hand anatomy

Hand Anatomy

Peninsula Hospital Center

Palmar Spaces

• Thenar Space• Midpalmar Space• Hypothenar Space• Radial Bursa• Ulna Bursa• Parona Space

Radial, Ulna and Perona Space

Digits

• Osteology – Fingers• proximal (P1), middle (P2), and distal (P3) phalanges

– Thumb • Proximal and distal phalanges

MCP Joint

• Triaxial condyloid joint– Range of motion: 15° of hyperextension to 90° of flexion– Metacarpal head has trapezoidal shape

• cam effect ? on the collateral ligaments• Taut MCP joint flexion• Lax in extension.

– Thumb: Metacarpal head a single broad condyle• Sesamoids volar plate.• Ulnar collateral ligament (UCL)

– Proper – Accessory portions

PIP Joint

• The PIP joint hinge joint• Head of proximal phalanx

– Two condyles – Intercondylar notch– Intercondylar notch articulates with the median ridge at the base

of the middle phalanx– Collateral ligaments Taut throughout range of motion – Proper collateral ligament

• Origin head of the proximal phalanx• Insertion lateral tubercle of the base

– Accessory collateral ligament—Inserts into the volar plate. – Volar plate—A thick, fibrocartilagenous floor that originates within the A2 pulley and

inserts into the “rough area” at the base of P2. It supports the insertion of the accessory collateral ligament and prevents PIP joint hyperextension.

PIP Joint

• Accessory collateral ligament– Inserts into the volar plate– Volar plate• Origin: A2 pulley • Insertion: Base of P2• Function: Supports the insertion of the accessory

collateral ligament and prevents PIP joint hyperextension.

DIP Joint

• Distal interphalangeal joint is stabilized by– Collateral ligaments– Terminal extensor tendon insertion– FDP insertion– Volar plate

Dorsal Surface of Finger

• Extensor apparatus • Extensor tendons divided into anatomic zones• Trifurcates at P1 base• Central portion insertion P2 as the central slip. • Lateral slips converge middle phalanx insertion P3

Dorsal Surface

• Dorsal stabilizing structures – Sagittal bands: origin at MCP joint volar plate and the base of P1

• Function: Stabilize extrinsic extensor tendon at the dorsal MCP joint• Indirectly MCP joint extension

– Triangular ligament• Function: Stabilize conjoined lateral bands over the base of P2 and prevent

volar subluxation.

– Transverse retinacular ligament• Function: Stabilize conjoined lateral bands to prevent dorsal subluxation

– The oblique retinacular ligament (ORL) links the PIP and DIP joints. • Origin: Fibro-osseous gutter at the A2 pulley and middle third of P1 (volar)

to insert into the terminal extensor tendon (dorsal).

Volar Finger

• Fascia– Grayson and Cleland ligaments– The flexor tendons five anatomic zones – FDS flattens and bifurcates at A1– FDS further divides into medial and lateral slips

Vascular Supply

• Vascular supply: Direct vascular supply and synovial diffusion

• Direct Vascular Supply: Transverse digital arteries and a direct arterial supply from intraosseous vessels at tendinous insertions• Synovial diffusion: Rely on intratendinous canaliculi for

synovial diffusion

Zones of Flexor Tendons

Flexor Tendon Pulleys

• The A1, A3, and A5 pulleys take their origin from palmar plates of the MCP, PIP, and DIP joints, respectively

• A2 and A4 pulleys originate from the proximal and middle phalanges

• A2 and A4 pulleys are the most important pulleys biomechanically

Dorsal Thumb

• MCP joint– EPL tendon is ulnar to EPB– EPL, EPB stabilized by sagittal band

• Volar Thumb • FPL emerges from interval between adductor pollicis

and the thenar• Flexes interphalangeal (IP) joint.

Volar Thumb

– Flexor tendon sheath/pulleys • A1, oblique and A2 pulleys comprise the pulley system

of the thumb. • A1 pulley at MCP joint• Oblique pulley fibers distal and radial direction at

proximal phalanx• A2 pulley: origin IP joint volar plate• A1 and oblique pulleys most important biomechanically• Radial digital nerve risk during A1 pulley release.

Hand Osteology

• CMC Joint– biconcave-convex

• TM joint– Biconcave-convex (two opposing saddles) – Stability by dorsal ligamentous complex• Dorsooradial ligament • Posterior oblique ligament• Deep anterior oblique ligament

Dorsal Hand and Extensor Tendons

• Juncturae tendinae • Extensor indicis proprius (EIP) and extensor digiti

minimi (EDM) are most commonly ulnar EDC tendons • Most common extensor pattern to little finger two

EDM tendons and no EDC tendon. • Extensor digitorum brevis confused with a soft-tissue

tumor.

Intrinsic Muscles

• Interossei (dorsal and volar)• Lumbrical• Thenar• Hypothenar muscles.

Interossei Muscles

• Origin: metacarpal diaphyses• Dorsal to the deep transverse intermetacarpal

ligament• Innervation: ulnar nerve• First interosseous muscle sometimes

innervated by median nerve

Interossei Muscles

• Four dorsal interossei: bipennate, superficial and deep muscle belly– Superficial Insertion lateral tubercle abduction of

digit– Deep lateral tendon Insertion Extensor Apparatus Flex MCP Joint

• Volar interossei : Unipennate – Origin: Metacarpal Shaft; Insertion: Extensor apparatus– Function: Flex MCP joint and adduct index, ring, and

little fingers

Lumbricals

– Origin: FDP tendon– Insertion: Radial lateral band of the extensor

apparatus– Action: extend the PIP and DIP joints through the

oblique fibers– Innervation: Median Nerve (1st and 2nd) and

unipennate• Ulna nerve (3rd and 4th) and bipennate.

Thenar Muscles

Muscle Innervation

APB Median Nerve

FPB Sup Median; Deep Ulna

Opponens Pollicis Median Nerve

Adductor Pollicis Ulna Nerve

Hypothenar MusclesHypothenar Muscles Innervation

Abductor Digiti Minimi Ulna Nerve

Flexor Digiti Minimi Ulna Nerve

Opponens Digiti Minimi Ulna Nerve

Hand 3

Hand 4

Hand 5

Hand 6

Hand 7

Finger 1

Finger 2

Hand 8

Hand 9

Paronychia

Felon

Webspace

Hand Spaces