The prevalence of total joint arthroplasty is increasing, with reports predicting a rise in both total hip arthroplasty (THA) and total knee arthroplasty (TKA) secondary to the aging population.1 Along with this increased volume, the number of prosthetic joint infections (PJIs) is expected to rise, with estimates as high as a 295% increase from 2010 to 2020.2 The clinical and economic implications have led many to evaluate methods to address the vexing problem of reducing PJI.
It is generally recognized that the cause of infection is influenced by factors both intrinsic and extrinsic to the patient. Recent literature has evaluated common extrinsic sources for PJI and identified circulating airborne microorganisms within the operating theater as a leading source of infection.3–6 Airborne particulate and bacterial colony-forming units (CFUs) have been demonstrated to be directly correlated with the number of personnel within the operating room (OR), traffic inside the OR as well as door traffic, and OR personnel skin exposure.3,7,8 Not only can bacterial CFUs be directly inoculated into surgical wounds during the case, but indirect inoculation can occur as airborne bacteria settle on surgical instruments on the back table and are later transferred into the wound.
A multitude of environmental controls have been implemented in operative theaters with the purpose of reducing airborne particulate and bacteria. These include helmet exhaust systems with hoods for the surgical team, vertical and horizontal laminar airflow of high-efficiency particulate air (HEPA)-filtered ultraclean air, perioperative ultraviolet radiation, and limiting OR room and door traffic.9–14 Although these tactics may reduce airborne CFUs, they all have limitations. It is well-known that large-scale laminar airflow systems are subject to upstream contamination if OR traffic interrupts the path of ultraclean air. Although ultraviolet radiation has the benefit of being bactericidal to bacteria that inoculate surgical wounds, concerns regarding personnel safety have limited its widespread use.12 Attempts to limit traffic in arthroplasty cases have included educating staff15 and storing implants and instruments inside the OR to reduce door traffic, although this is not always feasible.16,17
Although these methods focus on reducing particulate load within the operative suite, other technologies focus on removing particulate and bacterial CFUs from the air directly adjacent to the operative site. The Air Barrier System (ABS; Nimbic Systems, Stafford, Texas) is a device that applies ultraclean airflow across the operative incision. A nozzle attached in the surgical field at the end of the incision blows purified air across the incision during the case, thus redirecting particles away from the incision (Figure 1). The manufacturer claims that the system reduces airborne particulate over 10 µm in diameter from 10.43 to 2.39 particles per cubic meter. In a study evaluating the efficacy of the surgical airflow layer compared with controls, Stocks et al18 used a particle counter to demonstrate a 66% decrease in airborne particles at the operative site. This reduction included airborne bacterial contamination that could have otherwise been attributed to room contamination and, in the setting of large-scale laminar airflow, could introduce contamination. They concluded that the device was simple and inexpensive, did not prolong or impede surgical procedures, and was not subject to contamination of large ventilation systems. They did not correlate their results with infection rates because their promising study focused only on the particulate debris.
Directed airflow device at the surgical site of total hip arthroplasty
In a randomized, controlled trial, Darouiche et al16 evaluated the rate of deep infection when using the airflow layer in THA, instrumented spine procedures, and vascular bypass procedures. They noted that CFU density at the surgical incision was directly correlated with the incidence of deep implant infection. There were no cases of deep infection in the 148 procedures performed with the airflow layer, compared with a 2.7% infection rate in the 146 control cases. They concluded that the device was cost-effective and easily implemented and significantly reduced the rate of deep infection in these surgical procedures. Given the promise of potentially reducing the rate of infection in THA, the current authors implemented use of the surgical airflow layer in all primary THA procedures in 2013. The purpose of this study was to measure any change in PJI in primary THA cases.
