Risk of fragility fracture in older men with severe spine osteoarthritis

Abstract

Purpose: Data on the association of osteoarthritis (OA) with bone mass and fragility are limited. In particular, data on the fracture risk in older men with spine OA are scarce. Our aim was to study the association of baseline severity of spine OA with bone mineral density (BMD), bone loss and risk of fragility fracture in a cohort of older men. Methods: Men aged >50 (n=766) had lateral spine radiographs at baseline. Spine OA was assessed by Lane's score (J Rheumatol, 1993). We calculated the total osteophyte score by adding up osteophyte scores for 6 intervertebral levels. We calculated total disc narrowing score (DSN) and total overall grade score similarly. BMD was measured by DXA using a HOLOGIC QDR1500 device. Abdominal aortic calcification (AAC) was assessed by Kauppila's semiquantitative score (Atherosclerosis, 1997). Men were followed up for 7.5 yr to assess bone loss (every 18 mo) and incident vertebral fractures. Incident peripheral fractures were assessed for 10 yr. Results: Moderate and severe osteophytes were found in 85% of men, 72% of men had DSN. After adjustment for age and weight, BMD was 2-7% higher (p<0.05 to <0.001) in men with severe spine OA in comparison with men without or with mild spine OA. For instance, men with severe DSN (total score>4, highest quartile) had 5% (0.4SD, p<0.001) higher total hip BMD compared with men without DSN. The rate of bone loss did not differ according to the severity of spine OA regardless of the measure of the spine OA (DSN, osteophytosis) and regardless of the skeletal site (p>0.4). During the follow-up, 27 men sustained radiographic vertebral fractures. After adjustment for age, BMI, lumbar spine BMD, AAC, prior falls and fractures, risk of vertebral fracture increased with the DSN severity (HR= 1.15 per increase by 1 unit, 95%CI: 1.01-1.31, p<0.05). In the multivariable model, the risk of vertebral fracture was higher in the highest quartile of total DSN score vs. the three lower quartiles combined (HR= 2.47, 95%CI: 1.04-5.86, p<0.05). During the follow-up, 61 men sustained peripheral fragility fractures. The incidence of peripheral fracture was lower above the median of total DSN score (4.6 vs 10.2%, p<0.005). After adjustment for the confounders (including hip BMD and leg disability), the risk of peripheral fracture was lower in men above the median total DSN score vs. below the median (HR= 0.44, 95%CI: 0.24-0.80, p<0.01). Other measures of spine OA were not associated with the risk of fracture. Conclusions: Men with severe spine OA had higher BMD vs. men without spine OA. Spine OA had no impact on the rate of bone loss. Men with severe multi-level DSN had higher risk of vertebral fracture, but lower risk of peripheral fracture.