Hamstring lengthening for crouch gait in ambulatory cerebral palsy: a systematic review of surgical extent, technique, durability and harms

This study aimed to assess how patient selection, operative level and extent, approach, transfer and revision surgery influence kinematics, function, durability and harms after hamstring lengthening for crouch gait in ambulatory cerebral palsy. PubMed/MEDLINE, Embase, Scopus and CENTRAL were searched through 16 July 2026. After peer review, the original strategy was updated and a corrective two-concept search without compulsory crouch terminology was run from inception to 31 August 2026. Eligible postoperative reports formed the core synthesis; contextual sources were analysed separately. Risk of bias was assessed using Cochrane risk-of-bias tool for randomized trials, version 2, Risk Of Bias In Non-randomized Studies – of Interventions or Methodological Index for Non‐Randomized Studies. Synthesis Without Meta-analysis outcome-level synthesis was used because cohort overlap, clinical and measurement heterogeneity, and incomplete variance precluded pooling. Seventy-two core reports formed 53 conservative analytic clusters. Evidence was predominantly retrospective; the sole randomised comparison had high risk of bias. Among exact-data clusters, popliteal angle generally improved by 6.7–32.8°, knee flexion at initial contact by 5–25° and stance knee flexion by 5–23°. Functional gains were inconsistent and correction often attenuated during growth. Repeat lengthening produced smaller improvements than primary surgery in the largest comparison. Anterior pelvic tilt, reduced swing knee flexion, recurrence, overcorrection and nerve palsy were important trade-offs. Certainty was very low across all outcome domains. Selective, extent-specific hamstring lengthening can improve sagittal knee measures when clinical examination and instrumented gait analysis confirm a meaningful hamstring contribution. Current comparative evidence does not support routine lateral or automatic repeat lengthening. Surgery should be framed within longitudinal management through growth, with counselling about uncertain functional benefit and important trade-offs.