Osteopathy Journals and Research by Darren Chandler

 

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  1. Introduction

    Upper cervical headaches can have, in part, a distrtibution that shares a trigeminal nerve pain pattern. Chou and Lenrow (2002) identified C2 and C3 headache pain patterns as:

    • C2 dynatome (pain): pain ascending, 6-8 cm wide, paramedially from the subocciput to the vertex.
    • C3 dynatome: pain in the upper neck (<anterolateral), ear (<pinna), lateral cheek and angle of the jaw.

    Typically extracranial sources of trigeminal mediated pain are thought to be from a reflex involving several nerves that eventually involve a direct branch of the trigeminal nerve. For example an upper cervical nerve causing a neurological reflex via the spinal trigeminal nucleus.

    This end-stage physiological 'irritation' of the trigeminal nerve is in contrast to a direct mechanical compression that is usually associated with more pathological space occupying lesions.

    More recently Schueler et al (2013 & 2014) found branches from the trigeminal nerve that innervate the dura mater and regulate bloodflow intracranially can be compressed by extracranial  soft tissues. These nerves run a course originating intracranially to then traverse the cranium via the sutures and emissary canals to terminate extracranially. Extracranially these nerves innervate the connective tissue of the temporomandibular joint, periosteum and cervical muscles.

    This gives the potential for soft tissues of the head and neck to not only initiate a physiological reflex response but to exert a direct compression on the trigeminal nerve.

    Blake & Burnstein (2019) attributed these nerves to giving occipital pain that can radiate frontally to trigeminal innervated areas.

    Innervation of the dura

    Dura of the posterior cranial fossa

    The dura mater covering the posterior cranial fossa is innervated by the recurrent meningeal branches of the:

    • Vagus nerve.
    • Facial nerve.
    • Glossopharyngeal nerve (Lee et al 2017).
    • Hypoglossal nerve (Lv et al 2014)
    • Sphenopalatine ganglion (Lv et al 2014).
    • Upper three cervical nerves (Lee et al 2017).
    • C2-3 dorsal root ganglion: Noseda et al (2019) found, in rats, neurones in the C2-3 dorsal root ganglia innervated the dura of the posterior cranial fossa.

    Dura of the middle cranial fossa

    The dura mater of the middle cranial fossa is innervated by all three branches of the trigeminal nerve:

    • Opthalamic (V1): innervates the dura the full length of the middle cranial fossa. Posterior projections of this nerve (nervus tentorii) innervates the entire region of the tentorium cerebelli and the posterior part of the falx cerebri. Anterior projections of the recurrent meningeal branches of the opthalamic nerve innervate the dura in the anterior cranial fossa (Lee et al 2017).
    • Maxillary (V2): recurrent meningeal branches run parallel to the proximal part of the middle meningeal artery in the dura mater innervating the dura the full length of the middle cranial fossa (Lee et al 2017).
    • Mandibular (V3): recurrent meningeal branches run parallel to the proximal part of the middle meningeal artery in the dura mater innervates the dura in the posterior part of the middle cranial fossa (Lee et al 2017).

    Dura of the anterior cranial fossa  

    The dura of the anterior cranial fossa is innervated by the trigeminal nerve:

    • Opthalamic (V1).
    • Maxillary (V2).

    Extracranial projections of the dural innervation 

    Upper cervical nerves and C2-3 dorsal root ganglion

    There is a shared extracranial-intracranial innervation in the posterior cranial fossa involving the upper three cervical nerves and C2-3 dorsal root ganglion. 

    Schueler et al (2014) found in the nuchal region the trigeminal innervation territory to overlap considerably with that of the occipital nerves. The innervation of these pericranial muscles by collaterals of meningeal afferent fibers is substantial.

    For this reason Noseda et al (2019) proposed, not only can activation of extracranial muscle nociceptors cause headaches via their intracranial branches innervating the dura but also, in reverse, activation of intracranial dural nociceptors can give rise to extracranial muscle tenderness/pain.

    Recurrent meningeal branch of the trigeminal nerve (V3): spinosus nerve 

    The nerve that runs intracranially from the dura in the middle cranial fossa to extracranially in the periosteum and soft tissues is the spinosus nerve.

    This nerve originates from: trigeminal mandibular branch (V3) --> spinosus nerve (meningeal branch). It innervates the dura in the middle cranial fossa.

    Schueler et al (2014) identified this nerve as splitting into bundles. These bundles run within the dura mater along the middle meningeal artery. 10-20% of these bundles penetrate the skull through the sutures and along the emissary veins.

    These authors found the nerve leaves the skull around the petrosquamos fissure to reside around the squamous suture. These bundles of nerves not only innervate the periosteum but also the insertion of the temporalis muscle.

    Nerves fibers, unspecified as part of the spinosus nerve, in the posterior part of the cranial cavity also penetrate the petrosquamous fissure.

    Schueler et al (2014) hypothesised two clinical points to the spinosus nerve:

    • This nerve has Aβ‐fibers. These fibers normally have mechanoreceptive functions. Could these nerve fibers be activated by mechanical stimuli such as sudden head movements?
    • These authors also hypothesised that nerve fibers running with or parallel to the spinosus nerve may have a sympathetic or parasympathetic origin that can contribute to vascular functions. Scheuler et al (2013) found noxious stimulation of the pericranial muscles (including the temporalis where fibers from the spinosus nerve terminate extracranially) causes release of CGRP intracranially. This resulted in elevated meningeal blood flow. Vasodilation of the middle meningeal artery and neurogenic inflammation of the recurrent meningeal branches from the maxillary and mandibular divisions of the trigeminal nerve in the skull base have been suggested as causes of vascular headache (Lee et al 2017).

    Unspecified nerves in the anterior and posterior cranial fossa

    Schueler et al (2014) found extracranial projectons from other meningeal nerves that innervate the dura mater of the anterior and posterior cranial fossae.

    Nerves fibers of unspecified origin in the posterior part of the cranial fossae penetrate the petrosquamous fissure. This is along side nerve fibers from the spinosus nerve that penetrate the petrosquamous fissure having innervated the dura in the middle cranial fossa.

    Embryology of the dura, cranial sutures and brain

    Embryology of the dura and cranial sutures

    Reviewing the intimate embryological developmental relationship of the cranial sutures and dura can throw potential light on the origin of these nerves.

    Zhao and Levy (2014) postulated that these intrarcranial trigeminal afferents that cross the calvaria through the sutures and innervate the periosteum are important to the process of cranial suture closure during the early stages of cranial development. 

