Bifurcation of the sciatic nerve: A descriptive study on a South African cadaver cohort.

BACKGROUND: The sciatic nerve bifurcates into the tibial and common fibular nerves in six different regions: the pelvic region, gluteal region, proximal, middle, or distal third of the posterior thigh, or in the popliteal fossa. Inadequate knowledge of sciatic nerve anatomy could lead to failed nerve blocks, and damage during intramuscular injections. Limited studies have been done on African population groups and lack a quantifiable method to classify the levels of sciatic nerve bifurcation. AIM: Thus, this descriptive cadaver study aimed to assess the bifurcation level of the sciatic nerve in a South African population group using a quantifiable method. METHODS: Three hundred and thirty-eight formalin-fixed limbs from three universities were dissected between March and August 2018. Type A was classified if the sciatic nerve bifurcated within the pelvic region. A sciatic nerve bifurcation level index (SNBLI) was developed for this study to quantitatively classify the region of sciatic nerve bifurcation into types B to F. RESULTS: Type F bifurcation was most common (79.6%), and types B and C were not observed. In 15 (0.04%) specimens, two separate nerves entered the gluteal region and converged to form the sciatic nerve distal to the piriformis, which could bifurcate either in the distal third of the posterior thigh or popliteal fossa. CONCLUSION: This is the first study to provide information on the sciatic nerve bifurcation in a large South African cadaver cohort. Moreover, we created a quantifiable method that can be used to classify the sciatic nerve bifurcation level. This will be beneficial in ensuring accurate comparison between different population groups in future.

The posterior intercostal vein: a thermoregulatory gateway to the internal vertebral venous plexus.

The internal vertebral venous plexus (IVVP) plays a putative role in thermoregulation of the spinal cord. Cold cutaneous venous blood may cool, while warm venous blood from muscles and brown fat areas may warm the spinal cord. The regulating mechanisms for both cooling and warming are still unknown. Warm venous blood mainly enters the IVVP via the intervertebral veins. In the thoracic area these veins are connected to the posterior intercostal veins. In this study, anatomical structures were investigated that might support the mechanisms by which warmed venous blood from the intercostal muscles and the recently described paravertebral patches of brown adipose tissue are able to drain into the vertebral venous plexus. Therefore, tissue samples from human cadavers (n = 21) containing the posterior intercostal vein and its connections to the IVVP and the azygos veins were removed and processed for histology. Serial sections revealed that the proximal parts of the posterior intercostal veins contained abundant smooth muscle fibers at their opening into the azygos vein. Furthermore, the walls of the proximal parts of the posterior intercostal veins contain plicae that allow the vessel to dilate, thereby allowing it to serve as a pressure chamber. It is suggested that a cold induced closure of the intercostal/azygos opening can result in retrograde blood flow from the proximal posterior intercostal vein towards the IVVP. This blood flow would be composed of warm blood from the paravertebral brown adipose tissue and blood containing metabolic heat from the muscles draining into the intercostal veins.

Bony landmarks as an aid for intraoperative facial nerve identification.

Identification of the facial nerve trunk is essential during surgery of the parotid gland. Numerous landmarks have been researched and used. The relation between the facial nerve to two constant bony landmarks, the tip of the mastoid process and the central point of the transverse process of the atlas was investigated. Forty cadavers were dissected. A preauricular incision exposed the nerve trunk. Bony landmarks were identified and marked. The distance from the nerve trunk to the mastoid process and the atlas was measured. The mean distance between the mastoid process and nerve for the left was 9.18 +/- 2.05 mm and for the right, 9.35 +/- 1.67 mm. The mean distance between the atlas and the nerve for the left was 14.31 +/- 3.59 mm and for the right, 13.76 +/- 4.65 mm. Confidence intervals were determined. The importance of the aforementioned data revolves around minimizing the chance of injury to the facial nerve during surgery. The applicability of these landmarks needs to be studied in the clinical setting.

Evaluation of clinical relevance of a problem-orientated head and neck module.

Current trends in medical education focus on outcomes-based learning as a means to facilitate student learning. The aim of this study was to evaluate a clinically applied module in head and neck anatomy for third-year dental students. The module linked clinical examination, regional dental blocks simulated on cadaver specimens, radiographic images and clinical case scenarios. A Likert-type questionnaire, completed by all students (n = 49), was used to evaluate student perceptions of this module objectively. The results indicate that an average number of students found that clinical examination received sufficient time (mean: 2.98) during the module, while a substantial number of students agreed that the integration of dental procedures stimulated them to study specific regional anatomy (mean: 3.82) and increased their interest in their future careers as dentists (mean: 4.04). The radiographs improved their understanding of anatomy (mean: 3.41) while the clinical case studies were a positive learning experience (mean: 3.10). The majority of students (mean: 4.12) felt that they were continuously made aware that they were studying appropriate matter for their future work as dentists. It seems evident that the integration of clinically relevant content facilitates and encourages the understanding of anatomy.

Mandibular spine: a case report.

This is a brief review of the origin and normal variations of the genial tubercles, and specifically, a mandibular spine as an anatomical variation or abnormality. The case presented is that of abnormal genial tubercles observed during dissection of the floor of the mouth. A review and description on the morphology of the genial tubercles are given.