PHOTOGRAPH: ‘PHOTO RESEARCHERS, INC.’/SCIENCE PHOTO LIBRARY
should exist and patients should be referred to an acute knee clinic.
X-ray interpretation Ordering the appropriate X-rays is the fi rst step to making the correct diagnosis. For example, the clinician must decide whether a patient presenting with wrist pain needs wrist X-rays or specifi c scaphoid views, and a focused examination is the key to getting this right. Next, one must assess the adequacy of the views taken. T e
lateral cervical spine X-ray is the most useful in identifying vertebral fractures and dislocations, however the C7/T1 junction is frequently missed off the bottom of the image – an area prone to injury due to the change of the curvature of the spine from lordosis to kyphosis. A minimum of two views of any injured area is mandatory and
oblique views should be obtained where there is a strong clinical suspicion of a fracture that is not readily apparent on standard AP and lateral fi lms. In the case of the shoulder, an axillary view can be helpful and in the knee a ‘skyline’ view, which examines the patellofemoral joint. Knowledge of an area’s anatomy and the normal relationships between bones is crucial when interpreting abnormal X-rays. X-rays should be centered on the area of concern to prevent
parallax distortions. T erefore with a wrist injury, radiographs of the forearm that include the wrist may lead to subtle injuries being missed. Identifying a major long bone fracture from across the room can
be relatively straightforward, however more subtle injuries require a systematic approach to X-ray interpretation. When assessing elbow X-rays, for example, the alignment of the bones must be scrutinised. On the lateral view, a vertical line drawn down the anterior cortex of the humerus should cross the middle third of the capitellum. Similarly, a line extended up the shaſt of the radius should also cross the capitellum. Slight disruptions of these parameters can signify a fracture, or dislocation around the elbow.
AUTUMN 2012
Furthermore, soſt tissue signs, such as a raised anterior fat pad in the elbow, can aid in the diagnosis of subtle fractures. In the knee, the presence of a lipohaemarthrosis can be readily
identifi ed by the presence of a fat-fl uid level in the supra-patellar pouch seen on the lateral X-ray - this is another good example of a soſt tissue sign. T is occurs because fat is released from a fracture or ligament avulsion and fl oats on top of blood, which is denser. Finally, it is important to appreciate the limitations of plain
X-ray in identifying all fractures. If a patient suff ers a fall, sustaining a hip injury and clinical examination is strongly suggestive of a fracture, a normal X-ray does not exclude the diagnosis. As per NICE guidelines, they should go on to have further imaging of the injured area in the form of an MRI or CT scan. T is also applies for suspected scaphoid fractures, as a delay in treatment increases the frequency of non-union.
Summary points for risk reduction • Maintain a high index of suspicion for a fracture in non- weight bearing patients and those with high-risk mechanisms of injury.
• • •
Always perform an accurate examination and localise the site of the injury.
Understand injury mechanisms and patterns and actively look for associated injuries.
Have a low threshold for obtaining additional views and do not accept inadequate X-rays.
• Develop a systematic approach to assessing X-rays. •
Request CT or MRI scans for high-risk areas when a patient appears to have a fracture clinically, but the X-ray looks normal.
Mr Simon J Bennet is an orthopaedics SpR in the Severn Deanery and Mr Michael Kelly is a consultant orthopaedic trauma surgeon at Frenchay Hospital in Bristol
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