Valgus hip with high antetorsion causes pain through posterior extraarticular FAI

Abstract

Background: Valgus hips with increased antetorsion present with lack of external rotation and posterior hip pain that is aggravated with hip extension and external rotation. This may be the result of posterior femoroacetabular impingement (FAI).

Questions/purposes: We asked whether (1) the range of motion (ROM); (2) the location of anterior and posterior bony collision zones; and (3) the prevalence of extraarticular impingement differ between valgus hips with increased antetorsion compared with normal hips and hips with idiopathic FAI.

Methods: Surface models based on CT scan reconstructions of 13 valgus hips with increased antetorsion, 22 hips with FAI, and 27 normal hips were included. Validated three-dimensional collision detection software was used to quantify the simulated hip ROM and the location of impingement on the acetabular and the femoral sides.

Results: Hips with coxa valga and antetorsion showed decreased extension, external rotation, and adduction, whereas internal rotation in 90° of flexion was increased. Impingement zones were more anteroinferior on the femur and posteroinferior on the acetabular (pelvic) side; and the zones were more frequently extraarticular, posterior, or to a lesser degree anterior against the inferior iliac spine. We found a higher prevalence of extraarticular impingement for valgus hips with increased antetorsion.

Conclusions: Valgus hips with increased antetorsion predispose to posterior extraarticular FAI and to a lesser degree anteroinferior spine impingement.

Fig. 1A–B

Two graphs showing the anterior and posterior impingement tests for the three study groups. (A) For the anterior impingement test, hips with coxa valga and antetorsion showed increased IR from 60° to 110° of flexion compared with both the normal (p < 0.001 for all flexion values in this range) and impingement groups (p < 0.001 for all flexion values in this range). (B) For the posterior impingement test, hips with coxa valga and antetorsion showed decreased ER for the evaluated range of extension compared with both the normal (p < 0.001 for all extension values) and impingement groups (p < 0.001 for all extension values).

Fig. 2A–D

The impingement zones for the anterior (A–B) and posterior (C–D) impingement tests are shown. On the acetabulum, the impingement zones were located more anterior compared with normal (p = 0.06) and more superior compared with the FAI group (p = 0.05). On the femur, the impingement zones were located more anteroinferiorly compared with normal and FAI hips (p < 0.001 for both comparisons). We found a higher prevalence of extraarticular impingement on the acetabular (A) and the femoral sides (B) for the anterior impingement test in valgus hips when compared with normal (p < 0.001) and FAI hips (p < 0.001). The posterior impingement zones of the acetabulum (C) were located more posteroinferiorly in comparison with normal (p < 0.001) and FAI hips (p < 0.001). The posterior impingement zones on the femoral side (D) did not differ between valgus hips in comparison to normal (p = 0.20) or FAI hips (p = 0.17). A higher prevalence of extraarticular impingement was found for valgus hips compared with the normal and FAI groups on the acetabular (C; p < 0.001) and femoral sides (D; p < 0.003).

Fig. 3A–E

(A) This figure shows representative cases from each study group (left: normal hip, middle: femoroacetabular impingement hip, right: valgus hip with increased antetorsion). (B) The simulated anterior impingement zones of the acetabulum are located in the anterosuperior quadrant in FAI hips (middle) and more anteroinferiorly in valgus hips with increased antetorsion (right). (C) The simulated anterior impingement zones of the femur are located more inferior in the calcar area in valgus hips with increased antetorsion (right) compared with normal hips (left) and hips with FAI (middle). (D) The simulated posterior impingement zones of the acetabulum are located in the posteroinferior quadrant of the acetabulum and extraarticularly on the ischial tuberosity in valgus hips with increased antetorsion (right). (E) On the femoral side, the posterior impingement zone in valgus hips and increased antetorsion (right) are typically located in the area of the lesser trochanter.