Early to mid-term outcomes of the custom-made 3D-printed triflange acetabular component (aMace) : the largest UK dual-centre study

Various techniques have been described to manage massive acetabular bone loss in revision hip arthroplasty. The aMace system has gained popularity due to its custom design, which aims to restore the hip centre of rotation and provide initial mechanical stability in cases of large, non-contained defects. This study aimed to assess the short- and mid-term outcomes of patients who underwent revision surgery using the aMace system.

A retrospective review was conducted of all patients who underwent aMace implantation at two revision centres between June 2013 and October 2022, with a minimum follow-up of 12 months. Data collected included demographic details, indications for surgery, bone loss classification, reconstruction details, reoperations, complications, and functional outcomes.

A total of 52 patients underwent revision surgery, with a median follow-up of 51 months (IQR 36 to 72). The mean age was 72.9 years (40 to 87), and 86.5% (45/52) of patients were female. The mean BMI was 25.3 kg/m² (18.2 to 34.7), and the mean American Society of Anesthesiologists grade was III. Most patients had Paprosky type 3B 65.3% (34/52) or 3A 34.6% (18/52) defects. The main indications for revision were aseptic loosening 69.2% (36/52), infection 15.3% (8/52), and periprosthetic fracture 13.4% (7/52). Single-stage revision was performed in 76.9% (40/52), and 67.3% (35/52) underwent both cup and femoral component revision. Dual-mobility bearings were used in 76.9% (40/52) of cases, including 90% (36/40) of single-stage revisions, and 86.5% (45/52) had a metal-on-polyethylene articulation. No aMace components were revised. The 30-day mortality rate was 1.9% (1/52). The overall reoperation rate was 5.7% (3/52), primarily for periprosthetic femoral fracture and dislocation. Leg length discrepancy occurred in 9.6% (5/52). Two cases of sciatic nerve palsy were transient and resolved during follow-up. Statistically significant improvements in pain and mobility were observed (p < 0.001).

Our findings support the aMace system for significant acetabular bone loss and pelvic discontinuity, with satisfactory mid-term outcomes and low complications. We recommend these procedures in specialist centres with multidisciplinary team involvement.