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.

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.

Unilateral accessory brachialis muscle and its functional significance: a case report of rare variation.

Variations of the brachialis muscle are uncommon in the literature. During regular cadaveric dissection, we observed the unilateral presence of an accessory muscle in the front of the right arm of a female cadaver, taking its origin from the medial aspect of the brachialis and the adjacent intermuscular septum. The muscle belly descended downwards, crossed the neurovascular bundle in the cubital fossa and merged with the fibres of the pronator teres. There is no doubt regarding its significance in the etiogenesis of numerous compression syndromes due to its close topographical relationship with the neurovascular bundle. In our report, we consider the potential developmental process and therapeutic implications of this variation, which can aid surgeons in their strategy and management.

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.

A very rare case of a thoracobrachialis muscle.

The anterior arm compartment includes the biceps brachii muscle, brachialis muscle, and coracobrachialis muscle, and they are characterized by different morphological variations. During standard anatomical dissection of right upper limb, an variant muscle was found. It originated from the fascia covering the long head of biceps brachii and from the tendon of pectoralis major muscle. It also connected to the brachial fascia. It also demonstrated a long thin tendon which was distally attached to the medial epicondyle of humerus. Knowledge about the morphological variations in this region is clinically important because of their direct correlation with neurovascular structures, which may lead to pathologies such as tingling, muscle weakness, paresthesia, and loss of sensation.

A new variety of chondrocoracoideus muscle, or an additional head of pectoralis major muscle.

The pectoralis major and pectoralis minor muscles are located in the anterior chest wall. This region is characterized by high morphological variability. During dissection an additional muscle was found, originating from the lateral border of the pectoralis major muscle. After fusion it passed into the tendinous part coursing under the insertion of the pectoralis major muscle, then formed a common junction with the short head of the biceps brachii muscle, the distal attachment of which is on the coracoid process. Such an accessory structure could lead to neurovascular compression and cause thoracic outlet syndrome, of which pain is usually the first symptom. This muscle has not been described in the literature so far and for that reason we can name the present case as an unique structure.

Comparison of Preoperative MRI With Intraoperative Findings for Peroneal Tendon Pathologies.

Magnetic resonance imaging (MRI) is commonly used to evaluate soft tissue pathology of the foot and ankle. Prior investigations have reported limitations of this modality, however, in evaluation of pathologies related to the peroneal tendons. This article investigates the correlation of pre-operative MRI studies with intraoperative findings. Five board-certified radiologists interpreted MRIs of 80 ankles that subsequently underwent surgical procedures performed by one board-certified foot and ankle surgeon, after which comparison was made between their findings. Statistically significant disagreement was found between radiologist and surgeon findings of a normal peroneus brevis (PB), PB and peroneus longus (PL) tendinosis, PB and PL hypertrophy, PB and PL partial linear tears, PB and PL flattening, PB longitudinal split tears, and the PB attritional spectrum (combined analysis of flattening, partial linear tearing, and longitudinal split tears). These results suggest that given the disconcordance between MRI and intraoperative findings, surgeons should remain cautious in their reliance upon this imaging modality when evaluating this anatomic region.

Quads or quins? Atraumatic restricted knee flexion due to accessory quadriceps bands in children.

BACKGROUND: Recent anatomical investigations have emphasized the variability in the knee extensor apparatus, with particular attention to a fifth component of the quadriceps femoris termed the tensor vastus intermedius or accessory "quinticeps femoris." Disorders of this structure have not been described in the pediatric imaging literature. OBJECTIVE: To review the clinical features, pathoanatomy and imaging findings of children presenting with derangement of the accessory quadriceps femoris, with a particular emphasis on the utility of early magnetic resonance imaging (MRI) of the thigh. MATERIALS AND METHODS: This is a retrospective analysis of 3 children, ages 3-10 years at presentation, who underwent imaging evaluation with subsequent surgically proven accessory quadriceps femoris muscles. Their clinical histories, including duration of symptoms, MRI findings, intervention and surgical outcomes, are reported. RESULTS: All patients presented with progressive unilateral restricted knee flexion and had multiple imaging studies targeting the knee before diagnosis. Diagnosis in all patients was made on MRI of the thighs, which demonstrated a fusiform low signal intensity structure with muscle-like architecture arising from the anterior or anterolateral proximal femur and blending with the common quadriceps tendon distally. All patients underwent surgical release of the anomalous band with significant functional improvement. CONCLUSION: In cases of progressive limited knee flexion without intrinsic pathology, an accessory quadriceps muscle should be considered as an extrinsic cause. Our experience demonstrated this to be readily identifiable on MRI, with symptomatic improvement following surgical release. Early recognition of this condition should prevent unnecessary intervention such as knee arthroscopy and the debilitating loss of flexion due to delayed diagnosis.

