MASSIVE OSTEOARTICULAR KNEE ALLOGRAFTS - STRUCTURAL-CHANGES EVALUATEDWITH CT

PURPOSE: To analyze the structural changes seen at computed tomography (CT), particularly the findings that precede insufficiency (fatigue) fractures in massive osteoarticular knee allografts. MATERIALS AND MET HODS: The subchondral and cancellous bone of 12 allografts were retros pectively evaluated with repeat transaxial CT (mean follow-up, 53 mont hs). RESULTS: Early cortical graft resorption was followed by slow thi ckening after 6 months. Formation of resorptive cysts increased the co rtical irregularity, which leveled off after 2 years. Late remodeling was evident as a subcortical sclerotic rim,''neocortex.'' Initially, t he cancellous graft bone showed higher attenuation than the host bone; this difference subsided gradually during the first 3 years. Four ins ufficiency fractures were detected after the Ist postoperative year. P oor remodeling preceded these fractures. CONCLUSION: CT effectively de picted the structural changes during allograft incorporation and was s uperior to plain radiography for the detection of insufficiency fractu res. The use of CT for follow-up of massive osteoarticular knee allogr afts provides additional information concerning the readiness of the g raft for weight bearing.