Bio Mechanics Of The Wrist And Hand

Wrist and Hand

Wrist Joint

Wrist Joint • Bones – Radius, Ulna – Carpal bones • Pisiform, Triquetrum, Lunate, Scaphiod, Hamate, Capitate, Trapezium, Trapeziod

Articulations • • • •

Distal RadioUlnar Joint Radiocarpal Joint MidCarpal Joint Intercarpal Joint

Distal Radioulnar Joint • Does not participate in wrist movements • Ulna has no contact with carpals • Seperated by fibrocartilagenous disk which allows ulna to glide during pronation and supination

Radiocarpal Joint • Movement of whole hand takes place here • Articulation of: – Distal Radius – Scaphoid and lunate

• Condyloid-type • Allows for flexion/extension • 40% of flexion occurs at radiocarpal joint • 60% of extension occurs at radiocarpal joint

Radiocarpal Joint

Midcarpal Joint • These joints allow for translation of joint with wrist movements • Contributes to wrist flexion/extension – 60% of flexion occurs here • 40% occurs at radiocarpal joint

– 30% of extension occurs here • 60% of extension occurs at radiocarpal joint

Midcarpal Joint • Radial and Ulnar deviation – Proximal and distal carpal rows slide across each other – Radial deviation • Proximal towards ulna, distal to radius – Ulnar deviation • Proximal towards radius, distal to ulna

Intercarpal joints • Between carpal bones of proximal row • Midcarpal joint is between two rows of carpal bones (site of hand flexion and abduction) • Carpals united by anterior, posterior, and interosseous ligaments

Intercarpal Joints

Palmar

Dorsal

Wrist Joint Ligaments • Ulnar Collateral Ligament • Radial Collateral Ligament • Volar Radiocarpal • Dorsal Radiocarpal

Ligaments of Wrist

Palmar

Dorsal

Flexor Retinaculum

Extensor Retinaculum

Vascular Anatomy • Forearm Arteries

Nerve Innervation (palmar)

Nerve Innervation (dorsal)

Movements of Wrist • Flexion, extension, abduction (radial deviation), adduction (ulnar deviation) – Motion occurs mostly in proximal carpal row & distal radius – 70°-90° of flexion – 70°-85° of extension – 15°-25° of abduction (radial deviation) – 25°-40° of adduction (ulnar deviation)

Movement of the wrist • Flexion – flexor carpi radialis – flexor carpi ulnaris – palmaris longus – assisted by: • flexor digitorum superficialis • flexor digitorum profundus

Superficial Muscles of Forearm

common flexor group

Movement of the wrist • Extension – extensor carpi radialis longus – extensor carpi radialis brevis – extensor carpi ulnaris – assisted by: • other wrist extensor muscles

common extensor group

common extensor group

Hand and Fingers

Wrist & Hand Palmar Aspect Phalanges Metacarpals Carpals

Carpometacarpal Joint • Last four have very little movement-mostly gliding joint which moves with carpals • More movement at 4th and 5th articulation – Up to 10-30 degrees of flexion/extension in these fingers

Carpometacarpal Joint • Thumb articulation – Saddle joint provides major portion of thumb ROM – 30-90 degrees of flexion – 15 degrees of extension – Sits at an angle of approx 60 deg.

Carpometacarpal Joints

Palmar

Dorsal

Metacarpophalangeal Joint • Last 4 allows for flexion/extension – Abduction/adduction

• Ligamentous support is excellent • Can flex from 70-90 deg, with most at 5th joint • Can extend about 25 deg from relaxed position • About 20 deg of ab/adduction

Metacarpalphalangeal Joints

Volar plate

Deep Transverse Metacarpal

Collateral

Interphalangeal Joint • • • •

Hinge Joints Allow for flexion/extension Most dislocations occur at these joints Collateral Ligaments provide good stability • ROM – Proximal joint--110 degrees – Distal joint--90 degrees

Interphalangeal Joints (PIP)

Collateral

Volar Plate

Interphalangeal Joints (DIP)

Collateral

Volar Plate

• Fingers

Joints & Movements

– Metacarpophalangeal Joint (MCP) • Condyloid • 0°-40° of extension • 85°-100° of flexion – Proximal interphalangeal Joint (PIP) • Ginglymus • Full extension to 90°120° of flexion – Distal interphalangeal Joint (DIP) • Ginglymus • Flex 80°-90° from full extension

• 2 joints

Thumb Joints

– Metacarpophalangeal (MCP) • Ginglymus • Full extension into 40°-90° of flexion – Interphalangeal (IP) • Ginglymus • Flex 80°-90°

• Carpometacarpal (CMC) joint • Saddle joint • 50°-70° of abduction • Flex 15°-45° & extend 0°-20°

Finger Movement • Middle phalange is reference point to differentiate abduction & adduction – Thumb, index & middle fingers abduct when they move laterally toward radial side of hand – Ring & little fingers abduction when they move medially toward ulnar side of hand – Medial movement of thumb, index & middle fingers toward ulnar side of hand is adduction – Lateral movement of ring & little finger toward radial side of hand is adduction

Intrinsic Muscles of the Hand •

Thenar muscles

•

Hypothenar muscles

•

Midpalmar muscles – Interossei – Lumbrical

Palmar Interossei

Dorsal Interossei

Thenar muscles • Adductor pollicis • Flexor pollicis brevis • Abductor pollicis brevis • Opponen pollicis

Hypothenar muscles • Flexor digiti minimi • Abductor digiti minimi • Opponen digiti minimi

Anatomical Snuffbox • Extensor pollicis longus (medial side) • Extensor pollicis brevis (lateral side) Lateral

Medial

• Abductor pollicis longus (lateral side)

3 Types of Grips • Cylindrical--Holding a bat or golf club – Ulnar deviation enhances force of grip

• Spherical--More spread of fingers – Holding a basketball

• Hook--Precision handling – Holding a coffee cup or scalpel