Subchondral fatigue fracture of the femoral head in military recruits.

Abstract

Subchondral stress fracture of the femoral head is a rare condition that usually occurs as an insufficiency fracture in people with poor bone quality. We evaluated the clinical characteristics of subchondral fatigue fractures of the femoral head that occurred in young, healthy military recruits. Between January 1998 and November 2001, seven subchondral fatigue fractures of the femoral head were treated in five patients. The characteristics of this condition were ascertained by assessing the clinical course as well as radiographs, bone scintigrams, and magnetic resonance images. All patients were male military recruits in their early twenties in whom pain had developed within five months after recruitment. Definite abnormal findings were observed on the initial radiographs of four hips in three patients, and the femoral head was markedly collapsed in two of these four hips. Bone scintigrams were made of five hips in four patients, and all of them showed increased radionuclide uptake in the femoral head. In all affected hips, magnetic resonance images demonstrated a localized or diffuse bone-marrow-edema pattern in the femoral head and/or neck. A subchondral fracture line (a magnetic resonance crescent sign) was identified in all hips. In the patients who did not have collapse of the femoral head, the pain decreased gradually and disappeared completely within six months, with correspondingly improved findings on sequential magnetic resonance images. The patients with femoral head collapse were treated with total hip arthroplasty or an iliac bone strut graft. When a military recruit or an athlete reports hip pain, a diagnosis of subchondral fatigue fracture of the femoral head should be considered.