Isokinetic evaluation of hip strength muscle groups in unilateral lower limb amputees

Abstract

The objectives of the study were to measure the isokinetic strength of the hip flexor-extensor and adductor-abductor muscle groups in unilateral lower limb amputees and to evaluate abnormalities in order to improve the usual rehabilitation programs. Thirty-three patients with unilateral lower limb amputation were included in this study; they served as their own controls, the amputated side being compared to the intact side. Using an isokinetic device, the relative peak torques (N.m by body weight), bilateral asymmetries and agonist/antagonist torque ratios were calculated for the hip flexor, extensor, adductor and abductor muscle groups. A significant reduction of mean concentric relative peak torque measured on the amputated limbs was generally observed when compared to the intact contralateral limb (p < 0.05). The mean percentage of relative peak torque decrease was greater for the extensors than for the flexors (33±20% and 22±23%, respectively, at 30°/s angular velocity), and for the abductors than for the adductors (23 ± 22% and 11 ± 19%, respectively, at 30°/s angular velocity). Furthermore, the flexor/extensor torque ratio was significantly increased for the amputated limb (for instance, 1.25 ± 0.33 versus 1.09±0.25 for the intact limb at 30°/s). The reduction of the abductor/adductor ratio of the operated limb reached the level of statistical significance at 60°/s only (1.25 ± 0.46 versus 1.07 ± 0.36 for the intact limb). In conclusion, isokinetic testing revealed a significant reduction of the hip stabilizing muscle strength as a consequence of lower limb amputation. The more marked decrease of the strength of the abductor and extensor muscle groups, resulting in imbalances of the agonist/antagonist strength ratios should be taken into account to adapt the conventional rehabilitation programs.