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Potential asymmetries of the C2 posterior elements pose a problem for the spine surgeon seeking to make the best choice for spinal stabilization while reducing morbidity.A digital caliper was used to measure the pars interarticularis height and length on left and right sides of 25 adult C2 vertebrae. The pars interarticularis was defined as the bone between the posterior most aspect of the superior articular process and the anterior most aspect of the inferior articular process of C2. Also, the C2 vertebrae from 49 patients were scanned by CT. Parasagittal images were reviewed and using the same definitions as were used for the skeletal specimens, the length and the height of the C2 pars interarticularis from both the left and right sides were measured using CT. The image slices were acquired at 3 mm intervals. The pars interarticularis height was determined on sagittal CT reconstruction, while the pars interarticularis length was calculated on the basis of the axial images.The lengths and the heights of the left and right pars interarticularis were compared using CTs of patients and skeletal specimens. No significant differences were found in the length and height measurements of the CT images on both sides. However, in the skeletal specimens, the left and right pars interarticularis did not differ significantly in length but differed significantly in height (p = 0.003). The mean height of the left pars interarticularis was approximately two times larger than the right in the skeletal specimens. Absolute differences were calculated between the side with the greater length and height and the side with the lesser length and height irrespective of their left-right orientations. For CT measurements, most differences in length and height between the greater pars interarticularis and lesser pars interarticularis occurred between 0 and 1 mm with each successive disparity interval yielding lower numbers. Skeletal measurements revealed a similar length disparity distribution to the CT measurements. However, height measurements in the skeletal specimens varied widely. Eight pars interarticularis specimens demonstrated a height difference between 0 and 1 mm. No dry bone pars interarticularis specimens demonstrated a height difference between 1 and 2 mm. The pars interarticularis of nine specimens demonstrated a height difference between 2 and 3 mm. Two demonstrated a height difference between 3 and 4 mm. Four demonstrated a height difference between 4 and 5 mm and two demonstrated a height difference greater than 5 mm. The greater pars interarticularis lengths and heights were combined and compared to their lesser counterparts on CT and skeletal measurements. In all measurements of this type, significant differences were found in the pars interarticularis length and height, whether measured through CT or via digital calipers.Asymmetry between the left and right C2 pars interarticularis as shown in the present study can alter surgical planning. Therefore, knowledge of this anatomical finding might be useful to spine surgeons.

The submental artery usually runs anteriorly on the inferior surface of the mylohyoid muscle, giving branches to that muscle and to the anterior belly of the digastric muscle, finally supplying the submental skin. Branches of it often perforate the mylohyoid muscle and enter the sublingual space. During a routine anatomy dissection, we encountered a case in which the main trunk of the submental artery perforated the mylohyoid muscle, where the sublingual artery usually runs. No branches coursed anteriorly to supply the submental skin. To our knowledge, this submental artery variation has not been reported in the English literature. Any surgical procedure in the submandibular area, such as the axial pattern submental local flap, requires knowledge of such arterial variations.

In this study, we aimed to reveal the detailed anatomy of mental nerve branches to the inferior labial glands. Embalmed cadaveric heads were used in this study and the mental nerve branches to the inferior labial glands were dissected. Branches to the glands were then excised for histological observation. On all sides, the inferior labial glands were innervated by small branches arising from mental nerve branches that innervated the lower lip. No nerve branches to the inferior labial gland crossed the midline. Histological observation found that the tissue to the inferior labial gland were composed primarily of nerve fibers with a small number of surrounding vessels. Histological findings in examined specimens were consistent. The inferior labial glands were innervated by small branches of the mental nerve to the lower lip.

