Osteopathy Journals and Research by Darren Chandler

 

 RSS Feed

  1. Introduction

    Periscapular pain is a common clinical presentation. Amongst other causes an entrapment neuropathy of the dorsal scapular nerve can cause these symptoms. These conditions can be treat with conservative treatment.

    The article is split into:

    • Anatomy of the dorsal scapular nerve.
    • Symptoms of dorsal scapular neuropathy.
    • Pathology of dorsal scapular neuropathy.

    Anatomy of the dorsal scapular nerve

    Muir (2017) identified the course of the dorsal scapular nerve as:

    • Originates from the anterior ramus of the C5 nerve root directly, or, as the first branch of the superior trunk of the brachial plexus. Variations include sharing a common branching trunk with the long thoracic nerve, C4 nerve root or C4 and C5 nerve root. Trescot (2016) said the nerve can receive nerve roots from as low as T1.
    • Arises within the posterior cervical triangle deep to the prevertebral fascia. It then passes obliquely and inferiorly through the middle scalene without innervating it. Variations include the nerve piercing the middle and posterior scalene muscles.
    • Runs inferior and slightly laterally between the superior fibres of the upper trapezius medially and the levator scapulae laterally. Variations include the dorsal scapular nerve piercing the levator scapulae.
    • Passes deep to the upper trapezius fibres between the rhomboid major/minor and the serratus posterior superior muscle.
    • Runs inferiorly along the medial boarder of the scapula to the inferior medial boarder of the scapula.

    Variations in the course of the dorsal scapular nerve includes a looping of the nerve around the deep branch of the cervical artery and dorsal scapular artery.

    Signs and symptoms of dorsal scapular neuropathy

    The signs and symptoms of dorsal scapular neuropathy as:

    • Pain, stiffness, dysesthesia in the scapular, thoracic and costovertebral area (& Sultan et al 2013) and cervical spine (Trescot 2016).
    • Posterolateral arm symptoms (Muir 2017). Lateral arm and forearm symptoms (Trescot 2016).
    • Notalgia paresthetica (NP): pruritis, numbness and tingling, and pain in the upper to mid-thoracic spine (Muir 2017).
    • Winged scapula or ‘SICK’ scapula: acronym for Scapular malposition, Inferior medial boarder prominence, Coracoid pain and malposition, and dysKinesis of scapular movement (Muir 2017).
    • Anterior chest pain and pain on palpating the anterior chest wall over the T4 sternocostal boarder (Trescot 2016).
    • Rhythmic involuntary jerking movements of the shoulder (Trescot 2016).
    • In chronic cases atrophy of the Rhomboid and Levator Scapula (Trescot 2016).

    Pathology of dorsal scapular neuropathy

    Vascular (Muir 2017):

    Variations from the standard anatomical description of the dorsal scapular nerve can cause the nerve to become compressed by:

    • Deep branch of the cervical artery.
    • Dorsal scapular artery.

    Musculoskeletal

    If following the standard anatomical description the dorsal scapular nerve can become entrapped in the:

    • Scalene Medius (Muir 2017, Sultan et al 2013, Hanson & Auyong, 2013).
    • Rhomboids (Sultan et al 2013).

    Variations from the standard anatomical description of the dorsal scapular nerve can cause the nerve to become compressed by (Muir 2017):

    • Tendonous fibrous tissue at the inferior edge of the Scalene Medius (Trescot 2016).
    • Posterior Scalene.
    • Levator Scapulae.
    • Elongation of the C7 TP (Sultan et al 2013).

    As well as the dorsal scapula nerve the long thoracic nerve can also course through the Scalene Medius (Hanson & Auyong 2013).

    Hester et al (2000) found the long thoracic nerve in close relation to a tight fascial band of tissue. This fascial tissue arose from the inferior aspect of the brachial plexus, extended just superior to the middle scalene muscle insertion on the first rib, and to the proximal aspect of the serratus anterior muscle.

