Is peak hamstrings muscle-tendon length criterion a sufficient indicator to recommend against surgical lengthening of hamstrings?

ABSTRACT

BACKGROUND: Excessive knee flexion during stance in children with cerebral palsy is often treated by surgical hamstrings lengthening. Pre-operative hamstrings muscle-tendon length can be estimated from kinematics and often used for decision making to rule out surgical lengthening if peak hamstrings muscle-tendon length is 'Not Short'. RESEARCH QUESTION If peak hamstrings muscle-tendon length is within two standard deviations of typical, is that a sufficient indicator to rule out surgical hamstrings lengthening? METHODS: Three motion analysis centers retrospectively identified children with cerebral palsy, age 6-17 years, who had consecutive gait analyses with knee flexion at initial contact > 20° and popliteal angle > 35° at initial study. Three groups were considered Medial Hamstrings Lengthening (MHL), Medial and Lateral Hamstrings Lengthening (MLHL), no surgical intervention (Control). Peak hamstrings muscle-tendon length at initial gait study was computed and categorized as 'Short' or 'Not Short'. Two outcomes variables were considered change in peak knee extension (PKE) and change in pelvic tilt. Univariate comparisons of all variables were assessed along with a multivariate stepwise regression analysis to identify pre-operative characteristics that may predict post-operative improvement. RESULTS: 440 individuals met inclusion criteria. Percentage of individuals with improved PKE by grouping were- MHL-'Short' 60%, MHL-'Not Short' 65%, MLHL-'Short' 74%, MLHL-'Not Short' 74%, Control 'Short' 20%, Control 'Not Short' 19%. Percentage of individuals with worsened pelvic tilt were- MHL-'Short' 25%, MHL-'Not Short' 11%, MLHL-'Short' 42%, MLHL-'Not Short' 21% with significantly more individuals in MHL-'Short' subgroup compared to MHL-'Not Short'. Multivariate analysis suggested that pre-operative pelvic tilt and weak hip extensor strength have the largest effect on predicting post-operative increase in APT. Peak muscle-tendon length was not a significant predictor of post-operative knee kinematics or increase in APT. SIGNIFICANCE: This study suggests that hamstrings muscle-tendon length criteria by itself is not a sufficient indicator to recommend against hamstrings lengthening.