The Anterolateral Ligament of the Knee Is a Nonisometric Thin Ligament With High Prevalence and Almost Constant Attachment to the Lateral Meniscus: A Systematic Review With Meta-analysis.

PURPOSE: To provide comprehensive information about the anterolateral ligament (ALL) prevalence, morphometry, isometry, insertions, histology, and its relationship with the lateral meniscus (LM). METHODS: The study was performed, according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Eligible cadaveric studies investigating the frequency of the ALL presence, and anatomical features were identified through an online search of the PubMed, Scopus, and Cochrane Central databases from inception to June 2022. Statistical analysis was conducted with the open-source R programming language using the "meta" package. The Higgins I2 statistic was used for quantifying heterogeneity. RESULTS: Thirty-three studies (1,478 cadaveric knees) were included. The ALL had a 79% prevalence. It was attached to the LM periphery in 97% of studies. Most studies reported a femoral insertion of the ALL, just proximal and posterior to the lateral epicondyle. Tibial attachment is constant at the midpoint between Gerdy's tubercle and fibular head. The mean ALL thickness at the joint line was 1.6 [1.2; 2.0] mm. The ALL length was found to significantly change across the knee flexion (P < .01). It was increased from 0° to 60° and decreased after 60° flexion. Seven histological studies demonstrated a typical ligamentous microstructure. CONCLUSION: The ALL is a thin ligament, distinct to the knee capsule, which may be found in 79% of the knees having an almost constant attachment to the LM. The ALL is not isometric. It becomes tense during internal rotation and between 30° and 60° knee flexion. Pooled results should be interpreted with caution due to the high heterogeneity among the included studies. CLINICAL RELEVANCE: This study sheds light on controversial issues and provides comprehensive and accurate information about the essential anatomical knowledge on ALL, which may contribute to optimizing ALL reconstruction surgical techniques and biomechanical settings.

Hippocrates: A Pioneer in Orthopaedics and Traumatology.

PURPOSE: Hippocrates, the ancient Greek physician, is considered the father of Medicine; however, his contributions to Orthopaedics and Traumatology have not been highlighted enough. The present historical review represents an effort to present and categorize his work, in this field, per clinical disorder and anatomical region. METHODS: The "Hippocratic Corpus" original text was thoroughly studied to identify all Hippocrates' contributions in Orthopaedics and Traumatology. Volume III of his works, especially "On Fractures", "On Joints", and "Mochlicon" includes a plethora of information regarding the management of traumas, as well as other disorders and clinical entities of the musculoskeletal system. RESULTS: In particular, Hippocrates describes reduction techniques for fractures, as well as joint dislocations, elaborates on the biology of the fractures' healing process and the basic principles of fracture management and fixation, presents the signs and symptoms of gangrene, teaches the treatment of osseous infections and offers valuable insight on the biomechanics and treatment of spinal diseases. CONCLUSIONS: Hippocrates' contributions in Orthopaedics and Traumatology are unprecedented, making him a true pioneer in this field, while the basic principles that he presented were further studied and confirmed in the 19th and 20th centuries.

The enigmatic os supratrochleare anterius: from rarity to recognition in elbow pathology-case report and review of literature.

Accessory bones around the elbow are scarce, with a reported mean incidence rate of 0.77%. The rarest one is the os supratrochleare anterius, with only a handful of documented cases in the literature. Despite their scarcity, various types of ossicles have been documented, posing diagnostic challenges and potential misinterpretation on X-rays. Herein, we report a case of an accidentally found os supratrochleare anterius in a 43-year-old pig farmer presenting with symptoms of tennis elbow. After conservative treatment with nonsteroidal anti-inflammatory drugs and physiotherapy, he made a full recovery within 2 weeks. This report emphasizes the rarity of the ossupra trochleare anterius, the importance of accurate diagnosis, and the need for continued research and awareness of this anatomical variation.

Exploring consistent ratios in morphometry of the proximal tibia: insights for knee arthroplasty.

