Abstract:

BACKGROUND: Subchondral fractures were identified as the most complication of the femoral head necrosis and had important influences on the treatment and prognosis. The pathological and radiological findings on subchondral fractures of the femoral head necrosis have rare deep investigation.
OBJECTIVE: To compare the sensitivity of X-ray plain film, CT and magnetic resonance imaging (MRI) in revealing subchondral fractures.
METHODS: A total of 82 patients (132 hips) with known osteonecrosis were examined consecutively with MRI, CT and plain film. Sixteen resected specimens were sliced, decalcified, stained with hematoxylin and eosin, and examined using microscopy.
RESULTS AND CONCLUSION: Of 132 hips, 72 of the 132 hips with subchondral fractures were proved by radiography or CT, and 51 were detected on plain film, 60 on CT and 33 on MR images. Compared with CT, MR imaging has sensitivity and specificity of 36% and 100%. Radiography has sensitivity and specificity of 70% and 96% respectively. CT revealed more subchondral fractures in femoral head necrosis than MR imaging (χ²=10.95, P < 0.05). All histological sections in subchondral fractures area showed fluid accumulation and fibroblastic proliferation, which were corresponded slit-shaped radiolucent shadow on subchondral fractures using X-ray and CT, and consistent with above-described pathological processes. Results indicated that CT revealed more subchondral fractures in femoral head necrosis than radiography or MRI. MRI provided useful signs accompanied by subchondral fractures, especially T2WI+ fat-suppression, and evaluated liquid at fracture site. CT provided more detailed information than plain film.