Many anatomical variations of the superficial veins of the head and neck have been reported throughout the literature. Accordingly, anatomists and surgeons must have a comprehensive understanding of these variations to avoid confusion. Duplication of the external jugular vein (EJV) is occasionally observed during routine cadaveric dissections; however, this variation seems to be reported less often than actual experience suggests. Therefore, to gain a better understanding of its anatomical and clinical implications, an analysis of the available data should be available. Thus, in this article, we reviewed the current available literature for studies reporting duplication of the EJV. We conducted a search using PubMed and Google Scholar with the following keywords: “duplication of the external jugular vein,” “division of the external jugular vein,” and “fenestration of the external jugular vein,” “double external jugular vein,” and “doubled external jugular vein.” As a case illustration, we also describe a case of a duplicated EJV found during a right neck dissection of a female cadaver. Twenty sides across sixteen different studies were analyzed including the present case. All studies were published between 2009 and 2020. EJV division patterns were classified as either duplication, fenestration, fenestration followed by duplication, or double fenestrations. We have reviewed the literature regarding cases documenting duplication/fenestration of the EJV. As it is often difficult to find recent studies that report on classic anatomical variations, therefore, revisiting older articles and textbooks is necessary for achieving a “comprehensive” review, especially across different languages.

The anatomical variations of the mandibular canal have been described according to the number of additional branches it presents, bifid and trifid. Within the bifids we can also find subtypes of variations such as the retromolar mandibular canal. These anatomical variations can have important clinical implications for the work of dental professionals.A systematic search of the literature was carried out in different databases that met the following criteria: articles published between 2000 and 2020, and articles that established a clinical correlation with variations in the mandibular canal.After applying inclusion and exclusion criteria, 32 articles were obtained, in which the variations of the mandibular canal were identified, their prevalence and incidence, which was very varied between the different articles, it was also found that the CBCT was the main technique to identify the anatomical variations of the mandibular canal. Lastly, the anatomical variations of the mandibular canal have a direct clinical correlation with pre-surgical, intra-surgical and postsurgical complications in pathologies that require surgical intervention.The anatomical variations of the mandibular canal have a high incidence, so knowing them is of vital importance both for clinicians and anatomy professors who provide morphological training. We believe that research should focus on describing and diagnosing the causes of these anatomical variations. That said, there is also a continuous challenge for all health professionals to learn about the different anatomical variations that the human body presents and how these can affect clinical practice.

The term "sagittal cleft vertebra" (SCV) denotes a rare embryologically derived longitudinal defect within the vertebral body, which is clinically and radiologically challenging to diagnose in isolation. This defect results in two hemivertebrae, which ossify discordantly, ultimately leading to a sagittal cleft through the vertebral body. Often presenting with low back pain or concomitant with an associated syndromic illness, SCV is often found incidentally and can mimic vertebral compression fractures radiographically. Treatment of SCV has largely been conservative and symptomatic. With only 109 reported cases in the current literature, we present a unique case of multiple SCV throughout the thoracolumbar region in an adolescent patient. We performed a review of the literature to identify published cases of SCV to date. We searched PUBMED using the terms "sagittal cleft vertebrae", "butterfly vertebrae", and "anterior rachischisis". Abstracts were screened for reports specifically involving original cases of SCV. Given the well-established association with syndromic illnesses, finding an SCV warrants further investigation for other abnormalities of the musculoskeletal, cardiac, and genitourinary systems. Complex management strategies are rare unless the SCV is associated with an aberrant syndrome, disc herniation or severe musculoskeletal abnormality, or symptomatic disc herniation requiring surgical management. Further studies should focus on uncovering the genetic markers leading to the cleft vertebral bodies, with a focus on early screening and monitoring of patients who could be predisposed to the condition.

Orbital fat herniation is primarily in a subconjunctival location. However, herniation through the inferior orbital fissure (IOF) has been scantly reported. Here, we report a cadaveric case of herniation of orbital fat through the inferior orbital fissure and into the infratemporal fossa. The cadaver’s orbital anatomy and orbital fat herniation were found during routine dissection. The details of this case are reported. We also discuss anatomical variations of the inferior orbital fissure as well as the related vascular and nervous system structures related to orbital fat herniation. This is a rare case of a cadaver with this anatomical abnormality.

