Jon Waite

Why do you perform partial knee replacement instead of total knee replacement?
I perform partial knee replacement surgery because I like to be as bone conserving as possible with the operation I am doing I believe that for me it depends on the pattern of the disease the patient has.  If they fulfil the criteria that I insist on for partial knee replacement then it does not make any sense to me to take away two-thirds of the knee if it’s normal, effectively. 

Anecdotally if you talk to patients a lot more of them feel that their knee feels more normal than it does if they have a total knee replacement and I discuss that with them post operatively.  I am not persuaded by anything other than their pattern of disease and for me if they fit that pattern of disease then that’s the best operation and that’s what I tell them

What’s the ideal patient for partial knee replacement?
The ideal patient for partial knee replacement is somebody that, well like for any op, they have to be motivated they have to have the right disease pattern which means that they have isolated disease and if we are talking about medial compartment disease which is by far the most common, they need to have ligaments that are intact and functioning normally and preserved lateral and patella femoral compartment and if that’s the case then as far as I am concerned partial knee replacement on the medial side is the best operation for them.  I would never talk about total knee replacement in somebody that fulfils my criteria for having that condition and that’s irrespective of age, occupation, level of activity or anything really I would go by disease pattern rather than anything else as far as the patient is concerned.

Do you think that partial knee replacement is a good alternative to high tibial osteotomy?
I think for me any joint replacement surgery should be reserved for people who have got full thickness articular cartilage loss in the joint and I think in that situation HTO doesn’t give as good results but by the same token putting joint replacement in someone that does not have full thickness articular cartilage loss again in my experience gives very variable results and I‘m not keen on that so I would reserve HTO for somebody that still has some articular cartilage left in their joint and still has some malalignment for people who have full thickness articular cartilage loss I prefer to go down the route of joint replacement surgery.

Who would you not perform partial knee replacement on?
There are a few standard indications for partial knee replacement which include isolated disease in one compartment of the knee, intact ligaments, preserved remaining compartments of the knee and I think if you fulfil those criteria that then partial knee replacement is a good procedure.  There are occasionally people who have inflammatory joint disease that have osteoarthritis as well and I think partial knee replacement in that situation is the wrong thing to do, so someone with rheumatoid arthritis for instance I think it is too risky so I would not perform it in that situation…but  If you go to meetings around the world you will hear particularly if you go to America patients will be judged on their age, their weight particularly and that sort of thing as far as I am concerned that has no bearing on my decision making about the operation.  I perform it on patients ranging from 30’s up to 80’s and I’m not persuaded that age is a factor in fact I find that in particularly overweight people partial knee replacement surgery is technically a lot easier than total knee replacement surgery but again it is based on disease pattern not any other kind of existing factor so really obviously you need the joint to be free of infection and all the other obvious contraindications but I suppose inflammatory arthritis would be my main complication along with ligament deficiencies.

What are the main advantages of partial knee replacement?
Short term advantages I would say it’s a smaller operation in terms of the physiological insult to the patient, it’s done through a smaller incision it violates less of the soft tissues and obviously you’re taking away less bone so it tends to be less painful, patients tend to get over the operation quicker and get back to walking, driving and what they would describe as a normal level of activity quicker.

How well educated are GP’s about partial knee replacement?
I think there are still huge misconceptions about partial knee replacement surgery.  I think there is still a  belief that it is a stepping stone to needing total knee replacement surgery at a later date and I believe fundamentally that, that is not true of medial and lateral partial knee replacement.  I think the issue of patello-femoral replacement is more debatable, but certainly I tell patients that if I am putting a unicompartmental replacement in their knee whether it be medial or lateral that it is a definitive treatment for their pattern of disease and assuming that they fulfil the pattern of criteria then there is no reason to believe that the remainder of their knee is then going to go on and become degenerate.  And the number of people that have a partial knee replacement revised to a total knee replacement because the remainder of the knee wears out is relatively small and I think that if you are critical about looking at the initial operation I think often you find that the initial surgery over corrects the deformity that they have and therefore overloads the retaining compartment and therefore to some extent pre-disposes them into getting wear and tear on the remainder of the knee but if the procedure is done technically well enough in the first place then there is good evidence that these partial knee replacement’s last as long if not longer than total joint replacements.