INTRODUCTION: The current study, which delves into proximal tibia morphometric parameters in a Greek sample, not only analyzes whether specific linear distance ratios are consistent but also paves the way for a potential novel metric system for knee arthroplasty imaging studies using constant ratios. These findings could have significant implications for future enlarged research and clinical practice. METHODS: A total of 38 dried tibiae were evaluated by two independent investigators. The following distances were measured with a digital Vernier sliding caliper: (1) the mediolateral distance of the proximal surface (A), (2) the anteroposterior distance of the proximal surface (B), (3) The longitudinal length of the bone (C), (4) the line connecting the anterior margin of the proximal surface with the highest peak of the tibia tuberosity (D), (5) the depth of the proximal margin of the medial articular facet (AF) (medial plateau) (E) and (6) the depth of the proximal margin of the lateral AF (lateral plateau) (F). RESULTS: The A, B, C, D, E, and F mean distances were 71.3 mm, 47.4 mm, 340.2 mm, 37.1 mm, 42 mm, and 35.9 mm. Reliability analysis for each observer on all measurements revealed an interclass correlation (ICC) score of 0.975 (observer 1) and 0.971 (observer 2). The ratio A/B was 1.5, A/C was a constant 0.2, and D/C was 0.1. The ratio E/F was 1.2. The six measurements (A-F) showed excellent inter-observer reliability (all ICC values > 0.990). CONCLUSIONS: The study established constant ratios of the studied linear distances around the proximal tibia. Considering these ratios, asymmetrical tibial components in knee arthroplasty seem to replicate the native anatomy more closely. Furthermore, the distance from the anterior margin of the proximal surface to the tibial tuberosity peak, constituting one-tenth of the longitudinal length of the tibia, shows promise as a metric system for imaging studies, especially in assessing lesions around tibial components.

An ectopic thyrolingual trunk arising from the common carotid artery: a rare variant.

The common carotid artery (CCA) typically bifurcates into the external and internal carotid arteries (ECA and ICA). In the head and neck area, the ECA gives off a few anterior branches from proximal to distal: the superior thyroid artery (STA), the lingual artery (LA), and the facial artery (FA). Occasionally, these branches can fuse into trunks, with the linguofacial trunk being the most common. During a computed tomography angiography (CTA) of a 67-year-old patient, a common arterial trunk, 11.3 mm proximal (prior) to the CCA bifurcation was recorded. The trunk was formed by the STA and the LA fusion and was characterized as a thyrolingual trunk (TLT). These trunks have been reported with a prevalence ranging between 0.3 and 1% and correspond to one of the rarest variants of the ECA anterior branches. Knowledge of the typical and variant anatomy of the carotid arteries and their branches is of paramount importance to surgeons and interventional radiologists.

A scarce combination of arterial variants: an occipital artery originating from the internal carotid artery associated with a linguofacial trunk.

The occipital artery (OA) typically originates from the external carotid artery (ECA). Variations of the ECA has been well described in the current literature, while the OA is a relatively stable vessel, and its variations are uncommon. In the current case report, an aberrant OA has been found coexisting with a linguofacial trunk (LFT) on the right hemineck of a 51-year-old male patient. The OA was identified originating from the cervical internal carotid artery (ICA) at the level of the second cervical vertebra (C2). On the ECA, the lingual and facial arteries were emanating in common, as LFT. The left hemineck of the patient was free of variations. The current coexistence of arterial variants has been reported only once previously; therefore, the current case corresponds to the second case in the English literature. The aberrant OA origin from the ICA has been estimated with a pooled prevalence of 0.37%, while the origin at the C2 level and from the anterior surface of the ICA corresponds to a very rare variation. Additionally, the LFT is one of the most common trunk that can be found on the ECA. Interventional radiologists and surgeons must be aware of common and uncommon variation to avoid iatrogenic lesion.

Considerations for the value of three-dimensional printed (3DP) versus cadaveric specimens for anatomy education.

We enjoyed reading the Brumpt et al. paper, which showed that a three-dimensional printed model (3DPM) of the ear was more effective than conventional cadaveric models for teaching anatomy. We would like to comment on the findings of this exciting study. In this case, the 3DPM of the ear was compared with dried bone models but not with a cadaveric specimen (with all adjacent soft tissues). The better results after the first test of students who used the 3DPMs were probably attributed to the optimized 3D representation of the ear anatomy. Also, the educational outcomes will likely be better if a more complex 3DPM is used, as it permits better visualization of the structures compared to the dried bone specimens. We certainly agree that 3DPMs have a remarkable ability to represent anatomy. Still, their effectiveness has not been proven superior to cadaveric specimens teaching complex anatomy. In conclusion, although we agree that 3DPMs have a high educational potential and can contribute to complex anatomy teaching, those models were not proven significantly more effective than cadaveric specimens in the Brumpt et al. study. The better effectiveness of 3DPMs compared to dried bone specimens (at the first test) does not mean those models are superior to specimens with retained soft tissues. Such cadaveric specimens permit visualization of complex structures and have proven valuable for teaching complex anatomy. Currently, the literature does not support the educational superiority of 3DPMs to those cadaveric specimens.

