Theatre Radiography during Shoulder Surgery
There are at least three ways to approach theatre radiography during shoulder surgery. The approach usually preferred is from the head end, with the C-arm flipped over, intensifier underneath. Apply a flip from left to right whenever the tube is on top like this. The reason for flipping this way up is that this way C-arms can rotate further forwards over the top of the patient. Even those with extended travel only reach forty five degrees with the intensifier on top, as opposed to ninety degrees underneath.
The table and intensifier are lifted up and the C-arm rotated forward until the face of the intensifier is parallel to the patient who is tilted into a seated, reclined position. If the patient is reclined at forty five degrees then the C-arm will be rotated forty five degrees forwards.
If you have an ‘operator viewpoint’ C-arm e.g. Philips you will need to use the right hand flip button which looks like a left facing (mirror image) R upside down. This is because you are screening from the opposite end of the patient to the default orientation.
If you have a ‘surgeon viewpoint’ C-arm e.g. Siemens you will only need to use the left hand flip button which is a left facing (mirror image) letter R.
Position the Intensifier behind the shoulder then pay attention to the X-ray tube. Looking from behind the machine make sure it lines up with the shoulder. Small tube movements from left to right will have a marked effect on centring whilst the intensifier will hardly appear to move. Look at the C-arm from the side and sight towards the middle of the intensifier, the line should cross through the shoulder around ten centimetres below the A.C. joint.
Once you have flipped as indicated above:
Stand and look at the patient from the foot end. Hold out your left hand to the left. This is the side of the patient which will appear to the left side of the screen. Remember whether it is the medial or lateral side of the patient which will appear to the left of the screen. Whilst imaging the shoulder this direction is anatomically obvious, however along the humeral shaft it becomes rather less clear and needs to be remembered.
The distance to move across the shoulder will (as ever) be one degree per two centimetres. Distances moved head to foot are not so straight forward, this is because with your viewpoint is not following the direction of travel. If you use the cross arm to move forwards and back you will need to move approximately 50% further than usual. Moving the height of the machine up or down will have the same effect. Once you rotate forward more than forty five degrees (sixty degrees is a common alternative view) then you are better to move up in height as this is closer to perpendicular to your viewpoint.
Alternative position: Opposite side
This alternative to the standard positioning can be used for shoulder and proximal humerus. It is not suitable for views of the distal or mid-shaft humerus in abduction as the C-arm will not reach far beyond the shoulder laterally before it touches the table. Notice that in this case as in the standard position the intensifier faceplate is as close as possible to the shoulder.
Below is the position for axial shoulder (Stripp view). With the patient in the forty five degree reclined position the view is achieved with the tube vertical. Although not a true Stripp axial the table usually restricts further angulation of fifteen degrees caudally to achieve a true thirty degree view. The same vertical beam is also easily achievable from the standard position. Always take great care when manoeuvering the C-arm so close to the patient's head.