“Rock Paper Scissors”: A Mnemonic for Testing Peripheral Nerve Motor Functions of the Hand

In Tiny Tips by James KongLeave a Comment

Upper extremity injuries are one of the common reasons for visits to the emergency department. A quick physical exam, including both motor and sensory exam of the hand, can help triage the severity and urgency for referral to upper extremity specialists. When assessing the distal peripheral nerve motor functions of the hand, try using this mnemonic: “Rock, Paper, Scissors”.

Peripheral NerveMuscles InnervatedMovementMnemonics
Median​1​Flexor Digitorum SuperficialisFinger FlexionRock
 Flexor Digitorum Profundus  
 Flexor Pollicis LongusThumb Flexion 
 Flexor Pollicis Brevis*  
 Opponens PollicisThumb Opposition 
    
Radial​1​Extensor Carpi Radialis LongusWrist ExtensionPaper
 Extensor Carpi Radialis Brevis  
 Extensor Carpi Ulnaris  
 Extensor Digitorum (Communis)Finger Extension 
 Extensor Digiti Minimi  
 Extensor Indicis  
 Extensor Pollicis LongusThumb Extension 
 Extensor Pollicis Brevis  
 Abductor Pollicis Longus  
   
Ulnar​1​Palmar InterosseiFinger AdductionScissors
   * not imaged below
Figure 1.Muscles innervated by the median nerve (blue) and the radial nerve (red)​2​
Figure 2. Palmar interossei muscles innervated by the ulnar nerve​2​

The combinations of movements by muscles innervated by the three peripheral nerves make up the gestures of “Rock, Paper, Scissors”.

Median Radial and Ulnar are also in alphabetical order, corresponding to Rock, Paper, Scissors, respectively. An examination of the peripheral nerve motor functions should entail the assessment of active and passive movements as well as resisted isometric strength of each muscle group. The sensory function of the three peripheral nerves should also be examined carefully in addition to motor function examination.

This post was reviewed by Daniel Ting and copyedited by Pouria Rezapour.

References

  1. 1.
    Magee D. Orthopedic Physical Assessment. 6th ed. St. Louis, MO: Elsevier; 2014.
  2. 2.
    Betts G. The Muscular System. Anatomy & Physiology. https://openstax.org/details/books/anatomy-and-physiology. Published 2017.

Reviewing with the Staff

Testing the peripheral nerves of the upper extremity are a key part of the musculoskeletal exam to rule out neurovascular injury in the Emergency Department. Muscles of the forearm and hand are incredibly intricate, numerous, and hard to remember outside of the classroom or exam date. Mnemonics like this one that use simple terms like rock-paper-scissors help to integrate a thorough assessment into your routine physical exam.

Daniel Ting
Daniel Ting is a medical educator who currently works at the University of British Columbia as an emergency physician. During his residency he completed the CanadiEM Digital Scholarship Fellowship program. He is currently the Editor-in-Chief of CanadiEM.
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James Kong

James Kong

James is a senior medical student at University of Manitoba. He has interests in medical education, quality improvement and emergency/sports medicine.