Relevance
Nowadays in clinical practice ultrasound is often used as part of a comprehensive examination of a patient with a ventral hernia, due to its high specificity (81.8%) [1]. Ultrasound is also necessary for the primary inguinal herniasdiagnosis. But its use is not informative when examining the inguinal region in previously operated patients, especially after performing operations with the use of polypropylene meshes. In such cases computed tomography (CT) is the optimal imaging method. Also it is appropriate for differential diagnosis with other hernias types, with difficulties in diagnosis especially in elderly patients [2, 3, 4] and in the diagnosis of postoperative complications. CT is also used in the examination of this such patients category when the differential diagnosis between the hernias types and the choosing of treatment tactics are difficult. CT scans can detect such complications as wound infection, seroma formation, intestinal obstruction, wound of hollow organs, bladder, and others [5—8].
It is very important for doctor to have a clear anterolateral abdominal wall normal variants CT anatomy understanding in order to recognize pathological conditions. With prompt diagnosis of predisposing factors and with the current development of treatment technologies, it is possible to minimize the duration of disability and the risk of relapse to 1.4—2% [10]. SXCT allows for a comprehensive assessment of the operated inguinal region and is performed to clarify the expected postoperative complications after non-prolonged hernioplasty with a prosthetic mesh, to determine the optimal treatment strategy for the complication — conservative treatment, percutaneous or open surgical drainage [5, 13, 14].
In this study, we have studied in detail the inguinal region CT anatomy in order to confirm the feasibility of its use to determine the inguinal canal geometric characteristics. This study has convincingly proved that the CT anatomy study can now be considered a good alternative to dissecting topographic anatomy on cadavers.
The study aim: to study the inguinal space topographic anatomy features by direct 3D scanning and analysis of CT studies of a randomized both sexes patients sampling who do not have pathological or postoperative changes in the anterior abdominal wall, in order to determine the criteria for predisposition to the development of inguinal hernias.
Purposes
1) To study 220 CT studies of a randomized both sexes patients sampling with various types of pathology not related to the anterior abdominal wall.
2) To work out the method of the inguinal region identification and its the structures measurement by sing the Vidar DICOM Viewer program.
3) To study the distribution ofthe inguinal canal quantitative characteristics in different sampling groups (age, gender, body type and type of inguinal canal).
4) Using topographical and anatomical methods of investigation and direct 3D laser scanning of the anatomical object, to clarify the features of the topography of the inguinal space and verify the accuracy of the measurements obtained during CT examination.
5) To evaluate the patterns of the inguinal canal quantitative characteristics changes in different sampling groups.
6) Work out a technique for creating the inguinal canal parametric 3D models using three-dimensional reconstructions in the SolidWorks software based on data obtained from studying virtual slices made using the Vidar DICOM Viewer software.
Materials and methods
The SXCT has a more or less exressed negative effect on the body, in the course of this study, we used CT data from patients who had previously performed this study for some other reason.
SXCT allows to perform cross-sections in several planes, which makes it possible to obtain the scanned area 3D reconstructions. Moreover, unlike ultrasound, SXCT is a more accurate method of examination. The tomograms used in our study were obtained on the multidetector row spiral CT device "Aquilion-TSX-101A". The sections had a thickness and pitch of 0.5 to 1 mm, which were considered acceptable for identifying and measuring various anatomical structures and clarifying the topographic and anatomical features of the anterior abdominal wall.
220 CT scans of a randomized patients who did not have pathological or postoperative changes in the anterior abdominal wall sampling were studied 15 studies were excluded from the total sample: 9-due to lack of information; 3-due to the presence of a volume formation of unclear etiology in one of the inguinal regions. As a result, the number of studies reviewed was 206. Their analysis was carried out using the Vidar DICOM Viewer software in 3 planes (frontal, sagittal, and coronary).
The CT scans data allowed to:
1) to specify the inguinal space size;
2) to identify and measure the inner and outer inguinal ring;
3) to measure the inguinal canal length;
4) to determine the inguinal space type;
5) to indirectly determine the patient body type (after measuring the abdomen transverse index);
6) to determine the correlation between age and the inguinal space type;
7) to identify the correlation between sex and the inguinal space type;
8) to determine the correlation between the body type and the inguinal space type;
9) to test the method of anterior abdominal wall and inguinal region anatomical structures analysis and measurement.
All quantitative data and measurements are recorded in the form of a table, for their subsequent analysis and statistical processing using the "STATISTICA-10".