Are there any differences in surgical procedure between partial knee replacement and total knee replacement?
With partial knee replacement and total knee replacement surgery are two very different entities...in many aspects partial knee replacement surgery is technically more challenging and there are intricacies that again like most  surgery comes with experience.  Effectively you are trying to fit a joint replacement in a knee joint that is mostly normal so you have to fit it within the confines of the ligaments and soft tissue structures that are already there whereas in total knee replacement surgery almost you are putting the implant in and adjusting the soft tissues around the implant to balance it which is completely opposite for partial knee replacement surgery.

What is your recommendation for surgeon education for a knee surgeon wanting to get into partial knee replacement?
Obviously you need to go down the route of being educated in the surgical technique for partial knee replacement surgery I think most of the orthopaedic companies that sell partial knee replacement’s are keen on educating surgeons and there are various courses that are run from that point of view.  My experience has been mostly with the Oxford partial knee replacement and the course that I first experienced when I was training in Oxford has now progressed and is run on a regular basis.  It’s a very good course covering the whole aspects of indications, surgical techniques, ongoing care of patients and I think I would certainly suggest that anyone who is keen on pursuing partial knee replacement surgery gets well educated on a course of that nature.

Have you noticed an increase in the number of partial knees in relation to total knees that you perform?
50% of the knee replacements that I perform are partial replacements again whether that be medial or lateral or patellar femoral replacement.  I must say that I find partial knee replacement hugely rewarding and I think patients do as well.

How would you explain to a patient what partial knee replacement is?
I spend quite a lot of my time trying to explain the difference between what is labeled a partial and a total knee replacement.  I think of a knee as three parts the inside or medial side of the knee, there’s the outside or lateral side of the knee, there’s underneath the kneecap or the patella femoral joint and I explain that effectively we are now capable of replacing all those three parts as an individual or we can replace them in one operation as a whole that there are patterns of osteoarthritis and not everybody fits into one pattern but there are very common patterns and we now know that the pattern of osteoarthritis where you wear out the inside of your knee first is by far the most common so there are a huge number of patients who come to see me where the only part of their knee that’s worn out is the inside, the medial part of the knee and assuming that they haven’t got a significant deformity, that the ligaments are ok and they haven’t got any inflammatory disease problems then just replacing that bit of the knee that’s worn out and leaving the remainder of the knee that’s in good condition seems to make sense and that’s borne out in the results for partial knee replacement surgery. 

What’s the difference between fixed bearing and mobile bearing for partial knee replacement?
In the same with as with total knee replacement’s, fixed versus partial knee replacement is a sort of…is a design concept that in practical terms, the polyethylene or the plastic that fits between the metal on top of the shin bone and on the end of the thighbone is either fixed onto the tibial component, the bit on top of the shin bone or it’s free to move in which case it’s held in place by the ligament tension in the ligaments in the knee.  There are perceived advantages and disadvantages of both I use the Oxford^® Partial Knee Replacement that I use is a mobile bearing design so that plastic is press fitted under the tension of the surrounding ligaments and it gives the knee the ability to move biomechanically slightly more normally and that’s meant that the implant has certainly on laboratory testing good wear resistance and there is to some extent good evidence that the implant lasts a long time when its implanted in a patient.  For me the benefits of the partial knee replacement is more important because you are keeping all the knee ligaments normal so you are therefore allowing the knee to move normally and you’re trying to just produce as little stress on the implant and the bearing surface as you can and  a mobile bearing to my mind seems to make more sense.

Do surgeons in training learn about partial knee replacement?
There’s a huge variety in the quality and quantity of the training that people get and particularly nowadays as people’s training gets less and less.  I think there are people that definitely have an exposure that is variable particularly if you work in a big teaching hospital you are most likely to come across a specialist surgeon who does unicompartmental knee replacement. 

How long have you been performing partial knee replacement surgery?
I’ve been performing partial knee replacement surgery for about 6 years now…I first came across it during my orthopaedic training in Oxford where obviously one of the partial knee replacement was designed so I was exposed to it fairly early on in training and got involved in some of the research around it and started to understand some of the concepts and for me it fits very sensibly in the package of problems I see in patients with knee arthritis and so as I went on and I saw more patients that fitted the right criteria, I saw them go through surgery and I saw the outcomes I was firmly of the belief fairly early on that they did certainly in the short term they did better and in the long term as well so I became keen on it and as I’ve gone on I’ve got more experience with it and I perform a much higher percentage now than I used to.

These interviews have been conducted and are being published upon obtaining patient and surgeon consent for this purpose