The autologous osteochondral transplantation of the knee: clinical results, radiographic findings and histological aspects

Introduction: The osteochondral transplantation (OCT) is a well accepted treatment option for focal cartilage lesions in the knee joint, whereas the fate of the transplanted cartilage is still unclear and the clinical outcome is variable. The purpose of this study was to evaluate the histological character of autologous transplanted cartilage and to correlate technical aspects and the patients' history with the clinical outcome. Material and Methods: The OCT was performed in 27 patients (median age of 32 (22-43) years) with a focal chondral lesion at the medial femoral condyle. We investigated the clinical outcome after a median follow-up of 13.5 (5-28) months using the Lysholm-score and the integration of the transplanted plugs using an MRI-scoring system. Biopsy specimens from representative patients (n = 8) were evaluated with histological staining and immunohistochemistry. Results: The median Lysholm-score was 80 (range 45-98). The wide range of the Lysholm-score in clinical outcome did not show significant differences in: follow-up, concomitant injuries, defect size or genesis. The MRI analysis revealed in all cases a regular osseous integration of the subchondral bone, but a failed chondral integration. The congruency of the plugs to the joint surface was often incorrect, however a correlation between the MRI-score and the clinical outcome could not be shown. Histology of the transplanted cartilage revealed small changes in immunohistochemistry after a relatively short-term follow-up, whereas the cartilage has still the typical hyaline character. Often, the surrounding cartilage consists of fibrous and granulation tissue. Conclusion: The congruency of the joint surface can not be restored to the original status, particularly in larger defects with irregular shapes. However, we did not find any aspects which affected the function of the knee joint following OCT. It can be assumed that remaining lesions at the surrounding cartilage could maintain the inflammatory process and therefore maintain the pain and a low knee function. Further investigations are needed to specify the effects of the OCT on the transplanted cartilage and its influence on the later clinical outcome.