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The clinical anatomy of accessory mandibular canal in dentistry

Ngeow WC, Chai WL

Clin Anat, 2020 Nov;33(8):1214-1227.
PMID: 31943382 DOI: 10.1002/ca.23567

The mandibular canal is a conduit that allows the inferior alveolar neurovascular bundle to transverse the mandible to supply the dentition, jawbone and soft tissue around the gingiva and the lower lip. It is not a single canal but an anatomical structure with multiple branches and variations. The branches are termed accessory, bifid or trifid canals depending on their number and configuration. A bifid mandibular canal is an anatomical variation reported more commonly than the trifid variant. Because of these variations, it is of the utmost importance to determine the exact location of the mandibular canal and to identify any branches arising from it prior to performing surgery in the mandible. This article reviews the prevalence, classification and morphometric measurements of these accessory mandibular canals, emphasizing their clinical significance.

Matched MeSH terms: Anatomic Variation*
A new system for classifying accessory canal morphology

Ahmed HMA, Neelakantan P, Dummer PMH

Int Endod J, 2018 Feb;51(2):164-176.
PMID: 28635100 DOI: 10.1111/iej.12800

Thorough knowledge of anatomical complexities of the root canal system has a direct impact on the effectiveness of canal preparation and filling, and is an essential prerequisite for successful root canal treatment. A wide range of complex variations in root canal anatomy exists, including root canal configuration type, developmental anomalies and minor canal morphology such as accessory canals and apical deltas. Accessory canals and apical deltas have been associated with pulp disease, primary canal infection, canal reinfection and post-treatment disease. The current definitions of accessory canal anatomy are not standardized and potentially confusing. Given their role in endodontic disease and their impact on treatment outcomes, there is a need to have a simple classification of their anatomy to provide an accurate description of their position and path from the canal to the external surface of the root. The purpose of this article is to introduce a new system for classifying accessory canal morphology for use in research, clinical practice and training.

Matched MeSH terms: Anatomic Variation*
Multifaceted profile of an unusual paramedian occipital condyle-anatomical and computerised tomographic evaluation

Arora J, Mehta V, Abhishek K, Nisha S, Suri RK, Rath G, et al.

Clin Ter, 2014;165(2):111-4.
PMID: 24770815 DOI: 10.7471/CT.2014.1687

During extensive osteological study of 150 dry skulls in the Department of Anatomy, Vardhman Mahavir Medical college, an unusual Paramedian Occipital (POC) condyle was detected in the occipital bone of a cadaveric skull. The anatomical details of this unusual occipital condyle were carefully studied and its morphometric measurements taken. A coronal multiplanner reformatted image and a volume rendered image were taken to study radiological details and establish significant clinical correlation. Precise understanding of anatomy of craniovertebral junction and its anomalies have become immensely important for the present day surgeon during orthopaedic and neurosurgical procedures of this region . Technical advancements in imaging modalities such as CT and MRI scans further signify the importance of these anatomical variations ,which are often missed in routine examination. Osteological study combined with radiological details of the paramedian occipital condyle in the present case aims to emphasize the importance of bony anomalies in the craniovertebral region and their role in diagnosis and appropriate treatment of neurovascular compression syndromes of craniovertebral junction. The present study highlights anatomical details, clinical relevance and embryological basis of such a rare unusual paramedian occipital condyle.

Matched MeSH terms: Anatomic Variation*
Transposition and variant termination of azygos and hemiazygos veins: an extremely rare variation

Nayak SB, Soumya KV

Surg Radiol Anat, 2020 Nov;42(11):1303-1306.
PMID: 32328708 DOI: 10.1007/s00276-020-02471-1

Azygos system of veins is the main source of venous drainage from the thoracic wall. Knowledge of azygos vein anomalies could be of importance to cardiothoracic surgeons and radiologists. We report a rare variation of azygos vein as seen in an adult male cadaver aged 65 years approximately. The azygos vein was formed by the union of left ascending lumbar and subcostal veins. It coursed upwards on the left side of descending thoracic aorta and crossed the left subclavian artery and the left vagus to terminate into the left brachiocephalic vein. It received left superior intercostal vein and left fifth to eleventh posterior intercostal veins. The hemiazygos and accessory hemiazygos veins were situated on the right side of the vertebral column. They received the right posterior intercostal veins and terminated into the azygos vein at the level of eighth thoracic vertebra.

