Does the articularis cubiti muscle really exist? Anatomical, histological, and magnetic resonance imaging study with a narrative review of literature.

Although the term articularis cubiti muscle is incorporated in the official anatomical nomenclature, only sparse data about its appearance are available. It is usually described as few fibres originating from the medial head of the triceps brachii muscle and inserting to the capsule of the elbow joint. However, the most recent observations regarding the morphological relations in the posterior elbow region point towards the absence of a well-defined muscle. Therefore, this study was designed to verify the existence of the articularis cubiti muscle in question and to compile more data on the topographical features of the subtricipital area near the posterior aspect of the elbow. To address these questions, 20 embalmed upper limbs were dissected, and seven samples were collected for histological analysis. The laboratory findings were then correlated with 20 magnetic resonance imaging (MRI) scans of the elbow. Consequently, a narrative review of literature was performed to gain more information on the discussed muscle in a historical context. Upon the anatomical dissection, muscular fibres running from the posterior aspect of the shaft of the humerus to the elbow joint capsule and olecranon were identified in 100% of cases. Histologically, the connection with the joint capsule was provided via winding bands of connective tissue. On MRIs, the muscular fibres resembled a well-demarcated thin muscle located underneath the medial head of the triceps brachii muscle. Combined with the review of literature, we concluded that the constant articularis cubiti muscle originates from the posterior shaft of the humerus and attaches indirectly to the posterior aspect of the elbow joint capsule and directly to the superior portion of the olecranon. The obtained results slightly differ from the modern description, but are in agreement with the original publication, which has become misinterpreted throughout time. Presumably, the misused description has led to questioning the existence of an independent muscle. Moreover, our findings attribute to the articularis cubiti muscle, a function in pulling on the posterior aspect of the elbow joint capsule to prevent its entrapment, and possibly also a minor role in extension of the forearm. The presented results should be taken into consideration when intervening with the posterior aspect of the elbow joint because the articularis cubiti muscle poses a consistently appearing landmark.

Fracture of an aberrant os styloideum: a unique case report.

Several accessory bones can be found around the wrist, which may pose a diagnostic challenge. Hereby, we report a unique case of a traumatic fracture of an aberrant os styloideum in a 66-year-old male. The patient presented with a swollen dominant right hand and a hematoma on its anterior and posterior aspects, as a result of a fall on an outstretched hand. The diagnosis was based on a CT scan, which showed a fractured accessory bone between the distal portion of the capitate bone and the base of the third metacarpus. Due to its typical location, the ossicle was identified as os styloideum. The patient was treated conservatively and the symptoms subsided on a short forearm cast after 2 weeks. At a 12-month follow-up, no other episodes were declared. Strong anatomical knowledge and sharing of such cases is essential for proper diagnosis and treatment of this very rare condition.

Os supratrochleare anterius: a very rare clinical case and review of literature.

PURPOSE: The accessory bones around the elbow are very rare variant structures, present in approximately 0.7% of cases. They can cause diagnostic problems and can be mistaken for pathological structures, especially when pain and limitation of elbow movements are present and a trauma can be traced in the patient's history. They are of different nature, either presenting within muscle tendons as sesamoids (brachialis and triceps brachii muscles) or presenting intra-articularly probably as separated or accessory ossification centres. The least common is the os supratrochleare anterius. METHODS: We present a case of a young male, featuring chronic blocking and 20° limited flexion of his right elbow, which bothered him during his occupation as a locksmith. In history, he suffered minor trauma to the elbow 20 years ago. X-ray and CT showed a large ossicle in the coronoid fossa of the humerus. RESULTS: The ossicle was surgically extracted in small pieces. The patient left satisfied with no mention of complaints. CONCLUSION: The os supratrochleare anterius is a very rare accessory bone of the elbow, located in the coronoid fossa of the humerus which can mimic many pathological states, and limit movements and causing pain around the elbow.

Anatomy of the iliopsoas notch and its relationship with morphology of the proximal femur.

