Tray of Generic Medical Tools

Tools designed specifically for your knee surgery? It sounds like something that would make sense for every patient. YKC’s Dave Duffy isn’t so sure.

As we’ve explored in these pages previously, a ‘knee replacement’ doesn’t actually replace your knee. It resurfaces it. The implant will contain three basic components: a part that covers the worn end of the thigh bone (a bit like getting a crown at the dentist’s), a part that covers the worn area of the shinbone, and a plastic spacer in between which helps the two to operate in a frictionless way.

Because patients come in all shapes and sizes, implants do too. When knee surgeons ‘replace’ a knee, they choose from a range of differently sized implants, as you would in a shoe shop. Unlike a shoe shop, your correct size will always be available!

This post isn’t about the implant, but it is about the steps a knee surgeon will take to position the implant into your knee joint. The process of knee replacement involves making a series of precise bone cuts to a specific, personalised depth and plane, so the implant can be positioned and secured exactly. It’s a little like preparing your own jigsaw pieces so they fit together perfectly.

We achieve that with jigs and cutting blocks which, once set, help us achieve the precise angles and depths we need. At least, that’s the way knee surgeons have been doing it for years. Now, there’s an alternative.

> Discover more about partial or total knee replacements


What is patient-specific instrumentation?

While the knee implant is chosen to be a match for each patient, the tools we have traditionally used are not. Patient-specific instrumentation takes a personalised approach to the blocks and jigs we use, so that the block and jig used in your knee replacement will have been designed as a perfect match for your anatomy. In theory, it ensures that every cut is absolutely precise and tailored to you, reducing the risk of ‘outliers’, that is, the instances where outcomes are not as we would want.
Some studies have demonstrated that patient-specific instrumentation can improve outcomes and reduce the risk of outliers.

There is, however, a ‘but’.


The issue with patient-specific instrumentation

To be absolutely clear, patient-specific instrumentation doesn’t change the implant that’s going into your knee joint. It’s purely a matter of how you reach that end goal. While there’s an obvious theoretical advantage to personalised instrumentation, things aren’t quite so clear cut in practice.

Personalised instrumentation involves additional scans and, inevitably, creating the dedicated blocks and jigs takes time and costs money.

Then there’s the surgery itself. Here, the argument is very much like that surrounding robots in knee surgery. Yes, a robot can act as a guide, but it can’t do the surgery any more than a personalised jig can make the cut itself.

Patient-specific instrumentation may be a theoretically useful tool but it’s no substitute for surgeon expertise, and I wonder whether the more we use patient-specific instrumentation, the more insight and nuance we remove from surgeon training.

We need our surgeons to have the basic foundation of understanding on which to build. They need to understand the principles of what they are trying to achieve. They need to understand how to plan a procedure and minimise risk. These skills and experiences are not things you can – or should – shortcut, which removes the value in using patient-specific instrumentation in surgeon training.

As a surgeon builds expertise, they can then reasonably make a choice over the instrumentation they use, although at that point it’s hard to make a really compelling case for change because a well-trained and experienced surgeon will typically be able to achieve optimal results (and reduce those outliers) without patient-specific instrumentation.

It isn’t the case that patient-specific instrumentation is inherently ‘bad’ in any way. It is, however, the case that we need knee surgeons to fully understand all elements of the principles of knee replacement before they start taking advantage of expensive shortcuts. And by the time they reach that point, they probably won’t see the value in them anyway.

If you would like your knee replacement to be carried out by vastly experienced specialists, talk to us or phone us on 03453 052 579.

>  Discover more about Dave Duffy
>  Discover more about partial or total knee replacements

Dave Duffy

Dave Duffy

Private appointments weekly at The Duchy Hospital Harrogate & Nuffield Hospital Leeds

Private Secretaries

Amanda Hardy
The Duchy Hospital Harrogate
07889 485 579

Lauren Long
Nuffield Leeds
07930 585 744

Email Dave

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