Deep infection following arthroplasty condemns the patient to multiple wash-out and revision procedures, protracted courses of expensive and potentially toxic antibiotics, and prolonged hospital stays with immobilisation and isolation. Revision surgery for infection is a major challenge to the surgical team and requires adherence to stringent ward and theatre protocols to avoid spread of infection to susceptible patients. The cost of treating an infected prosthesis has been estimated as being four times greater than a primary procedure [8
Recent work has identified coagulase-negative staphylococci as being most commonly cultured from infected orthopaedic prostheses [25
]. Staphylococcus epidermidis
occurs as normal flora of the skin and mucous membranes. However, in the presence of immunosuppression, neutropenia, in-dwelling catheters, mechanical heart valves and orthopaedic prostheses, it can become an opportunistic pathogen. It was the most common contaminating organism identified in this series, and is recognised as one of the most important agents of hospital-acquired infection with multi-resistant strains emerging.
Skin commensals were identified as the primary contaminating organisms in this series of cemented arthroplasties. Despite chlorhexidine showers and preparation and draping in both the induction room and in theatre, 17.8% of skin swabs were contaminated. It had previously been suggested that it is not surface bacteria that cause wound contamination, but those lying deeper in the sebaceous glands and hair follicles exposed by the surgical incision. Fairclough et al. [10
] demonstrated that 15% of surgical wounds were contaminated by organisms present on the skin prior to disinfection. They further showed that iodophor-impregnated plastic adhesive drapes applied to the operation site 24 h prior to surgery reduced wound contamination from 15 to 1.6%. Plastic incision drapes were used during all of our procedures, but only six were impregnated with iodine; thus, significant conclusions cannot be drawn regarding their use. However, it has been suggested that isopropyl alcohol should be used to “de-fat” the skin prior to painting with an iodine preparation to ensure adherence of plastic incision drapes throughout the procedure [14
Higher intraoperative contamination rates were found with prolonged operative times. At 30 min, 1.6% of samples were contaminated increasing to 2.9% and 4.1% at 60 and 90 min respectively. In concurrence with previous reports [2
], significantly lower contamination rates were related to fewer gowned personnel scrubbed for each procedure, and fewer total personnel in theatre during the procedure.
Transient immunosuppression is a worrying finding in patients undergoing arthroplasty surgery. Intraoperative blood loss appears to result in a reduced frequency of natural killer cell precursors and decreased interferon gamma postoperatively [13
]. It has also been suggested that immunosuppression following intra-articular injections of steroid may interfere with asepsis in subsequent arthroplasty surgery [18
]. Preoperative co-morbidities that could potentially result in immunosuppression, due to the disease itself or its treatment, were noted in seven patients, including rheumatoid arthritis, non-insulin-dependent diabetes mellitus, psoriatic arthritis, and ulcerative colitis. One patient on chronic steroid management of rheumatoid arthritis had a single contaminated specimen of Staphylococcus epidermidis
with no short- or medium-term clinical sequelae.
James et al. [17
] reported a 9% rate of contamination of donated femoral heads at primary hip arthroplasty. Staphylococcus epidermidis
was isolated in 77% of the positive cases. There was no significant difference in complication or revision rates in donor patients whose femoral heads had a positive culture compared with those with sterile femoral heads, at a minimum follow-up of 1 year. A high incidence of intraoperative contamination of cemented arthroplasties was noted in our series, with 18 patients exposed to noteworthy intraoperative contamination. However, this was not reflected by a similar rate of postoperative infection at medium-term follow-up, suggesting that an interdependent relationship must exist between bacterial virulence, patient immune status and wound environment. The small bacterial inoculum in each case may account for the lack of clinical sequelae. Alternatively, the therapeutic effect of perioperative intravenous antibiotic prophylaxis may be responsible. Previous studies have demonstrated the absence of systemic antibiotic prophylaxis as one of the major risk factors for the development of infection in primary hip arthroplasties [9
]. Also, the ability of bacteria to attach to various biomaterials has been shown to differ, with the lowest colony-forming units of Staphylococcus epidermidis
being associated with stainless steel and cobalt chrome implants [23
]. All of the implants used in this study comprised cobalt chrome alloys.
The majority of contamination in this study of patients undergoing cemented arthroplasty surgery was localised to the skin. Exhaustive preoperative skin preparation did not remove all organisms. Further measures, including use of ultra-clean air theatre systems, total body isolation suits, complex disinfection, draping and glove changing regimes still does not eliminate contamination from arthroplasty. Measures to reduce operative times, reduce the number of personnel in the operating room and prevent transfer of organisms from adjacent skin into the wound may help reduce intraoperative contamination rates. Further awareness of intraoperative sources of contamination and the relationship between bacterial virulence, patient immune status and wound environment may guide changes in practice to further improve infection rates.