THE SHALBY INFECTED KNEE REVISION SCORE (SIKRS): A NOVEL SCORING SYSTEM TO PREDICT THE OPTIMAL SECOND STAGE REVISION PROCEDURE IN PERIPROSTHETIC JOINT INFECTION

Purpose This study assessed the ability of the novel Shalby Infected Knee Revision Surgery (SIKRS) score to predict the optimal 2nd stage procedure and risk of failure of a two-stage revision total knee arthroplasty (TKA) for periprosthetic joint infection (PJI). Methods This prospective study included patients who had undergone stage 1 revision TKA for PJI. The SIKRS score was designed based on number of previous surgeries, skin condition, co-morbidities, and type of organism involved. A stage 2 revision TKA was advised for a score ≤25 (category A), an alternative procedure (arthrodesis) for a score ≥40 (category C), and a choice between stage 2 revision TKA and alternative procedure after discussion with the patient for a score between 30-35 (category B). The SIKRS score was applied to each patient in the absence of any sign or symptom of active infection for atleast 12 months. Data was analyzed for outcomes and the positive predictive value (PPV) of SIKRS at a minimum follow-up of 12 & 24 months. Results A total of 57 stage 1 revision TKAs who underwent stage 2 revision procedures were analyzed. There were 42 knees in category A, 7 knees in category B, and 8 knees in category C. At a mean follow-up of 24±7.5 months, mean preoperative total KSS of 91.5±38.5 improved significantly (p<0.0001) to 137.2±27.3. At a minimum 12 months follow-up, there were 42 successes and 0 failures for score ≤25 with PPV of 100%; 4 successes and 3 failures for score 30-35 with PPV of 57.1%; 8 successes and 0 failures for score ≥40 with PPV of 100%; and an overall failure rate of 5.3%. At a minimum 24 months follow-up, there were 24 successes and 0 failures for score ≤25 with PPV of 100%; 3 successes and 2 failures for score 30-35 with PPV of 60%; 2 successes and 0 failures for score ≥40 with PPV of 100%, and an overall failure rate of 6.5%. Conclusion The SIKRS score was useful in predicting success or failure of a stage 2 procedure at a minimum follow-up of 24 months. A score of ≤25 indicates that a stage 2 revision TKA can be performed with minimal chances of failure. The SIKRS score is an attempt to objectify decision-making in a rather ambiguous situation and can may help surgeons identify patients where stage 2 revision TKA can be performed.