Hip Fractures
- A "hip fracture" almost always means a break in the top of the femur — the femoral neck or the bumpy region just below it — not the socket.
- Location matters enormously, because the blood supply to the femoral head runs up the neck. Break the neck and you can starve the head, risking avascular necrosis.
- The classic patient is older, fell, and now has a shortened, externally rotated leg they won't stand on.
- Your job on the X-ray is to trace one smooth curve along the bone. A subtle break is a kink in that curve.
- A normal-looking radiograph does not clear the hip. If the story screams fracture, the next step is MRI (or CT) to catch the occult one.
Here is the thing about hip fractures: the word "hip" is a lie. When someone says "Grandma broke her hip," they almost never mean the actual hip joint socket. They mean the top of the thigh bone — the proximal femur — snapped off near where it plugs into the pelvis. So before we go further, let's agree to gently ignore the patient's anatomy lesson and look at the femur.
A quick tour of the real estate
Picture the top of the femur as a golf ball on a tee, tilted sideways. The head is the ball. The neck is the tee. Below that, the shaft flares out into two knuckles of bone — the greater and lesser trochanters — and the region spanning between them is the intertrochanteric zone. (If you want to brush up on naming breaks before this, see how to describe a fracture.)
Why care about these zip codes? Because the blood supply to the femoral head is a needy little thing. Most of it climbs up the neck from below, hugging the bone like ivy on a trellis. That single fact drives almost every decision that follows.
Inside vs. outside the capsule: the line that changes everything
The hip joint is wrapped in a fibrous bag — the capsule — and it attaches along the front of the neck. This splits hip fractures into two great families:
| Fracture type | Where it breaks | Blood supply | Why it matters |
|---|---|---|---|
| Femoral neck (intracapsular) | Within the capsule, along the tee | Threatened — vessels run right through the break | Higher risk of avascular necrosis and nonunion; often replaced |
| Intertrochanteric (extracapsular) | Between the trochanters, outside the bag | Usually preserved — bone here is well-fed | Heals better, but bleeds more; usually pinned/nailed |
A neck fracture happens inside the bag, right where those climbing vessels live. Snap it badly and you've cut the ivy at the root — the head can die. That dead-bone process is avascular necrosis, and it's the slow-motion villain orthopedic surgeons are trying to outrun. This is exactly why a displaced neck fracture in an older adult often gets the head swapped out for metal rather than pinned back together — you can't reliably keep dead-ish bone alive.
An intertrochanteric fracture lives outside the capsule in chunky, well-perfused bone. It tends to heal if you stabilize it, so it usually gets fixed with hardware. The catch: this region is vascular, so these can bleed a surprising amount into the thigh.
Quick mental shortcut: neck = blood-supply problem, often replace the head. Intertrochanteric = mechanical problem, usually fix the bone. Same patient, same fall, very different operation depending on a couple of centimeters.
How to actually read the film
Start with the frontal (AP) pelvis. Run your eye along the smooth S-curve where the femoral neck meets the head — radiologists lean on Shenton's line, an imaginary arc traced along the inferomedial edge of the femoral neck and continuing smoothly onto the underside of the superior pubic ramus. In a normal hip it's one continuous, unbroken curve. A fracture makes it kink, step, or break.
The other tells are a band of increased density where bone has impacted and overlapped, a disrupted bone-spongework pattern, or the femur sitting shortened and externally rotated.
A normal-looking X-ray does NOT rule out a hip fracture. Occult (radiographically invisible) fractures are real, especially nondisplaced ones in osteoporotic bone. If the patient can't bear weight and the story fits, the radiograph that "looks fine" is not the end — it's the beginning. The classic next step is MRI, which lights up the marrow edema around even a hairline crack; CT is the backup when MRI isn't feasible.
Why MRI is the secret weapon
X-rays show cortical bone — the hard shell. But the very first thing a fresh fracture produces is bone marrow edema: a bruise inside the bone that an X-ray is completely blind to. MRI sees that edema like a smoke alarm sees smoke, often before the crack is visible any other way. On a fluid-sensitive (fat-suppressed) sequence, the marrow lights up bright around the fracture, and a true line cuts through it.
In an older patient with hip pain after a fall and normal radiographs, "negative X-ray" plus "can't bear weight" earns an MRI, not a discharge. Missing an occult femoral neck fracture lets a nondisplaced break slide into a displaced one — and that's how a pinning becomes a replacement.
Don't forget the neighborhood
The same fall that breaks a neck can crack the socket or the pelvic ring — that's the territory of pelvic and acetabular fractures. And a few of these breaks are flat-out sneaky, which is why the proximal femur shows up so often in discussions of subtle but critical fractures.
If you remember one thing, make it this: a hip fracture is a story about blood supply and a single smooth curve. Find the curve, check whether it's intact, and ask where the break sits relative to that all-important neck. Everything else — the surgery, the prognosis, the panic level — flows from there.