    Embryological relation of the sutures and the dura

    Jin et al (2016) found a small line of the neural crest is derived from mesenchyme that remains between the two parietal bones and contributes to the signalling system that governs growth of the cranial vault at the sutures and to the development of the underlying meninges.

    The mesoderm and neural crest cells don’t just form the bones of the skull but also the meningeal mesenchyme that forms all three layers of the meninges.

    It does this while the sutures are developing. The growing and expanding bone fronts both invade and recruit the intervening mesenchymal tissue into the advancing edges of the bone fronts. By this action the intervening bones separate the mesenchyme into an outer ectoperiosteal layer (to become the skull) and an inner dura mater.

    The outer layer of the dura forms the inner periosteum of the skull and the inner dura layer forms the dural folds (falx and tentorium).

    The dura mater also expresses osteogenic growth factors that may be required for ossification of cranial vault bones.

    The dura covers the brain. This dural covering has reflections acting as partitions of the cranial cavity under the calvarium, adopting a course that follows the main direction of the sutures. The folds are the falx and tentorium.

    They firmly attach to the skull base at the crista galli, the cribriform plate, the lesser wings of the sphenoid and the petrous temporal crests.

    The dura mater in conjunction with the falx cerebri and the tentorium cerebelli, come to define the zones where bone growth slows down and the coronal, lambdoid, and sagittal sutures develop.

    Oppermann (2000) found the dura mater was not only crucial in keeping the suture a flexible fibrous joint preventing them from being obliterated by bone but it was needed to stabilise the suture. It's not until the third decade of life that the cranial vault sutures ossify and until the seventh or eighth decade of life for the facial complex.

    Jin et al (2016) found these dural bands are essential in determining the shape of the brain as without them it would expand into a perfect sphere.

    The expanding brain, sending signals by means of the dura mater makes the cranium grow and expand by means of expanding the cartilaginous growth plates in the cranial base and making the sutures add more bone at their periphery in the cranial vault. Gagan et al (2007) found the cells of the dura mater not only have profound influence on cell migration and differentiation in the infant skull but also the brain.

    Therefore the growing brain does not actually push the bones outward. Rather, each flat bone is suspended, with the existent traction forces, within a widespread sling of the collagenous fibers of the enlarging inner (meningeal) and outter (cutaneous) periosteal layers. As these membranes grow in an ectocranial direction ahead of the expanding brain, the bones are displaced with them. This draws all of them apart, and the tensile physiological forces thus created are believed to be the stimulus that triggers the bone producing response.

    Embryology of the dura and brain

    These mechanical and biochemical factors aren't just related to the development of the skull but also the brain. The cells of the dura mater have a dynamic reciprocal influence on cell migration and differentiation in multiple regions of the embryonic and infant brain and skull (Gagan et al 2007)

    Innervation of the intracranial vasculature

    Of the autonomic nerve fibers that are strongly associated with the vascular bed, the sympathetic fibers from the SCG predominate whereas the parasympathetic fibers are less prominent (Fricke et al 2001). 

    Shimizu and Suzuki (2010) found the parasympathetic innervation of the dural sinuses to be:

    • Superior sagittal sinus: ethmoidal nerve (anterior) and tentorial nerve (posterior). Perivascular sympathetic fibers accompany the middle meningeal artery and build up a dense plexus around the sagittal sinus (Fricke et al 2001).
    • Inferior sagittal sinus: probably tentorial nerve.
    • Transverse sinus and straight sinus: tentorial nerve.
    • Superior petrosal sinus: tentorial nerve and V3 and fibers from the trigeminal ganglion.
    • Vein of Galen: tentorial nerve.

    The trigeminal nerve supplies the cranial dura mater. Two separate trigeminal nociceptive systems in the cranial dura mater have been distinguished (Lee et al 2017):

    • V1: Posterior projections of the recurrent meningeal branches of the ophthalmic nerve (nervus tentorii) innervates the distal middle meningeal artery on the lateral convexity. The most densely innervated areas are the transverse sinus and the posterior half of the straight sinus.  

    References 

    Cervicogenic Headache (2002) Larry H. Chou and David A. Lenrow

    Visualization of the tentorial innervation of human dura mater (2017). Shin‐Hyo Lee, Kang‐Jae Shin, Ki‐Seok Koh, Wu‐Chul Song

    Non-Trigeminal Nociceptive Innervation of the Posterior Dura: Implications to Occipital Headache (2019). Rodrigo Noseda, Agustin Melo-Carrillo, Rony-Reuven Nir, Andrew M. Strassman and Rami Burstein

    Extracranial projections of meningeal afferents and their impact on meningeal nociception and headache (2013). Schueler M, Messlinger KDux MNeuhuber WLDe Col R.

    Emerging evidence of occipital nerve compression in unremitting head and neck pain (2019). Pamela Blake & Rami Burstein 

    THE EMISSARY FORAMINA OF THE CRANIUM IN MAN AND THE ANTHROPOIDS (1930) BY G. I. BOYD

    Innervation of Rat and Human Dura Mater and Pericranial Tissues in the Parieto‐Temporal Region by Meningeal Afferents (2014). Markus Schueler, Winfried L. Neuhuber, Roberto De Col, Karl Messlinger

    The trigemino-cardiac reflex: an update of the current knowledge (2009). Schaller BCornelius JFPrabhakar HKoerbel AGnanalingham KSandu NOttaviani GFilis ABuchfelder M

    The sensory innervation of the calvarial periosteum is nociceptive and contributes to headache-like behaviour (2014). Jun Zhao and Dan Levy

    Development and Growth of the Normal Cranial Vault : An Embryologic Review (2016). Sung-Won Jin, Ki-Bum Sim, and Sang-Dae Kim

    Cranial sutures as intramembranous bone growth sites (2000). Lynne A. Opperman

    Cellular dynamics and tissue interactions of the dura mater during head development (2007). Jeffrey R. Gagan, Sunil S. Tholpady, Roy C. Ogle

    Innervation of the Cerebral Dura Mater (2014). Xianli LvZhongxue Wu, and Youxiang Li

    Headache (2010). Toshihiko Shimizu & Norihiro Suzuki

    Nerve Fibers Innervating the Cranial and Spinal Meninges: Morphology of Nerve Fiber Terminals and Their Structural Integration (2001). BRITTA FRICKE, KARL HERMANN ANDRES, AND MONIKA VON DU RING

     

  2. Anatomy of the brachial plexus (Revankar et al, 2013) 

    1. Nerve roots of the brachial plexus and their fascia:
    • The brachial plexus is formed by the union of the ventral rami from C5 to T1.
    • After exiting the intervertebral foramen these ventral rami run in the interval between the scalene anterior and scalene medius (scalene hiatus). This lies between the anterior tubercles (scalene anterior attachment) and posterior tubercles (scalene medius attachment) of the corresponding cervical transverse processes.
    • As well as the prevertebral fascia splitting between the scalene anterior and medius to create the scalene hiatus it also ensheaths the intervening C5 to T1 nerve roots. This prevertebral fascial sheath continues inferolaterally as the axillary sheath containing the nerve roots, trunks, cords and terminal branches.
    • After leaving the scalene hiatus these nerve roots of the brachial plexus descend in front of the scalene medius.

