CT reveals a high incidence of osseous abnormalities in hips with labral tears

Abstract

Background: Acetabular labral tears are being diagnosed with increasing frequency and there is a growing consensus that these tears rarely occur in the absence of osseous abnormalities.

Questions/purposes: We therefore determined the presence of structural abnormalities in patients with acetabular labral tears using a standardized CT protocol.

Methods: We evaluated 135 consecutive patients with labral tears diagnosed by MRI with CT scans of the symptomatic hip. The CT scans were evaluated in a standardized fashion to determine acetabular and femoral pathomorphologic features. Acetabular evaluation included version measurements and anterior and lateral center-edge angles. Femoral parameters evaluated included version, alpha angle, and neck-shaft angle.

Results: One hundred twenty-two (90%) of the 135 hips had structural abnormalities. One hundred two (76%) had an alpha angle greater than 50°, 18 (13%) had femoral version less than 5°, 22 (16%) had femoral version greater than 25º, and five (4%) had coxa valga. Fifty-eight (43%) patients had acetabular retroversion and five (4%) had a lateral center-edge angle less than 20º. Of the 58 patients with acetabular retroversion, 23 had isolated cranial retroversion, 12 had isolated central retroversion, and 23 had combined cranial and central retroversion. Sixty-seven of the 121 hips (55%) with bony abnormalities had a combination of abnormalities.

Conclusions: Ninety percent of patients with labral tears had structural abnormalities seen on CT scans. These structural abnormalities frequently occur in combination, and understanding these underlying morphologic features of the hip can help guide treatment.

Level of evidence: Level IV, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Figures

Fig. 1A–B

The sample measurements made for the (A) lateral center-edge angle and (B) anterior center-edge angle are shown.

Fig. 2A–D

The measurements made for (A) normal cranial and (B) central acetabular version and (C) cranial and (D) central acetabular retroversion are shown.

Fig. 3

A sample CT measurement of the neck shaft angle is shown.

Fig. 4

The alpha angle was measured by a line connecting the center of the femoral head to the center of the femoral neck and a second line connecting the center of the femoral head and the point at which the femoral head prominence exits the normal radius of the femoral head.

Fig. 5A–B

The technique for measuring the femoral version angle is shown. (A) A line is made from the base of the femoral neck through the center of the femoral head that is 10° anteverted relative to the reference line. (B) A line is made connecting the posterior femoral condyles that is 12° internally rotated relative to the reference line. In this example the patient has femoral anteversion of 22°.

Fig. 6

A 3-D reconstruction of a CT scan shows detail of osseous morphologic features.