Elizabeth Thorpe, MD
Pediatric Emergency Medicine Attending
An 11-year-old boy comes to the emergency department with an injury to his elbow. On physical examination, the right elbow is swollen, and he is unable to range it due to pain. The radial pulse is present but slightly diminished. Flexion of the distal interphalangeal (DIP) joint of the index finger and interphalangeal (IP) joint of the thumb is weaker in the right hand than the left. Extension of the thumb and adduction of the fingers is normal. Sensation is intact and capillary refill time is 2 seconds. A lateral radiograph of the elbow shows a supracondylar fracture. Which nerve has most likely been injured?
A. anterior interosseus nerve
B. median nerve
C. musculocutaneous nerve
D. radial nerve
E. ulnar nerve
Pediatric Emergency Medicine Attending
An 11-year-old boy comes to the emergency department with an injury to his elbow. On physical examination, the right elbow is swollen, and he is unable to range it due to pain. The radial pulse is present but slightly diminished. Flexion of the distal interphalangeal (DIP) joint of the index finger and interphalangeal (IP) joint of the thumb is weaker in the right hand than the left. Extension of the thumb and adduction of the fingers is normal. Sensation is intact and capillary refill time is 2 seconds. A lateral radiograph of the elbow shows a supracondylar fracture. Which nerve has most likely been injured?
A. anterior interosseus nerve
B. median nerve
C. musculocutaneous nerve
D. radial nerve
E. ulnar nerve
Answer: A
The AIN is the most commonly injured nerve in extension type SC fractures. It is a motor nerve primarily and NOT a sensory nerve. Injury is often missed because of this. It arises from the median nerve approximately 5 cm above the medial epicondyle of the elbow and runs along the interosseus membrane between the radius and ulna. It supplies the flexor pollicis longus (flexion of the IP joint of the thumb) and flexor digitorum profundus (flexion of the DIP joint) of index and middle fingers.
In flexion type supracondylar fractures, the ulnar nerve is most commonly injured. The ulnar nerve supplies sensory branches to the dorsoulnar and volar aspect of hand and ulnar 1½ fingers. The motor distribution is to the hypothenar and intrinsic muscles of the hand.
Radial nerve injury results in inability to extend the thumb and wrist and sensory loss on the dorsum of thumb, first web space, and hand as far ulnarward as the middle of the ring finger and as far distal as the proximal interphalangeal joint.
Median nerve injury also results in an inability to oppose or flex the thumb, weak flexion/radial deviation of wrist, and pronation but sensation to the volar thumb and radial 2½ fingers and corresponding portion of the palm is supplied by the median nerve.
Pearls for hand motor exam – how to test three nerves at once (radial, ulnar, median)
3 Nerve test - (Kumar Test)
The AIN is the most commonly injured nerve in extension type SC fractures. It is a motor nerve primarily and NOT a sensory nerve. Injury is often missed because of this. It arises from the median nerve approximately 5 cm above the medial epicondyle of the elbow and runs along the interosseus membrane between the radius and ulna. It supplies the flexor pollicis longus (flexion of the IP joint of the thumb) and flexor digitorum profundus (flexion of the DIP joint) of index and middle fingers.
In flexion type supracondylar fractures, the ulnar nerve is most commonly injured. The ulnar nerve supplies sensory branches to the dorsoulnar and volar aspect of hand and ulnar 1½ fingers. The motor distribution is to the hypothenar and intrinsic muscles of the hand.
Radial nerve injury results in inability to extend the thumb and wrist and sensory loss on the dorsum of thumb, first web space, and hand as far ulnarward as the middle of the ring finger and as far distal as the proximal interphalangeal joint.
Median nerve injury also results in an inability to oppose or flex the thumb, weak flexion/radial deviation of wrist, and pronation but sensation to the volar thumb and radial 2½ fingers and corresponding portion of the palm is supplied by the median nerve.
Pearls for hand motor exam – how to test three nerves at once (radial, ulnar, median)
3 Nerve test - (Kumar Test)
- Ask the patient to dorsiflex his/her wrist,
- Abduct the fingers of 3 rd , 4th and 5 th fingers and
- Make a ring (O) sign with thumb and index finger tips touching each other (Figure 1). This single test will assess motor power of all three nerves.
- Inability to dorsiflex wrist indicates Radial nerve weakness
- Inability to abduct the ulnar half of fingers indicates Ulnar nerve weakness
- Inability to appose thumb and index finger tips to make an O sign indicates Median nerve weakness (Flexor Pollicus Longus and Flexor Digitorium Profundus of index finger 1 ).
References
S. Rajkumar, S. Tay: A Single Clinical Sign To Test For Functioning Of All 3 Nerves Of The Hand. The Internet Journal of Orthopedic Surgery. 2006 Volume 3 Number 1. DOI: 10.5580/1019 - See more at: http://www.ispub.com/journal/the-internet-journal-of-orthopedic-surgery/volume-3-number-1/a-single-clinical-sign-to-test-for-functioning-of-all-3-nerves-of-the-hand.html#sthash.CRAUAu7x.dpuf
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