In
human anatomy, the extensor pollicis longus muscle (EPL) is a
skeletal muscle located dorsally on the
forearm. It is much larger than the
extensor pollicis brevis, the origin of which it partly covers and acts to stretch the
thumb together with this muscle.
Passing through the third tendon compartment,[1] lying in a narrow, oblique groove on the back of the lower end of the
radius,[3] it crosses the wrist close to the dorsal midline before turning towards the thumb using
Lister's tubercle on the distal end of the
radius as a pulley.[2]
The tendon is finally inserted on the base of the
distal phalanx of the thumb.[1]
6.7 to 9.7 centimetres (2.6 to 3.8 in) in length, the tendon passes through a long and superficial
synovial sheath which, passing obliquely from the radial border of the forearm into the thumb, extends from the proximal border of the
extensor retinaculum to the first carpometacarpal joint. In the synovial sheath a proximal and a distal
mesotendon connect the tendon to the floor of the sheath.[4]
The tendon of extensor pollicis longus is supplied by branches from various arteries. Before the tendon enters its synovial sheath, arteries from the
anterior interosseous artery or its muscular branches enter the tendon. The sheath itself is supplied by the posterior ramus of the same artery. In the metacarpal region, beyond the synovial sheath, the tendon is supplied directly from the
radial artery. At the phalanges, the tendon forms a dorsal aponeurosis which is supplied by a digital branch of the first
dorsal metacarpal artery.[4]
Innervation
The extensor pollicis longus muscle receives innervation from the
posterior interosseous nerve (C7 and C8) which is the continuation of the deep branch of the radial nerve.
Function
Extensor pollicis longus extends the terminal phalanx of the thumb. While abductor pollicis brevis and adductor pollicis, both attached to the extensor pollicis longus tendon, can extend the thumb's interphalangeal joint to the neutral position, only extensor pollicis longus can achieve full hyperextension at the interphalangeal joint. This complete extension at the interphalangeal joint is not possible, or considerably more difficult, with the carpal, carpometacarpal, and metacarpophalangeal joints simultaneously extended. Likewise, flexion at the interphalangeal joint by
flexor pollicis longus is considerably reduced in wrist flexion.[2]
It also applies an extensor force at the metacarpophalangeal joint together with the extensor pollicis brevis and extends and adducts at the carpometacarpal joint of the thumb.[2]
Clinical significance
Injury
Tenosynovitis, inflammatory irritation of the synovial sheath, is relatively common in the third compartment after repetitive activities such as drum playing.[5]
Austin, Noelle M (2005). "Chapter 9: The Wrist and Hand Complex". In Levangie, Pamela K; Norkin, Cynthia C (eds.). Joint Structure and Function: A Comprehensive Analysis (4th ed.). Philadelphia: F. A. Davis Company.
ISBN0-8036-1191-9.
Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol. 1: Locomotor System (5th ed.).
Thieme.
ISBN3-13-533305-1.
Schmitt, Rainer; Lanz, Ulrich; Buchberger, Wolfgang (2008). Diagnostic Imaging of the Hand. Thieme.
ISBN9781588904539.
In
human anatomy, the extensor pollicis longus muscle (EPL) is a
skeletal muscle located dorsally on the
forearm. It is much larger than the
extensor pollicis brevis, the origin of which it partly covers and acts to stretch the
thumb together with this muscle.
Passing through the third tendon compartment,[1] lying in a narrow, oblique groove on the back of the lower end of the
radius,[3] it crosses the wrist close to the dorsal midline before turning towards the thumb using
Lister's tubercle on the distal end of the
radius as a pulley.[2]
The tendon is finally inserted on the base of the
distal phalanx of the thumb.[1]
6.7 to 9.7 centimetres (2.6 to 3.8 in) in length, the tendon passes through a long and superficial
synovial sheath which, passing obliquely from the radial border of the forearm into the thumb, extends from the proximal border of the
extensor retinaculum to the first carpometacarpal joint. In the synovial sheath a proximal and a distal
mesotendon connect the tendon to the floor of the sheath.[4]
The tendon of extensor pollicis longus is supplied by branches from various arteries. Before the tendon enters its synovial sheath, arteries from the
anterior interosseous artery or its muscular branches enter the tendon. The sheath itself is supplied by the posterior ramus of the same artery. In the metacarpal region, beyond the synovial sheath, the tendon is supplied directly from the
radial artery. At the phalanges, the tendon forms a dorsal aponeurosis which is supplied by a digital branch of the first
dorsal metacarpal artery.[4]
Innervation
The extensor pollicis longus muscle receives innervation from the
posterior interosseous nerve (C7 and C8) which is the continuation of the deep branch of the radial nerve.
Function
Extensor pollicis longus extends the terminal phalanx of the thumb. While abductor pollicis brevis and adductor pollicis, both attached to the extensor pollicis longus tendon, can extend the thumb's interphalangeal joint to the neutral position, only extensor pollicis longus can achieve full hyperextension at the interphalangeal joint. This complete extension at the interphalangeal joint is not possible, or considerably more difficult, with the carpal, carpometacarpal, and metacarpophalangeal joints simultaneously extended. Likewise, flexion at the interphalangeal joint by
flexor pollicis longus is considerably reduced in wrist flexion.[2]
It also applies an extensor force at the metacarpophalangeal joint together with the extensor pollicis brevis and extends and adducts at the carpometacarpal joint of the thumb.[2]
Clinical significance
Injury
Tenosynovitis, inflammatory irritation of the synovial sheath, is relatively common in the third compartment after repetitive activities such as drum playing.[5]
Austin, Noelle M (2005). "Chapter 9: The Wrist and Hand Complex". In Levangie, Pamela K; Norkin, Cynthia C (eds.). Joint Structure and Function: A Comprehensive Analysis (4th ed.). Philadelphia: F. A. Davis Company.
ISBN0-8036-1191-9.
Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol. 1: Locomotor System (5th ed.).
Thieme.
ISBN3-13-533305-1.
Schmitt, Rainer; Lanz, Ulrich; Buchberger, Wolfgang (2008). Diagnostic Imaging of the Hand. Thieme.
ISBN9781588904539.