In order to study in detail the anterior abdominal wall posterior surface anatomical and topographical features the direct 3D scanning method was used (Fig. 1). This study was performed on 20 male corpses. The method allows to perform measurements of anatomical parameters with an accuracy greater than any other measurement method, such as: direct measurement on anatomical material and measurement using 3D reconstructions obtained from CT data. Also 3D scans are the most informative and detailed cybernetic analogues of real-life anatomical objects, which allows to be used for a comprehensive study of the latter. In this study, the direct 3D scanning method was used to verify the accuracy of measurements obtained during the study of CT data.
In preparation for 3D scanning the anterior abdominal wall horizontal incision 15—20 cm long was made 2—3 cm below the navel. The lower flap of the dissected anterior abdominal wall was stitched with 6—8 ligatures, after which was turned forward and up, pulling the ligatures and attaching them to the arc of the pathoanatomical table (Fig. 1, 2). Next the 3D scanner Range Vision Spectrum was installed on the side table, the "marks" were laid out and scanning of the posterior surface of the anterior abdominal wall was started.
Fig. 1. Range Vision Spectrum 3D scanner when performing a direct scan of the posterior surface of the anterior abdominal wall on anatomical material.
a — rear view; b — front view.
Fig. 2. 3D scan of the posterior surface of the anterior abdominal wall.
The lower flap of the wound is raised and fixed by ligatures to the arc (a); a 3D model of the same area in the «solid fill» mode (b). (The 3D model is scaled and rotated at the same angle to the observer as image 2, a).
After all the parietal peritoneum leaf was separated from the preperitoneal tissue.The thin preparation in the projection of the lateral and medial inguinal fossae, as well as injection of the lower epigastric arteries and veins was performed in order to improve visualization on the background of the surrounding tissues. After that, a Range Vision Spectrum 3D scanner was installed on the side table, the "tags" were put again and the anterior abdominal wall deserized posterior surface was scanned (Fig. 3).
The resulting 3D models were further processed (removing uninformative image fragments) (Fig. 3a). After the initial treatment, the following parameters were measured: the linear size and area of the supravesical, medial, and lateral inguinal pits, the distance between the lateral inguinal fossa lateral edge and the the medial inguinal fossa medial edge (the inguinal canal length).
The results were processed and recorded in the Microsoft Excel program (Microsoft Corporation), and graphical models were built using the CorelDRAW Graphics Suite X3 software package (Corel Corporation). Measurements on the obtained 3D models were made using the software SolidWorks 2016 (Dassault Systèmes, France) (Fig. 3b).
Fig. 3. 3D-scans of the back surface of the anterior abdominal wall-3D models are shown in the «solid fill» mode with their different positions in space.
a — initial data; b — measurements using SolidWorks 2016 SOFTWARE (Dassault Systèmes, France): the height and width of the deep inguinal ring on the left were measured.
Research results
Inguinal space CT-anatomy
The technique for identifying and measuring the inguinal area structures using the Vidar DICOM Viewer program was developed and used in practice.
The technique protocol is:
1. The frontal section was used to determine the pubic joint.
2. Set the horizontal plane of the slice. The anterior superior iliac spines and the iliac crests served as reference points. At this stage, the interosseous distance (distancia bispinalis) was measured (Fig. 4).
Fig. 4. Distancia bispinalis (LBiC= 240.8 mm).
Then the intercostal distance (distancia bicostarum) was measured in the frontal plane by drawing a straight line between the sections of 10 ribs (Fig. 5).
Fig. 5. Distancia bicostalis (LBiC=346.0 mm).
The distancia bicostarum value percentage ratio to the distancia bispinalis one value let to estimate the patient's abdomen transverse index. An index greater than 100 corresponds to the male abdomen form, an index equal to 100 corresponds to the cylindrical abdomen form, and an index less than 100 corresponds to the female one. An index of 100 was not obtained in any of the observations. So there was virtually no transitional type between the male and female types of abdominal structure. Thus, this range had been changed: male type — more than 105, cylindrical — from 95 to 105, female-less than 95.
3. For the purpose of accurate identification in the cut plane of the inguinal space, sections were sequentially analyzed when the cut plane shifted at a slow pace from the surface to the depth (Fig. 6). The interest zone is bounded above and medially by the lower internal oblique muscle edge, connected by its aponeurotic part to the lateral edge of the rectus abdominis, and by the inguinal ligament — from below and laterally.
Fig. 6. Size (a: LR=45.4 mm, HR=17.6 mm; LL=45.5 mm, HL=19.4 mm) and the area (b: SR=699.5 mm2; SL=648.1 mm2) of the inguinal space.