    Abduction and external rotation (e.g. a throwing action) caused the long thoracic nerve to "bow-string" across this fascial band. This was postulated as dynamically compressing the long thoracic nerve (Hester al 2000).

    Winging of the scapula caused by a long thoracic or dorsal scapula neuropathy may:

    • Further compress the long thoracic nerve: (Hester et al 2000) found medial and upward migration of the superior most aspect of the scapula was found to further compress the long thoracic nerve.
    • Induce a stretch of the cutaneous medial branches of the dorsal primary rami of thoracic spinal nerves: this will refer further pain to the interscapular region (Sultan et al 2013).

    References

    Muir, B. Dorsal scapular nerve neuropathy: a narrative review of the literature (2017)

    Sultan HE, Younis El-Tantawi GA. Role of dorsal scapular nerve entrapment in unilateral interscapular pain. (2013).

    Hanson NA, Auyong DB.Systematic ultrasound identification of the dorsal scapular and long thoracic nerves during interscalene block. (2013). 

    Trescot A. Dorsal Scapular Nerve Entrapment (2016)

    Hester P, Caborn DN, Nyland J. Cause of long thoracic nerve palsy: a possible dynamic fascial sling cause. (2000)

  2. Introduction

    Rotator cuff anatomy has been traditionally viewed as a series of single muscles with each muscle responsible for a different action. For instance it is commonly known the origin and insertion of each of the four rotator cuff muscles and that their tendons splay out and interdigitate to form a common, continuous insertion on the humerus. But what of the anatomy and function of the different parts of each one of these rotator cuff muscles, for example the anterior and posterior parts of the supraspinatus? Or the fascial anatomy of these muscles in relation to different pain presentations or proprioceptive function? 

    A more detailed look at the anatomy of the rotator cuff muscles and the deltoid reveal:

    • A ‘single’ muscle can be anatomically divided into different sections.
    • Each one of these sections has different functions.
    • Fibrous septa can exist within different parts of the muscle to give structural support and help in soft tissue repair. This structural support gives mechanical strength to the muscle preventing it from deforming and migrating during contraction.
    • Regional anatomy of the fascia not only dictates different symptoms but mechanically has a proprioceptive function in the shoulder.
    • Entrapment neuropathies can exist in the rotator cuff muscles.
    • Anatomical anomalies may account for different presentations.

    The article looks at the anatomy and function of the different muscles, including its fascia, of:

    • Supraspinatus.
    • Infraspinatus.
    • Teres Minor.
    • Subscapularis.
    • Rotator Interval.
    • Deltoid.
    • Coracobrachialis.

    Lastly it reviews:

    • Fascia's proprioceptive function in the shoulder.

    Supraspinatus

    Origin: medial two thirds of the supraspinous fossa and supraspinatus fascia.

    Insertion: greater tuberosity from the bicipital groove to the top of the bare area (Curtis et al 2006).

    The tendon is contiguous with the transverse humeral and coracohumeral ligaments and the infraspinatus. It blends into the articular capsule in the distal 1cm. The tendon is enveloped by a thick sheet of fibrous tissue derived from the coracohumeral ligament (Clark and Harryman 1992).

    Gates et al (2010) divided the supraspinatus into anterior and posterior sections.

    Anterior section: has a larger muscle with ‘a very strong’ fibrous frame within the muscle (Gagey, 1993). It produces 71% of the total force of the muscle. The tendon of the anterior part of the supraspinatus is thicker and more tubular. It extends further medially from its insertion on the greater tuberosity to branch into a fibrous framework derived from the coracohumeral ligament (Clark and Harryman 1992). Clark & Harryman (1992) found the biceps tendon was ensheathed by interwoven fibers derived from the anterior part of the supraspinatus (and subscapularis) tendons.

    Posterior section: has a smaller muscle with a wider thinner tendon. It produces 29% of the total force. The posterior tendon does not have the fibrous organization of the anterior tendon (Gates et al 2010).

