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MICRO: Microsurgical Index for Complication Risk and Outcomes
Thomas M Johnstone1,2, Daniel Najafali1,3, Priscila C Cevallos1,4
1Division of Plastic & Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Palo Alto, California.
Abstract:
Free tissue transfer (FTT) is determined by a multitude of patient and surgeon factors. However, no tool exists to quantify patient risk for complications following FTT. This study developed the microsurgical index for complication risk and outcomes (MICRO) to address this.Patients were queried from the 2007 to 2015 MarketScan Databases with CPT codes for FTT requiring microsurgical anastomosis. ICD-9 codes were used to query comorbidity and 90-day postoperative complication data for each patient. The Charlson and Elixhauser Comorbidity Indexes were constructed for each patient. The MICRO was then constructed with a forward stepwise selection from Elixhauser comorbidities and domain expert input. Indexes were used as covariates in multivariate logistic regression models with patient age, sex, and flap tissue type to predict complications following FTT. The area under the receiver operating characteristic curve and fivefold cross-validation classification accuracy was determined.A total of 5,595 patients were included. The final MICRO consists of seven variables (Charlson: 19; Elixhauser: 30). It had the highest area under the receiver operating characteristic curve (0.60) and accuracy (60.4%) of all indexes when predicting complications.The MICRO outperforms available patient comorbidity indexes at predicting complications following FTT with far fewer variables. Future studies could augment the MICRO with more granular or institutional data consisting of surgeon, donor-site, and recipient-site data to create a sharper risk-stratification tool for the plastic surgeon.
Insights
A new tool, the Microsurgical Index for Complication Risk and Outcomes (MICRO), predicts complications after free tissue transfer (FTT). This index offers a simpler, more accurate way to assess patient risk compared to existing methods.
Area of Science:
- Plastic Surgery
- Microsurgery
- Health Informatics
Background:
- Free tissue transfer (FTT) outcomes are influenced by numerous patient and surgeon factors.
- Currently, no validated tool exists to quantify patient-specific risks for complications following FTT procedures.
- Existing comorbidity indexes lack specificity for predicting FTT complications.
Purpose of the Study:
- To develop and validate a novel risk assessment tool, the Microsurgical Index for Complication Risk and Outcomes (MICRO), for predicting postoperative complications after FTT.
- To compare the predictive performance of the MICRO against established comorbidity indexes.
Main Methods:
- Retrospective analysis of 5,595 patients undergoing FTT with microsurgical anastomosis from the 2007-2015 MarketScan Databases.
- Development of the MICRO using forward stepwise selection from Elixhauser comorbidities, incorporating expert input.
- Multivariate logistic regression models utilizing patient demographics, comorbidities, and flap type to predict 90-day postoperative complications.
- Evaluation of predictive performance using Area Under the Receiver Operating Characteristic Curve (AUROCC) and cross-validation accuracy.
Main Results:
- The final MICRO comprises seven variables, outperforming existing comorbidity indexes.
- The MICRO achieved an AUROCC of 0.60 and a classification accuracy of 60.4% in predicting complications.
- The developed index demonstrated superior predictive capability with a reduced number of variables compared to Charlson and Elixhauser indexes.
Conclusions:
- The MICRO is a validated, concise tool that effectively predicts complications following free tissue transfer.
- It offers a significant improvement over existing comorbidity indexes for risk stratification in FTT patients.
- Future research should aim to enhance the MICRO by integrating surgeon and site-specific data for more precise risk assessment.
