Prevention of dislocation in total hip revision surgery using a dual mobility design.

BACKGROUND: Postoperative dislocation is the commonest complication following revision total hip arthroplasty (THA). HYPOTHESIS AND TYPE OF STUDY: Dual mobility cups are supposed to reduce the risk of THA instability. The present retrospective study tested this hypothesis on revision THAs and also, assessed this design contribution to acetabular fixation longevity.

MATERIALS AND METHODS: The series was homogeneous and continuous, comprising a total of 163 revision THAs: 110 of them were bipolar revisions and 53 were restricted to the acetabular component exchange. Mean patient age was 68.7 years (range: 34-92 years). Novae (SERF, Décines) dual mobility cups were used in all cases: 110 cementless cups were used and 53 cups were cemented in a Kerboull reinforcement ring due to severe acetabular bone loss.

RESULTS: Mean patients' follow-up (FU) was 60.4 + or - 17.6 months. There were six early dislocations (which were reduced without additional surgery and remained recurrence-free) and two cases of acetabular loosening. The total postoperative dislocation rate at the end of follow-up was 3.7% and the 7-year cup survivorship rate was 96.1% (95% CI: 92.8-99.2%). In revision for aseptic loosening, the instability rate was 2.9%; in the higher instability risk groups (i.e., revision for infection and or recurrent instability) the dislocation rate was respectively 9% and 0%.

DISCUSSION: Dual mobility cups provided a dislocation rate of only 3.7% in revision THA, comparable to the one reported with standard implants for primary THA. This kind of cup design is especially suited to deal with high instability risk revision cases, where constrained components are generally recommended. It can also be indicated in cases of aseptic loosening, where it resulted in a 2.9% dislocation rate and only two impending failures of fixation. In terms of mechanical failure rate, these numbers compare well to the ones pertaining to tripolar and constrained implants. These later alternatives remain possible options but are not fully efficient in terms of long-term stability and fixation longevity. LEVEL OF STUDY: Level IV, retrospective or records-based.