Thumb Extension, Abduction, Adduction, and Opposition PDF

# Thumb Extension, abduction, adduction and opposition ## 13th lecture Theoretical Part: Thumb Extension, abduction, adduction and opposition ### **Objectives:** At the end of this lecture the student will be able to: - Identify the primary muscles involved in thumb extension - Identify the range...

# Thumb Extension, abduction, adduction and opposition ## 13th lecture Theoretical Part: Thumb Extension, abduction, adduction and opposition ### **Objectives:** At the end of this lecture the student will be able to: - Identify the primary muscles involved in thumb extension - Identify the range of motion of thumb extension - Identify the primary muscles involved in thumb abduction - Identify the range of motion of thumb abduction - Identify the primary muscles involved in thumb adduction - Identify the range of motion of thumb adduction - Identify the primary muscles involved in thumb opposition - Identify the range of motion of thumb opposition ### **Content:** - Anatomy of primary muscles involved in thumb extension - Range of motion of thumb extension - Anatomy of primary muscles involved in thumb abduction - Range of motion of thumb abduction - Anatomy of the primary muscles involved in thumb adduction - Range of motion of thumb adduction - Anatomy of the primary muscles involved in thumb opposition - Range of motion of thumb opposition ## Extension of metacarpophalangeal and interphalangeal joints of thumb ### **Primary Muscles:** 1. Extensor pollicis longus 2. Extensor pollicis brevis ### **Range of motion:** The range of motion of thumb-metacarpophalangeal joint extension is of 60° - 70 to 0° and thumb interphalangeal joint flexion of 90° to 0°. ### **Anatomy of extensor pollicis longus:** - **Origin:** Middle third of posterior ulna (below abductor pollicis longus) and adjacent interosseous membrane. - **Insertion:** Base of distal phalanx of thumb (Fig. 1). - **Nerve supply:** Radial nerve. - **Action:** Extends interphalangeal and metacarpophalangeal joints of thumb. ### **Anatomy of extensor pollicis brevis:** - **Origin:** Posterior surfaces of radius and interosseous membrane. - **Insertion:** Base of proximal phalanx of thumb (Fig. 2). - **Nerve supply:** Radial nerve. - **Action:** Extends proximal phalanx of thumb at carpometacarpal joint. ### **Effects of weakness:** - **Extensor pollicis brevis:** - Weakness of this muscle decreases the ability to extend the proximal phalanx. - It may result in a position of flexion of the proximal phalanx. - **Extensor pollicis longus:** - Weakness of this muscle decreases the ability to extend the distal phalanx. - It may result in a position of flexion of the distal phalanx. ## Thumb abduction ### **Primary Muscles:** 3. Abductor pollicis longus 4. Abductor pollicis brevis ### **Range of motion:** The range of motion of thumb-metacarpophalangeal joint extension is of 0 to 40-50. ### **Anatomy of abductor pollicis longus:** - **Origin:** Upper posterior surface of ulna and middle third of posterior surface of radius and interosseous membrane between. - **Insertion:** Over tendons of radial extensors and brachioradialis to base of 1st metacarpal and trapezium (Fig. 3). - **Nerve supply:** Radial nerve. - **Action:** Abducts and extends thumb at carpometacarpal joint. ### **Anatomy of abductor pollicis brevis:** - **Origin:** Tubercle of scaphoid & flexor retinaculum - **Insertion:** Radial sesamoid of proximal phalanx of thumb & tendon of extensor pollicis longus (Fig. 4). - **Nerve supply:** median nerve - **Action:** Abducts thumb at metacarpophalangeal & carpometacarpal joints ## Thumb Adduction Motion ### **Primary Muscles:** 1. Adductor pollicis ### **Anatomy of Adductor pollicis:** - **Origin:** - Oblique head: base of 2nd and 3rd metacarpals, trapezoid and capitate. - Transverse head: palmar border and shaft of 3rd metacarpal. - **Insertion:** Ulnar side of base of proximal phalanx of the thumb and tendon of extensor pollicis longus (Fig. 5). - **Nerve supply:** Ulnar nerve. - **Action:** Adducts carpometacarpal joint of thumb. ### **Range of motion:** The Range of motion of thumb adduction is of 40-50 to 0°. ## Thumb Opposition Motion. ### **Primary Muscles:** 1. Opponens pollicis 2. Opponens digiti mini ### **Anatomy of Opponens pollicis:** - **Origin:** Flexor retinaculum and tubercle of trapezium. - **Insertion:** Whole of radial border of 1st metacarpal. (Fig. 6). - **Nerve supply:** Median nerve. - **Action:** Opposes (medially rotates and flexes ) carpometacarpal and metacarpophalangeal joints of thumb. ### **Anatomy of Opponens digiti mini:** - **Origin:** Flexor retinaculum and hook of hamate. - **Insertion:** Ulnar border of shaft of 5th metacarpal (Fig. 6). - **Nerve supply:** Ulnar nerve. - **Action:** Opposes (flexes and laterally rotates) carpometacarpal and metacarpophalangeal joints of little finger.