Objectives: Image Derived Instrumentation (IDI) has been introduced into regular use in modern day total knee arthroplasty (TKA) with many potential benefits touted. Despite this, much of the research involving IDI has failed to prove any significant benefit in alignment, operative time, blood loss and cost. The purpose of this study, the first of its kind, was to compare IDI with non-IDI TKA with respect to rate of revision. Methods: The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) was queried to analyse the survivorship of primary TKAs using IDI reported to the AOANJRR, between April 2009 to December 2014, compared with those without IDI instrumentation. Subgroup analysis was performed to determine the effect of polyethylene insert thickness upon IDI outcomes. The Kaplan-Meier method and proportional hazards models were used to determine the cumulative rates of revision and which prostheses or circumstances lead to an increased risk of revision. Results: In the period studied, there were 11197 primary TKAs performed utilising IDI. This was 4.8% of all primary TKAs during this period. The overall rate of revision/100 observed years was 1.07 in the PSI group, compared with, 0.82 in the standard group. This was equivalent to a hazard ratio (HR) of 1.15 (1.01,1.31; p=0.041). Posterior stabilised (PS) knees in particular showed an increased risk when compared with minimally stabilised knees when using IDI (HR=1.49; p=0.002) and non-IDI PS knees (HR=1.30; p=0.014). Subgroup analysis of the PSI (Zimmer); Signature (Vanguard) and Visionaire (Smith and Nephew) systems by polyethylene insert thickness found varied alteration in revision rates. Of the specific prosthetic combinations examined the NEXGEN CR FLEX/NEXGEN >11 mm poly (909 pts) HR 1.83 p=0.022 and GII Oxinium PS/GII <11 mm poly (868 pts) HR 1.45 p=0.049 were found to have significantly elevated risk of revision with the use of IDI. Conclusion: Using the AOANJRR we have shown that in primary TKAs, the use of IDI is associated with an increased overall revision rate. This is particularly prevalent in those knees using posterior stabilisation. The effect of polyethylene insert thickness varied dependent on manufacturer. The reasons for this cannot be determined from this analysis but suggest caution should be exercised in relation to this technology. Further study is warranted to better understand the reasons for increased revision rates.
413 Posterior Stabilisation Without Formal Debridement for The Treatment of Non-Tuberculous Pyogenic Spinal Infection in A Frail and Debilitated Population – A Systematic Review and Meta-Analysis
