Liner dissociation in total hip arthroplasty: a systematic review

OBJECTIVE: Liner dissociation ( LD) is a rare catastrophic mechanical failure of total hip arthroplasty (THA). The study aims at reviewing the available literature regarding liner dissociations to point out their prevalence, describing any possible association and highlighting the surgical management at the time of revision. MATERIALS AND METHODS: A systematic review of the literature was conducted from January 2002, until February 2022, according to the PRISMA guidelines. The main keywords were: "dissociation" AND "liner" OR "hip arthroplasty" OR "THA" and their MeSH terms in any possible combination. Cases of liner dissociation with all levels of evidence of any age published in indexed journals were included. The study quality of all included studies was evaluated using the MINORS criteria. The kappa (k) value was used to assess the consensus between reviewers in the selection of articles and methodological quality assessment. Finally, a sub-analysis was performed specifically concerning the elderly population. RESULTS: Thirty-one manuscripts met the inclusion criteria of the systematic review (21 case reports and 10 case series). 124 LD in 123 patients, (53% females and 47% males) were evaluated. The overall prevalence of LD was 0.15%. The mean age at surgery was of 56.5 years (range 31-75 years). LD occurred in a primary surgery setting in 86% of the cases, at a mean time of presentation of 45.8 months after replacement surgery. 39.5% of the cups and 8.8% of the stems required revision. The mean follow-up after the revision was 18.4 months. Complications after revision occurred in 19.6% of cases, including 3 cases of re-dissociations. Re-revision was required in 13.6% of the revisions. The sub-analysis of the elderly population included 28 cases of LD identified in 10 manuscripts, with an average age of 73.5 years. CONCLUSIONS: LD is a rare but catastrophic mechanical complication of modular THA that requires implant revision. The LD is not related to a specific prosthetic implant, liner material or design, acetabular positioning within the safe zone or age group.