Effect of Angular Deformities of the Proximal Femur on Impingement-Free Hip Range of Motion in a Three-Dimensional Rigid Body Model. Issue 6 (November 2015)

• Record Type: Journal Article
• Authors: Vallon, Faustine; Reymond, Amélie; Fürnstahl, Philipp; Zingg, Patrick O.; Kamath, Atul F.; Snedeker, Jess; Dora, Claudio
• Is Part Of: Hip international. Volume 25:Issue 6(2015)
• Page Start: 574
• Page End: 580
• Publication Date: 2015-11
• Subjects: Femoral neck-shaft angle -- Femoral torsion -- Femoroacetabular impingement (FAI) -- Hip arthroscopy -- Hip range of motion -- 3-D computer simulation; Hip joint -- Pathophysiology -- Periodicals; Hip joint -- Diseases -- Periodicals; Hip joint -- Surgery -- Periodicals; 617.581005
• DOI: 10.5301/hipint.5000260
• Languages: English
• ISSNs: 1120-7000

Abstract

Introduction: Abnormalities in hip morphology can reduce range of motion (ROM) through femoroacetabular impingement (FAI). Structural issues, such as asphericity of the head-neck junction and regional or global acetabular over-coverage, have been extensively discussed in the literature. The effect of varying femoral neck-shaft angle or torsion on native hip range of motion, however, has been poorly studied. Our hypothesis was that varying neck-shaft angles or femoral torsion affect the impingement-free ROM of the hip and can be treated by femoral osteochondroplasty or acetabular rim resection. Material and methods: A computer-aided design tool and a 3-D model of the hip were used to simulate incremental deformation of the proximal femur. Neck-shaft angles ranging from 90-160°, and femoral torsions ranging from -15-50°, were created. Femoroacetabular impingement was defined as bone-to-bone contact within physiological hip ROM, as described in the literature. Results and conclusion: With decreasing neck-shaft angles (≤110°) or femoral torsion (≤10°), impingement occurred at the anterosuperior rim area. With increasing neck-shaft angles (≥135°) and femoral torsion (≥25°) posteroinferior or ischiofemoral impingement occurred. Acetabular rim trimming could compensate for neck-shaft angles ≥90° and femoral torsion ≥-5°, without creating acetabular dysplasia. Femoral impingement zones in low neck-shaft and low femoral torsion angles were found to be distal to the head-neck junction at the mid-cervical region. The cross-sectional area at this neck region was the smallest, and thus osteochondroplasty at this location may prove potentially dangerous.