Femoral neck fractures most commonly follow a fall or blow on the greater trochanter which may be quite trivial. In severely osteopenic bone, the femoral neck may fracture on weightbearing, for example, on rising from a chair. Rarely, a femoral neck fracture follows severe traumatic injury in a child.
On examination, the affected side is shortened and externally rotated. This is because the femoral shaft now moves independently of the hip joint so that ilio-psoas and gravity rotate the femur externally rather than the hip internally.
X-ray reveals a trans-cervical or sub-capital fracture line, with or without displacement - as judged by the amount of mal-alignment between the trabecular lines in the femoral head and neck on either side of the fracture line.
Care must be taken not to miss undisplaced fractures. The patient may be able to weight bear with the fracture line barely visible on the radiograph. Such injuries may displace days or weeks afterwards, or remain stable.
Garden's classification may be used to describe the amount of displacement and impaction.
There is a high rate of non-union and avascular necrosis in displaced fractures. A fracture that is not displaced or impacted carries a good prognosis.
Last reviewed 01/2018