Bones and Joints of the Wrist WRIST COMPLEX Bones and Joints of the Wrist

Proximal Row of Carpal Bones Review- testable Scaphoid: Most lateral. Forms floor of anatomical snuff box. Most commonly fractured wrist bone. Fractures may compromise radial artery in snuff box. Articulates with radius.

Proximal Row of Carpal Bones Lunate: Articulates with radius Triquetral: Articulates with ulna (via articular (ulnar) disc) during extreme ulnar deviation. Pisiform: Sesamoid bone Forms in tendon of the flexor carpi ulnaris

Distal Row of Carpal Bones: Trapezium: Most lateral Trapezoid Capitate Hamate

Distal Row of Carpal Bones: Entire complex enclosed in a common synovial membrane. Articulations are plane joints that perform gliding motions.

Radiocarpal Joint Condyloid (ellipsoidal) synovial joint. Two degrees of freedom. Articular surfaces: Scaphoid (convex) Lunate (convex) Distal radius: Two concave fossae (lateral and medial) Triquetral (convex) Only during extreme ulnar deviation

Radiocarpal Joint Ligaments Lateral (radial) collateral ligament. Medial (ulnar) collateral ligament. Dorsal radiocarpal ligament. Palmar radiocarpal ligament. Strengthen capsule

Radiocarpal Joint Functions Some flexion and extension Ulnar deviation

Radiocarpal Joint Arteries Articular arteries Arise from dorsal and palmar carpal arches.

Radiocarpal Joint Nerves Anterior interosseous branch of median nerve. Posterior interosseous branch of radial nerve. Dorsal and deep branches of the ulnar nerve.

Radiocarpal Joint Injuries Colle’s fracture Scaphoid fracture Usually at “waist” Compromises radial artery in snuffbox

Midcarpal Joint Made up of intercarpal joints: Movements: Between proximal and distal rows of carpals and between carpals. Movements: Some flexion and extension. Radial deviation (abduction). Especially due to movement of head of capitate in its socket. Enclosed within synovial capsule.

Midcarpal Joint Ligaments: Nerves and arteries: Dorsal ligaments. Palmar ligaments. Interosseous ligaments. Nerves and arteries: Same as for radiocarpal.

Palmar Structure Sequence (radial to ulnar) Radius Radial artery Flexor carpi radialis tendon Median nerve: Under palmaris longus tendon

Palmar Structure Sequence (radial to ulnar) Flexor digitorum superficialis tendons Ulnar artery Ulnar nerve Flexor carpi ulnaris tendon

HAND

Carpometacarpal Joints Plane synovial joints: Motion: None for digits 2-3 Limited for 4 More mobile for 5

Carpometacarpal Joints Saddle (sellaris) joint between metacarpus and trapezium: Movements: Abduction/adduction Flexion/extension Circumduction Opposition

Metacarpophalangeal Joints Condyloid synovial joints Movements: Flexion/extension Abduction/adduction Some opposition at MCP 5 Capsular ligaments: Palmar ligaments (pads) Collaterals

Interphalangeal Joints Synovial hinge joints Only flexion/extension allowed Ligaments: Strong collaterals Proximal interphalangeal joints (PIPs) Distal interphalangeal joints (DIPs)

Dorsal Venous Drainage Dorsal venous arch drains hand dorsum. Medially drains into basilic. Laterally drains into cephalic.

Lymphatic Drainage Medial via lymph vessels accompanying basilic vein to: Supratrochlear nodes to: Lateral axillary nodes. Lateral via lymph vessels accompanying cephalic vein to: Infraclavicular nodes to:

Arterial Supply to Dorsum Via dorsal arterial arch from: Radial and ulnar arteries. Dorsal metacarpals. Dorsal digitals.

Muscles of Dorsum of Hand Long extensor tendons. Dorsal interosseous muscles (4): Attachments: DAB: Abductors Middle finger is reference Middle finger has two First and fifth digits have none.

Long Extensors

Superficial Palm Palmar aponeurosis Flexor retinaculum Palmaris brevis

Palmar Aponeurosis Triangular layer of deep fascia located between two eminences. Provides protection for superficial vessels, nerves, and tendons. Anchored to skin and flexor retinaculum. Splits into four slips that blend with fibrous flexor sheaths of four medial digits (II – V).

Flexor Retinaculum = Transverse carpal ligament. Laterally attaches to tubercles of scaphoid and trapezium. Medially attaches to hook of hamate and pisiform.

Palmaris Brevis Muscle O: Flexor retinaculum and palmar aponeurosis. I: Skin on medial side of palm. A: Tenses skin on palm.

Carpal Tunnel Contents Long flexor tendons of: Flexor digitorum superficialis Flexor digitorum profundus Flexor pollicis longus Median nerve Note: ulnar nerve and artery pass through Guyon’s canal.

Long Flexors

Intrinsic Muscles of the Thumb Thenar eminence: Adductor pollicis: Innervation: Deep branch of ulnar nerve (C8, T1).

