| Objective:To obtain some information about the anatomical position of the recurrent laryngeal nerve(RLN)in the female larynx by dissecting the larynx,so as to grasp and study the anatomical features of the RLN in the female larynx,which can more effectively set a safer area for clinical thyroid surgery to reduce the damage to the RLN during thyroid operations.Methods: First,cadaveric specimens with no history of neck surgery,thyroid lesions and RLN dissection were selected.In this analysis,15 adult female cadaveric specimens fixed with 10% formaldehyde embalming were selected,with a total of 30 bilateral RLNs,aged from 18 to 60 years.The anatomical procedure was smooth.The tracheoesophageal groove(TG)was dissected bluntly from the bottom up until the RLN was identified and confirmed,then the adjacent fibrous connective tissue was completely removed and the RLN and its branches in the thyroid gland were freed.The RLN and its branches in the thyroid area are carefully observed,especially in relation to the first and second tracheal cartilage rings at the entry point of the RLN,and carefully manipulated to avoid straining and injury to the RLN and avoiding anatomical displacement of the recurrent laryngeal nerve during the dissection.The vertical distance between the upper edge of the first and second tracheal cartilage rings and the horizontal distance between the upper edge of the cartilage ring and the lateral edge of the first and second tracheal cartilage rings on the same side(the upper edge of the cartilage ring is the most anterior edge of the sagittal plane and the lateral edge is the most lateral edge of the coronal plane)and the angle formed by the tracheal edge on the same side(the tracheal edge is the line connecting the most lateral edge of the coronal plane of the tracheal ring)are determined using a straightedge and a triangular ruler.This angle is determined using a straightedge and a triangular ruler.The measurement is carried out in the order of the vertical distance from the upper edge of the second tracheal ring,the horizontal distance from the lateral edge and the angle,followed by the vertical distance from the upper edge of the first tracheal ring,the horizontal distance from the lateral edge and the angle,to ensure the accuracy of the data.The cervical segmental alignment of the bilateral RLN was then recorded separately as it branched within the thyroid surgery area.The spacing was measured using an electronic reading vernier caliper with an accuracy of 0.01 mm and the angle was measured using a protractor with an accuracy of 0.5°.All measurements and statistical analyses were carried out by the same team of researchers,and for each analysis statistical data were analysed using the SPSS 25.0 application,with data expressed as mean ± standard deviation(±s)minimum-maximum(Min-Max).A t-test was applied to compare the analysis between the female left and right RLN data,with P < 0.05 indicating that the difference was statistically significant.Results:1.Among the 15 cadavers with a total of 30 RLNs,the cervical segment of the RLN was aligned within the TG throughout on 27 sides,while the RLN on the other 3 sides was not so aligned and did not travel within the TG throughout,with the portion of the lower pole of the thyroid detached from the TG and re-entering the TG upward and from the position of the lower pole of the thyroid.1 case on the left side and 2 cases on the right side.2.Within the scope of bilateral thyroid surgery,both bilateral RLNs were seen with extra-thyroidal and laryngeal branches in 2-4 branches,including 14 cases in 2 branches(46.67%),10 cases in 3 branches(33.33%),and 6 cases in 4 branches(20.00%).According to the number of branches,RLN could be divided into two branch types,i.e.dendritic and collaterals.29 cases of RLN branch types constituted dendritic(96.97%),and only one case constituted collaterals(3.33%).3.The intersection of the tracheal cartilage ring edge and the RLN was considered as the apex of the angle,and the angle between the entry point of the RLN on the 30 sides and the tracheal edge on the same side was analyzed.8 cases or 26.67% had 0° ≤ angle<5°,18 cases or 60.00% had 5° ≤ angle <10°,2 cases or 6.67% had 10° ≤ angle <15°,and 2 cases or 6.67% had ≥15°.The angle on the left side was 6.1±1.1(0-15)° and on the right side was 6.3±1.0(0-10)°.The P difference was greater than 0.05 for both sides,and this difference was not statistically significant.4.The vertical spacing of the left and right RLN from the upper edge of the first tracheal ring was(15.40±0.75)mm and(16.76±0.53)mm,respectively;the vertical spacing from the upper edge of the second tracheal ring was(17.05±0.65)mm and(16.71±0.70)mm,respectively;the horizontal spacing from the lateral edge of the first tracheal ring was(2.81±0.13)mm and(2.93±0.13)mm,respectively.In the above data,the vertical spacing of bilateral RLN at the upper edge of the first tracheal ring,P value< 0.05,the difference was statistically significant,and the right RLN was deep in position compared with the left RLN,and the difference was small.The rest of the measured data related to bilateral RLN were compared with P-values > 0.05,and the differences were not statistically significant.Conclusion: By mastering the accurate anatomy of the entry laryngeal site of the RLN in women,this study defined the area between 14 mm below the upper edge of the first and second tracheal cartilage rings and 2 mm on either side of it as a relatively safe area,and the surgeon was able to quickly and safely discover the entry laryngeal site of the RLN during thyroid surgery,thus helping the surgeon to effectively expose the RLN,reduce the damage to the RLN during thyroid surgery,and achieve the goal of reducing the postoperative complicatios.The aim is to reduce the occurrence of postoperative thyroid complications. |
