Infection in Primary Hip and Knee Arthroplasty

Field: Medicine (Health Sciences)

Since the advent of prosthetic joint replacement, patients suffering from bone and joint pathology have benefited from significant improvements in mobility and pain relief.In Australia 39,200 hip replacements and 39,500 knee replacements were performed in 2009 (Australian Orthopaedic Association National Joint Replacement Registry [AOA NJRR]) (Graves, et al. 2010).With an ageing population, the number of patients undergoing these procedures is projected to increase significantly over time.Data from the United States of America predicts that by 2030, the number of patients undergoing primary hip and knee replacement will increase by 174% and 673% respectively (Kurtz, et al. 2007).The major complication of such techniques is infection of the prosthetic device, which is associated with significant costs to individual patients and to the public health system.Significant morbidity is associated with prosthetic joint infections including the need for further operative procedures, long-term antibiotic therapy, and prolonged hospitalisation.Thereafter, the mortality rate from prosthetic joint infection is estimated to be between 1.0 to 2.7 precent (Ahnfelt, et al. 1990, Zimmerli 2006, Zimmerli, et al. 2004).Aside from the effects on the individual patient, the financial cost to the health system is considerable.The estimated hospital costs is $ 96 166 (US) per patient requiring revision arthroplasty for infection, which is 4.8 times the cost of a primary arthroplasty (Bozic & Ries 2005).This chapter examines the underlying epidemiology, diagnosis, treatment and challenges in managing this problem. Epidemiology IncidenceIdentification of prosthetic joint infection currently relies on diagnostic criteria, which include: histopathologic evidence of acute inflammation of periprosthetic tissue, presence of a sinus tract, macroscopic purulence surrounding the prosthesis observed intraoperatively or two or more positive microbiological cultures with the same organism isolated from the prosthetic joint fluid or tissue (Berbari, et al. 1998).We report a rate of prosthetic joint infection between 1.0 -2.0% in primary lower limb arthroplasty and this is congruent with current literature (Dowsey & Choong 2008, 2009, Swan, et al. 2011).In the United States the rate of infection in knee and hip arthroplasty was 0.92% and 0.88% respectively in a recent review of Medicare data.(Kurtz, et al. 2008).The majority of arthroplasty infections occur in www.intechopen.comRecent Advances in Arthroplasty 414 the two years following prosthetic joint surgery.The incidence of knee arthroplasty infection within 2 years was 1.55% decreasing to 0.46% in the subsequent 8 years.Corresponding data in the hip arthroplasty population showed an incidence of 1.63% within 2 years and 0.59% between two to ten years (Kurtz, et al. 2010, Ong, et al. 2009) Risk factorsA number of preoperative risk factors for prosthetic joint infection have been identified and these include pre-existing patient co-morbidities such as obesity, diabetes mellitus, rheumatoid arthritis and a history of prior malignancy.Body mass index (BMI) greater than 40kg/m 2 has been associated with a 9 fold increased risk of knee infection in our series (Dowsey & Choong 2009).Similar studies have shown that for every 1 kg/m 2 increase in body mass index, there was an associated 8% increase in the risk of deep prosthetic joint infection.The association between obesity and deep prosthetic infections is particularly marked in the hip arthroplasty population with the risk of infection increasing from 0.9% in patients within the normal weight range, to 9.1% in morbidly obese (Choong, et al. 2007, Dowsey & Choong 2008).Diabetes mellitus also predisposes patients to deep prosthetic joint infection with 5.3% of diabetic patients developing a prosthetic joint infection in one study (Dowsey & Choong 2009, Yang, et al. 2001).Postulated mechanisms for the increased risk include impaired leucocyte function and impaired wound healing in diabetic patients.Rheumatoid arthritis has been associated with a higher risk of deep prosthetic joint infections.Patients with rheumatoid arthritis have been reported to have a greater than 2.5 fold increase in the risk of arthroplasty infection compared to patients with osteoarthritis (Bengtson & Knutson 1991, Poss, et al. 1984).Whether this is due to impaired immunity secondary to the underlying disease or whether it is a reflection of the increased use of immunosuppressive medications in this cohort remains unclear (Berbari, et al. 2006b).A diagnosis of malignancy not involving the index joint has been identified as a risk factor for the subsequent development of prosthetic joint infection (Berbari, et al. 1998).Operative risk factors associated with deep prosthetic joint infection include higher American Society of Anaesthesiologist's (ASA) and National Nosocomial Infections Surveillance (NNIS) scores, bilateral surgery, knee arthroplasty, arthroplasty type and operating room conditions.Berbari et al showed that increasing NNIS score was associated with increasing risk of deep prosthetic joint infection; NNIS score 1 was associated with a 1.7 fold increase, increasing to 3.9 with a NNIS score of 2 (Berbari, et al. 1998).The ASA score, a component of the NNIS score, was also associated with an increased risk of arthroplasty infections (Pulido, et al. 2008).Pulido et al identified close to a six-fold increase in risk of prosthetic joint infection in patients undergoing simultaneous bilateral arthroplasty surgery.In the same study, knee arthroplasty, when compared to hip arthroplasty, was independently associated with a higher risk of developing deep prosthetic joint infection (Pulido, et al. 2008).The type of prosthesis used also appears to influence the risk of infection.A 20-fold increased risk of infection with metal hinged prosthetic knee joints compared to metal-to-plastic prostheses has been reported (Poss, et al. 1984).A number of postoperative risk factors for prosthetic joint infection have also been identified.The most important of these appears to be postoperative wound complications including the presence of superficial infection and/or wound discharge (Bengtson & Knutson 1991, Surin, et al. 1983, Wymenga, et al. 1992).Superficial infection, occurs within 30 days of the operative procedure, only involves the superficial structures and additionally How to referenceIn order to correctly reference this scholarly work, feel free to copy and paste the following: