Constrained Liners During Acetabular Revision: Clinical Results of an Impingement Avoidance Strategy.

BACKGROUND

Instability after total hip arthroplasty (THA) remains a challenging problem. Component revision or bearing exchange can be successful; however, constraints may be necessary. This study evaluated the results of revision THA for instability that required constrained liners (CLs) to determine whether revising or retaining the acetabular component is preferred.

METHODS

This single-surgeon retrospective study included 50 consecutive patients who required a CL during acetabular revision for instability. Indications for constraint included the absence of functioning abductors and failed previous CL or dual mobility liner. A CL was used in existing cups if the cup position was deemed acceptable with a reasonable impingement-free arc of motion. If unacceptable, it was revised, or, if the internal diameter allowed, a CL was cemented into the existing cup in a "face changing" position to minimize impingement. All patients had a minimum 2-year follow-up. Recurrent instability occurred in 15 of 50 patients overall (30%). Results were analyzed, and patients were separated into the following two groups based on whether the cup/liner position was changed: group 1, cup revision or cemented CL with "face change" (FC) (n = 28), and group 2, CL implanted into existing cup without FC (n = 22).

RESULTS

Group 1 had recurrent instability in four of 28 cases (14%), whereas group 2 had instability in 11 of 22 (50%) cases (P = 0.012). Cemented liners with FC failed in four of 16 cases. Cup revision had the lowest rate of recurrent instability (zero of 12) versus 15 of 38 (39%) when the cup was retained (P = 0.01).

CONCLUSIONS

This study demonstrated significantly lower rates of recurrent instability when CLs can be positioned to minimize impingement, either by revising the cup or cementing the liner independent of the existing cup: a so-called "FC." Cup revision demonstrated the lowest rate of recurrent instability with predictable osteointegration at the mean 4-year follow-up.