Association Between the Elasticity of Hip Muscles and the Hip Migration Index in Cerebral Palsy

Abstract

Objectives-Cerebral palsy (CP) increases the risk of hip displacement during childhood. Abnormal hip muscle forces have been proposed as the predisposing factors. In CP, the amount of hip displacement is commonly evaluated by the Reimers hip migration index (MI) on an anteroposterior pelvic radiograph. To the best of our knowledge, the association between the elasticity of hip muscles measured by shear wave elastography and the MI has not been studied yet. Herein, we aimed to analyze the correlation between the elasticity of hip muscles and the MI.

Methods-Bilateral hips of 25 children with spastic CP were included prospectively in this study. Anteroposterior pelvic radiographs were used to measure the MI. Shear wave elastography was performed to evaluate the elasticity of muscles. The correlation between the MI and the elasticity of hip flexor and adductor muscle groups was assessed. Also, the association between the elasticity of agonist/antagonist muscles was analyzed.

Results-The MI showed fair to good correlations with hip flexors and adductors for both readers (0.71 >= r >= 0.52). The mean MIs of the patients +/- SDs were 22.64% +/- 7.79% for reader 1 and 21.55% +/- 8.83% for reader 2. The elasticity of agonist/antagonist muscle groups showed little/no to a weak correlation for both readers (0.32 >= r >= -0.07).

Conclusions-Although, hip flexor and adductor muscle elasticity showed a correlation with MI, it seems very hard to say that increased elasticity of hip flexor and adductor muscles causes hip dislocation.