDRAL DEFECTS OF THE KNEE
In a prospective comparative study, Bentley et al. (2003) evaluated 100 individuals with a symptomatic lesion of the articular cartilage in the knee who were randomized to undergo either OAT (n=42) or ACI (n=58). The mean age of the study participants was 31.3 years (16 to 49). The mean duration of symptoms was 7.2 years with a mean follow-up of 19 months (12 to 26). Outcome measurements included objective clinical assessment and functional assessment using modified Cincinatti and Stanmore scores. Eighty-eight percent of individuals had excellent or good results after ACI compared with 69% of individuals after OAT. Arthroscopy at 1-year follow-up demonstrated excellent or good results in 82% of individuals after ACI and in 34% of individuals after OAT. All five patellar OAT mosaicplasties failed. The authors concluded that ACI was superior to OAT for the repair of articular defects in the knee. The study is limited in its small sample size and relatively short follow-up.
In a retrospective study, Miniaci et al. (2007) reported on the results of mosaicplasty in 20 symptomatic individuals with OCD. The mean age was 14.3 years (12 to 27), and all individuals had failed previous non-surgical treatment. The osteochondral lesions were grade 2 (n=16), grade 3 (n=3), or grade 4 (n=1) OCDs (according to the International Cartilage Repair Society, ICRS). At 24-month post-operative follow-up, all but 1 individual were assessed as normal. Pain was reduced from 8.2 on the visual analog scale (VAS) pain score preoperatively to 0.8 at 6 months and to 0 at 1 year. By 18 months, all individuals had returned to full activities. This study is limited by its small sample size and short-term follow-up, particularly given the age of the participants.
In a retrospective study, Marcacci et al. (2007) evaluated the outcome of OAT in individuals with full-thickness chondral knee lesions (n=30). The mean age was 29.3 years (17 to 46) with grade 3 and 4 OCD (> 2.5 cm2) of the weight-bearing surface of the medial or lateral femoral condyle. Nineteen individuals received associated procedures during the surgery: 9 ACL reconstructions, 13 meniscectomies and 1 medial collateral ligament repair. Patients were followed for 2 and 7 years. At 7-year follow-up, 76.7% of individuals were considered to be normal or nearly normal using the International Knee Documentation Committee (IKDC) subjective and objective evaluation scores. Magnetic resonance imaging (MRI) evaluations were performed on 24 of the individuals at 7 years. Complete filling of the lesion was maintained at 7 years in 62.5% of study participants, integration of the grafted cartilage occurred in 75%, and complete bone integration occurred in 95.9%. In all cases, the donor site was detectable, but covered. Seven individuals returned to sports at pre-injury level, 14 at a lower level, and 9 no longer participated in sports. This was decreased from the 2-year follow-up when 22 individuals had returned to sports at the pre-injury level, 4 at a lower level, and 4 had not returned to sports activity. However, the authors noted that this may have been attributable to an increase in age during the follow-up time. There was a statistically significant improvement on the Tegner scale at both 2 and 7 years (p <0.0005) from preoperative level; however, the new level of sports activity was significantly lower than the pre-injury level (p = 0.002). The authors concluded that the results of OAT as a valid solution for the treatment of small grade 3 or 4 OCD are promising at medium- to long-term follow-up. The study is limited in its small sample size and is potentially confounded by the concomitant procedures performed during surgery.
In a prospective randomized controlled trial, Gudas et al. (2009) compared the outcomes of arthroscopic mosaic-type OAT and MF procedures for the treatment of OCD of the femoral condyles in the knee joints of children (n=50) under the age of 18 years. The mean age was 14.3 years (12 to 18) at time of randomization to either the OAT or the MF procedure. Only children with grade 3 or 4 OCD in the medial or lateral femoral condyle were included in the study. Ninety-four percent (n=47) of individuals were available for follow-up. The mean duration of symptoms was 23.54 ± 4.24 months and the mean follow-up was 4.2 years (3 to 6). None of the children had prior surgical interventions to the affected knee. Children were evaluated using ICRS score, X-rays, MRI, and second-look arthroscopies. After 1 year, both groups had significant clinical improvement (p < 0.05) and ICRS functional and objective assessment indicated that 92% of individuals (n=23) had good or excellent results after OAT compared with 86% of individuals (n=19) after MF. After a mean of 4.2 years follow-up, 83% of individuals (n=19) had good or excellent results after OAT compared with 63% of individuals (n=12) after MF. The authors concluded that at an average of 4.2 years of follow-up, mosaic-type OAT has shown significant superiority over MF for the treatment of OCD in the knee in children under the age of 18 years. Limitations of the study include its small sample size and relatively short follow-up given the age of its study population.
