Histopathological prevalence of subchondral insufficiency fracture of the femoral head.
OBJECTIVE: Subchondral insufficiency fracture of the femoral head (SIF) is a recently recognised cause of acute onset arthritis mostly in older women, which previously had been commonly considered either as osteonecrosis or osteoarthritis. The purpose of this study is to report the histopathological incidence of SIF using surgically removed femoral heads. METHODS: We reviewed 7718 consecutive femoral heads from 7286 patients removed over a 4-year period (2001-2004). There were 4211 women and 3507 men. The age range was from 13 to 96, average age was 60. There were 7349 hips with a preoperative clinical diagnosis of osteoarthritis and 369 with a preoperative clinical diagnosis of osteonecrosis. RESULTS: SIF was diagnosed histologically as the primary process in 501 of 7718 resected femoral heads (6.5%). The age range in these patients was from 20 to 93, with an average age of 68, in which 79% (394 hips) were over 60. They were 305 hips in women and 196 in men. The affected side was the right one in 253 hips and left in 248. The prevalence of SIF in cases with a preoperative diagnosis of osteoarthritis was 6.3% (460 of 7349), and with osteonecrosis was 11.1% (41 of 369). In all cases, callus and granulation tissue were observed histologically along the fracture line. CONCLUSIONS: In this large series of total hip replacements SIF as the cause of disease was diagnosed histologically in 6.5% of the surgically removed femoral heads.