Lower-limb pain, disease and injury burden as determinants of muscle strength deficit after hip fracture

Abstract

Background: Hip fracture may result in an asymmetrical lower-limb strength deficit. The deficit may be related to the trauma, surgical treatment, pain, or disuse of the fractured limb. However, disease and injury burden or musculoskeletal pain in the other limb may reduce muscle strength on that side, reducing the asymmetrical deficit. Our study aim was to explore the asymmetrical strength deficit and to determine potential underlying factors in persons 6 months to 7 years after a hip fracture. Methods: Asymmetrical deficit was calculated ((fractured/sum both lower-limbs) x 100%) for isometric knee extension torque, rate of force development during isometric testing, and leg extension power. The asymmetrical measure for lower-limb muscle mass was calculated (fractured-non-fractured), and that of lower-limb pain and disease and injury burden (nonfractured-fractured).

Results: Half of the participants had no consistent asymmetrical deficit on the fractured side. Regression analyses showed that asymmetrical measures of lower-limb pain, muscle mass and disease and injury burden predicted asymmetrical deficit in knee extension torque (R2 =0.43) and rate of force development (R2 =0.36). More intense pain and disease and injury burden affecting the non-fractured limb and smaller muscle mass relative to the fractured limb were associated with a smaller asymmetrical deficit. Conclusions: Following hip fracture, preventing decreases in muscle strength and power and a large asymmetrical deficit by targeted pain management and rehabilitation may help to reduce the risk of subsequent mobility limitations and falls.