Superficial Back & Shoulder Muscles PDF

Back & Shoulder DPM Program Learning Objectives: 1. Describe the extrinsic (superficial) muscles of the back in terms of their origins, insertions, innervations, and major actions. 4.0 2. Define dermatome and myotome. 4.0 3. Describe the cutaneous innervation of the back. 4.0 4. Differentiate betwee...

Back & Shoulder DPM Program Learning Objectives: 1. Describe the extrinsic (superficial) muscles of the back in terms of their origins, insertions, innervations, and major actions. 4.0 2. Define dermatome and myotome. 4.0 3. Describe the cutaneous innervation of the back. 4.0 4. Differentiate between the extrinsic and intrinsic back muscles. 4.0 5. Describe the intrinsic muscles of the back in terms of their innervations and major actions. 3.0 6. Describe the origins and insertions of the intrinsic back muscles. 2.0 7. Describe the osteological features and boundaries of the suboccipital triangle and its contents. 2.0 8. Describe the fascia of the back, including the thoracolumbar fascia. 2.0 9. Identify the osteological features of the back as demonstrated on diagnostic imaging. 4.0 (will be looked at in lab) 10. Identify soft-tissue structures of the back on sagittal and transverse CTs and MRIs. 3.0 (will be looked at in lab) 11. Describe the structure and function of the rotator cuff. 4.0 12. Describe the clinical significance of rotator cuff injuries. 4.0 1 Myotome A myotome is a group of muscles which are innervated by a single spinal nerve which has derived from the same embryological segment. (developed from somites) Myotome testing can be difficult since individual muscles can be innervated by more than one nerve and by nerves that originate from different spinal cord levels. Usually done by checking a patient’s ability to perform specific actions and checking for muscle weakness 2 Dermatome Dermatome which is an area of skin innervated by a single spinal nerve. (develop from somites) Dermatome maps show the sensory distribution of each dermatome across the body. Clinicians can use test touch with a dermatome map as a way to localize lesions, damage, injury to specific spinal nerves, and to determine the extent of the injury. Posterior branches of spinal nerves innervate the intrinsic muscles of the back and adjacent skin. 3 Introduction: Muscles of the Back The back is the posterior aspect of the torso. It originates superiorly from the base of the skull and extends inferiorly just above the gluteal region. The muscles of the back can divided into two groups: extrinsic and intrinsic Extrinsic Back Muscles (Superficial Group) -Primarily involved in movements of the upper limb -Hypaxial -Trapezius, Latissimus dorsi, Rhomboideus major, Rhomboideus minor, Levator scapulae Extrinsic Back Muscles (Intermediate Group): -Attach to ribs (may have a respiratory function) -Hypaxial -Serratus Posterior Superior -Serratus Posterior Inferior Intrinsic Muscles of the Back (superficial group, intermediate group, deep group) -Primarily involved in movements of the vertebral column and head -Epiaxial: -separated from overlying hypaxial muscles by thoracolumbar fascia -innervated by dorsal rami of spinal nerves -Spinotransversalis muscles (superficial): -Splenius (capitis & cervicis) -Erector Spinae (intermediate): -Spinalis (medial), Longissimus, Iliocostalis (lateral) -Transversospinalis muscles (deep): -multifidus, rotatores, semispinalis 4 Extrinsic Muscles of the Back: Superficial Layer & Intermediate Group Ligamentum nuchae Trapezius Levator scapulae Levator scapulae Rhomboid minor Rhomboid major Posterior layer of thoracolumbar fascia Latissimus dorsi Superficial Layer (Thoracoappendicular) Intermediate Layer 5 Extrinsic muscles of the Back (Superficial and Intermediate) Muscle Origin Insertion Actions Innervation TRAPEZIUS Superior nuchal line, external occipital protuberance, ligamentum nuchae, SP C7-T12 Lateral one-third of the clavicle and acromion and spine of scapula Elevates scapula, retracts (adducts) scapula, depresses scapula, rotates the scapula upward, stabilizes scapula Spinal accessory n. (CN XI) Ventral rami of C3 and C4 LATISSIMUS DORSI SP T7-T12, thoracolumbar fascia, iliac crest, ribs 10-12 Floor of intertubercular sulcus of humerus