A new injection method for identifying the subpopliteal recess of the knee.

The posterolateral region of the knee has a complex and diverse anatomy. Hydrarthrosis of the knee can potentially communicate with other parts of the joint space. The joint fluid distribution reflects anatomical communications between synovial spaces. To observe the continuity between the knee joint cavity and the surrounding bursa, we devised a dissection method with a new injection agent, an eosin-containing congealed liquid that spreads uniformly over the entire space. The purpose of this study was to perform a detailed examination of the subpopliteal recess (SPR) where a bursa connects to the knee joint capsule. We also reported the advantages of this new injection agent compared with conventional materials (latex and epoxy resin). Twenty-two formalin-fixed cadavers (34 knees), two N-vinyl-pyrrolidone (NVP)-fixed cadavers (4 knees), and two cadavers (3 knees) fixed by Thiel's method were used. After filling the knee joint space and SPR with eosin congealed liquid, the specimens were dissected to investigate the morphology of the SPR. In addition, three different types of injection agents were assessed. The SPR extended distally along the popliteus tendon. The SPR length was 22.64 ± 11.38 mm from the upper end of the lateral tibial condyle to the lower end of the depression. The existence of a fabellofibular ligament made the SPR significantly longer, but abrasion of the femoral articular cartilage did not affect the SPR. Furthermore, the relationship between the popliteus muscle and the SPR was classified into three types (types 1-3). Types 2 and 3 in which the SPR extended to the proximal tibiofibular joint may cause instability of the knee joint. The eosin congealed liquid was highly useful in many aspects, such as fluidity and injection workability. The new dissection method with eosin congealed liquid provides insights into the anatomy of the posterior lateral knee, which are useful for radiological diagnoses and clinical treatments.

A histological study of the adult ligamentum arteriosum: Novel findings with application to a patent ductus arteriosus.

The ligamentum arteriosum (LA) is the vestigial fibrous remnant of the ductus arteriosus (DA), a fetal vessel arising from the left dorsal segment of the sixth aortic arch that connects the left pulmonary artery to the aortic arch. Incomplete obliteration of the DA results in a patent ductus arteriosus (PDA), causing the shunting of oxygen-rich blood to recirculate to the lungs, which can lead to pulmonary hypertension. The current study aims to further elucidate the structural characteristics of the LA via histological analysis with data gathered from adult cadaveric specimens. The LA was harvested and histologically observed with Hematoxylin and Eosin, van Gieson, and Masson's trichrome staining. Fibrous and muscle tissues were observed in all 25 specimens. The LA was categorized into three types based on the morphological features of the LA. Type I (vessel-like structure), type II (fibrotic tissue with duct-like structure), and type III (no duct-like structure) were found in 4.0%, 80.0%, and 16.0%, respectively. Finally, the remnant of a valve in the LA was also observed at the junction between the AA and LA. We suggest that this valve be called the "pulmonary-aortic valve." In the majority of the adult LAs, a duct-like structure was still present. These data could better elucidate our understanding of the pathology and etiology of a PDA.

Double Inferior Vena Cava with Major Predominance of the Left Inferior Vena Cava: A Cadaver Case Report.

We encountered a case of a double inferior vena cava with major predominance of the left inferior vena cava during an anatomical dissection course for medical students in 2015. The right inferior vena cava (normal inferior vena cava) was 2.0 mm wide, and the left inferior vena cava was 23.2 mm wide. The fine right inferior vena cava began at the right common iliac vein, ascended along the right side of the abdominal aorta, and then joined the left inferior vena cava at the level of the lower margin of the first lumbar vertebra. The dominant left inferior vena cava started from the left common iliac vein and ascended along the left side of the abdominal aorta. Most patients with a double inferior vena cava are asymptomatic, and these variants are incidentally detected by computed tomography or magnetic resonance imaging. Their presence may have significant implications for surgery, particularly abdominal surgery in patients with paraaortic lymphadenopathy and in those undergoing laparoscopic radical nephrectomy or inferior vena cava filter placement. We herein discuss the embryology of a double inferior vena cava based on detailed anatomical data of the variations of a double inferior vena cava, including those that require clinical attention.

The Key Structure of the Facial Soft Tissue: The Superficial Musculoaponeurotic System.

