Shoulder Girdle (Lecture 1) PDF

Faculty of Medicine Anatomical basis of movements of the shoulder girdle Lecture 1 ILO’s By the end of this lecture the student should be able to: Locate the important features of the bones that form the shoulder girdle [scapula and clavicle] Describe the structure...

Faculty of Medicine Anatomical basis of movements of the shoulder girdle Lecture 1 ILO’s By the end of this lecture the student should be able to: Locate the important features of the bones that form the shoulder girdle [scapula and clavicle] Describe the structure of the two joints of the shoulder girdle [ Sternoclavicular and Acromioclavicular joints]. Identify the important supporting ligaments. State the movements permitted at these joints, the muscles producing these movements and their nerve supply. Describe the boundaries and contents of “axilla”. Use the acquired anatomical knowledge to explain abnormalities seen in shoulder girdle injuries. 2 Shoulder girdle Comprises the collar bone (or clavicle) and the shoulder blade (or scapula). Together, they provide a mobile base to attach the upper limbs to the trunk. Subclavian groove It acts as a bar to distance the scapula and upper limb from the chest wall Forms articulations with the sternum and with the acromion of the scapula Transmits forces to the axial skeleton Lacks marrow and ossifies in membrane Right Clavicle  The triangular scapula: Articulates with the humerus at the glenoid fossa Possesses a prominent spine on the posterior surface Provides large, flat surfaces and roughened processes for muscle attachments Right Scapula Joints of the shoulder girdle: Sternoclavicular joint. Acromioclavicular joint. 5  Shoulder girdle joints 1) Sternoclavicular joint Type: Saddle synovial joint. Articular surfaces: 1. Sternal end of the clavicle. 2. Clavicular notch of manubrium sterni and 1st costal cartilage (upper surface). The articular surfaces of the sternoclavicular joint are covered by fibrocartilage Synovial capsule encloses the joint Accessory ligaments: 1- the capsule is reinforced by anterior and posterior sternoclavicular ligaments. 2- Just lateral to the joint, the costoclavicular ligament connects the clavicle to the 1st costal cartilage and 1st rib. This ligament is very strong and is the major stabilizing factor of the sternoclavicular joint. A fibrocartilaginous disc attaches to capsule; divides the joint into two cavities. 8 2) Acromioclavicular joint: Type: Plane synovial joint. Articular surfaces: 1. Acromial end of the clavicle. 2. Clavicular facet of the acromion process of the scapula Accessory ligaments: 1. Acromioclavicular ligament: It covers the upper aspect of the joint. 2. Coracoclavicular ligament: It is extremely strong, and it is the principal factor in providing stability to the joint It has 2 parts: a. Trapezoid part b. Conoid part  Scapular movements= Movements of the shoulder girdle Elevation : Depression : Retraction : Backward movement of the scapula Protraction : Upward rotation Downward rotation Forward movement of the scapula of the scapula of the scapula 1) Muscles of the Pectoral region involved in movements of the shoulder girdle The pectoral region is located on the anterior chest wall. It contains four muscles that exert a force on the upper limb: 1. Pectoralis major 2. Pectoralis minor, 3. Serratus anterior 4. Subclavius.  Pectoralis minor Attachments: between the upper ribs and Coracoid process of the scapula Action: Protraction and depression of the scapula  Subclavius Attachments: between firs rib and its costal cartilage and clavicle Nerve supply: Nerve to subclavius Action : Stabilizes the clavicle Serratus Anterior 15 Attachments: from upper 8 or 9 ribs anteriorly to the medial border of the scapula posteriorly Nerve supply: Long thoracic nerve Action: Protraction Rotate the scapula to raise the arm above 900 Long thoracic nerve could be injured in Radical Mastectomy operations Long thoracic nerve injury Paralysis of the serratus anterior muscle results in: -Weakness in abduction of the arm above 90˚ -Arm can not be used to push with. -Winging of the scapula: Medial and inferior borders of the scapula become prominent Tested by : Make the patient push against the wall 19 2) Muscles of the Back involved in movements of the shoulder girdle Levator scapula Trapezius Rhomboidus minor Rhomboidus major Superficial Layer Deep Layer 20 Trapezius muscle Attachments: from skull and upper half of vertebral column to the Scapula and Clavicle Nerve supply: Spinal part of accessory nerve (11th Cranial nerve) Action: Acts with serratus anterior to rotate the scapula to raise the arm above 900 Upper fibers : Elevate the scapula Middle fibers: Retract the scapula Lower fibers: Depress the scapula Paralysis of trapezius muscle Weakness in raising the arm above 90˚ Weakness in retraction of the scapula Flattening in the lower neck Sagging of the shoulder Deeper layer of muscles of the BACK Rhomboideus Minor Rhomboideus Major  Levator Scapulae Rhomboideus minor Rhomboideus major Attachment: The three muscles extend between the vertebral column and the medial border of the scapula Nerve supply: Dorsal scapular nerve Action: Levator scapulae elevates the scapula Rhomboideus minor and major retract the scapula Movements of the scapula(Shoulder girdle) 1. Elevation: by: a. Upper fibers of trapezius. b- Levator scapulae. 2. Depression: by: a. Lower fibers of trapezius. b. Pectoralis minor. 3. Protraction (forward movement): by: a. Serratus anterior. b. Pectoralis minor. 4. Retraction (backward movement): by: a- Middle fibers of trapezius. b- Rhomboideus minor & major. 5. Lateral (upward) rotation, by: a. Upper & lower fibers of trapezius. b. Lower 5 digitations of serratus anterior. 6. Medial (downward) rotation, by: a. Levator scapulae. b. Rhomboids (minor and major). Clavicle: The most common mechanism of injury is a fall directly on the shoulder with the arm at the side, as seen frequently in contact sports such as rugby and football. The fracture usually occurs in the middle one-third of the clavicle. The proximal piece is lifted superiorly by the sternomastoid muscle and the distal fragment is pulled inferiorly by the arm. The treatment is usually nonoperative. 28 29 30 Acromioclavicular joint: Despite the strong ligaments keeping it in place, this joint may become separated following a fall onto the shoulder or outstretched arm. The acromion is pushed under the clavicle tearing the coracoclavicular ligament 31  It has an apex, a base and 4 walls (anterior, posterior, medial & lateral) In addition to tail of the breast. Recommended resources: Oxford handbook of medical sciences P378-291, 304 First aid for the basic sciences P 341-342 Lecture notes  1) Winging of the scapula is due to paralysis of which of the following muscles? a) Trapezius b) Levator scapulae c) Pectoralis major d) Pectoralis minor e) Serratus anterior 2) Cervicoaxillary canal is found at the……………of Axilla ? a) Apex b) Base c) Anterior wall d) Posterior wall e) Medial wall 37 38