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J Reconstr Microsurg
DOI: 10.1055/a-2576-0299
Original Article

MICRO: Microsurgical Index for Complication Risk and Outcomes

Thomas M. Johnstone‡   *
1   Division of Plastic & Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Palo Alto, California
2   Stanford University School of Medicine, Stanford, California
,
Daniel Najafali  ‡   *
1   Division of Plastic & Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Palo Alto, California
3   Carle Illinois College of Medicine, University of Illinois Urbana-Champaign, Urbana, Illinois
,
Priscila C. Cevallos
1   Division of Plastic & Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Palo Alto, California
4   Geisel School of Medicine, Dartmouth University, Hanover, New Hampshire
,
Augustine Kang
1   Division of Plastic & Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Palo Alto, California
2   Stanford University School of Medicine, Stanford, California
,
Clifford C. Sheckter
1   Division of Plastic & Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Palo Alto, California
,
Rahim S. Nazerali
1   Division of Plastic & Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Palo Alto, California
,
Gordon K. Lee
5   Department of Plastic Surgery, University of California-Irvine, Orange, California
› Author Affiliations
Funding This work was supported by the Stanford Center for Population Health Sciences Data Core (UL1TR003142).
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Abstract

Background

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.

Methods

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.

Results

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.

Conclusion

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.

Keywords

complications - free flap - microsurgical - outcomes - risk index

Authors' Contributions

Conceptualization and methodology: T.M.J., D.N., P.C.C., C.C.S., R.S.N., and G.K.L.


Data curation and formal analysis: T.M.J.


Investigation, writing—original draft and review and editing: T.M.J., D.N., P.C.C., A.K., C.C.S., R.S.N., and G.K.L.


Supervision and project administration: C.C.S., R.S.N., and G.K.L.


All authors read and approved the final version.


Presented at

This work was presented at the Oral presentation at the 101st Annual Meeting of the American Association of Plastic Surgeons (Chicago, IL; April 2023) and Oral presentation at the 73rd Annual Meeting of the California Society of Plastic Surgeons (San Francisco, CA; May 2023).


* Indicates Co-First Authors, equal contribution.


Supplementary Material



Publication History

Received: 23 November 2024

Accepted: 31 March 2025

Accepted Manuscript online:
07 April 2025

Article published online:
28 April 2025

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