Association between vertebral fragility fractures, muscle strength and physical performance: A cross-sectional study

Background: Few studies have investigated the association between vertebral fragility fractures and lower limb muscle strength and physical performance in women with low bone mass.

Objectives: To explore whether the presence of vertebral fracture is independently associated with poor physical performance and decreased lower limb muscle strength. To understand whether lower limb muscle strength is associated with physical performance in women with vertebral fracture.

Methods: Older women with low bone mass were divided into 2 groups: no vertebral fracture (NF) and presence of vertebral fragility fracture (VFF). Physical performance was evaluated using the Five Times Sit to Stand (5TSS) test, the Timed Up and Go (TUG) test and a 5m walk test (5MWT). Lower limb muscle strength was assessed using an isokinetic dynamometer.

Results: We included 94 women with low bone mass (mean age 71.6 [SD 5.7] years, time since menopause 24.4 [7.1] years, mean BMI 27.5 [5.1] kgm^-2). VFF was only associated with low peak hip abductor torque (p = 0.001) after adjustments. In the VFF group (n= 47), each 1 Nmkg^-1 increase: in knee extensor torque was associated with improved 5MWT (p = 0.005), TUG (p = 0.002) and 5TSS (p = 0.005) performances; in knee flexor torque was associated with improved 5MWT speed (p = 0.003) and TUG time (p = 0.006); in hip abductor torque was associated with improved 5MWT speed (p = 0.003); and in hip extensor torque with improved TUG time (p = 0.046).

Conclusion: VFF was associated with reduced hip abductor strength in older women. However, the number of vertebral fractures influenced the association. Additionally, lower limb muscle strength was associated with physical performance, regardless of the clinical characteristics of the fractures. Therefore, strength and power training programs for the lower limbs could improve physical performance.