Materials and Methods
This study received institutional review board approval. All clinical data, including complications and reoperations, are prospectively collected on all surgical patients in the authors' institutional research database. From July 30, 2013, to March 21, 2017, the surgical airflow system was used in 1093 primary THAs in 1028 patients. This cohort was compared with a control group of 1171 primary THAs from January 5, 2010, to June 26, 2013, in which the airflow system was not used. All cases were consecutively performed by a single surgeon (W.G.H.) via the anterior approach on a specialized table. Perioperative protocols aimed at reducing infection were consistent over the study protocol (methicillin-resistant Staphylococcus aureus screening, chlorhexidine shower preoperatively, dilute povidone-iodine wash after insertion of implants).
The authors performed a retrospective database review with a specific focus on wound dehiscence and deep infection. The groups did not differ significantly regarding age, sex, or body mass index (BMI). Forty-seven percent of cases in the airflow group and 43% of cases in the control group were male (P=.10). The mean BMI was not different between the airflow group (28.1 kg/m2) and the control group (28.4 kg/m2; P=.12). The mean age of patients in the airflow group was 64.7 years (range, 20–92 years), and the mean age in the control group was 62.6 years (range, 19–95 years; P=.11). All cases that returned to the OR for infection or wound revision within 4 months of surgery were identified. The method of treatment as well as the organisms were also identified. The Musculoskeletal Infection Society criteria were used to define PJI.19 Wound complication was defined as dehiscence and failure to heal requiring hospital re-admission, antibiotics, and debridement in the absence of deep infection or component revision. The rate of infection and wound revision was calculated for each group and compared with a Fisher's exact test. Comorbidities known to affect infection rates were recorded for each patient who experienced an infection.
A total of 7 deep PJIs in 6 patients developed in the airflow study group of 1093 THAs, for an infection rate of 0.64%. Bilateral infections occurred in 1 patient with bilateral hip replacements who underwent subsequent debridement and head and liner exchanges of both hips. Table 1 lists the comorbidities and cultured organisms that were identified in the infected cases. The most common comorbidity was obesity, with 5 of the 7 patients with PJIs having a BMI of more than 30 kg/m2. The average BMI of patients who encountered an infection (38.7 kg/m2) was significantly higher than those who did not (28.1 kg/m2; P<.001). Five of the patients were smokers or former smokers. Treatment for 6 of the 7 cases included irrigation and debridement, head and liner exchange, and antibiotics. In 1 case, a 2-stage exchange with an antibiotic spacer was performed.
Comorbidities and Organisms of Infected Cases
In the control group of 1171 cases, there were 7 PJIs, for an infection rate of 0.60%. There was no difference in the infection rate between the study and control groups (P=1.0). The comorbidities in the control group included 3 obese patients, 1 former smoker, and 2 patients with a history of cancer. Five of the 7 cases were treated with irrigation and debridement, head and liner exchange, and antibiotics, whereas 2 cases underwent a 2-stage revision with an antibiotic spacer. There was no difference in the rate of wound complications identified with 5 (0.46%) cases in the airflow group and 4 (0.34%) in the control group (P=.75). These all occurred within 4 months of surgery.
Infection following total joint arthroplasty is a devastating complication, with some researchers equating the morbidity and mortality to that of cancer.20 The medical community continues to explore techniques and technologies to reduce this complication. Experts have implicated airborne particles during the procedure as a major source of bacterial inoculation of the surgical wound, and several studies have been aimed at reducing airborne debris.18,21 Compelling bench data showed a reduction of airborne particle load, and the current authors therefore chose to use this device in their arthroplasty practice with the hope of reducing infection. With the numbers available, they could not demonstrate a reduction in the infection rate with use of the airflow device over several years and thousands of primary THA cases. Therefore, the cost-to-benefit ratio of the equipment did not justify its continued use in their institution.