In a prospective randomized controlled trial, Gudas et al. (2009) compared the outcomes of mosaic-type osteochondral OAT and MF procedures for the treatment of articular cartilage defects of the knee joint in young active athletes. Only athletes competing in competitive sports at the regional or national levels were included. Patients had a mean age of 24.3 years (15 to 40) with a symptomatic lesion of the articular cartilage in the knee. Ultimately, 95% of individuals (n=57) were available for follow-up. Athletes were randomized to either the OAT group (n=28) or MF group (n=29). Mean duration of symptoms was 21.32 ± 5.57 months, and individuals were followed for a mean of 37.1 months (36 to 38 months). Patients were evaluated using ICRS scores, radiograph, MRI, and clinical assessment. An independent observer performed a follow-up examination after 6, 12, 24, and 36 months. At 12.4 months postoperatively, arthroscopy with biopsy for histological evaluation was carried out. After 37.1 months, both groups had significant clinical improvement (p < 0.05). Ninety-six percent of individuals had excellent or good results after OAT compared with 52% of individuals after MF (p < 0.001). At 12, 24, and 36 months after surgery, ICRS scores showed statistically significantly better results in the OAT group (p = 0.03; p = 0.006; p = 0.006, respectively). Younger athletes did better in both groups. Biopsy specimens obtained from 58% of the individuals indicated that histological evaluation of repair showed better scores for the OAT group (p < 0.05). MRI evaluation indicated excellent or good repairs in 94% of individuals after OAT compared with 49% of individuals after MF. Ninety-three percent of individuals (n=26) who were treated with OAT returned to sports activities at pre-injury levels compared with 52% of individuals (n=15) after MF. The authors concluded that in young, active athletes under the age of 40, treatment with OAT showed superiority over MF for the repair of articular cartilage defects in the knee. Limitations of the study include its small sample size and a relatively short 3-year follow-up in this young population. The authors called for long-term follow-up studies to assess the durability of articular cartilage repair in young active athletes.
In a literature review, Cole et al. (2009) evaluated the current state of surgical management of articular cartilage defects in the knee. The authors noted that the goals of surgical treatment are to provide pain relief and improve joint function, allowing individuals to potentially return to higher levels of activity. In general, surgical options can be grouped into three categories: palliative (arthroscopic debridement and lavage), reparative (marrow stimulation techniques), and restorative (osteochondral grafting and autologous chondrocyte implantation). Treatment algorithms should consist of a graduated surgical plan where the least destructive and least invasive option is performed first. OAT is limited by the amount of donor tissue available in the knee because donor site morbidity increases as more tissue is harvested. OAT is best for small lesions (< 2 cm2), but good clinical results have been reported with lesions between 2 and 4 cm2. Postoperatively, individuals should be protected from weight-bearing for six weeks and use a continuous passive motion machine six hours per day. The authors concluded that the use of OAT for the treatment of small and medium focal chondral and osteochondral defects of the knee is supported by several multi-center studies.
In a systematic review, Bekkers et al. (2009) identified the parameters for valid treatment selection in the repair of articular cartilage lesions of the knee. The authors included a total of 4 randomized controlled trials in their review and found that lesion size, activity level, and age were the influencing parameters for the outcome of articular cartilage repair surgery. Lesions greater than 2.5 cm2 should be treated with either ACI or OAT, while MF is a good first-line treatment option for smaller lesions. Active individuals showed better results after ACI or OAT when compared to MF. Younger individuals under 30 years of age seemed to benefit more from any form of cartilage repair surgery than those over 30 years of age. The authors concluded that the influencing parameters for the outcome of articular cartilage repair surgery should direct surgeons toward evidence-based treatment of articular cartilage lesions of the knee.
