Low Risk of Cup Fixation Failure at Ten Years Using Constrained Liners at the Same Time of Acetabular Component Revision

There remains concern that the use of constrained liners (CL) implanted simultaneously at the time of acetabular cup revision in revision total hip replacement (rTHA) may not be safe due to loss of fixation at the bone implant interface and early cup loosening. However, there is a paucity of mid to long-term literature reporting on the outcomes of this practice. Thus, the aim of this study was to determine the survival free from aseptic cup loosening (fixation failure) and all-cause re-revision in rTHA when a CL was implanted at the same time as acetabular cup revision. We retrospectively reviewed our institutional database to identify all consecutive rTHAs where a CL was implanted simultaneously at the time acetabular cup revision from 2001 to 2021. Eleven patients with less than two-year follow-up were excluded, none of whom underwent re-revision. One-hundred and seventy-four revisions (173 patients) were included in the study with a mean follow-up of 8.7 years (range two – 21.7). At the time of rTHA, the mean patient age was 70.7 years (range 25 – 91), BMI was 28.5 (range 17.1 – 60.0), and 60.9% were female. The most common indications for rTHA were instability (35%), second-stage periprosthetic joint infection (26.4%), and aseptic loosening (17.2%). All acetabular revisions had screw fixation, seven (4%) were cup-cage constructs and an additional five (2.9%) used highly porous augments to achieve stable cup fixation. Two-thirds (116) of the CLs were manufactured by one implant company and one-third (58) were from another. Thirteen percent (23) were cemented into the revision cup. Kaplan Meier Analysis was used to determine survival with all-cause re-revision and revision for cup aseptic loosening (fixation failure) as the endpoints. A total of 32 (18.3%) patients underwent re-revision at a mean time of 2.9 years (range 0.1 – 14.1). The most common reasons for re-revision were instability (14), periprosthetic joint infection (seven), and loosening of the femoral component (four). Three (1.7%) required re-revision due to aseptic loosening of the acetabular component (fixation failure) at a mean of two years (0.1 – 5.1). Acetabular component survival free from re-revision due to aseptic loosening was 98.9% (95% CI 97.3 – 100) at five-years and 98.1% (95% CI 95.8 – 100) at 10-years. There were no acetabular component fixation failures in modern highly porous shells. The all-cause re-revision-free survival was 84.9% (95% CI 79.4 – 90.3) at five-years and 79.9% (95% CI 73.0 – 86.7) at 10-years. CLs implanted at the time acetabular cup revision in rTHA have a 98.1% 10-year survival free from acetabular cup aseptic loosening (fixation failure). There were no cup fixation failures in modern highly porous shells. Thus, when necessary, implanting a CL during revision of an acetabular component with stable screw fixation is safe with an extremely low risk of cup fixation failure.