Introduction and Aims: As national total knee arthroplasty (TKA) registries evolve, there is an increasing trend towards publication of hospital and surgeon-level outcome data, with the goal of stimulating efforts to optimise the results of TKA. Such efforts first require understanding of the current mechanisms of TKA failure. Previous reports on revision TKA from tertiary referral centres lack data on the overall denominator, thus the relative importance of each failure mechanism leading to TKA revision over long term follow up remains unclear. The aim of this study was to analyse reasons for revision following primary TKA, and assess their relative frequencies over long-term follow-up. Methodology: 11,134 primary TKA performed between 2000-2015 at one of three tertiary referral hospitals were identified. ‘Failure’ was defined as patients undergoing subsequent revision surgery involving change of of one or more components or reoperation for deep periprosthetic joint infection (PJI). Patients were identified from a combination of the New Zealand National Joint Registry and individual search of patient records and clinical coding (ICD-9 and ICD-10). All relevant clinical records, radiographs, and lab results were obtained from all New Zealand hospitals to identify the primary reason for revision according to a standardised protocol. Results: A total of 357 (3.2%) failures over the 15 year period were identified. Of these, 36% were revised within one year and 56% were revised within 2 years of primary TKA. Periprosthetic joint infection (PJI) encompassed 48% of all reasons for revision, followed by aseptic loosening (15%), secondary patella resurfacing (14%), tibio-femoral instability (9%), stiffness (5%), polyethylene wear (2.5%), periprosthetic fracture (2.3%), patella maltracking (1.9%) and extensor mechanism discontinuity (0.9%). In the first 5 years following primary TKA, the most common reason for revision was PJI (52%), from 5-10 years PJI and aseptic loosening (35% each), and from 10-15 years aseptic loosening (41%). Conclusion: In this large cohort of patients with comprehensive follow up, PJI was the dominant reason for failure particularly in the first 10 years. Aseptic loosening becomes more important after 10 years follow up. Efforts to improve outcomes following primary TKA should focus on these areas, particularly prevention of PJI.
P405 Predictors of endoscopic recurrence in a long term follow up cohort of Crohn's disease patients – How effective is azathioprine? A single tertiary referral center experience
