ACUTE musculoskeletal injuries form a significant proportion of the workload in both general practice surgeries and accident and emergency departments. Statistics from Edinburgh have shown that approximately one per cent of the population sustain a fracture each year. The consequences of missed diagnosis range from minor pain and inconvenience for patients, to adverse long-term outcomes and chronic functional limitation due to fracture non-union, joint stiffness and the need for later, more complex surgery.
Missed fractures form the majority of diagnostic errors made in A&E. Most doctors who have worked in A&E will remember their consultants at some point asking them to “take another look” at a certain patient’s X-ray, gently informing them they have missed a fracture. Failure to detect an abnormality on an X-ray is the most common error, but failure to take an X-ray due to inadequate examination or appreciation of an injury, or ordering the wrong views also occur frequently. This is particularly true of junior medical staff working in A&E or general practice for the first time.
Clinical diagnosis and patterns of injury
The diagnosis of an acute fracture, like much of clinical medicine, is based upon an accurate history and a focused clinical examination, followed by appropriate imaging. Of crucial importance is the appreciation of injury mechanisms and therefore being alerted to associated injuries.
Often the history taken will be brief and may miss important features. The identification of higher risk mechanisms of injury and patient groups (such as the elderly and others susceptible to fragility fractures) will lead to a greater index of suspicion for certain injuries. For example, falls from a height over 5m are associated with calcaneal fractures. Moreover, this should prompt a search for associated injuries such as pelvic and spinal fractures, remembering that the presence of one major injury may distract both patient and doctor from other injuries. Shoulder pain following a seizure or electrocution is classically associated with a posterior dislocation of the shoulder that can be easy to miss on X-ray. The majority of presentations, however, will occur following relatively minor trauma.
In the assessment of upper limb injuries, the history should clarify the site of pain and swelling and any associated loss of function or movement. Commonly missed hand and wrist injuries include volar plate avulsion fractures, ulnar collateral ligament injuries, fractures of the base of the thumb and scaphoid fractures. Missing these often subtle injuries can lead to chronic pain, early osteoarthritis and reduction of hand function. Examination should elicit signs of bony tenderness, swelling, reduced range of movement and joint laxity. Clinicians should therefore adopt a low threshold for obtaining appropriate X-rays and follow-up X-rays where appropriate (e.g. suspected scaphoid injuries).
The evaluation of forearm injuries should include a careful examination of both the wrist and elbow joints, as a fracture of one bone can lead to shortening and the resultant dislocation of the other. If the radius is fractured and shortens, the ulna tends to dislocate at the distal radio-ulnar joint (Galleazi injury). In the case of an ulna fracture, the radial head dislocates from the radiocapitellar joint at the elbow (Monteggia injury).
Patients sustaining lower limb injuries who cannot weight-bear should be considered to have a fracture until proven otherwise. The Ottawa ankle rules, when applied correctly, have a very high sensitivity for identifying ankle fractures. These involve obtaining ankle X-rays when a patient has the triad of malleolar pain, tenderness and inability to weight-bear. This principle can also be logically applied to other areas of the lower limb.
Knee injury assessment should identify the presence of a haemarthrosis, which the patient will report as immediate swelling in the joint, rather than a reactive effusion taking many hours to develop. In the absence of an obvious fracture, a high suspicion of collateral and cruciate ligament injuries or a chondral injury should exist and patients should be referred to an acute knee clinic.
Ordering the appropriate X-rays is the first step to making the correct diagnosis. For example, the clinician must decide whether a patient presenting with wrist pain needs wrist X-rays or specific scaphoid views, and a focused examination is the key to getting this right.
Next, one must assess the adequacy of the views taken. The 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 films. 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 centred on the area of concern to prevent parallax distortions. Therefore 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 shaft of the radius should also cross the capitellum. Slight disruptions of these parameters can signify a fracture, or dislocation around the elbow. Furthermore, soft 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 identified by the presence of a fat-fluid level in the supra-patellar pouch seen on the lateral X-ray - this is another good example of a soft tissue sign. This occurs because fat is released from a fracture or ligament avulsion and floats 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 suffers 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. This 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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