In a retrospective study, Solheim et al. (2010) evaluated short- and medium-term results of the treatment of articular cartilage defects of the knee with OAT mosaicplasty in 69 individuals with symptomatic articular cartilage defects. The median age was 33 years and median follow-up was 7 years (5 to 9). Outcome measurements included Lysholm score and VAS pain scores. Preoperative measurements were collected prior to surgery, 12 months postoperatively, and at a median of 7 years follow-up. The mean Lysholm score and VAS pain scores improved from 48 and 62, respectively, to 81 and 24 at 12 months follow-up (p < 0.001). From 12 months postoperatively, the Lysholm and VAS pain scores deteriorated to 68 and 32, respectively, at the 5- to 9-year follow-up (p < 0.001 and p = 0.018, respectively). Eighty-eight percent of individuals (n=61) stated that they would have undergone the surgery again. The authors concluded that OAT mosaicplasty leads to improvement of symptoms and function at short- and medium-term follow-up, though deterioration of results is observed at the medium-term. The study is limited in its small sample size and relatively short follow-up.
In a retrospective comparative study, Krych et al. (2012) compared the general health outcomes, knee function, and Marx Activity Rating Scale score for individuals treated with OAT or MF for symptomatic chondral defects of the femoral condyles or trochlea. Forty-eight individuals were included in each treatment group with a mean age of 29.7 years in the OAT group and 32.5 years in the MF group. Patients were evaluated at baseline, one, two, three, and five years postoperatively with the use of validated clinical outcome measures including the IKDC, Knee Outcome Survey activities of daily living, and Marx Activity Rating Scale. At the time of the latest follow-up, both groups demonstrated statistically significant increases in IKDC and Knee Outcome Survey activities of daily living. These scores did not differ significantly between the two groups at any of the follow-up time points. However, the OAT group demonstrated a statistically significant greater improvement in the Marx Activity Rating Scale scores from baseline to the 2-year (p = 0.001), 3-year (p = 0.03), and 5-year (p = 0.02) time points compared with the MF group. The authors concluded that both MF and OAT offer similar clinical outcomes at intermediate follow-up. However, individuals treated with OAT maintained a superior level of athletic activity compared with individuals treated with MF. Limitations of the study include its small sample size and relatively short follow-up time.
OSTEOCHONDRAL DEFECTS OF THE TALUS
Injuries to the articular surface of the talar dome in the ankle joint are commonly called osteochondral lesions of the talus (OLT). Other terms that refer to the same general process are osteochondral defects (OCD), osteochondritis dissecans, and transchondral fracture. OLT are present in up to 70% of acute ankle sprains and fractures. OLT have become increasingly more recognized with the advancements in cartilage-sensitive diagnostic imaging modalities. However, OLT still only represent approximately 4% of all osteochondral lesion cases with the largest majority of osteochondral lesions occurring in the knee and the elbow.
In a meta-analysis, Tol et al. (2000) investigated the results of different treatment strategies for OCD of the talus. The authors included 32 studies describing the results of non-surgical and surgical treatment strategies for talar OCD. No randomized controlled trials were identified. While the authors do state that the analysis of 14 studies indicated that an average success rate of non-operative treatment was 45%, they concluded that the highest average success rates for surgical treatment were excision, curettage, and drilling (ECD) (85%), followed by excision and curettage (EC) (78%), and excision alone (38%). They did not speak to OAT directly as there were too few qualitative studies on individuals with these techniques to draw any firm conclusions. In a randomized controlled trial, Gobbi et al. (2006) compared OAT (n=12), chondroplasty (n=11), and MF (n=10) in individuals with talar OCD. Mean follow-up was 53 months (24 to 119). Outcome measurements included Ankle-Hindfoot Scale (AHS), the Subjective Assessment Numeric Evaluation (SANE) rating, Numeric Pain Intensity (NPI), and MRI. The authors concluded that NPI was significantly lower in chondroplasty and MF cases when compared to OAT postoperatively at 24 hours (p < 0.001). They determined that there was no difference between OAT, chondroplasty, and MF with regard to AHS and SANE ratings in individuals with talar OCD. The study is limited in its small sample size and short-term follow-up period.
