Prevention of Development of Collapse in Osteonecrosis of the Femoral Head by Systemic Alendronate Treatment
T Nishii, N Sugano, H Miki, M Takao, T Koyama, N Nakamura, H Yoshikawa
Department of Orthopaedic Surgery, Osaka University Medical School, Suita Japan

Progression of collapse in osteonecrosis of the femoral head (ONFH) is greatly influenced by repair reaction, especially bone resorptive activity. This study was performed to test if systemic alendronate treatment, a potent inhibitor of osteoclast activity, may prevent development of collapse in ONFH.

Daily administration of oral alendronate 5mg/day was started in 14 hips of 11 patients with ONFH (Alendronate group). At the beginning, 3, 6, 12 months, plain radiographs, T1-weighted MR imaging, and biochemical makers of osteoclast activity (N-telopeptide of type-I collagen) and osteoblast activity (Bone-specific alkaline phosphatase), were examined. At 12 months, MR imaging was repeated. Eleven hips of 6 patients with ONFH who did not receive alendronate administration were considered as the Control group.

There was no significant difference with respect to gender distribution, etiology factors, initial ARCO stages, and extent of necrosis. In the Alendronate group, there was an early decrease of osteoclast activity at 3 months, with decrease to 62% at 12 months, while decrease of osteoblast activity was smaller with 80% at 12 months. Development of collapse was observed in 4 of the 11 hips (36%) in the Control group, and in none of the 14 hips in the Alendronate group. There was a significant difference of collapse development between the two groups (p=0.026, Mann-Whitney U-test). Signal change on serial MR images was observed in 5 of 9 hips (55%) in the Control group, while only one of 9 hips (11%) in the Alendronate group. Low incidence of signal change on serial MR images may reflect decrease of repair activity in the Alendronate group. The present study was the first clinical trial which showed a significant preventing effect of collapse development by administration of alendronate.