This study had limitations. The most significant weakness was that the study was underpowered to conclude that there was no statistical difference between the 2 groups. The authors designed this study using the methodology from several recently published studies showing the utility of different perioperative techniques aimed at lowering the rate of PJI. Brown et al22 showed that by using a dilute povidone-iodine wash in 688 THA and TKA patients, the PJI rate was lowered to 0.15% compared with a prior infection rate of 0.97% in a cohort of 1862 cases where the wash was not used (P=.04). Another similar study design showed that by instituting a methicillin-resistant S aureus screening protocol the infection rate was lowered from 1.11% to 0.34% (P<.05).23 Jeans et al24 recently reported that screening for methicillin-sensitive S aureus in joint replacement patients reduced PJI in hips from 3% to 1.5% (P<.002) and from 1.92% to 1.41% overall (P=.03). Finally, Kapadia et al25 showed that instituting a preadmission chlorhexidine skin preparation lowered the PJI rate in TKA from 1.9% to 0.3% (P=.002). These study designs, cohort sizes, and scientific questions are comparable to those of the current study (Table 2). Because the baseline infection rate in these studies was above 1%, statistical significance was achieved. In the current study, with a relatively low starting infection rate of 0.6%, demonstrating a statistically significant reduction would require approximately 7000 cases in each group. Numbers of this magnitude would require either multicenter or registry data to demonstrate a significant result. Regardless, the authors think that studies that fail to achieve statistical significance can still add value to the body of literature on PJI, especially with a sample size of more than 2000 cases. The average practitioner may spend a career to accumulate a caseload of this size, and therefore find value in these data. Further study using a randomized design or larger numbers may provide better data on the influence of this device.
Studies of Interventions to Reduce Periprosthetic Joint Infections
Another weakness is that this study represents a retrospective comparative analysis of THA procedures performed during a multi-year period. Although the authors maintained a consistent commitment to infection control over the study duration, changes in clinical practice not measured in this study could have confounded the results. Factors such as surgical learning curve; staff turnover in the OR and sterile processing department; and evolution of how the team manages obesity, smoking, or diabetes mellitus can all influence rates of PJI. These weaknesses apply to all retrospective case-control studies. Unlike others of similar design, the authors were unable to demonstrate a reduction in their rate of PJI. Because the rate of infection was unchanged after instituting use of the device, it reinforced the complex nature of PJI and demonstrated that reducing airborne particles at the surgical site, although an attractive concept, cannot eliminate the occurrence of PJI. The authors postulate that it may be difficult to overcome intrinsic patient-related factors that may affect baseline infection rates in joint arthroplasty procedures.
Patient obesity and medical comorbidities correlate directly with infection following joint arthroplasty.26,27 Purcell et al28 evaluated obesity and surgical site infection following THA with the anterior approach and found that patients with a BMI above 35 kg/m2 had 7 times the risk of requiring revision for deep infection. Indeed, in the current study the infected cases in the airflow group had a mean BMI that was significantly higher than the uninfected cases. Other examples of comorbidities that affect the probability of infection are smoking and diabetes mellitus. Tischler et al29 showed that smokers have a significantly increased risk of infection within 90 days of a surgical procedure. Kurtz et al1 showed an increased risk of infection in diabetic joint replacement patients. In the current study, there were no attempts to separate cases based on demographic factors. Therefore, it is reasonable to assume the 2 arms of the current study have a similar distribution of medical comorbidities. The BMIs were not significantly different between the whole groups (P=.12). Intrinsic patient risk factors like these may have contributed a larger role to the rate of PJI than the airflow device.
It is widely accepted that airborne bacterial counts within the OR environment contribute to wound inoculation and subsequent PJI. Although the airflow layer provides ultraclean air directly over the surgical wound, it does not address the microbiological environment of the OR as a whole. Airborne bacteria within the OR can be deposited onto surgical instruments on the back table and secondarily inoculated into the surgical field. Operating room door openings and increased traffic creates turbulent air patterns, leading to increased dispersal of airborne microorganisms to the surgical field and creating the potential for wound inoculation and later sepsis despite the presence of an airflow layer.15,30–32 Given no appreciable differences in PJIs between the 2 groups in the current study, these environmental factors, in addition to intrinsic patient factors, may account for this observation despite the surgical airflow layer.
