infection control & hospital epidemiology
october 2015, vol. 36, no. 10
original article
Surgical Site Infection After Primary Hip and Knee Arthroplasty: A Cohort Study Using a Hospital Database Leslie Grammatico-Guillon, MD, PhD;1 Sabine Baron, MD;2 Philippe Rosset, MD, PhD;3 Christophe Gaborit, Statistical Engineer;2 Louis Bernard, MD, PhD;4 Emmanuel Rusch, MD, PhD;1 Pascal Astagneau, MD, PhD5
background. objective. surveillance.
Hip or knee arthroplasty infection (HKAI) leads to heavy medical consequences even if rare.
To assess the routine use of a hospital discharge detection algorithm of prosthetic joint infection as a novel additional tool for
methods. A historic 5-year cohort study was built using a hospital database of people undergoing a first hip or knee arthroplasty in 1 French region (2.5 million inhabitants, 39 private and public hospitals): 32,678 patients with arthroplasty code plus corresponding prosthetic material code were tagged. HKAI occurrence was then tracked in the follow-up on the basis of a previously validated algorithm using International Statistical Classification of Disease, Tenth Revision, codes as well as the surgical procedures coded. HKAI density incidence was estimated during the follow-up (up to 4 years after surgery); risk factors were analyzed using Cox regression. results. A total of 604 HKAI patients were identified: 1-year HKAI incidence was1.31%, and density incidence was 2.2/100 person-years in hip and 2.5/100 person-years in knee. HKAI occurred within the first 30 days after surgery for 30% but more than 1 year after replacement for 29%. Patients aged 75 years or older, male, or having liver diseases, alcohol abuse, or ulcer sore had higher risk of infection. The inpatient case fatality in HKAI patients was 11.4%. conclusions. The hospital database method used to measure occurrence and risk factors of prosthetic joint infection helped to survey HKAI and could optimize healthcare delivery. Infect. Control Hosp. Epidemiol. 2 01 5 ;3 6 (1 0) :1 19 8 – 12 07
Surgical site infections after knee and hip replacement have been a key target recommended by the Centers for Disease Control and Prevention for epidemiological surveillance for the past couple decades.1–7 Rates of surgical site infections after total joint arthroplasty are estimated at 0.5%–6% in the United States8–10 and 0.5%–1.0% in Europe.5,11–13 Prosthetic joint infections (PJI) of the hip or knee are devastating with heavy medical consequences of multiple reoperations, prolonged hospital stay, and functional disability,5,14,15 which result in increasing financial burden and sometimes litigation, with the emotional component emphasized by the media.1–5 Results of 3 decades of surveillance give evidence about the effectiveness of these systems but highlight failures in terms of postdischarge, long-term follow-up, and completeness of data.6 This statement brings up the necessity to develop a new approach to complete these existing methods. Use of French medico-administrative databases (Programme de Médicalisation
des Systèmes d'Information) could provide a computerized PJI detection, decreasing time for reporting data.5,9,16–19 This study assessed the routine use of a hospital discharge algorithm for PJI detection and surveillance. In addition, risk factors associated with increasing PJI morbidity and mortality rates after a first hip or knee arthroplasty could be determined.
