Hip arthroplasty : infections, thromboembolic events and surgical environment

Abstract

Background: Each year hip arthroplasties increase the quality of life for over 1 million patients worldwide. Although the complication rates are low, the absolute numbers are rising as the numbers of procedures increase. Prosthetic joint infections resulting from intraoperative contamination are regarded as compensable by the Swedish patient insurance. Healthcare personnel are obliged to inform patients about their injury and the possibility to claim it. In this thesis aspects of two complications after hip arthroplasty are discussed. Both have gone from being relatively frequent complications of uncommon procedures in the early days of hip arthroplasty, to infrequent complications of common procedures, resulting in many suffering patients. Prosthetic joint infection (Study I – III) is the most feared complication and venous thromboembolism is the most common medical complication, (Study IV).

Methods: Studies I and II are based on outcomes of operations performed at the Department of Orthopaedics, Stockholm South General Hospital (Södersjukhuset). Studies III and IV cover the nationwide population of Sweden and are based on data from national quality and healthcare registers. Study I: 3 884 patients operated between 1996 and 2005, due to degenerative hip disorder or hip fracture (primary and secondary fracture prostheses) were analysed for the incidence, microbiology and outcome of prosthetic joint infection after hip arthroplasty. Study II: Air quality in the operating room was evaluated through comparison of three clothing systems through 244 measurements of colony forming units per square meter, during 37 operations. Study III: A national cohort of prosthetic infections after total hip arthroplasties in patients operated between 2005 and 2008 has previously established. We analysed the number of filed patient claims in 441 infections and examined the incidence and outcome (accepted, rejected, approved disability). Study IV: Low molecular weight heparins and new oral anticoagulants were compared as thromboprophylaxis after 32 663 elective hip arthroplasties, through determination of effectiveness as incidence of venous thromboembolic events and assessment of safety by analysis of bleedings, reoperations and mortality.

Results: Study I: The infection rates for degenerative hip disorder and primary and secondary fracture prostheses were 0.4%, 2.1% and 2.5% respectively. The patient factors associated with a significantly increased risk for developing a surgical-site infection were both fracture indication for surgery and male gender. Staphylococcus Aureus and Coagulase-Negative Staphylococci dominated as microbiological agents. Treatment of 27 (44%) patients resulted in permanent resection arthroplasty, of which 22 (81%) were fracture patients. Study II: Compared with the two other reusable suits, the significantly lowest values of colony forming units were observed with the single-use polypropylene BARRIER® Clean Air Suit. Study III: 329 (75%) of patients did not file a claim of injury to LÖF and of those 112 that did, 108 (96%) were accepted as eligible for compensation. Patients’ age above 72 years and fracture diagnosis were the only significant factors associated with not filing a claim of injury. Study IV: Compared to low molecular weight heparins, new oral anticoagulants reduced the risk of venous thromboembolic events with more than 50% with simultaneously remained safety profile. In the subset of patients treated with low molecular weight heparins no significant difference with regards to the studied outcomes was observed.

Conclusion: Patients with fractures of the neck of femur, treated with primary or secondary fracture prostheses, have a greater risk of infection and display worse outcomes compared with patients operated due to degenerative hip disorders. Additionally, among the overall low rate of patient claims, fracture patients stand out with an even greater share of non-claimants (87%). Healthcare personnel should increase their knowledge about LÖF. Improving air quality is difficult in existing facilities. Evaluation of clothing in real-life surgical environments can, by decreased counts of airborne bacteria, result in better prevention of infections. Compared to low molecular weight heparins, thromboprophylaxis with new oral anticoagulants extending for a minimum of 28 days is a superior regimen for the majority of patients undergoing elective primary total hip arthroplasty.