    Action:

    Gates et al (2010) found the greatest amount of rotation occurred at lower degrees of abduction and at the highest supraspinatus load.

    Anterior section: internally or externally rotates the humerus depending on if the shoulder is internally or externally rotated respectively.

    Posterior section: externally rotates or does not induce rotation.

    Ihashi et al (1998) found external rotation was induced with increased abduction. Conversely internal rotation occurred with decreased abduction. These authors didn’t differentiate between anterior and posterior portions of the muscle.

    Entrapment neuropathy of the suprascapular nerve

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

    • Suprascapular notch.
    • Spinoglenoid notch.
    • Supraspinatus fascia: within the supraspinatus fascia in the supraspinous fossa between the suprascapular notch and spinoglenoid notch. Bektas et al (2003) found in cases of an absent spinoglenoid ligament a septum formed by the thickening of the fascial cover of the distal third of the supraspinatus and infraspinatus muscles. It originated from the spinoglenoid notch and extended into the posterior capsule. They named this structure the spinoglenoid septum. The suprascapular nerve passed between the bony margin of the spinoglenoid notch and the medial concave margin of the spinoglenoid septum. This septum may be a cause of dynamic compression of the suprascapular nerve.
    • Between the deep fascia of the Subscapularis and the superior transverse scapular ligament (STSL) (Tasaki et al 2015). Refer to ‘Subscapularis’.
    • 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 (2016). 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)?

    Infraspinatus

    Origin: infraspinous fossa and infraspinatus fascia.

    Insertion: greater tuberosity. The tendon runs anteriorly to attach to the supraspinatus and then continues to run anteriorly over the rotator interval to the subscapularis. The tendon also runs continuous with the teres minor.

    The infraspinatus fascia is a tough sheet of connective tissue that covers the infraspinatus fossa of the scapula and the muscle (Moccia et al 2016). Tsaki et al (2015) found the Infraspinatus split into three muscular partitions: superior, middle and inferior partitions. Each partition is bounded and separated by fascia.

    Fabrizio and Clemente (2014) gave the following description of the three partitions of the muscle:

    Superior muscle partition: arises from the inferior surface of the scapular spine and the deep surface of the infraspinatus fascia at the attachment of the fascia to the spine of scapula. The fibers attached distally to the posterior aspect of the greater tuberosity. Gagey (1993) found the superior part of the infraspinatus contained a significant fibrous reinforcement.

    Middle muscle partition: arose from the medial boarder of the scapula and from the posterior surface of the infraspinous fossa. The fibers course superolaterally toward to the glenoid cavity deep to the superior and inferior partitions. The middle partition blended with the tendons of the superior and inferior partitions and attached on the posterior aspect of the greater tuberosity. Tsaki et al (2015) found the middle partition of the Infraspinatus strongest to posteriorly stabilise the shoulder.

    Inferior muscle partition: arose from the inferior one-third of the medial boarder of the scapula, the infraspinous fossa, and the deep surface of the infraspinatus fascia. The fibers coursed superior-lateral parallel to the lateral border of the scapula. The fibers attached to the greater tuberosity.

    The fascia of the Infraspinatus has six components (Moccia et al 2016):

    1. Medial band: a band of fascia extending from the midspine of the scapula towards the inferior angle.
    2. Superomedial band: a band of fascia extending from the medial border of the scapula, near the origin of the spine of the scapula, toward the lateral border. In the three divisions of the Infraspinatus noted by Fabrizio and Clemente (2014) this band of fascia maybe the one cited in the article as separating the superior from the middle portion of the Infraspinatus.
    3. Inferomedial band: a band of fascia extending from the inferior angle of the scapula toward the scapular neck and glenoid fossa. The Infraspinatus fibers originate most strongly from the deep aspect of the inferomedial band. In the three divisions of the Infraspinatus noted by Fabrizio and Clemente (2014) this band of fascia maybe the one cited in the article as separating the middle and the inferior portions of the Infraspinatus.
    4. The insertion of the posterior belly of the deltoid muscle is inserted into the infraspinatus fascia inferior to the scapular spine.
    5. A band of fascia extending transversely from the posterior deltoid to anchor near the teres minor and teres major muscles.
    6. A retinacular sheet of fascia deep to the posterior deltoid and superficial to the infraspinatus and teres minor muscles as they approach the proximal humerus. Cooper et al (1993) claimed this fascia ran continuous with the clavipectoral fascia around the lateral aspect of the proximal humerus. On reviewing the anatomy the most likely attachment of the fascia at this point is to the lateral intermuscular septum.