methods Study Design A historic cohort study was performed using 1 French regional hospital discharge database 2008–2012, corresponding to all hospital stays from residents of this region (Région Centre, 2.5 million inhabitants, 38 private and public hospitals). Patients were selected by the presence in the hospital discharge, from January 1, 2008, through December 31, 2011, of a surgical hip or knee arthroplasty procedure according to the French Common
Affiliations: 1. Service d’Information Médicale, d’Epidémiologie et d’Economie de la Santé, Centre Hospitalier Régional Universitaire de Tours, Laboratoire de santé publique, Université François Rabelais, Tours, France; 2. Unité régionale d’épidémiologie hospitalière, Centre Hospitalier Régional Universitaire de Tours, France; 3. Service de chirurgie orthopédique, Centre Hospitalier Régional Universitaire Tours, Université François Rabelais, Tours, France; 4. Service de Médecine Interne et Maladies Infectieuses, Centre Hospitalier Régional Universitaire Tours, Université François Rabelais, Tours, France; 5. Ecole des Hautes Etudes en Santé Publique & Centre de coordination pour la lutte contre les infections associées aux soins, Paris, France. Received January 21, 2015; accepted May 25, 2015; electronically published July 8, 2015 © 2015 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2015/3610-0010. DOI: 10.1017/ice.2015.148
ssi after primary joint arthroplasty
Classification of Medical Acts associated with the corresponding specific code for prosthetic material (implant code).5,20 This hospital stay database is linked to patient data owing to the encrypted anonymized number. We extracted the 32,678 patients who underwent primary knee or hip arthroplasty during the selection period (Online Appendix). Patients younger than 18 were excluded (8 patients). Follow-up started at the first hospital stay when the procedure was performed (admission day) and continued until the end of 2012. Patients were not recalled for this study but followed up through their consecutive hospital stays and discharges, regardless of the location of admission in France, either inside or outside the region. The minimum target time of follow-up was 12 months (inclusion up to December 2011 and follow-up until December 2012). Primary Outcome: PJI PJI screening was based on a hospital discharge algorithm previously validated in an investigation study (more than 1,000 medical charts checked): the positive predictive value was 87% and the negative predictive value was 98%.20 The criteria used for identifying and classifying surgical site infections were developed by different experts for PJI: orthopedic surgeons, medical doctors specialized in infectious diseases, and data in the medical information system (Appendix). This definition was based on the diagnosis and procedure codes used in the hospital database summary, their position in the summary, and the presence of specific codes, according to the international admitted clinical definition for deep PJI.13,21 Patient infection rates were calculated from the number of PJI with respect to the total number of patients who underwent hip or knee arthroplasty during the study period. In our analysis of risk factors for infection and mortality, patients were included only once, regardless of the number of arthroplasties undergone. The case fatality rate was calculated using the number of stays with in-hospital death as numerator, and all hip or knee arthroplasty patients as denominator. Covariables of Interest Variables evaluated as potential confounders were coded patient variables (comorbidities) and hospital variables table 1.
1199
(Appendix). Incidence timing and predictive factors of PJI after a primary hip or knee arthroplasty were considered as the statistical unit. Lost to follow-up in this hospital discharge cohort was defined as no further hospital readmission or the moving of the patient toward another region with possible readmission or death. Statistical Analysis The main outcome was the PJI incidence describing the occurrence of surgical site infection for different age and sex (incidence density = person-time incidence rate). We used Kaplan Meier estimates to describe PJI occurrence and overall survival. All possible explanatory variables were first tested in a univariate model (Appendix). The criterion for inclusion in the multivariate analysis was P < .2 in the univariate analysis. Joint location, age, and sex were always included. Cox proportional hazards models were used to determine the effects of different confounding factors, as well as time period, on the risk of developing PJI. Hazard ratios (HRs) and 95% CIs were calculated. We checked proportionality of hazards and logrank test by SAS, version 9.1 (SAS Institute).