The coracobrachialis muscle: typical morphology, accessory forms, and the issues with terminology.

The coracobrachialis muscle (CB) represents one of the anterior arm compartment muscles. It has been defined by classic anatomy textbooks and old papers, as a muscle of one belly arising from the coracoid process tip and partially from the tendon of the biceps brachii short head, and inserted into the humeral shaft, above the bone's midpoint. However, recent cadaveric studies have confirmed that in the majority of cases, the CB is a two-headed muscle consisting of a superficial and a deep head. This finding has caused confusion regarding the terminology of CB's morphology. Typical CB morphology, according to recent data should not be considered the muscle of one belly, but the two-headed muscle. In particular, the musculocutaneous nerve's (MCN) course plays an important role in defining the CB morphological characteristics. If the MCN courses medially to the CB, with no signs of penetration after dissection, it can be concluded, that the CB is composed of one head; otherwise, if the muscle is composed of two or more heads, the MCN will courses between the CB bellies. In conclusion, it is of paramount importance to adopt common-universal terminology. Hence, considering recent findings, if the CB origin and/or the insertion differs from the typical anatomy, an "atypical CB" is the proper definition of the muscle, while if this "atypical CB" coexists with a typical CB, the terminology "accessory CB" may be used.

A bilateral four-headed brachialis muscle with a variant innervation: a cadaveric report with possible clinical implications.

PURPOSE: Anterior compartment muscles of the arm present high morphological variability, with possible clinical significance. The current cadaveric report aims to describe a bilateral four-headed brachialis muscle (BM) with aberrant innervation. Emphasis on the embryological background and possible clinical significance are also provided. METHODS: Classical upper limb dissection was performed on an 84-year-old donated male cadaver. The cadaver was donated to the Anatomy Department of the National and Kapodistrian University of Athens. RESULTS: On the left upper limb, the four-headed BM was supplied by the musculocutaneous and the median nerves after their interconnection. On the right upper limb, the four-headed BM received its innervation from the median nerve due to the musculocutaneous nerve absence. A bilateral muscular tunnel for the radial nerve passage was identified, between the BM accessory heads and the brachioradialis muscle. CONCLUSION: BM has clinical significance, due to its proximity to important neurovascular structures and frequent surgeries at the humerus. Hence, knowledge of these variants should keep orthopedic surgeons alert when intervening in this area. Further dissection studies with a standardized protocol are needed to elucidate the prevalence of BM aberrations and concomitant variants.

Jugular bulb anatomical variations and pneumatization patterns: a comprehensive CBCT analysis.

PURPOSE: This study aims to assess the anatomical possibilities of the jugular bulb (JB). METHODS: Fifty archived CBCT scans were analyzed. RESULTS: The average distance between the internal acoustic canal (IAC) and the JB was 7.97 mm on both sides (Right: SD = 2.56 mm, range 3.16-13.3 mm; Left: SD = 2.5 mm, range 2.9-13.6 mm). JB walls' pneumatization was classified into eight patterns. Deep petrosal cells (DPCs) prevailed in the lateral wall of the JB. The absence of pneumatization (NP) was commonly found on the left side. The presence of infralabyrinthine and hypotympanic cells varied. Less common types included accessory occipital cells (AOCs), posteromedial tracts (PMTs), and basi-occipital cells (BOCs), which determined a consistent variation of the lateral wall pneumatization patterns. Pneumatization of the medial wall was not observed in 50 right sides and 49 left sides. The inferior wall analysis revealed symmetry in AOC distribution and a predominant occurrence of NP. Cases with hypotympanum (HT) in the lateral wall showed a statistically significant IAC-JB distance increase by an average of 4.67 mm compared to NPs. Specific pneumatizations, particularly HT on the lateral side, have a significant effect on the IAC-JB distance, showing a clear pattern of increasing distance from DPC to NP and then to HT. A significant distance increase in HT pneumatization was noted. There were also recorded instances of JB hypoplasia and hyperplasia, JB diverticula, dehiscent JBs, and high JBs. CONCLUSION: This study establishes a novel classification of JB pneumatizations to aid in the understanding of the temporal bone anatomy.

Fenestration of the anterior and posterior cerebral arteries in coexistence with a contralateral posterior cerebral artery of fetal origin.

