Use of a Machine Learning Algorithm to Classify Expertise: Analysis of Hand Motion Patterns During a Simulated Surgical Task

Watson, Robert A. MBChB, FRCS(Eng)

Academic Medicine:
doi: 10.1097/ACM.0000000000000316
Research Reports

Purpose: To test the hypothesis that machine learning algorithms increase the predictive power to classify surgical expertise using surgeons’ hand motion patterns.

Method: In 2012 at the University of North Carolina at Chapel Hill, 14 surgical attendings and 10 first- and second-year surgical residents each performed two bench model venous anastomoses. During the simulated tasks, the participants wore an inertial measurement unit on the dorsum of their dominant (right) hand to capture their hand motion patterns. The pattern from each bench model task performed was preprocessed into a symbolic time series and labeled as expert (attending) or novice (resident). The labeled hand motion patterns were processed and used to train a Support Vector Machine (SVM) classification algorithm. The trained algorithm was then tested for discriminative/predictive power against unlabeled (blinded) hand motion patterns from tasks not used in the training. The Lempel–Ziv (LZ) complexity metric was also measured from each hand motion pattern, with an optimal threshold calculated to separately classify the patterns.

Results: The LZ metric classified unlabeled (blinded) hand motion patterns into expert and novice groups with an accuracy of 70% (sensitivity 64%, specificity 80%). The SVM algorithm had an accuracy of 83% (sensitivity 86%, specificity 80%).

Conclusions: The results confirmed the hypothesis. The SVM algorithm increased the predictive power to classify blinded surgical hand motion patterns into expert versus novice groups. With further development, the system used in this study could become a viable tool for low-cost, objective assessment of procedural proficiency in a competency-based curriculum.

Author Information

Dr. Watson is assistant professor, Department of Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.

Funding/Support: This study was supported by a University of North Carolina at Chapel Hill Academy of Educators award.

Other disclosures: None reported.

Ethical approval: The University of North Carolina Medical Center institutional review board approved all procedures.

Correspondence should be addressed to Dr. Watson, 4026 Burnett-Womack Building, Campus Box 7211, Chapel Hill, NC 27599-7211; telephone: (919) 966-8008; e-mail:

© 2014 by the Association of American Medical Colleges