4. After that the most informative position was recorded. The measurements were performed using the Vidar DICOM Viewer program with an accuracy of one hundredth of a millimeter (0.01 mm). Three measurements of each parameter nd their average value were recorded. This way gives the opportunity minimize the measurement error.
5. Using the method described above, the superficial inguinal ring was identified (Fig. 7), which is visualized on the most anterior frontal pubic bone and pubic joint slice, in the form of a triangular formation located about 2—3 cm laterally from the median line.
Fig. 7. Dimensions of the superficial inguinal ring (LR1=14.5 mm, LR2=16.2 mm, LR3=18.5 mm; LL1=14.2 mm, LL2=15.4 mm, LL3=16.4 mm) and its distance from the median line (LR=30.8 mm; LL=30.8 mm).
The external inguinal ring is bounded by three anatomical structures that give it a triangular shape (Fig. 8a, b). The size L1 is the side formed by the intervertebral fibers; the size L2 is the side formed by the external oblique abdominal muscle aponeurosis lateral pedicle, the size L3 is the side formed by the external oblique abdominal muscle aponeurosis medial pedicle.
Fig. 8. The superficial inguinal ring.
a — schematic representation of (highlighted in red): 1—pubic tubercle, 2—lateral leg of aponeurosis of the external oblique abdominal muscle (L2), 3—inguinal ligament, 4 — aponeurosis of the external oblique abdominal muscle, 5 — anterior superior iliac spine, 6—rectus abdominis, 7—medial leg of aponeurosis of the external oblique abdominal muscle (L3), 8 — intercostal fibers (L1), 9 — pubic joint; b — CT image of the external inguinal ring. L1-intercostal fibers; L2-lateral leg of aponeurosis of the external oblique abdominal muscle; L3-medial leg of aponeurosis of the external oblique abdominal muscle.
6. The deep inguinal ring (Fig. 9, 10) was visualized on the frontal section deeper, at the level of the transverse fascia and laterally from the lower epigastric vessels. In the frontal section most often is oval shape.
Fig. 9. Dimensions of the deep inguinal ring (HR=16.6 mm, WR=29.7 mm; HL=23.6 mm, WL=40.4 mm).
Fig. 10. Variability in the size of the deep inguinal ring in the same individual.
7. The distance on the frontal section from the superficial inguinal ring outer lateral edge to the deep inguinal ring medial edge corresponds to the inguinal canal length (Fig. 11).
Fig. 11. Length of the inguinal canal (LR=39.6 mm; LL=37.6 mm).
During analyzing the research results, the following patterns were found:
In the considered sampling (n = 206) 3 body types were identified: asthenic (18 or 8.7%), normosthenic (40 or 19.4%) and hypersthenic (148 or 71.8%). In addition, the sampling was divided by inguinal space types: slit-shaped (168 or 81.6%), oval (31 or 15%), triangular (7 or 3.4%). The results of measurements of individual structures of the anterior abdominal wall and inguinal area are shown below in Tables 1—4:
Table 1. Distribution of quantitative characteristics of the inguinal canal of the sample by age, mm
|
Characteristics |
All, n=198 |
<40 y.o., n=16 |
40—60 y.o., n=80 |
>60 y.o., n=102 |
p |
|
Age ratio (years old, y.o.) |
60.09±12.87 |
32.63±6.22 |
52.88±5.14 |
70.06±5.98 |
— |
|
Abdomen transverse index |
114.27±13.22 |
111.27±15.75 |
114.83±14.24 |
114.29±11.98 |
0.618 |
|
Inguinal space height (mm) |
13.45±5.91 |
10.89±4.2 |
12.98±5.97 |
14.21±5.99 |
0.074 |
|
Inguinal space length (mm) |
39.14±13.21 |
37.41±12.43 |
36.08±12.32 |
41.81 ±13.55 |
0.012 |
|
Inguinal space area (mm2) |
521.13±355.61 |
422.77±312.27 |
458.92±317.45 |
585.34±380.24 |
0.029 |
|
Inguinal interstice type |
1.18±0.42 |
1.13±0.34 |
1.13±0.33 |
1.24±0.49 |
— |
|
Deep inguinal ring height (mm) |
15.02±4.2 |
15.23±1.83 |
14.59±3.88 |
15.32±4.68 |
0.502 |
|
Deep inguinal ring width (mm) |
20.05±6.46 |
17.73±2.34 |
19.46±6.3 |
20.88±6.9 |
0.108 |
|
Superficial inguinal ring parameters (mm): |
|||||
|
L1 |
13.43±3.43 |
11.61±2.71 |
13.57±3.84 |
13.6±3.11 |
0.086 |
|
L2 |
14.5±3.68 |
14.04±3.95 |
14.73±3.7 |
14.39±3.65 |
