ORIGINAL ARTICLE INFECTIOUS DISEASES Risk factors for suerficial wound comlications in hi and knee arthrolasty K. Carroll 1, M. Dowsey 1,2, P. Choong 1,2 and T. Peel 2,3 1) Deartment of Orthoaedics, St Vincent s Hosital Melbourne, 2) Deartment of Surgery, St Vincent s Hosital, University of Melbourne and 3) Deartment of Infectious Diseases, St Vincent s Hosital Melbourne, Melbourne, Victoria, Australia Abstract Suerficial wound comlications have been consistently imlicated in the develoment of rosthetic joint infection. This cohort study aimed to determine erioerative risk factors associated with suerficial wound comlications. The study was erformed over an 18-month eriod (January 2011 to June 2012) and included 964 atients undergoing rosthetic hi or knee relacement surgery. The factors associated with suerficial wound comlication differed according to arthrolasty site. In the combined cohort the following factors were associated with suerficial wound comlications: the use of 0.5% chlorhexidine in 70% alcohol for surgical skin rearation comared with 1% iodine in 70% alcohol (odds ratio (OR) 4.75; 95% confidence interval (CI) 1.42, 15.92; = 0.012); increasing age (OR, 1.13; 95% CI, 1.06,1.19; 0.18); increasing body mass index (BMI) (OR, 1.08; 95% CI, 1.05,1.12; < 0.001); rheumatoid arthritis (OR, 2.56; 95% CI, 1.17, 5.58; 0.018); and increasing blood transfusions (OR, 1.26; 95% CI, 1.06,1.49; 0.008). In the hi arthrolasty cohort, the use of 0.5% chlorhexidine in 70% alcohol for surgical skin rearation (OR, 13.35; 95% CI, 2.11, 84.29; 0.006), increasing BMI (OR, 1.13; 95% CI, 1.06, 1.19; < 0.001) and increasing blood transfusions (OR, 1.26; 95% CI, 1.06, 1.49; 0.008) were associated with suerficial wound comlications. In the knee arthrolasty cohort rheumatoid arthritis (OR, 2.75; 95% CI, 1.03, 7.33; 0.043) and increasing tourniquet time (OR, 1.01; 95% CI, 1.00, 1.02; = 0.029) were indeendent redictors of suerficial wound comlications. Further research is warranted to assess the imact of modification of these factors on the subsequent develoment of wound comlications and rosthetic joint infection. Keywords: Arthrolasty, rosthetic joint infection, suerficial incisional surgical site infection, suerficial wound comlications Original Submission: 23 January 2013; Revised Submission: 24 February 2013; Acceted: 24 February 2013 Editor: M. Paul Article ublished online: 7 March 2013 Clin Microbiol Infect 2014; 20: 130 135 10.1111/1469-0691.12209 Corresonding author: Dr T. Peel, St Vincent s Hosital Melbourne, Deartment of Orthoaedics, 3rd Floor, Daly Wing, PO Box 2900, Fitzroy, Victoria 3065, Australia E-mail: tneel@unimelb.edu.au Introduction Prosthetic joint surgery has led to imrovement in symtoms of osteoarthritis and atient s quality of life. The oularity of this surgery continues to increase worldwide, including in Australia [1]. Data from eidemiological studies estimate that the number of knee and hi arthrolasties will increase to 4.5 million rocedures er year by 2030 in the United States of America [2]. Infective comlications of the rosthesis occur in 1 3% of atients undergoing hi and knee arthrolasty; however, they can have catastrohic consequences and often result in atient morbidity and significant cost to the ublic healthcare system [3]. In addition to the direct comlications of infection, the need for treatment with antibiotics contributes to emerging antimicrobial resistance [4]. Suerficial wound comlications, such as surgical site infection (SSI) and rolonged wound discharge, have been consistently imlicated in the develoment of rosthetic joint infection and may increase the risk of subsequent dee infection by u to 35-fold [5,6]. While there are a number of eidemiological studies examining risk factors for dee rosthetic infections in hi and knee arthrolasty, risk factors for suerficial wound comlications are not as well established. Clinical Microbiology and Infection ª2013 Euroean Society of Clinical Microbiology and Infectious Diseases