To the authors' knowledge, this study represents the largest volume of cases in the literature evaluating the efficacy of the surgical airflow layer in reducing surgical site infections in total joint arthroplasty. The authors observed no difference in the incidence of PJI with the implementation of the surgical site airflow system for direct anterior approach THA. The authors recognize a multifactorial etiology to PJI, including intrinsic patient, surgical, and environmental factors. They continue to recommend strict adherence to medical optimization of patients undergoing arthroplasty procedures, efficient surgery to minimize wound exposure, and careful attention to the OR environment to reduce the potential for PJI.
- Kurtz SM, Ong KL, Lau E, Bozic KJ, Berry D, Parvizi J. Prosthetic joint infection risk after TKA in the Medicare population. Clin Orthop Relat Res. 2010;468(1):52–56. doi:10.1007/s11999-009-1013-5 [CrossRef] PMID:19669386
- Kurtz SM, Ong KL, Lau E, Bozic KJ. Impact of the economic downturn on total joint replacement demand in the United States: updated projections to 2021. J Bone Joint Surg Am. 2014;96(8):624–630.
- Bitkover CY, Marcusson E, Ransjö U. Spread of coagulase-negative staphylococci during cardiac operations in a modern operating room. Ann Thorac Surg. 2000;69(4):1110–1115. doi:10.1016/S0003-4975(99)01432-0 [CrossRef] PMID:10800802
- Gruenberg MF, Campaner GL, Sola CA, Ortolan EG. Ultraclean air for prevention of postoperative infection after posterior spinal fusion with instrumentation: a comparison between surgeries performed with and without a vertical exponential filtered air-flow system. Spine. 2004;29(20):2330–2334. doi:10.1097/01.brs.0000142436.14735.53 [CrossRef] PMID:15480149
- Gosden PE, MacGowan AP, Bannister GC. Importance of air quality and related factors in the prevention of infection in orthopaedic implant surgery. J Hosp Infect. 1998;39(3):173–180. doi:10.1016/S0195-6701(98)90255-9 [CrossRef] PMID:9699136
- Noguchi C, Koseki H, Horiuchi H, et al. Factors contributing to airborne particle dispersal in the operating room. BMC Surg. 2017;17(1):78. doi:10.1186/s12893-017-0275-1 [CrossRef] PMID:28683726
- Quraishi ZA, Blais FX, Sottile WS, Adler LM. Movement of personnel and wound contamination. AORN J. 1983;38 (1):146–150. doi:10.1016/S0001-2092(07)69557-X [CrossRef]
- Ritter MA, Eitzen H, French ML, Hart JB. The operating room environment as affected by people and the surgical face mask. Clin Orthop Relat Res. 1975;111:147–150. doi:10.1097/00003086-197509000-00020 [CrossRef] PMID:1157412
- Lidwell OM, Lowbury EJ, Whyte W, Blowers R, Stanley SJ, Lowe D. Effect of ultraclean air in operating rooms on deep sepsis in the joint after total hip or knee replacement: a randomised study. Br Med J (Clin Res Ed). 1982;285(6334):10–14. doi:10.1136/bmj.285.6334.10 [CrossRef] PMID:6805791
- Rezapoor M, Parvizi J. Prevention of peri-prosthetic joint infection. J Arthroplasty. 2015;30(6):902–907. doi:10.1016/j.arth.2015.02.044 [CrossRef] PMID:25824026
- Ritter MA. Operating room environment. Clin Orthop Relat Res. 1999;369:103–109. doi:10.1097/00003086-199912000-00011 [CrossRef] PMID:10611865
- Ritter MA, Olberding EM, Malinzak RA. Ultraviolet lighting during orthopaedic surgery and the rate of infection. J Bone Joint Surg Am. 2007;89(9):1935–1940. doi:10.2106/00004623-200709000-00007 [CrossRef] PMID:17768189
- Panahi P, Stroh M, Casper DS, Parvizi J, Austin MS. Operating room traffic is a major concern during total joint arthroplasty. Clin Orthop Relat Res. 2012;470(10):2690–2694. doi:10.1007/s11999-012-2252-4 [CrossRef] PMID:22302655
- Stocks GW, Self SD, Thompson B, Adame XA, O'Connor DP. Predicting bacterial populations based on airborne particulates: a study performed in nonlaminar flow operating rooms during joint arthroplasty surgery. Am J Infect Control. 2010;38(3):199–204. doi:10.1016/j.ajic.2009.07.006 [CrossRef] PMID:19913327
- Hamilton WG, Balkam CB, Purcell RL, Parks NL, Holdsworth JE. Operating room traffic in total joint arthroplasty: identifying patterns and training the team to keep the door shut. Am J Infect Control. 2018;46(6):633–636. doi:10.1016/j.ajic.2017.12.019 [CrossRef] PMID:29455920
- Darouiche RO, Green DM, Harrington MA, et al. Association of airborne microorganisms in the operating room with implant infections: a randomized controlled trial. Infect Control Hosp Epidemiol. 2017;38(1):3–10.