    Myofascial trigger points are located in the medial band, inferomedial band,and the superomedial band,respectively. Referred pain patterns to the anterior and middle deltoid regions might be a result of the infraspinatus fascia acting as an intermediary between the two muscles (Moccia et al 2016).

    This arrangement of the fascia lends it prone to causing a compartment syndrome involving the infraspinatus and teres minor muscles (Moccia et al 2016). 

    Additional bands of this fascia include (Moccia et al 2016):

    (1) A loose, superficial fascia between the superior aspect of the latissimus dorsi muscle across the infraspinatus.

    (2) A thin sheet of superficial connective tissue extending between the superior boarder of the latissimus dorsi muscle to the spine of the scapula.

    Action

    Middle: Tsaki et al (2015) found the middle partition of the Infraspinatus posteriorly stabilises the shoulder. 

    Inferior: Hughes et al (2014) found isometric external rotation of the shoulder is most active in this part of the muscle irrespective of shoulder position. 

    Teres Minor

    Origin: upper two thirds on the dorsal aspect of the scapula and the two aponeurotic laminae seperating it from the teres major and infraspinatus.

    Insertion: greater tubercle and a humeral attachment between the greater tubercle and triceps attachment and the joint capsule.

    Gagey (1993) found the teres minor contained significant fibrous re-enforcement.

    Action: lateral rotator and adductor.

    Chafik (2013) found the fascia of the Teres Minor had two distinct characteristics:

    (1)  A stout, inflexible fascial compartment enveloping the teres minor muscle. This compartment may be the potential site of compression and tethering of the primary motor nerve to teres minor.

    (2)  A continuous fascia enveloping both the infraspinatus and teres minor muscles. 

    Subscapularis

    Origin: costal surface of the scapula, aponeurosis that covers the subscapularis and separates it from the long head of triceps and teres major. It is contiguous with the Teres Major and Latissimus Dorsi.

    Insertion: extrarticular and intraarticular.

    (1) Extraarticular:

    (a) Anterior capsuloligamentous complex (ACLC) (Kordasiewicz et al 2016). Recognised as a single structure it comprises the anterior joint capsule and Middle and Inferior Glenohumeral Ligaments.

    (b) Lesser tubercle (Kordasiewicz et al 2016).

    (2) Intraarticular: this explains the presence of synovial tissue around the tendon (Abe et al 2014). 

    The Middle and Inferior Glenohumeral Ligaments develop postnatally in response to mechanical demands from the Subscapularis and Biceps. The Inferior Glenohumeral Ligament development is more closely associated with the Bicep muscle attachment. The Middle Glenohumeral Ligament develops postnatally to cover the large opening (subcoracoid bursa) below the Superior Glenohumeral Ligament and to assist the intra-articular course of the Subscapularis.

    Wickham et al (2014) divided the Subscapularis into superior and inferior segments. These segments were not only structurally different but exhibited differential activity depending on shoulder position. They hypothesised this could indicate different roles for each segment of the subscapularis in shoulder movement.

    Superior portion of the Subscapularis: this part of the muscle is thicker. Gagey (1993) found a strong fibrous framework within the upper part of the subscapularis.

    Inferior portion of the Subscapularis: is considered mechanically weaker and more susceptible to injury. It enhances dynamic stability of the joint with injury to this segment resulting in greater functional limitations (Whickham et al 2014).

