Methicillin Resistant Staphylococcus Aureus (MRSA) screening has reduced rates of MRSA infection in primary total hip (THR) and total knee (TKR) replacements. There are reports of increasing methicillin resistance (MR) in Coagulase Negative Staphylococci (CNS) causing arthroplasty infections. We examined microbiological results of all 2-stage THR/TKR revisions in Tayside from 2001–2010. 72 revisions in 67 patients were included; 30 THRs and 42 TKRs. Mean ages at revision were 89 and 72 years respectively. Male: female ratio 1.4:1.2-year survivorship for all endpoints: 96% in THRs and 88% in TKRs. 5-year survival: 83% and 84% respectively. The most common organisms were SA (30%) and CNS (29%). Antibiotic resistance was more common amongst CNS. 72% of CNS were resistant to Methicillin versus 20% of SA. 80% of CNS were resistant to Gentamicin OR Methicillin versus 20% of SA. 32% (8/72 cases or 11% overall) of CNS were resistant to BOTH Gentamicin AND Methicillin, the primary arthroplasty antibiotic prophylaxis in our region, versus 4% of SA. Harris Hip Scores and Knee Society Scores were lower post primary, prior to symptoms of infection in patients who had MR organisms cultured compared with those who had methicillin sensitive organisms. One-year post revision both groups recovered to similar scores. Our data suggest MR-CNS cause significantly more arthroplasty infections than MRSA. Patients developing MR infections tend to have poorer post-primary knee and hip scores before symptoms of infection fully develop. 32% of CNS causing arthroplasty infections in our region are resistant to current routine primary antibiotic prophylaxis.
Two stage revision for infection is considered the gold standard with a success rate of 80–90%. Overall functional outcomes of these patients are commonly overlooked. There is a trend towards single stage revision to improve functional outcomes. We examined the functional scores of 2 stage revision for total hip arthroplasty (THR) and total knee arthroplasty (TKR). 72 revisions were identified over 9 years: 30 THR and 42 TKR. Two year survivorship was 96% in THR revision and 88% TKR revision. Five year survival was 83% and 84% respectively. 50 patients (without recurrence of infection) had recorded functional scores at a minimum of 1 year. The mean Harris-hip score (HHS) of THR was 75 (21 patients) prior to developing symptoms of infection. Once infected, the mean score fell to 46. At 1 year post revision it returned to 77. At 3 years HHS of 78 (12 patients) and at 5 yrs 62 (3 patients). The mean knee society score (KSS) of TKR was 66 (29 patients) prior to developing symptoms of infection. Once infected, the mean score fell to 34. At 1 year post revision it returned to 73. At 3 years KSS of 76 (16 patients) and at 5 years 62 (10 patients). We conclude that functional scores of staged revisions of infected THR and TKR return to pre-morbid levels within a year of completing the second stage. Although single stage revision may have a quicker return to function, by 1 year, staged revision has comparable results.