The superficial musculoaponeurotic system (SMAS) was advocated by Mitz and Peyronie in 1976. The concept of this superficial fascia was established by surgical findings of facelift surgery and is familiar to plastic surgeons and anatomists. However, detailed characteristics of this fascia are still not widely known among head and neck surgeons. Moreover, the SMAS is generally located at the parotid and cheek regions and divides facial fat into superficial and deep layers. The SMAS connects to the superficial temporal fascia cranially and to the platysma caudally. The frontal muscle and the peripheral part of the orbicularis oculi are also in the same plane. The exact expanse of the SMAS in the face is controversial. Some authors claimed that the SMAS exists in the upper lip, whereas others denied the continuity of the SMAS to the superficial temporal fascia in a histological study. There are various other opinions regarding SMAS aside from those mentioned above. The concept of the SMAS is very important for facial soft tissue surgeries because the SMAS is a good surgical landmark to avoid facial nerve injuries. Therefore, this article summarized SMAS from an anatomical point of view.

Anatomical Study of the Atrioventricular Nodal Branch of the Heart.

Background The atrioventricular (AV) node is a relay station for electrical signals passing between the atria and ventricles. The artery supplying the AV node is functionally important, and its anatomical topography is relevant during invasive procedures. Therefore, the aim of this study was to identify and understand the variations of the origin of the AV nodal branch (AVNb) and its variations. Materials and methods We dissected 31 adult human hearts to evaluate their AVNb and its variations. A classification scheme was used to detail the morphology found for each of these arteries. Results We identified five distinct origins of the AVNb: AVNb originating from the right coronary artery (RCA) proximal to the inferior interventricular branch (IVb) (type I, 3.2%), AVNb originating from the junction of the RCA and IVb (type II, 19.4%), AVNb originating from the RCA distal to the IVb (type III, 64.5%), AVNb originating from the IVb (type IV, 6.5%), and AVNb originating from the circumflex branch of the left coronary artery (LCA) (type V, 6.5%). Conclusions Our study provides data on the morphology and variations of the AVNb. Such information can assist in better diagnoses based on imaging, better guide invasive procedures, and provide the cardiac surgeon with an improved method of classifying the AVNb and its branches during procedures of the coronary arteries and their branches.

Gross anatomical study of the subcutaneous structures that create the three-dimensional shape of the buttocks.

The purpose of this study was to clarify the subcutaneous structures involved in the morphology of the gluteal region for clinical application. Thirty-seven formalin-fixed cadavers and one soft-fixed cadaver were used in this study. Gluteal tissue was removed from five formalin-fixed cadavers. A horizontal section and sections parallel to the long axis of the body were made from the excised tissue, and the subcutaneous fat was removed to observe the fibrous structure within the subcutaneous fat. Two formalin-fixed cadavers and one soft-fixed cadaver were used to perform conventional gross anatomical dissection and histological examination. On 30 formalin-fixed cadavers, the thickness of the subcutaneous fat was measured in various areas of the buttocks. The thickness of subcutaneous fat was thicker in the center of the buttocks and thinner on the lateral buttocks. Superficial fascia (SF) was found only in the upper buttock, being indistinct in the lower buttock. In the sacral and coccygeal areas, the dermis was tightly adhered to the bone as a single mass. Fibers arose from around the iliac crest to the SF. On the medial side of the gluteal fold, a strong fiber arose from the sciatic tubercle and inserted into the gluteus maximus and dermis. By identifying the characteristic subcutaneous structures of the gluteal region, we were able to identify the anatomical structures that shape the three-dimensional morphology of the buttocks. These findings may be useful in surgical treatments such as improving the buttock shape.

An Extremely Rare Case of Intestinal Malrotation with an Absent Inferior Vena Cava.

We present a case of intestinal malrotation with an absent inferior vena cava, which was found in a cadaver during a dissection course in our medical school. The intestinal malrotation was Amir-Jahed type 2, with the large intestine on the right side and the small intestine on the left side of the abdominal cavity. The descending colon was fixed on the right side of the posterior abdominal wall and continued into the pelvic cavity from the right side. The cadaver also had a venous system anomaly. The pre-renal segment of the inferior vena cava, which is a section between the renal vein and the hepatic vein, was absent. The inferior vena cava connected to the azygos vein after being joined by bilateral renal veins. The only hepatic segment of the inferior vena cava, which was posterior to the liver and received hepatic veins, penetrated the diaphragm and flowed into the right atrium. To our knowledge, this is the first report of these two anomalies appearing concurrently. We discuss the details of this case and the embryological considerations.

Three sublayers in the SMAS: Observations of facial soft tissue using the stretched tissue dissection method focusing on the SMAS.

