Purpose: We study the relationship between surgical gestures and motion primitives in dry-lab surgical exercises towards a deeper understanding of surgical activity at fine-grained levels and interpretable feedback in skill assessment. Methods: We analyze the motion primitive sequences of gestures in the JIGSAWS dataset and identify inverse motion primitives in those sequences. Inverse motion primitives are defined as sequential actions on the same object by the same tool that effectively negate each other. We also examine the correlation between surgical skills (measured by GRS scores) and the number and total durations of inverse motion primitives in the dry-lab trials of Suturing, Needle Passing, and Knot Tying tasks. Results: We find that the sequence of motion primitives used to perform gestures can help detect labeling errors in surgical gestures. Inverse motion primitives are often used as recovery actions to correct the position or orientation of objects or may be indicative of other issues such as with depth perception. The number and total durations of inverse motion primitives in trials are also strongly correlated with lower GRS scores in the Suturing and Knot Tying tasks. Conclusion: The sequence and pattern of motion primitives could be used to provide interpretable feedback in surgical skill assessment. Combined with an action recognition model, the explainability of automated skill assessment can be improved by showing video clips of the inverse motion primitives of inefficient or problematic movements.

翻译：目的：我们研究干实验室手术练习中手术手势与运动基元之间的关系，旨在更深入地理解手术活动在细粒度层面的表现，并在技能评估中提供可解释的反馈。方法：我们分析了JIGSAWS数据集中手势的运动基元序列，并识别出这些序列中的反向运动基元。反向运动基元定义为同一工具对同一对象执行且效果上相互抵消的连续动作。我们还探讨了手术技能（通过GRS评分衡量）与缝合、穿针和打结任务干实验室试验中反向运动基元的数量及总时长之间的相关性。结果：我们发现，用于执行手势的运动基元序列有助于检测手术手势中的标注错误。反向运动基元常被用作恢复性动作，以纠正物体的位置或方向，或可能指示其他问题（如深度感知能力不足）。在缝合和打结任务中，试验中反向运动基元的数量及总时长与较低的GRS评分也呈现强相关性。结论：运动基元的序列和模式可用于在手术技能评估中提供可解释的反馈。结合动作识别模型，通过展示低效或问题运动对应的反向运动基元视频片段，可提升自动化技能评估的可解释性。