Review Question - QID 214384

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Scaphoid Fracture Complications AVN QID: 214384 (M1.OMB.4721)

QID 214384 (Type "214384" in App Search)

A 64-year-old woman presents to her primary care provider with left wrist pain. She states that the pain has been present for nearly 1 month, and she does not remember any antecedent trauma except for a possible fall that she had recovered from without any complications. She has a history of type 2 diabetes mellitus that is controlled by diet and metformin. She has no other medical conditions and takes no other medications except for a multivitamin and calcium. On exam, her temperature is 98.2°F (36.8°C), blood pressure is 124/84 mmHg, pulse is 68/min, and respirations are 13/min. Her extremities are warm and well-perfused with intact distal pulses. She has full active range of motion of all joints in her left upper extremity, but she has tenderness to palpation between the first and third extensor compartments at the level of her wrist. Plain radiographs are taken and shown in Figure A. Which of the labeled in Figure A is at risk of avascular necrosis?

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Label 1

11%

13/116

Label 2

16%

19/116

Label 3

41%

47/116

Label 4

11%

13/116

Label 5

11/116

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This patient with tenderness to palpation at her anatomic snuffbox and a radiograph demonstrating fracture at the scaphoid waist is at risk of avascular necrosis of the proximal scaphoid fracture segment or label 3.

Scaphoid fractures are the most common carpal bone fracture and are typically due to a fall on an outstretched hand. The scaphoid is located in the proximal carpal row, forms the radial border of the carpal tunnel, and articulates with the radius, lunate, trapezoid, trapezium, and capitate. The scaphoid is vascularized by a dorsal carpal branch of the radial artery, which supplies the scaphoid via retrograde flow (from distal to proximal). As a result, a fracture at the scaphoid waist has the risk of interrupting flow to the proximal scaphoid, resulting in avascular necrosis. An exam finding that is characteristic of a scaphoid fracture is tenderness at the anatomic snuffbox, which is located at the wrist between the extensor pollicis longus (EPL, third compartment), and the extensor pollicis brevis and abductor pollicis longus (EPB and APL, first compartment).

Figure/Illustration A demonstrates a scaphoid waist fracture. Originally, labels 2 and 3 compose the scaphoid (arrow demonstrates the fracture line). The proximal segment of the scaphoid is label 3, which is at risk for avascular necrosis.

Incorrect Answers:
Answer 1: Label 1 is the trapezium, which can be involved in carpometacarpal joint arthritis. This is not involved in the fracture here.

Answer 2: Label 2 is the distal segment of the scaphoid. The proximal segment is more at risk for avascular necrosis.

Answer 4: Label 4 is the lunate. This bone articulates with the scaphoid and dissociation can result in scapholunate advanced collapse. However, it is not the bone in question for avascular necrosis.

Answer 5: Label 5 is the radial styloid. This can be involved in distal radius fractures that are also the result of falls from standing; however, is it not the bone in question for avascular necrosis in this situation.

Bullet Summary:
The proximal segment of the scaphoid in a scaphoid fracture is at risk for avascular necrosis due an interruption in the retrograde blood flow that supplies this bone.

ILLUSTRATIONS:

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