The Human Hand

Overview

The human hand is one of the most intricate and versatile structures in the body, enabling complex movements, communication, expression, and interaction with the environment. This guide provides a thorough review of hand anatomy, its mechanical and functional capabilities, its role in sign language and prosthetic design, and common injuries with rehabilitation strategies. It is intended for students, clinicians, and allied health professionals seeking a foundational understanding of this essential anatomical region.

Anatomy and Biomechanics of the Hand

Bones and Joints of the Hand:

• Carpal Bones (Wrist): Eight small bones form the wrist joint.
• Metacarpals (Palm): Five long bones connecting the wrist to the fingers.
• Phalanges (Fingers): Three in each finger (distal, middle, proximal) and two in the thumb.

Key Joints:

• DIP (Distal Interphalangeal): Fingertip joint.
• PIP (Proximal Interphalangeal): Middle finger joint.
• MCP (Metacarpophalangeal): Knuckles.
• CMC (Carpometacarpal): Base of the thumb; a saddle joint offering multi-directional movement.

Joint Movements:

• Flexion, extension, abduction, adduction, circumduction.
• The thumb CMC joint allows axial rotation and “opposition” – essential for grasping.

Range of Motion and Kinematics:

• PIP joints lead flexion during grip, with the DIP and MCP following.
• During release, extension begins with the DIP and MCP, followed by the PIP.
• The trapezium supports complex thumb mobility.

Muscles and Tendons:

• Flexor Tendons: Located on the palm; bend the fingers.
• Extensor Tendons: Located on the dorsum; straighten the fingers.
• Thumb Muscles: Include flexor pollicis longus, extensor pollicis brevis, and opponens pollicis.
• Link Ligament (Landsmeer ligament): Coordinates movement between DIP and PIP joints.

Hand Function and Real-World Application

Daily Living and Grasp Types:

• The hand supports multiple grip types: pinch, cylindrical, spherical, hook.
• The thumb contributes to half of hand function through opposition and control.

Sign Language Communication:

British Sign Language (BSL):

• Uses over 40 handshapes as linguistic elements.
• Meaning depends on handshape, orientation, movement, and facial expression.
• Lip patterns are crucial for distinguishing signs.

American Sign Language (ASL):

• A natural language developed in the U.S., derived partly from French Sign Language.
• Key phonemic parameters: handshape, movement, palm orientation, location, nonmanual markers.
• Grammar includes SVO order, topicalisation, subject copying, and inflection.
• Fingerspelling used for names and technical terms.
• Iconicity plays a greater role than in spoken languages.

Prosthetic Hand Design Principles:

• Key Challenges: Simulating dexterity, power, control, and sensory feedback.
• Desirable Features: Functional grip, natural appearance, low effort control.
• Thumb Designs: Fixed-position and two-position thumbs simplify mechanics.
• Control Systems:
  • Voluntary-opening: Opens actively, closes via spring tension.
  • Voluntary-closing: Closes actively, opens via spring—preferred for controlled grip.
  • Reflex hands: Combine both systems, offering improved function.
• Cosmetic Considerations: Appearances often conflict with mechanical needs.
• Emerging Priorities: Integration of feedback systems, size variation, and improved articulation.

Hand Injuries and Rehabilitation

Common Finger Injuries:

• Fractures: Breaks in bones; cause deformity, swelling, pain.
• Sprains: Ligament injuries; cause pain, swelling, tenderness.
• Dislocations: Joint misalignments; visibly deformed, intensely painful.
• Tendon Injuries:
  • Mallet Finger: Drooping fingertip.
  • Trigger Finger: Catching or locking.
  • Boutonnière Deformity: Central slip injury.

Causes and Risk Factors:

• Falls, sports injuries, manual work, repetitive tasks.
• Higher risk in older adults and those with joint disease.

Treatment and Rehabilitation:

• Initial care: rest, ice, splinting, or surgery.
• Physiotherapy goals:
  • Pain relief and swelling control.
  • Restoration of range and strength.
  • Prevention of stiffness.
  • Functional retraining.
  • Active patient engagement and education
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Exercises for Prevention:

• Stretching and strengthening.
• Functional tasks.
• Ergonomic adjustments for work and hobbies.

Call-to-Action

Explore more anatomical learning tools and hand health advice at www.OrthoGlobe.org. For rehabilitation services, consult your local physiotherapy clinic or visit www.TheArmDoc.co.uk.

Disclaimer
This guide is for educational use only. It does not replace medical advice from a healthcare professional. For any concerns about injury, treatment, or hand function, please consult your doctor or therapist.