Subchondral insufficiency fracture of the femoral head: a differential diagnosis in acute onset of coxarthrosis in the elderly.

OBJECTIVE

To document subchondral insufficiency fracture (SIF) of the femoral head and investigate its frequency.

METHODS

The study was based on a retrospective review of 464 removed femoral heads (from 419 patients) with both radiologic and histologic evidence of subchondral collapse. Gross photographs, specimen radiographs, and histologic sections were reevaluated in all cases. Available clinical notes and imaging studies were also reviewed.

RESULTS

Ten cases previously diagnosed as osteonecrosis were reinterpreted as SIF on a histopathologic basis. All of these patients were women over 65 years old (average age 75) with osteopenia. The initial symptom was acute onset of hip pain. Radiologically, a subchondral collapse, mainly in the superolateral segment of the femoral head, was noted. Magnetic resonance imaging, available in 3 cases, showed diffuse low intensity on T1-weighted images and high intensity on T2-weighted or fat-suppressed images. Bone scintigraphy, available in 4 cases, showed increased uptake in the femoral head. Histopathologically, a 1.0-2.5-cm long linear whitish gray zone, comprising fracture callus and granulation tissue, was found beneath the subchondral bone end plate. There was no evidence of antecedent osteonecrosis.

CONCLUSION

The results of this study indicate that SIF should be included in the differential diagnosis of acute onset of coxarthrosis in the elderly.