Extends, adducts, and medially rotates humerus Thoracodorsal n. (also middle subscapular n. ) LEVATOR SCAPULAE TP C1-C4 Superior angle of scapula Elevates and rotates scapula downward, fixes scapula against thorax Dorsal scapular n. RHOMBOID MAJOR SP T2-T5 Medial border of scapula below spine Retracts and rotates the scapula to tilt the glenoid cavity inferiorly RHOMBOID MINOR Ligamentum nuchae, SP C7-T1 Medial border of scapula at spine SERRATUS POSTERIOR SUPERIOR SP C7-T3 Superior borders of ribs 2-5 lateral to their angles Elevates ribs 2-5 Anterior rami T1-4 SERRATUS POSTERIOR INFERIOR SP T11-L2 Inferior border of ribs 9-12 lateral to their angles Depresses ribs 9-12 Anterior rami T9-T12 Abbreviations: SP, spinal process; TP, transverse process; C, cervical vertebrae; T, thoracic vertebrae; L, lumbar vertebrae; VT, vertebral column 6 Intrinsic Muscles of the Back: Superficial and Intermediate Ligamentum nuchae Spinalis Levator scapulae Longissimus Iliocostalis Deep back Spinotransversalis muscles Erector Spinae 7 Intrinsic Muscles of the Back (Superficial and Intermediate Group) Muscle SPLENIUS CAPITIS SPLENIUS CERVICIS Origin Insertion Actions Ligamentum nuchae, SP C7-T4 Mastoid process, lateral one-third of superior nuchal line Unilateral-laterally flexes and rotates the head and neck to same side Bilateral-extends head and neck Spinous processes of T3T6 TP C1-C4 Unilateral-Laterally flexes an rotates head to the same side Bilateral-extend the head and neck SP of T and C Unilateral-laterally flexes VT to same side Bilateral-extends VT and head, stabilizes VT Innervation Posterior rami of middle cervical region Posterior rami of lower cervical reiogn Erector Spinae (Spinalis, Longissimus, Iliocostalis) SPINALIS LONGISSIMUS ILIOCOSTALIS Median sacral crest, posterior surface sacrum, SP L and lower T, medial part of iliac crest Between tubercles and angles of ribs and TP of T and C Angles of lower ribs and TP of C Posterior rami of lower cervical nerves 8 Intrinsic Muscles of the Back: Deep Group SEMISPINALIS Deep to erector spinae Semispinalis thoracis, cervicis, capitis ROTATORES LONGI (11 PAIRS) The long rotators run from the transverse processes to the spinous processes two vertebrae above. ROTATORES BREVES (11 PAIRS) The short rotators extend between the transverse and spinous processes of adjacent vertebrae. MULTIFIDUS Consists of a number of segmental muscles that run along the length of the vertebral column from the sacrum to the axis. Deep to Semispinalis and basically arise from the transverse processes and insert into the spinous processes 2 – 4 segments above their origin. Rotatores brevis Rotatores longus Best developed in the lumbar and cervical regions. Actions: Unilateral Contraction: -Rotate the neck and trunk to the opposite side. Bilateral Contraction: 9 -Extend the vertebral column. INTERSPINALES Found in pairs which connect the apices of adjacent spinous processes from the sacrum to the axis. -Best developed in the cervical region and may be absent in the thoracic region. LEVATOR COSTARUM 12 pairs of segmental muscles found in the thoracic region. Run from the transverse processes of C7 – T11 to the superior border of the ribs below the vertebra of origin. Unilateral Contraction: -Elevate the ribs, therefore, assist in inspiration. -Laterally bend the vertebral column to the same side. Bilateral Contraction: -Extend the vertebral column. INTERTRANSVERSARII Small segmental muscles connect adjacent transverse processes in the cervical, lower thoracic, and lumbar regions. Well developed in the lumbar and cervical regions. 10 Fascia of the Back As elsewhere, the fascia of the back may be divided into a superficial layer and a deep layer. SUPERFICIAL FASCIA This is a thick fatty layer in the back which is continuous with the superficial fascia elsewhere. DEEP FASCIA -This layer invests the deep muscles of the back and is continuous with the deep fascia of the neck. -In the lower thoracic and the lumbar regions the deep fascia is modified to form what is known as the Thoracolumbar (Lumbodorsal) Fascia. THORACOLUMBAR (LUMBODORSAL) FASCIA -In the lower thoracic and the lumbar regions the deep fascia is much thicker and represents not only fascia but also the fused aponeuroses of several muscles. This combination of fascia and aponeuroses is what is known as the thoracolumbar fascia. -In the lumbar region it is considered to consist of 3 layers: anterior middle posterior Between the posterior and middle layers one finds the intrinsic muscles of the back. Between the anterior and middle layers, the Quadratus lumborum is found. 