Conventional single articulation constrained liners in revision hip arthroplasty: risk factors for failure and their combinations.

Background: Constrained liners (CLs) have been used in revision total hip arthroplasty (rTHA) with varying results. Relatively few studies have identified specific risk factors for failure. This study aimed to assess implant survivorship and complication rates, identify risk factors for constraint-related complications, and assess the effect of multiple factors present in a single case.

Methods: We conducted a retrospective analysis of 101 rTHAs for various aseptic indications and as second-stage procedures for periprosthetic joint infection (PJI) utilising 2 models of conventional single-articulation CLs. We excluded 8 cases in which the liners were removed early due to PJI and assessed the risk factors for constraint-related complications in the remaining 93 cases. The mean follow-up duration for complication-free cases was 6.5 years (range 4.7-10.5 years).

Results: The incidences of dislocation of a prosthetic head and loosening of the acetabular component were 19.8% and 5.0%, respectively. We also observed 8 cases where the locking ring of the liner was dislodged without dislocation (1 case required re-revision). The presence of factors related to impingement (cup retention, smaller internal diameter CLs, signs of probable impingement from the femoral side) was associated with higher rates of constraint-related complications. The presence of factors related to soft-tissue stabilisers did not increase the rate of complications. The simultaneous presence of multiple impingement-related risk factors resulted in worse outcomes.

Conclusions: CLs may be less effective for treating or preventing instability related to impingement. CLs should be used with caution or avoided when multiple impingement-related risk factors are present.