Predictors of outcome following two-stage revision total knee arthroplasty

Purpose Two stage revision arthroplasty remains the gold standard for peri-prosthetic joint infections of the knee. However, the functional outcomes of revision surgeries and the factors governing them require further investigation. The purpose of this study was to (a) evaluate impact of early and late stage I surgery and interval between stage I and stage II; (b) understand the impact of infecting organism and resistance; (c) to estimate long term survivorship and causes of failure. Methods A retrospective review of 86 patients, who underwent two stage revision for prosthetic joint infections of the knee, was performed. Time between onset of symptoms to stage I (T1), and T1 to re-implantation (T2), along with microbiological studies, were analysed for their impact on functional outcomes, failure modalities and survivorship. Results In this study, the mean KSS-Knee improved from 64.010.0 pre-operatively to 76.9 +/- 10.4, and 77.2 +/- 10.1 at the 5 and 10 year follow up respectively. The KSS-Function improved from 44.4 +/- 8.8 pre-operatively to 72.2 +/- 9.5 and 79.8 +/- 8.1 at 5 and 10 year follow-up respectively. This study also found that T1 and T2 remained critical factors in determining functional outcome and longevity of the implant and a delay in these intervals was a significant predictor of failure. Gram negative, poly-microbial infections and organisms with methicillin and vancomycin resistance demonstrated lower survivorship (p-value, 0.001 at 5, 10 and 12 years). Re-infections occurred in 4 cases while 9 cases failed due to aseptic causes. Conclusion Two-stage revision arthroplasty produced good functional outcomes when the infection was caused by single sensitive organism that did not exhibit high resistance to antibiotics. Stage I performed within 4 weeks and the subsequent re-implantation procedure undertaken within 6 weeks demonstrated better outcomes.