Where is the optimal plane to mobilize the anterior rectal wall in female patients undergoing total mesorectal excision?

BACKGROUND: Since Heald proposed the total mesorectal excision (TME) procedure, the prognosis of patients with rectal cancer has been significantly improved. But Heald did not specifically describe the anterior surgical plane in female patients. And the surgical plane for mobilizing the anterior rectal wall during TME surgery in female patients remains controversial. AIM: To investigate the anatomy of the female pelvis and identify the optimal plane for mobilizing the anterior rectal wall. METHODS: We retrospectively collected surgical procedure videos and clinical data of female patients diagnosed with middle or low rectal cancer who underwent the TME procedure between January 2020 and October 2022 across six hospitals. The patients were divided into two groups based on the surgical approach used to mobilize the anterior rectal wall: The experimental group was to open the peritoneum at the lowest point of the peritonea reflection and enter the plane for mobilizing, while the control group was cut at 0.5-1 cm above the peritoneal reflection and enter another plan. Then, we compared the preoperative and postoperative information between the two groups. We also dissected and observed ten adult female pelvises to analyze the anatomic structure and compare the entry plane between the two approaches. Finally, we researched the pathological structure between the rectum and the vagina. RESULTS: Finally, 77 cases that met the criteria were included in our study. Our observations revealed that the experimental group underwent a smooth procedure, entering the plane amidst the mesorectal fascia and adventitia of the vagina, whereas the control group entered the plane between the vaginal adventitia and muscle layers. Compared to the control group, the experimental group showed a significant decrease in intraoperative bleeding [22.5 (19.5-50) mL vs 17 (5-20) mL, P = 0.01], as well as a shorter duration of hospitalization [9 (7-11.25) d vs 7 (6-10) d, P = 0.03]. Through the examination of surgical videos and cadaveric studies, we discovered that Denonvilliers' fascia is absent in females. Additionally, pathological sections further revealed the absence of Denonvilliers' fascia in females, with only loose connective tissue present between the mesorectal fascia and adventitia of the vagina. CONCLUSION: The plane amidst the mesorectal fascia and vaginal adventitia is the optimal surgical plane to mobilize the anterior rectal wall for female patients undergoing the TME procedure.

The addition of 3D printed models to enhance the teaching and learning of bone spatial anatomy and fractures for undergraduate students: a randomized controlled study.

BACKGROUND: Whether or not the addition of 3D (three-dimension) printed models can enhance the teaching and learning environment for undergraduate students in regard to bone spatial anatomy is still unknown. In this study, we investigated the use of 3D printed models versus radiographic images as a technique for the education of medical students about bone spatial anatomy and fractures. METHODS: The computed tomography (CT) data from four patients, each with a different fracture type (one spinal fracture, one pelvic fracture, one upper limb fracture, and one lower limb fracture), were obtained, and 3D models of the fractures were printed. A total of 90 medical students were enrolled in the study and randomly divided into two groups as follows: a traditional radiographic image group (presented by PowerPoint) and a 3D printed model group (combined PowerPoint and 3D models). Each student answered 5 questions about one type of fracture and completed a visual analog scale of satisfaction (0-10 points). RESULTS: No significant differences were found in the upper limb or lower limb test scores between the 3D printed model group and the traditional radiographic image group; however, the scores on the pelvis and spine test for the traditional radiographic image group were significantly lower than the scores for the 3D printed model group (P=0.000). No significant differences were found in the test-taking times for the upper limb or lower limb (P=0.603 and P=0.746, respectively) between the two groups; however, the test-taking times for the pelvis and spine in the traditional radiographic image group were significantly longer than those of the 3D printed model group (P=0.000 and P=0.002, respectively). CONCLUSIONS: The 3D printed model may improve medical students' understanding of bone spatial anatomy and fractures in some anatomically complex sites.

A novel computed method to reconstruct the bilateral digital interarticular channel of atlas and its use on the anterior upper cervical screw fixation.

Purpose. To investigate a novel computed method to reconstruct the bilateral digital interarticular channel of atlas and its potential use on the anterior upper cervical screw fixation. Methods. We have used the reverse engineering software (image-processing software and computer-aided design software) to create the approximate and optimal digital interarticular channel of atlas for 60 participants. Angles of channels, diameters of inscribed circles, long and short axes of ellipses were measured and recorded, and gender-specific analysis was also performed. Results. The channels provided sufficient space for one or two screws, and the parameters of channels are described. While the channels of females were smaller than that of males, no significant difference of angles between males and females were observed. Conclusion. Our study demonstrates the radiological features of approximate digital interarticular channels, optimal digital interarticular channels of atlas, and provides the reference trajectory of anterior transarticular screws and anterior occiput-to-axis screws. Additionally, we provide a protocol that can help make a pre-operative plan for accurate placement of anterior transarticular screws and anterior occiput-to-axis screws.

