Ideal manipulation angle and instrument length in hand-assisted laparoscopic surgery

Background This study aimed to investigate the impact of manipulation angles and instrument length on task performance and muscle workload in hand-assisted laparoscopic surgery. Methods The standard task was to close a 5-cm enterotomy of porcine small bowel inside a hand-assisted laparoscopic trainer. Surgeons were instructed to place the sutures 3 to 5 mm apart and from the enterotomy edge. Ten surgeons participated in each experiment. In the first experiment, each surgeon performed one task for each of the following manipulation angles: 45°, 60°, 75°, and 90°. In the second experiment, each surgeon performed two sessions of three tasks using either standard-length (330 mm) or short (250 mm) needle holders in the external hand. Outcome measures were execution time (s), placement error score (mm deviation from exact placement), leaking pressure (mmHg), and muscle workload by upper extremities as measured by integrated electromyography (mV s). Results In the first experiments, the mean execution time was significantly longer with 90° angles than with 45° and 60° manipulation angles (1,074.9 vs 715.9 s and 657.9 s with p < 0.05 and p < 0.01, respectively). The 90° manipulation angle had the greatest muscle workload by the deltoid and trapezius of the extracorporeal and intracorporeal limbs and the extracorporeal dominant arm extensor and flexor groups. In the second experiment, the short instruments had a shorter mean execution time than the standard-length instrument (572.05 vs 618.75 s; p < 0.01). There was less muscle workload with the short than with the standard-length instrument by the extracorporeal dominant forearm extensor and flexor muscle groups and the deltoid of extracorporeal dominant and intracorporeal limbs. There were no significant differences in leaking pressure or placement error score between the different manipulation angles and instrument lengths. Conclusion The best ergonomic setup in hand-assisted laparoscopic surgery entails a manipulation angle of 45° to 60° and use of an instrument with a shorter shaft than standard laparoscopic length. The study of manipulation angle was presented at the 12th International Congress of the European Association for Endoscopic Surgery (EAES) and Other Interventional Techniques, Barcelona, June 2004; the experiment on instrument length was presented at the Technology Award Session, the 13th International Congress of the EAES, Venice, June 2005.