The anatomical variations of the maxillary sinus septa, greater palatine artery, and posterior superior alveolar arteries might cause unexpected complications when they are damaged. Dentists who know these structures well might hope to learn more practical knowledge to avoid and assess injury preoperatively. Therefore, this review paper aimed to review the reported anatomy and variations of the maxillary sinus septa, greater palatine artery/nerve, and posterior superior alveolar artery, and to discuss what has to be assessed preoperatively to avoid iatrogenic injury. To assess the risk of injury of surgically significant anatomical structures in the maxillary sinus and hard palate, the operator should have preoperative three-dimensional images in their mind based on anatomical knowledge and palpation. Additionally, knowledge of the average measurement results from previous studies is important.

While palsy of the L5 nerve root due to stretch injury is a known complication in complex lumbosacral spine surgery, the underlying pathophysiology remains unclear. The goal of this cadaveric study was to quantify movement of the L5 nerve root during flexion/extension of the hip and lower lumbar spine.Five fresh-frozen human cadavers were dissected on both sides to expose the lumbar vertebral bodies and the L5 nerve roots. Movement of the L5 nerve root was tested during flexion and extension of the hip and lower lumbar spine. Four steps were undertaken to characterize these movements: (1) removal of the bilateral psoas muscles, (2) removal of the lumbar vertebral bodies including the transforaminal ligaments from L3 to L5, (3) opening and removing the dura mater laterally to visualize the rootlets, and (4) removal of remaining soft tissue surrounding the L5 nerve root. Two metal bars were inserted into the sacral body at the level of S1 as fixed landmarks. The tips of these bars were connected to make a line for the ruler that was used to measure movement of the L5 nerve roots. Movement was regarded as measurable when there was an L5 nerve excursion of at least 1 mm.The mean age at death was 86.6 years (range 68-89 years). None of the four steps revealed any measurable movement after flexion/extension of the hip and lower lumbar spine on either side ( 1 mm). Flexion of the hip and lower lumbar spine revealed lax L5 nerve roots. Extension of the hip and lower lumbar spine showed taut ones.Significant movement or displacement of the L5 nerve root could not be quantified in this study. No mechanical cause for L5 nerve palsy could be identified so the etiology of the condition remains unclear.

This study aimed to investigate the relationship between the retromolar gland and pad, and the relationship between the LN and retromolar gland/pad to establish a new landmark for avoiding LN injury. Sixty-two lingual nerves from fresh-frozen cadavers were used for this study. The age of the specimens at the time of death ranged from 57 to 98 with a mean of 76.5 years. The mucous incision was made into the medial border of the retromolar pad and the submucosal tissue depth of the initial incision was bluntly dissected to expose the lingual nerve. When the LN was identified, the mucosa overlying the retromolar pad was removed to expose the retromolar gland to confirm if the retromolar pad corresponds to the retromolar gland. On all sides, the lingual nerve was found to course medial to the retromolar pad and inferior to the inferior border of the superior pharyngeal constrictor muscle to enter the sublingual space via the pterygomandibular space. The retromolar pad corresponded to the retromolar gland on all sides. This demonstrated that the retromolar pad is an overlying mucosa of the retromolar gland. No LN was found to travel through the retromolar gland. We suggest that the retromolar pad can be used as a new landmark for avoiding iatrogenic LN injury.

An accessory foramen around the mandibular foramen is called an accessory mandibular foramen (AMF). The clinical anatomy of the AMF has not been well described. The aim of this study was to reveal the clinical anatomy of the AMF for a better understanding of its implication during ramus surgeries. Twenty-two sides fresh-frozen cadaveric heads with a mean age of 76.2 ± 14.4 years at death underwent dissection. The neurovascular bundles passing through the AMF were observed. Additionally, a hemi-face of a latex injected embalmed cadaver was dissected medially to laterally and the neurovascular bundles of the AMF investigated. A unilateral foramen, bilateral foramina, and absence of foramina were found in 45.4%, 18.2%, and 36.4%, respectively. The origin of the neurovascular bundle entering the AMF was a branch of the maxillary artery in 20% and a tributary of the inferior alveolar vein in 80%. In the latex embalmed cadaver, the AMF was found to contain a branch from the maxillary artery and a tributary of the maxillary vein. Given the practical meaning of the specific AMF located in the operative field of the ramus osteotomy, we suggest these be named “foramina for ramus osteotomy.”

