The aims of this study were to determine the influence of external tibial t
orsion on the effectiveness of the ankle-foot orthoses (AFO) in children wi
th lumbosacral myelomeningocele. Forty patients with normal tibial rotation
and 18 patients with excessive external tibial torsion were evaluated with
three-dimensional gait analysis at their comfortable walking speed. The gr
oup with normal tibial rotation showed significantly greater knee extension
and lower mean extension moment compared with the group with external tibi
al torsion (p < 0.05). The posteriorly and laterally deviated ground-reacti
on force relative to the knee-flexion axis compromises the ability of this
force to facilitate knee extension. Patients with torsional magnitudes >20
degrees demand close inspection as candidates for derotation osteotomy. The
AFO will continue to stabilize the ankle-foot complex, but improved knee m
otion, knee-extensor activity, and ultimately walking efficiency may be com
promised.