Mind the Gap

​This 20-year-old right-handed patient came in with an obvious deformity of his hand after hitting a wall. Can you see two clues to the injury with just this AP film?I'd surmise that your eyes are drawn to the fifth metacarpal, which is good because this looked like a boxer's fracture. Boxer's fractures, however, are most frequently at the fifth metacarpal neck. There was no fracture, but the fifth metacarpal head seemed way too close to the fourth. The angle of the bone was all wrong. It should be pointing out, not in.I'll give another hint: The deformity seemed to be at the base of the fifth metacarpal. Now what do you see?Notice anything strange about the hamate to fifth metacarpal joint? The bones were overlapping! The joint should normally have about a 2 mm gap. OK, the index finger didn't seem to have that gap. This is true. Sometimes anatomic variation can make the first and second metacarpal carpal joint look funny, most probably because of the need to have wide range of motion of the thumb. From 3 to 5, the joint line should be a parallel M.The internal oblique clearly showed the fifth metacarpal dislocation with a small avulsion off the hamate. These injuries are uncommon, but when they do happen, the mechanism is often hitting a wall. An ulnar nerve block or conscious sedation should make this go in relatively easily.And it did!Tip to Remember: Check the metacarpal-carpal joint line. From at least 3 to 5, there should be a 2 mm gap the entire way across.T...
Source: Lions and Tigers and Bears - Category: Emergency Medicine Tags: Blog Posts Source Type: blogs