Hand: Extrinsic Muscles PDF

Nomenclature: The Hand Phalanges/Digits Thumb D1 Metacarpals Index (Pointer)- D2 Phalanges Long (Middle) - D3 A “Ray”= metacarpal and a phalange Ring-...

Nomenclature: The Hand Phalanges/Digits Thumb D1 Metacarpals Index (Pointer)- D2 Phalanges Long (Middle) - D3 A “Ray”= metacarpal and a phalange Ring- D4 i.e.- the index ray Small – D5 Bones of the Hand: Bones of the Hand: Ray Bony Landmarks: Base is the more proximal aspect of the metacarpal Head is the more distal aspect Neck is below the head Joint Structures Carpometacarpal Joint (CMC) Articulation between proximal end of a metacarpal and distal row of carpal bones Metacarpophalangeal Joint (MCP or MP) Articulation between the distal ends of the metacarpals and the proximal phalanges Interphalangeal Joint (IP) Proximal IP Distal IP Articulation between the phalanges CMC Joints Type of Joint: Non-axial plane (irregular) synovial joint Articulation Between: Thumb: trapezium & 1st metacarpal Index: Trapezoid & base of 2nd metacarpal Long: Capitate & base of 3rd metacarpal Ring: Hamate & base of the 4th metacarpal Small: Hamate & base of the 5th metacarpal Mobility versus Stability: Thumb CMC: High Mobility, Low Stability 2nd and 3rd CMC: Low Mobility, High Stability 4th CMC: Slight Mobility, High Stability 5th CMC: Slight Mobility, High Stability The 5th CMC joint is the most mobile of the fingers and allows for a small amount of finger opposition, but not as much as the thumb. CMC Joints: Interactive Activity 1. Start with the forearm supinated and elbow flexed. 2. Form a relaxed fist. 3. Note that with a relaxed fist, the MCP joints are essentially in a straight line. 4. Now make a tight fist. 5. What do you notice about the movements at the MCP joints? 6. When you make a tight fist, the 5th MCP moves a great deal, 4th MCP moves slightly and 2nd and 3rd MCP remains stationary. 1. That movement is initiated at the CMC.  “Knuckles” Type of Joint: Biaxial Condyloid Joints Rounded heads of metacarpals articulate with base of concave phalanges Motions: Flexion & Extension Hyperextension Abduction & Adduction Volar plate on volar surface prevents hyperextension MCP Joints: Motions The middle finger is the point of reference for abduction and adduction Abduction: Occurs when the 2nd, 4th and 5th fingers move away from the 3rd finger. Also occurs when the 3rd finger moves in either direction Adduction: Occurs when the 2nd, 4th, and 5th fingers return from abduction and move toward the 3rd finger. There is no adduction of the middle (3rd) finger, only abduction occurring in either direction Interphalangeal Joint (IP) Type of Joint: Uniaxial Hinge Joints Joint Motions: Flexion & Extension Digit 1 (Thumb): 1 IP Joint Digits 2-5: 2 IP Joints PIP  Proximal DIP  Distal Joint Motion: Digits 2-5 Flexion Extension ABduction ADduction Thumb CMC Joint: Review Trapezium articulates with the base of the 1st metacarpal Type of Joint Saddle Joint Concave & Convex Surfaces Note: This joint is sometimes described as a modified ball and socket joint, which implies that it has motion in all three planes. There is rotation at the CMC joint with opposition, which is involuntary and occurs as a result of the joint’s shape. Considered: Accessary Motion Thumb CMC Joint: Motions Flexion / Extension Occur in a plane parallel to the palm (frontal plane) Palmar Abduction / Adduction Occur in a plan perpendicular to the palm (sagittal plane) Opposition / Reposition Opposition is a combination of flexion and abduction, with accessory rotation Reposition is the return to anatomical position Bones and Landmarks: Review 5 MCPs 5 Proximal Phalanges 4 Middle Phalanges 5 Distal Phalanges Proximal end of the metacarpal and phalanges is called the base Distal end of the metacarpal and phalanges is called the head Ligaments and Other Structures Flexor retinaculum: A fibrous band that spans the anterior surface of the