Pre-operative hamstring length and velocity do not explain the reduced effectiveness of repeat hamstring lengthening in children with cerebral palsy and crouch gait.
Melisa Osborne, Nicole M Mueske, Susan A Rethlefsen and 2 others
PMID 30572181WHAT IT FOUND
Preoperative hamstring length and velocity did not differ between first and repeat hamstring lengthening.
Both groups had short or slow hamstrings. Knee flexion improved in more limbs after first surgery than after repeat, but the preoperative muscle measures did not explain the difference.
Key findings
01Peak hamstring length and peak lengthening velocity were lower than controls in both surgery groups, but did not differ between first and repeat surgery groups before surgery.
02All surgical limbs had hamstrings shorter and/or slower than controls preoperatively, and all but three limbs were more than 2 standard deviations below normal.
03After surgery, the first group improved in popliteal angle, knee flexion at initial contact and stance, and hamstring length; the repeat group improved only in hamstring length and worsened passive knee extension and minimum hip flexion in stance; neither group showed a significant change in hamstring velocity.
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What it does not show
The study was small and retrospective, with 23 patients and 10 controls, and only 8 patients in the repeat surgery group. Postoperative therapy and bracing were not controlled, and some postoperative gait analyses may have been done mainly because problems persisted, which could bias the sample toward poorer outcomes. The hamstring surgery was not standardised: the extent varied, some procedures were open and some percutaneous, and concomitant surgeries occurred, so their separate contributions cannot be judged from the text. The repeat group was older than the first-surgery group, average 13.0 years versus 9.0 years, and had more children at GMFCS level III, although the function difference was not statistically significant. Controls were a convenience sample, walking speed was not controlled, and hamstring velocity could not be compared with speed-matched norms. The musculoskeletal model may not fully represent children with disabilities, and subject-specific femoral anteversion was not modelled.
Declared interests
The authors declared no conflicts of interest.
The easy way to misread this
Do not conclude that repeat hamstring lengthening failed because the hamstrings were not short or slow. Both the first and repeat surgery groups had short and/or slow hamstrings before surgery, and their baseline hamstring length and velocity did not differ.