Upper Extremity Fractures (Scaphoid, Distal Radius, Elbow)
- The arm has three classic "look again" fractures: the scaphoid (sneaky), the distal radius (common), and the elbow (subtle).
- A scaphoid fracture can hide on day-one X-rays — tenderness in the anatomic snuffbox means you treat it as broken even if the film looks clean.
- On a lateral elbow, an abnormal fat pad (especially a posterior one) is the signal that there's a fracture you can't directly see.
- Distal radius fractures live or die by the lateral view: which way the broken piece tilts changes the name and the management.
Three bones in the arm cause more "wait, let me look again" moments than almost anything else in the body: the scaphoid, the distal radius, and the elbow. They all share a theme — the fracture is either hard to see directly, or the real story is in a detail you'd skip if nobody warned you. Consider yourself warned. Let's take them one at a time.
The scaphoid: the bone that lies on the first film
The scaphoid is a little boat-shaped wrist bone (that's literally what scaphoid means — boat) sitting at the base of your thumb. People break it falling onto an outstretched hand, which, conveniently, is how humans break basically everything in the upper limb.
Here's the trouble: a fresh scaphoid fracture can be invisible on the first X-ray. The crack is there, but the bone hasn't shifted and the edges haven't yet resorbed, so the line blends into normal anatomy. You'd have to be psychic. So instead of trusting the film, radiologists trust the exam: tenderness in the anatomic snuffbox — that little hollow at the base of the thumb when you stick your thumb out — gets treated as a fracture until proven otherwise. That usually means a splint and a repeat film in a week or two, by which point the fracture announces itself.
Why all the paranoia over one tiny bone? Blood supply. The scaphoid gets fed from one end, so a fracture across its waist can starve the upper fragment, leading to the part dying (avascular necrosis) or the fracture never healing (nonunion). Miss it, and a "minor wrist sprain" becomes a wrist that aches for the rest of someone's life.
When the clinical suspicion is high but the X-ray is clean, MRI is the most sensitive way to catch an occult scaphoid fracture early — it shows the marrow edema before the cortex ever cracks visibly on plain film.
The distal radius: common, but read the lateral
The distal radius — the forearm bone on the thumb side, right at the wrist — is one of the most frequently broken bones there is, especially in falls. The fracture is usually easy to find. The skill is describing it, and the lateral view is where you earn your keep.
The question that matters: which way did the broken end tilt? Two named patterns dominate, and they're mirror images:
| Pattern | Direction the distal fragment tilts | Classic mechanism |
|---|---|---|
| Dorsally angulated distal radius fracture | Backward, toward the back of the hand | Fall onto an outstretched, extended wrist |
| Volarly angulated distal radius fracture | Forward, toward the palm | Fall onto a flexed wrist |
You don't strictly need the eponyms to be useful — saying "distal radius fracture with dorsal angulation" tells the orthopedist exactly what they need to know. What you must not do is read only the front view, see the fracture, and stop. The front (PA) view can look almost benign while the lateral shows the wrist cocked back like a dinner fork. Always check whether the joint surface is involved and whether the ulnar styloid (the little bump on the pinky side) came along for the ride, because both change management.
Don't anchor on the obvious break and quit. A distal radius fracture is a notorious distractor — while you're admiring it, you can miss an associated dislocation or a second fracture further up the forearm. Trace every bone to its end before you sign off.
If you want the full grammar of how to write up any fracture — displacement, angulation, intra-articular extension — that lives in how to describe a fracture.
The elbow: trust the fat, not your eyes
The elbow is the master of the invisible fracture, and it gave us one of radiology's most elegant tricks: the fat pad sign.
Picture the elbow joint as a sealed water balloon with little pockets of fat tucked against it. Normally a small fat pad sits in front of the bone and you barely notice it, and the back one is hidden in a groove where you can't see it at all. Now break a bone inside that sealed joint: blood and fluid pour in, the balloon swells, and it shoves those fat pads outward like a rising tide lifting boats off the sand.
So on a proper lateral elbow:
- A posterior fat pad that's suddenly visible is the loud alarm — that fat lived in a hidden groove, and the only thing that floats it into view is fluid in the joint. Assume a fracture even if you can't see the line.
- An enlarged, lifted anterior fat pad (the "sail sign," because it puffs out like a sail) points the same direction.
A faint anterior fat pad can be normal — a small sliver in front of the bone is just resting fat, not a fracture. The posterior fat pad is the one that should never be visible on a normal elbow; if you see it, hunt for the fracture.
What's actually broken depends on age. In adults, the hidden culprit is often a radial head fracture. In children, it's frequently a supracondylar fracture — and the pediatric elbow is its own jungle of cartilage and growth plates that show up at different ages, which is why kids' elbows get their own careful treatment alongside pediatric fractures and Salter-Harris injuries.
The one habit that ties them together
All three of these bones punish the reader who looks once and stops. The scaphoid hides on the first film, the distal radius hides its real shape on the front view, and the elbow hides its fracture behind a puff of displaced fat. The fix is the same every time: a second look, the right view, and a healthy distrust of a film that looks "basically fine."
For more bones that love to vanish on the first pass, see subtle but critical fractures and the broader tour of high-yield fractures.