Thenar Eminence Muscles Abductor pollicis brevis Flexor pollicis brevis Opponens pollicis Innervation: Recurrent branch of median nerve (C8, T1).

Thenar Muscles

Hypothenar Eminence Intrinsic muscles for digit V. Abductor digiti minimi Flexor digiti minimi brevis Opponens digiti minimi Innervation: Ulnar nerve

Hypothenar Muscles

Long Digital Flexors Flexor digitorum superficialis Flexor digitorum profundus

Flexor Digitorum Superficialis Flexes PIP (and MCP and wrist). Each tendon passes through fibrous flexor sheath. Each tendon bifurcates opposite proximal phalanx. Each tendon inserts on middle phalanx.

Flexor Digitorum Profundus Flexes DIP (and PIP and MCP). More active than superficialis. Each tendon inserts on distal phalanx.

Vinculae Small vascular bundles connecting palmar surface of phalanges with long flexor tendons. Long and short

Long Flexors

Dorsal Interossei Four bipennate muscles. Each arises via two heads from adjacent sides of two metacapals.

Dorsal Interossei Insertion: Abducts MP joints of digits 2-4: Onto extensor expansions and: Radial sides of proximal phalanges 2 and 3; Ulnar sides of proximal phalanges 3 and 4. Note: digit has two dorsal interossei. Abducts MP joints of digits 2-4: Reference is line through middle finger.

Interossei Muscles

Palmar Interossei Four unipennate muscles: First is sometimes considered part of flexor pollicis brevis. Supply each digit except third: Reference is middle finger. Innervation for all interossei (incl. dorsal): Ulnar nerve

Interossei Muscles

Lumbricals Four small, narrow, elongated muscles. Each arises from the radial side of a flexor digitorum profundus tendon. Innervation: Two on radial side: Median nerve Two on ulnar side: Ulnar nerve Flex MCP joints and extend IP joints.

Arterial Supply to Hand Superficial palmar arch: Continuation of ulnar artery. Deep palmar arch: Continuation of radial artery.

Route of Radial Artery Smallest terminal branch of brachial artery. Passes proximally deep to brachioradialis muscle. Distally the artery lies against the radius lateral to the tendon of the flexor carpi radialis, where it can be felt (radial pulse). Passes across scaphoid in anatomical snuff box.

Route of Radial Artery Wraps around the dorsum of first metacarpus: Gives off arteries to the thumb and index finger. Pierces the first dorsal interosseous muscle and reappears in the palm of the hand. Gives rise to the deep palmar arch.

Deep Palmar Arch

Boundaries of the Anatomical Snuff Box Lateral (anterior): Tendons of the: Abductor pollicis longus. Extensor pollicis brevis. Medial (posterior): Tendon of the: Extensor pollicis longus.

Ulnar Nerve in the Hand Enters hand superficial to flexor retinaculum. Superficial branch: Muscular branch to palmaris brevis Cutaneous to palmar aspect of ulnar side of little finger and adjacent sides of little and ring fingers, including tips and dorsum.

Ulnar Nerve in the Hand Deep branch: Supplies hypothenar muscles, all interossei, two ulnar side lumbricals, and adductor pollicis.

Nerve Supply to Hand

Median Nerve in the Hand Enters palm deep to flexor retinaculum. Divides into lateral and medial branches: Lateral branch: To thenar muscles and first lumbrical. Cutaneous to anterior surface of thumb and radial side of index finger. Medial branch: To second lumbrical. Cutaneous to adjacent sides of digits 2-4, including nail-bed and finger tips.

Spaces in the Hand Thenar space: Midpalmar space: Located between the palmar side of the adductor pollicis muscle and the long flexor tendons to the index finger and the thumb. Midpalmar space: Located between metacarpals 4-5 and the long flexor tendons to digits 4-5.

Clinical Notes Mallet finger: Dupuytren’s contracture: Avulsion by long flexor tendon. Results in hyperflexion of DIP. Dupuytren’s contracture: Progressive fibrosis of palmar aponeurosis. Results in marked flexion of fingers at MP joints. Colle’s fracture. Fracture of scaphoid.

Clinical Notes Median nerve injury: Ulnar nerve injury: Loss of thumb opposition. Atrophy of thenar muscles. Ape hand. Ulnar nerve injury: Paralysis and atrophy of interossei. Guttering Loss of thumb adduction. Clawhand.

EXTENSOR MECHANISM

Components Hood Lateral bands: Central band: Function: To bases of distal phalanges. Central band: To base of middle phalanx. Function: Flexion at MCP joint. Extension at PIP, DIP joints.

Functional Notes Extension of the PIP is always accompanied by the simultaneous extension of the DIP. When the PIP is flexed, the DIP may be extended or flexed

Clinical Notes If lateral bands detach: Lateral bands will flex the PIP and hyperextend the DIP.