Overview
This lecture explains the clinical examination methods for assessing thumb muscle power, including movements, involved muscles, and their nerve supply.
Movements to Assess in Thumb Muscle Power Examination
- Assess palmar abduction, radial abduction, palmar adduction, ulnar adduction, opposition, flexion, and extension of the thumb.
- Each movement is tested actively and against resistance to evaluate muscle strength and function.
Palmar and Radial Abduction
- Palmar abduction: Child lifts thumb vertically at a right angle to the palm; muscles involved are abductor pollicis longus (APL) and abductor pollicis brevis (APB).
- Radial abduction: Child moves thumb horizontally away from the palm; muscles involved are abductor pollicis longus (APL) and extensor pollicis brevis (EPB).
Palmar and Ulnar Adduction
- Palmar adduction: Thumb moves at right angle to the palm to touch the index finger; muscle is adductor pollicis.
- Ulnar adduction: Thumb held parallel to other fingernails, touches radial side of index; muscle is adductor pollicis.
Opposition (Apposition) and Flexion
- Opposition: Child touches tip of thumb to tip of little finger; muscle is opponens pollicis.
- Flexion: Assessed at distal interphalangeal (DIP) and metacarpophalangeal (MCP) joints separately; muscles are flexor pollicis longus (DIP) and flexor pollicis brevis (MCP).
Extension Movements
- Extension at distal interphalangeal joint: Child extends tip of thumb; muscle is extensor pollicis longus (EPL).
- Extension at proximal interphalangeal and MCP joints: Child extends thumb at MCP/IP joints; muscle is extensor pollicis brevis (EPB).
Key Terms & Definitions
- Palmar Abduction — Thumb moves away from palm in a vertical plane.
- Radial Abduction — Thumb moves away from palm in a horizontal plane.
- Palmar Adduction — Thumb adducts at right angle to palm, touching index finger.
- Ulnar Adduction — Thumb adducts in the plane of the palm, touching index finger side.
- Opposition — Thumb tip touches tip of little finger.
- Flexion — Bending the thumb at DIP or MCP joints.
- Extension — Straightening the thumb at DIP or MCP joints.
Action Items / Next Steps
- Practice all thumb power examinations as described.
- Review nerve supply and primary muscles for each thumb movement.