Oral bisphosphonates and the risk of aseptic osteonecrosis

Canadian researchers set out to determine whether the use of oral bisphosphonates is associated with an increased risk of aseptic osteonecrosis (AON) among a cohort of elderly cardiovascular patients.

The researchers conducted a nested case-control study within a previously defined cardiovascular cohort of elderly Quebec patients using linked administrative health databases. Cases were defined as those with the diagnosis of hospitalization secondary to AON at a nonspecified site. For each case, 10 controls were randomly selected and matched to the cases by age, calendar time, and length of followup.

The main outcome measure was the risk ratio (RR) of AON among ever-users of oral bisphosphonates compared to that among nonusers. As a quality measure, RR for AON among users of statin and angiotensin-converting enzyme inhibitors (ACE-I) compared to nonusers were also calculated.

The initial cohort consisted of 87,837 subjects. In the primary analysis, the adjusted RR for AON among bisphosphonate users was 2.87 (95% CI 1.71-5.05). The adjusted RR for alendronate, etidronate, and risedronate were 2.87 (95% CI 1.46-5.67), 2.43 (95% CI 1.05-5.62), and 3.34 (95% CI 1.04-10.67), respectively. There were no significant differences in RR for AON among current users (most recent drug exposure within 90 days of diagnosis) and past users (drug exposure between 91 and 365 days before diagnosis) of bisphosphonates. The adjusted RR for both statins and ACE-I were 0.79 (95% CI 0.49-1.07) and 1.16 (95% CI 0.79-1.70), respectively.

The researchers concluded that, in this cohort of elderly cardiovascular patients, an association was observed between oral bisphosphonate use and aseptic osteonecrosis. They suggested that further research into this putative association is required.

(Source: Etminan M, Aminzadeh K, Matthew IR, Brophy JM. Use of oral bisphosphonates and the risk of aseptic osteonecrosis: a nested case-control study. J Rheumatol 2008. [Epub ahead of print] : PubMed : February 2008)