0.725 |
|
L3 |
18.99±4.8 |
17.16±4.56 |
18.93±4.59 |
19.33±4.98 |
0.244 |
|
Distance from the inguinal ring to the midline (mm) |
23.68±5.01 |
23.59±4.88 |
22.65±4.6 |
24.49±5.23 |
0.047 |
|
Inguinal canal length (mm) |
37.74±7.75 |
37.83±8.72 |
39.57±7.57 |
36.31±7.51 |
0.019 |
Table 2. Distribution of quantitative characteristics of the inguinal canal of the sample by gender
|
Parameter |
Female, n=97 |
Male, n=109 |
p |
|
Age (years old, y.o.) |
60.13±14.79 |
60.06±11.1 |
0.966 |
|
Abdomen transverse index |
108.01±9.91 |
119.48±13.4 |
<0.001 |
|
Inguinal interstice height (mm) |
12.08±4.84 |
14.59±6.48 |
0.003 |
|
Inguinal interstice length (mm) |
36.92±12.82 |
40.98±13.3 |
0.031 |
|
Inguinal interstice area (mm2) |
442.23±315.83 |
586.87±374.5 |
0.004 |
|
Inguinal interstice type |
1.12±0.33 |
1.23±0.49 |
- |
|
Deep inguinal ring height (mm) |
13.93 ±2.71 |
15.93±4.96 |
0.001 |
|
Deep inguinal ring width (mm) |
18.48 ±3.88 |
21.36±7.77 |
0.002 |
|
Superficial inguinal ring parameters (mm): |
|||
|
L1 |
12.15±2.5 |
14.49±3.73 |
< 0.001 |
|
L2 |
13.4±3.44 |
15.41±3.64 |
< 0.001 |
|
L3 |
18.04±4.42 |
19.78±4.98 |
0.011 |
|
Distance from the inguinal ring to the midline (mm) |
24.6±4.55 |
22.91±5.26 |
0.017 |
|
Inguinal canal length (mm) |
38.32±6.99 |
37.26±8.34 |
0.339 |
Table 3. Distribution of quantitative characteristics of the inguinal canal of the sample by body type
|
Parameter |
Body type |
|||
|
Asthenic, n=15 |
Normosthenic, n=43 |
Hypersthenic, n=148 |
p |
|
|
Age (years old, y.o.) |
42.6±17.35 |
61.85±11.4 |
60.8±12.12 |
<0.001 |
|
Abdomen transverse index |
89.14±5.05 |
100.51±2.75 |
119.68±10.33 |
<0.001 |
|
Inguinal interstice height (mm) |
16.48±7.71 |
10.66±4.86 |
13.99±5.83 |
0.001 |
|
Inguinal interstice length (mm) |
42.69±23.31 |
31.25±12.28 |
41.03±11.8 |
<0.001 |
|
Inguinal interstice area (mm2) |
743.95±615.35 |
344.36±271.64 |
553.85±337.27 |
<0.001 |
|
Inguinal interstice type |
1.5±0.85 |
1.08±0.27 |
1.19±0.41 |
— |
|
Deep inguinal ring height (mm) |
17.46±5.93 |
13.56±3.65 |
15.25±4.12 |
0.013 |
|
Deep inguinal ring width (mm) |
24.12±11.95 |
19.43±6.04 |
19.94±6.02 |
0.111 |
|
Superficial inguinal ring parameters (mm): |
||||
|
L1 |
11.97±2.95 |
12.19±3.06 |
13.86±3.46 |
0.008 |
|
L2 |
14.37±3.69 |
11.87±3.53 |
15.22±3.41 |
<0.001 |
|
L3 |
17.11±5.13 |
16.47±3.74 |
19.8±4.79 |
<0.001 |
|
Distance from the inguinal ring to the midline (mm) |
26.42±5.15 |
24.98±5.15 |
23.14±4.87 |
0.024 |
|
Inguinal canal length (mm) |
31.85±10.83 |
38.01±8.12 |
38.07±7.3 |
0.047 |
Table 4. Distribution of quantitative characteristics of the inguinal canal of the sample by type of inguinal canal
|
Parameter |
Inguinal space type |
|||
|
Slit-shaped, n=165 |
Oval-shape, n=37 |
Triangular — shape, n=4 |
p |
|
|
Age (years old, y.o.) |
59.83±13.27 |
61.07±11.23 |
64.67±1.15 |
0.736 |
|
Abdomen transverse index |
114.03 ±13.45 |
116.43±11.15 |
105.52±19.73 |
0.34 |
|
Inguinal interstice height (mm) |
11.85±4.46 |
20.36±4.35 |
32.03±9.6 |
<0.001 |
|
Inguinal interstice length (mm) |
35.78±11 |
54.38±8.36 |
71.27±17.03 |
<0.001 |
|
Inguinal interstice area (mm2) |
402.43±228.18 |
1050.69±191.19 |
1753.77±91.61 |
<0.001 |
|
Inguinal interstice type |
1±0 |
2±0 |
3±0 |
— |
|
Deep inguinal ring height (mm) |
14.52±3.94 |
16.97±4.39 |
23.1±3.16 |
<0.001 |
|
Deep inguinal ring width (mm) |
19.44±5.96 |
21.66±6.07 |
37.63±11.04 |
<0.001 |
|
Superficial inguinal ring parameters (mm): |
||||
|
L1 |
13.23±3.3 |
14.23±4.03 |
16.33±1.97 |
0.114 |
|
L2 |
14.31±3.6 |
15.27±4.1 |
17.17±2.2 |
0.188 |
|
L3 |
18.76±4.6 |
19.6±5.63 |
25.6±1.56 |
0.037 |
|
Distance from the inguinal ring to the midline (mm) |
24±4.99 |
21.18±4.13 |
30.8±1.21 |
0.001 |
|
Inguinal canal length (mm) |
37.8±7.91 |
38.45±6.16 |
27.57±8.56 |
0.066 |
According to the obtained data — the inguinal space height (p = 0.074) and the inguinal space area o (p = 0.029) increase with the age. There was no significant difference between the inguinal space type and age. Significant differences between the age and size of the inner inguinal ring, the outer inguinal ring and the inguinal canal length were also not revealed.
