Ergonomic assessment of optimum operating table height for hand-assisted laparoscopic surgery

To investigate the influence of the working surface height on task performance and muscle workload in hand-assisted laparoscopic surgery. The standard task used was closure of 5-cm enterotomy inside a hand-assisted laparoscopic surgery trainer. Surgeons were instructed to place the sutures 3-5 mm apart and from the enterotomy edge. Ten surgeons participated in each experiment and one task was performed with each level. The first experiment compared the quality of task performance and muscle workload with the working surface at: elbow level, 10 cm above, 15 cm above and 10 cm below the elbow. Further narrower levels (5 cm below, at the elbow and 5 cm above the elbow) were investigated in the second experiment. Outcome measures were execution time (s), placement error score (mm), leakage pressure (mmHg), number of execution errors, muscle workload as measured by integrated electromyography (mV center dot s) and visual analogue score of back discomfort (mm). The first experiment showed that 15 cm above the elbow level was associated with the longest execution time and similar quality of task performance. This level resulted in a higher workload of the deltoid of the extracorporeal limb, the arm extensor of the intracorporeal side and the trapezius and paraspinal muscles of both intra- and extracorporeal limbs. Also, the 10 cm above the elbow level was associated with increased muscle workload of the deltoid of extracorporeal limb and the trapezius of both limbs compared with the elbow height. The 10 cm below the elbow level was associated with increased back discomfort. The second experiment showed that 5 cm below the elbow height was associated with increased muscle workload of the arm flexor group of the intracorporeal dominant limb. The optimum table height for hand-assisted laparoscopic surgery allows the working surface of the extracorporal instrument handle to be at or 5 cm above the elbow level.