The characteristics of the superficial musculoaponeurotic system (SMAS), including the morphology of each part and the connection between tissues, remain controversial. The purpose of this study is to clarify the anatomy of the SMAS using our new dissection method. In this study, six hemi-sides of heads from formalin-preserved cadavers were used. Three were used for creating a horizontal section and three were used for creating the section along the axial line perpendicular to the surface of the skin, resulting in a gradual change from the coronal section at the lateral to the sagittal section at the median. The resected head was cut into slices with widths of 7 mm. The stretched tissue dissection method was performed by fixing a tissue slice to a board and pulling the skin outward to stretch the soft tissue. Blunt dissection was then performed under a microscope. The SMAS comprises three layers: superficial, intermediate, and deep. The superficial layer is a thin membrane directly connecting to the septa in the subcutaneous fat. The deep layer is the connective tissue in contact with the sub-SMAS structure. The layer surrounded by the superficial and deep layer of the SMAS is the intermediate layer, containing connective tissue, adipose tissue, and facial muscles. The detailed findings of the SMAS obtained using this method resolve theoretical discrepancies and provide important insight for the field of facial surgery.

The Lumbar Ligamentum Flavum Does Not Have Two Layers and Is Confluent with the Interspinous Ligament: Anatomical Study with Application to Surgical and Interventional Pain Procedures.

Numerous authors over the years have reported that the lumbar ligamentum flavum has two layers. Our routine cadaveric dissections raised the question whether this understanding is correct, as we always have observed only one layer. Thus, the goal of this cadaveric study was to reevaluate the layers of the ligamentum flavum. Twenty lumbar levels from five fresh-frozen cadaveric specimens were used in this study. After dissection of the lumbar spine, the ligamentum flavum and interspinous ligament were exposed. Each lumbar level was transected through the zygapophyseal joint, and hematoxylin and eosin staining, Masson's trichrome staining and Verhoeff-van Gieson staining were performed. Continuation of the interspinous ligament and ligamentum flavum were observed invariably. There was no evidence of the existence of a two-layered ligamentum flavum. The lumbar ligamentum flavum does not consist of two layers, but is confluent instead with the interspinous ligament that attaches to the zygapophyseal joints. To convey this anatomy better, we suggest describing the lumbar ligamentum flavum as a structure that consists of interlaminar and interspinous parts. Precise knowledge of the ligamentum flavum's anatomy can be of clinical value, particularly when epidural anesthesia or lumbar puncture are performed. Clin. Anat. 32:34-40, 2019. © 2019 Wiley Periodicals, Inc.

A novel method with which to visualize the human sinuatrial node: Application for a better understanding of the gross anatomy of this part of the conduction system.

For various clinical/surgical procedures, it is important to accurately understand the location of the sinuatrial node (SAN). Therefore, this study's goal was to develop a new and simple method to visualize the SAN in human hearts. A total of 16 formalin-fixed human hearts were used in the study. After the epicardium was removed, the fat tissue on the myocardium's surface was brushed and removed in a solution of 40°C water with a surfactant to show the SAN's location. Once the structure considered to be the SAN was observed, histological observation was conducted with Masson's trichrome staining to confirm its identity. The working myocardium, SAN branch of the coronary artery, and the structure believed to be the SAN were observed in all specimens. Histological analysis confirmed this structure to be the SAN. We believe that the method described herein might contribute to a better understanding of the SAN's morphologic features and serve as an improved teaching aide. Clin. Anat. 33:232-236, 2020. © 2019 Wiley Periodicals, Inc.

Bilateral Lateral Costal Branches of the Internal Thoracic Arteries: A Case Report.

We report a case of bilateral lateral costal branches (LCB) of the internal thoracic artery (ITA). On the left side, the ITA branched from the subclavian artery as a common trunk with the thyrocervical trunk. The left LCB flew into the collateral branch of the fifth intercostal artery after reaching the upper end of the sixth rib and after exiting the left ITA at the upper part of the first rib. The left ITA was disconnected near the second rib because it had been used for coronary artery bypass surgery. The right ITA arose from the anterior surface of the right subclavian artery just after the right ITA diverged from the brachiocephalic artery. The right LCB reached the upper end of the fifth rib and flew into the collateral branch of the fourth intercostal artery. The right ITA descended along the back of the costal cartilages as usual. The mechanism of the development of the LCB is thought to be due to a lateral longitudinal anastomosis connecting the inter-node arteries arising from the dorsal aorta during the embryonic phase. More anatomical and embryological studies are necessary to further elucidate this variant arterial branch.

A Retroaortic Left Renal Vein in a Female Cadaver.

