Two or more impingement and/or instability deformities are often present in patients with hip pain

Abstract

Background: Damage to the hip can occur due to impingement or instability caused by anatomic factors such as femoral and acetabular version, neck-shaft angle, alpha angle, and lateral center-edge angle (CEA). The associations between these anatomic factors and how often they occur in a painful hip are unclear but if unaddressed might explain failed hip preservation surgery.

Questions/purposes: We determined (1) the influence of sex on the expression of impingement-related or instability-related factors, (2) the associations among these factors, and (3) how often both impingement and/or instability factors occur in the same hip.

Methods: We retrospectively reviewed a cohort of 170 hips (145 patients) undergoing MR arthrography of the hip for any reason. We excluded 58 hips with high-grade dysplasia, Perthes' sequelae, previous surgery, or incomplete radiographic information, leaving 112 hips (96 patients). We measured femoral version and alpha angles on MR arthrograms. Acetabular anteversion, lateral CEA, and neck-shaft angle were measured on pelvic radiographs.

Results: We observed a correlation between sex and alpha angle. Weak or no correlations were observed between the other five parameters. In 66% of hips, two or more (of five) impingement parameters, and in 51% of hips, two or more (of five) instability parameters were found.

Conclusions: Patients with hip pain frequently have several anatomic factors potentially contributing to chondrolabral damage. To address pathologic hip loading due to impingement and/or instability, all of the anatomic influences should be known. As we found no associations between anatomic factors, we recommend an individualized assessment of each painful hip.

Fig. 1

A flow diagram shows the method for inclusion of patients in the final data analysis.

Fig. 2

An AP pelvis radiograph demonstrates measurement of lateral CEA on the right hip and neck-shaft angle on the left hip.

Fig. 3A–B

(A) A line drawing demonstrates measurement of acetabular version from an AP pelvis radiograph. AV = acetabular version; SP = sagittal plane; D = diameter of circle of best fit; Line CC′ = line between acetabular centers of rotation; Line AA′A″ = line drawn perpendicular to Line CC′ at the intersection of the anterior acetabular wall; Line PP′P″ = line drawn perpendicular to Line CC′ at the intersection of the posterior acetabular wall. Acetabular version was recorded as the angle A″-P′-P″. Reprinted with permission by John Wiley & Sons, Inc, from Jamali AA, Mladenov K, Meyer DC, Martinez A, Beck M, Ganz R, Leunig M. Anteroposterior pelvic radiographs to assess acetabular retroversion: high validity of the “cross-over-sign.” J Orthop Res. 2007;25:758–765. (B) Measurement of acetabular version on a representative radiograph is shown.

Fig. 4

A line drawing demonstrates measurement of femoral version from the MR arthrogram. Reprinted with permission by the Radiological Society of North America from Sutter R, Dietrich TJ, Zingg PO, Pfirrmann CWA. Femoral antetorsion: comparing asymptomatic volunteers and patients with femoroacetabular impingement. Radiology. 2012;263:475–483.

Fig. 5A–B

(A) A scatterplot shows the association between femoral version and neck-shaft angle (r = 0.36, p < 0.001). Neck-shaft angle is a predictor of femoral version and explains 13% of the variance. (B) A scatterplot shows the weak association between femoral version and acetabular version (r = 0.22, p = 0.02). Femoral version explains 5% of the variance of acetabular version.