Managing Protrusio Acetabuli With a Direct Anterior Approach Total Hip Replacement

Abstract

Introduction The deformities of protrusio acetabuli (PA) present unique reconstructive challenges. An incarcerated femoral head, medialized center of rotation, deficient bone stock, and associated leg length discrepancy add significant technical complexity to total hip arthroplasty (THA). Methods We retrospectively reviewed 23 THAs in 21 patients with PA who underwent direct anterior (DA) approach THA with intraoperative fluoroscopy. All acetabular defects were reconstructed with morcellized femoral head autograft using Bone Mill (Stryker Corporation, Kalamazoo, MI). Results The mean AK distance preoperatively was 8 mm (range: 1-16). Postoperatively, the degree of protrusio improved in all cases, and the mean AK distance decreased to 0 mm. All bone grafts consolidated, and no cups loosened or were revised at a mean of 5.3 years of follow-up. The mean Hip Disability and Osteoarthritis Outcome Score, Joint Replacement (HOOS, JR) at follow-up was 91. Conclusions These data suggest that the DA approach with intraoperative fluoroscopy may be a reasonable technique in the surgical management of this challenging population.

Keywords: bone graft; direct anterior approach; fluoroscopy; protrusio acetabuli; total hip replacement.

Figure 1. Anteroposterior radiograph of the pelvis showing characteristic protrusio acetabuli deformities. Note medial displacement of right femoral head past Kohler’s line, acetabular bone stock deficiency, incarcerated femoral head, and reduced hip offset and length.

Figure 2. Three examples of intraoperative fluoroscopy for real-time anteroposterior imaging of the pelvis.

(A) Right hip with medial bone restoration. (B) Right hip cup placement requiring adjunctive screw fixation for stability. (C) Left hip with trials in place for measurement of hip length and offset.

Figure 3. Measurement of radiographic outcomes after acetabular reconstruction.

(A) Anteroposterior (AP) radiograph close-up of left hip with moderate protrusio of 7.37 mm medialization. (B) AP radiograph close-up of left hip after medial autografting and corrected center of rotation. Note the medial edge of the acetabular component is now lateral to Kohler’s line.

Figure 4. Protrusio acetabuli managed with the direct anterior approach and intraoperative fluoroscopy.

(A) Preoperative anteroposterior (AP) pelvic radiograph with typical protrusio deformities. (B) AP intraoperative image to assess medial graft, cup orientation, and leg length. (C) Six-year follow-up AP pelvic radiograph with consolidation of bone graft, no radiolucent lines, restoration of offset, and correction of leg length discrepancy.