Association between spasticity of the hip and development of hip displacement in children: a cohort study of 786 hips.

Authors

Muhammed Bakhtiyar, Afrim Iljazi, Anders Odgaard, Christian Wong, Michael Mørk Petersen, Andreas Balslev-Clausen

Published in

Acta orthopaedica. Volume 97. Pages 417-422. Jun 22, 2026. Epub Jun 22, 2026.

Abstract

 Hip migration is a common complication in children with cerebral palsy (CP). Although spasticity has long been considered a contributing factor, muscle-specific associations with hip migration remain unclear. We aimed to investigate whether assessed hip spasticity was associated with hip displacement risk in non-ambulant children with CP.
 In this population-based cohort study using Danish Cerebral Palsy Follow-Up Program (CPOP) data, children classified as Gross Motor Function Classification System (GMFCS) levels IV-V with at least 1 hip radiograph were included. Pathological hip migration was defined as migration percentage (MP) ≥ 30%. Spasticity was assessed using the Modified Ashworth Scale (MAS) for hip adductors, flexors, and extensors. Overall hip spasticity was defined as summed MAS (0, 1-3, 4-6, 7-9). Cumulative incidence was estimated with death as a competing event, and associations were evaluated using Fine-Gray regression adjusted for GMFCS level.
422 children (786 hips) were included; 374 hips (48%) reached MP ≥ 30%, and death occurred as a competing event in 16 patients (25 hips). Higher overall hip spasticity was associated with increased risk of hip migration, with subdistribution hazard ratios (sHRs) of 1.46 (CI 1.05-2.01), 1.77 (CI 1.22-2.58), and 2.53 (CI 1.59-4.02) for MAS 1-3, 4-6, and 7-9, respectively, compared with MAS 0. Adductor spasticity showed the most consistent association with sHRs ranging from 1.44 to 1.97 across MAS categories.
 In children with CP classified as GMFCS levels IV-V, higher clinically assessed hip spasticity-particularly of the hip adductors-was associated with development of a hip at risk for displacement.

PMID:
42329267
Bibliographic data and abstract were imported from PubMed on 22 Jun 2026.

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