Infections in orthopaedic surgery : clinical and experimental studies

Abstract

The diagnostic difficulties, variability in outcome and the heterogeinity of the problem of orthopaedic infections stimulated the author to a study of the literature, and several clinical and experimental studies. The diagnosis prosthesis-related infection can only be reached with an acceptable degree of certainty by combination of clinical, laboratory and imaging investigations. Fourty-seven patients with a prosthetic hip infection treated in our hospital were retrospectively divided into three treatment groups: I debridement and retention of the original components, II resection arthroplasty and III removal of the prosthesis followed by immediate or staged reimplantation. Two patiens died because of the infection. The infection was succesfully eradicated initially in 44%, 73% and 94% of the patients, respectively. Removal of the prosthesis is superior for eradication of the infection, but the functional outcome of the resection arthroplasty is poor. For better functional results, an exchange of the prosthesis, when possible, is advised. To emphasise the haematogenous route as an important pathway for orthopaedic infections, a retrospective analysis of 28 children with an osteomyelitis was performed. The patients were evaluated by chart review. All children were treated surgically and treated with antibiotics subsequently. In addition to surgical intervention, six weeks of antibiotic therapy appears to be sufficient to eradicate acute as well as chronic osteomyelitis in children. In a clinical case report the development and course of a haematogenous hip prosthesis infection after an acute cholecystitis is described. A Clostridium perfringens was isolated from the infected gallbladder and after several months of the prosthesis. If patiens of a total joint prosthesis develop bacterial infections at distant sites, they should be treated immediately and aggresively with antibiotics to prevent haematogenous spread to the prosthetic joint. The so-called "race for the surface" theory, as postulated by Gristina, suggests competition between tissue and bacterial cells for implant material surfaces. If bacteria arrive first at the surface and colonise the biomaterial, an infection will develop. In an experimental animal study the question whether there is a difference in infection suspectibility of two common orthopaedic implant surfaces with a different biocompatibility (grit-blasted Ti6A14V and hydroxyapatite coated Ti6A14V) was addressed. Prior to implantation the left tibia of a rabbit was contaminated with increasing concentrations of Staphylococcus aureus. After sacrifice, bone adjecent to the implant was harvested for bacteriological, histological and histomorphometrical examination and quantification. Bacteriology and histology showed more severe infection for the HA implants as compared to the Ti implants. Histomorphometry confirms a relationship between implant loosening and infection. The results suggest that the "race for the surface theory" should be reconsidered for the more complex in vivo situation. Also the development of an experimental animal model to study haematogenous infections of cementless implants is described. A cylindrical Ti6A14V or hydroxyapatite coated Ti6A14V implant was inserted into the right tibia of rabbits. After at least 4 weeks, the implants were contaminated through selective angiography with varying doses of Staphylococcus aureus (Wood 46). After sacrifice, at least after 1 week, biopsies of bone were cultured. Injection of 5x10 8 colony forming units caused positive cultures in all cases and minimal systemetic reactions. This model is used for further studies of haematogenous implant infections.