PURPOSE: The present case report aims to describe the rare coexistence of three variants of the cerebral arterial system diagnosed by computed tomography angiography (CTA). METHODS: A retrospective study on head and neck CTAs was performed on a Greek adult population from the Department of Radiology, University Hospital of Larissa. An interesting case of an 80-year-old male was further investigated. RESULTS: The cerebral arterial circle presented with a combination of three variations. The left anterior cerebral artery (ACA) was fenestrated 1.4 mm proximally to the anterior communicating artery formation. The left posterior cerebral artery (PCA) was also fenestrated, 5.5 mm distally to its origin from the basilar artery. Lastly, the right PCA originated from the ICA supraclinoid segment. CONCLUSIONS: This case report highlights an unusual coexistence of A1 and P1 segments fenestration with a fetal PCA, resulting in a unique cerebral circle. A1 segment fenestration has been previously reported as rare, while the PCA fenestration as extremely rare variant. Awareness of these rare variations could aid interventionists in their preoperative assessments.

The anterior communicating artery variants: a meta-analysis with a proposed classification system.

Morphological and morphometric variants of the anterior communicating artery (AComA) have been described by multiple studies; however, a complete classification system of all possible morphological variants with their prevalence is lacking. The current systematic review with meta-analysis combines data from different databases, concerning the AComA morphological and morphometric variants (length and diameter). Emphasis was given to the related clinical implications to highlight the clinical value of their knowledge. The typical AComA morphology occurs with a pooled prevalence (PP) of 67.3%, while the PP of atypical AComA is 32.7%. The identified AComA morphological variants (artery's hypoplasia, absence, duplication, triplication, differed shape, fenestration, and the persistence of a median artery of the corpus callosum- MACC) were classified in order of frequency. The commonest presented variants were the AComA hypoplasia (8%) and the anterior cerebral artery (ACA) fusion (5.9%), and the rarest ones were the MACC persistence (2.3%), and the AComA triplication (0.7%). The knowledge of those variants is essential, especially for neurosurgeons operating in the area. Given the high prevalence of AComA aneurysms, an adequate and complete classification of those variants is of utmost importance.

Musculus pterygoideus proprius: A meta-analysis.

The pterygoideus proprius muscle can be found incidentally in the infratemporal fossa, where it is spatially associated with the muscles of mastication, the maxillary artery, and the trigeminal nerve and its branches. Anatomists have described the muscle in various ways over the past 160 years, chiefly as a musculotendinous structure that originates from the infratemporal crest of the sphenoid bone and inserts into the lateral pterygoid plate and the lateral pterygoid muscle. It is present in non-human primates, albeit rarely, with similar anatomical findings. Embryologically, the pterygoideus proprius is thought to have developed from the first pharyngeal arch mesenchyme along with other muscles of mastication. Its close association with the maxillary artery and trigeminal nerve suggests possible clinical significance in trigeminal neuralgia and temporomandibular joint disorders. The literature was reviewed systematically to detail the historical background of research on the pterygoideus proprius muscle and explain its morphology, prevalence, embryology, and potential clinical significance. Despite its rarity, we propose that it is important to recognize its presence when the infratemporal fossa is approached.

Muscle interconnections in the anterior and posterior arm compartment: a cadaveric case series with possible clinical implications.

PURPOSE: The report describes four cases of accessory bundles (ABs) or fibers connecting the muscles of the anterior with the posterior arm compartment. The ABs morphology (pure muscular or musculofascial or musculoaponeurotic) is described emphasizing their attachment points, characterized as muscles' interconnections. MATERIALS AND METHODS: Four formalin-embalmed donated male cadavers were dissected. RESULTS: The muscles' interconnections were unilaterally identified. In the first case, the two ABs originated from the coracobrachialis muscle (CB), received fibers from the biceps brachii (BB), and were inserted into the triceps brachii (TB) medial head. The ABs created an arch over the brachial vessels and the median nerve (MN). In the second case, an accessory musculoaponeurotic structure was identified between CB and TB medial head and extended over the brachial vessels. In the third case, the myofascial ABs between the BB short head and the upper arm fascia, coursed anterior to the MN, the brachial artery, and the ulnar nerve, with direction to the TB medial head. In the fourth case, the three muscular ABs originating from the CB superficial and deep heads, in common with the BB short head, joined the upper arm fascia and the TB medial head and possibly entrapped the musculocutaneous nerve, the MN, and the brachial artery. CONCLUSION: ABs or musculoaponeurotic extensions may predispose to complications due to their potential compression on nerves and vessels. Clinicians should consider the possible existence of such bridging variants between muscles, in the differential diagnosis of a patient presenting with ischemia, edema, or MN palsy symptoms.

