Anterior Inferior Iliac Spine Bone Morphology in Hip Dysplasia and Its Effect on Hip Range of Motion in Total Hip Arthroplasty.

ABSTRACT

BACKGOUND Despite the fact that femoral impingement against the anterior inferior iliac spine (AIIS) is increasingly recognized, there is no description of morphologic features of the AIIS in hip dysplasia and their effect on hip range of motion (ROM) in total hip arthroplasty (THA). The purpose is to evaluate the bone morphology of the AIIS in hip dysplasia and whether its morphology affects hip ROM in THA. METHODS: Computed tomography-based simulation software was used to create 3-dimensional bone models and perform virtual simulations. Using the computed tomographic data of 85 patients (male n = 25, female n = 60, mean age 60.9) with hip osteoarthritis due to dysplasia, we measured the straight, vertical, and horizontal distances between the anteroinferior edge of the AIIS and the center of rotation in sagittal and axial views. The anterior and lateral versions of the AIIS were also measured. We calculated the ROM of flexion (Flex), and internal rotation (Int-R) in THA in the software, and analyzed the correlations among them. RESULTS: The AIIS prominence is bigger and extends more anteriorly and laterally in males than in females. Furthermore, the taller the patient, the more the AIIS extends anteriorly and laterally. We found that Flex and Int-R decreased inversely proportional to the size and lateral version of the AIIS. CONCLUSION: Our results demonstrated that the AIIS bone morphology substantially affects the ROM of Flex and Int-R especially in patients with laterally large AIIS bony anatomy in THA. Furthermore, our result indicates that the morphologic features of AIIS in hip dysplasia may be different between males and females.