Anatomy of the Forearm 22-23(1).pptx

Anatomy of the Forearm Dr Catherine Hennessy [email protected] Learning Outcomes • Describe the deep and superficial flexor muscles in the anterior compartment of the forearm. • Describe the extensor muscles in the posterior compartment of the forearm. • Identify the position and course of the...

Anatomy of the Forearm Dr Catherine Hennessy [email protected] Learning Outcomes • Describe the deep and superficial flexor muscles in the anterior compartment of the forearm. • Describe the extensor muscles in the posterior compartment of the forearm. • Identify the position and course of the arteries in the forearm and hand. • Identify the position and course of the nerves in the forearm and hand. Skeletal Component Coronoid process Head Radial tuberosity Olecranon Trochlear notch Radial notch Ulnar tuberosity Interosseous membrane Styloid process of radius Styloid process of ulna Joints 1. Synovial hinge joint (elbow joint) – flexion/extension 2. Synovial pivot joint (proximal radioulnar joint) – supination/pronation Posterior Anterior Olecranon of the ulna Capitulum Trochlea of of the humerus the humerus Trochlear notch of the ulna Head of radius Radial notch of the ulna Proximal radioulnar joint Ligaments Ligaments stabilise/strengthen joint Lateral Medial Annular ligament Lateral epicondyle Medial epicondyle Radial collateral ligament Ulnar collateral ligament Forearm Compartments Two compartments: 1. Anterior/Flexor compartment 2. Posterior/Extensor compartment Long tendons enter hand Anterior Compartment Mainly flexors Superficial muscles: 3 Flexors of wrist (carpi) 1 Pronator FROM COMMON FLEXOR ORIGIN Intermediate muscles: 1 Flexor of digits 2-5 (digitorum) Deep muscles: 1 Flexor of digits 2-5 (digitorum) 1 Flexor of thumb (pollicis) 1 Pronator Superficial Muscles COMMON FLEXOR ORIGIN Medial epicondyle Pronator teres (see pronation slide) Flexor carpi radialis Palmaris longus Flexor carpi ulnaris (Pisiform + hamate) 2 3 5 Metacarpals Clinical: Golfers elbow / medial epicondylitis (inflammation of tendons at CFO due to overuse/excessive gripping) Intermediate Muscles COMMON FLEXOR ORIGIN Medial epicondyle Flexor digitorum superficialis Radial artery 5 2 3 4 Middle phalanges Deep Muscles Medial epicondyle Interosseous membrane Flexor pollicis longus Flexor digitorum profundus + Pronator quadratus (see pronation slide) 1 Distal phalanges Posterior Compartment Mainly extensors Superficial muscles: 3 Extensors of wrist (carpi) 1 Extensor of digits 2-5 (digitorum) 1 Accessory extensor to digit 5 (digiti minimi) Brachioradialis and anconeus Deep muscles: 2 1 1 1 Extensors of thumb (pollicis) Abductor of thumb (pollicis) Accessory extensor to digit 2 (indicis) Supinator Superficial Layer Supracondylar ridge COMMON EXTENSOR ORIGIN Lateral epicondyle Extensor carpi radialis longus/brevis Extensor digitorum Extensor digiti minimi (Accessory to extensor digitorum) Extensor carpi ulnaris Metacarpals 5 32 Middle phalanges Distal phalanges Clinical: Tennis elbow / lateral epicondylitis (inflammation of tendons at CEO due to overuse/forceful extension) Brachioradialis Two other superficial muscles Supracondylar ridge Lateral epicondyle Brachioradialis - Flexor when half pronated Anconeus - Stabilises elbow Styloid process of the radius Deep Layer Supinator (see supination/pronation slide) Abductor pollicis longus Extensor pollicis brevis Anatomical snuff box Extensor pollicis longus Extensor indicis (Accessory to extensor digitorum) 1st Metacarpal Proximal phalanx Distal phalanx Wrist Ab/adduction • • Flexor carpi radialis Extensor carpi radialis (longus + brevis) FCU Abduction (radial deviation): FC R Performed by the carpi muscles Adduction (ulnar deviation): Together muscles splint the wrist to allow fine movements of the hand ECR Flexor carpi ulnaris Extensor carpi ulnaris EC U • • Pronation and Supination Muscles involved in supination: Muscles involved in pronation: Humeral Biceps brachii Ulna Supinator Pronator teres Pronator quadratus Pronation and Supination Supinated Pronated Annular ligament Proximal radioulnar joint SUPINATION PRONATION Distal radioulnar joint During pronation: the radius rotates over the ulna Carpal Tunnel and Flexor Retinaculum Tunnel for flexor tendons to digits and median nerve Flexor retinaculum (transverse carpal ligament) - Prevents bowing of tendons Contents: Synovial sheaths Median nerve Flexor policis longus Flexor digitorum superficialis Flexor digitorum profundus Extensor Retinaculum Extensor retinaculum - Prevents bowing of tendons - Separates tendons into compartments Synovial sheaths Extensor digitorum Long Tendon Insertions Tendons to digits 2 – 5 Extensor digitorum - Into middle + distal phalanx Flexor digitorum profundus - Into distal phalanx Flexor digitorum superficialis - Into middle phalanx Blood and Nerve Supply to the Forearm Cubital Fossa Triangular region over anterior elbow Lateral cutaneous nerve to the forearm Brachialis 3. Brachial artery 4. Median nerve Lateral epicondyle 1. Radial nerve 2. Biceps tendon Brachioradialis (lateral boundary) Medial epicondyle Pronator teres (medial boundary) Bicipital aponeurosis Median Cubital Vein Important for venepuncture Cephalic vein Basilic vein Median cubital vein Arterial Supply Cubital fossa - Brachial artery divides into: 1. Radial artery (located under brachioradialis) 2. Ulnar artery (located under flexor carpi ulnaris) Gives off common interosseous branch Anastomosis around elbow joint Radial Artery Brachial artery Brachioradialis Anterior Recurrent branches contributing to anastomosis Radial artery Superficial branch of the radial nerve Winds to dorsum of hand Medial Ulnar Artery Anterior Ulnar artery Recurrent branches contributing to anastomosis Common interosseous artery Flexor carpi ulnaris Posterior interosseous artery Ulnar nerve Anterior interosseous artery Medial Nerve Supply Musculocutaneous nerve (lateral cutaneous nerve of the forearm) Median nerve Radial nerve Ulnar nerve Median Nerve Lies mid forearm between FDS and FDP Branch - Anterior interosseous nerve (to deep flexors) Passes through carpal tunnel Median nerve Clinical: Carpal tunnel syndrome – median nerve compression (Due to increased pressure in carpal tunnel – associated with trauma, obesity, pregnancy) Carpal tunnel Motor: Anterior compartment muscles (except FCU and medial part of FDP) and lateral hand muscles Sensory: Lateral palm, including lateral 3 ½ digits (d1, d2, d3, ½ d4) on the palmar surface Ulnar Nerve Posterior Anterior Cubital tunnel Ulnar nerve Flexor carpi ulnaris Ulnar nerve Flexor digitorum profundus Clinical: Cubital tunnel syndrome Motor: FCU and medial part FDP, and intrinsic muscles of hand (except thenar group) Sensory: Medial side of hand (palmar and dorsal surface) including medial 1 ½ digits (½ d4 + d5) Radial Nerve Enters forearm on lateral side under brachioradialis Divides into two branches: Superficial branch (sensory) Under brachioradialis Winds round to dorsum of hand Deep branch - posterior interosseous nerve (motor) Passes through supinator muscle Enters extensor compartment Radial Nerve Posterior Anterior Deep branch Radial nerve Supinator muscle Superficial branch Brachioradialis Brachioradialis Superficial branch Posterior interosseous nerve Clinical: Wrist drop Motor: Deep branch supplies posterior compartment muscles Sensory: Superficial branch supplies dorsolateral aspect of the hand including lateral 3 ½ digits Cutaneous Innervation Lateral cutaneous nerve of forearm (musculocutaneous) Radial nerve Radial nerve Medial cutaneous nerve of forearm (from medial cord) Median nerve Ulnar nerve Clinical: Altered sensation in one of the above areas indicates a distal nerve in