Review Question - QID 217377

This young female patient has symptoms and radiographic findings consistent with a compression-sided femoral neck stress fracture. The next best step is an urgent MRI to determine the extent of femoral neck involvement (Answer 4).

Femoral neck stress fractures are fractures of the femoral neck that occur secondary to repetitive loading. These injuries come in two patterns, compression side (inferior-medial neck) or tension side (superior-lateral neck). Repetitive loading causes microscopic fractures which propagate due to continued repetitive loading and/or poor capacity for healing. They are common in runners and are classically associated with the female athlete triad of amenorrhea, disordered eating, and osteoporosis. Treatment is dependent on fracture pattern (compression vs. tension) and the extent of femoral neck involvement. The study of choice for determining the pattern and extent of neck involvement is MRI.

Neubauer et al. provide a systematic review of the literature on femoral neck stress fractures in runners. Their study included 48 runners. The authors conclude that patients with a history of prior stress fracture and/or relevant comorbidity (i.e. female athlete triad) had a shorter diagnostic time for evaluation.

Behrens et al. provide a review of the literature on stress fractures of the pelvis and legs in athletes. They note that fractures in locations subjected to tension (supero-lateral femoral neck, anterior tibia, patella, etc.) are at a high risk of progression, and oftentimes require surgery. The authors conclude that MRI is the diagnostic modality of choice.

Robertson and Wood provide a comprehensive review of femoral neck stress fractures in athletes. They note that while small compression-sided femoral neck stress fractures are at low risk of progression, those with greater than 50% involvement of the femoral neck have a high risk of progression and oftentimes require surgical intervention. They conclude that MRI is the study of choice to determine the pattern and extent of neck involvement.

Figure A is an AP radiograph of a left hip demonstrating a sclerotic line along the inferior aspect of the base of the femoral neck, suggestive of a compression-sided femoral neck stress fracture. Illustration A is a T2-weighted MRI of the same patient, demonstrating a fracture line that spans greater than 50% of the femoral neck.

Incorrect Answers:
Answer 1: The patient's symptoms are more consistent with a stress fracture. A patient with infectious arthritis would not likely present with a benign physical examination, or radiographs with a sclerotic focus along the femoral neck.
Answer 2: This would be the correct next step for a tension-sided femoral neck stress fracture, or a compression-sided fracture which spans more than 50% of the femoral neck. This patient's radiographs are consistent with a compression-sided fracture, and MRI is necessary to determine the size of the fracture line.
Answer 3: The patient has radiographic findings consistent with a femoral neck stress fracture. MRI must be performed to determine pattern and size prior to allowing for protected weight-bearing,
Answer 5: The patient has radiographic findings consistent with a femoral neck stress fracture. Immediate return to sport carries a high risk of causing fracture propagation.