Finger Anatomy

Description

Bones of the hand and wrist

Illustration of finger flexion

Illustration of finger extension

Normal fingertip anatomy

Palmar digit anatomy

Alternative Names

• Anatomy of the Fingers
• Finger Structure
• Finger Anatomy and Function
• Finger Musculoskeletal Anatomy
• Digital Anatomy (Hand)
• Manual Digit Anatomy
• Anatomy of the Digits (Hand)
• Phalangeal Anatomy
• Hand Digit Anatomy
• Finger Bone Anatomy
• Finger Joint Anatomy
• Finger Tendon Anatomy
• Finger Neurovascular Anatomy

Nomenclature of the Fingers

• 1st Digit: Thumb is discussed separately
• 2nd Digit: pointer finger
• 3rd Digit: middle finger
• 4th Digit: ring finger
• 5th Digit: pinky, little finger

General

• Finger function is complex and involves interaction of multiple joints, flexor/extensor tendons, fascia and ligaments
• Digits of the hand (2–5) composed of proximal, middle, distal phalanges (thumb has 2)
• Articulations include MCP, PIP, DIP joints which allow flexion/extension and fine motion
• Stabilized by collateral ligaments, volar plate, joint capsule
• Motion driven by extrinsic tendons (FDP, FDS, extensors) and intrinsic muscles (lumbricals, interossei)
• Neurovascular supply from digital nerves and arteries → sensation and perfusion
• Functions include grip strength, pinch, dexterity, and fine motor control

Bones

• Proximal Phalanx
• Middle Phalanx
• Distal Phalanx

Joints

• Metacarpophalangeal Joint
  • Primarily hinge joint with 0-90 degrees flexion
  • Extension 0-30 degrees, 0-20 degrees abduction, rotation is minimal
  • Stabilized by articulate capsule, collateral ligaments, palmar ligaments
• Proximal Interphalangeal Joint of the Hand
  • Hinge joint, range of motion 0-120 degrees flexion
  • Stabilized by volar plate, capsule, collateral ligaments
  • Central slip attaches to middle phalanx, enables extension
• Distal Interphalangeal Joint of the Hand
  • Hinge joint, range of motion 0-80 degrees flexion
  • Stabilized by volar plate, capsule, collateral ligaments
  • Extensor tendons cross DIPJ to form the extensor expansion
• Joint stability provided by
  • Joint Capsule
  • Radial Collateral Ligament
  • Ulnar Collateral Ligament
  • Dorsal/Palmar Ligaments

Fingernail

• Located at the dorsal end of the finger
• Specialized structure of the epidermis that is found at the tips of our fingers and toes
• Protects the tips of our fingers and toes as they are the farthest extremities
• Forms a back-support for picking up small objects with the fingers

Movement

(A) Acute paronychia presenting as erythema, swelling and pus discharge along the lateral and proximal nail fold. (B) Acute paronychia of the thumb with subungual abscess

Illustration of typical jersey finger mechanism of injury

• Flexion
  • Flexor Digitorum Superficialis
  • Flexor Digitorum Profundus
  • Facilitated by the Flexor Pulley System of the Hand
• Extension
  • Extensor Digitorum
  • Extensor Indicis Proprius
  • Extensor Digiti Minimi
• Inter-digital
  • Lumbricals
  • Dorsal Interossei
  • Palmar Interossei

Vasculature

• Deep Palmer Arch
  • Radial digital artery of the index finger
• Superficial Palmer Arch
  • Three common palmar digital arteries
  • Branch out along both sides of the middle finger, one side of index and little finger
• Ulnar Artery
  • Palmar digital artery supplies ulnar side of little finger
• Digital arteries run with digital nerves
• Normal capillary refill of the fingertip is < 2 seconds

Innervation

• Median Nerve
  • Innervation: radial side of the palm and the palmar surface of the thumb, index fiոger, long fiոger, radial side of the ring fiոgеr
  • Sensation to the dorsal surfaces of these fingеrѕ distal to the distal interphalangeal (DIP) joint
• Ulnar Nerve
  • Innervation: hypothenar eminence, palmar and dorsal surfaces of the little fingеr, ulnar side of the ring fiոger
• Radial Nerve
  • Innervation: dorsal surface of the palm and fiոgers, from the thumb to the radial side of the ring fiոgеr, proximal to the DIP joints

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Clinical Significance

Comminuted phalangeal tuft fracture of the third digit. The fracture does not extend into the DIP joint. Soft tissue swelling around the distal digit.

Bones/ Joints

• Phalanx Fractures (Hand)
• Metacarpophalangeal Joint Dislocation
• Proximal Interphalangeal Joint Dislocation
• Distal Interphalangeal Joint Dislocation

Tendons/Ligaments

• Extensor Tendon Injuries (Hand)
• Central Slip Extensor Tendon Injury
• Flexor Tendon Injuries (Hand)
• Boutonniere Deformity
• Swan Neck Deformity
• Jersey Finger
• Mallet Finger
• Trigger Finger
• Volar Plate Avulsion Injury
• Sagittal Band Injury

Nailbed Injuries

• Nail Bed Lacerations
• Nail Bed Avulsions
• Subungual Hematoma
• Paronychia
• Felon

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See Also

• Finger Pain Main
• Physical Exam Hand
• Hand and Wrist Anatomy

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