From the Guidelines
To determine if one leg is shorter than another, a standing long-leg (hip-to-ankle) radiograph is the most appropriate imaging study. This X-ray should include both legs from the hips to the ankles in a single image, with the patient standing and bearing weight equally on both feet, as it provides for optimal assessment of alignment 1. The use of standing long-leg views allows for accurate measurement of the tibiofemoral angle and of tibial and femoral component alignment, and provides accurate information on the weight-bearing mechanical axis in patients with suspected lower limb malalignment 1.
Some key points to consider when using this imaging study include:
- The routine radiographic examination for evaluation of lower limb alignment consists of standing AP and lateral views and a tangential axial view of the patellofemoral joint 1
- Standing long-leg (hip-to-ankle) views provide accurate information on the weight-bearing mechanical axis in patients with suspected lower limb malalignment 1
- The standard AP knee radiograph is a valid alternative to the hip-to-ankle radiograph for determining coronal plane alignment at the knee, but the longer hip-to-ankle radiograph alone provides accurate information on the weight-bearing mechanical axis 1
In terms of specific techniques,
- AP views obtained in 10° of internal rotation may improve interpretation of varus and valgus alignment 1
- Orthoroentgenography or scanography may be used for more precise measurements, especially when planning surgical correction [no specific reference in provided evidence, but general medical knowledge]
- CT scanography is another option that provides accurate measurements with less radiation than traditional X-rays [no specific reference in provided evidence, but general medical knowledge]
From the Research
Imaging Modalities for Leg Length Discrepancy
To determine if one leg is shorter than the other, various imaging modalities can be employed. The choice of imaging technique depends on the specific requirements of the diagnosis.
- X-ray: Although not mentioned in the provided studies, X-ray is commonly used to measure leg length and detect any discrepancies.
- Computed Tomography (CT): CT scans can be used to evaluate the bones and joints, but they are not typically the first choice for assessing leg length discrepancy 2, 3.
- Magnetic Resonance Imaging (MRI): MRI is preferred for examining soft tissues, major joints, and the spine, making it a suitable option for evaluating leg length discrepancy, especially if the discrepancy is related to soft tissue or joint abnormalities 2, 4, 5.
Considerations for Imaging Choice
When choosing an imaging modality, considerations include:
- The need to visualize soft tissues, bones, or joints
- The presence of any underlying conditions, such as trauma or demyelinating diseases
- The availability and accessibility of imaging equipment
It is essential to consult with a healthcare professional to determine the most appropriate imaging modality for a specific case of suspected leg length discrepancy.