PURPOSE: Discrepancy between the morphology of the acetabular margin and the design of hemispheric acetabular cups used in total hip arthroplasty may produce postoperative hip pain due to an iliopsoas impingement at the iliopsoas notch. This study aimed to determine the anatomical features of the iliopsoas notch in the Central European sample, and to test whether the morphology of the proximal femur affects the size of the iliopsoas notch. METHODS: The sample was composed of 40 matched pairs of dry hip bones and corresponding femora. The depth and length of the iliopsoas notch were measured and correlated with the available demographic data. The anthropometric parameters of the proximal femur were calculated using image-analysis software, and their association with the measurements of the iliopsoas notch was tested. RESULTS: The iliopsoas notch was present in all specimens and featured four morphological configurations: curved (61.3%), angular (16.2%), irregular (16.2%), and straight (6.3%). Its size was found to be larger in males (P = 0.014 for depth, P < 0.001 for length). No significant difference existed between the sides. The height and age of the specimens did not correlate with the size of the iliopsoas notch. Furthermore, neither the femoral neck version, the lesser trochanteric version, nor the angle between the neck of the femur and the lesser trochanter influenced the dimensions of the iliopsoas notch. CONCLUSION: The iliopsoas notch is a consistent landmark of the acetabulum, although its anatomical appearance is widely variable. The iliopsoas notch arrangement cannot be predicted perioperatively based on the morphology of the proximal femur. The various shapes and sex-related differences detected in this study could be used for designing new hip implants or could be utilized during cup positioning in total hip arthroplasty.

Osseous variability around the elbow joint.

There are many osseous variants that occur around the elbow joint such as supracondylar process, supratrochlear foramen, accessory ossicles, and others. Scientific databases were searched for variants around the elbow joint. Elbow radiographs from our center demonstrating some of these findings were included in the study. The aim of the present review was to provide comprehensive information on the terminology, prevalence, history, etiology, and clinical importance of these variants. These anatomical variants are important for radiologists while interpreting radiographs, computed tomography, and magnetic resonance imaging for trauma and orthopedic surgeons during osteosynthesis at the distal humerus, proximal ulna, and radius.

Scoping review of the palmaris profundus muscle: anatomy of a rare variant and its role in carpal tunnel syndrome.

The palmaris profundus muscle is a rare anatomical variation of the forearm muscles. It has been described in both cadaveric and clinical studies as a possible cause of carpal tunnel syndrome. We observed three cases of this variant in recent years and decided to perform a scoping review of this uncommon anatomical entity. Major databases were searched to identify all relevant clinical and anatomical studies containing anatomical descriptions of the muscle, including its origin, insertion, and concomitant presence of the proper palmaris longus muscle or the bifid median nerve. In clinical cases, we studied the surgical approach. Sixty-four articles met our inclusion criteria and contained 88 cases of palmaris profundus muscle. The most common origin was the ventral aspect of the radius in the area of insertion of the pronator teres muscle observed in 11 cases (12.5 %). We found 65 cases (73.3%) in which the tendon was inserted into the palmar aponeurosis or palmar fascia after entering the carpal canal. The concomitant presence of the proper palmaris longus muscle was described in 47 cases (53.4%). We identified 10 cases (10.8%) of the bifid median nerve. In 49 of 69 clinical cases (71%), the surgical approach was to resect the variant muscle. The importance of this variant should not be underestimated due to its potential to compress the median nerve. We found a significant disparity in the muscle origin sites, but uniformity of muscle insertion. In cases where the muscle is found during carpal canal surgery, it should be partially resected to ensure complete nerve decompression.

Osseous variations associated with physiological thinning of the glenoid articular cartilage: an osteological study with CT, MRI and arthroscopic correlations.

OBJECTIVE: To investigate the relationship between osseous variations of the glenoid fossa and thinning of the overlaying articular cartilage. MATERIALS AND METHODS: In total, 360 dry scapulae, comprising adult, children and fetal specimens, were observed for potential presence of osseous variants inside the glenoid fossa. Subsequently, the appearance of the observed variants was evaluated using CT and MRI (each 300 scans), and in-time arthroscopic findings (20 procedures). New terminology of the observed variants was proposed by an expert panel formed by orthopaedic surgeons, anatomists and radiologists. RESULTS: Tubercle of Assaky was observed in 140 (46.7%) adult scapulae, and an innominate osseous depression was identified in 27 (9.0%) adult scapulae. Upon radiological imaging, the tubercle of Assaky was found in 128 (42.7%) CTs and 118 (39.3%) MRIs, while the depression was identified in 12 (4.0%) CTs and 14 (4.7%) MRIs. Articular cartilage above the osseous variations appeared relatively thinner and in several young individuals was found completely absent. Moreover, the tubercle of Assaky featured an increasing prevalence with aging, while the osseous depression develops in the second decade. Macroscopic articular cartilage thinning was identified in 11 (55.0%) arthroscopies. Consequently, four new terms were invented to describe the presented findings. CONCLUSION: Physiological articular cartilage thinning occurs due to the presence of the intraglenoid tubercle or the glenoid fovea. In teenagers, the cartilage above the glenoid fovea may be naturally absent. Screening for these variations increases the diagnostic accuracy of glenoid defects. In addition, implementing the proposed terminological updates would optimize communication accuracy.