The abdomen transverse index value in men on average was greater than in women (p <0.001). The inguinal interstice height (p = 0.003) and length (p = 0.031) in men were also greater than in women. The inguinal interstice area in men was larger than in women (p = 0.004). The height and width of the inner inguinal ring were greater in men than in women (p = 0.001; 0.002, respectively). The dimensions of the superficial inguinal ring (L1, L2, L3) are larger in men than in women (p <0.001; <0.001; = 0.011, respectively). The distance from the median line to the superficial inguinal ring was less in men than in women (p = 0.017). There were no significant differences in the length of the inguinal canal of men and women and no significant differences in the inguinal interstice type.
According to observations normosthenic and hypersthenic body types are more common in older people (p <0.001). The abdomen transverse index in persons with a hypersthenic body type is greater than one in normosthenic body type. In the normosthenic type the abdomen transverse index is greater than in the asthenic body type (p <0.001). The inguinal space height in normosthenic body type persons is less than in persons with the asthenic type (p =0.001). The inguinal space height in normosthenic body type persons is less than in persons with the hypersthenic type (p=0.001). The inguinal space height in asthenic individuals is greater than in hypersthenic individuals (p =0.001). The inguinal space length in normosthenic body type persons is less than that of the asthenic body type (p<0.001); the length of the inguinal space in persons of the normosthenic body type is less than that of the hypersthenic body type (p <0.001). The length of the inguinal space in asthenic individuals is greater than in hypersthenic individuals (p <0.001). The area of the inguinal space in persons of the normosthenic body type is less than in persons of the asthenic type (p <0.001). The area of the inguinal space in persons of the normosthenic body type is smaller than in persons of the hypersthenic type (p <0.001); the area of the inguinal space in persons of the asthenic body type is larger than in persons of the hypersthenic type (p <0.001). There was no significant correlation between the body type and the type of inguinal space. The height of the deep inguinal ring in persons of the normosthenic body type is less than in persons with the asthenic type (p =0.013). The height of the deep inguinal ring in persons with a normosthenic body type is less than in persons with a hypersthenic body type (p =0.013). The height of the deep inguinal ring in asthenic individuals is greater than in hypersthenic individuals (p =0.013). There was no significant correlation between the width of the deep inguinal ring and body type. The size of the L1 of the superficial inguinal ring in asthenic individuals was smaller than in normosthenic individuals, and in hypersthenic individuals it was larger than in normosthenic individuals (p =0.008). The dimensions of the superficial inguinal ring (L2, L3) in normosthenic individuals were smaller than in asthenic individuals (p <0.001; p <0.001); the size of the superficial inguinal ring (L2, L3) in persons of the normosthenic body type was smaller than in persons of the hypersthenic type (p <0.001; p <0.001). The dimensions of the superficial inguinal ring (L1, L2, L3) in asthenic individuals are smaller than one in hypersthenic individuals (p =0.008; p <0.001; p <0.001). The distance from the median line to the superficial inguinal ring in asthenic individuals is greater than in normosthenic individuals, and in normosthenic individuals it is greater than in hypersthenic individuals (p =0.024). The length of the inguinal canal in asthenic individuals is less than in normosthenic and hypersthenic individuals (p =0.047). There was no significant difference in the length of the inguinal canal in individuals with different body types.
