The dual-mobility acetabular cup (DMC) has an additional bearing consisting of a mobile polyethylene component between the prosthetic head and the outer metal shell. This design has gained popularity in revision total hip arthroplasty (THA) and in primary treatment of femoral neck fractures with the anticipation of a reduced risk of THA instability. Our primary aim was to evaluate the overall revision risk of these cups on the basis of data from the Nordic Arthroplasty Register Association (NARA) database, and our secondary aim was to study specific revision causes including dislocation.
Propensity score matching for age, sex, fixation of the cup and stem, and the year of surgery (2001 to 2014) was used to match 4,520 hip fractures treated with a DMC to 4,520 hip fractures treated with conventional THA (control group). Competing risk regression analyses with revision or death as the end point were used. Revision was defined as a secondary surgical procedure in which any component of the implant was removed or exchanged. In addition, revision of the cup was analyzed.
The DMCs had a lower risk of revision compared with conventional THA, with an adjusted hazard ratio (AHR) of 0.75 (95% confidence interval [CI] = 0.62 to 0.92). This was consistent after adjusting for surgical approach. DMCs had a lower risk of revision due to dislocation (AHR = 0.45 [95% CI = 0.30 to 0.68]) but we found no difference regarding revision for deep infection. Revision of the acetabular component, both in general and due to dislocation, was more frequent with the use of conventional cups. The risk of death was higher in the DMC group (AHR = 1.49 [95% CI = 1.40 to 1.59]).
The use of a DMC as primary treatment for hip fracture was associated with a lower risk of revision in general and due to dislocation in particular. The total number of DMCs analyzed (4,520) likely exceeds any cohort of DMC-treated fractures published to date.
Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
1Department of Orthopaedics, Lund University, Skåne University Hospital, Malmö, Sweden
2The Swedish Hip Arthroplasty Register, Registercentrum VGR, Gothenburg, Sweden
3Department of Orthopaedics, Sahlgrenska University Hospital, Gothenburg, Sweden
4Department of Orthopaedic Surgery and Traumatology, Odense University Hospital, Odense, Denmark
5Department of Clinical Research, University of Southern Denmark, Odense, Denmark
6Danish Hip Arthroplasty Register, Aarhus, Denmark
7Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark
8Department of Clinical Medicine, University of Bergen, Bergen, Norway
9The Norwegian Arthroplasty Register, Department of Orthopaedic Surgery, Haukeland University Hospital, Bergen, Norway
10Department of Orthopedics and Traumatology, Turku University Hospital, Turku, Finland
E-mail address for A. Jobory: email@example.com
Investigation performed at the Department of Orthopaedics, Lund University, Skåne University Hospital, Malmö, Sweden
A commentary by Steven A. Olson, MD, is linked to the online version of this article at jbjs.org.
Disclosure: This study was funded by The NordForsk Foundation (Grant number 71025). The funding source had no influence on the study design or conclusions. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJS/F285).