Prevalence of the anterosuperior capsulolabral anatomical variations and their association with pathologies of the glenoid labrum: a systematic review and meta-analysis.

PURPOSE: Differentiating the anatomical variations of the anterosuperior portion of the glenoid labrum from pathologies is important to avoid unnecessary iatrogenic complications resulting from inaccurate diagnosis. Additionally, the presence of several variations was reported to be conductive to lesions involving the glenoid labrum. Thus, the aim of this study was to state the prevalence rates of the sublabral recess, sublabral foramen, and the Buford complex, and to verify their association with labral lesions. METHODS: Systematic search of electronic databases was conducted to gain potentially eligible literature. Suitable studies were selected in a two-round screening, and relevant data were subsequently extracted. Calculation of the pooled prevalence estimates, including sub-analyses on cohort size, study type, and geographical variance, was conducted. Pooled analysis of risk ratios (RR) was used to assess the conductive nature of the discussed variants to superior labrum anterior to posterior (SLAP) lesions. RESULTS: The screening resulted in selection of 20 studies investigating the morphological features of the glenoid labrum, consisting of 7601 upper limbs. On the bases of random-effects meta-analysis the sublabral recess, sublabral foramen and Buford complex occur with a pooled prevalence of 57.2% (95% CI 30.0-84.4%), 13.5% (95% CI 8.2-18.9%), and 3.0% (95% CI 1.5-4.5), respectively. Moreover, individuals with Buford complex have RR 2.4 (95% CI 1.3-4.7) of developing SLAP lesions, especially type II (95.5%; 95% CI 86.1-100%), whereas such risk for sublabral recess and sublabral foramen was not statistically significant. CONCLUSION: Morphological variants of the glenoid labrum posing diagnostic confusion are frequently observed. Gradually, the Buford complex may be a predisposing factor for sustaining a SLAP lesion.

Anatomical variants complicating the posterior approaches towards the elbow joint.

INTRODUCTION: Anatomical variants observed during the posterior approach to the elbow joint require special attention due to their clinical relevance. We aim to present a compendious review of described variants potentially encountered during the posterior approach towards the elbow joint to the experts in the elbow surgery. METHODS: A narrative review of surgical and anatomical textbooks, as well as search of scientific databases was carried out. RESULTS: Variability of the subcutaneous nerves is important during incision planning. Accessory muscles such as dorsoepitrochlearis, chondroepitrochlearis, epitrochleoanconeus, subanconeus or supernumerary flexor carpi ulnaris may confuse even the senior surgeon during the dissection and possibly complicate the fracture reduction. Some bony variants such as supratrochlear foramen may lead to fracture or possibly interfere with the osteosynthesis placement. Accessory bones are also present in the region of the elbow joint. Those situated intra-articular may present with symptoms. CONCLUSION: Many variants can be encountered in the area of the elbow joint and their knowledge is essential to truly understand its anatomy. The presented review enables easier orientation in the current literature with the aim on the posterior approach towards the elbow joint.

An accessory muscle belly or an accessory muscle head? An unusual arrangement of muscles in the anterior compartment of the forearm.

PURPOSE: Knowledge of the unusual arrangement of the flexor pollicis longus (FPL) muscle is important as the variable tendon may be a rare cause of carpal tunnel syndrome. METHODS: During a routine dissection at the Department of Anatomy, an unusual formation of the FPL muscle was observed in a formalin embalmed Central European cadaver. RESULTS: This report presents a variation of the FPL muscle, where the muscle split and formed a separate accessory head inserting into the first lumbrical muscle. Moreover, a tendinous interconnection was present between the FPL muscle tendon and the tendon of the aberrant muscle head. CONCLUSION: The cases described by previous literature, concerning the Linburg-Comstock variation or the accessory head of the first lumbrical muscle originating from the FPL muscle, are closest to the present case. Such variation has a clinical significance ranging from the functional limitation of the thumb and index finger movement to the potential median nerve compression.

Accessory heads of the biceps brachii muscle: A systematic review and meta-analysis.

