Introduction: In children with MMC characteristic kinematic gait patterns and center of mass motion have been identified for different lumbo-sacral levels, which may vary in specific muscle paresis definitions and ambulatory outcome. The goal was to investigate compensatory movements employed in MMC in groups with successive paresis in the following major muscle groups: plantarflexors, dorsiflexors, hip abductors and hip extensors.

Patients and Methods: 28 children with MMC (m=10.3 y), walking independently participated in a gait study. A classification based on paresis on the primary muscle groups was established using standard Manual Muscle Test (MMT). Five groups of MMC were established based on successive paresis (0-2 MMT) of the plantarflexors,dor-siflexors, hip abductors, and hip extensors. Subjects were tested in their habitual orthoses, if any. All children underwent full-body three-dimensional gait analysis (VICON, Oxford). Five kinematic cycles from each side were analyzed and group averages were calculated.

Results: The most striking compensatory movements were observed in the frontal and transverse planes in the trunk, pelvis, and hips. Trunk sway increased sequentially from Groups 1 to 5, with the largest interval occurring at the onset of hip abductor paresis (Group 4). Trunk and pelvic rotation were observed to completely alter at the onset of hip abductor paresis (Group 4), where an internal position occurs during stance and external during swing. ‘Pelvic hike,’ or the lifting of the pelvis during swing, was observed in as early as Group 2 with plantarflexor paresis, becoming more pronounced in the latter groups. Large hip abduction was observed during stance at the onset of hip abductor paresis (Group 4). The onset of dorsiflexor paresis result in few kinematic changes since all subjects in Groups 2 and 3 wore orthoses. Sagittal plane differences were observed at the onset of hip extensor paresis (Group 5), where the trunk and pelvis were more posteriorly tipped and hips less flexed.

Discussion The classification method aids in understanding the specific compensatory mechanisms employed when the muscle functions are successively lost. Plantarflexor paresis is evident in all three planes in even the trunk. Abductor weakness results in large frontal and transverse plane changes. Hip extensor weakness is mostly evident in the sagittal plane. By understand-ingthe characteristic movements employed, an improved basis for evaluation and treatment can be established.