resul ts Baseline Characteristics Overall, 32,678 patients underwent hip or knee arthroplasty during the study period (1.8% of the inpatient hospital stays/ year). Table 1 presents the baseline characteristics of cohort patients. The sex ratio (male/female) for replacement was 0.67. Two-thirds of replacements were hip arthroplasty (66.2%). The median (range) age at replacement was 74 (18–110) years. Among men, mean age was significantly lower (69.9 y [95% CI, 69.7–70.1 y]) than among women (73.8 y [73.7–74.0 y]). The mean length of follow-up was 427 days (14.2 months); the median (range) was 236 (1–1,217) days. Ten patients were lost to follow-up. Independent of the reason of hospital admission, two-thirds of the cohort patients were readmitted once (64.2%) and 15% were readmitted 2 times, allowing reliable hospital database follow-up of patients (Figure 1). Arthroplasty surgery
Baseline Characteristics of the Cohort Patients, 2008–2011
Patients undergoing hip or knee arthroplasty Sex ratio, M/F Age, median (range), y Follow-up, mean, d Follow-up, median (range), d Lost to follow-up, N (%) Hospital sector, N (%) Private Public ≥1 Coded comorbidity N (%) Mortality rate, N (%)
Patients with hip replacement N = 21,633 0.71 75 (18–105) 398 169 (0–1,817)
13,368 (61.7) 8,283 (38.3) 11,368 (52.5) 1,429 (6.6)
Patients with knee replacement N = 11,045 0.59 72 (19–110) 484 352 (0–1,801)
4,448 (76.6) 2,583 (23.4) 6,305 (57.2) 280 (2.5)
Overall patients N = 32,678 0.67 74 (18–110) 427 236 (1–1,217) 10 (0.03) 21,816 (66.8) 10,866 (33.2) 10,785 (33.0) 1,765 (5.4)
1200 infection control & hospital epidemiology
october 2015, vol. 36, no. 10
was mainly undergone in private hospitals (67%). In public settings, arthroplasty mainly took place in tertiary care university hospitals (53%). During follow-up, at least 1 comorbidity was coded in 33% of hospital stays. The most frequently coded comorbidities were diabetes mellitus and cardiologic diseases (Tables 2–4). Crude patient mortality was 5.4% in the whole cohort with cardiovascular diseases and cancer as the main cause of death (17% and 12%, respectively), as in the general population. At baseline, among hip replacements,
70
significant differences existed depending on the indication of arthroplasty. Among hip replacements, baseline characteristics were different according to the replacement undergone. Total hip arthroplasty was performed on coxarthrosis cases (89%), whereas partial arthroplasty surgery mostly occurred after hip fracture (80%). Coxarthrosis represented 74% of the hip replacement stays, with more male (HR = 0.88 vs 0.32 in hip fracture cases), a lower mean age (70.1 y [95% CI, 69.9– 70.3 y] vs 82.0 y [81.7–82.9 y] in hip fracture cases), and most surgical management in private sector (72% vs 32% for fracture management). Owing to the patient profile, among hip arthroplasty, mortality increased from 3% in coxarthrosis to 16% after hip fracture management.
60 Overall cohort rehospitalization HKAI rehospitalization
% of cohort patients
50
40
30
20
10
0 1
2
3
4
5
6
7
8
9
10
>10
Number of rehospitalization
fig 1. Frequency of rehospitalization after hip or knee arthroplasty (hip or knee arthroplasty infection [HKAI] hospitalization included), 2008–2012 cohort (N = 32,678 patients).
table 2.
PJI was identified in 604 of the 32,678 patients over the whole study period (Table 2). The sex ratio (male/female) was 0.86. The median (range) age of PJI patients was 75 (18–98) years, significantly lower in men (72.5 [18–98] y) than women (77 [25–98] y).The 1–year incidence of PJI was 1.31% (N = 418 patients infected during the year after replacement). Annual PJI incidence increased significantly during the 4-year period from 1.02% to 1.69% for hip-associated infections and from 0.84% to 1.33% for knee-associated infections, with a slightly lower increase for knee. Overall density incidence was 2.3 per 100 person-years (95% CI, 2.0–2.6): 2.2 per 100 person-years (2.0–2.6) in hip replacement and 2.5 per 100 person-years (2.1–2.69) in knee replacement, without significant difference. Among hip replacements, again patient characteristics were different after fracture or coxarthrosis: 2-fold more PJI after hip fracture management (2.6%) than coxarthrosis (1.3%), and more female (69% vs 42%), higher mean age (80 y vs 69.8 y), and more management in public sector (74% vs 36%), respectively. PJI occurred during the first 30 days after the replacement for 183 patients (30.3%), of which 78 (42.6%) were during the replacement hospital stay. A total of 243 patients (40.1%) were infected between 1 month and 1 year; 178 (29.5%) were infected more than 1 year after joint replacement (Figure 2). The mean time between joint replacement and PJI diagnosis
Characteristics of the Patients With Prosthetic Joint Infection, 2008–2012
Patients undergoing HKA Sex ratio, M/F Age, median (range), y Follow-up, mean, d Follow-up, median (range), d Hospital sector N (%) Private Public ≥1 Coded comorbidity, N (%) Mortality rate, N (%) NOTE.