Finger abduction as a novel function of the extensor digitorum brevis manus muscle.

A 25-year-old female presented with a chronic scapho-lunate ligament injury with development of carpal instability requiring reconstruction. During a standard dorsal longitudinal mid-line approach to the carpus, an extensor digitorum brevis manus (EDBM) muscle was found taking its origin from the dorsal wrist capsule overlying the lunate with innervation from the posterior interosseous nerve (PIN). Electrical stimulation of the muscle belly demonstrated abduction of the middle finger. The EDBM is a rare anatomical variant of the extensor compartment of the wrist and may be encountered during surgical approaches. Where possible these variant muscles should be carefully dissected off underlying structures, preserved and repaired at the conclusion of a procedure to ensure no perceived functional deficit to the patient. We present a case of a previously undescribed EDBM muscle function of pure finger abduction with no extension and a surgical technique of preserving its origin. We propose that the middle finger variant of the EDBM should be re-named the extensor digitorum brevis medius to reflect our findings.

Flexor carpi radialis brevis: a rare accessory muscle presenting as an intersection syndrome of the wrist.

The flexor carpi radialis brevis (FCRB) is a rare accessory muscle of the forearm and wrist. It is typically asymptomatic, but has been discovered either incidentally during cadaveric studies or at the time of surgery in patients with distal forearm injury. Rarely, the FCRB muscle is associated with pain. We report a patient with wrist pain related to intersection between the tendon of the FCRB muscle and the tendon of the flexor carpi radialis (FCR) muscle, with an associated longitudinal split tear of the FCR tendon, documented by magnetic resonance imaging (MRI). To our knowledge, this is only the second report in the English literature of this intersection syndrome.

A unique case of an accessory sartorius muscle.

The sartorius muscle (SM) is a long strap muscle originating from the anterior superior iliac spine and inserting onto the medial surface of the proximal tibia. It crosses the anterior compartment of the thigh obliquely and descends towards the medial aspect of the knee. We found an accessory sartorius muscle (ASM) from the inguinal ligament and an original SM bifurcated into medial and lateral heads. The ASM merged with the medial head of the SM and inserted on the medial aspect of the tibia as the pes anserinus. The lateral head of the SM continued inferiorly and inserted on the medial aspect of the patella. We report a unique variation in the morphology of the SM, and discuss its functional and clinical implications.

Two accessory muscles of leg: potential source of entrapment of posterior tibial vessels.

Accessory muscles can be found in any part of the body. In most of the regions, they go unnoticed. However, in some cases, they become symptomatic or of cosmetic concern. In this particular case, the presence of two accessory muscle slips was observed in the flexor compartment of the leg. Among the two, the first accessory muscle belly connected the lower part of flexor hallucis longus to the tibialis posterior. The muscle crossed superficial to the posterior tibial vessels. The second accessory muscle took origin from the connective tissue around the lower part of the posterior tibial vessels and was inserted to the upper part of the lateral border of tibia near the attachment of the interosseous membrane. One of the accessory muscles crossed the posterior tibial vessels, while the other surrounded them. The above accessory muscles were supplied by the branches of tibial nerve.

Langer's axillary arch: a frequent but rarely discussed anatomical variant in the radiologic literature.

