Kaisa Huotari

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.

Impact of postdischarge surveillance on the rate of surgical site infection after orthopedic surgery.

OBJECTIVE To evaluate the impact of postdischarge surveillance on surgical site infection (SSI) rates after orthopedic surgery. SETTING Nine hospitals participating in the Finnish Hospital Infection Program. PATIENTS All patients who underwent hip or knee arthroplasty or open reduction of a femur fracture during 1999-2002. RESULTS The date of discharge was available for 11,812 procedures (90%). The median length of hospital stay was 8 days (range per hospital, 6-9 days). The overall SSI rate was 3.3% (range, 0.8%-6.4%). Of 384 SSIs detected, 216 (56%; range, 28%-90%) were detected after discharge: 93 (43%) were detected on readmission to the hospital, 73 (34%) at completion of a postdischarge questionnaire, and 23 (11%) at a follow-up visit. For 27 postdischarge SSIs (13%), the location of detection was unknown. Altogether, 32 (86%) of 37 of organ/space SSIs, 57 (80%) of 71 deep incisional SSIs, and 127 (46%) of 276 superficial incisional SSIs were detected after discharge. Most SSIs (70%) detected on readmission were severe (organ/space or deep incisional), whereas most SSIs (86%) detected at follow-up visits or at completion of a postdischarge questionnaire were superficial. Of all SSIs, 78% (range, 48%-100%) were microbiologically confirmed. Microbiologic confirmation was less common after discharge than during postoperative hospital stay (66% vs 93%; P<.001). CONCLUSIONS Postdischarge surveillance had a large impact on the rate of SSI detected after orthopedic surgery. However, postdischarge surveillance conducted by means of a questionnaire detected only a minority of deep incisional and organ/space SSIs.

Risk factors for deep surgical site infection following operative treatment of ankle fractures.

BACKGROUND Surgical site infection is one of the most common complications following ankle fracture surgery. These infections are associated with substantial morbidity and lead to increased resource utilization. Identification of risk factors is crucial for developing strategies to prevent these complications. METHODS We performed an age and sex-matched case-control study to identify patient and surgery-related risk factors for deep surgical site infection following operative ankle fracture treatment. We identified 1923 ankle fracture operations performed in 1915 patients from 2006 through 2009. A total of 131 patients with deep infection were identified and compared with an equal number of uninfected control patients. Risk factors for infection were determined with use of conditional logistic regression analysis. RESULTS The incidence of deep infection was 6.8%. Univariate analysis showed diabetes (odds ratio [OR] = 2.2, 95% confidence interval [CI] = 1.0, 4.9), alcohol abuse (OR = 3.8, 95% CI = 1.6, 9.4), fracture-dislocation (OR = 2.0, 95% CI = 1.2, 3.5), and soft-tissue injury (a Tscherne grade of ≥1) (OR = 2.6, 95% CI = 1.3, 5.3) to be significant patient-related risk factors for infection. Surgery-related risk factors were suboptimal timing of prophylactic antibiotics (OR = 1.9, 95% CI = 1.0, 3.4), difficulties encountered during surgery, (OR = 2.1, 95% CI = 1.1, 4.0), wound complications (OR = 4.8, 95% CI = 1.6, 14.0), and fracture malreduction (OR = 3.4, 95% CI = 1.3, 9.2). Independent risk factors for infection identified by multivariable analyses were tobacco use (OR = 3.7, 95% CI = 1.6, 8.5) and a duration of surgery of more than ninety minutes (OR = 2.5, 95% CI = 1.1, 5.7). Cast application in the operating room was independently associated with a decreased infection rate (OR = 0.4, 95% CI = 0.2, 0.8). CONCLUSIONS We identified several modifiable risk factors for deep surgical site infection following operative treatment of ankle fractures.

