Esa Jämsen

Risk factors for infection after knee arthroplasty. A register-based analysis of 43,149 cases.

BACKGROUND Clinical studies have revealed a number of important risk factors for postoperative infection following total knee arthroplasty. Because of the small numbers of cases in those studies, there is a risk of obtaining false-negative results in statistical analyses. The purpose of the present study was to determine the risk factors for infection following primary and revision knee replacement in a large register-based series. METHODS A total of 43,149 primary and revision knee arthroplasties, registered in the Finnish Arthroplasty Register, were followed for a median of three years. The Finnish Arthroplasty Register and the Finnish Hospital Discharge Register were searched for surgical interventions that were performed for the treatment of deep postoperative infections. Cox regression analysis with any reoperation performed for the treatment of infection as the end point was performed to determine the risk factors for this adverse outcome. RESULTS Three hundred and eighty-seven reoperations were performed because of infection. Both partial and complete revision total knee arthroplasty increased the risk of infection as compared with the risk following primary knee replacement. Male patients, patients with seropositive rheumatoid arthritis or with a previous fracture around the knee, and patients with constrained and hinged prostheses had increased rates of infection after primary arthroplasty. Wound-related complications increased the risk of deep infection. The rate of septic failure was lower after unicondylar than after total condylar primary knee arthroplasty, but the difference was not significant. The combination of parenteral antibiotic prophylaxis and prosthetic fixation with antibiotic-impregnated cement protected against septic failure, especially after revision knee arthroplasty. Following revision total knee arthroplasty, diagnosis and prosthesis type had no effect, but previous revision for the treatment of infection and wound-healing problems predisposed to repeat revision for the treatment of infection. CONCLUSIONS There was an increased risk of deep postoperative infection in male patients and in patients with rheumatoid arthritis or a fracture around the knee as the underlying diagnosis for knee replacement. The results of the present study suggest that the infection rate is similar after partial revision and complete revision total knee arthroplasties. Combining intravenous antibiotic prophylaxis with antibiotic-impregnated cement seems advisable in revision arthroplasty.

Obesity, diabetes, and preoperative hyperglycemia as predictors of periprosthetic joint infection: a single-center analysis of 7181 primary hip and knee replacements for osteoarthritis.

BACKGROUND Diabetes and obesity are common in patients undergoing joint replacement. Studies analyzing the effects of diabetes and obesity on the occurrence of periprosthetic joint infection have yielded contradictory results, and the combined effects of these conditions are not known. METHODS The one-year incidence of periprosthetic joint infections was analyzed in a single-center series of 7181 primary hip and knee replacements (unilateral and simultaneous bilateral) performed between 2002 and 2008 to treat osteoarthritis. The data regarding periprosthetic joint infection (defined according to Centers for Disease Control and Prevention criteria) were collected from the hospital infection register and were based on prospective, active surveillance. Patients diagnosed with diabetes were identified from the registers of the Social Insurance Institution of Finland. The odds ratios (ORs) for infection and the accompanying 95% confidence intervals (CIs) were calculated with use of binary logistic regression with adjustment for age, sex, American Society of Anesthesiologists risk score, arthroplasty site, body mass index, and diabetic status. RESULTS Fifty-two periprosthetic joint infections occurred during the first postoperative year (0.72%; 95% CI, 0.55% to 0.95%). The infection rate increased from 0.37% (95% CI, 0.15% to 0.96%) in patients with a normal body mass index to 4.66% (95% CI, 2.47% to 8.62%) in the morbidly obese group (adjusted OR, 6.4; 95% CI, 1.7 to 24.6). Diabetes more than doubled the periprosthetic joint infection risk independent of obesity (adjusted OR, 2.3; 95% CI, 1.1 to 4.7). The infection rate was highest in morbidly obese patients with diabetes; this group contained fifty-one patients and periprosthetic infection developed in five (9.8%; 95% CI, 4.26% to 20.98%). In patients without a diagnosis of diabetes at the time of the surgery, there was a trend toward a higher infection rate in association with a preoperative glucose level of ≥6.9 mmol/L (124 mg/dL) compared with <6.9 mmol/L. The infection rate was 1.15% (95% CI, 0.56% to 2.35%) in the former group compared with 0.28% (95% CI, 0.15% to 0.53%) in the latter, and the adjusted OR was 3.3 (95% CI, 0.96 to 11.0). The type of diabetes medication was not associated with the infection rate. CONCLUSIONS Diabetes and morbid obesity increased the risk of periprosthetic joint infection following primary hip and knee replacement. The benefits of joint replacement should be carefully weighed against the incidence of postoperative infection, especially in morbidly obese patients. LEVEL OF EVIDENCE Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Outcome of prosthesis exchange for infected knee arthroplasty: the effect of treatment approach