Characteristics of Outcome Events
Patients with hip SSI N = 383
Patients with knee SSI N = 221
Overall patients N = 604
0.86 77 (18–98) 236 49 (0–1,631)
0.87 72 (24–92) 368 196 (0–1,626)
0.86 75 (18–98) 284 91 (0–1,631)
145 (37.9) 238 (62.1) 259 (67.6) 51 (13.3)
103 (46.6) 118 (53.4) 160 (72.4) 18 (8.1)
No patients were lost to follow-up. HKA, hip or knee arthroplasty; SSI, surgical site infection.
248 (41.1) 356 (58.9) 419 (69.3) 69 (11.4)
ssi after primary joint arthroplasty
table 3.
1201
Univariate and Multivariate Cox Proportional Hazards Models of HKAI Occurrence After Hip or Knee Arthroplasty Multivariate analysisa
Univariate analysis Variable Age < 75 ≥ 75 Sex Female Male Location Hip Knee
Year of replacement 2008 2009 2010 2011 Diabetes mellitus No Yes Ulcer sore No Yes Tobacco No Yes Hypertension No Yes Cardiologic device No Yes Chronic renal failure No Yes Urinary tract disorders No Yes Cancer No Yes Chronic liver diseases No Yes Alcohol abuse No Yes HIV No Yes Drug abuse No Yes Obesity No Yes
n
Incidence PJI (%)
P
Hazard ratio
(95% CI)
P
17,427 15,251
1.73 1.99
NA .12
1 1.11
Reference 0.93 1.32
NA .24
19,600 13,078
1.65 2.15
NA .003
1 1.32
Reference 1.12 1.55
NA .001
21,557 11,025 1.11 0.93
1.78 2.00
NA .83
1
Reference
NA
1.32
.25
8,514 8,091 8054 8,019
1.66 1.88 2.07 1.81
NA .001 .001 .001
1 1.48 2.19 2.77
– 1.16 1.72 2.14
29,270 3,408
1.75 2.70
NA .01
1 0.90
Reference 0.71 1.14
NA .37
31,558 1,120
1.68 6.61
NA
october 2015, vol. 36, no. 10
original article
Surgical Site Infection After Primary Hip and Knee Arthroplasty: A Cohort Study Using a Hospital Database Leslie Grammatico-Guillon, MD, PhD;1 Sabine Baron, MD;2 Philippe Rosset, MD, PhD;3 Christophe Gaborit, Statistical Engineer;2 Louis Bernard, MD, PhD;4 Emmanuel Rusch, MD, PhD;1 Pascal Astagneau, MD, PhD5
background. objective. surveillance.
Hip or knee arthroplasty infection (HKAI) leads to heavy medical consequences even if rare.
To assess the routine use of a hospital discharge detection algorithm of prosthetic joint infection as a novel additional tool for
methods. A historic 5-year cohort study was built using a hospital database of people undergoing a first hip or knee arthroplasty in 1 French region (2.5 million inhabitants, 39 private and public hospitals): 32,678 patients with arthroplasty code plus corresponding prosthetic material code were tagged. HKAI occurrence was then tracked in the follow-up on the basis of a previously validated algorithm using International Statistical Classification of Disease, Tenth Revision, codes as well as the surgical procedures coded. HKAI density incidence was estimated during the follow-up (up to 4 years after surgery); risk factors were analyzed using Cox regression. results. A total of 604 HKAI patients were identified: 1-year HKAI incidence was1.31%, and density incidence was 2.2/100 person-years in hip and 2.5/100 person-years in knee. HKAI occurred within the first 30 days after surgery for 30% but more than 1 year after replacement for 29%. Patients aged 75 years or older, male, or having liver diseases, alcohol abuse, or ulcer sore had higher risk of infection. The inpatient case fatality in HKAI patients was 11.4%. conclusions. The hospital database method used to measure occurrence and risk factors of prosthetic joint infection helped to survey HKAI and could optimize healthcare delivery. Infect. Control Hosp. Epidemiol. 2 01 5 ;3 6 (1 0) :1 19 8 – 12 07
Surgical site infections after knee and hip replacement have been a key target recommended by the Centers for Disease Control and Prevention for epidemiological surveillance for the past couple decades.1–7 Rates of surgical site infections after total joint arthroplasty are estimated at 0.5%–6% in the United States8–10 and 0.5%–1.0% in Europe.5,11–13 Prosthetic joint infections (PJI) of the hip or knee are devastating with heavy medical consequences of multiple reoperations, prolonged hospital stay, and functional disability,5,14,15 which result in increasing financial burden and sometimes litigation, with the emotional component emphasized by the media.1–5 Results of 3 decades of surveillance give evidence about the effectiveness of these systems but highlight failures in terms of postdischarge, long-term follow-up, and completeness of data.6 This statement brings up the necessity to develop a new approach to complete these existing methods. Use of French medico-administrative databases (Programme de Médicalisation
des Systèmes d'Information) could provide a computerized PJI detection, decreasing time for reporting data.5,9,16–19 This study assessed the routine use of a hospital discharge algorithm for PJI detection and surveillance. In addition, risk factors associated with increasing PJI morbidity and mortality rates after a first hip or knee arthroplasty could be determined.