In a retrospective study, Scranton et al. (2006) examined the outcomes of 50 individuals with a symptomatic type V cystic talar defect who were treated with an arthroscopically harvested, cored osteochondral graft taken from the ipsilateral knee. Sixty-four percent of these individuals (n=32) had previous surgical treatment including drilling, fixation, cancellous grafting or debridement, and also received at least 6 initial months of conservative treatment which included rest, immobilization, and physiotherapy before the index procedure. Mean follow-up was 36 months (24 to 83). Ninety percent of the study participants (n=45) were satisfied with their post-procedure outcomes at final follow-up. Further surgery was required in 34% of individuals (n=17) and 20% of individuals (n=10) had arthroscopy and debridement. Limitations of this study include its retrospective study design, small sample size, and short-term follow-up period. The authors noted that their results are limited to type V lesions treated by OAT from the ipsilateral knee.
In a retrospective summary of cases, Hangody et al (2008) reported on 1097 mosaicplasty procedures, including 98 involving talar lesions. The authors reported good to excellent results in ninety-three percent of the talar procedures. Durability follow-up for talar implants were limited to 36 patients with the mean duration of 4.2 years (range 2-7 years) with an average participant age of 27 years old and an upper limit age of 50 years was recommended by the authors based on clinical experience and observed repair capabilities in advanced age. The average graft size was 1 cm2 with an average number of grafts of three (range 1-6). Limitations of this study include the retrospective study design, lack of control arm, small sample size, and relatively short-term follow-up period considering the mean age of participants.
In a more recent systematic review, Zengerink et al. (2010) attempted to summarize all eligible studies to compare the effectiveness of treatment strategies for talar OCD. The authors included 52 studies, identifying 65 treatment groups. Specific to OAT, there were 9 studies identified for the subsequent analysis, including 243 individuals. Good to excellent results were obtained in 87% of individuals (n=212) with success rates varying from 74% to 100%. The authors noted that post-operative complications were a concern. Specifically, donor knee morbidity was found in a clinically relevant number of individuals – up to 36% had been noted in the literature. The authors admit that this systematic review was limited in that it included only one RCT (Gobbi et al. 2006). Furthermore, the majority of the included studies had loss to follow-up exceeding 5%, which limits the potential validity of the results due to a higher chance of introducing bias.
In a systematic review, Mitchell et al. (2010) examined the current available peer-reviewed literature and recommended that arthroscopic excision curettage and BMS be the first treatment of choice for primary osteochondral talar lesions. The authors indicated that the studies included in this systematic review had weak study designs. There were no RCT or case-control studies specific to OAT. They state that due to the great diversity in the articles and variability in treatment results, no definitive conclusions can be drawn. Post-operative complications for the surgical treatment of primary osteochondral talar lesions can include incomplete defect coverage and difficulty with shoulder lesions. The authors called for further sufficiently powered, randomized clinical trials with uniform methodology and validated outcome measures.