Matched MeSH terms: Anatomic Variation*
Fulltext Sternocleidohyoid muscle: an unreported variant of cleidohyoid muscle

Nayak SB, Shetty SD

Surg Radiol Anat, 2021 Aug;43(8):1327-1330.
PMID: 33527215 DOI: 10.1007/s00276-021-02682-0

Sternohyoid, sternothyroid, omohyoid, and thyrohyoid muscles are collectively known as infrahyoid muscles. These muscles frequently show variations in their attachments. Here, an extremely rare variant muscle belonging to this group has been presented. During cadaveric dissection for undergraduate medical students, an additional muscle was found between sternohyoid and superior belly of omohyoid muscles bilaterally in a male cadaver aged approximately 70 years. This muscle took its origin from posterior surface of the manubrium sterni, capsule of the sternoclavicular joint and the posterior surface of the medial part of the clavicle. It was inserted to the hyoid bone between the attachments of sternohyoid and superior belly of omohyoid muscles and was supplied by a branch of ansa cervicalis profunda. There is no report on such a muscle in the literature and it could be named as "sternocleidohyoid muscle". Knowledge of this muscle could be useful in neck surgeries.

Matched MeSH terms: Anatomic Variation*
Anatomical variants of surgically important landmarks in the sphenoid sinus: a radiologic study in Southeast Asian patients

Anusha B, Baharudin A, Philip R, Harvinder S, Shaffie BM, Ramiza RR

Surg Radiol Anat, 2015 Dec;37(10):1183-90.
PMID: 25990686 DOI: 10.1007/s00276-015-1494-8

Failure of a surgeon to understand the local variations of the anatomical landmarks of the sphenoid sinus is a potential risk factor to cause damage to the optic nerve (ON) or internal carotid artery (ICA) that lies on the walls of the sphenoid sinus. The aim of this study was to identify the anatomical variants of the sphenoid sinus and its related surrounding structures among the Southeast Asian (SEA) population, based on computed tomography (CT) scans.

Matched MeSH terms: Anatomic Variation
Anatomical variations of anterior ethmoidal artery at the ethmoidal roof and anterior skull base in Asians

Abdullah B, Lim EH, Mohamad H, Husain S, Aziz ME, Snidvongs K, et al.

Surg Radiol Anat, 2019 May;41(5):543-550.
PMID: 30542929 DOI: 10.1007/s00276-018-2157-3

PURPOSE: The variations of the anterior ethmoidal artery (AEA) in different populations should be recognized by surgeons to prevent unwarranted complications during surgery. The aim of this study was to assess the anatomical variations of AEA in Asian population.
METHODS: A cross-sectional study of 252 AEA identified by computed tomography (CT) of the paranasal sinuses. The multiplanar CT images were acquired from SOMATOM® Definition AS+ and reconstructed to axial, coronal and sagittal view at 1 mm slice thickness.
RESULTS: 42.5% of AEA was within skull base (grade I), 20.2% at skull base (grade II) and 37.3% coursed freely below skull base (grade III). The prevalence of supraorbital ethmoid cell (SOEC) and suprabullar cell (SBC) was 29.8% and 48.0%. The position of AEA at skull base has significant association with SOEC (p

Matched MeSH terms: Anatomic Variation*
Morphometric analysis and surgical adequacy of palmaris longus as a tendon graft. A systematic review of cadaveric studies