Background and purpose Two-stage revision remains the gold standard in the treatment of infected knee arthroplasty. Lately, good long-term results of direct exchange arthroplasty have been reported. The purpose of this literature review is to compare the clinical outcome achieved with one-stage revision and two-stage revision with different types of spacers. Methods A thorough systematic review of literature was undertaken to idenepsy reports on the treatment alternatives. Papers written in English or including an English abstract, published from 1980 through 2005, and reporting either the success rate in eradication of infection or the clinical status achieved were reviewed. 31 original articles describing the results of 154 one-stage exchange arthoplasties and of 926 two-stage exchange arthoplasties were included. The depth of detail in the description of materials and methods varied markedly, making it impossible to perform a meta-analysis. Instead, a descriptive review of the results is presented. Results With a follow-up of 12–122 months, the overall success rate in eradication of infection was 73–100% after one-stage revisions and 82–100% after two-stage revisions. Reinfection rates were the lowest in series where articulating cement spacers were used, though the follow-up was relatively short. Studies using articulating spacers reported the highest average postoperative ranges of motion. Otherwise, no correlations were observed between the clinical outcome and the length of follow-up, the type of revision, or the type of spacer. The clinical outcome (knee scores and range of motion) of the one-stage revisions was no different from that of the two-stage revisions. Interpretation Two-stage exchange is an effective treatment. Mobile spacers may further improve the range of motion. More experience in one-stage revision is required in order to define its role in the management of infected knee arthroplasties.

Incidence of Prosthetic Joint Infections After Primary Knee Arthroplasty

We report the 1-year incidence of postoperative infections in an unselected series of 2647 consecutive primary knee arthroplasties (3137 knees) performed in a modern specialized hospital dedicated solely to joint arthroplasty surgery in 2002 to 2006. The rates of superficial and prosthetic joint infections were 2.9% and 0.80%, respectively. Prospective surveillance by hospital infection register failed to detect 6 of the 24 prosthetic joint infections. Increased rate of prosthetic joint infections was associated with complex surgery and with several patient-related factors, for example, comorbidity, obesity, and poor preoperative clinical state. The rate of prosthetic joint infections in contemporary knee arthroplasty is low and mainly related to patient-related factors, of which patient comorbidity has the most profound effect on the infection rate.

Younger age increases the risk of early prosthesis failure following primary total knee replacement for osteoarthritis. A follow-up study of 32,019 total knee replacements in the Finnish Arthroplasty Register.

Background and purpose Total knee replacements (TKRs) are being increasingly performed in patients aged ≤ 65 years who often have high physical demands. We investigated the relation between age of the patient and prosthesis survival following primary TKR using nationwide data collected from the Finnish Arthroplasty Register. Materials From Jan 1, 1997 through Dec 31, 2003, 32,019 TKRs for primary or secondary osteoarthritis were reported to the Finnish Arthroplasty Register. The TKRs were followed until the end of 2004. During the follow-up, 909 TKRs were revised, 205 (23%) due to infection and 704 for other reasons. Results Crude overall implant survival improved with increasing age between the ages of 40 and 80. The 5-year survival rates were 92% and 95% in patients aged ≤ 55 and 56–65 years, respectively, compared to 97% in patients who were > 65 years of age (p < 0.001). The difference was mainly attributable to reasons other than infections. Sex, diagnosis, type of TKR (condylar, constrained, or hinge), use of patellar component, and fixation method were also associated with higher revision rates. However, the differences in prosthesis survival between the age groups ≤ 55, 56–65, and > 65 years remained after adjustment for these factors (p < 0.001). Interpretation Young age impairs the prognosis of TKR and is associated with increased revision rates for non-infectious reasons. Diagnosis, sex, type of TKR, use of patellar component, and fixation method partly explain the differences, but the effects of physical activity, patient demands, and obesity on implant survival in younger patients warrant further research.

