Study on sex differences and potential clinical value of three-dimensional computerized tomography pelvimetry in rectal cancer patients

Table 1 Pelvic measurement parameters and definitions

Parameter name	Definition
Anterior-posterior diameter of pelvic inlet (AB)	Distance between the midpoint of the superior pubic symphysis and the midpoint of the anterior margin of the sacral promontory
Transverse diameter of pelvic inlet (PQ)	Maximum distance between the left and right iliopectineal line
Anterior-posterior diameter of mid-pelvis (CD)	Distance between the midpoint of the inferior pubic symphysis and the midpoint of the sacrococcygeal junction
Anterior-posterior diameter of pelvic outlet (CE)	Distance between the midpoint of the inferior pubic symphysis and the tip of the coccyx
Interischial spine diameter (LM)	Shortest distance between the ischial spines
Interischial tuberosity diameter (NO)	Shortest distance between the ischial tuberosities
Superior-inferior diameter of the pubic symphysis (AC)	Distance between the superior and inferior borders of the pubic symphysis
Sacrococcygeal distance (BE)	Distance between the midpoint of the anterior margin of the sacral promontory and the tip of the coccyx
Superior-inferior diameter of sacrum (BD)	Distance between the midpoint of the anterior margin of the sacral promontory and the midpoint of the sacrococcygeal junction
Sacrococcygeal angle (α)	The angle between the extended lines of the anterior-posterior diameter of pelvic inlet and the anterior-posterior diameter of pelvic outlet
Sacropubic angle (β)	Angle between the extended lines of the anteroposterior diameter of pelvic inlet and the anterior-posterior diameter of mid-pelvis
Sacrococcygeal curvature height (FI)	Vertical distance from the most convex point of the sacrococcygeal curve to the sacrococcygeal distance
Sacral curvature height (FH)	Vertical distance from the most convex point of the sacral curve to the superior-inferior diameter of sacrum
Superior pubococcygeal diameter (AE)	Distance between the midpoint of the superior pubic symphysis and the tip of the coccyx
Anterior-posterior sacropubic distance (FG)	Vertical distance from the most convex point of the sacrococcygeal curve to the superior-inferior diameter of pubic symphysis or its extended line

Among the 15 pelvic diameter and angle parameters, there are 5 parameters reflecting anterior-posterior diameter of pelvic width: anterior-posterior diameter of pelvic inlet, anterior-posterior diameter of mid-pelvis, anterior-posterior diameter of pelvic outlet, superior pubococcygeal diameter, and anterior-posterior sacropubic distance. There are three parameters reflecting left and right diameter of pelvic width: transverse diameter of pelvic inlet, interischial spine diameter and interischial tuberosity diameter. There were three parameters reflecting pelvic depth: superior-inferior diameter of the pubic symphysis, sacrococcygeal distance, and superior-inferior diameter of sacrum. There are two parameters reflecting the curvature of the sacrococcygeal bone: sacrococcygeal curvature height and sacral curvature height. There are two parameters comprehensively assessing sacrococcygeal (sacral) arc length and bending degree, the superior-inferior diameter of the pubic symphysis and the distance between the pubic symphysis and sacrococcygeal bone: sacrococcygeal angle and sacropubic angle.

Table 2 Soft tissue measurement parameters and definitions

Parameter name	Definition
Rectal area (a)	Area of the rectum at the level of the ischial spine
Mesorectal fat area (b)	Area of the mesorectal fat at the level of the ischial spine
Visceral fat area (c)	Area of visceral fat at the level of the umbilicus
Subcutaneous fat area (d)	Area of subcutaneous fat at the level of the umbilicus
Waist circumference (e)	Circumference of the waist at the level of the umbilicus
Anterior-posterior abdominal diameter (RS)	It refers to the distance measured from the line connecting the umbilicus to the spinous process at the level of the umbilicus, between the abdominal wall section and the lumbar section
Transverse abdominal diameter (TU)	It refers to the distance measured from the level of the umbilicus to the horizontal line at the anterior edge of the lumbar vertebrae

Table 3 Normality test analysis of each variable

Variable name	W value	P value
Anterior-posterior diameter of pelvic inlet	0.9905098	0.1642
Transverse diameter of pelvic inlet	0.9914321	0.2294
Anterior-posterior diameter of mid-pelvis	0.9758847	0.0009
Anterior-posterior diameter of pelvic outlet	0.9716010	0.0002
Interischial spine diameter	0.9840155	0.0146
Interischial tuberosity diameter	0.9848102	0.0195
Superior-inferior diameter of the pubic symphysis	0.9878909	0.0617
Sacrococcygeal distance	0.9947691	0.6552
Superior-inferior diameter of sacrum	0.9883327	0.0729
Sacrococcygeal angle	0.9931951	0.4174
Sacropubic angle	0.9720830	0.0003
Sacrococcygeal curvature height	0.8480501	0.0000
Sacral curvature height	0.9947091	0.6454
Superior pubococcygeal diameter	0.9918030	0.2615
Anterior-posterior sacropubic distance	0.9114720	0.0000
Anterior-posterior diameter of pelvic inlet/sacrococcygeal distance	0.9723249	0.0003
Visceral fat area	0.9564061	0.0000
Subcutaneous fat area	0.9635344	0.0000
Waist circumference	0.9939451	0.5244
Anterior-posterior abdominal diameter	0.9863249	0.0343
Transverse abdominal diameter	0.9939991	0.5327
Rectal area	0.9221744	0.0000
Mesorectal fat area	0.9777443	0.0016

P < 0.05 indicates that it does not conform to a normal distribution, and the P value expressed by < 0.001.