Yammine K, Erić M

Surg Radiol Anat, 2020 Mar;42(3):259-267.
PMID: 31741040 DOI: 10.1007/s00276-019-02381-x

INTRODUCTION: The tendon of the palmaris longus is commonly used as a tendon graft in many reconstructive surgeries. Easy to access and at proximity to the hand, the palmaris longus tendon is considered as the optimal tendon source for hand reconstructive surgery. However, and besides its inconsistency, the size of the palmaris longus tendon is reported to show variability. The aim of this study is to look for the surgical adequacy of the palmaris longus tendon by conducting a quantitative synthesis on its length and width in human populations and its correlation with the forearm length.
METHODS: Twenty-four studies met the inclusion criteria including 1761 cadaveric limbs.
RESULTS: The results were as following: (a) the mean palmaris longus tendon length was of 13.9 ± 2.6 cm, (b) the mean ratio palmaris longus tendon length/forearm length was of 0.545 ± 0.06, (c) the weighted correlation value was of 0.686, and (d) the mean palmaris longus tendon width was of 4.0 ± 1.7 mm. Only five studies reported a palmaris longus tendon length of more than 15 cm. The palmaris longus tendon length was shown to vary between ancestries; the Japanese had the shortest while Malaysian the longest palmaris longus tendons. All studies but one reported a palmaris longus tendon mean width of more than 3 mm where the minimal mean palmaris longus tendon width was of 2.5 mm.
CONCLUSION: While the requested length depends on the recipient site and/or type of reconstructive surgery, the palmaris longus tendon often met the required diameter for grafting. Our review demonstrated that while palmaris longus length varies between ancestries, its width is often adequate for grafting. In addition, the forearm length could be a good predictor of palmaris longus tendon length; such correlation could assist surgeons when planning to use palmaris longus tendon as a graft source.

Matched MeSH terms: Anatomic Variation*
Anatomical variations of anterior ethmoidal artery and their significance in endoscopic sinus surgery: a systematic review

Abdullah B, Lim EH, Husain S, Snidvongs K, Wang Y

Surg Radiol Anat, 2019 May;41(5):491-499.
PMID: 30542930 DOI: 10.1007/s00276-018-2165-3

PURPOSE: Anterior ethmoidal artery (AEA) is at risk of injury in endoscopic sinus surgery due to its location. The aim of this review was to assess the anatomical variations of AEA and their significance.
METHODS: A literature search was performed on PUBMED, SCOPUS AND EMBASE. The following keywords were used: ethmoidal artery; anterior ethmoidal artery; anterior ethmoidal canal; ethmoid sinus; ethmoid roof; skull base. The search was conducted over a period of 6 months between October 2016 and April 2017.
RESULTS: 105 articles were retrieved. 76 articles which were either case reports or unrelated topics were excluded. Out of the 29 full text articles retrieved, 16 articles were selected; 3 were cadaveric dissection, 5 combined cadaveric dissection and computed tomography (CT) and the rest were of CT studies. All studies were of level III evidence and a total of 1985 arteries were studied. Its position at the skull base was influenced by the presence of supraorbital ethmoid cell (SOEC) and length of the lateral lamella of cribriform plate (LLCP). Inter population morphological variations contribute to the anatomical variations.
CONCLUSIONS: The average diameter of AEA was 0.80 mm and the intranasal length was 5.82 mm. 79.2% was found between the second and third lamellae, 12.0% in the third lamella, 6% posterior to third lamella and 1.2% in the second lamella. Extra precaution should be taken in the presence of a well-pneumatized SOEC and a long LLCP as AEA tends to run freely below skull base.