The potential role of ChatGPT and artificial intelligence in anatomy education: a conversation with ChatGPT.

PURPOSE: A recent study published in the JMIR Med Educ Journal explored the potential impact of the Generative Pre-Train (ChatGPT), a generative language model, on medical education, research, and practice. In the present study, an interview with ChatGPT was conducted to determine its capabilities and potential for use in anatomy education (AE) and anatomy research (AR). METHODS: The study involved 18 questions asked of ChatGPT after obtaining an online subscription to the 4th edition. The questions were randomly selected and evaluated based on accuracy, relevance, and comprehensiveness. RESULTS: The ChatGPT provided accurate and well-structured anatomical descriptions, including clinical relevance and relationships between structures. The chatbot also offered concise summaries of chapters and helpful advice on anatomical terminology, even with complex terms. However, when it came to anatomical variants and their clinical significance, the chatbot's replies were inadequate unless variants were systematically classified into types. ChatGPT-4 generated multiple-choice quizzes and matching questions of varying difficulty levels, as well as summaries of articles when presented with text. However, the chatbot recognized its limitations in terms of accuracy, as did the authors of the current study. CONCLUSION: ChatGPT-4 can be a valuable interactive educational tool for students in the field of anatomy, encouraging engagement and further questions. However, it cannot replace the critical role of educators and should be used as a complementary tool. Future research should establish guidelines for ChatGPT's optimal use and application in medical education.

The sphenoidal emissary foramina prevalence: a meta-analysis of 6,369 subjects.

PURPOSE: To estimate the prevalence of the sphenoidal emissary foramina (SEF), and the effect of possible moderators on it. METHODS: A systematic online literature search was conducted. The pooled prevalence with 95% confidence intervals was estimated. Outlier and influential analyses were performed. The presence of small-study effect and publication bias were evaluated. Moderator analyses were executed to investigate the effect of the specimens' continent of origin, type of study (dried skull or imaging), probing for the evaluation of SEF patency (conduction and instruments used), side dominance (bilateral or unilateral), morphometric data [SEF diameter, distances SEF-Foramen ovale (FO) and SEF-Foramen spinosum (FS)], and the methodology used for the morphometric measurements (caliper, DICOM Viewer, and image analysis software) on the estimated prevalence. RESULTS: In total, 6,460 subjects from 26 studies were included in the meta-analysis. The overall SEF prevalence was estimated as 38.1%. The heterogeneity was high and statistically significant. No indications of publication bias and small-study effect were identified. The conducted subgroup analyses did not yield statistically significant differences in the SEF prevalence between groups, except of the type of side dominance. Both results of the univariable and multivariable regression analyses showed the association of the unilateral dominance with a decrease in the reported SEF prevalence. CONCLUSION: The identification of more unilateral than bilateral foramina in a given cohort is associated with a decrease in the reported crude SEF prevalence. Laterality-specific estimates should be established for a precisive estimation of the emissary foramina prevalence.

Median artery persistence in coexistence with a bifid median nerve and interconnections of the median with the ulnar nerve and vice versa.

PURPOSE: This report describes a bilateral persistent median artery (PMA) originating from the ulnar artery and terminating at different levels of the upper limb. The PMA coexisted with a bilateral bifid median nerve (MN) and two bilateral interconnections (ICs characterized with the symbol -) of the MN with the ulnar nerve (UN) (MN-UN) and a unilateral reverse IC (UN-MN). Emphasis was given to the artery's developmental background. METHODS: The PMA was identified in an 80-year-old formalin-embalmed donated male cadaver. RESULTS: The right-sided PMA terminated at the wrist, posterior to the palmar aponeurosis. Two neural ICs were identified: the UN joined the MN deep branch (UN-MN), at the forearm's upper third, and the MN deep stem joined the UN palmar branch (MN-UN), at the lower third (9.7 cm distally to the 1st IC). The left-sided PMA ended in the palm giving off the 3rd and 4th proper palmar digital arteries. An incomplete superficial palmar arch was identified by the contribution of the PMA, radial, and ulnar arteries. After the MN bifurcation into superficial and deep branches, the deep branches formed a loop, that was penetrated by the PMA. The MN deep branch communicated with the UN palmar branch (MN-UN). CONCLUSIONS: The PMA should be evaluated as a causative factor of carpal tunnel syndrome. The modified Allen's test and the Doppler ultrasound may detect the arterial flow and the angiography may depict the vessel thrombosis in complex cases. PMA could also be a "salvage" vessel for the hand supply, in radial and ulnar artery trauma.

