Radiographic and Clinical Outcomes After Direct Anterior Versus Mini Posterior Total Hip Arthroplasty

Abstract

Background: Total hip arthroplasty (THA) is a successful surgical treatment for end-stage hip arthritis. There is controversy over whether the surgical approach leads to any differences in implant sizing, implant positioning, and clinical outcomes. This study sought to compare radiographic and clinical outcomes when performing primary THA through the direct anterior approach (DAA) and posterior approach (PA).

Methods: In this retrospective cohort study of patients undergoing primary THA, 198 DAA patients were matched to 198 PA patients. Surgeries were performed by 3 fellowship-trained surgeons. Radiographic parameters analyzed were acetabular cup anteversion and abduction angles, femoral stem coronal alignment, femoral offset, and leg-length discrepancy. Postoperative complications, including periprosthetic joint infection, wound complications, periprosthetic fracture, and dislocation, were extracted from the medical record. Statistical analysis was performed to compare radiographic and clinical outcomes between groups.

Results: There were no statistically significant differences for any postoperative complications between the 2 groups. One dislocation occurred in the PA group, and no dislocations occurred in the DAA group. DAA had a longer operative time (117 vs 79 minutes, P < .01). PA had a higher increase in femoral offset compared to the contralateral limb (2.76 mm vs 1.01 mm, P < .01), higher cup anteversion (26.17° vs 23.44°, P < .001), and higher use of dual mobility components (6.06% vs 1.01%, P = .007).

Conclusions: Both DAA and PA lead to acceptable clinical and radiographic outcomes for primary THA, with significant differences noted for cup position, femoral offset, and use of dual mobility components. These differences likely represent surgeon factors to help mitigate the risk for dislocation.

Keywords: Anterior approach; Femoral offset; Posterior approach; Primary total hip arthroplasty.

Figure 1

Preoperative AP pelvis radiograph demonstrating the measurement of femoral offset using the center of the femoral head and anatomical axis of the femur.

Figure 2

Preoperative AP pelvis radiograph demonstrating the measurement of leg length discrepancy using the interteardrop line and most prominent points of the lesser trochanter. Postoperative cup anteversion measurement.

Figure 3

Postoperative AP pelvis radiograph demonstrating use of the elliptical principle and known cup diameter to measure acetabular version. Acetabular inclination is measured as the angle subtended by a horizontal reference (line across the ischial tuberosities) and a line across the rim of the cup.

Figure 4

Postoperative AP pelvis radiograph demonstrating the measurement of femoral stem coronal alignment as the angle subtended by the long axis of the femoral component and the anatomical axis of the femur.

Figure 5

Scatter plot demonstrating acetabular cup anteversion and inclination for all patients using the (a) direct anterior approach and (b) posterior approach.

Figure 6

Postoperative AP pelvis radiograph demonstrating a patient with a left hip dislocation/subluxation.