wrist in a mediolateral (horizontal) direction Function # 1: Hold tendons close to the wrist (preventing the tendons from puling away during wrist flexion). Function # 2: Prevents the two sides of the carpal bones from separating. Split into the palmar carpal ligament & transverse carpal ligament Ligaments and Other Structures Palmar Carpal Ligament Transverse Carpal Ligament More proximal and superficial Lies deeper and more distal Distal fibers blend with the Attaches to the pisiform and transverse carpal ligament hook of the hamate on the Attaches to the styloid medial side and to the scaphoid processes of the radius and ulna and trapezium laterally and crosses over the flexor Arch over the carpal bones muscles forming a tunnel through which the median nerve and 9 extrinsic flexor tendons pass Ligaments and Other Structures Ligaments and Other Structures: Carpal Tunnel Median FDS (4) Nerve FDP (4) FPL (1) Ligaments of the Hand and Other Structures Extensor Retinaculum Fibrous band crossing on dorsal side Attaches medially to the ulnar styloid and laterally to the triquetrum, pisiform and radius Function: Holds extensor tendons close to wrist during wrist extension Divided into six sections (tunnels) called dorsal compartments Ligaments of the Hand and Other Structures: Dorsal Compartments 1st: Abductor Pollicis Longus (APL) Apple (APL) in 1st Extensor Pollicis Brevis (EPB) 2 muscles in 1st *2nd: Extensor Carpi Radialis Longus (ECRL) 2 muscles in 2nd Extensor Carpi Radialis Brevis (ECRB) 3rd: Extensor Pollicis Longus (EPL) 1 muscle in 3rd 4th: Extensor Digitorum Communis (EDC) Extensor Indicis Proprius (EIP) 2 muscles in 4th 5th: Extensor Digiti Minimi (EDM) 1 muscle in 5th 5th compartment to 5th finger *6th: Extensor Carpi Ulnaris (ECU) 1 muscle in 6th *  Ligaments of the Hand and Other Structures Extensor Expansion Ligament ”Extensor Hood” A small, triangular, flat aponeurosis covering the dorsum and sides of the proximal phalanx of the fingers * This will be discussed in- depth in a separate lecture *  Arches of the Hand Longitudinal Transverse Starts at wrist and goes to tip Distal – Metacarpal Heads Proximal – CMC Joints When the hand is relaxed, the palm assumes a cupped position. This palmar concavity is due to the arrangement of the bony skeleton reinforced by ligaments. Function: Arches of hand allow for high level of function with various grasp patterns  Creases 1 Distal palmar crease 2 Proximal palmar crease 3 Thenar crease 4 Distal wrist crease 5 Proximal wrist crease Thenar eminence Extrinsics Muscles of Thumb & Fingers Extrinsic muscles have an origin above the wrist and have an insertion inside of the hand. Cross the wrist and the joints in the hand Primary Function: Finger motion Secondary Function: Wrist motion (Weak)  Extrinsic Muscles Anterior: Flexor Digitorum Superficialis (FDS) Flexor Digitorum Profundus (FDP) Flexor Pollicis Longus (FPL) Posterior: Abductor Pollicis Longus (APL) Extensor Pollicis Brevis (EPB) Anatomical Snuff Box Extensor Pollicis Longus (EPL) Extensor Digitorum Communis (EDC) Extensor Indicis (EI) Extensor Digiti Minimi (EDM)  Flexor Digitorum Superficialis O. Medial Epicondyle of Humerus (common flexor origin), coronoid process & medial collateral ligament I. Anterior margin of the base of 2nd – 5th middle phalanx A. Flexion of PIP; Secondary MCP Flexion (2nd-5th Digits) N. Median nerve  Flexor Digitorum Profundus O. Medial olecranon, anterior and medial ulna & interossseous membrane I. Base of the 2nd - 5th distal phalanges A. Flexion of DIP, Secondary MCP and PIP Flexion (2nd – 5th Digits) N. Median N. (2nd and 3rd) & Ulnar N. (4th & 5th) Relationship of the Profundus and Superficialis Insertions Profundus Superficialis Flexor Pollicis Longus O. Radius, anterior surface and interosseous membrane I. Distal phalanx of thumb A. Flexes all joints of the thumb N. Anterior Interosseous (Median)  Abductor Pollicis Longus