        2. Ventral rami to the nerve trunks of the brachial plexus:

    • The nerve trunks lie in the posterior triangle of the neck (borders: SCM, trap and middle 1/3 of clavicle).
    • Upper trunk: formed where the C5 & C6 ventral rami unite at the lateral border of scalenus medius.
    • Middle trunk: continuation of the C7 ventral rami.
    • Lower trunk: formed where the C8 & T1 ventral rami unite behind the scalene anterior.

        3. Nerve trunks to nerve cords of the brachial plexus:

        Each nerve trunk (upper, middle and lower) has anterior and posterior divisions. These divisions, behind the clavicle and through the costocoracoid space, form the posterior, lateral and medial cords:

    • Posterior cord: formed from the posterior divisions of all three trunks (C5-C8 & T1).
    • Lateral cord: formed from the anterior divisions of the upper and middle trunks (C5-C7).
    • Medial cord: continuation of the anterior division of the lower trunk (C8 & T1).

        4. Nerve cords to terminal branches:

        Between the lateral aspect of the Pectoralis Minor and axilla the nerve cords turn into the terminal nerve branches:

    • Musculocutaneous nerve: formed from the lateral cord of the brachial plexus (C5-C7).
    • Axillary nerve: formed from the posterior cord of the brachial plexus (C5 & C6).
    • Radial nerve: formed from the posterior, lateral and medial cords of the brachial plexus (C5-T1).
    • Median nerve: formed from the lateral (C6 & C7) and medial cords (C8 & T1) of the brachial plexus.
    • Ulna nerve: formed from the lateral (C7) and medial cords (C8 & T1) of the brachial plexus.

    Median nerve (Meyer et al 2018)

    Anatomy of the median nerve

    Nerve roots and cords

    C6-C7: lateral cord. C8-T1: medial cord.

    Trunk

    After originating from the brachial plexus in the axilla, the median nerve lies lateral to the brachial artery and then crosses it anteriorly to medially.

    The lower head of the coracobrachialis which is usually suppressed in human beings is sometimes present as the ligament of Struthers (supracondylar process of humerus --> medial epicondyle). The median nerve and brachial artery passes deep to this ligament.

    After entering the cubital fossa the nerve passes in relation to:

    • Bicipital aponeurosis (aka lacertus fibrosus): the nerve passes beneath the bicipital aponeurosis being sandwiched between the brachialis posteriorly and bicipital aponeurosis anteriorly.

    • Brachialis: passes over the brachialis sandwiched between the brachialis and the brachial fascia.

    • Pronator teres: passes between the humeral and ulnar heads of the pronator teres.

    In the anterior antebrachial compartment the nerve passes in relation to:

    • Flexor digitorium superficialis: runs under the aponeurotic arch of the flexor digitorum superficialis. Just proximal to the aponeurotic arch of the flexor digitorium superficialis the median nerve gives off the anterior interosseous nerve which innervates the deep flexors of the forearm.

    • Flexor digitorum superficialis and profundus: courses between the flexor digitorum superficialis and profundus muscles.

    In the distal forearm, 3cm proximal to the wrist crease, the median nerve gives rise to the palmar cutaneous branch. This nerve provides sensory innervation to the skin on the proximal side of the palm.

    In the wrist the median nerve passes under the flexor retinaculum into the carpal tunnel.

    Distal to the carpal tunnel the median nerve subdivides into five branches: the recurrent motor branch to the muscles of the thenar compartment and four digital sensory branches.

    The median nerve is palpable:

    • After emerging from the coracobrachialis.
    • Deep to the bicipital aponeurosis.
    • At the wrist where it emerges from behind the superficial flexor tendons just lateral to the palmaris longus.

    Innervation

    Motor function: flexors of the forearm except for the flexor carpi ulnaris and the ulnar head of the flexor digitorium profundus. Innervates the muscles of the thenar eminence and 1 & 2 lumbricals.

    Cutaneous innervation: thenar eminence, palm and lateral side of the palm, palmar side and distal dorsal aspects of the lateral three and a half digits.

    Fibers in the lateral cord (from the lateral roots) convey most of the sympathetic fibers to the median distribution of the hand (Standring 2015).

    Anatomy of the carpal tunnel

    The boundaries of the carpal tunnel are:

    • Posteriorly: carpal bones.
    • Laterally: tubercle of scaphoid and trapezium.
    • Medially: pisiform and hook of the hamate.
    • Anterior: the roof of the tunnel is formed from the flexor retinaculum (transverse carpal ligament or anterior annular ligament). The flexor retinaculum is divided into two layers (1) superficial: formed by the palmaris brevis tendon. (2) Deep: made up of transversal fibers.

    The carpal tunnel contains:

    • Tendons: flexor pollicis longus, the four flexor digitorum superficialis tendons and the four flexor digitorum profundus tendons.
    • Neurological: median nerve. Travels between the flexor retinaculum and the flexor tendons of the second and third fingers.

    Myofascial continuity and the median nerve 

    Stecco et al (2007) identified myofascial extensions tightening and tractioning the anterior brachial, antebrachial and palmar fascia from the pectoralis major, biceps and palmaris longus. These expansions can be likened to the tensor fascia lata that tightens and tractions the iliotibial band.

    These authors found the brachial fascia continuous proximally with the pectoralis, axillary and deltoid fascia and distally with the antebrachial and palmar fascia. The fascia of the pectoralis major and deltoid inserts tightly into these muscles by intramuscular septa.

    Conversley the brachial fascia is only adherent to the anterior muscles not by intramuscular septa but by myofascial expansions. The brachial fascia is also adherent to the humerus via the attachments to the medial and lateral intermuscular septum and directly via its attachment to the medial and lateral epicondyles.

