Standard X-rays, such as the Anteroposterior (AP) view, provide a broad look at the hip joint structure and the side-to-side relationship between the hip socket (acetabulum) and the thigh bone (femur). Because the hip is a complex ball-and-socket joint, specialized projections are required to visualize areas hidden in a standard frontal image. The false profile view is a specialized X-ray technique developed specifically to focus on the front, or anterior, portion of the hip socket, providing a unique perspective unavailable through routine imaging.
Understanding the False Profile View Technique
The false profile view, also known as the Lequesne view, requires precise patient positioning. The patient stands with the affected hip placed against the X-ray detector (cassette). This standing position is a significant difference from routine supine projections, ensuring the image is captured while the hip is bearing the body’s weight, which is relevant for evaluating joint mechanics.
The technique creates a profile view of the anterior acetabulum without requiring a difficult true lateral position. To achieve this projection, the pelvis is rotated approximately 65 degrees away from the plane of the cassette. The foot on the side being imaged is kept parallel, and the central X-ray beam is aimed directly at the center of the femoral head, perpendicular to the film.
This specific, oblique rotation isolates the front rim of the hip socket, projecting it clearly onto the image. A properly executed view demonstrates the affected hip joint in a profile orientation, allowing doctors to assess the bony relationship at the front of the hip.
Key Information Derived from the View
The primary function of the false profile view is to isolate and visualize the anterior acetabular coverage of the femoral head. It provides a clear picture of the degree to which the bony socket covers the joint at the front. The key measurement taken is the Anterior Center-Edge Angle, often referred to as the VCA angle (Vertical-Center-Anterior angle).
This angle is measured by drawing a vertical line from the center of the femoral head and a second line from that same center point to the most anterior edge of the visible acetabulum. The angle formed between these two lines quantifies the amount of bony coverage. This quantitative data is valuable for determining if the hip socket provides sufficient structural support.
Normal values for the Anterior Center-Edge Angle typically fall within a range of 20 to 45 degrees. An angle measurement below 20 degrees suggests a deficiency, meaning the anterior socket does not provide enough coverage for the femoral head. Conversely, a measurement greater than 45 degrees may indicate that the socket is too deep or overgrown at the front.
Diagnostic Applications in Hip Health
The specific information provided by the false profile view is fundamental for diagnosing and characterizing several common hip conditions. It is particularly useful in evaluating mild hip dysplasia, which involves an abnormally shallow or underdeveloped hip socket. While the standard AP view assesses lateral coverage, the false profile view identifies anterior acetabular deficiency, which can be an isolated or accompanying feature of dysplasia.
A low Anterior Center-Edge Angle points directly to a lack of anterior coverage, a finding often missed on a standard X-ray. Detecting this deficiency is important because insufficient coverage can lead to chronic instability and uneven loading of the joint cartilage, potentially accelerating osteoarthritis. The view provides a more complete assessment of the joint’s three-dimensional shape than the standard AP view alone.
The view is also important in evaluating femoroacetabular impingement (FAI), a condition where abnormal contact between the femur and the acetabulum causes pain and joint damage. Specifically, it helps identify Pincer-type impingement, caused by overgrowth of the acetabular rim. In these cases, a higher than normal Anterior Center-Edge Angle indicates anterior over-coverage, where the socket extends too far over the femoral head, leading to premature collision during hip movement.