Implementation of 3D printed superior mesenteric vascular models for surgical planning and/or navigation in right colectomy with extended D3 mesenterectomy: comparison of virtual and physical models to the anatomy found at surgery.

BACKGROUND: Three-dimensional (3D) printing technology has recently been well approved as an emerging technology in various fields of medical education and practice; e.g., there are numerous studies evaluating 3D printouts of solid organs. Complex surgery such as extended mesenterectomy imposes a need to analyze also the accuracy of 3D printouts of more mobile and complex structures like the diversity of vascular arborization within the central mesentery. The objective of this study was to evaluate the linear dimensional anatomy landmark differences of the superior mesenteric artery and vein between (1) 3D virtual models, (2) 3D printouts, and (3) peroperative measurements. METHODS: The study included 22 patients from the ongoing prospective multicenter trial "Safe Radical D3 Right Hemicolectomy for Cancer through Preoperative Biphasic MDCT Angiography," with preoperative CT and peroperative measurements. The patients were operated in Norway between January 2016 and 2017. Their CT datasets underwent 3D volume rendering and segmentation, and the virtual 3D model produced was then exported for stereolithography 3D printing. RESULTS: Four parameters were measured: distance between the origins of the ileocolic and the middle colic artery, distance between the termination of the gastrocolic trunk and the ileocolic vein, and the calibers of the middle colic and ileocolic arteries. The inter-arterial distance has proven a strong correlation between all the three modalities implied (Pearson's coefficient 0.968, 0.956, 0.779, respectively), while inter-venous distances showed a weak correlation between peroperative measurements and both virtual and physical models. CONCLUSION: This study showed acceptable dimensional inter-arterial correlations between 3D printed models, 3D virtual models and authentic soft tissue anatomy of the central mesenteric vessels, and weaker inter-venous correlations between all the models, reflecting the highly variable nature of veins in situ.

Retromesenteric course of the middle colic artery-challenges and pitfalls in D3 right colectomy for cancer.

BACKGROUND: The middle colic artery (MCA) is of crucial importance in abdominal surgery, for laparoscopic or open right and transverse colectomies. Against this background, a high number of reports concerning anatomical variations of the MCA have been published intended to contribute to the improvement of operative techniques for the treatment of colon cancer. Despite this extensive literature, briefly reviewed in the present paper, a course of the MCA posterior to the superior mesenteric vein, called a retromesenteric trajectory, has been related to only once, to the best of our knowledge. METHODS: A total series of 507 patients included in two prospective trials concerning laparoscopic or open right colectomy for cancer between 2011 and 2017 are reported. The investigation included preoperative or postoperative multidetector-computed tomography angiography. RESULTS: We found four (0.79%) cases of retromesenteric MCA. They all underwent meticulous image analysis with mesenteric vessels' road mapping, detailed morphometry, and surgical validation which revealed that, apart from their course, those cases did not differ significantly from the rest of the series. CONCLUSION: This paper therefore documents the worth-knowing behavior causing considerable confusion for the operating surgeon unaware of the abnormality and shows its concrete impact on patient-tailored surgical practice, in particular for laparoscopic D3 colectomy (including the "uncinated process first" approach).

Additional muscular slip of the flexor digitorum longus muscle to the fifth toe.

Despite the fact that there are numerous reports on muscular variations in the sole of the foot, routine dissection in a formaldehyde-fixed cadaver revealed an accessory flexor digiti quinti muscle, which to the best of our knowledge is a very unusual variant. This was in the form of a slender, 38 mm long muscular slip, with a proximal and distal tendon extending from the common flexor digitorum longus tendinous plate out to the distal phalanx of the fifth toe. An associated finding was the absence of the musculotendinous portion of the flexor digitorum brevis to the same toe. A developmental explanation for this variation is presented. Clinical implications with regard to this anatomical condition may result in clawing of the fifth toe.

Endoscopic Transcranial Duraplasty for Rhinoliquorrhea: A Cadaveric Study.

BACKGROUND: Repair of the anterior skull base for cerebrospinal fluid leak requires either endoscopic endonasal approach or open transcranial approach. OBJECTIVE: To present a less invasive surgical procedure for sealing of the entire anterior fossa floor for traumatic rhinoliquorrhea. METHODS: Cadaver study in 3 head specimens. Endoscopic placement of a furled bovine pericardial patch bilaterally along the sphenoid ridge and planum in guidewire technique. Unfurling and spreading of the patch under endoscope assistance. RESULTS: Patch placement was feasible in all 3 specimens without visible injuries to the frontal lobes. Dissection and preservation of the olfactory tracts was only possible for 50% of olfactory tracts. CONCLUSION: Endoscopic transcranial keyhole duraplasty is a promising concept for traumatic rhinoliquorrhea.

