A 54-year-old woman comes to the emergency department due to a hand injury after a fall. The patient slipped in the bathroom and fell backwards onto her extended right hand. She was able to get up but has had right wrist pain and finger numbness since the fall. Medical history is notable for obesity, hypertension, and type 2 diabetes mellitus. On examination of her right hand, there is decreased sensation in the palmar aspect of her first three digits and a small bump is noted just below the palm. Lunate dislocation causing median nerve compression is suspected. Which of the following marked bones on a normal x-ray is most likely dislocated in this patient?

Question

A 54-year-old woman comes to the emergency department due to a hand injury after a fall.  The patient slipped in the bathroom and fell backwards onto her extended right hand.  She was able to get up but has had right wrist pain and finger numbness since the fall.  Medical history is notable for obesity, hypertension, and type 2 diabetes mellitus.  On examination of her right hand, there is decreased sensation in the palmar aspect of her first three digits and a small bump is noted just below the palm.  Lunate dislocation causing median nerve compression is suspected.  Which of the following marked bones on a normal x-ray is most likely dislocated in this patient?

Quizplus · Accepted Answer

11ec160b_35e4_c90c_9249_a3d467f0cd86_MD0001_00 This patient has lunate dislocation after a fall onto an outstretched hand (FOOSH). Although the force transmitted up the arm by a FOOSH can injure many different structures in the arm (eg, elbow, humerus, shoulder), wrist complications are the most common (eg, lunate or scaphoid dislocation/fracture, distal radius fracture). The lunate is in the proximal row of carpal bones and can be identified on x-ray as the more medial (ulnar) of the 2 bones that articulate with the radius. Volar dislocation of the lunate can compress the median nerve within the carpal tunnel, resulting in wrist pain and numbness in the first (radial) 3½ digits. (Choice A) The trapezium is the most lateral (radial) of the distal carpal bones and articulates with the first metacarpal. (Choice B) The capitate is the largest carpal bone; it lies in the distal row at the center of the wrist and articulates with the third metacarpal. (Choice C) The scaphoid is the most lateral (radial) of the proximal carpal bones and articulates with the radius. It is the carpal bone most frequently affected by a FOOSH; dislocation or fracture of the scaphoid can present with wrist pain and tenderness in the anatomic snuffbox. Scaphoid fractures have a high risk of avascular necrosis. (Choice E) The triquetrum is located in the proximal row on the medial (ulnar) side and is partially obscured on x-ray by the pisiform, which lies directly anterior to it. Educational objective: The lunate bone is the more medial (ulnar) of the 2 proximal carpal bones that articulate with the radius. A fall onto an outstretched hand can cause dislocation of the lunate bone with resulting compression of the median nerve (eg, wrist pain, numbness in the first 3½ digits).

A 54-Year-Old Woman Comes to the Emergency Department Due to a Hand