Revision Total Knee Arthroplasty: 1990 Through 2002

BACKGROUND National and regional arthroplasty registries have been used to study the results of primary total knee arthroplasties. The purpose of this paper was to present the results of revision total knee replacements and describe predictors of survival of those replacements, with repeat revision as the end point. METHODS The nationwide Finnish Arthroplasty Registry included 2637 revision total knee arthroplasties from 1990 through 2002. Survivorship of the revision total knee arthroplasties was analyzed, with repeat revision as the end point. The survivorship analyses comprised evaluations of the proportional hazards assumption followed by calculations of univariate and multivariate statistics and model diagnostics as appropriate. RESULTS The survival rate following the revision total knee arthroplasties was 95% (95% confidence interval, 94% to 96%) at two years (1874 knees), 89% (95% confidence interval, 88% to 90%) at five years (944 knees), and 79% (95% confidence interval, 78% to 81%) at ten years (141 knees). Multivariate regression analysis showed the most significant predictors of prosthetic survival to be the age of the patient and the life in service of the primary total knee replacement (that is, the time between the primary total knee replacement and the revision). Survivorship was also significantly predicted by the year of the first revision total knee arthroplasty and the reason for the revision. CONCLUSIONS An age greater than seventy years, revision five years or more after the primary arthroplasty, and absence of patellar subluxation are positive indicators of survival of a revision total knee replacement. We believe that normal aging as well as the deconditioning effect of disease (osteoarthritis and rheumatoid arthritis) and its treatment (primary total knee replacement) may lead to a reduced activity level, which, together with a presumed reluctance to operate on elderly patients, protects against repeat revisions. LEVEL OF EVIDENCE Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence.

Preoperative hyperglycemia predicts infected total knee replacement

BACKGROUND Diabetes increases the risk of surgical site infections. In many patients undergoing total knee replacement, however, diabetes has not been diagnosed. The purpose of this study was to analyze the applicability of preoperative screening for hyperglycemia in identifying patients predisposed to infected knee replacement. METHODS A recent series of 1565 primary total knee replacements performed due to osteoarthritis in a specialized, publicly funded hospital for joint replacement was reviewed. RESULTS Preoperative hyperglycemia was significantly associated with infected knee replacement: during the 1-year follow-up infection occurred in 0.44%, 0.93% and 2.42% of patients with preoperative plasma glucose <6.1 mmol/l (<110 mg/dl), 6.1-6.9 mmol/l (110-125 mg/dl) and > or =7.0 mmol/l (> or =126 mg/dl). In age- and gender-adjusted analysis the patients with the highest glucose levels had a 4-fold risk for infected knee replacement compared to the patients with the lowest glucose. Obesity increased the risk of infected knee replacement, but the effect of hyperglycemia on the infection rates remained significant also after adjustment for body mass index. None of the patients with normal but 2.8% of patients with increased glycosylated hemoglobin (>6.5%) experienced infected knee replacement. CONCLUSION Obesity and hyperglycemia associate with a higher risk of infected knee replacement. Preoperative screening of plasma glucose is an efficient way to identify patients in increased risk of infection following primary total knee replacement.

Prevention of deep infection in joint replacement surgery: A review

The incidence of deep infection has declined since the early years of joint replacement surgery (Figure 1). Currently, the infection rates are low: around 1% in primary knee replacements and 0.3–0.6% in hip replacements (Phillips et al. 2006, Pulido et al. 2008, Jamsen et al. 2010). However, even prospective surveillance programs may underestimate the infection rates; thus, the true incidence is probably higher (Huotari et al. 2010). Figure 1. The cumulative revision rates (CRRs; the proportion of operated patients who underwent revision with time) with revision for infection as endpoint in consecutive cohorts of primary total knee arthroplasties (TKAs) performed in patients with osteoarthritis ... Deep infection accounts for up to one quarter of early revisions (Dobzyniak et al. 2006, Mulhall et al. 2006). Recent data from the Scandinavian arthroplasty registries show that the proportion of revision operations that are due to infection is increasing (Figure 2). Operating patients with a higher inherent infection risk, such as obese patients and those with diabetes, and emergence of resistant bacterial strains represent additional challenges, and give reason for continuous dedication to prevent deep infection. Figure 2. The proportions of infections, aseptic loosening, instability, and pain for all reasons for revision knee replacements in 1997–2008 in Denmark. Source: the Danish Knee Arthroplasty Register, Annual Report 2009 (available online at www.dkar.dk ... Patient-related infection risk can be reduced e.g. by managing preoperative anemia, glucose control, and elimination of harmful lifestyle factors such as smoking. Morbidly obese patients represent a special risk group. The principles of infection prevention in perioperative management are well-documented, but adherence to the protocols should be improved. Care should be taken regarding timely and appropriate administration of antibiotic prophylaxis. Combining intravenous antibiotics and antibiotic-impregnated cement further reduces deep infection rates. Finally, monitoring of infection rates on a local, national, and even an international scale is an essential part of quality control and is necessary in order to be able to identify weaknesses in current infection prevention practices.