Matched MeSH terms: Anatomic Variation
A new system for classifying root and root canal morphology

Ahmed HMA, Versiani MA, De-Deus G, Dummer PMH

Int Endod J, 2017 Aug;50(8):761-770.
PMID: 27578418 DOI: 10.1111/iej.12685

Knowledge of root and root canal morphology is a prerequisite for effective nonsurgical and surgical endodontic treatments. The external and internal morphological features of roots are variable and complex, and several classifications have been proposed to define the various types of canal configurations that occur commonly. More recently, improvements in nondestructive digital image systems, such as cone-beam and micro-computed tomography, as well as the use of magnification in clinical practice, have increased the number of reports on complex root canal anatomy. Importantly, using these newer techniques, it has become apparent that it is not possible to classify many root canal configurations using the existing systems. The purpose of this article is to introduce a new classification system that can be adapted to categorize root and root canal configurations in an accurate, simple and reliable manner that can be used in research, clinical practice and training.

Matched MeSH terms: Anatomic Variation
Variant Abductor Pollicis Longus Muscle: a Case Report

Shipra P, Srijit D

Acta Medica (Hradec Kralove), 2007;50(3):213-215.
PMID: 28795947 DOI: 10.14712/18059694.2017.85

Abductor pollicis longus (APL) muscle is known to exhibit different variations with respect to its attachments. Various studies have reported the splitting of the APL muscle. Comparative anatomical findings of split insertion of APL is commonly found in chimpanzees, gorillas and gibbons. In the present study, we describe an anomalous APL muscle, which originated from the posterior surface of the shaft of the radius and ulna and traversed a course deep to the extensor retinaculum. Interestingly, immediately after emerging form the deeper aspect of extensor retinaculum, the thin tendon of the APL muscle continued again as a muscular belly in relation to the dorsolateral part of the 1st metacarpal bone, to end as a tendon with its attachment to the base of the proximal phalanx. Such an unusual variation of APL with its attachment into proximal phalanx is a rare finding and may be of importance in altering the mechanics of the thumb during abduction. The clinical significance of such an anatomical variation of APL may be important during reconstructive surgeries involving thumb and also of academic interest.

Matched MeSH terms: Anatomic Variation
Fulltext Surgical and embryological perspective of a big loop of internal carotid artery extending laterally beyond internal jugular vein

Nayak SB, Shetty SD

Surg Radiol Anat, 2021 Mar;43(3):413-416.
PMID: 33231750 DOI: 10.1007/s00276-020-02619-z

Knowledge of variations of the internal carotid artery is significant to surgeons and radiologists. The internal carotid artery normally runs a straight course in the neck. Its anomalies can lead to its iatrogenic injuries. We report a case of a large loop of the internal carotid artery in a male cadaver aged about 75 years. The common carotid artery terminated by dividing it into the external carotid artery and internal carotid arteries at the level of the upper border of the thyroid cartilage. From the level of origin, the internal carotid artery coursed upwards, backwards and laterally, and formed a large loop behind the internal jugular vein. The variation was found on the left side of the neck and was unilateral. The uncommon looping of the internal carotid artery might result in altered blood flow to the brain and may lead to misperceptions in surgical, imaging, and invasive procedures.

Matched MeSH terms: Anatomic Variation*
Fulltext Accessory roots in maxillary molar teeth: a review and endodontic considerations

Ahmed HM, Abbott PV

Aust Dent J, 2012 Jun;57(2):123-31; quiz 248.
PMID: 22624750 DOI: 10.1111/j.1834-7819.2012.01678.x

Maxillary molar teeth may have accessory roots. The aim of this paper is to review and discuss the endodontic implications of this anatomical variation. A review of the literature was undertaken to identify studies and reported cases where accessory roots have been recorded in maxillary molar teeth. The results show that although the prevalence of accessory roots in maxillary molar teeth is low, they can exist in all three types of maxillary molar teeth, and they may be located palatally, buccally, mesially or distally. Hence, it is essential that dentists undertaking root canal treatment thoroughly assess all teeth to determine how many roots are present in order to provide the best possible outcome of treatment for the patient.

Matched MeSH terms: Anatomic Variation

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