Planimetric correlation between the submandibular glands and the pancreas: a postmortem ductographic study.

The salivary glands and pancreas have comparable anatomic and antigenic properties and can share common pathogenetic mechanisms involving toxic or autoimmune processes. The aim of this study is to assess the correlation in size between the normal submandibular glands and the pancreas. The study was based on human autopsy specimens of the pancreas, neck and oral base from 22 adults, both sexes (mean age, 57.9 years). The pancreatic and submandibular ducts were injected with a contrast medium, and the area of the salivary and pancreatic glandular ductograms was measured with the aid of software for quantification of visual information. Samples of tissue from the salivary glands and the pancreas were studied by means of light microscopy. A high correlation was found between the planimetric size of the pancreas and the submandibular glands (correlation coefficient 0.497 and 0.699 for the right and the left gland, respectively). This ratio was close to 5:1. There were no significant differences in size for the left vs. right submandibular gland (p = 0.39). The ductograms were significantly larger in size in males than in females (p < 0.001). This study has proven a positive correlation in planimetric size between the normal submandibular glands and pancreas, a result that is expected to have possible clinical implications in the long-term follow-up of patients with chronic pancreatitis.

Surgical Training for the Implantation of Neocortical Microelectrode Arrays Using a Formaldehyde-fixed Human Cadaver Model.

This protocol describes a procedure to assist surgeons in training for the implantation of microelectrode arrays into the neocortex of the human brain. Recent technological progress has enabled the fabrication of microelectrode arrays that allow recording the activity of multiple individual neurons in the neocortex of the human brain. These arrays have the potential to bring unique insight onto the neuronal correlates of cerebral function in health and disease. Furthermore, the identification and decoding of volitional neuronal activity opens the possibility to establish brain-computer interfaces, and thus might help restore lost neurological functions. The implantation of neocortical microelectrode arrays is an invasive procedure requiring a supra-centimetric craniotomy and the exposure of the cortical surface; thus, the procedure must be performed by an adequately trained neurosurgeon. In order to provide an opportunity for surgical training, we designed a procedure based on a human cadaver model. The use of a formaldehyde-fixed human cadaver bypasses the practical, ethical and financial difficulties of surgical practice on animals (especially non-human primates) while preserving the macroscopic structure of the head, skull, meninges and cerebral surface and allowing realistic, operating room-like positioning and instrumentation. Furthermore, the use of a human cadaver is closer to clinical daily practice than any non-human model. The major drawbacks of the cadaveric simulation are the absence of cerebral pulsation and of blood and cerebrospinal fluid circulation. We suggest that a formaldehyde-fixed human cadaver model is an adequate, practical and cost-effective approach to ensure proper surgical training before implanting microelectrode arrays in the living human neocortex.

Human liver territories: Think beyond the 8-segments scheme.

Worldwide, compartmentalization of the human liver into portal venous territories today follows the eight-segments scheme credited to Couinaud. However, there are increasing reports of anatomical, radiological and surgical observations that contradict this concept. This paper presents a viewpoint that enhances understanding of these inconsistencies and can serve as a basis for customized liver interventions. Clin. Anat. 30:974-977, 2017. © 2017 Wiley Periodicals, Inc.

Quantification of Working Volumes, Exposure, and Target-Specific Maneuverability of the Pterional Craniotomy and Its Minimally Invasive Variants.

OBJECTIVE: Quantitative comparison of minimally invasive and standard cranial approaches remains a methodologic challenge. The aim of this study was to apply a new digital, navigation-based method to quantify multiple parameters of the pterional, supraorbital, lateral supraorbital and mini-pterional approaches and to describe a target-specific maneuverability score. METHODS: Supraorbital, lateral supraorbital, mini-pterional, and standard pterional craniotomies were performed on 8 sides in 4 cadaver heads. The limits of superficial and deep exposure and surgical target points were registered with image-guidance (Medtronic Stealth). A custom software (Guided Therapeutics Eyes II Software [GTxEyesII]) calculated superficial and deep surface areas, working volumes, and target distances. Volumes were reconstructed digitally and visualized with GTxEyesII. Finally, we defined for each approach a target-specific maneuverability score based on surface exposure, target distance, target position, and anatomical obstacles. RESULTS: Surface exposure and volumes were significantly smaller for keyhole approaches compared with standard pterional craniotomy (P < 0.01). Maneuverability index scores showed the greatest values for standard pterional craniotomies, but nearly equally high scores could be achieved by one or several of the less-invasive approaches for most of the targets. CONCLUSIONS: The combination of a navigation-based measurement method with custom software (GTxEyesII) provides a powerful tool for visualization and quantification of surgical approaches. Compared with standard pterional craniotomy, alternative keyhole craniotomies offer comparable deep exposure with smaller working volumes and relatively high maneuverability for specific targets.