    The anatomy of these myofascial expansions are:

    • Pectoralis major: clavicular part of the pectoralis major sends myofascial expansions to the anterior brachial fascia (costal part sent an expansion to the axillary and then to the medial part of the brachial fascia).
    • Biceps: the bicipital aponeurosis (lacterus fibrosus) sends an expansion to the antebrachial fascia. It gives origin to some of the fibres of the local muscles, amongst others the brachioradialis and flexor carpi radialis, and to several intermuscular septa.
    • Palmaris longus: the antebrachial fascia continues as the palmar fascia in the hand. At the wrist the antebrachial fascia is reinforced by the collagen fibres of the flexor retinaculum. Similarly not only is the palmar fascia reinforced by the palmaris longus but the palmaris longus aponeurosis is reinforced by attachments of the palmaris brevis and flexor pollicis brevis. The palmaris longus sends myofascial expansions to the flexor retinaculum as well as to the palmaris fascia at the hyperthenar eminence.

    Compression of the median nerve can occur at (i) between the lacterus fibrous and brachialis, (ii) between the brachialis and the brachial fascia(?) and (iii) the carpal tunnel by the flexor retinaculum (the superficial layer being formed from the palmaris brevis).

    Therefore from a mechanical perspective the myofascial expansions from the pectoralis major, biceps and palmaris longus may play an important role in the pathology of median nerve entrapment.

    Entrapment sites of the median nerve

    Entrapement sites of the median nerve are:

    • Carpal tunnel: 90-93% of median nerve entrapments.

    • Brachialis and brachial fascia: could the median nerve get trapped between the brachialis and brachial fascia?
    • Supracondylar process continued by the ligament of Struthers: the ligament of Struthers extends from supracondylar process --> medial epicondyle. It encases the median nerve and brachial artery.

    • The bicipital aponeurosis (lacertus fibrosus): extends from the myotendinous junction of the distal bicep to the medial deep fascia of the forearm close to the epicondylar muscles. Covers the median nerve and the brachial artery.

    • Pronator teres: the median nerve runs between the humeral and ulnar heads of the pronator teres.

    • Fibrous arch of the origin of the flexor digitorum superficialis.

    Anatomical variations in the forearm causing entrapment of the median nerve:

    • Accessory head of the flexor pollicis longus.

    • Accessory head of the flexor digitorum profundus.

    • Bicipital bursa.

    Anatomical variations in the carpal tunnel causing entrapment of the median nerve:

    • Accessory palmaris longus.

    • Accessory palmaris profundus.

    • Accessory flexor digitorum muscle.

    • Accessory lumbricals.

    Ulnar nerve (Choi et al (2018)

    Anatomy of the ulnar nerve

    Nerve root and cords

    (C7: lateral cord). C8-T1: medial cord

    Trunk

    Travels medial to the brachial artery up until the insertion of the coracobrachialis. It then pierces the medial intermuscular spetum*, at the arcade of Struthers, 10cm proximal to the medial epicondyle, to enter the posterior compartment of the arm.

    * Medial intermuscular septum: lesser tubercle --> along the medial supracondylar ridge --> medial epicondyle. It is blended with the tendon of the coracobrachialis. Stecco et al (2007) found the costal part of the pectoralis major to send myofascial expansions to the axillary and then the  medial brachial fascia. The medial intermuscular septum gives attachment to the triceps posteriorly and brachialis anteriorly.

    The arcade of Struthers is a fibrous canal on the medial aspect of the lower third of the arm. It consists of the medial head of the triceps (and its fascial sheath) and its aponeurotic expansion which extends into the medial intermuscular septum and internal brachial ligament* (Caetano et al 2017). Because the arcade of Struthers is just a passage way in the medial intermuscular septum for the ulnar nerve to pass from the anterior to posterior compartment of the arm Caetano et al (2017) described it as an 'unfolding' of the medial intermuscular septum.

    *: Internal brachial ligament: medial intermuscular septum proximally --> medial intermuscular septum distally (near medial epicondyle).

    The nerve then continues posteriorly to the medial epicondyle at the cubital tunnel.

    After leaving the cubital tunnel the ulnar nerve crosses the medial collateral ligament of the elbow before entering the forearm.

    The ulnar nerve enters the forearm between the humeral and ulnar origin of the flexor carpi ulnaris.

    The nerve then travels into a deep fascia septum between the anterior surface of the flexor carpi ulnaris and the posterior surface of the flexor digitorum superficialis. This deep fascia is a tough structure that lies immediately against the course of the ulnar nerve.

    The ulnar branches to the flexor carpi ulnaris arise proximal to this fascial septum between the flexor carpi ulnaris and flexor digitorum superficialis.

    More distally branches to the flexor digitorum profundus pierce this fascial septum.

    The dorsal cutaneous nerve arises from the ulnar nerve 6cm proximal to the ulnar styloid process.

    At the wrist the ulnar nerve divides into superficial (sensory) and deep (motor) components both of which pass through Guyon's canal.

    The ulnar nerve is palpable at:

    • Posterior to the medial epicondyle.
    • At the wrist as it emerges from under the flexor carpi ulnaris.

    Innervation of the ulnar nerve

    Motor function:

    • Flexor carpi ulnaris.
    • Medial half of Flexor digitorium profundus.
    • Hypothenar muscles.
    • Medial two lumbricals.
    • Adductor pollicis.
    • Interossei of the hand.
    • Palmaris brevis.

    Cutaneous innervation:

    • Articular branch: elbow joint
    • Palmar cutaneous branch: innervates the skin of the medial half of the hand.
    • Dorsal cutaneous branch: innervates the skin of the medial one and a half fingers, and the associated dorsal hand area.
    • Superficial branch: innervates the palmar surface of the medial one and a half fingers.

    Anatomy of the cubital tunnel

    The cubital tunnel is bordered by (Machhi et al 2014):

    • Medially: humeral and ulnar heads of the flexor carpi ulnaris.
    • Anteriorly: medial epicondyle.
    • Roof*: arcuate ligament of Osborne. This 'ligament' is a fusion of the deep fascia of the flexor carpi ulnaris and antebrachial fascia spanning from the medial epicondyle --> olecranon process. When present the anconeus epitrochlearis (medial epicondyle --> anconeus) forms the roof of the cubital tunnel.

