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Risk Factors Associated with Deep Surgical Site Infections After Primary Total Knee ArthroplastyAn Analysis of 56,216 Knees
Robert S. Namba, MD1; Maria C.S. Inacio, MS2; Elizabeth W. Paxton, MA2
1 Department of Orthopedic Surgery, Kaiser Permanente Orange County, Southern California Permanente Medical Group, 6670 Alton Parkway, Irvine, CA 92618
2 Department of Surgical Outcomes and Analysis, Kaiser Permanente, 8954 Rio San Diego Drive, Suite 406, San Diego, CA 92108. E-mail address for M.C.S. Inacio: maria.cs.inacio@kp.org
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Investigation performed at the Department of Surgical Outcomes and Analysis, Kaiser Permanente, San Diego, California

A commentary by Donald W. Roberts, MD, is linked to the online version of this article at jbjs.org.

Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. None of the authors, or their institution(s), have had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, no author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article

Copyright © 2013 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2013 May 01;95(9):775-782. doi: 10.2106/JBJS.L.00211
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Deep surgical site infection following total knee arthroplasty is a devastating complication. Patient and surgical risk factors for this complication have not been thoroughly examined. The purpose of this study was to evaluate risk factors associated with deep surgical site infection following total knee arthroplasty in a large U.S. integrated health-care system.


A retrospective review of a prospectively followed cohort of primary total knee arthroplasties recorded in a total joint replacement registry from 2001 to 2009 was conducted. Records were screened for deep surgical site infection with use of a validated algorithm, and the results were adjudicated by chart review. Patient factors, surgical factors, and surgeon and hospital characteristics were identified with use of the total joint replacement registry. Cox regression models were used to assess risk factors associated with deep surgical site infection.


A total of 56,216 total knee arthroplasties were identified; 63.0% were done in women, the average age of the patients was 67.4 years (standard deviation [SD] = 9.6), and the average body mass index (BMI) was 32 kg/m2 (SD = 6). The incidence of deep surgical site infection was 0.72% (404/56,216). In a fully adjusted model, patient factors associated with deep surgical site infection included a BMI of ≥35 (hazard ratio [HR] = 1.47), diabetes mellitus (HR = 1.28), male sex (HR = 1.89), an American Society of Anesthesiologists (ASA) score of ≥3 (HR = 1.65), a diagnosis of osteonecrosis (HR = 3.65), and a diagnosis of posttraumatic arthritis (HR = 3.23). Hispanic race was protective (HR = 0.69). Protective surgical factors included use of antibiotic irrigation (HR = 0.67), a bilateral procedure (HR = 0.51), and a lower annual hospital volume (HR = 0.33). Surgical risk factors included quadriceps-release exposure (HR = 4.76) and the use of antibiotic-laden cement (HR = 1.53). In a subanalysis, operative time was a risk factor, with a 9% increased risk per fifteen-minute increment.


Use of a comprehensive infection surveillance system, combined with a total joint replacement registry, identified patient and surgical factors associated with infection following total knee arthroplasty in a large sample. High-risk patients should be counseled, and modifiable clinical conditions should be optimized. Use of antibiotic irrigation should be encouraged, but antibiotic-laden cement may not be useful.

Level of Evidence: 

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Annette L. Adams, Robert S. Namba, Elizabeth W. Paxton, Maria C.S. Inacio
    Posted on July 08, 2013
    Response to Comments
    Kaiser Permanente, Irvine and San Diego, California, USA

    While the two studies appear similar, and have almost identical estimations, they actually address quite different research questions, and include important methodological differences (study sample, exposure ascertainment, confounding adjustments, analyses performed). The first study (Adams et al.) investigated diabetes impact on several surgical outcomes and the second study (Namba et al.) evaluated multiple risk factors for deep surgical site infection.

    Adams et al. used the Kaiser Permanente Total Joint Replacement Registry (KPTJJR) to identify 40,491 total knee arthroplasty patients from 5 regions. The primary aim was to assess the association between glycemic control status (well- and poorly-controlled diabetes vs. no diabetes) and several surgical and medical outcomes. This study classified patients as having diabetes (vs. no diabetes) using a combination of ICD-9 diagnosis codes and laboratory-based information within 2 years of the time of the arthroplasty procedure. Another main difference between these studies are the confounding adjustments performed (a modified Deyo index score was used). While the association between diabetes status (diabetes yes vs. no) and deep infection was not explicitly done in the study by Adams et al., after doing so a similar estimate to the second study by Namba et al. (OR=1.26, 95% CI 0.97-1.68) was obtained.

    In the second study (Namba et al.) of 56,216 patients registered in the KPTJRR general infection risk factors for deep infection were the target of the investigation. In this study, all patients registered in the KPTJRR were included (all regions), diabetes was identified using the Diabetes Registries of each KP region (no time limit in their diagnosis was stipulated), and a broader number of covariates were investigated. The study focused on identifying general risk factors of infection and found diabetes to be risk factor for deep infection (HR=1.28, 95%CI 1.03-1.60).

    Todd Clevenger, MD
    Posted on June 26, 2013
    Same data base, different conclusion?
    Southern Oregon Orthopedics, Medford, OR, USA

    After reading and comparing this article to one also published by Dr. Namba and colleagues in JBJS in March of this year (Surgical Outcomes of Total Knee Replacement According to Diabetes Status and Glycemic Control, 2001 to 2009), presumably mining the same database, I was a bit perplexed on the association of diabetes with infection in this article and the lack of association in the article published in March. I was wondering if Dr. Namba or the JBJS editors might be able to clarify any methodological differences in the two papers that might have led to the discrepancy, and also comment on whether or not they feel that the Kaiser joint database supports or does not support an association between diabetes and infection in total knee arthroplasty. Thank you very much.

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