The axillopectoral muscle is a rarely discussed variant of muscular anatomy of the axilla, with various clinical implications. We report a case of a 7-year-old girl with multiple genetic and developmental abnormalities who presented with asymmetrical right axillary bulging of unknown etiology. MRI demonstrated a small accessory axillary muscle, known as Langer's axillary arch and/or the axillopectoral muscle. Other than soft-tissue asymmetry, the patient experienced no additional related symptoms. However, this is an important variant to be aware of, as it can easily be discovered on imaging and may be a causative agent for various upper extremity symptoms that may resolve with appropriate recognition and surgical intervention.

[Normal variants and pitfalls at the elbow joint]. / Normvarianten und Pitfalls rund um den Ellenbogen.

The elbow joint is comprised of three different bones with a combined hinge and a ball joint. Several nerves, tendons and muscles cross the joint. Anatomical variations at the elbow are common and may be the cause of certain pathologies. Despite the high quality of modern cross-sectional imaging, certain normal findings on CT or MRI have the risk of being misinterpreted. This article describes more common but also rare, normal variants around the elbow joint. Classic pitfalls are illustrated and compared to similar pathological findings.

The prevalence and characteristics of the subclavius posticus muscle in the adult population on MRI.

PURPOSE: The subclavius posticus muscle (SPM) is an aberrant muscle, and the presence of the SPM has a clinical significance, since the SPM might lead to thoracic outlet syndrome (TOS). To date, no radiological study has been evaluated the prevalence of the SPM in the adult population. In this study, we aimed to assess the prevalence of the SPM using magnetic resonance imaging (MRI). METHODS: We retrospectively reviewed brachial plexus, neck, and thoracic MRI of the patients who underwent MRI for various pathologies. Only the patients whose MRI examinations did not have sufficient image quality and the patients who had any pathology that directly involved the thoracic outlet region were excluded from the study. The observers assessed images in the coronal plane to detect the presence of the SPM. The thickness of the muscle and the distance between the SPM and brachial plexus were also noted. RESULTS: MRI examinations of 350 patients, 174 males and 176 females, were evaluated. SPM was detected in 29 patients (8.3%). In 6 patients (1.7%), we identified bilateral SPM. The mean thickness of the muscle was 6.10 ± 1.60 mm (range 2.5-10 mm). In 21 sides (60%), the brachial plexus and SPM were touching each other. In the remaining 14 sides (40%), the mean distances between the SPM and brachial plexus were 2.32 ± 0.62 mm (range from 1.7 to 3.6 mm). CONCLUSIONS: We conducted the first radiological study that evaluated the prevalence of the SPM, and we also assessed the thickness of the SPM and the distance between the SPM and brachial plexus. We highlight that our study might be accounted as a first step for future studies to assess the role of the SPM in TOS.

A rare accessory muscle in the hand--the flexor digitorum superficialis indicis.

Accessory muscles are easily overlooked during imaging evaluation. Although usually discovered incidentally, they are occasionally symptomatic. With increasing utilization of cross-sectional imaging, the radiologist should be prepared to readily identify these anomalous muscles. It is particularly important to distinguish these anatomical variants from soft-tissue tumors prior to invasive intervention, reserving biopsy and surgery for children who are symptomatic. This report discusses a case of a flexor digitorum superficialis indicis muscle, an extremely rare but well-described accessory muscle, presenting as a painful mass in a 15-year-old girl. The report includes the clinical presentation, radiologic findings, and the significance to management.

MRI of the tibioastragalus anticus of Gruber muscle: a rare accessory muscle and normal anatomical variant.

We present the case of a 31-year-old man who sustained a hyperplantar flexion injury of his right ankle, and was evaluated using computed tomography and MRI to assess for osseous and ligamentous injury. The MRI and CT studies demonstrated a tibioastragalus anticus of Gruber (TAAG) muscle in the lower limb's anterior compartment. To our knowledge, the imaging of this muscle has not been previously described. The TAAG muscle arises from the lower third of the anterolateral tibia and the interosseous membrane. Its tendon passes laterally, deep to the tibialis anterior and extensor hallucis longus tendons, and inserts onto the anterior superolateral neck of the talus in a fan-like manner. Knowledge and recognition of this tendon are important for both diagnostic accuracy and surgical planning, and could potentially be used as a tendon transfer or graft in the appropriate clinical setting. The presence of this accessory muscle should not be confused with a pathological condition.

