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A Validated, Risk Assessment Model for Predicting Need for Salvage Flaps After Open Groin Vascular Procedures
John P. Fischer, MD, Eric Shang, MD, Jonas A. Nelson, MD, Emily Cleveland, BA, Edward Y. Woo, MD, Joseph M. Serletti, MD, Stephen J. Kovach, MD, Suhail Kanchwala, MD.
Hospital of the Univesity of Pennsylvania, Philadelphia, PA, USA.
Background: Groin wound complications after open vascular surgery procedures are common, morbid, and extremely costly. Salvage flaps can be effective for managing such wounds, but can also be associated with significant patient morbidty and added institution cost. Determining patients at risk for major wound complications can allow surgeons to make evidence-based, targeted interventions to reduce morbidity. We reviewed a large, consecutive series of open groin vascular procedures and salvage flaps to derive a validated risk assessment tool.
Methods: A retrospective review of consecutive patients undergoing groin cutdowns at the Hospital of the University of Pennsylvania for femoral access between 2006 and 2011 was performed. Patients who developed a wound complication requiring a muscle flap were compared to control patients. Exploratory univariate analyses were performed. Stepwise logistic regression was performed and validated using a bootstrap technique (coefficients were utilized to develop a simplified risk score). Discrimination and calibration of the logistic and simplified models were assessed.
Results: A total of 925 patients were included in the study. The salvage flap rate was 11.2% (N=104). Predictors of major wound complications and flap determined by logistic regression, included: prior groin surgery (OR=4.0, P<0.001), prosthetic graft (OR=2.7, P<0.001), CAD (OR=1.8, P=0.019), PAD (OR=5.0, P<0.001), and obesity (OR=1.7, P=0.039). The c-statistic for the regression demonstrated outstanding discrimination at 0.90 (Figure 1). The calibration of this model (Figure 2) was acceptable by the Hosmer-Lemeshow 2 statistic (8.65, P=0.373)
We then derived a simplified Salvage Risk Score (SRS) usable as a clinical decision tool generated by assigning numerical point values to significant predictors of groin salvage based on rounded ratios of logistic coefficients. The overall score is obtained by summation, and ranges from 0-10: prior surgery (3), PAD (3), prosthetic (2), CAD (1), and obesity (1) (Fig. 3). The simplified system preserved the ability to accurately predict groin salvage with excellent discrimation and a c-statistic of 0.84. Patients with low risk (SRS 0-2, n=387) had a rate of groin salvage of approximately 0.5%, whereas those at intermediate risk (SRS 3-6, n=407) had a 14.3% salvage rage, and patients at high risk (SRS 7-10, n=131) required groin salvage at a rate of 41.0%.
Conclusion: We present a simple, validated risk assessment tool that accurately predicts wound morbidity requiring flap salvage in open groin vascular surgery patients. This is the first study to date that provides a well-defined and validated risk assessment tool to manage the complicated groin wound. The preoperatively high-risk patient can be identified and selectively targeted as a candidate for a prophylactic muscle flap and risk counseling using these data.
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