Acetabular Liner with Focal Constraint to Prevent Dislocation After THA

Background: Dislocation continues to commonly cause failure after primary and revision total hip arthroplasty (THA). Fully constrained liners intended to prevent dislocation are nonetheless associated with a substantial incidence of failure by redislocation, mechanical failure, aseptic loosening, or a combination. Constrained liners with cutouts of the elevated rims can theoretically increase range of movement and therefore decrease the risk dislocation, but it is unclear if they do so in practice and whether they are associated with early wear or loosening.

Questions/purposes: We therefore determined (1) occurrence or recurrence of dislocation and (2) rate of complications associated with constrained implants with cutouts; and (3) assessed for early cup loosening.

Methods: We retrospectively reviewed the records of 81 patients at high risk for dislocation who had 82 constrained liners inserted for primary (n = 10) or revision (n = 72) THA between 2008 and 2010. From the records we extracted demographic and implant data and instances of recurrent dislocation, implant failure, osteolysis, loosening, or construct failure. The minimum followup was 24 months (mean, 34 months; range, 24-49 months).

Results: Three liners failed as a result of further dislocation (3%). Three deep infections occurred. One patient had progressive loosening at the shell-bone interface.

Conclusions: Our observations suggest this liner is associated with a relatively low risk of dislocation in patients at high risk for dislocation and those with recurrent dislocation.