Early Intraprosthetic Dislocation of Dual- Mobility Total Hip Arthroplasty Implant Following Attempted Closed Reduction: A Case Report

Introduced in 1974 by Bousquet, the dual-mobility bearing for use in total hip arthroplasty (THA) confers increased jump distance and improved overall stability relative to conventional THA designs [1-3]. The dual-mobility bearing incorporates a relatively small (22-28mm) metal or ceramic femoral head press fit into a larger polyethylene liner which articulates with the acetabular component. Dissociation of the femoral head from the polyethylene liner (intraprosthetic dislocation) is a known late complication thought to be related to polyethylene liner wear and has been previously reported [2-7]. In a consecutive series of 384 primary THAs employing Bousquet’s original design, there were 14 intraprosthetic dislocations over 15 years (3.6%). The authors cited polyethylene wear as causative and mean time to intraprosthetic dislocation was 8.9 years [2]. A recent investigation by Hamadouche et al. reported a 2.4% rate of intraprosthetic dislocation among 168 consecutive primary THAs followed for a minimum of 5-years [5]. The dislocations occurred at a mean 5.9 years and were thought to be secondary to wear at the mobile insert. A case report from the UK describes an intraprosthetic dislocation of a dual mobility implant occurring 1.5 years after primary THA [8]. There have been no reports in North America of early intraprosthetic dislocation following use of dual mobility implants for primary THA. Three recent case reports describe early (within 14 months) intraprosthetic dislocation of the dual mobility implants following attempted closed reduction of an ipsilateral hip dislocation [4,6-7]. The reports, however, concern patients in which the dual-mobility head was used in an off-label, mix-and-match fashion to revise an existing THA with retention of either the femoral stem [7] or acetabular cup [4,6]. We present a patient with intraprosthetic dislocation following attempted closed reduction of a primarily-implanted dual-mobility THA. To our knowledge, this is the first case of early intraprosthetic dislocation of a primary dual-mobility implant to be reported in North America. The purpose of the current report is to increase awareness of intraprosthetic dislocation and mitigate its risk by recommending that orthopaedic surgeons be involved with any attempted reduction of dual mobility implants.