Magnification, Practice, and Anatomy of Movement: A Kinematic Study of Microsurgical

Microsurgery requires precise instrument manipulation at millimetre scale. Surgeons are trained to coordinate their hand movements under magnified visual feedback while minimising unwanted motion. Previous studies investigating pointing and tracing tasks found that accuracy improved from low to medium magnification, but plateaued at higher levels. However, it remains unclear whether this pattern extends to more complex tracing tasks and how performance varies across movement directions. We recruited 32 participants with varying levels of microsurgical expertise, and each participant performed an eight-branch star tracing task at randomized magnification levels, before and after a microsurgical anastomosis. We computed kinematic measures to characterise movement timing, extent, directional accuracy, residual tremor, and smoothness. Performance varied across branches, with differences observed in all metrics except for tremor intensity. Moreover, compared with the pre-anastomosis trial, participants traced faster, with lower normalised jerk but higher residual tremor intensity. Magnification affected only movement extent, which was smaller at the lower magnification level. Expertise groups differed in their patterns across branches and between trials, but no overall group difference was detected. These findings may contribute to a better understanding of the processes underlying microsurgical errors.