methods Study Design A historic cohort study was performed using 1 French regional hospital discharge database 2008–2012, corresponding to all hospital stays from residents of this region (Région Centre, 2.5 million inhabitants, 38 private and public hospitals). Patients were selected by the presence in the hospital discharge, from January 1, 2008, through December 31, 2011, of a surgical hip or knee arthroplasty procedure according to the French Common
Affiliations: 1. Service d’Information Médicale, d’Epidémiologie et d’Economie de la Santé, Centre Hospitalier Régional Universitaire de Tours, Laboratoire de santé publique, Université François Rabelais, Tours, France; 2. Unité régionale d’épidémiologie hospitalière, Centre Hospitalier Régional Universitaire de Tours, France; 3. Service de chirurgie orthopédique, Centre Hospitalier Régional Universitaire Tours, Université François Rabelais, Tours, France; 4. Service de Médecine Interne et Maladies Infectieuses, Centre Hospitalier Régional Universitaire Tours, Université François Rabelais, Tours, France; 5. Ecole des Hautes Etudes en Santé Publique & Centre de coordination pour la lutte contre les infections associées aux soins, Paris, France. Received January 21, 2015; accepted May 25, 2015; electronically published July 8, 2015 © 2015 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2015/3610-0010. DOI: 10.1017/ice.2015.148
ssi after primary joint arthroplasty
Classification of Medical Acts associated with the corresponding specific code for prosthetic material (implant code).5,20 This hospital stay database is linked to patient data owing to the encrypted anonymized number. We extracted the 32,678 patients who underwent primary knee or hip arthroplasty during the selection period (Online Appendix). Patients younger than 18 were excluded (8 patients). Follow-up started at the first hospital stay when the procedure was performed (admission day) and continued until the end of 2012. Patients were not recalled for this study but followed up through their consecutive hospital stays and discharges, regardless of the location of admission in France, either inside or outside the region. The minimum target time of follow-up was 12 months (inclusion up to December 2011 and follow-up until December 2012). Primary Outcome: PJI PJI screening was based on a hospital discharge algorithm previously validated in an investigation study (more than 1,000 medical charts checked): the positive predictive value was 87% and the negative predictive value was 98%.20 The criteria used for identifying and classifying surgical site infections were developed by different experts for PJI: orthopedic surgeons, medical doctors specialized in infectious diseases, and data in the medical information system (Appendix). This definition was based on the diagnosis and procedure codes used in the hospital database summary, their position in the summary, and the presence of specific codes, according to the international admitted clinical definition for deep PJI.13,21 Patient infection rates were calculated from the number of PJI with respect to the total number of patients who underwent hip or knee arthroplasty during the study period. In our analysis of risk factors for infection and mortality, patients were included only once, regardless of the number of arthroplasties undergone. The case fatality rate was calculated using the number of stays with in-hospital death as numerator, and all hip or knee arthroplasty patients as denominator. Covariables of Interest Variables evaluated as potential confounders were coded patient variables (comorbidities) and hospital variables table 1.
