40-year-old woman presents to the emergency department with left hand pain after a fall on to an outstretched hand just one hour earlier. Her pain is located on the radial side of her wrist. She is right hand dominant and has no medical or surgical history. She occasionally drinks alcohol but does not use tobacco products or any illicit drugs. She works as an office secretary. Physical examination reveals no bruising or swelling, but she does have tenderness located on the dorsal surface of her radial wrist just proximal to the carpal metacarpal joint of her left thumb. She also endorses pain with axial loading of her left thumb. She has full range of motion in her wrist and fingers with sensation fully intact and 2+ radial pulses bilaterally. X-rays of her left hand, wrist and forearm are all negative for any acute pathology.
Which of the following next steps in evaluation is most likely to reveal the diagnosis?
- A) CT scan of the left hand and wrist
- B) Fluoroscopic imaging of the left hand and wrist
- C) MRI of the left hand and wrist
- D) Open reduction internal fixation of the left wrist
- E) Repeat x-rays in 24 hours
C) MRI of the left hand and wrist
MRI imaging is the most sensitive modality for diagnosing occult fractures of the scaphoid bone. Scaphoid fractures are most common in younger to middle-aged adults after a fall on to an outstretched hand. Pain at the anatomic "snuff box" region (the dorsal surface of the radial wrist just proximal to the carpal metacarpal joint of her left thumb) is a common exam finding as well as pain with axial loading of the thumb which puts pressure on the scaphoid as it articulates with the proximal metacarpal bone of the thumb.
Answer choice A: CT scan of the left hand and wrist, is incorrect. A CT scan will give more clarity than a plain film x-ray, but an MRI is the most sensitive and specific for occult scaphoid fractures, and CT scans are often reserved for pre-operative surgical planning.
Answer choice B: Fluoroscopic imaging of the left hand and wrist, is incorrect. Fluoroscopy will not add any diagnostic clarity as this imaging often has less clarity than x-rays.
Answer choice D: Open reduction internal fixation of the left wrist is incorrect. Open reduction and internal fixation of the wrist is overly aggressive and not indicated at this time.
Answer choice E: Repeat x-rays in 24 hours is incorrect. X-ray imaging is often negative for 1-2 weeks following injury.
Key Learning Point
Scaphoid fractures require a high index of suspicion in order to properly diagnose as x-rays are often negative for 1-2 weeks following injury. They often present with pain in the anatomical "snuff box" region of the hand, and MRI is the most sensitive imaging modality.