Constrained acetabular liners in the instability of hip arthroplasty: what is its current role in revision surgery?

BACKGROUND: Dislocation of a total hip arthroplasty (THA) is a highly disabling complication following the implantation of primary and revision hip arthroplasties, as well as a prevalent reason for subsequent revisions. This study is designed to evaluate the survival rate, functional outcomes, and the reasons for further revision due to implant failure of Constrained Acetabular Liners (CALs). METHODS: 56 patients underwent hip revision surgery using a Constrained Acetabular Liner between June 2018 and December 2022 were retrospectively evaluated. Inclusion criteria consisted of age > 18 years, follow-up of at least 12 months, prior total hip arthroplasty or bipolar hemiarthroplasty, a history of recurrent implant dislocation, or, alternatively, the presence of a high risk of implant instability in hip revisions due to mechanical conditions. RESULTS: The average age at the time of surgery was 72.4 years (SD 12.4). 55.6% of implants were performed for recurrent dislocation of THA, 8.9% for recurrent dislocation of bipolar hemiarthroplasty, 13.3% for aseptic loosening revisions, 4.4% for adverse reactions to metal debris revision procedures, and 17.8% for two-stage revision for periprosthetic joint infection. The average follow-up at the final evaluation was 32 months (SD 12.3). The survivorship of the implant was 88.9% at final follow-up. At the final follow-up: average HHS 77.4 ± 13.2; average WOMAC 31.4 ± 13.4; average OHS 32.1 ± 6.9; and average FJS-12 69.5 ± 19.6., and 65% showed excellent or good outcomes (HHS > 80). CONCLUSIONS: The CALs assessed in this study have shown satisfactory functional outcomes, even when compared with other anti-dislocation systems available on the market. Both cemented and uncemented solutions have shown a good survival rate in the mid-term. However, their use should be reserved for selected cases.