    Clark & Harryman (1992) found the biceps tendon was ensheathed by interwoven fibers derived from the subscapularis (and supraspinatus) tendons. This has an effect of stabilising the biceps tendon. Arai et al (2010) found stabilisation of the biceps tendon relied on tension in the superior glenohumeral ligament and the most superior insertion point of the subscapularis from behind this ligament.

    Subscapularis fascia

    The subscapularis fascia is the thinnest of the different fascia surrounding the muscles of the scapula. Laterally it continues with the axillary and infraspinatus fascia and superiorly with the supraspinatus fascia.

    Primary action of the upper and lower subscapularis

    The lower portion of the subscapularis primary function is to stabilise and centralise the humeral head during movement. It therefore activates before the superior portion of the subscapularis to counteract any shearing movement of the humeral head. For instance in abduction deltoid contraction can cause a superior shear of the humeral head so the lower subscapularis counteracts this by pulling down and produces an inferior shear. It also resisting anterior shear of the humeral head in abduction and external rotation.

    Superior subscapularis:

    • Internal rotation at mid and high levels of abduction. Rathi et al (2017) found the primary role of the upper subscapularis was as an internal rotator.
    • Forward punch/push up plus exercises (Whickham et al 2016).

    Inferior subscapularis:

    Due to its stabilising function in maintaining the humeral head in a neutral position the inferior subscapularis is particulary active during abduction and flexion.

    • Humeral head depression (inferiorly depresses the humeral head to counteract the superior pull of the deltoid).
    • In mid ranges of abduction contributes the majority of resistance to anterior translation.

    Accessory Subscapularis (aka accessory subscapularis-teres-latissimus muscle)

    This muscle is not always present and anatomically is highly variable:

    Origin: anterior surface of the subscapularis (Pires et al 2017) on its superior lateral aspect (Breisch 1986), lateral margin of the scapula and the latissimus dorsi (Kameda 1976).

    Insertion: into the shoulder joint (Pires 2017) and lesser tubercle (Breisch 1986).

    Entrapment neuropathies from the Subscapularis

    (1) Axillary and Inferior Subscapular nerve.

    (2) Radial nerve.

    (3) Suprscapular Nerve.

    (1) Axillary and Inferior Subscapular nerve

    Between the Subscapularis and the accessory subscapularis passes the axillary nerve (Pires et al 2017) and inferior subscapular nerve (Breisch 1986) that run through a myotendinous tunnel (Breisch 1986). 

    (2) Radial nerve

    Kasmeda (1976) found an anomalous muscle passing through the brachial plexus designated the 'accessory subscapularis-teres-latissimus muscle'.

    This muscle arose near the lateral margin of the scapula, either from the surface of the subscapularis muscle or from the latissimus dorsi tendon or from both of those sources. It ran obliquely upward to fuse with the insertion of the subscapularis.

    Depending on its anatomy the muscle can separate the radial nerve into two roots.

    (3) Suprascapular nerve

    The deep fascia of the Subscapularis attaches posteriorly to the costal surface of the scapula. At the superior end of this between the base of the coracoid and the medial end of the scapula notch runs the superior transverse scapular ligament (STSL). Between the deep fascia of the subscapularis and the STSL is a space that the suprascapular nerve runs through (Tasaki et al 2015). 

    Rotator Interval

    The rotator interval comprises the space between the supraspinatus and subscapularis tendons (Jost et al, 2000) in the anterosuperior aspect of the glenohumeral joint.

    It is composed of and represents a complex interaction of the supraspinatus, subscapularis, coracohumeral ligament, superior glenohumeral ligament, and glenohumeral joint capsule (Jost 2000).

    Lesions of the rotator interval may result in (Arai et al 2010):

    • Glenohumeral joint contractures.
    • Shoulder instability.
    • Lesions to the long head of the bicep tendon. The bicep tendon is ensheathed by interwoven fibers derived from the subscapularis and supraspinatus tendons (Clark & Harryman 1992).

