Hip-related tenotomy and progression to severe displacement of the hip in nonambulant children with cerebral palsy

Aims The aim of this study was to investigate whether a hip-related tenotomy is associated with a lower risk of severe hip outcomes in nonambulant children with cerebral palsy and established displacement of the hip. Methods This nationwide register-based cohort study included children classified as Gross Motor Function Classification System (GMFCS) level IV or V who were enrolled in the Danish Cerebral Palsy Follow-Up Program (CPOP) between 1 January 2008 and 31 December 2023. Hips with a baseline migration percentage (MP) of between 30% and 49% were included and followed until the first occurrence of a severe hip outcome, defined as a MP of ≥ 50% or osteotomy of the hip. Death was treated as a competing event. The cumulative incidence was estimated using the Aalen-Johansen estimator. Associations were analyzed using Fine-Gray competing-risk regression with cluster-robust standard errors. Results A total of 259 children, contributing 406 hips, were included, of which 110 underwent a tenotomy. At ten years, the cumulative incidence of a severe hip outcome was 34.7% (95% CI 28.8 to 40.7) without tenotomy, and 20.4% (95% CI 12.4 to 28.5) with tenotomy. In adjusted competing-risk regression, tenotomy was associated with a significantly lower risk of a severe hip outcome (sub-distribution hazard ratio (sHR) 0.53 (95% CI 0.34 to 0.84); p = 0.006). GMFCS-specific Fine-Gray analyses showed a significant association in GMFCS level IV (sHR 0.35 (95% CI 0.16 to 0.78); p = 0.010), whereas the association did not reach significance in GMFCS level V (sHR 0.68 (95% CI 0.40 to 1.19); p = 0.180). Spasticity, as classified according to the Modified Ashworth Scale (MAS) 1 and ≥ 3, was independently associated with a significantly increased risk of a severe hip outcome. Conclusion A hip-related tenotomy was associated with a significantly lower incidence of the subsequent development of a severe hip outcome among nonambulant children with established displacement of the hip, particularly in GMFCS level IV. In GMFCS level V, progression remained substantial irrespective of the soft-tissue release, emphasizing the importance of careful patient selection and continued surveillance. Cite this article: Bone Joint J 2026;108-B(11):1379–1384.