Femoral Neck Stress Fractures

The femoral neck is at risk for the development of stress fractures because it is subject to forces that are up to eight times of our body weight during impact loading activities (1). The repetitive stress in the femoral neck induces bony resorption faster than the body can produce metabolic repair (2). They make up 5% of all stress fractures (1). Femoral neck stress fractures are most commonly seen in military recruits and distance runners (2). The other most common risk factors identified are female gender and pour baseline conditioning (3). Anatomic risk factors including coxa vara and femoracetabular impingement (5).

The two types of femoral neck stress fractures are categorized as compression or tension sided. The compression side of the femoral neck is localized to the inferior portion of the femoral neck (3). Tension sided injuries are localized to the superior portion of the femoral neck (3).

Compression and tension sided injury (5)

Patients will typically come in with exercise induced groin pain (2). Typically, there is no acute injury or trauma. These injuries typically occur during periods of an increase in volume of activity (2). On physical exam of these patients, up to 70% will have pain with extremes of hip motion (2).

Standard radiographs of the hip are done first to rule out any bony sclerosis, fracture line, or callous formation (1). Diagnosis is typically aided by MRI. An MRI can identify bone marrow edema before a fracture line will be seen on an x-ray.

MRI of grade II femoral neck stress fracture (1)

There are MRI grades to help determine the severity of the femoral neck stress injury (1).

MRI staging of femoral neck stress fracture (1)

An assessment of the patient’s vitamin D level, serum calcium, and parathyroid hormone can also be done after a femoral neck stress fracture is diagnosed (5). Providers can also consider ordering a bone density test (5). A thorough history should also be obtained including menstrual history (5).

A compression sided stress fracture is not at high risk for fracture displacement (1). A study looking at MRI grade and the length of time until running showed that the higher grade injuries took longer to return to running (1). For example, a grade I injury took on average 7 weeks and a grade 2 injury took 13.8 weeks (1). They identified that patients with lower BMI took a longer time to return to running (1). These patients are typically treated with two weeks of non-weight bearing on the side of the injury and then a restricted weight bearing return to activity (1). Guidelines suggest increasing the amount of weight bearing by 25% per week until painless ambulation is achieved (2). Then, a walk-to-run program is started that may take up to 4 months to achieve (2). Early diagnosis and treatment typically leads to a 100% return to previous functional capacity (3). Higher grade injury involving a compression sided fracture that accounts for 50% or more of the femoral neck typically need surgical evaluation (4).

A tension sided stress fracture is at risk for fracture displacement (1). As a result, treatment is typically referred to an orthopedic surgeon to evaluate for surgical fixation (2). However, treatment without surgery has been seen in patients without a tension sided fracture line (2).

To conclude, femoral neck stress fractures can be seen in military recruits and long-distance runners. They can be compression or tension sided. The grading of these injuries is performed with an MRI. Compression sided stress fractures are typically managed nonoperatively, while tension sided stress fractures may require surgery. 

By Gregory Rubin, DO
rubinsportsmed.com

– More Hip Pain: https://www.sportsmedreview.com/by-joint/hip/

– More @ Wiki Sports Medicinehttps://wikism.org/Femoral_Neck_Stress_Fracture

References

1)      Ramey, Lindsay N., et al. “Femoral Neck Stress Fracture: Can MRI Grade Help Predict Return-to-Running Time?” The American Journal of Sports Medicine, vol. 44, no. 8, Aug. 2016, pp. 2122–29. PubMed, https://doi.org/10.1177/0363546516648319.

2)      Bernstein, Ethan M., et al. “Femoral Neck Stress Fractures: An Updated Review.” The Journal of the American Academy of Orthopaedic Surgeons, vol. 30, no. 7, Apr. 2022, pp. 302–11. PubMed, https://doi.org/10.5435/JAAOS-D-21-00398.

3)      Robertson, Greg A., and Alexander M. Wood. “Femoral Neck Stress Fractures in Sport: A Current Concepts Review.” Sports Medicine International Open, vol. 1, no. 2, Feb. 2017, pp. E58–68. PubMed, https://doi.org/10.1055/s-0043-103946.

4)      Steele, Clarence E., et al. “Femoral Neck Stress Fractures: MRI Risk Factors for Progression.” The Journal of Bone and Joint Surgery. American Volume, vol. 100, no. 17, Sept. 2018, pp. 1496–502. PubMed, https://doi.org/10.2106/JBJS.17.01593.

5)      Shaw, K. Aaron, et al. “Femoral Neck Stress Fractures in Athletes and the Military.” The Journal of Bone and Joint Surgery. American Volume, vol. 104, no. 5, Mar. 2022, pp. 473–82. PubMed, https://doi.org/10.2106/JBJS.21.00896.