- Alijanipour P, Karam J, Llinás A, et al. Operative environment. J Arthroplasty. 2014; 29(2)(suppl):49–64. doi:10.1016/j.arth.2013.09.031 [CrossRef] PMID:24342274
- Stocks GW, O'Connor DP, Self SD, Marcek GA, Thompson BL. Directed air flow to reduce airborne particulate and bacterial contamination in the surgical field during total hip arthroplasty. J Arthroplasty. 2011;26(5):771–776. doi:10.1016/j.arth.2010.07.001 [CrossRef] PMID:20851565
- Workgroup Convened by the Musculoskeletal Infection Society. New definition for periprosthetic joint infection. J Arthroplasty. 2011;26(8):1136–1138. doi:10.1016/j.arth.2011.09.026 [CrossRef] PMID:22075161
- Hotchkiss RS, Moldawer LL. Parallels between cancer and infectious disease. N Engl J Med. 2014;371(4):380–383. doi:10.1056/NEJMcibr1404664 [CrossRef]
- Lidwell OM, Lowbury EJ, Whyte W, Blowers R, Stanley SJ, Lowe D. Airborne contamination of wounds in joint replacement operations: the relationship to sepsis rates. J Hosp Infect. 1983;4(2):111–131. doi:10.1016/0195-6701(83)90041-5 [CrossRef] PMID:6195220
- Brown NM, Cipriano CA, Moric M, Sporer SM, Della Valle CJ. Dilute betadine lavage before closure for the prevention of acute postoperative deep periprosthetic joint infection. J Arthroplasty. 2012;27(1):27–30. doi:10.1016/j.arth.2011.03.034 [CrossRef] PMID:21550765
- Sporer SM, Rogers T, Abella L. Methicillin-resistant and methicillin-sensitive Staphylococcus aureus screening and de-colonization to reduce surgical site infection in elective total joint arthroplasty. J Arthroplasty. 2016;31(9)(suppl):144–147. doi:10.1016/j.arth.2016.05.019 [CrossRef] PMID:27387479
- Jeans ME, Holleyman MR, Tate DD, Reed MM, Malviya MA. Methicillin sensitive Staphylococcus aureus screening and decolonisation in elective hip and knee arthroplasty. J Infect. 2018;77(5):405–409. doi:10.1016/j.jinf.2018.05.012 [CrossRef]
- Kapadia BH, Zhou PL, Jauregui JJ, Mont MA. Does preadmission cutaneous chlorhexidine preparation reduce surgical site infections after total knee arthroplasty?Clin Orthop Relat Res. 2016;474(7):1592–1598. doi:10.1007/s11999-016-4767-6 [CrossRef] PMID:26956247
- Belmont PJ Jr, Goodman GP, Hamilton W, Waterman BR, Bader JO, Schoenfeld AJ. Morbidity and mortality in the thirty-day period following total hip arthroplasty: risk factors and incidence. J Arthroplasty. 2014;29(10):2025–2030. doi:10.1016/j.arth.2014.05.015 [CrossRef] PMID:24973000
- Murgatroyd SE, Frampton CM, Wright MS. The effect of body mass index on outcome in total hip arthroplasty: early analysis from the New Zealand Joint Registry. J Arthroplasty. 2014;29(10):1884–1888. doi:10.1016/j.arth.2014.05.024 [CrossRef] PMID:25042579
