Femoral Neck Stress Fractures: Tension vs Compression-Side Risks and Protocols
In short
Superior tension-side femoral neck stress fractures carry catastrophic risks of avascular necrosis and require urgent surgical pinning; compression-side fractures heal conservatively.
In this guide (4 sections)
The High-Stakes Nature of Femoral Neck Bone Stress
Femoral neck stress fractures represent approximately 5% of all athletic bone stress injuries, predominantly afflicting distance runners, endurance triathletes, and military recruits. Unlike low-risk stress fractures (such as the posteromedial tibia or fibula), femoral neck fractures are classified as high-risk injuries due to the catastrophic consequences of displacement.
Displacement of a femoral neck fracture tears the delicate retinacular vessels ascending from the medial and lateral femoral circumflex arteries, cutting off the arterial blood supply to the femoral head and triggering avascular necrosis (AVN), requiring total hip replacement in young athletes.
Tension-Side vs Compression-Side Stress Fractures
| Clinical Feature | Compression-Side Stress Fracture | Tension-Side Stress Fracture | Displaced Femoral Neck Fracture | |
|---|---|---|---|---|
| Anatomical Location | Inferior medial cortex of the femoral neck | Superior lateral cortex of the femoral neck | Complete transcervical cortical disruption | |
| Biomechanical Force | Subjected to axial compressive loading forces | Subjected to distractile tensile pulling forces | Shear forces cause superior migration of shaft | |
| Risk of Complete Displacement | Low risk; compression forces hold fracture ends together | Extremely high risk; tensile forces pull fracture apart | Already displaced; medical emergency | |
| Treatment Strategy | Non-operative; strict non-weight-bearing crutches 6 weeks | Urgent surgical percutaneous screw fixation mandatory | Emergency open reduction and internal fixation (ORIF) | |
| Avascular Necrosis Risk | Minimal (< 1%) with proper conservative offloading | High (up to 30% if surgical pinning is delayed) | Extremely high (over 50% risk of permanent AVN) |
Diagnostic Surveillance: The Fulcrum Test and MRI Standards
- The Clinical Fulcrum Test: With the patient seated on the plinth edge, place the examiner's forearm under the mid-thigh to serve as a fulcrum while pressing downward on the distal femur; sharp, deep bone pain reproduced at the hip confirms a positive test.
- Zero Reliance on Plain Radiographs: Initial X-rays are completely normal in over 50% of early bone stress injuries; immediate MRI with T2-weighted fat-suppressed sequences is mandatory to detect marrow edema before cortical cracking occurs.
- Addressing Relative Energy Deficiency in Sport (RED-s): Screen endurance athletes for low energy availability, hormonal disruptions, and low bone mineral density (DEXA scan), which triple the risk of femoral bone failure.
Frequently Asked Questions
Why is a stress fracture on the top of the hip bone so much more dangerous than one on the bottom?
The top of your femoral neck is under tension (pulling apart forces), meaning it can suddenly snap completely open while walking. The bottom of the bone is under compression (pushing together forces), which helps it stay stable and heal naturally.
What is the Fulcrum test?
The Fulcrum test is an exam where a physiotherapist places their forearm under your thigh and presses down on your knee. If this creates a sharp, deep aching pain inside your hip, it strongly suggests a bone stress fracture.
How long does a hip stress fracture take to heal?
A compression-side stress fracture requires 6 to 8 weeks on crutches without bearing weight, followed by another 8 weeks of progressive physiotherapy before running can be safely resumed.
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