Histologic and immunohistochemical characteristics of failed articular cartilage resurfacing procedures for osteochondritis of the knee: a case series.

BACKGROUND The histologic appearance of the repair tissue after articular cartilage resurfacing procedures in humans is not well documented. HYPOTHESIS The histologic and immunohistochemical appearance of the repair tissues in failed articular cartilage resurfacing procedures will be similar, regardless of the procedure that was done, and will not resemble normal articular cartilage. STUDY DESIGN Case series; Level of evidence, 4. METHODS Graft tissue from 10 patients who underwent an autologous chondrocyte implantation (n = 6), microfracture (n = 3), or periosteal transplantation (n = 1) procedure to treat symptomatic osteochondritis dissecans of the medial femoral condyle was processed for histologic examination after failure of the articular cartilage resurfacing procedure. Serial sections from all slabs were stained with hematoxylin and eosin and toluidine blue and were immunostained using antibodies directed against types I, II, and X collagen. RESULTS Specimens from all 3 types of repair procedures were composed primarily of fibrous connective tissue and fibrocartilage. None of the sections stained positively for type X collagen. All 10 cases stained positively for type I collagen (range, 7%-97% of tissue area). Staining for type II collagen was positive in 4 of 6 autologous chondrocyte implantation cases, 3 of 3 microfracture cases, and the periosteal transplant case (range, 2%-65% of tissue area). In 8 of 10 cases, the percentage of the section area exhibiting positive staining for type I collagen was higher than for type II collagen (6 of 6 autologous chondrocyte implantation; 1 of 3 microfracture; 1 periosteal transplant). CONCLUSION The histologic appearance of the repair tissue of 3 different failed articular cartilage resurfacing procedures was similar and did not resemble normal articular cartilage.