Trail Guide Shoulder OIAs

S EEE R REREREREERREEERENEREEERRERRERNERENRRRRRERARRORAEE Deltoid The triangle-shaped deltoid is located on the cap of the shoulder. The origin of the deltoid (which is, interestingly enough, identical to the insertion of the trapezius) curves around the spine of the scapula and clavicle forming a “V" shape. From this broad origin, the Middle fibers converge down the arm to attach at the deltoid fibers tuberosity (2.36). The deltoid fibers can be divided into three segments: the anterior, middle and posterior fibers. All three groups abduct the humerus, but the anterior and posterior fibers are antagonists in both flexion/ extension and medial/lateral rotation. fibers All fibers: Abduct the shoulder (glenohumeral joint) Anterior fibers: 2.36 Lateral view of deltoid Flex the shoulder (G/H joint) showing the three segments Medially rotate the shoulder (G/H joint) When Do You Use Your Deltoid? - Virtually all movements that involve the shoulder - Slipping your arms into ajacket | « Raking, shoveling, sawing m « Rowing a dinghy Horizontally adduct the shoulder (G/H joint) Posterior fibers: Extend the shoulder (G/H joint) Laterally rotate the shoulder (G/H joint) Horizontally abduct the shoulder (G/H joint) /:\. '\\\ o gy L { A 3] Lateral one-third of clavicle, acromion L,\ ™~ § and spine of scapula o} y i 2.37 Origin and Sl insertion of deltoid Deltoid tuberosity Axillary C5, 6 @ Belly of the deltoid 1) Seated. Locate the spine of the scapula, the acromion and the lateral one-third of the clavicle. Note the “V” shape these landmarks form. 2) Locate the deltoid tuberosity. 3) Palpate between these landmarks to isolate the superficial, convergent fibers of the deltoid. Be sure to explore the deltoid’s most anterior and posterior aspects. Are the fibers you feel superficial and do they 2L converge toward the deltoid tuberosity? If your s partner alternately abducts and releases, do you feel / - D the fibers contract and relax (2.38)? ' 2.38 Anterior/lateral view deltoid del-toid Grk. delta, capital letter D (A) in the Greek alphabet Shoulder & Arm | 67

2.39 Lateral view of right shoulder. Use both hands to sculpt out the edges of the deltoid, following them down to the tuberosity. sy @Deltoid as antagonist to itself To feel the antagonistic abilities of the deltoid's anterior and posterior fibers: 1) Shaking hands with your partner, place your other hand on the deltoid. 2) Keeping his elbow next to his side, ask your partner to medially and laterally rotate his arm against your resistance. Can you sense the anterior fibers contracting upon medial rotation and relaxing upon lateral rotation, and vice versa for the posterior fibers? Superior nuchal line of the occiput Spinous process of C-7 Middle fibers { Lower fibers £ i, ‘ \{/L ; 1% { ; \ k f ‘l . - \( Spinous process é‘ i of T-12 Lf | O — 2.40 Posterior view of trapezius 68 | Trail Guide to the Body Trapezius | The trapezius lies superficially along the upper back and neck. Its broad, thin fibers blanket the shoulders, attaching to the occiput (the bone at the base of the head, p. 231), lateral clavicle, scapula and spinous processes of the thoracic vertebrae (2.40, 2.42). The trapezius fibers can be divided into three groups: upper (descending) fibers, middle fibers and lower (ascending) fibers. The upper and lower fibers are antagonists in elevation and depression of the scapula, respectively. All fibers of the trapezius are easy to palpate. 2.47 Origin and insertion of trapezius

’D"",””,,WU’OJ,\L'\'V-’_ Upper fibers: Bilaterally Extend the head and neck Unilaterally Laterally flex the head and neck to the same side External occipital protruberance Rotate the head and neck to the opposite side Elevate the scapula (scapulothoracic joint) Acromion Upwardly rotate the scapula (S/T joint) Middle fibers: Adduct the scapula (S/T joint) Stabilize the scapula (S/T joint) Lower fibers: Depress the scapula (S/T joint) Upwardly rotate the scapula (S/T joint) External occipital protuberance, medial portion of superior nuchal line of the occiput, ligamentum 2.42 Lateral view nuchae and spinous processes of C-7 through T-12 of trapezius Lateral one-third of clavicle, acromion and spine of the scapula Spinal portion of cranial nerve XI (accessory) and ventral ramus C2, 3, 4 () Upper fibers of the trapezius 1) Prone. These fibers form the easily accessible flap of muscle lying across the top of the shoulder. Along the posterior neck they are surprisingly skinny, each being only an inch wide. 2) Grasp the superficial tissue on the top of the Yv p shouder and feel the upper trapezius fibers. Take \ t L note of their slender quality (2.43). % T s 3) Follow the fibers superiorly toward the base of the S il head at the occiput. To feel the fibers along the posterior neck contract, stand at the side of the table m and ask your partner to extend his head “a quarter inch off the face cradle” Then follow the fibers inferiorly to the lateral clavicle. == s the muscle you are grasping thin and superficial? 2N Grasp the fibers along the top of the shoulder and have your partner elevate his scapula gently toward his ear. Do the muscle fibers become taut? As your partner extends his head, you will likely see two parallel “speed bumps” running along the posterior neck. These bulges are formed primarily by the deeper semispinalis capitis muscle (p. 201), with the trapezius muscles draped on top. trapezius tra-pee-ze-us Grk. alittle table or trapezoid shape nuchae nu-kay L. nape of neck Shoulder & Arm | 69 occiput ok-si-put L. the back of the skull

RN NS ... et A/‘K g‘; ] b \ Latissimus Dorsi and Teres Major The latissimus dorsi is the broadest muscle of the back. Its thin, superficial fibers originate at the low back, ascend the side of the trunk and merge into a thick bundle at the axilla (2.46). Both ends of the latissimus dorsi are difficult to isolate; however, its middle portion next to the lateral border of the scapula is easy to grasp. The teres major is called “lat’s little helper” because it is a complete synergist with the latissimus dorsi (2.47). It is superficial and located along the scapula’s lateral border between the latissimus dorsi and teres minor. Although they share names, the teres major and teres minor rotate the arm in opposite directions—the major medially, the minor laterally. The latissimus dorsi and teres major are sometimes called the “handcuff muscles;’ since their actions collectively bring the arms into the “arresting” position! Latissimus Dorsi Extend the shoulder (glenohumeral joint) Adduct the shoulder (G/H joint) Medially rotate the shoulder (G/H joint) Inferior angle of scapula, spinous processes of last six thoracic vertebrae, last three or four ribs, thoracolumbar aponeurosis and posterior iliac crest n Intertubercular groove of the humerus Thoracodorsal C6,7, 8 Teres Major Extend the shoulder (glenohumeral joint) Adduct the shoulder (G/H joint) Medially rotate the shoulder (G/H joint) Inferior angle and lower one-third of lateral border of the scapula n Crest of the lesser tubercle of the humerus Lower subscapular C5, 6, 7 latissimus dorsi la-tis-i-mus dor-si L. widest of the back teres teh-reez Thoracolumbar aponeurosis Posterior iliac crest 2.46 Lateral/posterior view of latissimus dorsi 2.47 Posterior view of teres major The latissimus dorsi not only moves the arm, but, because of its broad origin, can also affect the trunk and spine. Contraction of the left latissimus dorsi assists in lateral flexion of the trunk to the left. If the arm is fixed, as when hanging from a bar, the latissimus will assist in extension of the spine and tilting of the pelvis anteriorly and laterally. L. rounded, finely shaped Shoulder & Arm | 71