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SELECTED PROCEEDINGS FROM THE 2019 MUSCULOSKELETAL INFECTION SOCIETY MEETING (GUEST EDITOR CHARALAMPOS G. ZALAVRAS MD, PHD)

CORR Insights®: Risk Factors for Surgical Site Infection after Operative Fixation of Acetabular Fractures: Is Psoas Density a Useful Metric?

Cornell, Charles N. MD

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Clinical Orthopaedics and Related Research: August 2020 - Volume 478 - Issue 8 - p 1768-1769
doi: 10.1097/CORR.0000000000001300

Where Are We Now?

Cichos and colleagues [5] performed a retrospective study of patients with acetabular fractures who underwent open reduction internal fixation (ORIF) to determine whether psoas muscle density could be used as a predictor for risk of surgical site infection (SSI). As the paradigm of quality-based health care is adopted throughout orthopaedic surgery, more effort is being directed at providing tools for surgical risk assessment. Frailty is a clinically recognizable state of increased vulnerability resulting from aging-associated decline in reserve and function across multiple physiologic systems that may encompass factors such as advancing age, particular comorbidity profiles, undernutrition, and sarcopenia [6]. Low serum albumin is an often-cited risk factor that is associated with an increased risk of wound healing complications and infection as well as higher mortality following a variety of orthopaedic scenarios including surgical care of patients with hip fractures and those undergoing elective total joint replacement [2-4, 6, 7].

Cichos and colleagues [5] focus on psoas muscle density because it can be measured from preoperative CT scans used to diagnose and characterize acetabular fractures needing ORIF. As documented by the authors, psoas muscle density can be a surrogate for overall muscle quality as well as a tool that may help diagnose undernutrition and quantify sarcopenia. It has been recognized as a potential prognostic variable relevant to critically ill patients following general surgical procedures [8, 9].

Although several variables that were associated with SSI were identified including female sex and longer surgical times with more extensive blood loss, the authors were unable to provide any association between psoas density and the risk of SSI in these patients. As such, this clinical characteristic does not appear to provide any prognostic insight when preparing acetabular fractures patients for surgical repair.

Where Do We Need to Go?

Ideally, the effort to detect risk factors for SSI and medical complications following surgery should focus on those that are modifiable. The authors suggest that sarcopenia likely reflects chronic undernutrition, and as such may be a modifiable risk factor. Although logical, the potential for nutritional correction and supplementation to reverse the detrimental association of preoperative nutritional status with poor surgical outcome has yet to be realized. This is most frustratingly apparent when treating older patients with hip fractures [1, 10]. For a long time now, surgeons have observed that low serum albumin and other variables (like sarcopenia) that are believed to reflect nutritional status are associated with infection, but these “nutritional” factors may not themselves be causing the infections we observe. Low albumin and sarcopenia may instead reflect a chronic state of ill health or frailty and not merely malnutrition; that being so, nutritional supplementation alone may not mitigate the risk associated with what surgeons sometimes surmise is a problem related to “malnutrition”. In fact, decades of research suggest this is so [1, 10]. It does appear that nutritional support and supplementation have value, but the intervention must be started well before surgery is performed [4]. We need a more in-depth understanding of the relationship between measures reflective of nutritional status and the perhaps more multifaceted clinical condition of frailty, as well as the variety of other comorbidities that are associated with increased surgical risk [7].

Additionally, the relationship between increased surgical risk and pre-existing comorbidities needs to be better defined. Efforts to describe frailty based on baseline health characteristics are rudimentary and the studies investigating these relationships have been low evidence [1, 7, 10]. For example, why is hypoalbuminemia a recognized risk factor? Is it directly the result of protein-calorie malnutrition, does it reflect liver dysfunction, dilution from chronic hypervolemia, or other some physiologic dysfunction yet described that specifically increases surgical risk?

How Do We Get There?

