Definition of hip displacement and dislocation by acetabular dysplasia in children with cerebral palsy

Nai Kuang Wang; Shih Hsien Shen; Brian Po Jung Chen; Chia Hsieh Chang; Ken N Kuo

doi:10.1177/18632521231185294

Definition of hip displacement and dislocation by acetabular dysplasia in children with cerebral palsy

J Child Orthop. 2023 Jul 22;17(4):315-321. doi: 10.1177/18632521231185294. eCollection 2023 Aug.

Authors

Nai Kuang Wang¹, Shih Hsien Shen², Brian Po Jung Chen³, Chia Hsieh Chang³, Ken N Kuo^{4

5}

Affiliations

¹ Department of Internal Medicine, Taichung Veterans General Hospital, Taichung.
² Department of Orthopaedic Surgery, Chang Gung Memorial Hospital, Chiayi.
³ Department of Pediatric Orthopaedics, Bone and Joint Research Center, Chang Gung Memorial Hospital, Taoyuan.
⁴ Cochrane Taiwan, Taipei Medical University, Taipei.
⁵ Department of Orthopaedic Surgery, National Taiwan University Hospital, Taipei.

Abstract

Purpose: The acetabulum interacts with the femoral head in daily activities and may exhibit structural changes in the presence of hip disorders. This study aims to redefine hip disorders in children with cerebral palsy by structural characteristics of the acetabulum in relation to the degree of the migration percentage.

Methods: The clinical and radiographic data of 70 patients (36 males, 34 females; mean age 8.2 years) with spastic cerebral palsy were retrospectively analyzed. The acetabular structure was measured by the acetabular index on reconstructed three-dimensional computerized tomography for precision of measurement. Any significant change in acetabular index measured on the reconstructive computerized tomography related to every 10% increment of migration percentage was regarded as clinically significant in hip disorders.

Results: The acetabular index measured on the reconstructive computerized tomography showed an increasing trend with the increment of migration percentage. The most significant acetabular index measured on the reconstructive computerized tomography change occurred between the 20%-29% and 30%-39% migration percentage groups (p < 0.001), suggesting that a migration percentage of 30% is the starting point of hip disorder. A significant increase in the posterolateral acetabular index measured on the reconstructive computerized tomography occurred in migration percentages >50%, indicating posterolateral acetabular dysplasia. Hips with migration percentages from 80% to 100% had consistent acetabular indexes measured on the reconstructive computerized tomography values, suggesting complete dislocation and no more contact and interaction between the femoral head and acetabular fossa.

Conclusion: Structural characteristics in the acetabulum reflect hip dysfunction and potentially classify hip disorders. Results suggest the migration percentage 30% as a starting point of hip disorder and 80% as a turning point of hip dislocation in children with cerebral palsy.

Level of evidence: level IV, diagnostic study.

Keywords: Cerebral palsy; acetabular dysplasia; dislocation; hip displacement; migration percentage; three-dimensional computerized tomography.