Bisphosphonates are not associated with vertebral osteonecrosis

Intravertebral clefts are considered markers for osteonecrosis. We tested the hypothesis that bisphosphonate therapy was associated with vertebral osteonecrosis. A retrospective review of a vertebroplasty database was performed. Exposure to, duration of, and type of bisphosphonate therapy was documented. Radiographs were reviewed to identify intravertebral gas-filled or fluid-filled clefts, which are considered a marker for vertebral osteonecrosis. Proportion of patients with and without clefts was compared between the group exposed to bisphosphonates and the unexposed group using Chi-squared test. Duration of bisphosphonate exposure was compared between patients with and without clefts using Student's t-test. After exclusion of 16 patients with malignancy and 21 with chronic steroid therapy 237 patients were identified. Sixty-seven (28%) of the total cohort of patients were prescribed bisphosphonate therapy. Overall, clefts were present in 68 (29%) of the 237 patients. Among the 67 patients exposed to bisphosphonate therapy, 15 patients (22%) had clefts. Among the 170 patients not exposed to bisphosphonate therapy, 53 patients (31%) had clefts (P = 0.17 compared to bisphosphonate therapy group). Mean duration of bisphosphonate therapy among patients with clefts was 52 ± 63 weeks and among patients without clefts was 57 ± 79 weeks (P = 0.80). Intravertebral clefts are not associated with bisphosphonate therapy. If these clefts indicate osteonecrosis, then bisphosphonate therapy does not appear to be associated with vertebral osteonecrosis.