Computer navigated shoulder replacement – and the art of surgery

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By Harry Brownlow, November 2017

It may sound obvious but in order to get the best results from a joint replacement it probably helps to put it in the right place! When it comes to a shoulder replacement the difficult bit is doing the socket (glenoid). This half of the shoulder joint is deep inside the body and can be hard to visualise clearly. It takes experience and good assistance and meticulous technique in order to see the whole of the glenoid. In very large people or those with very distorted anatomy it can be impossible to expose the bone completely. Even if the socket can be perfectly visualised there then comes the issue of preparing the bone to accept the implant. From preoperative planning with xrays and CT scans the surgeon has an idea about which prosthesis he is going to use and at which angle he will want to insert it. It is likely that the glenoid bone will need some reshaping to accept the implant and that the surgeon may wish to adjust the angle of implantation. Both of these aspects of the surgery are judged by eye. The art of surgery. But even the best surgeon cannot get the angles and orientations right every time. Until now…

A new surgical technique has just been launched in the UK by Exactech who are the manufacturers of my preferred shoulder replacement. Using the preoperative CT scan a 3D computerised version of a patients specific bony anatomy is generated. On a computer screen the surgeon can review the anatomy and identify exactly which implant at which angle would best suit that very particular case. The orientation and depth of glenoid preparation, the implant of choice, and the number and direction of all screws are remembered by the computer. Next day, during the operation, a computer with cameras is set up near the operative site. After some quick calibration, the computer cameras can see the instruments and into the exposed shoulder. Now, when holding the drill, the surgeon can look up to the screen and watch, in real time, the progress of the drill or the reamer in relation to the predetermined plan. He can make constant and dynamic adjustments to ensure that the drilling and reaming are completed as per the plan. This ensures that the socket component is  inserted in the correct place and orientation. The difficult bit of the operation has been completed with confidence! The replacement of the stem and head of the humerus does not need computer navigation as the orientations can be reliably reproduced by eye.

This is a very exciting new development in the shoulder world. Only a handful have been done in the UK. We have just completed our first case in Reading and the procedure went exactly to plan. We hope that by siting the implant in the perfect position that the new joint will work better, that there will be fewer complications and that it might even last longer. All these hopes will need to be demonstrated over time and as yet this is still an unproven technique. Until using computer assisted navigation for shoulder replacement has been shown, by research, to deliver measurable benefit then it will remain outside the NHS. At the moment it is only available to private patients who will also have to pay an additional supplement.

I believe the use of computers to aid navigation will become the norm. Nowadays it is standard practice to use technology to guide needles and cannulas and wires when we used to do it by surface anatomy, feel and experience. Nobody would choose to return to those days. Of course the old skills are still required and a computer cannot help when the live situation is not as had been predicted but why choose not to use a technology that can definitely be of assistance?