Femoral Neck Stress and Insufficiency Fractures Workup

Updated: Mar 18, 2020
  • Author: Michael S Wildstein, MD; Chief Editor: William L Jaffe, MD  more...
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Workup

Laboratory Studies

No particular laboratory studies aid in the diagnosis of this disorder; however, a prudent part of the preoperative workup is the ordering of standard laboratory tests (eg, blood chemistries, hemoglobin and hematocrit values, and coagulation profile). When an insufficiency fracture is suspected, the medical workup should include a search for metabolic abnormalities, including abnormal calcium, phosphate, and alkaline phosphatase values.

If septic arthritis of the hip is suspected, assessment of the C-reactive protein (CRP) level, the erythrocyte sedimentation rate (ESR), and the white blood cell (WBC) count with differential is indicated to help rule out an infectious process.

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Plain Radiography

Plain radiography remains the initial imaging examination in the evaluation of suspected hip disease. A standard hip radiographic series includes an anteroposterior (AP) view of the pelvis and cone-down AP and frog-leg lateral views of the affected hip.

The AP view of the pelvis allows evaluation of the contralateral hip for concomitant disease and can be used to exclude osseous or articular abnormalities of the pelvis (eg, sacroiliitis, sacral stress fractures, pubic ring fractures) that could present clinically as hip pain. The AP views of the pelvis and hip are obtained with the feet internally rotated.

The frog-leg lateral view of a hip is obtained with the radiographic beam oriented in the AP direction and with the hip abducted. A groin lateral view of the hip can be used instead in cases of an acute femoral neck fracture or displaced fracture, because the affected hip remains in a neutral position. In this examination, the opposite leg is abducted and elevated and the radiographic beam is oriented parallel to the table, with 20° cephalad angulation.

In the case of a compression-type fracture, the inferior aspect of the femoral neck demonstrates cortical thickening with a hazy, radiolucent center. This radiographic picture may be easily confused with that of an osteoid osteoma if an adequate history is not obtained from the patient.

Transverse-type fractures appear much differently on radiography, the first sign being a faint line of sclerosis across the femoral neck. (See the images below.) If left untreated, these transverse fractures may easily progress to complete neck fractures, with significant displacement and varus angulation.

Anteroposterior and lateral images of 54-year-old Anteroposterior and lateral images of 54-year-old woman with 2-month history of right groin pain with ambulation. Note sclerosis of right femoral neck running perpendicular to trabeculae.
Anteroposterior and lateral images of 54-year-old Anteroposterior and lateral images of 54-year-old woman with 2-month history of right groin pain with ambulation. Note sclerosis of right femoral neck running perpendicular to trabeculae.
Anteroposterior and lateral images of 54-year-old Anteroposterior and lateral images of 54-year-old woman with 2-month history of right groin pain with ambulation. Note sclerosis of right femoral neck running perpendicular to trabeculae.
Anteroposterior and lateral images of 54-year-old Anteroposterior and lateral images of 54-year-old woman with 2-month history of right groin pain with ambulation. Note sclerosis of right femoral neck running perpendicular to trabeculae.
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Bone Scanning

Because of its sensitivity in detecting periosteal injury, bone scanning has been very helpful in the absence of conventional radiographic findings. [26]  In the presence of stress fractures, bone scanning demonstrates focal increased uptake of the radiotracer, at the fracture site. This represents an area of increased bone turnover. One drawback to this modality, however, is that findings on scintigraphy are often negative during the first 24 hours after stress fracture.

The positive predictive value of radionuclide imaging in diagnosing femoral neck stress pathology approaches 68%.

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Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is comparable to radiography in sensitivity and has the added advantage of being more specific for stress fractures; accordingly, it has become the modality of choice for detecting stress pathology. [27, 28, 29, 30]  In several studies, both the sensitivity and the specificity of MRI for femoral neck stress fractures were 100%. With this increased specificity, however, comes a higher price tag.

Besides being less invasive than bone scanning (because it does not require the injection of a radiotracer), MRI provides much more information about the surrounding soft tissues. MRI has been shown to be effective in differentiating stress fracture from malignancy or infection.

Diagnostic MRI of a femoral neck stress fracture yields decreased signal intensity on T1-weighted images and increased signal intensity on T2, as well as short tau inversion recovery (STIR) images with or without a low signal fracture line.

In a study of 305 patients with femoral neck stress fracture, Steele et al found that in patient with a fracture line, the presence of a hip effusion on the initial MRI screening was an independent risk factor for fracture progression. [31]

In a retrospective review of 156 consecutive fatigure-type femoral neck stress injuries in 127 US Army soldiers over a 24-month period, Rohena-Quinquilla et al proposed an MRI classification system for these injuries that is based on patient management and return-to-duty time. [32]

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Computed Tomography

Computed tomography (CT) is typically not regarded as a first- or second-line imaging modality for these fractures, but it may be considered when other modalities yield equivocal results. [33]

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