In order to investigate preoperative interventions to mitigate frailty or undernutrition, only elective surgical procedures should be studied. Preoperative interventions are not practical for patients requiring urgent, life- or limb-saving surgery.

Primary total joint arthroplasty has providedva useful experience [2, 3, 6, 7], but studies involving surgeries like revision joint replacement or complex spinal reconstruction may be necessary to detect meaningful results. It may take surgeries of sufficient complexity and risk to provide the setting where frailty-related complications (infection, medical complications, loss of strength or mobility) occur with sufficient frequency that it’s possible to power studies adequately to detect clinically important differences between interventions. Every effort should be made to design studies of higher evidence in contrast to the retrospective, observational efforts reported to date. Meaningful clinical differences of the variables assessed need to be defined. Both short- and long-term outcomes should also be studied. SSI is a critical endpoint, but other, longer-term endpoints like recovery of cognition, functional strength, and mobility should be studied as well. This will require large, multicenter prospective studies that collect data related to nutrition, frailty and relevant patient-reported outcomes. If registries are to become a source for this important research this type of data will need to be input for each patient captured.

It is unlikely that a single, dominant comorbidity will be identified. It is more likely to be a combination of factors producing identifiable profiles of risk. To assess the several potential risk factors, large study populations will be needed.

References

1. Avenell A, Smith TO, Curtain JP, Mak JC, Myint PK. Nutritional supplementation for hip fracture aftercare in older people. Cochrane Database Syst Rev. 2016;11:CD001880.
2. Bohl DD, Shen MR, Kayupov E, Della Valle CJ. Hypoalbuminemia independently predicts surgical site infection, pneumonia, length of stay, and readmission after total joint arthroplasty. J Arthroplasty. 2016;31:15-21.
3. Bohl DD, Shen MR, Hannon CP, Fillingham YA, Darrith B, Della Valle CJ. Serum albumin predicts survival and postoperative course following surgery for geriatric hip fracture. J Bone Joint Surg Am. 2017;99:2110-2118.
4. Burgess LC, Phillips SM, Wainwright TW. What is the role of nutritional supplements in support of total hip replacement and total knee replacement surgeries? A systematic review. Nutrients. 2018;10:E820.
5. Cichos KH, Mahmoud KH, Spitler CA, Abdel Aal AMK, Osman S, McGwin G Jr, Ghanem ES. Risk factors for surgical site infection after operative fixation of acetabular fractures: is psoas density a useful metric? Clin Orthop Relat Res. [Published online ahead of print March 10, 2020]. DOI: 10.1097/CORR.0000000000001207.
6. Fu MC, McLawhorn AS, Padgett DE, Cross MB. Hypoalbuminemia is a better predictor than obesity of complications after total knee arthroplasty: A propensity score-adjusted observational analysis. HSS J. 2017;13:66-74.
7. Schmucker AM, Hupert N, Mandl LA. The impact of frailty on short-term outcomes after elective hip and knee arthroplasty in older adults: A systematic review. Geriatr Orthop Surg Rehabil. 2019;10:2151459319835109.
8. Simonsen C, de Heer P, Bjerre ED, Suetta C, Hojman P, Pedersen BK, Svendsen LB, Christensen JF. Sarcopenia and postoperative complication risk in gastrointestinal surgical oncology: A meta-analysis. Ann Surg. 2018;268:58-69.
9. Yeh DD, Ortiz-Reyes LA, Quraishi SA, Chokengarmwong N, Avery L, Kaafarani HMA, Lee J, Fagenholz P, Chang Y, DeMoya M, Velmahos G. Early nutritional inadequacy is associated with psoas muscle deterioration and worse clinical outcomes in critically ill surgical patients. J Crit Care. 2018;45:7-13.
10. Zeraatkar D, Petrisor B. Cochrane in CORR®: Nutritional supplementation for hip fracture aftercare in older people. Clin Orthop Relat Res. 2019;477:491–493.
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