Introduction: Joint angle analysis using variables calculated from task beginning to end is the primary means in surgical ergonomics for understanding joint control. These traditional variables, e.g. range of motion, provide general joint movement information; however, they cannot differentiate specific patterns required to achieve certain goals of laparoscopic tasks. We propose a novel method of data analysis that extends our previous DDW 2006 findings about characteristic joint kinematics determined from mean joint angle. Here we divide a laparoscopic task into functional subtasks and analyze joint movement within the subtask's time frame to extract characteristic movement patterns associated with particular surgical maneuvers.
Methods: Nine right-handed, experienced laparoscopic surgeons were recruited to perform the standard FLS pegboard transfer task. A motion analysis system captured participants’ upper body movements while simultaneously recording endoscopic images that allowed task performance to be partitioned. For each subject, left- and right-side data were captured in three rotations—flexion/extension, abduction/adduction, and internal/external—at three joints—shoulder, elbow, and wrist. The transfer of a single disk was divided into four subtasks: pickup, medial transfer (side to middle), lateral transfer (middle to side before dropping), and the actual drop. Joint angles were analyzed within the time windows of each subtask. Data from a representing subject suggests a possible rubric.
Results: Each subtask was composed of a unique set of joint kinematics (see table). These joint controls were relatively consistent through six repetitions. While left-right comparison in three subtasks showed no significant control strategy difference, during the pickup subtask left side movement involved fewer joints, well known as joint freeze on the non-dominant side.
Conclusions: Our study showed that detailed characteristic movement patterns, not fully depictive with traditional analysis, can be extracted when a laparoscopic task is partitioned into functional subtasks. This new approach will enable our investigation of intra- and inter-subject variability of joint kinematics as part of the development of standard joint control strategy matrices for optimal surgical performance.
Significant joint movements during each subtask

Subtask	Sides	Shoulder	Elbow	Wrist
Pickup	Left	extended	—	extended & radial deviation
	Right	extended	extended	extended, radial deviation & supinated
Medial transfer	Both	flexed, abducted & externally rotated	extended	flexed, radial deviation & supinated
Lateral transfer	Both	extended & adducted	flexed	extended & ulnar deviation
Drop	Both	flexed	—	flexed & ulnar deviation