CMI Carroll et al. Arthrolasty suerficial wound comlications 131 The aims of this study were (i) to describe the incidence and severity of suerficial wound comlications in a cohort of atients undergoing hi and knee arthrolasty and (ii) to elucidate erioerative factors associated with the develoment of suerficial wound comlications. Patients and Methods Study setting and oulation This retrosective cohort study was erformed at St Vincent s Hosital Melbourne (SVHM), Victoria, Australia, an 848-bed tertiary ublic hosital. This centre comrises 16 orthoaedic surgeons erforming over 800 rosthetic hi and knee relacements er year. All hosital ostoerative care is erformed according to the SVHM Hi or Knee Relacement Clinical Pathway, which has been described reviously [7]. All atients received antibiotic rohylaxis, in keeing with national guidelines, rior to skin incision and >5 min rior to tourniquet inflation [8]. The study was erformed over an 18-month eriod (January 2011 to June 2012) and included all atients undergoing elective rimary and revision hi and knee arthrolasty during this eriod, as systematically recorded in a database rosectively comiled by the Deartment of Orthoaedics [9]. Patients were excluded if they underwent arthrolasty for fractured neck of femur, or revision arthrolasty with rior history of setic arthritis affecting the index joint, or if they were lost to follow-u. Patients were followed-u from the date of index arthrolasty until review in the orthoaedic clinic 6 weeks ost-surgery. The study design was reviewed and aroved by the SVHM Human Research Ethics Committee. Definitions Suerficial wound comlication was recorded if the atient develoed either a suerficial incisional SSI or rolonged wound ooze in the 30 days following index arthrolasty surgery. Suerficial incisional SSI was defined as er the US Centers for Diseases Control and Prevention (CDC) Criteria [10,11]. In keeing with the US CDC criteria, a suerficial incisional SSI was not recorded in the case of stitch abscess, navigation in site infection, cellulitis not in communication with the wound, or in the case that a general ractitioner commenced antibiotics for swelling, erythema or increased ain, which was not subsequently recognized as a suerficial incisional SSI by the orthoaedic surgeon or treating hysician [10]. Prolonged wound ooze was defined if there was documented drainage from the surgical incision that required intervention, such as suerficial surgical debridement, or if it led to deviation from normal care as er the SVHM arthrolasty clinical athway, such as delayed discharge from hosital [12]. A data collection sreadsheet was designed to document otential risk factors for suerficial wound comlications. Risk factors were drawn from the current literature as well as novel, biologically lausible risk factors and included atient co-morbidities and factors surrounding oerative and ostoerative care. Information was extracted from the database and from careful medical chart review by a single researcher (KC). Information regarding ostoerative comlications was obtained rimarily from orthoaedic clinic notes, as well as emergency deartment or medical record entries if readmission occurred. All management strategies and decisions were not randomized and were based on the treating surgeon s reference at the time of surgery. There was no telehone or recall contact with atients for the uroses of this study. Statistical analysis Descritive statistics were used to summarize and reort the data. Descritive analyses were based on ercentages and frequencies for categorical variables and for continuous variables, mean and standard deviation (SD) or medians and interquartile range (IQR) if the data were skewed. Logistic regression was erformed to roduce odds ratios (ORs) with 95% confidence intervals (CIs) for the association between each variable and the resence or absence of suerficial wound comlication. Multivariable logistic regression techniques were used in the assessment of risk factors by adding in forward substitution factors identified as significant in the univariate analysis ( <0.1) or risk factors reviously identified in the ublished literature. Fisher s exact test was erformed to comare rates of suerficial wound comlication and rosthetic joint infection. All reorted -s were two-tailed and for each analysis < 0.05 was considered statistically significant. All analyses were erformed using Stata 11.2 (StataCor, College Station, TX, USA, 2009). Results Over the 18-month study eriod, 1006 atients underwent rosthetic hi or knee relacement surgery at SVHM. Forty-two atients were excluded from the study (eight with fractured neck of femur, 12 with setic revision arthrolasty and 22 who were lost to follow-u). Therefore, 964 atients were included in this current study (453 hi and 511 knee arthrolasties). The demograhic characteristics of the cohorts are outlined in Table 1. Clinical Microbiology and Infection ª2013 Euroean Society of Clinical Microbiology and Infectious Diseases, CMI, 20, 130 135