The anatomy of the biceps brachii muscle has been a subject of interest to many researchers. In particular, the presence of one or more accessory heads has been reported to be the most common variation of the biceps brachii muscle. In fact, contemporary knowledge is quite inconsistent and lacks a definitive summary. Taking this into account, the present study aims to investigate the overall prevalence of the accessory heads and related questions, such as their broad morphological features, population variance, sexual dimorphism, side distribution or the changes in prevalence rates over time. A literature search of major scientific databases was conducted and produced 78 eligible articles, including 10,603 upper limbs, for our study. Relevant data were extracted and consequently analysed with the use of random-effects meta-analysis. As a result, the accessory heads occur with an overall prevalence of 9.6% (95% CI 8-11%) and by far the most common is the presence of a single accessory head (8.4%; 95% CI 7-10%). Additional sub-analyses revealed that accessory heads appear more frequently unilaterally and in males. Differences between the occurrence on the right or left side were not significant. Moreover, a decreasing trend in prevalence rates over time was observed, pointing towards an evolutionary adaptation. The innervation and blood supply of the accessory heads are nearly identical to that of the normal biceps brachii muscle. Although the accessory heads are usually asymptomatic, their potential presence must be kept in mind while interpreting various conditions. In addition, their direct clinical importance is speculated and is thought that they might be conductive to several pathological processes around the shoulder girdle and brachial region. While many of the morphological and morphometric aspects of the accessory heads are well documented, their functional value is still a matter for future investigations.

The arcade of Frohse: a systematic review and meta-analysis.

PURPOSE: The structure of the proximal margin of the superficial layer of the supinator muscle is of high interest to many researches. Its tendinous appearance, called the arcade of Frohse, may be clinically important because of its close relationship to the deep branch of the radial nerve passing beneath it and is considered to be the cause of several syndromes. Given the importance of this structure, we aimed to provide a comprehensive and evidence-based review with meta-analytic techniques. MATERIALS AND METHODS: The meta-analysis was performed in adherence to the PRISMA guidelines. Three medical databases were searched in order to identify all potentially eligible articles. Included studies were assessed for quality and the extracted morphological and morphometric data from the relevant articles was analyzed with the use of random effects meta-analysis. RESULTS: A total of 20 studies were included into this meta-analysis. The pooled prevalence of the arcade of Frohse was calculated to be 66% within the adult population and 0% in the fetuses. Other variations regarding the arcade of Frohse were identified as very rare. Analysis of the morphometric parameters revealed the average proportions to be 23.22 mm for the length, 11.05 mm for the width and the mean thickness is 0.67 mm. CONCLUSIONS: The arcade of Frohse is a commonly found structure in adults and thoughtful knowledge of its texture and morphology is especially useful in neurology, neurosurgery, orthopedics, trauma surgery and hand surgery, because it is considered to be the most common source of compression for the deep branch of the radial nerve.

Accessory bones of the elbow: Prevalence, localization and modified classification.

Accessory bones in the region of the elbow are rare variants with high clinical significance as they may be confused with avulsion fractures. We investigated their prevalence and performed a statistical analysis to support their congenital origin. Their localization was mapped to show their exact site of occurrence. We evaluated anteroposterior and lateral X-ray images of 2413 elbows in a Central European population from which a group of accessory bony structures was selected. Their character was evaluated, and accessory bones were identified. We used logistic regression to evaluate the potential relationship between the occurrence of accessory bones, the age of patients, and the occurrence of calcar olecrani. The prevalence of accessory bones of the elbow in the sample was 0.77%. Our results did not show a statistically significant relationship with the occurrence of calcar olecrani or with the age of patients. The most common type was os subepicondylare mediale (type V) in 0.46%, which was located distal to the medial epicondyle of the humerus, followed by os subepicondylare laterale (type III; 0.21%), situated laterally to the lateral epicondyle of the humerus. In comparison with previous reports, os sesamoideum mediale (type IV) was located more distally. Our data suggest that congenital accessory bones are a rare entity. Knowledge of their exact localization should be considered during diagnosis of avulsion fractures and other unclear diagnoses including accessory bony structures in the elbow region.

Absence of flexor digitorum profundus muscle and variation of flexor digitorum superficialis muscle in a little finger: two case reports.