An unusual combination of a bilateral aberrant suprascapular artery with neurovascular structures variants.

PURPOSE: The report describes a bilateral suprascapular artery (SPSA) of atypical origin in coexistence with neurovascular aberrant structures. METHODS: The variants were identified in a 91-year-old formalin-embalmed male cadaver, derived from a body donation program after a signed informed consent. RESULTS: The left-sided SPSA emanated from the 1st part of the axillary artery, coursed between the brachial plexus lateral and medial cords, accompanied by the suprascapular nerve, and passed below the superior transverse scapular ligament. Ipsilateral coexisted variants were the lateral thoracic artery multiplication, the subscapular trunk formation, and the musculocutaneous nerve duplication. In the right supraclavicular area, a SPSA duplication was identified. The main artery emanated from the thyrocervical trunk in common with the transverse cervical artery and the accessory SPSA emanated from the dorsal scapular artery. Both SPSAs coursed over the superior transverse scapular ligament, while the suprascapular nerve ran below the ligament. CONCLUSIONS: The current study reported a bilateral aberrant SPSA, originating from the AA 1st part (left side) and from the dorsal scapular artery (right side), which coexisted with adjacent neurovascular structures' variants. The left SPSA atypically coursed below the superior transverse scapular ligament. Such an unusual combination of variations, present bilaterally in the current study, may be challenging for radiologists and surgeons.

Coracobrachialis muscle morphology and coexisted neural variants: a cadaveric case series.

PURPOSE: The current cadaveric case series evaluates the coracobrachialis muscle morphology, the related musculocutaneous nerve origin, course, and branching pattern, as well as associated adjacent neuromuscular variants. MATERIALS AND METHODS: Twenty-seven (24 paired and 3 unpaired) cadaveric arms were dissected to identify the coracobrachialis possible variants with emphasis on the musculocutaneous nerve course and coexisted neural variants. RESULTS: Four morphological types of the coracobrachialis were identified: a two-headed muscle in 62.96% (17/27 arms), a three-headed in 22.2% (6/27), a one-headed in 11.1% (3/27), and a four-headed in 3.7% (1 arm). A coracobrachialis variant morphology was identified in 37.04% (10/27). A three-headed biceps brachii muscle coexisted in 23.53% (4/17). Two different courses of the musculocutaneous nerve were recorded: 1. a course between coracobrachialis superficial and deep heads (in cases of two or more heads) (100%, 24/24), and 2. a medial course in case of one-headed coracobrachialis (100%, 3/3). Three neural interconnections were found: 1. the lateral cord of the brachial plexus with the medial root of the median nerve in 18.52%, 2. the musculocutaneous with the median nerve in 7.41% and 3. the radial with the ulnar nerve in 3.71%. Duplication of the lateral root of the median nerve was identified in 11.1%. CONCLUSIONS: The knowledge of the morphology of the muscles of the anterior arm compartment, especially the coracobrachialis variant morphology and the related musculocutaneous nerve variable course, is of paramount importance for surgeons. Careful dissection and knowledge of relatively common variants play a significant role in reducing iatrogenic injury.

A rare bilateral variant of the coracobrachialis muscle with supernumerary heads and coexisted variant branching patterns of the brachial plexus and the axillary artery.

PURPOSE: The study report describes a rare bilateral variant of a six- and five-headed coracobrachialis muscle (CB). The musculocutaneous nerve (MCN) (bilaterally) and the median nerve (MN) lateral root (unilaterally) pierced CB heads, separating superficial from deep heads. METHODS: The variant bilateral CB was identified in a 78-year-old formalin-embalmed male cadaver, derived from a body donation program after a signed informed consent. RESULTS: At the right side: The 6-headed CB was pierced by the MCN, while the MN lateral root pierced the one superficial and deep head. CB was supplied by the lateral cord and the MCN. At the left side: A 5-headed CB was identified with three superficial distinct origins that fused into a common superficial head coursing anterior to MCN. The variant CB bilaterally (with 11 heads in total) coexisted with a MN variant formation, an atypical course of the MN lateral root through CB (right side), a connection of the MN lateral root with the MCN (left side) and a variant axillary artery branching pattern (bilaterally). CONCLUSIONS: Course and direction of the accessory CB heads may occasionally entrap the MCN and/or adjacent structures (brachial artery and MN). The MCN compression results in problems in the glenohumeral joint flexion and adduction, and tingling or numbness of the elbow joint, the forearm lateral parts and the hand.