132 Clinical Microbiology and Infection, Volume 20 Number 2, February 2014 CMI TABLE 1. Demograhic characteristics of the hi and knee arthrolasty cohorts Hi cohort, n = 453 Knee cohort, n = 511 Median age, years (IQR) 69 (60, 75) 70 (64, 76) Median BMI, kg/m 2 (IQR) 29.7 (26.2, 33.7) 33.7 (29.6, 38.4) Female gender 272 (60%) 335 (66%) Rheumatoid arthritis 19 (4%) 39 (8%) Immunosuressant medications 10 (2%) 32 (6%) Systemic corticosteroids 13 (3%) 25 (5%) Diabetes mellitus 58 (13%) 118 (23%) Preoerative rescrition of warfarin 28 (6%) 47 (9%) American Society of Anaesthesiologists (ASA) score 1 15 (3%) 12 (2%) 2 25512 (2%) 249 (49%) 3 171 (38%) 233 (46%) 4 12 (3%) 17 (3%) Surgical antibiotic rohylaxis Cefazolin 437 (96%) 483 (96%) Vancomycin 12 (3%) 22 (4%) Gentamycin 345 (76%) 395 (77%) Image guided surgery (IGS) 94 (18%) Tourniquet 485 (95%) Median tourniquet time, minutes (IQR) 75 (60, 90) Median oeration time, minutes (IQR) 100 (85, 115) 95 (85, 115) Stales 324 (72%) 397 (81%) Subcuticular sutures 123 (28%) 94 (19%) Presence of drain tube 165 (36%) 262 (51%) Median drain outut in ml (IQR) 250 (140, 400) 380 (140, 700) Median transfusion, units (range) 0 (0, 8) 0 (0, 7) Surgical skin rearation 1% iodine in 70% alcohol 447 (99%) 501 (98%)12 0.5% chlorhexidine in 70% alcohol 6 (1%) 9 (2%) TABLE 2. Univariate and multivariate analysis of risk factors for suerficial wound comlications in the combined cohort Univariate analysis Multivariate analysis Age, years 1.02 (1.00, 1.05) 0.044 1.03 (1.00, 1.06) 0.018 Female gender 0.98 (0.62, 1.54) 0.9 Prosthetic hi Reference relacement Prosthetic knee 0.92 (0.59, 1.43) 0.7 relacement BMI, kg/m 2 1.06 (1.02, 1.09) 0.001 1.08 (1.05, 1.12) <0.001 Warfarin 2.04 (1.05, 3.94) 0.035 Rheumatoid arthritis 1.97 (0.93, 4.15) 0.077 2.56 (1.17, 5.58) 0.018 Immunosuressant 2.08 (0.89, 4.82) 0.089 medication Systemic 1.93 (0.78, 4.75) 0.2 corticosteroids Diabetes mellitus 1.36 (0.80, 2.30) 0.3 Surgical skin rearation 1% iodine in Reference 70% alcohol 0.5% chlorhexidine 3.74 (1.17, 12.0) 0.027 4.75 (1.42, 15.92) 0.012 in 70% alcohol Stales Reference Subcuticular sutures 0.50 (0.27, 0.95) 0.033 0.54 (0.29, 1.03) 0.063 Oeration time (min) 1.00 (0.99, 1.01) 0.8 Presence of drain tube 0.95 (0.61, 1.48) 0.8 Drain loss (ml) 0.99 (0.99, 1.00) 0.8 Blood transfusion (units of red blood cells) 1.24 (1.06, 1.44) 0.006 1.26 (1.06, 1.49) 0.008 Likelihood ratio = 39.90. Overall model erformance < 0.0001. Hi and knee cohorts were analysed as a combined cohort and then searately. Overall, 88 (9%) atients develoed a suerficial wound comlication (42 had suerficial incisional SSI, 40 had rolonged wound discharge and six had both). Combined cohort The combined cohort results of the univariate and multivariate logistic regression analysis are outlined in Table 2. On univariate analysis, the following factors were associated with the develoment of a suerficial wound comlication: increasing age, increasing body mass index (BMI), rheumatoid arthritis, warfarin, the use of 0.5% chlorhexidine in 70% alcohol for surgical skin rearation rior to surgical incision comared with 1% iodine in 70% alcohol, blood transfusion and skin closure with stales rather than sutures. On multivariate analysis, the following factors were indeendently associated with the develoment of suerficial wound comlications: increasing age, increasing BMI, rheumatoid arthritis, skin rearation with 0.5% chlorhexidine in 70% alcohol and increasing number of units of blood transfused in the ostoerative eriod. Hi cohort In the cohort of 453 atients who underwent elective hi arthrolasty, a wound comlication occurred in 43 atients at a rate of 9%. Readmission to hosital for management of the wound comlication was necessary in 11 of these cases (26%). In the univariate analysis of hi arthrolasty atients, the following factors were associated with suerficial wound comlication: increasing BMI, use of 0.5% chlorhexidine in 70% alcohol for surgical skin rearation, blood transfusion and warfarin theray. On multivariate analysis increasing BMI, skin rearation with 0.5% chlorhexidine in 70% alcohol and increasing blood transfusion requirements redicted suerficial wound comlications (Table 3). Knee cohort In the cohort of 511 knee arthrolasty atients, a wound comlication