We encountered a case of retroaortic left renal vein (RLRV) during an anatomical dissection course at our medical school in 2017. The case was a female cadaver who was 88 years old at death. Six roots of the left renal vein (RV) arose from the hilus of the kidney and joined to form one left renal vein, crossed dorsal to the abdominal aorta (AA) at the level of the second lumbar vertebra, and then drained into the inferior vena cava (IVC). Two roots joined at the right renal hilus to become the right RV to then drain into the IVC at the level of the first lumbar vertebral body. The reported frequency of RLRV is approximately 2%. Embryologically, the normal anastomosis of the left and right sub-cardinal veins results in the left RV traveling on the ventral surface of the AA. However, in the case presented here, the left RV traveled on the dorsal side of the AA due to the anastomosis of the left and right supra-cardinal veins and regression of the anastomosis between the left and right sub-cardinal veins. If both the dorsal and ventral anastomoses remain, the left RV travels on the dorsal and ventral sides of the aorta. Some of the clinical problems reported in association with RLRV are hematuria and abdominal pain, and the risk of damaging the RLRV during surgery of the posterior abdominal wall. Venous variants as reported herein should be kept in mind when interpreting imaging of the posterior abdominal wall or performing surgery or other invasive procedures near the RLRV.

A Case of Duplicated Right Vertebral Artery.

We encountered a case of duplicated right vertebral artery during an anatomical dissection course for medical students in 2015. Two vertebral arteries were found in the right neck of a 91-year-old female cadaver. The proximal leg of the arteries arose from the area between the right subclavian artery and the right common carotid artery that diverged from the brachiocephalic artery. The distal leg arose from the right subclavian artery as expected. The proximal leg entered the transverse foramen of the fourth cervical vertebra and the distal leg entered the transverse foramen of the sixth cervical vertebra. The two right vertebral arteries joined to form one artery just after the origin of the right vertebral artery of the brachiocephalic artery entered the transverse foramen of the fourth cervical vertebra. This artery then traveled up in the transverse foramina and became the basilar artery, joining with the left vertebral artery. We discuss the embryological origin of this case and review previously reported cases.

Anatomical and Radiological Analyses of L-shaped Kidney with Vascular Anomalies.

L-shaped kidney is a congenital anomaly. The disorder results in the kidney appearing very similar in shape to horseshoe kidney (also a congenital anomaly), but either the right or left kidney is located at a position lower than the other kidney. In this report, we describe a woman with L-shaped kidney, identified during anatomical dissection, and compare the findings with clinical data obtained before her death. We discuss the embryology of L-shaped kidney based on detailed anatomical data on the kidney and its vascular system obtained by means of gross anatomical, radiological, and histological examinations. Our findings indicate the importance of detailed anatomical information when planning surgical procedures in patients with fused kidneys, as well as kidney transplantation, resection of renal carcinoma, or surgical treatment of abdominal aortic aneurysm.

Novel Cadaver Injection Method Using Latex and Magnetic Fluid.

Vascular injection into extracted tissue may be associated with leakage due to excessive local injection pressure. Historically, this complication has been impossible to resolve because the injection pressure has been the only available force with which to send the agent to the peripheral vasculature. We have developed a new vascular injection method that utilizes a material affected by magnetic force and is therefore not solely dependent upon the injection pressure. We mixed the same weights of latex and magnetic fluid and injected the solution into the arterial stump of an extracted tissue specimen. Next, we used a permanent magnet to attract the agent into the peripheral vasculature. We repeated the injection and magnetic application until no further fluid could be injected. We used this method in 20 formalin-fixed tissue specimens. The vessels were clearly observable through to the peripheral areas, and leakage from the injected artery was minimal. This new agent has several beneficial characteristics: it is X-ray impermeable, is durable in the face of chemical insult, and allows for easy visual observation. The injected tissue can be studied for X-ray film examination, tissue clarification, and gross anatomical dissection. Additionally, this method can be applied to both fresh and formalin-fixed tissue. We consider that this method has the potential to expand the applications of injection studies.

Direct Insertion of the Papillary Muscle into the Anterior Mitral Leaflet: Cadaveric Findings.

Direct insertion of the anterior papillary muscle (DPM) into the mitral valve is uncommon. During the routine dissection of an adult female, a DPM into the mitral valve with abnormal chordae tendinae was observed. This abnormal papillary muscle was measured as 28.0 mm in length from myocardial to insertion, 14.8 mm in width, and 7.0 mm in depth. The embryology, symptoms, associated cardiac diseases, and surgical precautions of this congenital malformation in the heart are reviewed.

A Novel Method for Observation of the Mandibular Foramen: Application to a Better Understanding of Dental Anatomy.

