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

Who is 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 contra indications 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’s the difference between fixed bearing and mobile bearing for partial knee replacements?
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.

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