11 12 Suboccipital Triangle The suboccipital region is that area between the occipital bone and the atlas and axis. Situated deep to the Semispinalis capitis in this area 4 pairs of small muscles are found and are called the suboccipital muscles. Boundaries: Superior and Medially Rectus capitis posterior major Superior and Laterally Obliquus capitis superior Inferior and Laterally Obliquus capitis inferior Floor: Posterior atlantooccipital membrane Posterior arch of the atlas (C1) Roof: Semispinalis capitis The suboccipital triangle is clinically important for it contains the vertebral artery and the dorsal rami of c1 (suboccipital nerve). 13 14 Muscles of the Suboccipital Triangle Muscle Origin Insertion Actions Innervation RECTUS CAPITIS POSTERIOR MAJOR Spinous process of the axis (C2) Occipital bone just inferior to the inferior nuchal line Occipital bone just inferior to the inferior nuchal line Unilateral Contraction: Rotates the head to the ipsilateral side Bilateral Contraction: Extends the head RECTUS CAPITIS POSTERIOR MINOR Posterior tubercle of the posterior arch of the atlas (C1) Occipital bone just inferior to the inferior nuchal line and medial to Rectus capitis posterior major Extends head the dorsal rami of c1 (suboccipital nerve) OBLIQUUS CAPITIS INFERIOR Spinous process of the axis (C2) Tip of the transverse process of the atlas (C1) Rotates atlas (therefore, the head) on the same side the dorsal rami of c1 (suboccipital nerve) OBLIQUUS CAPITIS SUPERIOR Tip of the transverse process of the atlas (C1) Occipital bone between the inferior and superior nuchal lines, superficial and superior to the insertion of Rectus capitis posterior major Unilateral Contraction: Laterally bends head to the same side Bilateral Contraction: Extends head the dorsal rami of c1 (suboccipital nerve) the dorsal ramus of c1 (suboccipital nerve) 15 Rotator (Musculotendinous) Cuff Formed by the tendons of the Supraspinatus, Infraspinatus, Teres Minor, and Subscapularis (SITS) muscles. The rotator cuff fuses with the capsule of the shoulder joint and strengthens it every where except inferiorly. The rotator cuff muscles stabilize the shoulder joint and have their prime function the holding of the head of the humerus in the glenoid cavity. A torn rotator cuff may result in dislocation of the shoulder joint. The most commonly torn part of the rotator cuff is the supraspinatus tendon. There are a number of bursae associated with the rotator cuff muscles. SUBACROMIAL BURSA: Between the Supraspinatus tendon and the acromion and the coracoacromial ligament. The subdeltoid bursa is a lateral extension of this same bursa between the Deltoid muscle and the greater tubercle of the humerus. The subacromial bursa ordinarily does not communicate with the shoulder joint. Calcium deposits in the Supraspinatus tendon are common and may be associated with inflammation, pain, tenderness, and limitation of motion, particularly abduction. This condition is called calcific tendonitis or subacromial bursitis. SUBSCAPULARIS BURSA Between the tendon of the Subscapularis and the scapular neck. This bursa is really an extension of the cavity of the shoulder joint, since it communicates with it. 16 Rotator Cuff NOTE: All except the supraspinatus are rotators of the humerus. 17 Rotator Cuff Muscle Origin Insertion Actions Innervation SUPRASPINATUS Supraspinous fossa of the scapula Superior facet of the greater tubercle of the humerus Abducts the humerus Suprascapular n. INFRASPINATUS Infraspinous fossa of the scapula Middle facet of the greater tubercle of the humerus Laterally rotates the humerus Suprascapular n. TERES MINOR Lateral border of the scapula Inferior facet of the greater tubercle of the humerus Laterally rotates the humerus Axillary n. SUBSCAPULARIS Subscapular fossa Lesser tubercle of the humerus Medially rotates the humerus Upper and lower subscapular nn. 18 19