PURPOSE: Knowledge of rare variants of the FDP is of high clinical importance for physicians examining patients for tendon lacerations and especially for hand surgeons operating tendon injuries. METHODS: During routine dissection at our Department of Anatomy both cases were observed. RESULTS: Variations of flexor digitorum superficialis and flexor digitorum profundus muscles of the little finger were observed in two cadavers. In both cases, the flexor digitorum profundus muscle for the little finger was absent. Moreover, in the first case, the flexor digitorum superficialis muscle for the little finger was hypoplastic and in the second case it featured variable insertion. CONCLUSION: There were found only four cases in previous literature describing absent flexor digitorum profundus tendon without any muscle attachment to the base of the distal phalanx. Furthermore, all previously described cases were observed in living patients. To our best knowledge, a case report in cadaver has yet not been reported and is of high importance for hand surgeons examining the hand for tendon injuries.

The superficial anatomical landmarks are not reliable for predicting the recurrent branch of the median nerve.

PURPOSE: The variability of the recurrent branch (RB) of the median nerve lends itself to an increased risk of injury when performing the minimally invasive approach for carpal tunnel release without its direct visualization. This risk is less so when it is released via the more invasive open approach as the RB can be easily identified, but the drawback is that of longer postoperative patient recovery time. Therefore, performing these releases via the less invasive approach should be more favorable for patients providing it could be done safely. Hence with there being a positive link between the hypertrophy of the thenar musculature and the course of RB according to previous studies. METHODS: We dissected 28 hands of 14 donated bodies fixed using Thiel's method to try to demonstrate these findings of the associations among the RB, palmar creases and other superficial anatomical landmarks. Fisher's exact test was conducted to verify the relationship between those structures statistically. RESULTS: Statistically significant links were found between the type of the RB and the type of the palmar creases (p value = 0.0094) and between the RB type and the palmaris longus muscle presence (p value = 0.028). CONCLUSION: It was inferred that palmar creases and other superficial anatomical landmarks listed in the text could not be used to predict the variability of the RB and the choice of mini-invasive approach should not be based on their course.

Accessory flexor carpi ulnaris muscle with associated anterior interosseous artery variation: case report with the definition of a new type and review of concomitant variants.

PURPOSE: Knowledge of accessory flexor carpi ulnaris (AFCU) is not only important for proper orientation in the surgical field but it can be used for tendon transfer as well. AFCU commonly occurs with concomitant variants, and its presence should rise caution in order to prevent iatrogenic injury. METHODS: During a routine dissection for research data collection at the Institute of Anatomy, a AFCU with concomitant variants was observed in a European cadaver fixed with Thiel's method. A thorough review of the literature concerning all the encountered variants was performed. RESULTS: AFCU was found in the right upper limb with its insertion on the flexor retinaculum. Palmaris longus muscle was absent in this limb, and an accessory branch of the anterior interosseous artery coursed over the pronator quadratus muscle to anastomose with the ulnar artery 5 cm proximally to the pisiform. On the left hand, a variable lumbrical of the second finger originating from the flexor retinaculum was found, which was not described in the literature before. CONCLUSIONS: AFCU commonly occurs together with concomitant variants, and special attention is needed when performing surgery on such forearm.

Variations of the lumbrical muscles of the hand: Systematic review and meta-analysis.

PURPOSE: Lumbrical muscles of the upper limb belong to the middle group of intrinsic hand muscles. Their anatomical variability has been extensively studied with heterogeneous findings. Therefore, the aim of this study is to provide a systematic review and a meta-analysis of the lumbrical muscles variations in the human hand. METHODS: For this purpose, four major electronic databases were searched to identify eligible studies. Then, all relevant data were extracted, and statistical analysis performed. A new classification of lumbrical muscles variations is proposed to summarize and clearly define all described findings. We included 26 studies, making a total sample of 1340 dissected hands. FINDINGS: The most common variations for each muscle were an accessory belly for the first lumbrical muscle, a variable origin for the second lumbrical muscle, a variable innervation for the third lumbrical muscle and a variable insertion for the fourth lumbrical muscle with the prevalence 3.8%; 7.7%; 12% and 5.8%, respectively. CONCLUSIONS: We believe that results of our statistical analysis are suitable for both hand surgeons and other medical professionals dealing with hand injuries or functional problems in their daily routine.

Prevalence and anatomy of the anomalous subclavius posticus muscle and its clinical implications with emphasis in neurogenic thoracic outlet syndrome: Scoping review and meta-analysis.