An outbreak of Streptococcus equi subspecies zooepidemicus associated with consumption of fresh goat cheese

BackgroundStreptococcus equi subspecies zooepidemicus is a rare infection in humans associated with contact with horses or consumption of unpasteurized milk products. On October 23, 2003, the National Public Health Institute was alerted that within one week three persons had been admitted to Tampere University Central Hospital (TaYS) because of S. equi subsp. zooepidemicus septicaemia. All had consumed fresh goat cheese produced in a small-scale dairy located on a farm. We conducted an investigation to determine the source and the extent of the outbreak.MethodsCases were identified from the National Infectious Disease Register. Cases were persons with S. equi subsp. zooepidemicus isolated from a normally sterile site who had illness onset 15.9-31.10.2003. All cases were telephone interviewed by using a standard questionnaire and clinical information was extracted from patient charts. Environmental and food specimens included throat swabs from two persons working in the dairy, milk from goats and raw milk tank, cheeses made of unpasteurized milk, vaginal samples of goats, and borehole well water. The isolates were characterized by ribotyping and pulsed-field gel electrophoresis (PFGE).ResultsSeven persons met the case definition; six had septicaemia and one had purulent arthritis. Five were women; the median age was 70 years (range 54–93). None of the cases were immunocompromized and none died. Six cases were identified in TaYS, and one in another university hospital in southern Finland. All had eaten goat cheese produced on the implicated farm. S. equi subsp. zooepidemicus was isolated from throat swabs, fresh goat cheese, milk tank, and vaginal samples of one goat. All human and environmental strains were indistinguishable by ribotyping and PFGE.ConclusionThe outbreak was caused by goat cheese produced from unpasteurized milk. Outbreaks caused by S. equi subsp. zooepidemicus may not be detected if streptococcal strains are only typed to the group level. S. equi subsp. zooepidemicus may be a re-emerging disease if unpasteurized milk is increasingly used for food production. Facilities using unpasteurized milk should be carefully monitored to prevent this type of outbreaks.

Clinical manifestations and outcome in Staphylococcus aureus endocarditis among injection drug users and nonaddicts: a prospective study of 74 patients.

BackgroundEndocarditis is a common complication in Staphylococcus aureus bacteremia (SAB). We compared risk factors, clinical manifestations, and outcome in a large, prospective cohort of patients with S. aureus endocarditis in injection drug users (IDUs) and in nonaddicts.MethodsFour hundred and thirty consecutive adult patients with SAB were prospectively followed up for 3 months. Definite or possible endocarditis by modified Duke criteria was found in 74 patients: 20 patients were IDUs and 54 nonaddicts.ResultsEndocarditis was more common in SAB among drug abusers (46%) than in nonaddicts (14%) (odds ratio [OR], 5.12; 95% confidence interval [CI], 2.65–9.91; P < 0.001). IDUs were significantly younger (27 ± 15 vs 65 ± 15 years, P < 0.001), had less ultimately or rapidly fatal underlying diseases (0% vs 37%, P < 0.001) or predisposing heart diseases (20% vs 50%, P = 0.03), and their SAB was more often community-acquired (95% vs 39%, P < 0.001). Right-sided endocarditis was observed in 60% of IDUs whereas 93% of nonaddicts had left-sided involvement (P < 0.001). An extracardiac deep infection was found in 85% of IDUs and in 89% of nonaddicts (P = 0.70). Arterial thromboembolic events and severe sepsis were also equally common in both groups. There was no difference in mortality between the groups at 7 days, but at 3 months it was lower among IDUs (10%) compared with nonaddicts (39%) (OR, 5.73; 95% CI, 1.20–27.25; P = 0.02).ConclusionS. aureus endocarditis in IDUs was associated with as high complication rates including extracardiac deep infections, thromboembolic events, or severe sepsis as in nonaddicts. Injection drug abuse in accordance with younger age and lack of underlying diseases were associated with lower mortality, but after adjusting by age and underlying diseases injection drug abuse was not significantly associated with mortality.

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.

The incidence of late prosthetic joint infections A registry-based study of 112,708 primary hip and knee replacements