Syndesmosis reduction by computer-assisted orthopaedic surgery with navigation: Feasibility and accuracy in a cadaveric study.

INTRODUCTION: Syndesmotic disruption may be difficult to reduce and fix, and malreduction is associated with inferior outcomes. Intraoperative computed tomography (CT) can provide accurate assessment of syndesmotic reduction. We hypothesized that three-dimensional (3-D) computer-assisted orthopaedic surgery (CAOS) with navigation of syndesmotic reduction could avoid malreduction. Our goal was to assess feasibility and accuracy of such a technic in a cadaveric study. METHOD: Eleven through-the-knee cadaveric specimens were used. Ankle CT as control was obtained prior to intervention. The syndesmosis was destabilized by sectioning the tibiofibular ligaments, producing a malreduction temporarily fixed with a Kirschner wire (K-wire). With reference base fixed to the tibia an acquisition scan was made. A K-wire was fixed to the fibula. The K-wire holding the syndesmosis malreduced was removed. The fibula was reduced within the syndesmosis under 3-D CAOS using a navigated K-wire. Once optimal position was obtained by referencing control images, the syndesmosis was fixed with a 3.5mm screw. A CT scan was performed to assess quality of reduction. RESULTS: Position of the fibula in control and post-reduction CT scans showed a mean anterior-posterior displacement of 0.74 (±0.62)mm. The medial-lateral position measured a mean displacement of 0.68 (±0.76)mm. Rotation of the fibula revealed a mean difference of 0.99° (± 0.73). CONCLUSION: In this cadaveric study, CAOS with navigation allowed for very accurate syndesmosis reduction. This appears to be a promising technique to be confirmed by clinical study.

Adapting anatomy teaching to surgical trends: a combination of classical dissection, medical imaging, and 3D-printing technologies.

PURPOSE: Many regions worldwide report difficulties in recruiting applicants to surgery. One strategy proposed to reverse this trend consists of early exposure of medical students to the field. Against this backdrop, the present study presents an innovative approach for anatomy teaching, integrating a surgically relevant trend: 3D printing. METHODS: Whole-body computed tomography (CT) was made of two cadavers. Twelve students performed measurements and 3D reconstructions of selected anatomical structures (Osirix, Mimics). 3D printed (3DP) models were obtained (ZPrinter 310 Plus), and the students completed the analogous measurements on these replicas. Finally, classical anatomical dissection was performed and the same parameters were measured. The differences between the values obtained by the three modalities were submitted to standard statistical analysis (Wilcoxon two-tail paired test). RESULTS: Qualitative comparison of the digital 3D reconstructions based on the students' manual CT segmentation and the anatomical reality showed excellent correlation. Quantitatively, the values measured on the CT images and the physical models created by 3D printing differed from those measured on the cadavers by less than 2 mm. Students were highly appreciative of the approach (CT, 3DP, cadaver). Their average satisfaction score was 5.8 on a 1-6 scale. CONCLUSIONS: This study shows that the approach proposed can be achieved. The results obtained also show that CT-based 3D printed models are close to the authentic anatomic reality. The program allows early and interactive exposure of medical students to a surgically relevant trend-in this case 3D printing.

Evaluating Preoperative Models: A Methodologic Contribution.

BACKGROUND: Three-dimensional (3D) printed models of the human skull and parts of it are being increasingly used for surgical education and customized preoperative planning. OBJECTIVE: This study, using the calvaria as a model, provides a methodologic analysis with regard to future investigations aimed at evaluating patient-specific skull replicas. METHODS: Postmortem computed tomography was used for 3D reconstruction of a skull. The digital model obtained was converted to a physical replica by 3D printing. This copy was compared qualitatively and quantitatively with the original, using both a classical anthropometric and a 3D surface scanning approach. RESULTS: Qualitatively, the replica and the original displayed good qualitative concordance. The quantitative deviations, as measured by osteometric tools, lay partly in the submillimetric area, partly between 1 and 2 mm. The maximum difference was 3.7 mm. On the basis of the surface scans, a mean deviation of 0.2930 mm (±0.2677 mm) and a median difference of 0.2125 mm (0.0000-1.5509 mm) were observed for the inner surface. For the whole object, corresponding figures amounted to 0.9101 mm (±0.5390 mm) and 0.8851 mm (0.000-3.2647 mm). CONCLUSIONS: Qualitatively flawless replicas of the skull region investigated are feasible, subject to extensive manual CT image editing. However, neurosurgeons should be aware that models of one and the same patient will vary according to the production chain used by the 3D printing laboratory in charge. Methodologically, both classic anthropological and light-stripe-based comparisons are justified for use in future studies. For trials aimed at assessing mean deviations and topographic distribution patterns, optical 3D scanning technologies can be recommended.