BACKGROUND: The subclavius muscle runs underneath the clavicle. However, there have been a few reports of a duplicated subclavius muscle which is commonly referred to as subclavius posticus muscle due to its orientation being posterior to the proper subclavius muscle. Its occurrence seems to potentially create a narrowing interval at the superior thoracic aperture as it crosses over the brachial plexus. It might also have functional influence on the shoulder girdle. PURPOSE: To provide comprehensive gross anatomy description of the variant "subclavius posticus muscle" and to investigate its reported clinical implications with emphasis on its involvement in causing brachial plexus compression. BASIC PROCEDURES: A scoping review with meta-analysis of the gross anatomy of the subclavius posticus muscle was conducted along with investigating its correlation to the thoracic outlet syndrome. Forty-seven articles were pooled through two rounds of the selection process. The relevant information was extracted and meta-analyzed. MAIN FINDINGS: The scoping review and meta-analysis of the 47 articles revealed a total prevalence of 11/2069 (4.9%); 10/1369 (5.1%) in cadaveric studies, and 1/700 (5.0%) in MRI studies. The subclavius posticus muscle is a short triangular muscle with an average length of 12 cm and an average width of 1 cm. It originates from the sternal end of the first rib in most cases with reported variants of one case originating from the costoclavicular ligament and one case where it was fused with the proper subclavius muscle. Its insertion is more variable: on the superior border of the scapula with variable length in 71.35%, on the coracoid process of the scapula in 25.42%, and on the clavicle in 0.90%. The subclavian nerve seems to be the dominant nerve supply with a 57.6% prevalence, while 25.8% are innervated by the suprascapular nerve. Other reported nerves were the nerve to the myolohyoid (4.5%), accessory phrenic nerve (4.5%), and a direct branch from the brachial plexus (2.0%). The blood supply was reported (only once) to be from the suprascapular artery. However, the venous drainage was not established at all. PRINCIPAL CONCLUSIONS: The subclavius posticus muscle is a variant muscle occurring with a reported overall prevalence of 4.9%. It can compress the brachial plexus as it runs across at the space of the superior thoracic aperture with exquisite contact, and this can lead to a neurogenic thoracic outlet syndrome. It also can be involved in the vascular thoracic outlet syndrome. Lastly, it is important not to omit its potential influence in shoulder joint instability to some extent.

A meta-analysis on the anatomical variability of the brachial plexus: Part III - Branching of the infraclavicular part.

INTRODUCTION: The anatomy of the brachial plexus has been a subject of interest to many researchers over time resulting in an inconsistent amount of data. Previously, our team had published two evidence-based studies on the anatomical variations involving the brachial plexus, therefore the aim of this study was to analyze the findings regarding the infraclavicular part of the brachial plexus with the use of meta-analytic techniques to complete the comprehensive series. MATERIAL AND METHODS: Major scientific databases were extensively searched to compile anatomical studies investigating the morphology of the infraclavicular part of the brachial plexus. Extracted data were classified based on our proposed classification system and subsequently analyzed with the use of random effects meta-analysis to state the pooled prevalence estimates of the distinct variation patterns. RESULTS: A total of 75 studies (4772 upper limbs) were selected for the meta-analysis. The branches of the lateral cord, including the lateral pectoral nerve and musculocutaneous nerve, resembled their usual origin in 76.8% (95% CI 50-96%) and 98.8% (95% CI 98-100%), respectively. The medial pectoral nerve, medial brachial cutaneous nerves, medial antebrachial cutaneous nerve and ulnar nerve emerging from the medial cord were observed originating from their usual origins in 90.9% (95% CI 68-100%), 90.7% (95% CI 73-100%), 87.9% (95% CI 67-99%) and 97.7% (95% CI 94-100%), respectively. Lastly, nerves branching from the posterior cord, including the superior and inferior subscapular nerves, thoracodorsal nerve, axillary nerve and radial nerve, originated as per textbook description in 90.7% (95% CI 80-98%), 76.1% (95% CI 61-89%), 90.1% (95% CI 84-95%), 79.8% (95% CI 68-90%) and 99.0% (95% CI 96-100%), respectively. Moreover, the usual origin of the median nerve from the lateral and medial cord via the corresponding roots was encountered in 89.7% (95% CI 84-95%) of cases. CONCLUSIONS: The nerves originating from the infraclavicular part of the brachial plexus exhibit a wide spectrum of possible origins. However, the usual patterns were significantly the most common types present in more than three quarters of cases. Especially clinicians might profit from the enhanced understanding of the brachial plexus anatomy presented herein, since we offer a strong guide for handling the anatomically challenging pathologies in this specific area.