Forearm and Wrist Regions Neumann Chapter 7 REVIEW AND HIGHLIGHTS OF OSTEOLOGY & ARTHROLOGY Radius dorsal radial tubercle radial styloid process Ulna ulnar styloid process ulnar head Carpals Proximal Row - Scaphoid, Lunate, Triquetrum, Pisiform Distal Row - Trapezium, Trapezoid, Capitate, Hamate Metacarpals - 5 WRIST COMPLEX Primary function is to position hand Wrist complex not a single joint but a group of articulations making up two operationally defined: radiocarpal and midcarpal Radiocarpal Joint articulation between radius, scaphoid, lunate, triquetrum and disk (triangular fibrocartilage); ulna is not part of articulation. Although pisiform bone is anatomically part of the proximal row of carpal bones, functionally it is not part of the articulation. Biaxial condyloid joint. Joint enclosed by a single, relatively loose joint capsule; carpals connected by interosseous ligaments. Midcarpal Joint irregular joint line between proximal and distal rows of carpals. Unlike radiocarpal joint, midcarpal joint does not have its own distinct joint capsule but instead has a capsule which is continuous with each intercarpal articulation. Joint surface is very irregular due to bony configuration. Ligaments of Wrist Complex: many ligaments we will consider 4. Dorsal radiocarpal ligament o Helps to limit wrist flexion, although not too significant Palmar radiocarpal ligament o Function is to limit wrist extension and provide support to lunate bone. Radial collateral ligament o from radius to carpals o limits ulnar deviation Ulnar collateral ligament o from ulna to carpals o limits radial deviation Page 1
Osteokinematics at the wrist: Motion is defined as occurring in two planes: Sagittal plane Flexion and Extension Frontal plane Ulnar and Radial deviation Limitations of wrist movement Ligaments limit the slide of bones at end of range and thus limit motion at the wrist. Some argue that radial deviation is a bony end-feel. Arthrokinematics (roll, slide, spin, convex/concave) Radiocarpal Joint: proximal joint surface is concave; distal joint surface is convex. Rule of moving convex surfaces. Movement at the radiocarpal joint occurs primarily as result of sliding of the proximal carpal row in a direction opposite the direction of the distal movement. (i.e. carpals slide ulnarly with radial deviation; slide posteriorly with wrist flexion) To increase radiocarpal extension due to capsule/ligament tightness: perform glides Midcarpal Joint: The surfaces are reciprocally concave/convex. In general, the carpals in the distal row slide in the direction as movement of the hand. CARPAL TUNNEL Roof - transverse carpal ligament (part of flexor retinaculum); goes from pisiform and hamate to scaphoid and trapezium. Floor - palmar radiocarpal ligament, palmar intercarpal ligs, & proximal carpal row. Medial wall - pisiform and hook of hamate Lateral wall - tuberosity of scaphoid and tubercle of trapezium. Contents - tendons of flexor digitorum superficialis, profundus, & flexor pollicis longus and median nerve. (9 tendons & 1 nerve) NEUROVASCULAR Review info (Gross) about the vessels and nerves of the anterior and posterior regions of the forearm Brachial artery branches into radial and ulnar arteries in the cubital fossa Ulnar Nerve - After passing posterior to the medial epicondyle of the humerus, it enters the anterior portion of the forearm & travels with the ulnar artery to the wrist and hand. Median Nerve - Passes between the 2 heads of the pronator teres then travels deep to the flexor digitorum superficialis. Superficial & Deep branches of the Radial Nerve; the deep branch travels thru the supinator muscle Patho-Kinesiology: Fractures & dislocations such as Colles' Fracture, scaphoid fracture, lunate dislocations Nerve entrapments (forearm included in arm-elbow notes) Carpal Tunnel Syndrome Page 2
MUSCULATURE IN THE FLEXOR SIDE OF THE FOREARM SUPERFICIAL GROUP - All have a common tendon attachment that includes the medial epicondyle. Pronator teres Flexor carpi radialis Palmaris longus: Absent in about 10-20% of individuals. Absent more often on left side Flexor digitorum superficialis Flexor carpi ulnaris DEEP GROUP None of these cross the elbow. Flexor digitorum profundus, Flexor pollicis longus, Pronator quadratus WRIST FLEXORS Flexor carpi radialis Flexor carpi ulnaris Accessory muscle: Palmaris longus Aid in wrist flexion: o Flexor digitorum superficialis, Flexor digitorum profundus, Flexor pollicis longus IN THE EXTENSOR SIDE OF THE FOREARM SUPERFICIAL GROUP - All have a common tendon attachment that includes the lateral epicondyle. Brachioradialis Extensor carpi radialis longus Extensor carpi radialis brevis Extensor digitorum Extensor digiti minimi Extensor carpi ulnaris DEEP MUSCLE GROUP Supinator Abductor pollicis longus, Extensor pollicis longus, Extensor pollicis brevis, Extensor indicis WRIST EXTENSORS Extensor carpi radialis longus Extensor carpi radialis brevis Extensor carpi ulnaris Aid in wrist extension - Extensor digitorum, Extensor indicis, Extensor digiti min, Extensor pollicis longus RADIAL DEVIATORS Flexor carpi radialis Extensor carpi radialis longus & brevis Aid in wrist radial deviation - Pollicis muscles ULNAR DEVIATORS Flexor carpi ulnaris AND Extensor carpi ulnaris Page 3
Compare/Contrast Internal Torque Production @ the Wrist: All About Grip: Tenodesis Grip: Questions: 1. Only 1 muscle of the forearm, that acts on the wrist, actually attaches directly to the carpal bones. Most of them exert their action on the wrist via their distal attachment to the metacarpals and phalanges. Which muscle is the exception? 2. What role do the wrist extensor play in producing a forceful fist/grip? How does position of the wrist effect grip force production? 3. Which muscle is the strongest radial deviator? 4. Explain how the actions of the ECRL and the FCR muscles are a great example of two muscles working as synergists for the same wrist movement (like a force couple) yet can also act as antagonists in other movements of the wrist? Page 4
Movement Analysis: Page 5