CASE 1. A woman, who had had an arthrodesis of the left hip as a child (in 1931) as a result of tuberculosis, had an arthroplasty of that hip in 1981. The postoperative course was complicated by a late Staphylococcus aureus infection of the left hip at one year. This infection was successfully treated with limited irrigation and débridement, with retention of the implants, followed by the intravenous administration of vancomycin for one month and the oral administration of cefadroxil for another month. The patient was asymptomatic until June 25, 1996, when she was admitted to the hospital because of a suspected infection of the left hip. During the first forty-eight hours after admission, the patient became febrile and leukocytosis developed. A culture of aspirate from the hip and blood cultures were positive for Staphylococcus aureus. The prosthetic components were removed, and tobramycin-impregnated polymethylmethacrylate beads were placed. The patient was given cefazolin intravenously through the time of the reimplantion of the total hip components. In August 1996, a second irrigation and débridement was performed with replacement of the tobramycin-impregnated beads because of persistent pain and erythema of the wound. The components were successfully reimplanted four months after the patient was first seen.
CASE 2. The patient's husband was managed with a right total knee arthroplasty in 1993. He was symptom-free until July 23, 1996, when pain and redness developed in the right knee. This occurred during the period when his wife was receiving intravenous therapy with cefazolin as she awaited the second stage of the reimplantation. The husband had aspiration of the knee on July 25, 1996, and the synovial fluid was sent for culture. Pulsed-field gel electrophoresis was performed on this fluid and on blood that had been obtained from the wife one month earlier. The results confirmed that the two specimens contained indistinguishable strains of Staphylococcus aureus. The husband then had a successful two-stage reimplantation. Nasal swab analyses performed several months after the conclusion of antibiotic treatment of each patient showed that it was unlikely that either patient or the surgeon who performed the arthroplasties was a carrier of the organism.
Although it is well known that many diseases can be transmitted between sexual partners, to our knowledge there is no published report of spousal cross-infection relative to total joint arthroplasty.
The organism in our patients, coagulase-negative Staphylococcus aureus, has been increasingly implicated in the etiology of infections associated with prosthetic devices or indwelling catheters. Staphylococcus aureus is most prevalent in crowded areas where personal hygiene is suboptimum. The most common site of colonization is the anterior nares, and it has been estimated that approximately 25 per cent of the population are carriers1. The organism is transmitted through contact either with a person who has a draining lesion or with an asymptomatic carrier. The airbone spread of Staphylococcus aureus infection is rare, and the hands are the most important instrument in the transmission of the organism1. Thus, frequent and thorough hand-washing is critical in order to limit the dissemination of Staphylococcus aureus. Elimination of the nasal-carrier state, with either topical agents or oral administration of antibiotics, is another means of avoiding transmission2.
Specific strains of Staphylococcus aureus can be identified with several means, one of which is pulsed-field gel electrophoresis. This method consists of cutting bacterial DNA with specific enzymes and then subjecting it to a pulsing electrical field in an agarose gel. The gel is then stained and photographed, and the DNA bands are compared4.
The factors that are recognized as being associated with septic arthritis after total knee arthroplasty include rheumatoid arthritis, an infected or unhealed wound, and limited motion of the knee at the time of discharge from the hospital6. Risk factors for patients who are managed with a hip arthroplasty include diabetes, a breakdown of sterility during the operation, an infected wound or an unhealed wound at the time of discharge from the hospital, and postoperative urinary-tract infection3. In the present study, the husband had none of the predisposing factors for an infection at the site of a total knee arthroplasty. However, septic arthritis of the knee developed during a period when his wife had what was probably a long-standing, subacute infection at the site of a total hip arthroplasty. As the Staphylococcus aureus strains grown on culture were indistinguishable from one another on pulsed-field gel electrophoresis, we concluded that the second infection was probably a direct result of the first. Given the chronology, the bacterial transmission probably occurred before the wife was seen initially on June 25, 1996.
With the difficulty, costs, and disability associated with the treatment of infection after total joint arthroplasty, additional precautions may be warranted under similar circumstances. These precautions include strict hand-washing in the home, vigilant monitoring of indications of an infection, and early intervention if such indications are observed. As joint replacement becomes more common in our aging society, the occurrence of similar situations involving married couples is likely to increase. The risk of cross-infection can potentially be decreased with the proper preventative measures.
NOTE: The authors thank David H. Pershing, M.D., Ph.D., for molecular microbiology consultation.