    Deltoid

    Origin: lateral third of clavicle, acromion (from 4 to 5 tendinous insertions, Moatshe et al 2018) and spine of scapula.

    Insertion: deltoid tuberosity. Lorne et al (2001) found eight half-cone shaped distal fibrous structures that merged together into the distal tendon of the deltoid. The intermediate fibers of the deltoid contained four deep fibrous intramuscular bands that glide inside these. The anterior and posterior parts of the deltoid muscle lacked such bands.

    Anterior fibers: The anterior part of the deltoid muscle lacked fibrous bands (Lorne et al 2001).

    Intermediate fibers: the intermediate fibers have a short fiber length, complex multipennate structure, and high cross sectional area (Peterson & Rayan 2011). From 4 to 5 tendinous insertions (Moatshe et al 2018) four fibrous intramuscular bands descend from the acromion to interdigitate with three septa ascending from the deltoid tubercle. The septa are connected by short muscle fibers that provide powerful traction. Lorne et al (2001) proposed the role of the fibrous bands was not only to help repair the muscle but to stop migration and deformation of the muscle during strong contraction.

    Posterior fibers: The posterior parts of the deltoid muscle lacked fibrous bands (Lorne et al 2001).

    Audenaert and Barbaix (2008) proposed the deltoid to be divided into at least seven functional (not anatomical) muscle segments all of which have the potential to be independently coordinated by the central nervous system.

    Fascial relations of the deltoid

    The superficial deltoid fascia continues with the fascia covering the trapezius muscle. The deep deltoid fascia inserts into the spine of scapula and clavicle.

    Rispoli et al (2009) found the deltoid tendon and fibrous aponeurosis was in continuity with the lateral intermuscular septum posteriorly and the lateral aspect of the brachialis and deep brachial fascia anteriorly. Stecco et al (2008) found the posterior deltoid inserted fibers directly into the posterior portion of the brachial fascia.

    Action

    Anterior fibers: shoulder flexion and adduction (with clavicular portion of the pectoralis major, Barberini 2014) and rotates arm medially (with pectoralis major).

    Intermediate: abductor. In the initial phase of abduction it translates the humeral head superiorly (with the Supraspinatus). Hereter et al (2014) found the tightening and elevation function of the intermediate fibers increased from its posterior to its anterior segment. This indicates a greater stabilizing effect, and tightening of, the anterior segment of the intermediate fibers in for example rotator cuff tears.

    Posterior: external rotator and extensor (with Latissimus Dorsi and teres major)

    Variations in anatomy

    Kamburogu et al (2008) found continuation and fusion of the fibers of the deltoid muscle into the trapezius, pectoralis major; vertebral border of the scapula, infraspinous fascia, and the axillary boarder of the scapula.

    Kamburogu et al (2008) found the posterior fibers of the deltoid can be enclosed in a distinct fascial sheet and arise from the middle 1/3 of the medial boarder of the scapula.

    The posterior part of the deltoid can be enclosed within a separate fascial sheath (Kayikçioglu, 1993).

    Coracobrachialis (Maiti and Bhattacharya 2018)

    Origin: coracoid process with a conjoint origin of the short head of biceps. It is formed of two fused heads.

    Insertion: antebrachial fascia and the medial epicondyle of the humerus. 

    Variations include the coracobrachialis brevis. This muscle can insert proximally to the capsule of shoulder joint, root of coracoid process or conoid ligament of clavicle. It can insert distally into the medial intermuscular septum, medial supracondylar ridge, medial epicondyle and ligament of Struthers.

    Entrapment neuropathies of the coracobrachialis:

    (1) Musculocutaneous nerve.

    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.

    (2) Median nerve

    The lower head of the coracobrachialis which is usually suppressed in human beings is sometimes present as the ligament of Struthers. The Median nerve and brachial artery passes deep to this ligament and are vulnerable to compression by being entrapped between the ligament and the bony surface.

