Forearm Muscles & Nerves (PDF)

By: Dr. Ayman Ahmed Khanfour Professor of Anatomy & Embryology Master degree in Obstetrics & Gynecology - MRCOG Faculty of Medicine - Alexandria University  What are the compartments of the forearm ?  The forearm is subdivided into anterior & posterior compartments by th...

By: Dr. Ayman Ahmed Khanfour Professor of Anatomy & Embryology Master degree in Obstetrics & Gynecology - MRCOG Faculty of Medicine - Alexandria University  What are the compartments of the forearm ?  The forearm is subdivided into anterior & posterior compartments by the radius, ulna, interosseous membrane and deep fascia.  Why the anterior compartment is much more bulky than the posterior compartment of the forearm? (Compartments of the forearm)  What is the classification of the muscles of the anterior compartment of the forearm? I. Superficial group of muscles II. Deep group of muscles  What are the superficial muscles of the anterior compartment of the forearm ? 1. Pronator teres 2. Flexor carpi radialis 3. Flexor carpi ulnaris 4. Flexor digitorum superficialis 5. Palmaris longus  Common flexor origin:  It is the front of the medial epicondyle, which gives origin to the greater parts of the superficial group of muscles of the front of the forearm. 1. Pronator teres  Origin: a. Superficial humeral head - Common flexor origin. b. Deep ulnar head - Medial border of the coronoid process of the ulna.  Insertion: - Middle of the lateral surface of the shaft of the radius.  Attachments & Actions: 1. Flexion of the elbow. 2. Pronation of the radio-ulnar joint (medial rotation of forearm).  (Flexion) (Pronation) (Elbow joint) (Radioulnar joints) (Action of pronator teres & Animation)  Relations: 1. Median nerve passes between the two heads of pronator teres 2. Deep head of pronator teres separates median n. from ulnar a.  Pronation and supination (Pronation and supination) (Pronation and supination – Animation “GIF”) 2,3. Flexor carpi radialis & Flexor carpi ulnaris  Attachments: Origin: Insertion:  Attachments & Actions: FCR FCU - Flexion + abduction of the wrist. - Flexion + adduction of the wrist. (Flexion) (Abduction) (Flexion) (Adduction) (FCR - Wrist joint) (FCU - Wrist joint) (Actions of FCR & FCU & Animation “GIF”)  Relations: FCR FCU - Its tendon is related to: - The ulnar nerve enters the a. Medially: Median nerve. forearm by passing between b. Laterally: Radial artery. its two heads.  The tendon  The tendon of FCU is a of FCR is a flattened cord like tendon. tendon. (Lower forearm and hand – Anterior view)  4. Palmaris longus  Attachments & Actions: - Flexion of the wrist (week). - Tension of the palmar aponeurosis  This muscle has a short belly and long tendinous part.  The tendon of palmaris longus must be differentiated from the median nerve intraoperative..  This muscle may be present and may be absent. (Action) (Detection) (Wrist and Metacarpophalangeal joint) (Palmaris longus action & Detection - Animation) (Tendon of palmaris longus muscle) 5. Flexor Digitorum Superficicalis  Attachments & Actions: - Flexion of: a. Proximal inter-phalangeal joints (medial 4 fingers). b. Metacarpo-phalangeal joints (medial 4 fingers). - Flexion of the wrist joint. (Flexion) (Flexion) (Flexion) (Flexion) (PIPJ) (MPJ) (Wrist joint) (Complete action) (Actions of FDS & Animation) (Superficial muscles of the front of forearm)  Nerve Supply of the Anterior Compartment  Superficial muscles: Muscle Nerve Supply 1. Pronator teres 2. Flexor carpi radialis 3. Flexor digitorum - Median nerve. superficialis 4. Palmaris longus 5. Flexor carpi ulnaris - Ulnar nerve.  What are the deep muscles of the anterior compartment of the forearm ? 1. Pronator quadratus 2. Flexor digitorum Profundus 3. Flexor pollicis longus  1. Pronator quadratus  Origin and insertion:  Attachments & Actions: - Pronation. - Fixation of the lower ends of the radius and ulna.  2. Flexor digitorum profundus 3. Flexor pollicis longus  Origin:  Insertion:  The tendon of FPL is a unipennate tendon.  Actions: FPL FDL  Flexion of:  Flexion of: - Distal interphalangeal joints (med. 4 fingers). - Distal interphalangeal joints (thumb). - Metacarpophalangeal joints - Metacarpophalangeal joints (thumb). (med. 4 fingers). - Wrist - Wrist.  How the tendon of FDP reaches the distal phalanx? 1. Tendon of FDS lies in the superficial group. 2. Tendon of FDP lies in the deep group.  Relation Between the Tendon of FDS & FDP  Each tendon of flexor digitorum superficialis splits to form a “perforation” opposite the proximal phalanx.  These perforations give passage for each tendon of flexor digitorum profundus. (Deep muscles of the front of forearm)  Nerve Supply of the Anterior Compartment  Deep muscles: Muscle Nerve Supply 1. Pronator quadratus - Anterior interosseous nerve. (deep branch of median n.) 2. Flexor pollicis longus 3. Flexor digitorum - Anterior interosseous nerve profundus (lateral half). - Ulnar nerve (medial half).  What are the nerves of the anterior compartment of the forearm? 1. Median nerve (and anterior interosseous nerve) 2. Ulnar nerve 3. Radial nerve  Median, Ulnar and Radial Nerve  Course: 1.  The MEDIAN nerve descends under cover of flexor digitorum superficialis and enters the hand deep to FLEXOR retinaculum. 2. The ULNAR nerve descends under cover of flexor carpi ulnaris and enters the hand superficial to FLEXOR retinaculum. 3. The RADIAL nerve descends under cover of brachioradialis and deviates backwards superficial to EXTENSOR retinaculum.  Branches of the median and ulnar nerves: Median Nerve Ulnar Nerve Cutaneous - Palmar cutaneous branch 1. Palmar cutaneous branch. 2. Dorsal cutaneous branch. Motor 1. Pronator teres 1. Flexor carpi ulnaris. 2. Flexor carpi radialis 2. Flexor digitorum profundus 3. Palmaris longus. (medial½). 4. Flexor digitorum superficialis - Anterior interosseous n. Articular - Superior radioulnar joint. - Elbow joint. - No branches of the radial nerve in the forearm.  Anterior Interosseous Nerve  It is a branch from the upper part of the median nerve.  It descends over the interosseous membrane, accompanied by the anterior interosseous artery.  Branches: - It supplies: 1. Flexor pollicis longus. 2. Flexor digitorum profundus (lateral ½) 3. Pronator quadratus. For Contact: Dr. Ayman Ahmed Khanfour [email protected] Dr. Ayman Khanfour Dr-Ayman Ahmed Khanfour Dr. Ayman Anatomy Discussion