    *: Traditionally the roof of the cubital tunnel has been defined by the arcuate ligament of Osbrone. However Macchi et al (2014) found the roof of the cubital tunnel to be formed from a myofascial trilaminar retinaculum comprising three layers: 

    • Layer one: a layer of loose connective tissues corresponding to the deep fascia. 

    The ulnar nerve is covered in a fibrous thickening of the brachial fascia. This fascia is at the border between the muscle and the tendon 5 cm proximal from the elbow joint line. 

    This thickening of the brachial fascia is formed by two laminae of fibres:

    a. Lamina one: arises from the triceps fascia. It bridges the elbow, attaching from the medial epicondyle to the olecranon process, to then spread into the antebrachial fascia.

    b. Lamina two: appears between the medial intermuscular septum and the triceps.

    • Layer two: a layer of connective tissue corresponding to a tendinous structure of the triceps proximally and flexor carpi ulnaris distally.
    • Layer three: a bundle of muscle corresponding to the triceps proximally and flexor carpi ulnaris distally.

    Anatomy of the Guyons's canal

    Guyon's canal is a fibrosseous tunnel. It's formed by the transverse carpal ligament at the proximal aspect of the pisiform --> origin of the hypothenar eminence at the hook of the hamate.

    Sites of entrapment

    • Arcade of Struthers: it is controversial whether this site is a potential cause for ulnar nerve entrapment. However could it be a potential point of tethering effecting the gliding movement of the nerve?
    • Cubital tunnel. Macchi et al (2014) found pathological fusion of the trilaminar roof of the cubital tunnel reduces gliding of the ulnar nerve during movements at the elbow.

    • Flexor/pronator muscle origin: formation of “tendinous bands” at the humeral and ulnar heads of the flexor carpi ulnaris/pronator muscle origin.

    • Macchi et al (2014) found fascial structures (fibrous bands) over the ulnar nerve in the proximal forearm.
    • Medial intermuscular septum: the medial intermuscular septum runs between the flexor carpi ulnaris and flexor digitorum profundus muscles. The ulnar nerve can suffer proximal and distal compression by the medial intermuscular septum.

    • Deep fascia septum between the anterior surface of the flexor carpi ulnaris and the posterior surface of the flexor digitorum superficialis: whilst Choi et al (2018) found no ulnar nerve compression by this fascial septum with elbow extension some angulation of the proximal ulnar nerve was noted due to its intimate connection to this deep fascia.

    • Fibrous aponeurosis between the flexor digitorum superficialis and the humeral head of the flexor carpi ulnaris: the ulnar nerve lies against this dense fibrous aponeurosis formed from the flexor carpi ulnaris posteriorly and flexor digitorium superficialis anteriorly. 

    • Anconeus epitrochlearis muscle. Macchi et al 2014 found this muscle to not always be present. When present it spans from medial epicondyle --> olecranon.

    Because of the medial head of triceps relation to the medial intermuscular septum (and arcade of Struthers) and the roof of the cubital tunnel (myofascial trilaminar retinaculum) could this explain the similarities in ulnar nerve symptoms and myofascial symptoms of the medial head of triceps.

    Radial nerve

    Anatomy of the radial nerve

    Nerve roots and cord

    C5-8 (T1): posterior cord.

    Nerve trunk

    The radial nerve descends anterior to the subscapularis, latissimus dorsi and teres major tendons.

    It then passes through the lower triangular space (lower border of teres major, long head of triceps and humerus) with the profunda brachii artery. Here it gives rise to the posterior cutaneous nerve of the arm.

    Coursing distally in passes through the arm between the medial and lateral heads of the tricep and spiral groove. Proximally as the nerve passes between the medial and lateral heads of the tricep it passes through a fibrous arch. This fibrous arch consists of muscle fibers that originate from the lateral head of tricep tendon --> just below the lateral part of the spiral groove (Latef et al 2018). 

    Between the distal and middle third of the arm Fleming et al (2004) found the nerve pierced the lateral intermuscular septum*. From here it enters the anterior compartment of the arm running between the brachialis and brachioradialis.

    *Lateral intermuscular septum separates the anterior and posterior compartments of the arm. It extends from the greater tuberosity (or bicipital groove, Dones et al 2013) to the lateral epicondyle and anular ligament. Proximally it's in continuity with the the deltoid tendon and its fibrous aponeurosis (Rispoli et al 2009). The midsection is in continuity with the lateral aspect of the brachialis and deep brachial fascia anteriorly and gives attachment to the triceps posteriorly. Distally it attaches to the superficial fascia (Dones et al 2013) and gives attachment to the brachioradialis and extensor carpi radialis anteriorly and is confluent with the annular ligament encircling the radial head.

    Anterior to the elbow, at the level of the tip of the lateral epicondyle, the radial nerve branches into the superficial radial nerve and the posterior interosseous nerve (deep branch of the radial nerve).

    The posterior interosseous nerve

    The posterior interosseous nerve travels around the lateral aspect of the radius passing underneath the fibrous bands of the extensor muscles at the level of the radial head. It then enters the radial tunnel which extends from the radial head --> inferior border of the supinator.

    The nerve exits the radial tunnel beneath the aponeurotic margin between the superficial and deep layers of the supinator muscle. Here the nerve can be compressed at the arcade of Frohse (a fibrous arch formed from the superficial head of the supinator).

    It then courses along the posterior compartment of the arm towards the wrist deep to the brachioradialis and terminates in a separate fascial sheath at the base of the fourth extensor compartment at the dorsal wrist capsule underneath the extensor digitorium and extensor indicis.

    Superficial radial nerve

    Descends from the lateral epicondyle between the brachioradials and the supinator. It carries on descending behind the brachioradialis exiting from under the brachioradialis at the junction of the  proximal two thirds and distal one third of the forearm. From here it curves around the lateral side of the radius piercing the deep fascia innervating the skin on the dorsum of the hand and lateral three and a half digits.

    Patel et al (2014) found a fascial ring from the dorsal edge of the brachioradialis constricting the nerve and from the fascia connecting the brachioradialis and extensor carpi radilais longus.

    The radial nerve can be palpable between the brachialis and brachioradialis just above the lateral epicondyle.

    Innervation

    • Motor: innervates the triceps and the extensor muscles in the forearm.
    • Cutaneous innervation: innervates most of the skin of the posterior side of forearm, the dorsal surface of the lateral side of the palm, and dorsal surface of the lateral three and a half digits.
    • ? Subdeltoid bursa: Seo et al (2018) found branches of the posterior cord of the brachial plexus (they did not specify the radial nerve) to supply the anterolateral area of the subdeltoid bursa. These authors found whilst the bursa is mainly innervated by the suprascapular nerve it is also innervated by the axillary and lateral pectoral nerves.

