Hip flexion deformity improves without psoas-lengthening after surgical correction of fixed knee flexion deformity in spastic diplegia.

BACKGROUND: It is unclear if psoas lengthening surgery is required in the treatment of patients with cerebral palsy (CP) with hip flexion deformity and previous studies show equivocal results with regard to functional outcome.
METHODS: This study retrospectively assessed 12 patients with a diagnosis of spastic diplegia who underwent single event multilevel surgery in order to correct deformities in the sagittal plane distal to the hip. Both clinical and instrument gait analysis results were recorded preoperatively, at one year (short term) and at five years (mid term) postoperatively.
RESULTS: Clinically measured hip and knee movement improved at both short and mid term follow up. Correlations of clinically measured maximum hip and knee extension were significant at all three time points. Angles at terminal stance/toe off for hip and knee from kinematic data also showed significant correlations at all three time points.
CONCLUSIONS: Our study demonstrates that the hip flexion deformities encountered in these patients will improve spontaneously when the distal fixed knee flexion deformity is surgically corrected. Therefore correction at the knee allows the ground reaction force to assume a more normal position resulting in correction at the hip over time. This then removes the need for surgery at the hip level. This fact is especially important when applied to psoas lengthening as this procedure can cause significant reduction in propulsion power.