Osteoporosis is a common feature of ankylosing spondylitis (AS), and vertebral fractures are an increasingly recognised complication. A cumulative fracture prevalence of between 9.5% and 18% has been reported, with a six- to eightfold relative increased risk of vertebral fracture.^1–3 Osteoporosis and new bone formation (syndesmophytosis) suggest that disordered bone turnover has a role in disease pathogenesis in AS. Bisphosphonates accumulate at sites of increased bone turnover, and inhibit bone resorption by inducing osteoclast apoptosis,⁴ thereby improving bone density and reducing fracture rates.⁵ Pulse pamidronate has recently been used with clinical efficacy in the treatment of AS.^6,7 Biochemical markers of bone turnover have been used to monitor response to treatment in postmenopausal osteoporosis.⁸

The effect of bisphosphonate treatment on biochemical bone turnover markers has not previously been studied in AS. We aimed at studying the efficacy of pulse pamidronate treatment in severe AS, and at determining its effect …