Table 4 Clinical and pathological characteristics data of 218 patients in the laparoscopic radical resection for rectal cancer

	Range	mean ± SD or median (Q1, Q3)	No. of cases (percentage), n (%)
Age (yr)	32-89	66 (59, 74)
Sex
Male			139 (63.76)
Female			79 (36.24)
BMI (kg/m2)	14.42-31.25	22.57 ± 3.17
ASA grading
I			22 (10.09)
II			185 (84.86)
III			11 (5.05)
History of previous abdominal surgery			19 (8.72)
Neoadjuvant therapy			8 (3.67)
pTNM/ypTNM staging
0			9 (4.13)
I			53 (24.31)
II			63 (28.9)
III			93 (42.66)

If the data follows a normal distribution, it is represented as mean ± SD. If the data does not follow a normal distribution, it is represented as median (Q1, Q3). Examples (%) will be used to represent count and ordinal data. ASA: American Society of Anesthesiologists; TNM: Tumor-node-metastasis; BMI: Body mass index.

Table 5 mean ± standard deviation or median (Q1, Q3) of 16 pelvic parameters and 7 soft tissue parameters measured by 218 computerized tomography scans and comparison between sexes

Variable name	Total cases (n = 218), mean ± SD or median (Q1, Q3)	Male (n = 139), mean ± SD or median (Q1, Q3)	Female (n = 79), mean ± SD or median (Q1, Q3)	Mean comparison between sexes, P value
Anterior-posterior diameter of pelvic inlet in mm	114.36 ± 11.99	110.57 ± 10.84	121.03 ± 11.01	0.0000a
Transverse diameter of pelvic inlet in mm	123.3 ± 8.14	119.81 ± 6.57	129.44 ± 6.93	0.0000a
Anterior-posterior diameter of mid pelvis in mm	111.59 (105.76, 117.26)	109.06 (103.5, 114.76)	113.94 (109.81, 121.44)	0.0000a
Anterior-posterior diameter of pelvic outlet in mm	88.34 (82.35, 95.73)	86.45 (80.03, 91.33)	93.12 (85.32, 99.8)	0.0000a
Interischial spine diameter in mm	95.92 (88.9, 104.09)	90.77 (84.88, 96.05)	106.73 (102.53, 112.28)	0.0000a
Interischial tuberosity diameter	104.88 (96.78, 116.95)	99.58 (93.26, 108.12)	117.37 (109.52, 126.2)	0.0000a
Superior-inferior diameter of pubic symphysis in mm	41.8 ± 4.92	43.11 ± 4.99	39.49 ± 3.82	0.0000a
Sacrococcygeal distance in mm	122.92 ± 12.02	125.23 ± 11.53	118.84 ± 11.83	0.0002a
Superior-inferior diameter of sacrum in mm	105.36 ± 10.35	106.76 ± 9.79	102.9 ± 10.89	0.0101a
Sacrococcygeal curvature height in mm	39.15 (35.81, 42.96)	39.7 (36.42, 44.05)	38.3 (34.67, 41.45)	0.0204a
Sacral curvature height in mm	20.87 ± 5.66	21.14 ± 5.74	20.38 ± 5.53	0.3385
Superior pubococcygeal diameter in mm	119.39 ± 9.27	119.41 ± 8.68	119.34 ± 10.29	0.9596
Anterior-posterior sacropubic distance in mm	119.6 (113.39, 126.28)	117.03 (112.54, 123.58)	123.86 (116.48, 130.88)	0.0000a
Sacrococcygeal angle (°)	48.37 ± 7.28	50.7 ± 6.67	44.26 ± 6.47	0.0000a
Sacropubic angle (°)	33.01 (29.28, 36.75)	34.24 (30.42, 37.42)	31.48 (28.09, 35.24)	0.0028a
Anterior-posterior diameter of pelvic inlet/sacrococcygeal distance	0.93 (0.85, 0.99)	0.88 (0.83, 0.94)	0.99 (0.96, 1.08)	0.0000a
Rectal area in cm2	16.67 (12.12, 21.69)	16.69 (11.48, 21.99)	16.57 (12.44, 21.39)	0.8389
Mesorectal fat area in cm2	38.57 (26.71, 51.24)	44.17 (32.87, 53.19)	30.95 (21.2, 43.35)	0.0000a
Visceral fat area in cm2	202.65 (122.4, 259.89)	219.86 (125.28, 277.74)	174.12 (120.58, 242)	0.1184
Subcutaneous fat area in cm2	255.35 (184.82, 338.59)	235.63 (138.73, 294.54)	319.87 (226.14, 403.15)	0.0000a
Waist circumference in cm	81.69 ± 9.26	82.02 ± 9.45	81.1 ± 8.95	0.4744
Anterior-posterior abdominal diameter in cm	18.22 (16.14, 19.93)	18.26 (16.52, 20.35)	17.72 (15.29, 19.33)	0.0447a
Transverse abdominal diameter in cm	28.69 ± 2.78	28.72 ± 2.67	28.65 ± 2.99	0.8653

^aP value < 0.05. Measurement data that conforms to a normal distribution is represented by the mean ± standard deviation. If the data do not follow a normal distribution, they are represented by the median (Q1, Q3). All P values denoted by ‘e’ were found to be < 0.001.