Cone-beam computed tomography gives us much useful morphological information about the mandibular bone. Many studies of the mandible include findings from this technique. However, there have been no endoscopic studies of the mandible. Sixteen sides of eight dry mandibles resected from cadavers (age range 38-83 years) were examined by endoscopy. The head of the endoscope was 2.0 mm in diameter. We examined the mandibular foramen, lingula, mylohyoid groove, and mandibular canal. The mylohyoid grooves showed variations such as double grooves and canals. The mandibular lingula was located superior or medial to the the mandibular foramen. In a single case, the medial wall inside the mandibular canal showed a porous surface. The retromolar canal was observed in three sides. None of the images in the present study have been seen in other studies. Observation of the retromolar canal from the mandibular canal in particular can help dental students as well as oral and maxillofacial surgeons to understand its morphology. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:1875-1880, 2017. © 2017 Wiley Periodicals, Inc.

Undetected Small Accessory Mental Foramina Using Cone-Beam Computed Tomography.

INTRODUCTION: The accessory foramina could not be identified on some imaging modalities such as surface-rendered images. The purpose of this study was to investigate the ability of surface-rendered images in detecting these foramina. MATERIALS AND METHODS: We analyzed 20 accessory mental foramina (AMF) in nine mandibles removed from cadavers with cone-beam computed tomography (CBCT) and assessed in surface-rendered images. All AMF were divided into three groups depending on their visibility. RESULTS: Group 1 included AMF that were clearly visible as foramina, Group 2 were not clearly visible but could be recognized with concave parts, and Group 3 were not visible and the smooth surface of the bone was observed. Group 1 ranged from 1.3 to 5.1 mm2, Group 2 from 0.3 to 3.8 mm2, and Group 3 from 0.2 to 1.1 mm2. A statistically significant difference in the mean size between Groups 1 and 3 was observed. Even if the AMF are smaller (e.g., 1 mm in diameter), they should still be avoided to prevent injury. CONCLUSIONS: The clinician should be aware that smaller foramina might not be detected on these images.

Aortic arch origin of the left vertebral artery: An Anatomical and Radiological Study with Significance for Avoiding Complications with Anterior Approaches to the Cervical Spine.

Complications from anterior approaches to the cervical spine are uncommon with normal anatomy. However, variant anatomy might predispose one to an increased incidence of injury during such procedures. We hypothesized that left vertebral arteries that arise from the aortic arch instead of the subclavian artery might take a more medial path in their ascent making them more susceptible to iatrogenic injury. Fifty human adult cadavers were examined for left vertebral arteries having an aortic arch origin and these were dissected along their entire cervical course. Additionally, two radiological databases of CTA and arteriography procedures were retrospectively examined for cases of aberrant left vertebral artery origin from the aortic arch over a two-year period. Two cadaveric specimens (4%) were found to have a left vertebral artery arising from the aortic arch. The retrospective radiological database analysis identified 13 cases (0.87%) of left vertebral artery origin from the aortic arch. Of all cases, vertebral arteries that arose from the aortic arch were much more likely to not only have a more medial course (especially their preforaminal segment) over the cervical vertebral bodies but also to enter a transverse foramen that was more cranially located than the normal C6 entrance of the vertebral artery. Spine surgeons who approach the anterior cervical spine should be aware that an aortic origin of the left vertebral artery is likely to be closer to the midline and less protected above the C6 vertebral level. Clin. Anat. 30:811-816, 2017. © 2017Wiley Periodicals, Inc.

Radiological and Microsurgical Anatomy for Variation of the Mandible: Comparative Study of Human and Macaca fascicularis.

Recent studies using cone-beam computer tomography (CBCT) have added to our understanding of anatomical variation in the mandible of humans. However, the distribution of nerves cannot be revealed by CBCT. There have been investigations of the distribution of nerves relating to the mandible, but some proposed causes of these variations remain controversial. In this study, we observed a total of 10 sides from five mandibles of Macaca fascicularis of unknown age and sex using CBCT and dissection under stereomicroscopy. Nine of the 10 sides had two mental foramina in each side. Innervation by the mental nerves depended on the locations of those foramina. The long branch to the mandibular angle ran with a branch of the facial artery, which joined the mental artery in all 10 sides. Five specimens had a median perforating canal in the mandibular bone. In addition, a branch of the sublingual artery, which joined with the small branches of the submental artery, entered the mandibular bone from the median lingual foramen. This foramen was located in the lower part of the mandibular symphysis and passed via the median perforating canal to exit from the median labial foramen, also located in the lower part of the mandibular symphysis. We speculate that the median perforating canal of the mandible, rarely found in humans, is the remnant of the feeding artery of the fetal mandible, and in M. fascicularis is seen in all specimens because they have no mental protuberance. Anat Rec, 300:1464-1471, 2017. © 2017 Wiley Periodicals, Inc.