Upper limb

Introduction to the Upper Limb and Pectoral Region

  • Focus on the osteology of the pectoral girdle and free limb bones

Overview of the Upper Limb

  • The upper limb comprises the following segments:

    • Shoulder (junction of trunk and arm)

    • Arm

    • Elbow

    • Forearm

    • Wrist

    • Hand

Attachment to the Axial Skeleton

  • The upper limb is attached to the axial skeleton via:

    • Scapula

    • Clavicle

  • Two major joints involved are:

    • Acromioclavicular joint

    • Sternoclavicular joint

  • The primary attachment mechanism is muscular rather than ligamentous.

The Clavicle

  • Characteristics of the Clavicle:

    • First bone to ossify in the fetus (6 weeks)

    • Develops in the membrane (not cartilage)

    • Located subcutaneously along its entire length

    • Transmits mechanical forces from the arm to the axial skeleton

  • Anatomical Features:

    • Medial two-thirds:

    • Circular in cross-section

    • Curved convex forwards

    • Lateral third:

    • Flat

    • Curved convex backwards

  • Articulations:

    • Medially with the sternum and 1st costal cartilage at the sternoclavicular joint

    • Attached by:

    • Costoclavicular ligaments (to the 1st rib)

    • Sternoclavicular ligaments (to sternum)

Muscles Associated with the Clavicle

  • Deltoid Muscle (Clavicular Portion)

  • Pectoralis Major Muscle (Clavicular Portion)

  • Trapezius Muscle

  • Sternohyoid Muscle

  • Subclavius Muscle

Ligaments of the Shoulder

  • Types of Ligaments:

    • Coracoclavicular Ligament:

    • Composed of conoid and trapezoid ligaments

    • Anchors clavicle to scapula

    • Acromioclavicular Ligament

    • Coracoacromial Ligament

    • Coracohumeral Ligament

    • Glenohumeral Ligaments

    • Articular Capsule

The Scapula

  • Shape and Structure:

    • Triangular shape

    • Provides attachment for numerous muscles

  • Key Anatomical Features:

    • Glenoid Fossa:

    • Articulates with the humeral head at the glenohumeral joint

    • Acromion Process:

    • Articulates with the clavicle at the acromioclavicular joint

    • Medial and lateral borders with distinct features (e.g., coracoid process, various fossa)

Muscles of the Scapula and Associated Structures

  • Muscles Attaching to the Scapula:

    • Coracobrachialis

    • Biceps Brachii (Caput Breve)

    • Serratus Anterior

  • Muscle Actions and Attachments:

    • Pectoralis Major:

    • Origin: Clavicle, sternum, upper six costal cartilages

    • Insertion: Lateral lip of bicipital groove of humerus

    • Action: Adducts and medial rotation of arm

    • Pectoralis Minor:

    • Origin: 3rd to 5th ribs

    • Insertion: Coracoid process of scapula

    • Action: Depresses shoulder and elevates ribs if scapula is fixed

    • Deltoid:

    • Origin: Lateral third of clavicle, acromion, spine of scapula

    • Action: Arm abduction

    • Trapezius and Latissimus Dorsi with various origins and insertions.

The Humerus

  • General Structure:

    • Rounded head articulates with glenoid fossa, allowing wide movement

    • Anatomical neck separates head from greater and lesser tubercles

    • Surgical neck lies below the anatomical neck; is at risk during shoulder dislocations

  • Anatomical Landmarks:

    • Greater and Lesser Tubercles: Attachment points for rotator cuff muscles

    • Intertubercular Sulcus: Pathway for long head of biceps tendon

The Elbow Joint

  • Type and Articulation:

    • Synovial hinge joint

    • Humeral capitulum with radial head

    • Humeral trochlea with trochlear notch of ulna

  • Movements:

    • Flexion and extension around the elbow joint

  • Angle:

    • Carrying angle results from the medial border of the trochlea projecting further than the lateral border

The Radius and Ulna

  • Components:

    • Radius: Head, neck, shaft, expanded distal end.

    • Ulna: Olecranon, trochlear fossa, coronoid process, shaft, small distal head

  • Movements in Supination/Pronation:

    • Radius rotates around ulna at the radial notch

  • Colles Fracture:

    • Common in elderly when falling on an outstretched hand, causing posterior displacement of distal fragment

The Wrist Joint

  • Overview:

    • Condyloid synovial joint consisting of:

    • Distal radius

    • Triangular disc of fibrocartilage covering distal ulna

    • Scaphoid, lunate with triquetral bone in adduction

  • Movements:

    • Flexion/extension combined with midcarpal joint action

    • Total flexion is approximately 80° with majority occurring at the midcarpal joint.

Summary of the Muscles of the Forearm

  • Anterior (Flexor) Compartment:

    • Flexor muscles: Coracobrachialis, biceps, brachial artery, median nerve

    • Superficial, intermediate, and deep layer distinctions

  • Posterior (Extensor) Compartment:

    • Extensor muscles led by triceps and innervated primarily by radial nerve

Ligaments and Capsule of the Elbow Joint

  • Lateral Collateral Ligament:

    • Connects the lateral epicondyle to the annular ligament

  • Medial Collateral Ligament:

    • Triangular with three bands (anterior, posterior, middle) extending from the medial epicondyle

Carpal Tunnel

  • Formed by carpal bones and flexor retinaculum

  • Houses several tendons and the median nerve

  • Impingements lead to carpal tunnel syndrome necessitating clinical consideration