The accuracy of a method for printing three-dimensional spinal models.

BACKGROUND: To study the morphology of the human spine and new spinal fixation methods, scientists require cadaveric specimens, which are dependent on donation. However, in most countries, the number of people willing to donate their body is low. A 3D printed model could be an alternative method for morphology research, but the accuracy of the morphology of a 3D printed model has not been determined. METHODS: Forty-five computed tomography (CT) scans of cervical, thoracic and lumbar spines were obtained, and 44 parameters of the cervical spine, 120 parameters of the thoracic spine, and 50 parameters of the lumbar spine were measured. The CT scan data in DICOM format were imported into Mimics software v10.01 for 3D reconstruction, and the data were saved in .STL format and imported to Cura software. After a 3D digital model was formed, it was saved in Gcode format and exported to a 3D printer for printing. After the 3D printed models were obtained, the above-referenced parameters were measured again. RESULTS: Paired t-tests were used to determine the significance, set to P<0.05, of all parameter data from the radiographic images and 3D printed models. Furthermore, 88.6% of all parameters of the cervical spine, 90% of all parameters of the thoracic spine, and 94% of all parameters of the lumbar spine had Intraclass Correlation Coefficient (ICC) values >0.800. The other ICC values were <0.800 and >0.600; none were <0.600. CONCLUSION: In this study, we provide a protocol for printing accurate 3D spinal models for surgeons and researchers. The resulting 3D printed model is inexpensive and easily obtained for spinal fixation research.

The radiological feature of anterior occiput-to-axis screw fixation as it guides the screw trajectory on 3D printed models: a feasibility study on 3D images and 3D printed models.

Anterior occiput-to-axis screw fixation is more suitable than a posterior approach for some patients with a history of posterior surgery. The complex osseous anatomy between the occiput and the axis causes a high risk of injury to neurological and vascular structures, and it is important to have an accurate screw trajectory to guide anterior occiput-to-axis screw fixation. Thirty computed tomography (CT) scans of upper cervical spines were obtained for three-dimensional (3D) reconstruction. Cylinders (1.75 mm radius) were drawn to simulate the trajectory of an anterior occiput-to-axis screw. The imitation screw was adjusted to 4 different angles and measured, as were the values of the maximized anteroposterior width and the left-right width of the occiput (C0) to the C1 and C1 to C2 joints. Then, the 3D models were printed, and an angle guide device was used to introduce the screws into the 3D models referring to the angles calculated from the 3D images. We found the screw angle ranged from α1 (left: 4.99±4.59°; right: 4.28±5.45°) to α2 (left: 20.22±3.61°; right: 19.63±4.94°); on the lateral view, the screw angle ranged from ß1 (left: 13.13±4.93°; right: 11.82±5.64°) to ß2 (left: 34.86±6.00°; right: 35.01±5.77°). No statistically significant difference was found between the data of the left and right sides. On the 3D printed models, all of the anterior occiput-to-axis screws were successfully introduced, and none of them penetrated outside of the cortex; the mean α4 was 12.00±4.11 (left) and 12.25±4.05 (right), and the mean ß4 was 23.44±4.21 (left) and 22.75±4.41 (right). No significant difference was found between α4 and ß4 on the 3D printed models and α3 and ß3 calculated from the 3D digital images of the left and right sides. Aided with the angle guide device, we could achieve an optimal screw trajectory for anterior occiput-to-axis screw fixation on 3D printed C0 to C2 models.

The anatomic study of clival screw fixation for the craniovertebral region.

