Lateral Femur

The Lateral Femur is the essential second projection in a femur series, providing a view 90 degrees from the AP projection. This perspective is vital for determining the anterior or posterior displacement of fractures and evaluating the placement of orthopedic hardware. Because the femur is a large, dense bone, achieving a true lateral without the other leg getting in the way requires precise patient positioning and careful management of the horizontal plane.

The Goal

To demonstrate the femur in a 90-degree lateral profile, ensuring the inclusion of both the hip and knee joints and the proper superimposition of the femoral epicondyles.

Patient Positioning

The Setup: Have the patient turn onto their affected side.
The Knee: Flex the knee of the affected leg approximately 45 degrees.
The Unaffected Leg: Have the patient roll the unaffected leg and hip backward to prevent it from superimposing the femur of interest.
The Plane: Ensure the femur is aligned with the long axis of the IR. The shoulder, hip, and knee should be adjusted so the femur is on a single horizontal plane.
Distal (Lower) Focus: To ensure a true lateral of the knee joint, the femoral epicondyles must be perpendicular to the image receptor.
Proximal (Upper) Focus: If the hip joint is the focus, the patient may need to roll back slightly further to clear the soft tissue and bone of the opposite hip.

Technical Factors

Central Ray (CR): Perpendicular to the IR, directed to the mid-point of the femur.
SID: 40″.
Collimation: Must include the joint of interest (hip or knee) and the anterior/posterior skin margins of the thigh.

Image Evaluation Criteria (The “Richie” Checklist)

A professional Lateral Femur must meet these standards:

Joint Inclusion: Both the hip and knee joints must be visualized in lateral profile throughout the series.
True Lateral (Distal): The femoral epicondyles should be superimposed, and the patellofemoral joint space should appear open.
True Lateral (Proximal): The greater trochanter should be superimposed by the femoral neck, and the lesser trochanter should be visible on the medial side.
No Motion: The cortical margins must be sharp and clear to allow for the assessment of subtle fracture lines.
Physical Marker: Your physical R/L marker must be clear and placed in the light field.

Why the Lateral Femur Matters

This view is the only way to accurately assess anterior or posterior angulation of a fracture. It is also critical for surgeons to see how intramedullary (IM) nails or plates are seated within the bone from a side-view perspective. In trauma cases, where the patient cannot be turned, a cross-table lateral (using a horizontal beam) is the required method to obtain this view safely without moving the fracture site.

Richie’s Pro-Tips for the Lateral Femur

Professionalism and Support: Femur fractures are incredibly painful. Use sponges to support the knee and ankle in the lateral position to help the patient hold still, and always ensure they are properly shielded with lead. a joint or leaves a “gap” in the mid-shaft is a failure of technical standards.

The “Hiked Hip” Warning: If the patient’s unaffected hip isn’t rolled back far enough, it will overlap the proximal femur, making it non-diagnostic. Always ensure clear separation.

Physical Markers are Mandatory: Digital markers are not legally or medically sufficient for orthopedic imaging. Always use your lead markers at the time of exposure.

The “Incomplete” Standard: Submitting a series that clips a joint or shows a “diagonal” femur across the IR is an ethical violation and a technical failure.