In a nonrandomized study, Yoon et al (2014) evaluated outcomes for 44 individuals, twenty-two in each treatment group, utilizing either AOT or repeat arthoscopy with marrow stimulation technique, respectively. During the study design period, a total of 399 individuals received primary arthroscopic marrow stimulation as initial treatment of an osteochondral lesion of the talus and this study included 44 talar lesions that followed initial marrow stimulation suggesting marrow stimulation was an effective treatment option for 89% of the total study population. The decision to participate in either AOT or repeat marrow was based on discussions with clinicians and after risks were expressed limiting randomization between treatment group selection. Based on the AOFAS scores, the group treated with AOT resulted in 19/22 (86.4%) scoring good to excellent compared to 12 of 22 (54.5%) treated with repeat marrow stimulation (p=0.021). Initially, all participants demonstrated improvement in VAS and AOFAS at 6 month post-treatment, however, scores significantly deteriorated when the mean follow-up was reached for the group treated with repeat marrow stimulation. Demonstrated by only 7 (31.8%) achieved good to excellent scores and nearly two-thirds 14 of the 22 participant required additional revisions. Additionally, for those who presented with large lesions, at a mean follow up of 50 months, 100% (n=7) in the repeat marrow stimulation arm had clinical failure, whereas when presenting with small lesions 53.3% (8/15) presented with clinical failure (p=0.001). Suggesting for smaller lesions repeat marrow stimulation could still be considered. Alternatively, for individuals treated with OAT 18/22 (81.8%) had excellent or good results at a mean follow-up of 48 months and none required additional revisions. Based on the results in this small sample and nonrandomized study, OAT could be considered as a possible treatment for individuals who failed initial marrow stimulation.
In a prospective cohort study, Georgiannos et al (2016) evaluated 48 talar lesions in 46 individuals who have previously failed marrow stimulation. Individuals were examined using the AOFAS-hindfoot and VAS FA scores (0-100), measured both preoperatively and at six month post-surgery, as well as every year thereafter. This study recorded longer term follow-up then previously published literature reporting a median follow up of 5.5 years. Graft sizes ranged from 4.75 mm to 8 mm and were harvested from the ipsilateral talar articular facet. Preoperative MRI classified the lesions in this study according to a modified classification stage based on MRI appearance into one of three stages (3, 4, 5) with a distribution of 18, 24, 6, respectively. The mean AOFAS score improved from 55 (SD 4.2) preoperative to 90 (SD 5.8). The median VAS FA score increased from 52 (SD 6.6) preoperatively to 91 (SD 8.2). Following treatment, the authors reported 100% of the participants were clinically observed as fair or good. At the last follow-up radiographs, all grafts were fully incorporated and osteotomy sites healed. Five individuals did require subsequent surgery to treat impinging osteophytes. The study was limited by a small sample size, no control group, lack of heterogeneous study population as over 80% of the participants were male. This study suggest improvements in functional outcomes for a population who have failed marrow stimulation therapy to treat an OCD of the talas.
SUMMARY
OAT appears to improve symptoms in individuals who have had an inadequate response to a prior surgical procedure and are considered too young to be considered an appropriate candidate for total knee replacement. Short- to intermediate-term results are promising. However, the current available peer-reviewed literature does not permit conclusions concerning the effect of OAT on the long-term progression of degenerative changes.
Based on the current available peer-reviewed literature, OAT may be considered an option for symptomatic, skeletally mature individuals with full-thickness chondral lesions of the femoral condyle or trochlea caused by acute or repetitive trauma that have had an inadequate response to prior surgical repair. Based on the available evidence, clinical input, and recommendations from relevant medical societies, OAT may be considered medically necessary in individuals younger than 55 years of age with disabling knee pain who have not shown an adequate response to physical therapy and analgesic medications.
Based on the current available peer-reviewed literature, OAT may be considered an option for the treatment of large or cystic OCD of the talus. The American Orthopaedic Foot and Ankle Society, a medical specialty society of over 2000 orthopaedic surgeons, provided a guidance statement endorsing the use of osteochondral transplantation for the treatment of the osteochondral lesion of the talus, especially for large diameter and cystic lesions. Despite study limitations observed in the treatment of OCD of the talus with osteochondral autograft transplantation, the short-to-intermediate results have shown promise for the improvement based on numerous primary outcome scores. Based on the current available peer-reviewed literature, clinical practice and input and recommendation from relevant medical societies, OAT may be considered medically necessary as a revision surgery for individuals who has previously failed marrow stimulation for osteochondral lesion of the talus.
Considering the quality and availability of peer-reviewed literature, there are questions that still remain regarding the safety and effectiveness of OAT for the treatment of OCD of all other joints. Therefore, all other uses for OAT are considered experimental/ investigational and, not covered.