Periosteal releasing incision (PRI) techniques are often used with guided bone regeneration procedures. As complications such as intra- and postoperative bleeding have been noticed, we aimed to study and clarify these as related to the PRI, especially on the mandibular buccal periosteum. Fourteen sides from seven fresh-frozen Caucasian cadaveric heads were used in this study. The seven cadavers were derived from two females and five males. The mean age at the time of death was 75.9 ± 10.8 years. The PRI was made using a no. 15c blade using a surgical microscope. Subsequently, the fat tissue lateral to the periosteum was slightly dissected. The diameter of the facial artery (or its branch) and closest relationship between the tooth and position of the artery was recorded. Finally, the artery was traced back proximally to clarify its origin. On all sides, the inferior labial artery (ILA) was identified in the fat tissue lateral to and close to the periosteum. The ILA was closest to the periosteum at the midpoint of the PRI (approximately between the first and second molar teeth area or 10 mm mesial to the apex of the retromolar pad). The mean diameter of the ILA was 2.72 ± 0.26 mm. This anatomical finding should encourage dentists to make the PRI incision without invading the tissue underneath the periosteum.

We present a rare anatomical variation in which an additional incisive canal was observed during the routine dissection of the palatal region in a cadaver. The diameter of the incisive and additional incisive canals measured 4.59 mm and 0.91 mm, respectively. Even though this variation is rare, oral surgeons should be aware of such anatomical variations for a better understanding.

The palatine aponeurosis is a thin, fibrous lamella comprising the extended tendons of the tensor veli palatini muscles, attached to the posterior border and inferior surface of the palatine bone. In dentistry, the relationship between the “vibrating line” and the border of the hard and soft palate has long been discussed. However, to our knowledge, there has been no discussion of the relationship between the palatine aponeurosis and the vibrating line(s). Twenty sides from ten fresh frozen White cadaveric heads (seven males and three females) whose mean age at death was 79 years) were used in this study. The thickness of the mucosa including the submucosal tissue was measured. The maximum length of the palatine aponeurosis on each side and the distance from the posterior nasal spine to the posterior border of the palatine aponeurosis in the midline were also measured. The relationship between the marked borderlines and the posterior border of the palatine bone was observed. The thickness of the mucosa and submucosal tissue on the posterior nasal spine and the maximum length of the palatine aponeurosis were 3.4 mm, and 12.2 mm on right side and 12.8 mm on left, respectively. The length of the palatine aponeurosis in the midline was 4.9 mm. In all specimens, the borderline between the compressible and incompressible parts corresponded to the posterior border of the palatine bone.

In the surgical setting, horseshoe kidneys (HKs) may be a cause for confusion because of their complicated morphology, especially in the vicinity of the vascular and urinary collecting systems around the isthmus of the HK. In the patients with HK, analysis of the anatomical structure of the isthmus is both useful and necessary. The aim of this study is to observe the vascular and collecting system of the HK using anatomical and contrast imaging technique, then make use of the knowledge for clinical anatomy. A HK voluntarily donated post-mortem to our department in 2013 by an 80-year-old woman was dissected. The gross anatomy of this HK was reported. In this study, we additionally analyzed this kidney using micro-computed tomography with both colored and colorless contrast media after the kidney was made transparent. Contrast imaging clearly revealed that each of the five renal arteries, including the three surplus renal arteries, entering the HK distributed blood to different regions. Neither side of the urinary collecting system crossed the midline of the isthmus. Two surplus renal veins emerged from the HK and two ureters descended dorsal to the isthmus. These observations show that gross anatomical observation and contrast imaging of the HK can provide very important surgical information. Our results can contribute to both better understanding of fundamental knowledge and progress in the surgery of HKs such as in the setting of biopsy and transplantation.