Repair of Large Abdominal Wall Defects Using Total Anterior Aponeurotic Flap: Anatomical Feasibility Study and Comparison with Ramirez's Technique.

In this cadaveric study, we explored the feasibility of a maximal mobilization of the superficial abdominal fascia, in a continuous flap, to achieve a tension-free covering of midline defects. The aponeurosis of the external oblique muscle was incised along the anterior axillary line and then detached up to the anterior rectus sheath. The latter was opened between the external and the internal oblique aponeurosis while keeping the continuity with the external oblique fascia. The obtained flap was solid and uninterrupted. The width gain reached 15 ± 3 cm on each sides, providing tissue advancement 60% longer than Ramirez's technique (n = 8). The described technique allows large covering with respect to the anatomical planes. Further clinical tests should evaluate the validity of such concept in the repair of giant and asymmetrical hernias.

Scapular Notching on Kinematic Simulated Range of Motion After Reverse Shoulder Arthroplasty Is Not the Result of Impingement in Adduction.

Impingement after reverse shoulder arthroplasty (RSA) is believed to occur from repetitive contact in adduction between the humeral component and the inferior scapular pillar. The primary purpose of this biomechanical study was to confirm the presence of different types of impingement and to examine which daily-life movements are responsible for them. A secondary aim was to provide recommendations on the type of components that would best minimize notching and loss of range of motion (ROM). The study included 12 fresh frozen shoulder specimens; each had a computed tomography (CT) image of the entire scapula and humerus in order to acquire topological information of the bones before RSA implantation. Cyclic tests were run postimplantation with 3 shoulders in each modalities. To quantify bone loss due to impingement, 3-dimensional anatomical models of the scapula were reconstructed from the CT scans and compared to their intact states. We found 8 bony impingements in 7 specimens: 2 at the lateral acromion, 1 at the inferior acromion, 4 scapular notching, and 1 with the glenoid resulting to wear at the 3:00 to 6:00 clock-face position. Impingements occurred in all kinds of tested motions, except for the internal/external rotation at 90° of abduction. The 3 specimens tested in abduction/adduction presented bone loss on the acromion side only. Scapular notching was noted in flexion/extension and in internal/external rotation at 0° of abduction. The humeral polyethylene liner was worn in 2 specimens--1 at the 6:00 to 8:00 clock-face position during internal/external rotation at 0° of abduction and 1 at the 4:00 clock-face position during flexion/extension. The present study revealed that 2 types of impingement interactions coexist and correspond to a frank abutment or lead to a scapular notching (friction-type impingement). Scapular notching seems to be caused by more movements or combination of movements than previously considered, and in particular by movements of flexion/extension and internal/external rotation with the arm at the side. Polyethylene cups with a notch between 3 and 9 o'clock and lower neck-shaft angle (145° or 135°) may play an important role in postoperative ROM limiting scapular notching.

Accuracy evaluation of CAD/CAM generated splints in orthognathic surgery: a cadaveric study.

INTRODUCTION: To evaluate the accuracy of CAD/CAM generated splints in orthognathic surgery by comparing planned versus actual post-operative 3D images. METHODS: Specific planning software (SimPlant(®) OMS Standalone 14.0) was used to perform a 3D virtual Le Fort I osteotomy in 10 fresh human cadaver heads. Stereolithographic splints were then generated and used during the surgical procedure to reposition the maxilla according to the planned position. Pre-operative planned and postoperative 3D CT scan images were fused and imported to dedicated software (MATLAB(®)) 7.11.) for calculating the translational and rotational (pitch, roll and yaw) differences between the two 3D images. Geometrical accuracy was estimated using the Root Mean Square Deviations (RMSD) and lower and upper limits of accuracy were computed using the Bland & Altman method, with 95 % confidence intervals around the limits. The accuracy cutoff was set at +/- 2 mm for translational and ≤ 4° for rotational measurements. RESULTS: Overall accuracy between the two 3D images was within the accuracy cutoff for all values except for the antero-posterior positioning of the maxilla (2.17 mm). The translational and rotational differences due to the splint were all within the accuracy cutoff. However, the width of the limits of agreement (range between lower and upper limits) showed that rotational differences could be particularly large. CONCLUSION: This study demonstrated that maxillary repositioning can be accurately approximated and thus predicted by specific computational planning and CAD/CAM generated splints in orthognathic surgery. Further study should focus on the risk factors for inaccurate prediction.

