Muscle Power in Hand and Fingers

Overview

This lecture covers the assessment of muscle power in the hand and finger muscles, including specific movements, involved muscles, their nerve supply, and testing techniques.

Movements to Assess in Fingers

• Assess finger flexion, extension, adduction, abduction, and opposition of the little finger.
• Ask the child to perform each movement; add resistance to test muscle strength.

Flexion of Fingers

• Test flexion at metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints.
• FDP (flexor digitorum profundus) flexes the DIP, supplied by median (radial head) and ulnar nerves (ulnar head).
• FDS (flexor digitorum superficialis) flexes the PIP and MCP, supplied by the median nerve (C8-T1).
• Interossei and lumbricals assist in MCP flexion, supplied by deep palmar branch of ulnar nerve (C8-T1).
• Making a fist involves flexion at all finger joints and thumb flexion.

Extension of Fingers

• Test extension by having the child resist downward pressure on extended fingers.
• EDC (extensor digitorum communis) extends MCP joints.
• EIP (extensor indices proprius) extends index finger; EDM (extensor digiti minimi) extends little finger.
• All extensors supplied by posterior interosseous branch of radial nerve (C7-C8).
• Interossei and lumbricals extend the PIP and DIP joints.

Adduction and Abduction of Fingers

• Adduction: Child brings fingers together or holds paper between fingers; muscles are palmar interossei.
• Abduction: Child spreads fingers apart against resistance; muscles are dorsal interossei, except abductor digiti minimi for the little finger.

Opposition of Little Finger

• Test by having the child move the little finger toward the thumb.
• Opponens digiti minimi is responsible, supplied by ulnar nerve (C8-T1).

Key Terms & Definitions

• Flexion — Bending a joint, decreasing the angle between bones.
• Extension — Straightening a joint, increasing the angle between bones.
• Adduction — Movement toward the midline of the hand.
• Abduction — Movement away from the midline of the hand.
• Opposition — Movement where the thumb or little finger touches another finger.
• FDP — Flexor digitorum profundus, flexes DIP joints.
• FDS — Flexor digitorum superficialis, flexes PIP and MCP joints.
• EDC — Extensor digitorum communis, extends MCP joints.
• EIP — Extensor indices proprius, extends index finger.
• EDM — Extensor digiti minimi, extends little finger.

Action Items / Next Steps

• Practice assessing finger and hand muscle power as described.
• Prepare for the next lecture on assessment of thumb muscle power.