Rectus femoris transfers with and without a hamstring lengthening will not change hip kinematics in children with cerebral palsy

Background: A rectus femoris transfer (RFT) surgery with and without a hamstring lengthening (HSL) is used to treat stiff-knee gait in children with cerebral palsy (CP). While current literature has reported that a RFT surgery improves the kinematics at the knee, little is known about the kinematic changes at the hip. Research question: Does a RFT surgery change hip joint kinematics in children with CP? Methods: This retrospective study included children (<18 years old) diagnosed with CP, who underwent a RFT procedure, and who were seen at our institution's accredited clinical motion laboratory. Patients with both preand post-operative gait analysis were identified and comparison between those analyses were performed to identify kinematic differences at the hip and knee. A total of 66 legs from 46 children (mean age: 11.1 +/- 3.6) met the inclusion criteria. Results: Overall results revealed that a RFT did not change kinematics at the hip [p > 0.051, however, a RFT did increase the maximum knee flexion during the swing period [Mean Difference Post - Pre: 8.3 degrees, 95% CI: 4.9-11.8, p < 0.0001]. Additionally, it was found that changes in hip extension during the terminal stance phase were significantly different between the combined RFT and HSL compared to solely an RFT. The results of this study also revealed that children whose stiff-knee gait did not improve, tended to have increased hip external rotation during terminal stance and swing and greater hip extension during terminal stance, compared to children whose stiff-knee gait did improve. Significance: Overall, a RFT with and without a HSL surgery improves hip and knee kinematics in the sagittal plane, however, improvements at the hip were not clinically significant. As a result, a RFT or a combined RFT with HSL should not be used to change hip kinematics in children with CP.