Histopathological Findings of Failed Free Vascularized Fibular Grafting for Osteonecrosis of the Femoral Head after Long-Term Follow-Up

Purpose. The aim of this study was to report the histopathology of failed free vascularized fibular grafting (FVFG) for osteonecrosis of the femoral head (ONFH) after a mean follow-up of 11.5 years (ranged from 10.6 to 14.2 years). Methods. Six hips of 5 patients with a history of steroid use, aged 34–67 years, were in stage II of ONFH as classified by the Ficat and Arlet classification at the time of FVFG treatment. Grafting failure led to osteoarthritis of the hip joint during a mean of 11.5 years of follow-up. Femoral head specimens were first evaluated macroscopically. Bone specimens were sectioned into long strips, divided into necrotic, transitional, and healthy zones, and then prepared for nondecalcified and decalcified histopathological examination using hematoxylin and eosin (HE) staining, Goldner’s trichrome staining, and immunofluorescence (IF) staining. Results. Femoral head articular cartilage surfaces appeared thin, opaque, and partially cartilaginous missing, with gradual collapse detected in weight-bearing areas. The interface with the fibular graft showed well union, with no obvious gaps between graft and host bone, as observed macroscopically. The necrotic area was filled with fibular graft, cancellous bone, and cartilaginous or soft tissue invasion. Histopathology results revealed well integration between fibular graft and host bone, with thickened trabecular bone. Gaps occurred in transitional and healthy zones. In the necrotic zone, cartilaginous or soft tissue invasion occurred, while thin or missing articular cartilage exposed subchondral bone to hip joint surfaces. By IF counterstaining with CD-31 and α-SMA, blood vessel transplanted during fibular grafting could be clearly observed along the graft from healthy to necrotic zones. In the necrotic zone, blood vessels presented obviously and spread into the surrounding area of the graft tip. Conclusion. After FVFG procedure with a mean follow-up of 11.5 years, fibular grafts retained their integrity as viable, vascularized, cortical bone that fused well with host bone and formed thickened trabecular bone surrounding the surface of the graft. However, the revascularization of FVFG’s blood vessels spreading from the tip of the fibular graft into subchondral area of necrotic lesion did not improve significantly in these failure cases. The local necrotic lesion failed to be repaired as healthy trabecular bone to buttress articular surface and was occupied by soft tissues.