Friday, August 28, 2015

Imaging - making sure that the time, money and radiation benefit the patient

A few thoughts regarding the use of imaging modalities for patients with shoulder disorders.

As shoulder surgeons, we use imaging to help establish the diagnosis, to plan surgery, and to evaluate the change in shoulder anatomy with time. A robust approach to imaging the shoulder needs to recognize that (1) it is a three-dimensional structure that cannot be represented by a single planar view, (2) critical relationships - such as the degree of centering of the humeral head - change with the position of the arm, and (3) overlying and superimposed structures as well as metallic implants may complicate imaging the structures of interest. 

It is possible to spend a lot of time, money and radiation dosage on imaging, so surgeons need to develop a judicious approach that yields the information necessary to treat the patient while avoiding the tendency to ‘over image’. A currently discussed question, for example, is whether three-dimensional reconstructions based on CT scans of the arthritic shoulder help surgeons achieve better outcomes for their patients in comparison to imaging consisting only of two standardized plain films?. Or, do complex MRI analyses of cuff muscle fat content lead to better results in the management of rotator cuff lesions? While more may seem better, we need to ask whether there is an incremental benefit to the patient of the increased cost and time and radiation exposure of more elaborate imaging methods.

In imaging the possibly unstable shoulder we need to recognize that the displacement of the humeral head in relation to the glenoid is dynamic – anterior translation may be more apparent on an axillary view when the arm is extended posteriorly, posterior translation may be more apparent when the arm is adducted across the chest, superior translation may be more apparent when the deltoid is contracted isometrically, and inferior instability may be more apparent when the arm is relaxed at the side. While CT arthrography, MRI and MR arthrography with the arm adducted may reveal changes in the appearance of the labrum, they cannot reveal dynamic instability. As a result we see patients having repairs of “SLAP”, “ALPSA”, “HAGL” or “Bankart” lesions even though their symptoms were not those of instability. Only yesterday we saw a patient who demonstrated the 'MRI trap'. She had shoulder pain without a recognized injury. Had an MRI which was interpreted as showing a 'SLAP lesion'. Had a 'SLAP repair'. And now has a painful shoulder that is also very stiff.

In imaging the arthritic shoulder, a standardized anteroposterior view in the plane of the scapula and a true axillary view are often all that is necessary for diagnosis and surgical planning. The true axillary view that shows the ‘eye’ or spinoglenoid notch taken with the arm elevated in the plane of the scapula is known as the ‘truth’ view, because it reveals pathology that would not be expected when imaging (plain film or CT) is performed with the arm at the side. Two important examples are (1) the degree of joint space narrowing seen when the bald central aspect of the humeral head is opposed to the eroded posterior glenoid and (2) the functional decentering seen when the humeral head drops posteriorly into a pathologic posterior concavity (see this post). While CT scans may provide a more reproducible measure of glenoid version than standardized axillary views, it is not clear that CT images lead to any better clinical outcomes in the usual case of shoulder reconstruction. A final advantage of standardized plain films for arthritic shoulders is that the same radiographic views can be compared preoperatively and sequentially postoperatively, whereas postoperative CT scans are costly and difficult to interpret because of the metal artifacts.

So, as we move forward, we have the opportunity to ask, 'will this additional imaging study help me take better care of my patient?'; 'will the additional cost, time and radiation dose translate into a better treatment outcome?'

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