Pathways of cerebrospinal fluid outflow: a deeper understanding of resorption.

INTRODUCTION: Cerebrospinal fluid (CSF) absorption has long been held to predominantly entail drainage into the venous outflow system via the intracranial arachnoid granulations. Newer data suggest pathways involving spinal arachnoid granulations and lymphatic channels may also make substantial contributions to CSF outflow. METHODS: The putative major CSF outflow pathways and their proportionate contribution to CSF absorption were reviewed in this article. RESULTS: CSF is absorbed and drained in bulk not just through cerebral arachnoid granulations (CAG) but also through spinal arachnoid granulations (SAG) and a lymphatic pathway involving egress through cranial and spinal nerve sheaths. The proportions of CSF that efflux through each of these major pathways have yet to be determined with any certainty in humans, though existing evidence (the majority of which is derived from animal studies) suggests that lymphatic pathways may account for up to 50% of CSF outflow-presumably leaving the CAG and SAG to process the balance. CONCLUSION: Knowledge of the CSF pathways holds implications for our ability to understand, prognose, and even treat diseases related to CSF circulation and so is a matter of considerable relevance to neuroradiology and neurology.

A modified posteromedial approach combined with extensile anterior for the treatment of complex tibial pilon fractures (AO/OTA 43-C).

The anterior approaches that have been described for open reduction internal fixation of multifragmentary pilon fractures are designed to reconstruct the comminuted and impacted anterior articular surface onto a stable posterior column. Thus, reduction of the posterior column, particularly proper length, is critical. There are differing opinions of how best to surgically approach the posterior pilon fracture. There is also no clear indication as to the timing of both anterior and posterior reconstructions. Our objectives were (1) to develop a more midline posterior approach that might provide better visualization of the posterior aspect of the posterior column and juxtametaphyseal/diaphyseal parts of the tibia, first on the cadaver and then with patients, and (2) to use this as part of a combined posterior and anterior approach during the same anesthesia for complex tibial pilon fractures (AO/OTA 43-C) in a preliminary study of 6 patients.

Teaching Clinical Anatomy: from general practice to state-of-the-art surgery

The amount of time allocated to teaching gross anatomy within medical curricula has been drastically curtailed worldwide. There is thus a need for core syllabi detailing the level of knowledge all medical students should reach. Against this background, the present study was aimed at determining a compulsory core of anatomical knowledge relevant for non-specialised, i.e. general medical practice. The design of the study was a modified Delphi consensus approach - i.e., a survey relied on a panel of independent experts. 7 general practitioners of high professional profile were asked to identify, in an exhaustive list of the structures included in the current international anatomical terminology, those elements which they considered to be indispensable for their practice. This paper presents the results concerning the digestive tract, with special emphasis on the liver. The current anatomical nomenclature names 499 structures under the alimentary system. Out of these, 442 were judged unanimously. This corresponds to a consensus of opinion in 88.6 %. 148 (29.7%) have been settled as indispensable for general medical practice. Based on these results, a 3-level-strategy for teaching anatomy has been implemented. Its main features are briefly described in the paper

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Anatomy of the liver: an outline with three levels of complexity--a further step towards tailored territorial liver resections.

The vascular anatomy of the liver can be described at three different levels of complexity according to the use that the description has to serve. The first--conventional--level corresponds to the traditional 8-segments scheme of Couinaud and serves as a common language between clinicians from different specialties to describe the location of focal hepatic lesions. The second--surgical--level, to be applied to anatomical liver resections and transplantations, takes into account the real branching of the major portal pedicles and of the hepatic veins. Radiological and surgical techniques exist nowadays to make full use of this anatomy, but this requires accepting that the Couinaud scheme is a simplification, and looking at the vascular architecture with an unprejudiced eye. The third--academic--level of complexity concerns the anatomist, and the need to offer a systematization that resolves the apparent contradictions between anatomical literature, radiological imaging, and surgical practice. Based on the real number of second-order portal branches that, although variable averages 20, we submit a system called the "1-2-20 concept", and suggest that it fits best the number of actual--as opposed to idealized--anatomical liver segments.