Anatomical ACL

Over this decade there have been two surgeons in particular – Freddie Fu and Charlie Brown – who have done a lot of work on “Where’s the right place to put the ACL?”

[Published 2010]

And the researchers have looked – Freddie Fu in particular – really hard at the anatomy again in the lab, in the cadavers, on CT, on MRI and so on, and what they have discovered is that all these years we have been way out on our tunnel positioning on both the tibia and the femur! So there was this vogue to do 'double-bundle' procedures – two tunnels on the tibia and two tunnels on the femur – to recreate a more anatomical ACL. That procedure has not really taken off as no one can show at the moment a real advantage to the patients either in the clinic or there is no way of testing to say if it is any better than a single bundle. And I think most of us feel at the moment that probably double bundle is not the way to go. There is this famous phrase ‘double bundle double trouble – just keep it simple’. However, what has spun out of all their research is particularly on the femur people were miles out on where they were putting it despite the big debate over the last ten years of the best way of drilling the femur. The traditional way is to do the tibial tunnel first, come up into the femur and then drill the femur. You were very fixed. Once you had drilled that tibial tunnel you had to go that way to drill the femur.

So the Australians came up with this idea of trans-portal drilling where you drill the femoral tunnel and the tibial tunnel independently. So you drill the femoral tunnel first and you drill it through the medial portal with the knee really bent up (well that is the way I like to do it). We all thought we had been doing it brilliantly – we had been viewing from the lateral side and drilling from the medial side. But what is really interesting is that if you look from the medial side and you drill from the medial side you realise that we all tend to put the femoral tunnel a bit too high and a bit too towards the midline and we are not around the clock face enough. We need to bring it lower in the femur as you look at it and you need to bring it actually surprisingly less posterior than we have been putting it but below where we had been putting it. Tim Spalding did a brilliant presentation at BASK looking at all the evidence – everyone’s CTs and everyone’s MRI scans and what everyone is saying. He has worked out that actually if you measured the distance on the medial side – you put in a ruler and you take a halfway point from the back of the femur and the articular surface at the front in the notch below the so-called registrar’s ridge (intercondylar ridge) – if you take midpoint that is the centre of the ACL and it is a long long way away from where people have been traditionally drilling it.

So everyone is now desperately trying to develop a nice technique for doing an anatomical ACL reconstruction in a way that can be replicated by your average surgeon. At the moment the only way of doing it is to look from the medial side and do all the work from the medial side and that is quite difficult you know. It’s quite a small little area that you are working in and it is possible but it is fiddly. Arthrex has developed these nice jigs for drilling – you basically pass a guide wire into the knee and then you externally turn the end of the wire, it has a little crank on it, and it cranks open a little drill and it allows you then to back the drill into the femur – they are called flip cutters  - and are absolutely fantastic. I am hoping to develop a new technique so that you actually look from the medial side and do all the work from the lateral side with some special instruments that go around the corner into the notch and allow you to prepare the femur, mark the femur and then accept this drill bit.

 

That idea of anatomical ACL reconstruction is just so completely different from what people have been doing up to now is going to revolutionise the way that ACL reconstruction gets done. What has been really difficult up until now is actually quantifying where the centre of the true anatomical ACL footprint is on the femur. What Spalding has done is that he has come up with a really simple way of doing it – get a ruler, measure the front, measure the back – it is usually about 20mm – take the halfway point just below the intercondylar notch and there it is, and you’re in the middle. And it’s probably 4 mm lower and 4 mm anterior to what we all used to think it was. So it was way off, way off. The problem is that there is no way of proving that it is any better until we have plenty of data, but the evidence so far is telling us is that what we are doing at the moment is not remotely anatomical.