Fingers

TERMINOLOGY

Abbreviations

• Extensor digitorum communis (EDC)
• Extensor digiti minimi (EDM)
• Interphalangeal (IP) joint
• Interphalangeal (MCP) joint

GROSS ANATOMY

Muscles

• Flexor aspect

Flexor digitorum superficialis

– Origin: Common flexor tendon origin and midradius

– Insertion: Volar plates of proximal IP joints and bases of middle phalanges digits 2-5

– Superficialis tendon is superficial to profundus tendon in palm until it divides at level of proximal 1/3 of proximal phalanx

– 2 slips of superficialis tendon pass around profundus tendon and reunite deep to profundus tendon prior to insertion

– Flexes both MCP joints, aided by lumbricals and interossei and proximal IP joints of digits 2-5

Flexor digitorum profundus (FDP)

– Origin: Proximal radius, midradius, and interosseus membrane

– Profundus tendon passes through divided superficialis tendon to insert at base of distal phalanx

– Insertion: Volar plates of distal IP joints and bases of distal phalanges digits 2-5

– Flexes distal and proximal IP joints as well as MCP joints aided by lumbricals and interossei
• Palmar interossei

Denoted 1-3 from radial to ulnar

Origin: Mesial palmar diaphyses of 2nd, 4th, and 5th metacarpals

Insertion: Mesial lateral bands and proximal phalanges have same base as digit of origin

Adducts digits and assists lumbricals with flexion MCP and extension IP joints in digits 2, 4, and 5
• Extensor aspect

EDC

– Origin: Common extensor tendon origin (lateral humeral epicondyle)

– Insertion: As central slip at bases of middle phalanges and proximal IP joint capsule

– Separate EDC tendon to 5th digit tendon is present in 50% of general population

Extensor indicis

– Origin: Posterior ulna, distal ulna, and interosseus membrane

– Insertion: Blends with 2nd digit EDC tendon and extensor hood

EDM

– Origin: Common extensor tendon origin (lateral humeral epicondyle)

– Insertion: 2 tendons of EDM fuse with one another and with 5th digit EDC tendon prior to insertion at base of proximal phalanx 5th digit
• Lumbricals

Numbered 1-4 from radial to ulnar

Origin: FDP tendons, just distal to carpal tunnel

Insertion: Radial lateral bands of digits 2-5

– Extend IP and flex MCP joints of digits 2-5
• Dorsal interossei

Numbered 1-4 from radial to ulnar

Origin: Dorsolateral metacarpal diaphyses

Insertion: Adjacent lateral bands of digits 2-4

– Extend 2nd-5th IP joints and abduct digits 2-5

Tendon Pulley System

• Annular pulley

Retinaculum that retain flexor tendons at 5 points = annular pulleys

Prevent tendon bowstringing during finger flexion

Odd -numbered pulleys at oval parts (i.e., joints)

Even -numbered pulleys at elegant waists (i.e., shafts)

A2 and A4 are functionally most important pulleys to prevent bowstringing

– A1: MCP joint and base of proximal phalanx

– A2: Middle and distal 3rds of proximal phalanx

– A3: Proximal IP joint

– A4: Midshaft of middle phalanx

– A5: Distal IP joint

Also cruciform pulleys, C1-C3
• Extensor expansion

Begins just proximal to MCP joints and terminates just proximal to proximal IP joint

Dorsal expansion of fibers oriented perpendicular to long axis of extensor tendons

Fibers of extensor expansion interdigitate with EDC tendons to prevent lateral translation

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Apr 9, 2020 | Posted by admin in MUSCULOSKELETAL IMAGING | Comments Off

TERMINOLOGY

Abbreviations

GROSS ANATOMY

Muscles

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Radiology Key

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Fingers

Fingers

Tendon Pulley System

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Radiology Key

Fastest Radiology Insight Engine

Fingers

Fingers

TERMINOLOGY

Abbreviations

GROSS ANATOMY

Muscles

Tendon Pulley System

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Full access? Get Clinical Tree