    Fascia's proprioceptive function in the shoulder

    Stecco et al (2007, 2008) hypothesised the role of muscular insertions in pulling on the fascia to stimulate the proprioceptors in fascia.

    Examples of the myofascial continuity of the fascia around the shoulder includes:

    1. Brachial fascia

    The brachial fascias myofascial connections include the:

    • Fascia over the clavicular part of the pectoralis major runs from the clavicle (deep layer of pectoralis fascia) and the superficial lamina of the deep cervical fascia (superficial layer of pectoralis fascia) to attach to the anterior brachial fascia. Barberini (2014) found the clavicular part of the pectoralis major a later evolutionary development designed to optimise stabilisation of the upper limb to the thorax.
    • Fascia from the costal part of the pectoralis major runs from the sternum (deep layer), contralateral pectoral fascia (superficial layer), rectus abdominis muscle and contralateral external oblique fascia to attach to the medial brachial fascia and medial intermuscular septum.
    • Fascia from the latissimus dorsi sends fibrous lamina to the tricpes brachial fascia.
    • Posterior deltoid muscle fibers attached to the posterior portion of the brachial fascia.
    • Rispoli et al (2009) found the deltoid tendon and aponeurosis was continuous with the deep brachial fascia anteriorly.

    2. Infraspinatus fascia (Moccia et al 2016)

    The Infraspinatus fascia has musclar connections to the:

    • Infraspinatus.
    • Posterior deltoid.
    • Teres Minor.
    • Teres Major.

    3. Lateral intermuscular septum (Rispoli et al 2009):

    The lateral intermuscular septum has connections to the:

    •  Deltoid tendon and its aponeurosis attach on to the lateral intermuscular septum.

    These muscular attachments pull on the fascia that stimulate the mechanoreceptors in the fascia. The complexity of this model also includes that one muscle attaches onto to various different fascial sheets and if one muscle e.g. levator scapula, pulls on another muscle e.g. supraspinatus could this pull on the supraspinatus fascia and alter proprioceptive function?

    References

    Tendons, ligaments, and capsule of the rotator cuff. Gross and microscopic anatomy (1992). Clark JM, Harryman DT

    The insertional footprint of the rotator cuff: an anatomic study (2006). Curtis AS, Burbank KM, Tierney JJ, Scheller AD, Curran AR.

    Influence of distinct anatomic subregions of the supraspinatus on humeral rotation (2010). Gates JJ, Gilliland J, McGarry MH, Park MC, Acevedo D, Fitzpatrick MJ, Lee TQ.

    Tendinous muscular insertions onto the deep fascia of the upper limb. First part: anatomical study (2007). Stecco C, Gagey O, Macchi V, Porzionato A, De Caro R, Aldegheri R, Delmas V.

    Fibrous frame of the rotator cuff. The concept of fibrous lock (1993). Gagey O, Arcache J, Welby F, Gagey N.

    Rotational action of the supraspinatus muscle on the shoulder joint (1998). Ihashi K, Matsushita N, Yagi R, Handa Y.

    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.

    Fascial bundles of the infraspinatus fascia: anatomy, function, and clinical considerations. (2016).Moccia D, Nackashi AA, Schilling R, Ward PJ.

    Anatomical structure and nerve branching pattern of the human infraspinatus muscle. (2014). Fabrizio PA, Clemente FR.

    Supporting layers of the glenohumeral joint. An anatomic study. (1993). Cooper DE, O'Brien SJ, Warren RF.

    Isolation of infraspinatus in clinical test positions. (2014). Hughes PC, Green RA, Taylor NF.

    Teres minor muscle and related anatomy. (2013). Chafik D, Galatz LM, Keener JD, Kim HM, Yamaguchi K.

    A new look at the shoulder anterior capsuloligamentous complex complementing the insertion of the subscapularis tendon-Anatomical, histological and ultrasound studies of the lesser tuberosity enthesis (2016). Kordasiewicz B, KiciÅ„ski M, Pronicki M, MaÅ‚achowski K, Brzozowska M, Pomianowski S.