occurred in 45 atients at a rate of 9%. Readmission to hosital for management of the wound comlication was necessary in 15 of these cases (33%). The following factors were identified on univariate analysis: rheumatoid arthritis, diabetes mellitus and increasing tourniquet time. On multivariate analysis, rheumatoid arthritis and increasing tourniquet time redicted suerficial wound comlications (Table 4). Prosthetic joint infection Over the course of the study, 14 atients resented with rosthetic joint infection (seven rosthetic hi and seven rosthetic knee infections), with an overall infection rate of 1.45%. In rosthetic hi infections, six atients had receding suerficial wound comlications (Fisher s exact test < 0.001). Clinical Microbiology and Infection ª2013 Euroean Society of Clinical Microbiology and Infectious Diseases, CMI, 20, 130 135
CMI Carroll et al. Arthrolasty suerficial wound comlications 133 TABLE 3. Univariate and multivariate analysis of risk factors for suerficial wound comlications in the hi arthrolasty cohort Univariate analysis Multivariate analysis Age, years 1.02 (0.99, 1.06) 0.1 Female gender 1.26 (0.64, 2.49) 0.5 BMI 1.12 (1.06, 1.18) <0.001 1.13 (1.06 1.19) <0.001 Warfarin 3.96 (1.57, 10.00) 0.004 2.93 (0.99, 8.63) 0.050 Rheumatoid 1.31 (0.29, 5.89) 0.7 arthritis Immunosuressant 2.66 (0.55, 12.99) 0.2 medications Systemic 1.92 (0.41, 9.00) 0.4 corticosteroids Diabetes mellitus 0.74 (0.25, 2.16) 0.6 Surgical skin rearation 1% iodine in Reference 70% alcohol 0.5% chlorhexidine in 70% alcohol 11.08 (2.16, 56.86) 0.004 13.35 (2.11, 84.29) 0.006 Stales Reference Subcuticular 0.44 (0.18, 1.07) 0.070 sutures Oeration 1.00 (0.99, 1.01) 0.8 time (min) Presence of 1.85 (0.96, 3.55) 0.07 drain tube Drain loss (ml) 0.99 (0.99, 1.00) 0.7 Blood transfusion (units of red blood cells) 1.32 (1.09, 1.60) 0.005 1.37 (1.10, 1.70) 0.005 Likelihood ratio = 37.26. Overall model erformance < 0.0001. TABLE 4. Univariate and multivariate analysis of risk factors for suerficial wound comlications in the knee arthrolasty cohort Univariate analysis Multivariate analysis Age, years 1.02 (0.98, 1.05) 0.4 Female gender 0.85 (0.45, 1.61) 0.6 BMI 1.03 (0.98, 1.08) 0.2 Warfarin 1.26 (0.47, 3.37) 0.6 Rheumatoid arthritis 2.50 (1.03, 6.04) 0.042 2.75 (1.03, 7.33) 0.043 Immunosuressant 2.03 (0.74, 5.57) 0.2 medication Systemic corticosteroids 2.07 (0.68, 6.31) 0.2 Diabetes mellitus 1.57 (0.80, 3.07) 0.1 2.03 (0.99, 4.16) 0.054 Surgical skin rearation 1% iodine in 70% alcohol Reference 0.5% chlorhexidine 1.29 (0.16, 10.6) 0.8 in 70% alcohol Stales Reference Subcuticular sutures 0.64 (0.26, 1.57) 0.3 IGS 1.30 (0.62, 2.73) 0.5 Tourniquet 2.94 (0.33, 18.85) 0.6 Tourniquet time (min) 1.01 (1.00, 1.02) 0.029 1.01 (1.00, 1.02) 0.029 Oeration time (min) 1.00 (0.99, 1.01) 0.9 Presence of drain tube 0.60 (0.32, 1.13) 0.1 Drain loss (ml) 1.00 (0.99, 1.00) 0.5 Blood transfusion (units of red blood cells) Likelihood ratio = 10.99. Overall model erformance 0.012. 1.08 (0.82, 1.43) 0.6 In rosthetic knee infections, four atients had receding suerficial wound comlications (Fisher s exact test 0.006). Discussion Eidemiological studies have consistently imlicated suerficial wound comlications in the develoment of dee rosthetic joint infection [5,13]. Indeed, in this study 71% of atients subsequently diagnosed with rosthetic joint infection had receding suerficial wound comlications. We ostulate that identification and modification risk factors for suerficial wound comlications will lead to a decrease in the incidence of subsequent dee rosthetic joint infection. In addition, suerficial wound comlications themselves are associated with atient morbidity and cost to the healthcare system indeendent of the develoment of dee infection, such as rolonged hosital stay, readmission, ongoing treatments and reduced atient satisfaction [5,6,14,15]. In this study, 9% of atients develoed a suerficial wound comlication and of these, 30% required readmission to hosital for management. This study has identified a number of novel and clinically relevant risk factors for suerficial wound comlications. In addition, this study has highlighted the risk factors that differ according to arthrolasty site. The otimal agent for surgical skin rearation is a controversial issue. In a large, multicentre randomized clinical trial in clean-contaminated surgery, skin rearation with 2% chlorhexidine gluconate and 70% isoroyl alcohol was