Challenges in management of congenital enophthalmos due to anomalous accessory orbital extraocular muscle bands.

INTRODUCTION: Congenital enophthalmos is a rare condition characterized by posterior displacement of the globe, often associated with bony orbital anomalies or whole globe development defects. The purpose of this report is to present two unrelated cases of congenital enophthalmos secondary to anomalous accessory orbital bands and to describe characteristics of orbital imaging that differentiate this condition from the other causes. METHODS: The case records of two patients who presented with congenital enophthalmos and were discovered to have anomalous accessory orbital extraocular muscle bands were reviewed. The clinical features, initial diagnosis, high resolution magnetic resonance imaging (MRI) findings, and surgical outcomes were noted. A 3-dimensional reconstruction model was used to understand the approach and surgical management in one of the cases. RESULTS: Both patients presented with unilateral severe enophthalmos, globe retraction, and restricted ocular motility in all directions since birth. High-resolution MRI of the orbits revealed a short anomalous band, isointense to the muscle, arising from a rectus muscle belly and attaching to the posteroinferior part of the globe adjacent to the optic nerve. The caliber of the extraocular muscles and ocular motor nerves was normal. In one patient, surgery was not pursued due to the extreme posterior location of the band with proximity to the optic nerve. In the other patient, the deviation did not improve, despite successfully severing the accessory band, due to extensive scarring. CONCLUSION: Anomalous accessory orbital extraocular muscle bands are a rare and often overlooked cause of congenital enophthalmos when associated with limited ocular motility. Imaging the orbit can aid in diagnosis and help differentiate it from other causes. Safe surgical approaches to address the problem are limited, and available approaches may not be effective. These two cases highlight that the management of accessory extraocular muscle bands causing enophthalmos can be extremely challenging and difficult to improve even with intensive surgical intervention.

The brachioradialis longus: an unreported accessory form of the brachioradialis muscle.

The brachioradialis muscle (BR) belongs to the lateral forearm muscle. Typically, the radial nerve innervates it. BR morphological variability, such as split muscular belly, split tendon, or accessory BR (ABR), has been described in the current literature. A 68-year-old female donated cadaver was routinely dissected for research and educational purposes. A variant muscle was identified extending at the right arm's lateral and forearm compartments. It originated from the humerus lateral surface between the deltoid and the triceps brachii lateral head, joined the second muscular head from the brachialis muscle, and inserted into the radius styloid process. According to its origin, course, and insertion, the variant muscle probably corresponded to the BR accessory form. However, in the current literature, the ABR morphology corresponds to an accessory muscle originating adjacent to the typical BR and inserted into the radial tuberosity. At the same time, it was defined as "brachioradialis brevis." In the current case, the variant muscle differed significantly from the current literature due to the origin, insertion, length, and relationship with the typical BR; therefore, the term "brachioradialis longus" seemed adequate to describe this variant muscle.

An accessory muscle of flexor digitorum profundus with bipennate first lumbrical: a unique variation of clinical significance.

During the deep dissection of the front of the forearm, an anomalous accessory muscle in relation to the flexor digitorum profundus (FDP) muscle was observed in the right forearm. The accessory muscle consisted of a spindle-shaped muscle belly with a long tendon underneath the flexor pollicis longus muscle. When followed distally, the accessory muscle tendon was found lateral to the FDP tendon for the index finger and entered the palm deep to the flexor retinaculum. In the palm, we encountered the first lumbrical muscle as a bipennate muscle taking origin from the adjacent sides of the middle of the tendons of FDP and accessory muscle tendon. After giving origin to first lumbrical muscle, the accessory muscle got merged with the tendon of FDP for index finger. Understanding this kind of variation is required for radiologists and hand surgeons for diagnostic purposes and while performing corrective surgical procedures.