PURPOSE: To study the anatomic parameters related to clival screw and establish reference data concerning the craniovertebral fixation technique. METHODS: Morphometric measurement of the clivus and the surrounding anatomic structures were obtained on 41 dry bone specimens. Then, 2-D CT reconstruction of the craniovertebral region of 30 patients (19 men and 11 women, ranging in age from 20-64 years with an average age of 38.8 years) were performed to measure the safety range for a 3.5-mm screw placement. Nine entry points were evaluated. Finally, one male fresh cadaver specimen (age 46 years) was dissected to observe the craniovertebral region. RESULTS: The clivus faces the basilar artery, the V ~ XII cranial nerves, the pons, and ventral medulla oblongata at its intracranial surface. The longitudinal diameter of extracranial clivus was 25.87 ± 2.64 mm. The narrowest diameter of the clivus was 12.84 ± 1.08 mm, the distance between the left and right hypoglossal canal was 32.70 ± 2.09 mm at its widest part. The distance between the left and right structures, the maximum value was 49.31 ± 4.16 mm at carotid canal, the minimum value was 16.54 ± 2.04 mm at the occipital condyle. The measurement of clival screws placement simulation via 2-D CT reconstruction images shows the maximum upper insertion angle of three components the optimal entry points, the candidate points, the limit entry points was 130.19°, 125.23° and 85.72°, and the total mean screw length was 7.57, 10.13 and 15.6 mm at the vertical entry angle, respectively. CONCLUSIONS: Clival screw placement is a viable option for craniovertebral fixation. There is a safe scope for the screw length and angle of the screw placement. And, these parameters obtained in the present study will be helpful for anyone contemplating the use of clival screw fixation.

Comparative research of the thin transverse sectional anatomy and the multislice spiral CT on Pterygopalatine Fossa.

AIM: To explore a method to obtain sub-millimeter data of the thin transverse section of the pterygopalatine fossa (PPF), and to study the thin transverse sectional anatomy of the adult pterygopalatine fossa and its communicating structure for providing anatomic gist for the imaging diagnosis and minimal invasive operation when PPF diseased. MATERIAL AND METHODS: Two heads of adult cadaver without macroscopic trauma (four sides of PPF) were selected to observe. Images of 0.6 mm-thick multi-planar construction (MPR) were obtained with multislice spiral CT (MSCT) based on the superior orbitomeatal line. Then, the specimens were sliced into 0.1 mm serial section on the transverse plane with the computerized milling machine, the figures were taken with digital camera and the sectional data were stored in the computer. Lastly, the thin transversal section of PPF was investigated and compared with multislice spiral CT images acquired by MPR technique to explore and discuss the anatomy of the thin transverse section of the internal structure of PPF. RESULTS: PPF was divided into four portions: infrapterygopalatine portion, pterygopalatine ganglionic one, suprapterygopalatine one and roof of PPF according to the structural characteristics of the transverse section of PPF. The infrapterygopalatine portion communicated laterally with the infratemporal fossa through the pterygomaxillary fissure and communicated downwards with the oral cavity via palatine greater and lesser canals. The pterygopalatine ganglion was shown clearly in the pterygopalatine ganglionic portion, and its dimensions were 3.91x1.92 mm at the best layer. In the suprapterygopalatine portion, the sphenopalatine foramen and artery were obviously shown on the medial wall, while the palatovaginal canal and artery, the pterygoid canal and artery, and the foramen rotundum and maxillary nerve were shown from the inferiomedial to laterosuperior on the posterior wall. The vomerovaginal canal and artery were located at the slightly superior portion of the medial side of the palatovaginal canal. CONCLUSION: Figures of thin transverse section and multislice spiral CT have highly consistency for the display of PPF. Both of them can correctly identify the micro-structure, the complex relationship of the connectivity and the spatial localization in the narrow space of PPF. It can provide reference gist for the imaging diagnosis and minimal invasive operation.

[Study on angle and depth of needle insertion in acupuncture at Zusanli (ST 36)].

OBJECTIVE: To provide an appropriate angle and depth of needle insertion in acupuncture at Zusanli (ST 36) and avoid injuring the nerve and blood vessel and exert the most effect. METHODS: Eighty adult lower-limb samples were used to dissect and observe the relative layered structures and adjoining important nerves and blood vessels in needling Zusanli (ST 36) according to the national standard. RESULTS: The needling depth from the skin to the interosseous membrane and from the skin to posterior border of tibialis posterior is (2.22 +/- 0.31) cm and (4.42 +/- 0.53) cm, respectively. There are flabellate branches of anterior tibial arteries and deep peroneal nerves around the needle in the superficial layer of interosseous membrane. The vessel and nerve bundles containing tibial nerve and posterior tibial vessels can be touched when the needle body past through tibialis posterior. CONCLUSION: It is recommended that ideal average depth of acupuncture is 2.22 cm and the maximum depth is 4.42 cm for oblique needling Zusanli (ST 36). When it is injected, the needle should be perpendicularly inserted or deviated slightly to the direction of tibia and paralleled to medial surface of tibia. And the safe needling depth is generally less than 5 cm. The point of the body surface between tibialis anterior and extensor digitorum longus at 3 cun below Dubi (ST 35) is also an effectively stimulating point.