Study design: A cross-sectional study comparing normal subjects and patients with lumbar disc herniation (LDH) with sciatica.
Objective: To simultaneously measure the isokinetic muscle strength of the trunk, knees, and ankles in both groups.
Summary of background data: Coordination between the trunk and lower extremity muscles is important for normal physical activity. Reduced trunk and knee muscle strength have been reported in patients with lower level LDH; however, ankle performance in these patients is still unknown.
Methods: We recruited 43 normal subjects as controls and 33 patients with lower level LDH with sciatica. The isokinetic strength of the trunk, knees, and ankles was measured at 2 velocities in random order: 60°/s and 120°/s, and 60°/s and 180°/s for trunk and ankle strength and for knee strength, respectively.
Results: The isokinetic trunk strength was significantly lower in the LDH group irrespective of test modes or velocity. Despite unilateral sciatica or test modes and velocity, the unilateral knee strength was significantly lower in the LDH group than that in the control group. Knee extension torque was also found to be significantly lower in the limbs with sciatica than in those without sciatica at the testing velocity of 180°/s (80.25 ± 24.88 vs. 95.42 ± 26.29 Nm, P < 0.05). Irrespective of unilateral sciatica or test velocity, ankle plantar flexion torque revealed to be significantly lower in the LDH group than the control group; however, dorsiflexion torque was not different. Significant correlations were demonstrated among the total muscle strength of the trunk, knees, and ankles in both groups.
Conclusion: Besides the lower trunk strength, concurrent lower unilateral knee and ankle plantar flexion but not dorsiflexion strength was demonstrated in the LDH subjects with unilateral sciatica, regardless of its location. As compared to the limbs without sciatica, an additional 14% reduction of knee extension torque at 180°/s was found in the limbs with sciatica in the LDH patients.