Outcomes of a Cementless Nonmodular Dual Mobility Acetabular Cup Inserted via Posterior Approach Without Technology: Mean Two-Year Follow-Up.

Abstract

Nonmodular dual mobility (DM) articulations in total hip arthroplasty (THA) aim to reduce dislocations through a large outer bearing diameter while minimizing wear via a smaller inner bearing where most motion occurs. Although routine use remains uncommon in the United States, this construct may protect against dislocation. This study aimed to evaluate clinical outcomes of a cementless, nonmodular DM acetabular cup at a mean follow-up of two years. We conducted a single-arm retrospective review of 604 primary, elective THAs using a cementless nonmodular DM acetabular cup between April 2017 and August 2024 at a single health system with at least 90 days of follow-up. All surgeries were performed by a single hip surgeon via posterior approach. Cases were planned using digital templating and performed with manual instruments without enabling technology. Clinical outcomes were collected, including 90-days readmission and revision rates, reasons for readmission and revision, and dislocation rates. At a mean follow-up of 2.0 years (range, 0.25 to 8.0), all-cause and aseptic acetabular cup implant survivorship was 99.8%. There were six revisions during the study period. There was one acetabular component (0.2%) that was revised due to cup dissociation from the pelvis. The remaining revisions included two for periprosthetic femoral fracture (0.3%), one for femoral loosening (0.2%), and two for acute periprosthetic joint infection (0.3%), none of which involved revision of the acetabular cup. There were no dislocations observed, and no patients required revision for instability. Cementless nonmodular DM acetabular cups offered excellent clinical outcomes in primary THA at a mean follow-up of 2.0 years, with no observed dislocations in 604 cases and high implant survivorship. These findings support the use of nonmodular DM implants as a viable option to achieve THA implant stability and durable fixation even when using a posterior approach without enabling technology.