How Often Do Patients Presenting With Severe Adolescent Idiopathic Scoliosis Have Underlying Hip Dysplasia?

Abstract

Introduction: Adolescent idiopathic scoliosis radiographic screening will often include the hips. The purpose of this study is to evaluate the prevalence of hip dysplasia by lateral center edge angle (LCEA) on scoliosis radiographs in patients presenting with severe range (>45 deg) idiopathic curves. Methods: We reviewed 200 consecutive patients (400 hips) with idiopathic scoliosis with major coronal curves ≥45 degrees between October 2009 and October 2022. The presenting scoliosis radiograph PA were reviewed for the following variables: major coronal curve direction, coronal balance, and lateral center edge angles. An LCEA value ≤18 was considered dysplastic. To assess potential measurement variability related to parallax of the scoliosis radiographs, the intermodality intraclass correlation coefficient (ICC) was measured from a subset of 20 hip LCEA values from patients with both scoliosis and pelvis radiographs. Results: A total of 200 patients [mean age: 13.6 (1.8) years; Female: 79%] were reviewed. The mean major curve (SD) was 58.6 degrees (11.4 deg). Overall 19% (37/200) patients or 11% (43/400) of hips had hip dysplasia. Of the dysplastic hips, 16% (6/43, P<0.001) were bilateral and 57% (21/43, P=0.04) were right sided. There was no association between dysplastic hip laterality and ipsilateral or contralateral coronal balance (P=0.26) or curve direction (P=0.49). The interobserver ICC for assessment of LCEA on scoliosis radiographs was 0.85, and the intermodality ICC between pelvic and scoliosis radiographs was 0.78. Conclusion: Hip dysplasia was present in 19% of patients presenting with large major curves, and many of these patients had right sided hip dysplasia. There was no association between hip dysplasia laterality and the patient’s major curve direction or coronal balance. There was good intermodality reliability (ICC=0.78) between LCEA values in patients who had both scoliosis and pelvis radiographs, and good inter-rater reliability between raters. Radiographic interpretation of adolescent idiopathic scoliosis should focus not only on the description of the curve and ruling out underlying segmentation anomalies but should also include critical assessment of the hips to exclude co-existing hip dysplasia. Level of Evidence: Therapeutic study—level IV