O. Posterior radius, interosseous membrane, middle ulna I. Base of the thumb metacarpal A. Radial abduction of thumb N. Radial nerve Note: It effectively abducts the thumb at the CMC even though it is attached only to the metacarpal because the MCP and IP only allow flexion and extension; therefore the thumb moves as one unit in the direction of abduction Extensor Pollicis Brevis O. Posterior distal radius I. Base of the proximal phalanx of thumb A. Extends MCP joint of thumb N. Radial nerve  Extensor Pollicis Longus O. Middle posterior ulna and interosseous membrane I. Base of distal phalanx of thumb A. Extension of thumb IP N. Radial nerve Anatomical Snuff Box Deep depression on dorsal base of thumb Formed by 3 tendons: Radial (Lateral) Side 1- Abductor Pollicis Longus 2- Extensor Pollicis Longus Ulnar (Medial) Side: 3- Extensor Pollicis Brevis Extend your thumb and you will notice a depression formed between the tendons What bone is found in this depression? Extensor Digitorum O. Lateral epicondyle of humerus I. Base of middle and distal phalanx of 4 fingers (extensor mechanism) A. Extension all three joints of fingers N. Radial nerve Note: The only common extensor muscle of the digits  Extensor Indicis O. Distal Ulna I. Base of distal phalanx of 2nd finger and dorsal expansion A. Extension of MCP joint of 2nd (Index) Finger N. Radial nerve Extensor Digiti Minimi O.Lateral epicondyle of humerus I. Base of proximal phalanx of small finger and dorsal expansion A. Extension MP joints of 5th finger N. Radial nerve Sensory Innervations Review Questions: 1. Which finger and thumb motions occur in the frontal plane? 2. Which finger and thumb motions occur in the sagittal plane? 3. Which finger and thumb motions occur in the transverse plane? 4. How many bones comprise one thumb? 5. How many bones comprise one finger? 6. How many joints comprise the thumb? What are the names of these joints? 7. How many joints comprise the finger? What are the names of these joints? 8. Which thumb opposition motion is considered an accessory motion? 9. Which tendons and nerve runs through the carpal tunnel? 10. What is an extrinsic muscle? 11. What is the ”anatomical snuffbox”? Which muscles act as the borders of this area?  Name – Flexor Digitorum Superficialis O. Medial epicondyle of humerus, coronoid process of ulna, and radial tuberosity medial collateral ligament I. Base of middle phalanx of digits 2-5 A. Flexion of PIP joints N. Median  Name – Flexor Digitorum Profundus O. Medial and anterior ulna, coronoid process Medial olecranon, and interosseous membrane I. Base of distal phalanxes 2-5 A. Flexion of DIP joints N. Median (2 and 3) and ulnar (4 and 5) Name – Flexor Pollicis Longus O. Interosseous membrane, anterior surface of radius I. Base of distal phalanx of thumb A. Flexion of thumb at all joints N. Median  Name Abductor Pollicis Longus O. Posterior surface of ulna, interosseous membrane, and distal posterior surface of radius I. Base of 1st metacarpal A. Radial Abduction of thumb N. Radial Name Extensor Pollicis Longus O. Posterior ulna and interosseous membrane I. Base of distal phalanx of thumb A. Extension of thumb at all joints IP joint N. Radial  Name Extensor Pollicis Brevis O. Interosseous membrane, and distal posterior radius I. Base of proximal phalanx of thub A. Extension of the MCP joint N. Radial Name Extensor Digitorum Communis O. Lateral Epicondyle of humerus I. Base of middle and distal phalanx of digits 2-5, dorsal expansion A. Extension of all joints for digits 2-5 N. Radial  Name Extensor Indicis O. Distal medial surface of ulna, interosseous membrane I. Base of distal phalanx of digit 2 and dorsal expansion A. Extension of MCP joint of 2nd digit N. Radial Name Extensor Digiti Minimi O. Lateral epicondyle of humerus I. Base of distal proximal phalanx of 5th finger and dorsal expansion A. Extension of 5th finger at all joints MP joints N. Radial