Research

Infection and rheumatoid agents

x-ref Hip, Knee, Hand, Shoulder, Foot, Spine

The discovery over a decade ago of the key role that tissue necrosis factors (TNFs), and in particular TNF-alpha, play in the nuclear mechanism of rheumatoid arthritis (conducted at the Kennedy Institute, London; now Oxford, UK) opened the door for the development of novel biological therapies for rheumatoid arthritis. With every passing year, new agents are introduced to subtly modify the autoimmune reaction that is the key disease-affecting step. These agents, however, have a profound immunosuppressive effect and ever since their introduction there has been concern in academic and arthroplasty circles about the potential to increase rates of periprosthetic infection. The incidence of infection in arthroplasty is small, as is the number of patients undergoing large joint arthroplasty taking disease-modifying antirheumatic drugs (DMARDS) of various types. This makes teasing out the excess incidence of infection associated with DMARD use (if indeed there is any) quite difficult. A collaborative team from Alabama (USA) and Ontario (Canada) have published an important review in The Lancet in which they attempt to establish a comprehensive contemporary meta-analysis quantifying serious infection rates in rheumatoids taking DMARDS. The review team designed an up-to-date meta-analysis using a comprehensive search of the indexed literature. They identified 106 studies that reported infection rates in those taking biologic and non-biologic (traditional) DMARDs. The studies were assessed using the Cochrane risk of bias tool and a Bayesian network meta-analysis model was used to establish odds ratios of serious infection in patients in whom biologic agents were used. In terms of crude odds ratios, the use of low dose biological DMARDs did not have an increased risk of serious infection (OR 0.93), but when standard dose agents (OR 1.31) or high dose (OR 1.90) were used, the risk of infection was significantly higher than for those on ‘traditional’ DMARDs. In absolute figures, around 55 excess infections can be expected in those taking biological and non-biological DMARDs compared with methotrexate alone, clearly a marked and clinically significant difference.² This study potentially highlights the risk of infection associated with taking DMARDs in rheumatoid patients. Although not specific to joint replacement, this is an important study and clearly more work is required to tease out the most effective and safest strategy for managing DMARDs in the peri-operative period following arthroplasty.

Infection rates and ‘bundles of care’ revisited

x-ref Hip, Knee, Shoulder, Foot

A turning point (in British Orthopaedics at least, and likely the wider orthopaedic community) in terms of management of arthroplasty units with ‘bundles of care’ to minimise infection rates came with a publication from Biant et al in the BMJ. This simple comparative cohort series had many flaws, but served an important purpose in highlighting the potential value of bundles of care in reducing infection rates in arthroplasty patients, a concept that has gained traction across the globe. Investigators in Iowa City (USA) have undertaken an impressive prospective study across 20 hospitals in nine states to revisit the concept of bundles of care. The research team undertook their investigation of the surgical site infection after cardiac surgery or hip and knee arthroplasty with and without decolonisation of MRSA or MSSA. Their study was a prospective comparative cohort series comparing rates of established deep infection, both before and after the institution of a pre-operative screening and decolonisation programme. Their study reports an impressive 28 218 operations pre-intervention, and 14 316 post-intervention. The authors report a moderate decrease in the rates of post-operative infection in the arthroplasty group, with a relative risk of 0.48, and a less significant improvement in the cardiac surgery group (RR 0.86). They found a modest but significant reduction in Staph. aureus infections.³ This study adds some evidence to the arguments for pre-operative screening and bundles of care, although the reduction in infection rates presented here is not as impressive as those suggested in the initial and much smaller single-centre study.