1199
(Appendix). Incidence timing and predictive factors of PJI after a primary hip or knee arthroplasty were considered as the statistical unit. Lost to follow-up in this hospital discharge cohort was defined as no further hospital readmission or the moving of the patient toward another region with possible readmission or death. Statistical Analysis The main outcome was the PJI incidence describing the occurrence of surgical site infection for different age and sex (incidence density = person-time incidence rate). We used Kaplan Meier estimates to describe PJI occurrence and overall survival. All possible explanatory variables were first tested in a univariate model (Appendix). The criterion for inclusion in the multivariate analysis was P < .2 in the univariate analysis. Joint location, age, and sex were always included. Cox proportional hazards models were used to determine the effects of different confounding factors, as well as time period, on the risk of developing PJI. Hazard ratios (HRs) and 95% CIs were calculated. We checked proportionality of hazards and logrank test by SAS, version 9.1 (SAS Institute).
resul ts Baseline Characteristics Overall, 32,678 patients underwent hip or knee arthroplasty during the study period (1.8% of the inpatient hospital stays/ year). Table 1 presents the baseline characteristics of cohort patients. The sex ratio (male/female) for replacement was 0.67. Two-thirds of replacements were hip arthroplasty (66.2%). The median (range) age at replacement was 74 (18–110) years. Among men, mean age was significantly lower (69.9 y [95% CI, 69.7–70.1 y]) than among women (73.8 y [73.7–74.0 y]). The mean length of follow-up was 427 days (14.2 months); the median (range) was 236 (1–1,217) days. Ten patients were lost to follow-up. Independent of the reason of hospital admission, two-thirds of the cohort patients were readmitted once (64.2%) and 15% were readmitted 2 times, allowing reliable hospital database follow-up of patients (Figure 1). Arthroplasty surgery
Baseline Characteristics of the Cohort Patients, 2008–2011
Patients undergoing hip or knee arthroplasty Sex ratio, M/F Age, median (range), y Follow-up, mean, d Follow-up, median (range), d Lost to follow-up, N (%) Hospital sector, N (%) Private Public ≥1 Coded comorbidity N (%) Mortality rate, N (%)
Patients with hip replacement N = 21,633 0.71 75 (18–105) 398 169 (0–1,817)
13,368 (61.7) 8,283 (38.3) 11,368 (52.5) 1,429 (6.6)
Patients with knee replacement N = 11,045 0.59 72 (19–110) 484 352 (0–1,801)
4,448 (76.6) 2,583 (23.4) 6,305 (57.2) 280 (2.5)
Overall patients N = 32,678 0.67 74 (18–110) 427 236 (1–1,217) 10 (0.03) 21,816 (66.8) 10,866 (33.2) 10,785 (33.0) 1,765 (5.4)
1200 infection control & hospital epidemiology
october 2015, vol. 36, no. 10
was mainly undergone in private hospitals (67%). In public settings, arthroplasty mainly took place in tertiary care university hospitals (53%). During follow-up, at least 1 comorbidity was coded in 33% of hospital stays. The most frequently coded comorbidities were diabetes mellitus and cardiologic diseases (Tables 2–4). Crude patient mortality was 5.4% in the whole cohort with cardiovascular diseases and cancer as the main cause of death (17% and 12%, respectively), as in the general population. At baseline, among hip replacements,
70
significant differences existed depending on the indication of arthroplasty. Among hip replacements, baseline characteristics were different according to the replacement undergone. Total hip arthroplasty was performed on coxarthrosis cases (89%), whereas partial arthroplasty surgery mostly occurred after hip fracture (80%). Coxarthrosis represented 74% of the hip replacement stays, with more male (HR = 0.88 vs 0.32 in hip fracture cases), a lower mean age (70.1 y [95% CI, 69.9– 70.3 y] vs 82.0 y [81.7–82.9 y] in hip fracture cases), and most surgical management in private sector (72% vs 32% for fracture management). Owing to the patient profile, among hip arthroplasty, mortality increased from 3% in coxarthrosis to 16% after hip fracture management.