    Anatomy of the radial tunnel

    The radial tunnel is bordered by (Xiao & Cartwright 2019):

    • Laterally: mobile wad of Henry (brachioradialis, extensor carpi radialis longus, and extensor carpi radialis brevis muscles).
    • Medially: biceps tendons and brachialis.
    • Posteriorly: radial recurrent vessels (leash of Henry), the superficial head of the supinator muscle, and the brachioradialis muscle.
    • Anteriorly: The capsule of the radiocapitellar joint and the deep head of the supinator muscle.

    Myofascial continuity and the radial nerve

    Under the section 'myofascial continuity and the median nerve' Stecco et al (2007) identified certain muscles that attached on to and tensed the anterior brachial fascia. These muscles happened to be in relation to the median nerve, and, in principle functioned similar to the tensor fascia lata muscle that tenses the fascia that is the iliotibial band.

    Stoeckart et al (1991) found a similar effect with the tricep muscle on the antebrachial fascia around the lateral epicondyle.

    The interest of this area with regards to radial nerve entrapment is (i) the brachioradialis and extensor carpi radialis brevis in forming the lateral side of the radial tunnel and (ii) the extensor carpi radialis brevis in compressing the radial nerve against the supinator.

    Stoeckart et al (1991) found simulated contraction of the tricep tensed the antebrachial fascia taking the strain off the extensor muscles. The most notably effect was on the extensor digitorium and extensor carpi radialis longus due to their direct fascial attachments.

    To extend this concept further the lateral intermuscular septum attaches distally onto the extensor carpi radialis. Therefore could the muscles attaching onto the lateral intermuscular septum i.e. the deltoid, triceps and brachialis preload this fascial septum and intern its attachments to the brachioradialis and extensor carpi radialis reducing strain on these muscles as well as the superficial fascia?

    Sites of compression

    • Radial tunnel (radial tunnel syndrome): Moradi et al (2015) found the radial nerve to be compressed in the tunnel by bands of fascia and the inferior edge of the supinator muscle. 
    • Arcade of Frohse: Moradi et al (2015) identified the arcade of Frohse as the most common site of radial nerve entrapment affecting the posterior interosseous nerve. As a fibrous arch from the superficial supinator muscle the arcade of Froshe is meant to develop in adults from repetitive movements (Clavert et al 2009). This leads the potential for repetitive strain injuries in this muscle thickening this fibrous arch causing radial nerve entrapment.
    • Brachioradialis: the superficial branch of the radial nerve runs underneath the brachioradialis in the proximal two thirds of the forearm. Along this course it runs between the supinator and the brachioradialis, in the fascia between the extensor carpi radialis longus and brachioradialis and through a fascial ring in the brachioradialis (Wartenberg syndrome). The fascia between the extensor carpi radialis longus and brachioradialis and the fascia of the brachioradialis forming the ring that the superficial radial nerve goes through (Wartenberg syndrome) are all areas of potential entrapment. However could the space between the supinator and brachioradialis form an area of potential tethering?
    • Triangular space: the lower triangular space is formed from the lower border of teres major, long head of triceps and humerus. The radial nerve can get trapped between the humerus and the long head of the tricep (Bowman et al 2018).
    • Lateral head of the triceps (fibrous arch): the fibrous arch consists of muscle fibers from the lateral head of triceps tendon --> just below the lateral part of the spiral groove. It's located at the point where the radial nerve courses between the lateral and medial heads of the tricep. It can also lead to compression during extensive muscular effort when increased blood flow causes the triceps to swell (Latef et al 2018).
    • Lateral intermuscular septum: Bowman et al (2018) found the radial nerve travels through the lateral intermuscular septum between the middle and distal third of the arm in a defect with a mean diameter of 1cm. At this point the radial nerve has greatly restricted mobility  (Carian et al 2007).
    • Between the superolateral aspect of the extensor carpi radialis brevis and the superior edge of the supinator: this can be a site of entrapment for the posterior interosseous branch of the radial nerve as it supplies the extensor carpi radialis brevis (Clavert et al 2009).
    • Accessory muscle: accessory subscapularis-teres-latissimus muscle (Bowman et al 2018).

    A common presentation in practice is lateral radiating arm pain. If caused by the radial nerve then a case can be made for examining the lateral triceps to exclude an entrapment in the lower triangular space and its fibrous aponeurosis. Obvioulsy as well as this the lateral intermuscular septum would be an area of interest.

    Musculocutaneous nerve

    Anatomy of the musculocutaneous nerve

    Nerve roots

    C5-7: lateral cord

    Nerve trunk

    Musculocutaneous nerve

    The musculocutaneous nerve originates in the axilla (third part of the axillary artery). Once its left the axilla the nerve passes through the two fused heads of the coracobrachialis near its attachment to the humerus. It then passes between the brachialis and biceps to innervate these muscles.

    Lateral cutaneous nerve of the forearm

    Deep to the biceps the nerve continues as the lateral cutaneous nerve of the forearm. It emerges lateral to the biceps, a few centimetres above the elbow, in the space between the biceps and brachialis just lateral to the bicpes tendon. Here it pierces the deep fascia and continues down the forearm.

    Innervation

    • Motor: coracobrachialis, biceps and most of the brachialis.
    • Sensory (lateral cutaneous nerve of forearm): supplies the skin of the lateral forearm sometimes extending to 1 MC and the lateral part of the thenar eminence.

    Sites of compression

    • Coracobrachialis: in human beings, the upper two heads of the coracobrachialis are usually fused while taking origin from the coracoid process. They enclose the musculocutaneous nerve in between the two fused heads. This gives the impression that the musculocutaneous nerve pierces the coracobrachialis muscle (Maiti & Bhattacharya 2018).
    • Biceps and brachialis: the musculocutaneous nerve courses between the biceps and brachialis. Could this be an area of direct compression or restriction to nerve gliding? 

    Axillary nerve

    Anatomy of the axillary nerve

    Nerve roots

    C5 & C6: posterior cord.

    Nerve trunk

    Axillary nerve

    The axilary nerve runs in the axilla turning around the subscapularis to pass almost horzontally through the quadrilateral space (superiorly: teres minor; inferiorly: teres major; medially: long head of the triceps; laterally: humerus).

