The use of a cemented dual mobility socket to treat recurrent dislocation

Abstract

Background: The treatment of recurrent dislocation after total hip arthroplasty remains challenging. Dual mobility sockets have been associated with a low rate of dislocation but it is not known whether they are useful for treating recurrent dislocation.

Questions/purposes: We therefore asked whether a cemented dual mobility socket would (1) restore hip stability following recurrent dislocation; (2) provide a pain-free and mobile hip; and (3) show durable radiographic fixation.

Methods: We retrospectively reviewed 51 patients treated with a cemented dual mobility socket for recurrent dislocation after total hip arthroplasty between August 2002 and June 2005. The mean age at the time of the index procedure of was 71.3 years. Of the 51 patients, 47 have had complete clinical and radiographic evaluation data at a mean followup of 51.4 months (range, 25-76.3 months).

Results: The cemented dual mobility socket restored complete stability of the hip in 45 of the 47 patients (96%). The mean Merle d'Aubigné hip score was 16 ± 2 at the latest followup. Radiographic analysis revealed no or radiolucent lines less than 1 mm thick located in a single acetabular zone in 43 of 47 hips (91.5%). The cumulative survival rate of the acetabular component at 72 months using revision for dislocation and/or mechanical failure as the end point was 96% ± 4% (95% confidence interval, 90%-100%).

Conclusions: A cemented dual mobility socket was able to restore hip stability in 96% of recurrent dislocating hips. However, longer-term followup is needed to ensure that dislocation and loosening rates will not increase.

Fig. 1

Photograph of the Medial Cup® tripolar unconstrained acetabular component (Aston Medical) consisting of, from inside out, a spherical mobile polyethylene insert that accepts a 22.2- or 28-mm femoral head and is not constrained into a spherocylindrical metal shell.

Fig. 2

Diagram of the Medial cup® design indicating the medialization (1) of the center of rotation of the polyethylene insert (α) when compared with the center of rotation of the metal shell (β), the spherocylindrical design of the metal shell decreasing stresses at the periphery of the shell (2) and the good congruity between the femoral neck and the polyethylene rim (3).

Fig. 3A–D

A 66-year-old man presented with recurrent dislocation after revision THA of the right hip. (A) The patient had a THA for posttraumatic osteoarthritis 15 years after a posterior column acetabular fracture that was operated on. He experienced recurrent dislocations that were unsuccessfully treated with trochanteric advancement and augmentation of the acetabular liner. (B) A third revision was performed using a Kerboull acetabular reinforcement device with allograft and trochanteric advancement fixed with wires and a claw plate. (C) Although trochanteric consolidation was obtained, and no component malposition was noted, the patient continued to experience dislocation. (D) The patient underwent revision to a cemented tripolar unconstrained acetabular component. He described episodes of transient instability during stair climbing but is otherwise not limited in his daily activities. Fifty-one months postoperatively, the radiograph shows no radiolucent line and no sign of loosening or impingement.