Neck of Femur Fracture
The fracture line's relationship to the hip capsule decides whether the femoral head's blood supply survives, which in turn decides whether the head is fixed in place or replaced.
In a nutshell
Femoral neck fractures are a blood-supply problem: intracapsular fractures shear the retrograde retinacular vessels and risk avascular necrosis, so displaced ones are replaced; extracapsular fractures spare the vessels and are fixed. Outcome is driven as much by rapid medical optimisation and orthogeriatric care as by the operation itself.
Classic presentation
An elderly patient after a low-energy fall, unable to weight-bear, with a shortened and externally rotated leg and groin pain.
Key points
- Intracapsular fractures (subcapital, transcervical) shear the retrograde blood supply running up the femoral neck, risking avascular necrosis of the head.
- Extracapsular fractures (intertrochanteric, subtrochanteric) lie outside the capsule and spare the blood supply, so the native head can safely be fixed.
- Displaced intracapsular fracture = replace (hemiarthroplasty or THR); undisplaced intracapsular or any extracapsular = fix (screws, DHS or IM nail).
- Leg shortening and external rotation are mechanical, from unopposed muscle pull, not a neurological sign.
- Time to surgery matters: aim for within 36 hours once medically optimised, with orthogeriatric input throughout.
First-line investigation
AP pelvis and lateral hip X-ray to confirm the fracture and classify it as intracapsular or extracapsular; MRI if the X-ray is normal but suspicion remains.
First-line management
Analgesia (including nerve block) and rapid medical optimisation, followed by surgery matched to fracture pattern: fixation if extracapsular or undisplaced intracapsular, replacement if displaced intracapsular.
Exam traps
- A normal hip X-ray does not exclude a fracture in a patient who cannot weight-bear after a fall. Request MRI.
- Displaced intracapsular fractures are replaced, not fixed, because the blood supply is already disrupted.
- Delaying surgery to 'optimise' indefinitely increases mortality; the correct approach is rapid, targeted optimisation followed by surgery within the recommended window.
- A shortened, externally rotated leg is a mechanical deformity from muscle pull, not a sign of nerve injury.
Educational content pending clinical review. Not medical advice.