Is simultaneous hamstring lengthening necessary when performing distal femoral extension osteotomy and patellar tendon advancement?

Crouch gait is common in individuals with cerebral palsy. Recently published data has shown that distal femoral extension osteotomy with patellar tendon advancement (DFEO/PTA) is an effective procedure to correct crouch gait in the presence of a knee flexion contracture and quadriceps insufficiency. Short length and slow lengthening rate (velocity) of the hamstrings are indications for hamstrings surgery. We empirically believed that hamstrings surgery would not be necessary to improve hamstring function when DFEO/PTA are performed. This hypothesis was examined in a retrospective review of hamstrings length and velocity before and after DFEO/PTA. 51 limbs in 32 individuals with a diagnosis of CP who underwent DFEO/PTA without concomitant hamstring surgery were included in the study. Pre and post-operative peak medial hamstring length and velocity z-scores were calculated using a musculoskeletal model. A subset of limbs with pre-operative values above or below two SD from the control mean emerged and were called long or short respectively. Members of this subset would often be considered candidates for hamstrings surgery. Categorical length outcomes were derived, with analogous categories for velocity. The mean peak hamstring length z-score improved pre- to post-operatively from -2.2 to -0.76 (p<0.001). The mean peak velocity z-score improved from -3.1 to -1.5 (p<0.001) [Figure 1]. DFEO/PTA surgery without concomitant hamstrings surgery led to significantly longer or faster hamstrings. Specifically, we saw 94% good or neutral results for length correction and 80% good or neutral results for velocity correction. Because crouch improved without posterior pelvic tilting, and because both hamstring length and velocity increased substantially, we conclude that concomitant hamstring surgery is rarely needed when performing DFEO/PTA.