    Variation of the subscapularis tendon at the fetal glenohumeral joint (2014) By Shin-ichi ABE, Mitsuhiro AOKI, Tadashi NAKAO, Masaaki KASAHARA, Jose Francisco RODRIGUEZ-VAZQUEZ, Gen MURAKAMI, Baik Hwan CHO

    Functional anatomy of the superior glenohumeral and coracohumeral ligaments and the subscapularis tendon in view of stabilization of the long head of the biceps tendon (2010). Arai R, Mochizuki T, Yamaguchi K, Sugaya H, Kobayashi M, Nakamura T, Akita K.

    The variable roles of the upper and lower subscapularis during shoulder motion (2014). James Wickham, Tania Pizzari, Simon Balster, Charlotte Ganderton, Lyn Watson.

    Accessory subscapularis muscle - A forgotten variation? (2017). Pires LAS, Souza CFC, Teixeira AR, Leite TFO, Babinski MA, Chagas CAA.

    A rare human variation: the relationship of the axillary and inferior subscapular nerves to an accessory subscapularis muscle (1986). Breisch EA.

    An anomalous muscle (accessory subscapularis-teres-latissimus muscle) in the axilla penetrating the brachial plexus in man (1976). Kameda Y.

    Anatomy and functional aspects of the rotator interval (2000). Jost B, Koch PP, Gerber C.

    Qualitative and Quantitative Anatomy of the Proximal Humerus Muscle Attachments and the Axillary Nerve: A Cadaveric Study. (2018). Moatshe G, Marchetti DC, Chahla J, Ferrari MB, Sanchez G, Lebus GF, Brady AW, Frank RM, LaPrade RF, Provencher MT.

    Shoulder and upper arm muscle architecture. (2011). Peterson SL, Rayan GM.

    The fibrous frame of the deltoid muscle. Its functional and surgical relevance (2001). Lorne E, Gagey O, Quillard J, Hue E, Gagey N. 

    Separate segments within the deltoid muscle: Anatomical variants or wishful thinking? (2008). Audenaert E & Barbaix

    The clavicular part of the pectoralis major: a true entity of the upper limb on anatomical, phylogenetic, ontogenetic, functional and clinical bases. Case report and review of the literature (2014). Barberini F. 

    Coaptation/elevation role of the middle deltoid muscle fibers: a static biomechanical pilot study using shoulder MRI. (2014). Hereter Gregori J, Bureau NJ, Billuart F, Hagemeister N.

    An unusual variation of deltoid muscle (2008). Haldun O. KamburoÄŸluOmer F. Boran, Mustafa F. Sargon, and Abdullah Keçik

    An anatomic variation of the deltoid muscle (case report) (1993). Kayikçioglu A, Celik HH, Yilmaz E.

    Teres minor muscle and related anatomy. (2013) Chafik D, Galatz LM, Keener JD, Kim HM, Yamaguchi K.

    The upper and lower segments of subscapularis muscle have different roles in glenohumeral joint functioning. Rathi S, Taylor NF, Green RA.

    The anatomy of the deltoid insertion (2009). Rispoli DM, Athwal GS,  Sperling JW, Cofield RH

    The expansions of the pectoral girdle muscles onto the brachial fascia: morphological aspectsand spatial disposition. (2008). Stecco CPorzionato AMacchi VStecco AVigato EParenti ADelmas VAldegheri RDe Caro R.

    Tendinous muscular insertions onto the deep fascia of the upper limb. First part: anatomical study. (2007). Stecco C, Gagey O, Macchi V, Porzionato A, De Caro R, Aldegheri R, Delmas V. 

    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 (2018). Grigoriță L, Vaida MA, Jianu A.

    Arthroscopic Treatment of Suprascapular Nerve Neuropathy (2012). Dipit Sahu, Robert Fullick and Laurent Lafosse 

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