    After emerging from the quadrilateral space the nerve divides into an anterior, posterior and collateral branch:

    • Anterior (upper) branch: runs under the deltoid to the anterior portion of this muscle. It supplies motor branches to the deltoid and pierces this muscle to provide cutaneous innervation. It also innervates the subdeltoid bursa (Seo et al 2018).
    • Posterior (lower) branch: innervates the teres minor and posterior deltoid. The posterior branch pierces the deep fascia to continue as the superior lateral nerve of the forearm.
    • Collateral branch: innervates the long head of triceps.

    Superior lateral cutaneous nerve of the arm

    The superior lateral cutaneous nerve of the arm leaves the posterior (lower) branch of the axillary nerve sweeping around the posterior border of the deltoid. It supplies the skin over the lower two thirds of the posterior part of this muscle and that of the the long head of triceps. 

    Innervation

    • Teres minor.
    • Delotid.
    • Long head of triceps.
    • Skin over the deltoid, lateral shoulder and long head of triceps.
    • Subdeltoid bursa: Seo et al (2018) found the muscular branches of the anterior and middle parts of the deltoid, from the anterior (upper) branch, distributes to the branch of the nerve that innervates the subdeltoid bursa. These authors found 60% of the axillary nerve branches innervates the posterolateral aspect of the bursa. Whilst the bursa is mainly innervated by the suprascapular nerve as well as the axillary nerve it also receives branches from the posterior cord and lateral pectoral nerve.

    Sites of compression

    • Quadrilateral space: fibrous bands and muscular hypertrophy (Hangge et al 2018). 
    • Subdeltoid bursa: Seo et al (2018) found  a branch of the axillary nerve runs through the subdeltoid bursa.

    Suprascapular nerve

    Anatomy of the suprascapular nerve

    Nerve roots

    Ventral rami (C4) C5>6: upper trunk of brachial plexus

    Nerve trunk

    The nerve runs posteriorly under the trapezius and omohyoid. It then enters the supraspinous fossa through the suprascapular notch under the superior transverse ligament. Once in the supraspinous fossa the nerve then passes inferolaterally around the lateral border of the spine of scapular to enter the spinoglenoid notch between the spine of scapular and the glenoid rim. Passing through this notch underneath the spinoglenoid ligament the nerve enters the infraspinous fossa.

    When a cutaneous branch is present it pierces the deltoid close to the tip of the acromion to supply the lateral proximal third of the arm.

    Innervation

    • Supraspinous fossa: Supraspinatus.
    • Infraspinous fossa: Infraspinatus and articular rami to the shoulder (70% of the shoulder joint), posterior and superio shoulder joint capsule, coracoacromial ligaments, A/C joint and is the main innervation of the subacromial bursa (also innervated by posterior cords of brachial plexus, axillary nerve and lateral pectoral nerve).
    • Cutaneous (when present): lateral proximal third of the arm (axillary distribution). 

    Entrapment sites for the suprascapular nerve

    Duparc et al (2010) found an entrapment neuropathy of the suprascapular nerve in the:

    • Suprascapular notch: is a depression in the superior aspect of the scapula just medial to the coracoid process. The roof of the suprascapular notch is formed from the superior transverse scapular ligament. The suprascapular nerve enters the supraspinous fossa under the superior transverse scapular ligament through this notch. The superior transverse scapular ligament attaches to the base of coracoid --> medial end of scapular notch. It has attachments from the conoid ligament (medial fasciculus of coracoclavicular lig), omohyoid, supraspinatus fascia and when present the subclavius posticus or chondroscapularis.
    • Spinoglenoid notch: is a notch connecting the supraspinous and infraspinous fossa through which the suprascapular nerve passes. Its borders are: (i) medially where the most lateral aspect of the spine of scapula leaves the scapula; (ii) laterally the glenoid rim; (iii) superiorly the spinoglenoid ligament. The spinoglenoid ligament attaches on to the neck of the scapula (in the spinoglenoid notch) --> rim of the posterior glenoid and shoulder joint capsule.
    • Supraspinatus fascia: this fascia lies within the supraspinous fossa forming a sheath for the suprascapular nerve (Duparc et al 2008). Superiorly this fascia inserts on to the superior border of the scapula and the superior transverse scapular ligament. Inferiorly it attaches to the floor of the supraspinous fossa. On the floor of the supraspinous fossa the fascia forms a fibrous aperture. This aperture has a thickened zone which constitutes a histological equivalent to the spinoglenoid ligament. Bektas et al (2003) termed this condensation of the supraspinous fascia forming a replica splenoglenoid ligament the 'spinoglenoid septum'. Much like the spinoglenoid ligament the splenoglenoid septum extends from the spinoglenoid notch --> posterior shoulder joint capsule.

    Therefore the supraspinous fascia can trap the suprascapular nerve at three different levels: superiorly as it attaches to the superior transverse ligament; forming a sheath for the suprascapular nerve; inferiorly creating an aperture (as well as the spinoglenoid septum) so the nerve can pass to the infraspinous fossa. 

    • Between the deep fascia of the subscapularis and the superior transverse scapular ligament: the deep fascia of the Subscapularis attaches posteriorly to the costal surface of the scapula. At the superior end of the scapular between the base of the coracoid and the medial end of the scapula notch runs the superior transverse scapular ligament. Between the deep fascia of the subscapularis and the superior transverse scapular ligament is a space that the suprascapular nerve runs through (Tasaki et al 2015). 
    • Anterior coracoscapular ligaments (Sahu et al 2012).
    • Hypertrophied Infraspinatus (Sahu et al 2012).
    • In the common tendon of the omohyoid and subclavius posticus or chondroscapularis: The subclavius posticus, that is not often present, originates from the postero-superior side of the costocoracoid membrane and costoclavicular ligament and inserts onto the superior boarder of the scapula and on the superior transverse scapular ligament Grigorita et al (2019). As the suprascapular nerve runs above the superior transverse scapular ligament and perforates the subclavius posticus it can be prone to entrapment. As this muscle can share a common tendon with the inferior belly of the omohyoid muscle could this be the entrapment site of the suprascapular nerve by the omohyoid mentioned by Sahu et al (2012)?
    • Coracocalvicular ligaments: these ligaments divide into the conoid ligament (posterior and medial fasciculus) and trapezoid ligament (anterior and lateral fasciculus). Harris et al (2001) found 33% of coracoid attachments of the conoid ligament attached on to the lateral fibers of the superior transverse scapular ligament.

    The big players

    Muscles representing sites of multiple nerve entrapment are:

    • Prontator teres

    Median nerve: the median nerve passes between the humeral and ulnar heads of the pronator teres.

