[Torsion deformities in the lower extremities in patients with infantile cerebral palsy: pathogenesis and therapy]

Patients with spastic cerebral palsy often develop torsional deformities at the level of hip, shank or foot. The abnormal muscle activity such as spasticity or the increase of tone are considered as the major cause. The present study shows that the gait pattern is another cause which may lead to deformities. The study is based on gait analysis of 13 patients and 8 normal controls. The major and significant differences in gait kinematics were toe walking, toeing-in and internal rotation at the hip in the patients whereas the unaffected control group had a physiological heel-toe gait. The difference in torsional moments at the hip, knee and ankle were statistically significant. At the knee and the ankle a decrease in the internal rotation moment was found, whereas at the hip a paradoxical curve pattern with a more externally directed rotation moment was seen. These differences in torsional moments can explain the external rotation at the foot and/or shank as well as the increase in femoral anteversion, although they might be primarily caused by the deformity itself. Because a constantly acting force, however, changes the bony form and/or shape, the abnormal moments can be considered as a factor leading to deformities. A heel-toe gait seems to be mandatory for an efficient prophylaxis. Torsional deformities at the shank require a corrective osteotomy which is performed at the supramalleolar site and fixed by an unilateral, external fixator. Malrotations at the hip usually show two components: the functional part can be corrected by lengthening and weakening the tensor fasciae latae and the ventral parts of the glutei, using stretching exercises, botulinum toxin A or operative lengthening and releases. The increased femoral anteversion needs to be corrected by a femoral derotation osteotomy. Patients with cerebral palsy show a reduced control of their legs; therefore, balance internal torsion should not be corrected to neutral and overcorrection must be avoided. A remaining slight internal rotation after correction will help to spontaneously stabilize the leg if it gives way at initial contact, by "falling underneath the centre of gravity". If the leg is in neutral or external rotation, the patient needs to realign the centre of gravity over the dynamically unstable leg, showing a trunk-lean over the leg, the Duchenne limp.