Low rate of infected knee replacements in a nationwide series—is it an underestimate?: Review of the Finnish Arthroplasty Register on 38,676 operations performed in 1997 through 2003

Background and purpose Specialist hospitals have reported an incidence of early deep infections of < 1% following primary knee replacement. The purpose of this study was to estimate the infection rate in a nationwide series using register-based data. Methods The Finnish Arthroplasty Register (FAR) was searched for primary unicompartmental, total, and revision knee arthroplasties performed in 1997 through 2003 and eventual revision arthroplasties. The FAR data on revision arthroplasties was supplemented by a search of the national Hospital Discharge Register (HDR) for debridements, partial and total revision knee replacements, resection arthroplasties, arthrodeses, and amputations. Results During the first postoperative year, 0.33% (95% CI: 0.13–0.84), 0.52% (0.45–0.60) and 1.91% (1.40–2.61) of the primary UKAs, primary TKAs, and revision TKAs, respectively, were reoperated due to infection. The 1-year rate of reoperations due to infection remained constant in all arthroplasty groups over the observation period. The overall infection rate calculated using FAR data only was 0.77% (95% CI: 0.69–0.86), which was lower, but was not, however, statistically significantly different from the overall infection rate calculated using endpoint data combined from FAR and HDR records (0.89%; 95% CI: 0.80–0.99). FAR registered revision arthroplasties and patellar resurfacing arthroplasties reliably but missed a considerable proportion of other reoperations. Interpretation More reoperations performed due to infection can be expected as the numbers of knee arthroplasties increase, since there has been no improvement in the early infection rate. Finnish Arthroplasty Register data appear to underestimate the incidence of reoperations performed due to infection.

Spacer prostheses in two-stage revision of infected knee arthroplasty.

At present, no consensus exists on the best spacer alternative for the management of two-stage exchange arthroplasty of infected knee arthroplasties. In this retrospective study, patient records of 24 patients, who had undergone two-stage revisions in which resterilised prosthetic components were used as spacers, were reviewed. The outcome was compared to that of operations performed during the same period (1993–2003) using cement spacers (n=10). With an average follow-up of 32 months, control of infection was achieved in 26 cases (76%), with good or excellent clinical outcome in 19 cases (56%). Treatment failed and resulted in amputation at the level of the thigh before reimplantation in one case. Three patients did not undergo reimplantation. In four cases (12%) infection relapsed. The reinfection rate did not differ between the two spacer groups. Patients treated with resterilised components had a superior range of motion during the period between the two stages. Operative time was shorter and there was less blood loss in the reimplantation arthroplasty when a prosthetic spacer was used. We consider resterilised prosthetic components a safe and effective alternative to cement spacers in the management of infected knee arthroplasties.RésuméIl n’existe pas actuellement de consensus sur les meilleurs spacers à utiliser dans le traitement des reprises en deux temps des prothèses totales du genou infectées. Dans cette étude rétrospective, 24 patients ont été évalués, patients ayant bénéficié d’un changement prothétique en deux temps, le spacer utilisé pouvant être les composants prothétiques stérilisés. Nous avons comparé le devenir de cette série (1993–2003) à une autre série traitée pendant la même période et en utilisant un spacer en ciment (10 patients). Le délai moyen était de 32 mois et la guérison de l’infection a été obtenue dans 76% des cas (26) avec un excellent ou un bon résultat dans 19 cas (56%). Les échecs du traitement sont secondaires à une amputation de cuisse avant la réimplantation (un cas). Trois patients n’ont pas eu de réimplantation et dans 4 cas (12%) l’infection a récidivé. La récidive de l’infection n’est pas différente entre les deux groupes de patients quelle que soit la nature du spacer. Les patients traités avec des composants prothétiques re-stérilisés ont eu une meilleure mobilité pendant la période intermédiaire. Le temps opératoire et les pertes sanguines sont significativement diminués lorsque le spacer utilisé est la prothèse re-stérilisée. Nous considérons en conclusion, que la re-stérilisation du composant prothétique est une méthode sure, efficace et une bonne alternative au spacer en ciment lors du traitement des prothèses totales du genou infectées.