Background and purpose — Late prosthetic joint infections (PJIs) are a growing medical challenge as more and more joint replacements are being performed and the expected lifespan of patients is increasing. We analyzed the incidence rate of late PJI and its temporal trends in a nationwide population. Patients and methods — 112,708 primary hip and knee replacements performed due to primary osteoarthritis (OA) between 1998 and 2009 were followed for a median time of 5 (1–13) years, using data from nationwide Finnish health registries. Late PJI was detected > 2 years postoperatively, and very late PJI was detected > 5 years postoperatively. Results — During the follow-up, involving 619,299 prosthesis-years, 1,345 PJIs were registered: cumulative incidence 1.20% (95% CI: 1.13–1.26) (for knees, 1.41%; for hips, 0.92%). The incidence rate of late PJI was 0.069% per prosthesis-year (CI: 0.061–0.078), and it was greater after knee replacement than after hip replacement (0.080% vs. 0.057%, p = 0.006). The incidence rate of very late PJI was 0.051% per prosthesis-year (CI: 0.042–0.063), 0.058% for knees and 0.044% for hips (p = 0.2). The incidence rate of late PJI varied between 0.041% and 0.107% during the years of observation without any temporal trend (incidence rate ratio (IRR) = 0.98, 95% CI: 0.93–1.03). Very late PJI increased from 0.026% in 2004 to 0.056% in 2010 (IRR = 1.11, 95% CI: 1.02–1.20). Interpretation — In our nationwide study, the incidence rate of late PJI after hip or knee arthroplasty was approximately 0.07% per prosthesis-year. The incidence of very late PJI appeared to increase.

Mitigation and Education

Delegates: Joseph A. Abboud, MD, Mark Altena, MD, Thomas L. Bradbury, MD, Jason H. Calhoun, MD, FACS, Douglas A. Dennis, MD, Daniel J. Del Gaizo, MD, Lluis Font-Vizcarra, MD, Kaisa Huotari, MD, Stephen L. Kates, MD, Kyung-Hoi Koo, PhD, Tad M. Mabry, MD, Calin Stefan Moucha, MD, Julio Cesar Palacio, MD, Trisha Nicole Peel, MBBS, Rudolf W. Poolman, MD, PhD, William J. Robb III, MD, Ralph Salvagno, MD, Thorsten Seyler, MD, Gabor Skaliczki, MD, Edward M. Vasarhelyi, MD, William Charles Watters III, MD

Efficacy of a novel PCR- and microarray-based method in diagnosis of a prosthetic joint infection

Background and purpose — Polymerase chain reaction (PCR) methods enable detection and species identification of many pathogens. We assessed the efficacy of a new PCR and microarray-based platform for detection of bacteria in prosthetic joint infections (PJIs). Methods — This prospective study involved 61 suspected PJIs in hip and knee prostheses and 20 negative controls. 142 samples were analyzed by Prove-it Bone and Joint assay. The laboratory staff conducting the Prove-it analysis were not aware of the results of microbiological culture and clinical findings. The results of the analysis were compared with diagnosis of PJIs defined according to the Musculoskeletal Infection Society (MSIS) criteria and with the results of microbiological culture. Results — 38 of 61 suspected PJIs met the definition of PJI according to the MSIS criteria. Of the 38 patients, the PCR detected bacteria in 31 whereas bacterial culture was positive in 28 patients. 15 of the PJI patients were undergoing antimicrobial treatment as the samples for analysis were obtained. When antimicrobial treatment had lasted 4 days or more, PCR detected bacteria in 6 of the 9 patients, but positive cultures were noted in only 2 of the 9 patients. All PCR results for the controls were negative. Of the 61 suspected PJIs, there were false-positive PCR results in 6 cases. Interpretation — The Prove-it assay was helpful in PJI diagnostics during ongoing antimicrobial treatment. Without preceding treatment with antimicrobials, PCR and microarray-based assay did not appear to give any additional information over culture.

Disease burden of prosthetic joint infections after hip and knee joint replacement in Finland during 1999–2004: capture–recapture estimation

We evaluated the Finnish Hospital Infection Program (SIRO) conducting incidence surveillance for prosthetic joint infection (PJI) from 1999 to 2004. We estimated its sensitivity using capture-recapture methods and assessed the disease burden of PJIs after hip (THA) and knee (TKA) arthroplasties (N = 13 482). The following three data sources were used: SIRO, the Finnish Arthroplasty Register (FAR), and the Finnish Patient Insurance Center (FPIC), which were cross-matched, and 129 individual PJIs were identified. After adjusting for the positive predictive value of SIRO (91%) a log-linear model including an interaction term between FAR and FPIC provided an estimated PJI rate of 1.6% [95% confidence interval (CI): 1.2-2.4] for THA and 1.3% (1.1-1.6) for TKA. Sensitivity for SIRO varied from 36% to 57%. The annual disease burden was 2.1 PJIs per 100 000 population after THA and 1.5 after TKA. The true disease burden of PJIs may be heavier than the rates from national sentinel surveillance systems usually suggest.