Development of a more robust tool for postural stability analysis of laparoscopic surgeons

Background: Physical difficulties experienced by surgeons performing minimally invasive surgery (MIS) are being given extensive attention by ergonomic researchers. Postural stability, not commonly addressed, is our prime focus. Center of pressure (COP) alone is used in the few existing postural stability studies. Using COP, we previously correlated postural stability to instrument type, task difficulty, and skill level. This study, including center of mass (COM), sway area analysis, and what we uniquely term postural stability demand (PSD), extends our investigation. Methods: Six surgeons from different experience levels were recruited to complete three fundamentals of laparoscopy (FLS^TM) tasks. Standing on two force plates, participants performed each task as a motion capture system recorded body movements. An ellipse was created for sway area analysis of COP, the point where the ground reaction force was located, and COM, the point at which body mass was concentrated. PSD was defined as the mean distance between the COP and COM locations in the anterior-posterior (A-P) or medial-lateral (M-L) directions. Postural parameters and performance time were correlated. Results: COM and COP sway areas positively correlated with pegboard transfer performance time (r = 0.928, p < 0.05; r = 0.864, p < 0.05) and also with circle-cutting performance time (r = 0.858, p < 0.05; r = 0.779, p = 0.06). However, COM and COP sway areas negatively correlated with endo-loop placement performance time (r = -0.925, p < 0.05; r = -0.935, p < 0.05). These results indicate unique postural controls based on skill level. During all tasks, PSD in the A-P direction strongly correlated with performance time (r = 0.829, p < 0.05; r = 0.913, p < 0.05; r = 0.880, p < 0.05), indicating that less-skilled participants experienced increased postural demands. Conclusions: This study demonstrated that variance in postural adjustments, as evidenced by sway area analysis, correlate to skill level and individual task. Strong correlation between PSD and performance time shows potential as a predictor of skill levels. Combining COM, COP, and PSD data produces a more robust analytic tool for identifying postural adjustments that can be correlated with skill level.