associated with a reduced number of suerficial and dee SSIs when comared with 10% ovidone-iodine [16]. This study did not include a third comarator arm with ovidone-iodine combined with alcohol; therefore it is difficult to attribute the reduction in SSIs to the chlorhexidine, the alcohol or to the combination of both agents [17]. At SVHM either chlorhexidine with alcohol or iodine with alcohol are recommended for skin antisesis as er the hosital infection control recommendations and the decision about which secific agent is used is based on the surgeon s reference. In this current study, surgical skin rearation with chlorhexidine 0.5% in alcohol 70% was associated with a five-fold increased risk of suerficial wound comlications comared with iodine 1% in alcohol 70%. The association was articularly marked in the hi arthrolasty cohort, with a 13-fold increased risk. This association may reflect differing anti-infective roerties of the agents. Counter to this, it may be argued that the difference observed reflects the surgeon s reference and surgical exerience. The agents chosen in this study differed from the randomized control trial; however, this study raises interesting questions regarding surgical rearation choice that requires further evaluation. Clinical Microbiology and Infection ª2013 Euroean Society of Clinical Microbiology and Infectious Diseases, CMI, 20, 130 135
134 Clinical Microbiology and Infection, Volume 20 Number 2, February 2014 CMI Obesity has been reviously imlicated in rosthetic joint infections, articularly in hi arthrolasty atients [9,18,19]. In addition, obesity is a risk factor for rolonged ostoerative wound drainage [20]. There are a number of otential exlanations for the association between increasing BMI and suerficial wound comlications, including the need for larger surgical incision, increased incidence of fat necrosis and rolonged or more comlicated arthrolasty surgery [9,20]. Rheumatoid arthritis leads to imaired immune function and revious studies have suggested interlay between the underlying disease rocess as well as use of immunosuressant medications [21,22]. In this study, the use of systemic corticosteroids or other immunosuressant medications was not associated with the develoment of suerficial wound comlications, suggesting the imortance of imaired immunity secondary to the underlying inflammatory rocess itself. The association between rheumatoid arthritis and suerficial wound comlications varied with the joint relaced. Rheumatoid arthritis was imlicated in knee but not hi arthrolasty. Patients with rheumatoid arthritis have an increased rate of carriage of Stahylococcus aureus and this organism is isolated in a higher roortion of rosthetic joint infections in atients with rheumatoid arthritis comared with other atients [21,23]. We ostulate that the association between rheumatoid arthritis and suerficial wound comlications may reresent interlay between increased Stahylococcus aureus carriage and the overall vulnerability of the rosthetic knee joint to infective comlications [21,24]. Blood transfusion has been reviously identified as a risk factor for wound infection in surgical atients, including those having orthoaedic surgery [25,26]. This association may reflect more rolonged or comlicated surgery with increased intraoerative blood loss, or develoment of haematoma. Haematoma formation imairs healing by increasing wound tension and reducing tissue erfusion, as well as acting as a culture medium for athogens [6,27]. Overall, this finding argues for strategies to minimize intraoerative blood loss, including attention to haemostasis and drainage of the surgical field. In this knee arthrolasty cohort, an increase in tourniquet time was associated with the develoment of suerficial wound comlications. This finding is in keeing with other ublished studies; increased tourniquet time has been identified as a risk factor for dee infection and for imaired wound healing and rolonged wound discharge after total knee arthrolasty [28]. The reason for this effect of increased tourniquet time may relate to a number of factors. Firstly, the rolonged tourniquet alication may lead to local inflammation and tissue hyoxia and subsequent comromised wound healing. In addition, a number of studies have imlicated tourniquet use in increased total ostoerative blood loss [29,30]. Finally, the use of the tourniquet reduces the tissue concentrations of rohylactic