The inguinal interstice height, length and area in the slit-like inguinal space type is less than in the oval, and in the oval — less than in the triangular (p <0.001; p <0.001; p <0.001). The inner inguinal ring height and width in the slit — like inguinal space type is less in the oval, and in the oval-less than in the triangular (p <0.001; p <0.001; p <0.001). A significant difference was found only in the value of L3 and the external inguinal ring size (p =0.037). These indicators are less in the slit type than with the oval, and with the oval-less than with the triangular inguinal space type. The distance from the median line in the oval type is less than (p =0.001); in the oval type less than in the triangular type (p =0.001); in the slit type less than in the triangular type (p =0.001). There was no significant difference in the length of the inguinal canal between the slit-shaped and oval types of inguinal space.
At the final stage of CT data proceeding using the original algorithm [9], automatic segmentation of some CT scans was performed in the Inobitek DICOM-Viewer program. The resulting grid was edited in the MeshLab program (Fig. 12).
Fig. 12. 3D-models (a—c) of the anterior abdominal wall and inguinal region of the patient [12].
Obtaining patient anterior abdominal wall detailed three-dimensional models before the operation on a natural scale based on the CT data make possible:
• to take into account the anatomical structure features, inguinal canal deformities and injuries, leading to abdominal organs pathological protrusion;
• to determine the mesh implant shape in accordance with the individual features of the anatomical structure of the patient's abdominal wall;
• to perform subsequent mesh implant shape correction;
• to make a detailed the operation plan.
A mathematical analysis of the inguinal canal spatial characteristics in individuals with different body types allowed to propose and justify from a topographical and anatomical point of view a minimally invasive method for the treatment of repairable inguinal hernias by injecting a mixture of polymers into the lumen of the inguinal canal under ultrasound control [11, 12].
Based on the virtual sections proceeding obtained data using the Vidar DICOM Viewer software, a inguinal canal parametric three-dimensional (statistical) model was constructed in the SolidWorks software based on three-dimensional reconstructions. This model included the following structures: a fragment of the pelvis, the inguinal ligament, the transverse fascia passing into the spermatic cord internal seminal fascia, the lower epigastric vessels, the internal oblique and transverse muscles left lower edges, the external oblique abdominal muscle aponeurosis (Fig. 13). The choice of the above structures was made from the practical expediency point of view. , The inguinal canal slit-like gap volume was calculated for different body types by using the created model. Also the main stages of the proposed surgical intervention were developed (Fig. 13, 14).
Fig. 13. Comparison of slices made in the Vidar DICOM Viewer software and the created parametric model of the inguinal canal at different positions in space.
Fig. 14. Statistical parametric model of the inguinal canal based on topographic and anatomical measurements in the Vidar DICOM Viewer software.
As a result of this research part, an algorithm for preoperative particular patient inguinal canal 3D modeling was developed, followed by the calculation of all necessary characteristics using standard tools and procedures according to SolidWorks software. In the puncture-infusion method development for the treatment inguinal hernias repairable, the most important quantitative inguinal canal characteristics is its volume. But it was calculated using the standard "fill" operation, followed by the boolean operation of subtracting the operand corresponding to the volume of the spermatic cord (Fig. 15).
Fig. 15. Individualized 3D-reconstruction of the inguinal canal of a normosthenic patient, built in SolidWorks software based on CT data and the procedure for calculating the volume of the canal.
For all body types, the inguinal canal volume magnitude does not exceed 24 cm3 (Table. 5), which allowed to make a conclusions about the possibility of quickly and safely filling the inguinal canal space with the developed polymer mixture.
