Femoral Neck Stress Fracture

A femoral neck stress fracture is a bone stress injury of the femoral neck from repetitive submaximal loading, typically causing activity-related groin pain in distance runners, military recruits and dancers.

It is rare, about 3% of sport-related stress fractures, but high risk: a tension-side or extensive fracture can displace, risking avascular necrosis of the femoral head and non-union. When it is suspected, stop weight-bearing and arrange imaging.

Compressive load passes through the inferomedial neck (the calcar). Tensile load develops at the superolateral neck and is normally counterbalanced by gluteus medius and minimus; when they fatigue, tension on the superior neck rises.

The femoral head is supplied mainly by the medial femoral circumflex artery through retinacular vessels running along the neck. A displaced fracture can tear or kink them, causing avascular necrosis.

Repetitive loading outpaces remodelling: a stress reaction (marrow oedema), then a fracture line, then a complete fracture if loading continues.

The pattern drives management:

• •Compression side (inferomedial): an oblique, more stable fracture line, stable until it crosses about 50% of the neck width
• •Tension side (superolateral): a transverse, unstable line, more likely to displace
• •Displaced, on either side: a surgical emergency

Risk factors include female sex, low baseline fitness, low bone mineral density, a sudden rise in training and coxa vara. Low energy availability, with menstrual dysfunction and low bone mineral density, is the Female Athlete Triad and part of relative energy deficiency in sport (REDs).