Upper Limb Bones: Scapula Anatomy

Upper Limb Bones

• The scapula, also known as the shoulder blade, is a flat, triangular bone.
• It's located on the posterior aspect of the thorax, extending from the second to the seventh rib.

Scapula - Anterior (Costal) Surface

• The scapula has anterior, lateral, and posterior surfaces.
• Subscapular Fossa: A large, concave depression for the subscapularis muscle attachment.
• Coracoid Process: A beak-like projection that provides attachment for the pectoralis minor, short head of the biceps brachii, and coracobrachialis muscles.

Scapula - Posterior Surface

• Spine of the Scapula: A prominent ridge dividing the posterior surface into the supraspinous and infraspinous fossae.
• Supraspinous Fossa: A shallow depression for the supraspinatus muscle attachment.
• Infraspinous Fossa: A larger depression for the infraspinatus muscle attachment.
• Acromion: An extension of the spine, forming the highest point of the shoulder, providing attachment for the deltoid and trapezius muscles.

Scapula - Lateral Surface

• Glenoid fossa: A shallow socket that articulates with the head of the humerus to form the glenohumeral (shoulder) joint.
• Supraglenoid tubercle: A roughening immediately superior to the glenoid fossa. Attachment site for the long head of the biceps brachii muscle.
• Infraglenoid tubercle: A roughening immediately inferior to the glenoid fossa. Attachment site for the long head of the triceps brachii muscle.

Scapula - Medial Border

• Attachment Sites: Rhomboid major, rhomboid minor, and serratus anterior muscles.

Scapula - Joints

• Glenohumeral Joint: Articulation between the glenoid cavity and the head of the humerus.
• Acromioclavicular Joint: Articulation between the acromion of the scapula and the clavicle.
• Scapulothoracic Joint: Functional joint between the anterior surface of the scapula and the posterior thoracic wall.

Scapula - Neurovascular Supply

• Arteries: Suprascapular artery, circumflex scapular artery, dorsal scapular artery.
• Nerves: Suprascapular nerve, dorsal scapular nerve, axillary nerve (to the deltoid and teres minor).

Scapula - Clinical Considerations

• Scapular Fracture: Typically occurs from high-energy trauma. May involve the body, neck, or glenoid.
• Winged Scapula: Caused by injury to the long thoracic nerve, affecting the serratus anterior muscle.

Clavicle (Collarbone)

• Location: An S-shaped long bone located horizontally across the front of the thorax, above the first rib, extending from the sternum to the scapula.
• Main functions: Attaches the upper limb to the trunk; protects underlying neurovascular structures supplying the upper limb; transmits force from the upper limb to the axial skeleton.
• Sternal (medial) End: Contains a large facet for articulation with the manubrium of the sternum at the manubriosternal joint; inferior surface has a rough oval depression for the costoclavicular ligament.
• Shaft: Acts as a point of origin and attachment for several muscles (deltoid, trapezius, subclavius, pectoralis major, sternocleidomastoid, and sternohyoid).
• Acromial (lateral) End: Houses a small facet for articulation with the acromion of the scapula at the acromioclavicular joint; attachment point for the coracoclavicular ligament (conoid and trapezoid parts).

Clavicle - Muscles Attached

• Pectoralis Major
• Deltoid
• Trapezius
• Sternocleidomastoid
• Subclavius

Clavicle - Joints

• Sternoclavicular Joint: Articulation between the clavicle and the manubrium of the sternum.
• Acromioclavicular Joint: Articulation between the clavicle and the acromion of the scapula.

Clavicle - Neurovascular Supply

• Arteries: Clavicular branch of the thoracoacromial artery, suprascapular artery.
• Nerves: Supraclavicular nerves (supply the skin over the clavicle), nerve to the subclavius.

Clavicle - Clinical Considerations

• Clavicle Fracture: Results from a fall on the shoulder or outstretched hand.
• Acromioclavicular Joint Dislocation: Often due to a direct blow to the shoulder. (Fractures occur more often in the middle third, and 80% are in the middle third)
• Management of a clavicular fracture can be conservative (e.g., sling immobilization) or operative (e.g., open reduction and internal fixation).

Humerus

• Long bone of the upper arm, extending from the shoulder to the elbow.
• Proximal Landmarks: Head, anatomical and surgical neck, greater and lesser tuberosities, and intertubercular sulcus.
  • The greater tuberosity is located laterally; it is an attachment site for supraspinatus, infraspinatus, and teres minor.
  • The lesser tuberosity faces medially; an attachment site for subscapularis.
• Shaft: Site of various muscle attachments; the radial (or spiral) groove is a shallow depression that runs diagonally down the posterior surface of the humerus, parallel to the deltoid tuberosity; the radial nerve and profunda brachii artery lie in the groove.
• Distal end: Lateral and medial supraepicondylar ridges; lateral and medial epicondyles;ulnar nerve passes posterior groove; trochlea; capitulum; coronoid, radial, and olecranon fossae.

Humerus - Muscles Attached

• Rotator Cuff Muscles (Supraspinatus, Infraspinatus, Teres Minor, Subscapularis).
• Deltoid
• Pectoralis Major
• Latissimus Dorsi
• Teres Major
• Biceps Brachii
• Triceps Brachii
• Brachialis
• Coracobrachialis

Humerus - Joints

• Glenohumeral Joint: Articulation between the head of the humerus and the glenoid cavity of the scapula.
• Elbow Joint: Articulation between the distal humerus and the radius and ulna (humeroradial and humeroulnar joints).

Humerus - Neurovascular Supply

• Arteries: Brachial artery, profunda brachii artery.
• Nerves: Axillary nerve, radial nerve, musculocutaneous nerve, ulnar nerve, median nerve.

Humerus - Clinical Considerations

• Humeral Fracture: Can occur at the proximal, shaft, or distal end; mid-shaft fractures may injure the radial nerve.
• Shoulder Dislocation: Displacement of the humeral head from the glenoid cavity (often anteriorly).
• Impingement Syndrome: Compression of the rotator cuff tendons or the subacromial bursa (often involving the supraspinatus tendon).