    Ulnar nerve: tendonous bands at the flexor carpi ulnaris/pronator teres origin can trap the ulnar nerve.

    • Flexor digitorium superficialis

    Median nerve:

    i. Runs under the aponeurotic arch of the flexor digitorium superficialis.

    ii. Runs between the flexor digitorium superficialis and flexor digitorium profundus.

    Ulnar nerve: the ulnar nerve runs inrelation to the fascial septum between the flexor carpi ulnaris and flexor digitorium superficialis.

    • Flexor digitorium profundus

    Median nerve: the median nerve runs between the flexor digitorium superficialis and flexor digitorium profundus.

    Ulnar nerve: the ulnar nerve runs inrelation to the medial intermuscular septum between the flexor carpi ulnaris and flexor digitorium profundus.

    • Flexor carpi ulnaris

    Ulnar nerve:

    i. Enters the forearm between the humeral and ulnar heads of the flexor carpi ulnaris. Tendonous bands from the flexor carpi ulnaris/pronator origin can trap the ulnar nerve.

    ii. Runs inrelation to the fascial spetum between the flexor carpi ulnaris and flexor digitorium superficialis.

    iii. Runs inrelation to the medial intermuscular septum between the flexor carpi ulnaris and flexor digitorium profundus.

    iv. The muscle and fascia can form the roof of the cubital tunnel either as the arcuate ligament of Osborne or along with the triceps as part of the the myofascial trilaminar retinaculum.

    • Medial head of triceps

    Ulnar nerve: the medial head of triceps is inrelation to:

    i. Medial intermuscular septum (and arcade of Struthers).

    ii. cubital tunnel: forms the roof of the cubital tunnel as part of the myofascial trilaminar retinaculum with the flexor carpi ulnaris.

    Radial nerve: the radial nerve courses between the medial and lateral heads of tricep.

    • Lateral head of triceps

    Radial nerve:

    i. Runs between medial and lateral triceps.

    ii. Runs through the fibrous arch: lateral head of tricep tendon --> just below the lateral spiral groove.

    iii. Runs through the lateral intermuscular septum: the lateral intermuscular septum gives attachment to the lateral head of tricep.

    References

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    The Deep Fascia of the Forearm and the Ulnar Nerve: An Anatomical Study (2018). Paul J ChoiChidinma NwaogbeJoe IwanagaGeorgi P GeorgievRod J Oskouian, and R. Shane Tubbs.

    The cubital tunnel: a radiologic and histotopographic study (2014). Veronica MacchiCesare TiengoAndrea PorzionatoCarla SteccoGloria SarasinShane TubbsNicola Maffulli, and Raffaele De Caro

    Injury of the Radial Nerve in the Arm: A Review (2018). Taroob J Latef, Muhammad Bilal, Marc Vetter, Joe Iwanaga, Rod J Oskouian, and R. Shane Tubbs 

    Frohse's arcade is not the exclusive compression site of the radial nerve in its tunnel (2009). P.Clavert, J.C.Lutz, P.Adam, R.Wolfram-Gabel, P.Liverneaux, J.L.Kahn

    The radial nerve in the brachium: an anatomic study in human cadavers (2007). Carlan DPratt JPatterson JMWeiland AJBoyer MIGelberman RH.

    One-third, two-thirds: relationship of the radial nerve to the lateral intermuscular septum in the arm (2004). Fleming PLenehan BSankar RFolan-Curran JCurtin W

    Ultrasound in the Evaluation of Radial Neuropathies at the Elbow (2019). Ted G. Xiao and Michael S. Cartwright

    Lateral intermuscular septum as cause of radial nerve compression: case report and review of the literature (2018). Jason BowmanBryan CurnutteKyle AndrewsJacob StirtonNabil Ebraheim, and Abdoul Azim Mustapha.

    Radial Tunnel Syndrome, Diagnostic and Treatment Dilemma (2015). Ali Moradi, Mohammad H Ebrahimzadeh and Jess B Jupiter.

    Anatomical study of myofascial continuity in the anterior region of the upper limb (2007). Antonio Stecco, Veronica Macchi, Carla Stecco, Andrea Prozinato, Julie Ann Day, Vincent Delmas, Raffaele De Caro

    The anatomy of the forearm extensor muscles and the fascia in the lateral aspec of the elbow joint complex (2013). Valentin C Dones III, Steven Milanese, David Worth, Karen Grimmer-Somers

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    Relation of roots and trunks of brachial plexus to scalenus anterior muscle and its clinical significance (2013). Yogesh , Viveka S , Sudha M J , Santosh Kumar S.C, Sanjay Revankar 

    ANATOMIC BASIS FOR SUBFASCIAL COMPRESSION OF THE SUPRASCAPULAR NERVE IN THE SUPRASPINOUS FOSSA (2008). Fabrice DUPARCJocelyn OZEELMaxime NOYON,  Antoine GEROMETTAChantal MICHOT

    Anatomical basis of the suprascapular nerve entrapment, and clinical relevance of the supraspinatus fascia (2010). Duparc F, Coquerel D, Ozeel J, Noyon M, Gerometta A, Michot C.

    Anatomic observation of the running space of the suprascapular nerve at the suprascapular notch in the same direction as the nerve. (2015). Tasaki A, Nimura A, Mochizuki T, Yamaguchi K, Kato R, Sugaya H, Akita K.

    Spinoglenoid Septum: a new anatomical finding (2003). Bektas U, Ay S, Yilmaz C, Tekdemir I, Elhan A

    An Aberrant Subclavius Posticus Muscle: A Case Report (2019). Laura Grigoriță, Monica-Adriana Vaida and Adelina Jianu

    Anatomic variance of the coracoclavicular ligaments (2001). Harris RI, Vu DH, Sonnabend DH, Goldberg JA,, Walsh RW

    A study on variations of accessory coracobrachialis muscle along with variations of biceps brachii muscle (2018). Maiti D, Bhattacharya S.

     

    Quadrilateral Space Syndrome: Diagnosis and Clinical Management (2018). Patrick T. HanggeIlana BreenHassan AlbadawiM. Grace KnuttinenSailendra G. Naidu, and Rahmi Oklu.

     

    Clinical Anatomy for the Innervated Pattern and Boundary of the Subdeltoid Bursa (2018). Chang Min Seo, Kyungyong Kim, Anna Jeon, Chang Sub Uhm, Je-Hun Lee and Seung-Ho Han