Background. After hip fracture, muscle power (the product of force and velocity) remains persistently impaired, especially in the fractured leg. In addition to poor power, this asymmetrical deficit may limit mobility function (1) and is a risk factor for frequent and injurious falls (2, 3). Better understanding of mechanisms underlying mobility limitation after hip fracture may lead to improved rehabilitation strategies to prevent mobility limitation.
Aim. To explore whether asymmetrical leg extension power (LEP) deficit is associated with mobility limitation in women after proximal femoral fracture (PFF). Because higher LEP in the nonfractured leg may compensate for the deficit in the fractured leg, we assessed the combined effects of LEP and asymmetrical deficit.
Methods. 43 women, aged 73-96, participated in this observational study. LEP (W) of both legs, 10- and 50-ft walking (m/s) and stair-climbing speed (steps/s) were assessed 1 and 13 weeks after surgical repair of a PFF. The asymmetrical LEP deficit was calculated as (fractured/sum both legs) × 100%. The value of 50% represents equal LEP in both legs, a lower value an LEP deficit on the fractured side. Cross-sectional and longitudinal multiple linear regression analyses were used to test whether the combination of LEP of the nonfractured leg (as a measure of general leg power) and the asymmetrical deficit predicted mobility function at weeks 1 and 13.
Results. Between weeks 1 and 13 after PFF surgery, LEP in the fractured leg doubled and LEP in the nonfractured leg increased by 30%. Therefore, the asymmetrical deficit decreased from 28.5% ± 10.2% to 40.4% ± 8.6%. Regression analyses showed that poorer LEP of the nonfractured leg at week 1 correlated significantly with slower walking (Beta > 0.525, p < .001) and stair-climbing speed (Beta > 0.349, p < .016) and also predicted poorer mobility 12 weeks later (Beta > 0.354, p < .020). Large asymmetrical LEP deficit was cross-sectionally associated with slow stair-climbing speed (Beta > 0.343, p < .018) at weeks 1 and 13, but not with walking speed. The reduction in asymmetrical deficit over time was significantly associated (Beta = 0.519, p = .015) with the improvement in stair-climbing speed, while the increase in LEP of the nonfractured leg was not associated with the improvement in any of the mobility measures.
Conclusions. A large muscle power deficit in the fractured leg was present after the PFF. During the 3-month recovery, the asymmetrical deficit decreased only partly, probably due to spontaneous recovery of the fractured leg. Higher general power in the legs predicted better recovery of mobility function after PFF, whereas a large asymmetrical deficit may limit stair climbing. The results stress the importance of increasing muscle power in rehabilitation after PFF to prevent mobility limitation. Reducing the asymmetrical deficit by increasing power of the fractured leg may be beneficial, especially for more challenging mobility tasks that require unilateral force production, such as stair climbing. However, further study is needed to determine the effects of increasing muscle power and reducing the asymmetrical deficit by training. References: 1) Portegijs et al. Arch Phys Med Rehabil 2005; 86:1838-42. 2) Skelton et al. Age Aging 2002;31:119-25. 3) Portegijs et al. J Am Geriatr Soc 2006;54:551-3.