Histopathologic assessment of healed osteochondral fractures

PURPOSE: To assess the histopathologic features of healed tissue to define its biological and biomechanical properties after internal fixation of osteochondral fractures. Type of Study: Cohort study. METHODS: The general principle of management of detached acute osteochondral fractures is reattachment of the fragment by internal fixation, but the opinions on the quality and structure of the healed tissue that will be obtained after treatment is controversial. This study included 13 patients with acute osteochondral fractures who were treated arthroscopically and had surgical fixation providing joint-surface congruity. Patients with osteochondral fractures too small for fixation or with the overlying cartilage frayed, and patients with associated injuries were excluded from the study. The mean age of patients was 17 years (9 to 24 years). In 2 cases the fractures were localized at medial, in 7 at lateral femoral condyles, and in 4 at the patella. Internal fixation materials were K-wires for 1 case, Herbert screws for 3, and mini cancellous screws for 9 cases. The mean follow-up period was 6.3 years (3 to 13 years). On second-look arthroscopy, congruity of the joint surfaces and healed fractures was observed in all cases. Beside removal of the implant, punch biopsies were performed extending to the osteochondral junction; biopsy specimens were taken from the junction of the articular margin of the fragment and the edge of the remainder of the articular surface. RESULTS: On histologic examination of the specimens, scarce mature chondrocytes among regenerative stroma, which dyed more eosinophilic than the basophilic chondral stroma and which had a chondrocyte-like appearance, were seen. Maturation of histologic architecture to hyaline or articular cartilage was not recorded in any of these cases. CONCLUSIONS: The clinical results did not correlate with the histologic findings. Despite the protected joint surface congruence, restoration of the hyaline cartilage at the chondral junctions could not be obtained.