Fate of the Infected Unicompartmental Knee Arthroplasty: A New Zealand Joint Registry Study

Introduction Incidence of prosthetic joint infection (PJI) in Unicompartmental Knee Arthroplasty (UKA) is up to 0.8% worldwide and evidence for long term outcomes remain limited. The unique presence of implant infection in combination with native cartilage and septic arthritis have both diagnostic and management implications. This study aims to identify outcomes of PJI revision following UKA from the New Zealand Joint Registry (NZJR). Methods All UKA revisions were extracted from the NZJR. Demographic, relevant clinical and intra-operative data, reason for revision, time to revision and death were identified. Revisions and re-revisions were analysed to determine revision strategy, outcomes and survival. Results 77 UKA revisions for PJI were identified. An additional 37 re-revisions following prior revision(s) for reasons other than deep infection were analysed. Of the 77 UKA revisions, 31 were conversion to TKA and 42 were liner exchange, with 27 (83.9%) and 33 (78.6%) respectively having no further revisions for PJI. The remaining 4 were 2-stage revision (2SE) with 3 (75%) of these free from further PJI. Of the 37 re-revisions, 14 were component exchange for deep infection, following a prior revision from UKA to TKA for aseptic reasons, and none having infection recurrence. 22 were liner exchange, 1 was revision to TKA. Discussion PJI revision outcomes following UKA compare favourably to that for TKA, with single stage TKA revision comparable to 2SE. Registry data is known to outperform case series reviewing management stratified by PJI type, which is reflected here. Conclusion Liner exchange is a viable option for management of PJI following UKA with comparable success rates across groups. Higher success rates of single stage TKA could favour this as a revision strategy for UKAs in the appropriately selected patient.