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September 5, 2014 by dailybolusoflr

By Karolina Paziana, MD
Hand and wrist complaints are common presentations to the emergency department, and often require a dedicated tendon exam. The function of the hand, and in particular the thumb, is essential for day to day living. In this review of the hand exam, we will focus particularly on the extensor muscles of the thumb.  Please make sure to make it to the bottom, so you can watch the video referenced below.
Quick Anatomy Review:

i] http://www.msdlatinamerica.com/ebooks/HandSurgery/sid901079.html


[ii] http://teachmeanatomy.info/upper-limb/muscles/hand/

1.       Abductor Pollicis Longus (APL)
a.        ABDUCTS thumb
b.       EXTENDS carpometacarpal joint
2.       Extensor Pollicis Longus (EPL)
a.        EXTENDS distal phalanx at IP joint, MCP and carpometacarpal joints
3.       Extensor Pollicis Brevis (EPB)
a.        ENXTENDS thumb, carpometacarpal joint
4.       Opponens Pollicis
a.        Draws thumb to the center (opposes)
5.       Abductor Pollicis Brevis (APB)
a.        Abducts thumb (helps oppose)
6.       Flexor Pollicis Brevis
a.        Flexes thumb
7.       Adductor Pollicis
a.        Adducts thumb[iii]
          Ask the patient to oppose the thumb to all fingers in turn
          Ask the patient to ADduct the thumb, Abduct the thumb and flex the thumb
          To test extension, ask the patient to put their hand down flat on a surface, hold the hand down and ask them to lift their thumb from the surface – this should make them hyperextend the IP and test MCP extension also.
          Alternatively you may have the patient adduct the thumb while hyperextending[iv]
Only the EPL can HYPEREXTEND the IP joint – hitchhiker’s thumb. If you suspect an  EPL injury you MUST have test for active extension PAST the neutral postion – stick their thumb out like they are trying to hitchhike.
The ADDUCTOR POLLICIS (on the ulnar side) and the ABDUCTOR POLLICIS BREVIS (on the radial side) contribute dorsal expansions that stabilize the extensor tendons and transfer extension forces to the IP joint. The intrinsic muscles of the thumb therefore can extend the IP joint to the neutral position – EVEN IN THE FACE OF AN EPL INJURY – but cannot hyperextend. [v][vi]
Having the patient extend the thumb from flexion to the neutral position is not sufficient to test extension. You must have them hyperflex!

[i] http://www.msdlatinamerica.com/ebooks/HandSurgery/sid901079.html
[iii] Moore, K. L., Dalley, A. F., & Agur, A. M. (2013). Clinically oriented anatomy. Lippincott Williams & Wilkins.
[v] Skirven, T. M., Osterman, A. L., Fedorczyk, J., & Amadio, P. C. (2011). Rehabilitation of the Hand and Upper Extremity, 2-Volume Set: Expert Consult. Elsevier Health Sciences.
[vi] Austin, Noelle M (2005). “Chapter 9: The Wrist and Hand Complex”. In Levangie, Pamela K; Norkin, Cynthia C. Joint Structure and Function: A Comprehensive Analysis (4th ed.). Philadelphia: F. A. Davis Company.

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