Trunk muscle strength in flexion, extension, and axial rotation in patients managed with lumbar disc herniation surgery and in healthy control subjects

Design. A cross-sectional study was conducted. Objective. To compare maximal flexion, extension, and rotation strength as well as force-time characteristics of trunk muscles in patients who undergo lumbar disc herniation with those in healthy control subjects 2 months after surgery. Summary of Background Data. Insufficient attention has been paid to muscle strength characteristics after lumbar disc herniation surgery. Methods. For this study, 30 postoperative patients with lumbar disc herniation and 30 healthy control subjects volunteered to participate. Isometric trunk flexion, extension in the standing position, and seated rotation strength were tested bilaterally in a neutral posture and at 30degrees axial prerotation. The area under the curve was calculated to analyze explosive force capacity. Dynamic endurance strength was measured by calculating the repetition maximum. Pain during the strength measurements was assessed by a visual analog scale. Results. The healthy control subjects showed 44% and 36% higher isometric trunk flexion (P < 0.001) and extension (P < 0.001) forces, respectively, than the patients. The respective values for the area under the curve were 41% and 37% higher for the trunk flexors (P < 0.001) and extensors (P < 0.001) in the healthy control subjects than in the patients. The differences in trunk rotation force between the groups were statistically significant when the lower body was rotated 30degrees to the right (P = 0.023) or to the left (P = 0.043) and the upper body was rotated in the opposite direction. Furthermore, in the dynamic endurance strength test, the healthy control subjects performed 70% more repetitions both for trunk flexors and extensors than did the patients. Some of the patients reported mild pain during the strength measurements, but the level of pain did not correlate with the strength values. Conclusions. The recovery of maximal endurance and explosive type strength characteristics is incomplete in patients with lumbar disc herniation 2 months after surgery. Active strength training is recommended to restore muscle function in these patients.