Background Information: Vertebral fractures are a common type of osteoporotic fracture, associated with increased morbidity and mortality. An accumulation of vertebral fractures may lead to postural changes including hyperkyphosis. However, hyperkyphosis may also be caused from habitual forward flexion and weakening of the back extensor muscles. The associations between vertebral fractures, posture and physical performance remain unclear.
Objectives: Our primary objective was to investigate the association between number, severity, and location of vertebral fractures (vertebral fracture characteristics), or posture (OWD) and performance on the Timed Up and Go (TUG) test. Secondary objectives were to understand the association between vertebral fracture characteristics or OWD and other physical performance measures; and between vertebral fracture characteristics and OWD. Methods: We used baseline data from a multi-site randomized controlled trial of women over the age of 65 with a suspected vertebral fragility fracture. SPSS was used to run multivariable regression models to evaluate relationships between variables for each objective. A p-value of <0.05 was considered statistically significant. Both adjusted and unadjusted models were generated, where the adjusted model accounted for age, and pain.
Results: A total of 158 women were included in the study. The mean age (SD), BMI (SD), OWD (SD), and number of fractures was 75.9 (6.5) years, 26.7 (5.3) kg/m², 5.7 (4.6) cm, and 2.5 (2.4), respectively. OWD (B=0.25 95% CI= 0.12,0.38) and pain (B=0.32 95% CI=0.10,0.53) were independently associated with TUG, four-meter walk (OWD: B=0.08 95% CI=0.03,0.12; pain: B=0.11 95% CI=0.04,0.18), and step test (OWD: B= -0.33 95% CI=-0.47,-0.19; pain: B= -0.29 95% CI=-0.51,-0.07). OWD was independently associated with five times sit-to-stand (B=0.29 95% CI=0.07,0.50). Severity of fracture was independently associated with four-meter walk test. Number of fractures (B=0.82 95% CI=0.04-1.59) and pain (B=0.30 95% CI=0.04,0.56) were independently associated with OWD.
Conclusion: OWD was significantly associated with each of the physical performance tests, and contributed more to physical performance variability than number, severity and location of fracture.