antibiotics, such as cehazolin, which may increase the risk of surgical site infections; however, in this current study, antibiotic rohylaxis was given rior to tourniquet inflation [31]. The benefit of subcuticular soluble sutures or stales remains a contentious issue, with a recent meta-analysis suggesting an increased rate of suerficial SSI when wounds were closed with stales comared with sutures [14]. In this study, wound closure with stales was associated with an increase in suerficial wound comlications on univariate analysis in the combined and hi arthrolasty cohorts, but this difference was not observed uon multivariate analysis. Therefore the question of otimal wound closure requires further investigation. Strengths of this study include an analysis of consecutively oerated atients over an 18-month eriod and a relatively large samle size. A single researcher was resonsible for all data collection, classification and coding, which romoted consistency in the analysis. In addition, hosital care is standardized for all arthrolasty atients at SVHM through the rotocol-driven clinical care athway. Limitations of the study are related to the retrosective study design and the ossible inaccuracy or misinterretation of the information contained in the medical records. However, we attemted to address this by setting clear definitions of wound comlication rior to data collection. Secondly, not all factors related to wound healing could be accounted for, such as nutrition, hygiene and wound care, articularly after atients were discharged home from hosital. Finally, we included data regarding rosthetic joint infection; however, given the contemoraneous setting of this study, 12- and 24-month follow-u data for some atients are incomlete, therefore some delayed and late infections may not be catured. Suerficial wound comlications, however, are a more tyical feature of early rosthetic joint infection rather than delayed or late infection (where ain is the redominant clinical feature) [3]. Conclusions This study has identified unique factors in the evolution of suerficial wound comlications. These data rovide clinicians with evidence to suort re-emtive strategies to identify atients at risk of suerficial wound comlications, articularly obese atients or atients with rheumatoid arthritis. This study has highlighted the imortance of erioerative factors, Clinical Microbiology and Infection ª2013 Euroean Society of Clinical Microbiology and Infectious Diseases, CMI, 20, 130 135
CMI Carroll et al. Arthrolasty suerficial wound comlications 135 including skin rearation, tourniquet time and blood transfusion, in the develoment of suerficial wound comlications. This study rovides an imetus for further clinical research, articularly assessing the imact of modification of these identified factors on the subsequent develoment of both suerficial wound comlications and subsequent rosthetic joint infections. Funding Dr Trisha Peel is suorted by a National Health and Medical Research Council Medical and Dental Postgraduate Research Scholarshi (APP1017038). Dr Michelle Dowsey is suorted by a National Health and Medical Research Council Early Career Australian Clinical Fellowshi (APP1035810). Transarency Declaration PFMC has received consultancy fee and funds for research (not related to the current work) from De Puy and funds for research from Allergan and royalties from Zimmer. All other authors: no conflict of interest to declare. References 1. Australian Orthoaedic Association. National bone and joint registry annual reort 2011. Adelaide 2011. 2. Kurtz S, Ong K, Lau E, Mowat F, Halern M. Projections of rimary and revision hi and knee arthrolasty in the United States from 2005 to 2030. J Bone Joint Surg Am 2007; 89: 780 785. 3. Zimmerli W, Tramuz A, Ochsner PE. Prosthetic-joint infections. N Engl J Med 2004; 351: 1645 1654. 4. Ridgeway S, Wilson J, Charlet A, Kafatos G, Pearson A, Coello R. Infection of the surgical site after arthrolasty of the hi. J Bone Joint Surg Br 2005; 87: 844 850. 5. Berbari EF, Hanssen AD, Duffy MC et al. Risk factors for rosthetic joint infection: case-control study. Clin Infect Dis 1998; 27: 1247 1254. 6. Saleh K, Olson M, Resig S et al. Predictors of wound infection in hi and knee joint relacement: results from a 20 year surveillance rogram. J Ortho Res 2002; 20: 506 515. 7. Dowsey MM, Kilgour ML, Santamaria NM, Choong PF. 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