60 Overall cohort rehospitalization HKAI rehospitalization
% of cohort patients
50
40
30
20
10
0 1
2
3
4
5
6
7
8
9
10
>10
Number of rehospitalization
fig 1. Frequency of rehospitalization after hip or knee arthroplasty (hip or knee arthroplasty infection [HKAI] hospitalization included), 2008–2012 cohort (N = 32,678 patients).
table 2.
PJI was identified in 604 of the 32,678 patients over the whole study period (Table 2). The sex ratio (male/female) was 0.86. The median (range) age of PJI patients was 75 (18–98) years, significantly lower in men (72.5 [18–98] y) than women (77 [25–98] y).The 1–year incidence of PJI was 1.31% (N = 418 patients infected during the year after replacement). Annual PJI incidence increased significantly during the 4-year period from 1.02% to 1.69% for hip-associated infections and from 0.84% to 1.33% for knee-associated infections, with a slightly lower increase for knee. Overall density incidence was 2.3 per 100 person-years (95% CI, 2.0–2.6): 2.2 per 100 person-years (2.0–2.6) in hip replacement and 2.5 per 100 person-years (2.1–2.69) in knee replacement, without significant difference. Among hip replacements, again patient characteristics were different after fracture or coxarthrosis: 2-fold more PJI after hip fracture management (2.6%) than coxarthrosis (1.3%), and more female (69% vs 42%), higher mean age (80 y vs 69.8 y), and more management in public sector (74% vs 36%), respectively. PJI occurred during the first 30 days after the replacement for 183 patients (30.3%), of which 78 (42.6%) were during the replacement hospital stay. A total of 243 patients (40.1%) were infected between 1 month and 1 year; 178 (29.5%) were infected more than 1 year after joint replacement (Figure 2). The mean time between joint replacement and PJI diagnosis
Characteristics of the Patients With Prosthetic Joint Infection, 2008–2012
Patients undergoing HKA Sex ratio, M/F Age, median (range), y Follow-up, mean, d Follow-up, median (range), d Hospital sector N (%) Private Public ≥1 Coded comorbidity, N (%) Mortality rate, N (%) NOTE.
Characteristics of Outcome Events
Patients with hip SSI N = 383
Patients with knee SSI N = 221
Overall patients N = 604
0.86 77 (18–98) 236 49 (0–1,631)
0.87 72 (24–92) 368 196 (0–1,626)
0.86 75 (18–98) 284 91 (0–1,631)
145 (37.9) 238 (62.1) 259 (67.6) 51 (13.3)
103 (46.6) 118 (53.4) 160 (72.4) 18 (8.1)
No patients were lost to follow-up. HKA, hip or knee arthroplasty; SSI, surgical site infection.
248 (41.1) 356 (58.9) 419 (69.3) 69 (11.4)
ssi after primary joint arthroplasty
table 3.
1201
Univariate and Multivariate Cox Proportional Hazards Models of HKAI Occurrence After Hip or Knee Arthroplasty Multivariate analysisa
Univariate analysis Variable Age < 75 ≥ 75 Sex Female Male Location Hip Knee
Year of replacement 2008 2009 2010 2011 Diabetes mellitus No Yes Ulcer sore No Yes Tobacco No Yes Hypertension No Yes Cardiologic device No Yes Chronic renal failure No Yes Urinary tract disorders No Yes Cancer No Yes Chronic liver diseases No Yes Alcohol abuse No Yes HIV No Yes Drug abuse No Yes Obesity No Yes
n
Incidence PJI (%)
P
Hazard ratio
(95% CI)
P
17,427 15,251
1.73 1.99
NA .12
1 1.11
Reference 0.93 1.32
NA .24
19,600 13,078
1.65 2.15
NA .003
1 1.32
Reference 1.12 1.55
NA .001
21,557 11,025 1.11 0.93
1.78 2.00
NA .83
1
Reference
NA
1.32
.25
8,514 8,091 8054 8,019
1.66 1.88 2.07 1.81
NA .001 .001 .001
1 1.48 2.19 2.77
– 1.16 1.72 2.14
29,270 3,408
1.75 2.70
NA .01
1 0.90
Reference 0.71 1.14
NA .37
31,558 1,120
1.68 6.61
NA
