RESUMEN
Objective:To explore the morphological characteristics of the pectoralis major muscle and the anatomical relationship of adjacent structures .Methods:A total of 156 patients undergoing thyroid surgery at the First Hospital of Anhui University of Science & Technology and the First Affiliated Hospital of University of Science and Technology of China from Dec 2020 to Sep 2022 were includeed. Those adopting routine endoscopic thyroidectomy by gasless unilateral axillary approach were assigned to group A,and searching for the sternocleidomastoid muscle through the pectoralis major muscle gap on this basis to group B.Results:Among the 78 patients in group B, a total of 71 (91%) cases were found to have a typical sternocleidomastoid muscle gap, and in 7 (9%) cases were not found. The morphology phenotypes of the gap between the clavicular part and thoracic ribs part of the pectoralis major muscle was found in 3 types: obvious separation type (typeⅠ), inconspicuous separation-partially overlapped type (typeⅡa), and inconspicuous separation-completely anastomosed type (type Ⅱb). The mean duration of surgery in group B was less (105±15) min than that in group A (156±27) min ( t=14.523, P<0.01); postoperative one day drainage in group B was less (49±6) ml than that in group A (51±6) ml ( t=2.273, P=0.024). There was no statistically significant difference in intraoperative bleeding, postoperative hospital stay and complication rate between the two groups ( t=0.557, P=0.578; t=0.134, P=0.894; χ2=1.844, P=0.174). Conclusion:The search for the sternocleidomastoid muscle through the pectoralis major muscle gap in the endoscopic thyroidectomy by gasless unilateral axillary approach can shorten the duration of surgery and improve the efficiency of surgery.