Pre-operative hamstring length and velocity do not explain the reduced effectiveness of repeat hamstring lengthening to correct crouch gait in children with cerebral palsy
J8
M Osborne1, N Mueske2, S Rethlefsen2, R Kay3, T Wren2
1University of Southern California, Los Angeles, CA, USA; 2Children's Hospital Los Angeles, Los Angeles, CA, USA; 3Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
Background and Objective(s): Crouch gait is a common movement disorder that progresses with age in children with cerebral palsy (CP). To correct crouch gait, children with CP often undergo hamstring lengthening surgery (HSL). Despite the overall effectiveness of HSL, crouch gait can recur over time. Although repeat HSL is often performed, a recent study showed gait routinely improved only after primary, and not repeat, HSL. Causes of recurrent crouch gait and the lower effectiveness of repeat HSL are unclear. This study examined whether the difference in outcomes could be due to differences in dynamic muscle-tendon length and/or lengthening velocity. We hypothesized that children undergoing repeat HSL do not have short or slow hamstrings, thereby explaining their lack of improvement after HSL.
Study Design: Retrospective, cross-sectional.
Study Participants & Setting: A retrospective chart review identified children with CP under 15 years of age who had primary or repeat HSL with pre- and postoperative gait analyses at our institution between November 2005 and March 2016. A control group of typically developing children was also included.
Materials/Methods: Gait analysis data were collected from a 3-D motion capture system and analyzed using musculoskeletal modeling (OpenSim) to calculate joint angles and muscle-tendon lengths. The control, primary, and repeat HSL groups were compared using ANOVA with Bonferroni adjusted post-hoc t-tests. Pre- to postoperative change was evaluated using paired t-tests.
Results: This study included 26 children with CP and 10 controls without CP. Fifteen patients had undergone primary HSL (13 bilateral), and 11 had undergone repeat HSL (8 bilateral). In both surgical groups, all limbs had hamstrings that were dynamically shorter and/or slower than controls by >1–2 standard deviations preoperatively. In pre- to postoperative analysis, the primary HSL group showed improved popliteal angle, initial contact knee flexion, minimum stance knee flexion, and hamstring length while the repeat HSL group only improved in hamstring length (Table 1).
Conclusions/Significance: Since both surgical groups had short and slow hamstrings preoperatively, hamstring length and velocity do not explain the lower effectiveness of repeat HSL. Poor outcomes after repeat HSL are likely due to other factors, and interventions other than repeat HSL may be preferable for treating recurrent crouch.