- Purcell RL, Parks NL, Gargiulo JM, Hamilton WG. Severely obese patients have a higher risk of infection after direct anterior approach total hip arthroplasty. J Arthroplasty. 2016;31(9)(suppl):162–165. doi:10.1016/j.arth.2016.03.037 [CrossRef] PMID:27133929
- Tischler EH, Matsen Ko L, Chen AF, Maltenfort MG, Schroeder J, Austin MS. Smoking increases the rate of reoperation for infection within 90 days after primary total joint arthroplasty. J Bone Joint Surg Am. 2017;99(4):295–304. doi:10.2106/JBJS.16.00311 [CrossRef] PMID:28196031
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- Lynch RJ, Englesbe MJ, Sturm L, et al. Measurement of foot traffic in the operating room: implications for infection control. Am J Med Qual. 2009;24(1):45–52.
- Smith EB, Raphael IJ, Maltenfort MG, Honsawek S, Dolan K, Younkins EA. The effect of laminar air flow and door openings on operating room contamination. J Arthroplasty. 2013;28(9):1482–1485. doi:10.1016/j.arth.2013.06.012 [CrossRef] PMID:23890828
Comorbidities and Organisms of Infected Cases
|A1||Morbid obesity (BMI >50 kg/m2), diabetes mellitus, sleep apnea, coronary artery disease, history of cellulitis, former smoker||Proteus mirabilis, coagulase-negative staphylococci, Enterococcus faecalis, Staphylococcus capitis, Corynebacterium matruchotii|
|A2||Obesity (BMI >40 kg/m2), pre–diabetes mellitus, asthma||Gram-positive cocci, Staphylococcus aureus, Staphylococcus lugdunensis|
|A3||Morbid obesity (BMI >50 kg/m2), atrial fibrillation||Staphylococcus intermedius|
|A4||Smoker for 30 years, obesity (BMI 33 kg/m2)||Staphylococcus hominis|
|A5||Former smoker, 2 drinks per day||Streptococcus agalactiae (group B Streptococcus)|
|A6||Former smoker, 2 drinks per day||Streptococcus agalactiae (group B Streptococcus)|
|A7||Obesity (BMI 39 kg/m2), coronary artery disease, diabetes mellitus, former smoker||Staphylococcus aureus, diphtheroids|
|C1||Obesity (BMI >40 kg/m2), sleep apnea, hypertension||Citrobacter koseri|
|C2||Psoriasis, former smoker||Group C Streptococcus|
|C3||Obesity (BMI 39 kg/m2), steroid use, multiple sclerosis||Enterobacter cloacae|
|C4||History of cancer (lymphoma), chemotherapy, polyneuropathy||Enterobacter cloacae|
|C5||None||Rare yeast, group B Streptococcus|
|C6||Rheumatoid arthritis, cancer||Streptococcus agalactiae|
|C7||Cancer, obesity (BMI 32 kg/m2)||Pasteurella multocida|
Studies of Interventions to Reduce Periprosthetic Joint Infections
|Study (Year)||Intervention||No.||Control Infection Rate||Postintervention Infection Rate|
|Brown et al22 (2012)||Dilute povidone-iodine wash||2550||0.97%||0.15%|
|Sporer et al23 (2016)||MRSA screening||9690||1.11%||0.34%|
|Jeans et al24 (2018)||MSSA screening||5917||3.00%||1.50%|
|Kapadia et al25 (2016)||Chlorhexidine skin preparation||3717||1.90%||0.30%|
|Current||Directed airflow layer||2264||0.60%||0.64%|