Table 5. The volume of the inguinal canal in individuals with different body types
|
Parameter |
Body type |
|||
|
Asthenic, n=15 |
Normosthenic, n=43 |
Hypersthenic, n=148 |
p |
|
|
Age (years old, y.o.) |
42.6±17.35 |
61.85±11.4 |
60.8±12.12 |
<0.001 |
|
Inguinal canal volume, cm3 |
23.15±6.04 |
17.51±1.73 |
19.81±5.23 |
<0.001 |
The anterior abdominal wall posterior surface direct 3D scanning.
The 3D models obtained as a result of anterior abdominal wall posterior surface scanning were further processed: uninformative image fragments were removed using the SolidWorks 2016 software (Fig. 16).
Fig. 16. Stages of processing a three-dimensional model of the anterior abdominal wall back surface using the tools of the SolidWorks 2016 program. The process of deleting uninformative image fragments.
a — first stage; b — second stage.
The three-dimensional objects obtained as a result of processing are 3D models that allow to study in detail the topographical and anatomical anterior abdominal wall posterior surface features in the inguinal interstice area (Fig. 17).
Fig. 17. Pre-processed three-dimensional model of the anterior abdominal wall posterior surface at different angles of rotation in space relative to the observer (in the frontal plane (a), at an angle (b)).
1 — plica umbilicalis mediana; 2 — fossa supravesicalis; 3 — plica umbilicalis medialis; 4 — fossa inguinalis medialis; 5 — plica umbilicalis lateralis; 6 — fossa inguinalis lateralis.
Three-dimensional anterior abdominal wall posterior surface models obtained by scanning with a Range Vision Spectrum 3D scanner were used to calculate the anterior abdominal wall posterior surface geometric characteristics and linear folds and pits dimensions. The calculated parameters were: the height, width and area of the lateral, medial inguinal and supravesical pits, the inguinal canal length, the inguinal interstice length and height. The obtained data were entered in a table and compared with the data of the study on anatomical material and the data of inguinal region CT-anatomy study (Table 6).
Table 6. Comparison of measurement data for the spatial characteristics of the inguinal canal on 3D models obtained by 3D-scanning of the posterior surface of the anterior abdominal wall with measurement data obtained from measurements on anatomical material, as well as with CT measurements
|
Parameter |
3D scanning, n=30 |
Direct measurement, n=30 |
CT, n=30 |
|||
|
M±SD |
Me |
M±SD |
Me |
M±SD |
Me |
|
|
The inguinal interstice area (mm2) |
492.48±236.22 |
540.51 |
499.97±244.57 |
541.49 |
611.52±352.72 |
607.45 |
|
The lateral inguinal fossa area (mm2) |
283.55±67.99 |
254.69 |
280.71±66.69 |
254.50 |
252.51±144.85 |
234.00 |
|
The inguinal canal length (mm) |
40.34±2.72 |
39.59 |
40.07±2.64 |
39.50 |
38.32±8.60 |
39.40 |
The measurement data proceeding of the inguinal interstice and lateral inguinal fossa areas, the inguinal canal length revealed that the distribution does not correspond to normal, respectively, nonparametric methods were used for further analysis. Very high Spearman rank correlation coefficients (0.99) were obtained when comparing the measurement using a 3D scanner and direct measurement for all three parameters (Fig. 18).
Fig. 18. Correlation of direct measurement of the inguinal gap area (a), of the area of the inner inguinal ring (b) and of inguinal canal length (c) with data of the direct 3D scanning.
There were no significant differences in the set of nonparametric criteria between CT and 3D scanning measurement, as well as between CT and direct measurement (p >> 0.05).
The data obtained by measuring the inguinal canal spatial characteristics using 3D scanning are comparable to those obtained by direct measurement on anatomical material and with the data obtained by studying CT data using the Vidar DICOM Viewer software (Table 6), (Fig. 19). These results allow to conclude that it is appropriate to use CT data of patients to measure the spatial characteristics of the inguinal canal using the Vidar DICOM Viewer software, the accuracy and reliability of the obtained data.
Fig. 19. Results of measuring the inguinal space area (a), the area of the inner inguinal ring (b) and of inguinal canal length measurement (c) during direct measurement, 3D scanning and CT.
Discussion
An research important feature is the fact that in the topographic and anatomical research part, not only a direct-acting, "direct" study was performed on anatomical objects using preparation and measurement standard methods, but also the construction of abstract mathematical models — three-dimensional the anterior abdominal wall posterior surface scans using a 3D scanner and performing accurate measurements with their usage. Such modeling made it possible to significantly strengthen the evidence base and the reproducibility of the work carried out results.
