Stress fractures account for 0.7% to 20% of all sports injuries, 80% to 90% of which occur in the lower limb and 1% to 2% occur in the pelvis.1–3 Femoral neck stress fractures (FNSFs) occur more often on the compression (inferior) side than on the tension (superior) side, which is important due to differences in treatment protocols. There is a bimodal distribution of injury, with most occurring in those younger than 20 or older than 40 years of age, with higher rates in women and in sports such as cross-country and gymnastics4 (Fig. 29–1).
Incidence of lower extremity stress fractures. (Reproduced with permission from Brown CR Jr. Chapter 72. Common Injuries from Running. In: Imboden JB, Hellmann DB, Stone JH, eds. CURRENT Diagnosis & Treatment: Rheumatology, 3e New York, NY: McGraw-Hill; 2013.)
Wolf's law states that through mechanisms of mechanotransduction, bone responds and adapts to the forces applied upon it by altering both its internal trabecular and outer cortical structures. Stress fractures result from repetitive submaximal forces occurring with enough frequency for the rate of bone destruction to exceed bone remodeling.5 Risk factors include a rapid increase in frequency, intensity, or duration of a repetitive activity; slower running speed; female gender; amenorrhea; muscle fatigue; strength imbalances; and biomechanical and gait abnormalities; a better overall fitness level is protective of stress fractures.6–9
Diagnosis can be difficult and is often delayed up to 14 weeks, on average, due in part to vague symptoms, poorly sensitive and specific exam findings, and often unremarkable plain radiography early in the course of the disease process.10 The pain is often insidiously progressive, vague, and typically worse with activity and improved with rest. A thorough history and physical should be performed and include a dietary and menstrual history as well as biomechanical and gait analysis.
The physical exam typically reveals tenderness over the area, assuming the location is accessible for direct palpation. With FNSFs, one must rely on other exam findings, such as pain at the extreme ends of passive range of motion, log roll, heeltap, or single-leg standing or hopping.5 Definitive diagnosis is made through radiographic assessment. Plain films are often obtained first, but may take several weeks to demonstrate pathology. If plain films are unremarkable and clinical suspicion remains, bone scan, computerized tomography (CT), or magnetic resonance imaging (MRI) may be obtained, as they demonstrate pathology much earlier in the disease process.11–14
Those looking to increase their physical activity should be counseled, and protocols should be developed, regarding preventive measures. However, once a stress fracture develops, treatment is often conservative, with activity modification to allow time for the bone to heal.15 Patients are typically ...