The study of the inguinal space types frequency ratio and the dependence of the inguinal space size, shape and other anterior abdominal wall features on the body type, age and gender was conducted. The quantitative characteristics revealed in the study of CT anatomy allows to identify and prevent the possible inguinal hernia formation risk, thereby reducing the cost of treating patients during acute pathology.
The present study revealed that the smallest length of the inguinal canal was observed in people with an asthenic body type. In addition, the maximum size and area of the inguinal space were also revealed in individuals with asthenic type. At the same time, the smallest size and area of the inguinal space were observed in individuals of the normosthenic body type.
Conclusions
1. As the study result the distribution of the inguinal canal quantitative characteristics of the sample by age, sex, body type and type of inguinal canal, the following data were obtained:
1) In the studied sampling (n = 206) , the ratio of asthenic: normosthenic: hypersthenic body type was 1:4: 15; and the ratio of slit — like: oval: triangular types of inguinal space was 41:8: 1.
2) With increasing age, the height and area of the inguinal space increases.
3) There was no correlation found between age and the size of the deep and superficial inguinal ring.
4) The inguinal interstice size and area in men is larger than in women. This can be considered as one of the factors that explains the greater likelihood of a direct inguinal hernia in men than in women.
5) The deep and superficial inguinal ring sizes is larger in men than in women. It may also be a factor in the relatively rare incidence of oblique inguinal hernia in females.
6) The distance from the midline to the superficial inguinal ring is smaller in men than in women, as the female pelvis is wider.
7) There is no correlation between the length of the inguinal canal, the type of inguinal space, and sex.
8) The smallest inguinal interstice size and area were found in normosthenic body type persons. In addition, when comparing these parameters, it was found that such indicators are more important in people with asthenic type compared to hypersthenic body type. The risk of developing inguinal hernias in the asthenic type is greater than in the hypersthenic type, and in the hypersthenic type, it is greater than in the normosthenic body type.
9) A correlation was found between the deep inguinal ring height and the body type (asthenic type> hypersthenic type> normosthenic type), while the deep inguinal ring width did not correlate with any other measurements.
10) The superficial inguinal ring oblique-vertical size (L1), as well as the oblique-transverse dimensions (L2 and L3) are maximal in hypersthenic type people (G > A > H).
11) The superficial inguinal ring in asthenic individuals is located further from the median line than in normosthenic individuals. The smallest distance was observed in individuals with a hypersthenic body type.
12) The inguinal canal with the smallest length was detected in persons with an asthenic body type. There was no significant difference in the length of the inguinal canal between individuals with normosthenic and hypersthenic body types.
13) The size and area of the inguinal interstice have a minimum value for the slit-like type, followed by the oval and triangular types of the inguinal interstice .
14) The deep inguinal ring dimensions also have a minimum value for the slit-like type, followed by the oval and triangular types of the inguinal gap. Therefore, the lowest risk of developing an oblique inguinal hernia is found in individuals with a slit-like type of inguinal space, the second highest risk is the oval type, and those with a triangular type of inguinal space are most likely to develop an indirect inguinal hernia.
15) The oblique-transverse size (L3) of the external inguinal ring decreases in the following sequence: slit-shaped, oval, triangular type. Other dimensions of the outer ring did not have a statistically significant difference.
16) The inguinal canal smallest length is marked with a triangular shape of the inguinal interstice. Individuals with this type of inguinal space have the greatest tendency to form an oblique inguinal hernia.
2. The results obtained by comparing the data of direct measurement, 3D scanning and CT data allow to conclude that using CT to measure the inguinal canal spatial characteristics and the accuracy and reliability of the data obtained.
3. The detailed individualized three-dimensional parametric inguinal region and inguinal canal models creation make it possible to take into account the features of the anatomical structure of each individual patient. Also it allows to correct the mesh implant shape in accordance with the individual features of the anatomical structure of the of the patient, and is also a good basis for the development of new inguinal hernias treatment methods.
The participation of the authors:
Concept and design of the study — A.A. Smirnov, E.M. Trunin, S.S. Dydykin
Data collection and processing — M.J. Mowlabucus, R.F. Gainullina, S.Yu. Rakita, A.V. Ostyakova, A.V. Aleksandrov
Statistical processing of the data — A.L. Ovsepyan, P.A. Blake
Text writing — A.A. Smirnov, E.M. Trunin, S.S. Dydykin, A.L. Ovsepyan, P.A. Blake
Editing — A.A. Smirnov, E.M. Trunin, Yu.L. Vasiliev
The authors declare no conflicts of interest.