Recuperation and rehabilitation after knee osteotomy is generally without complications.
Nonetheless, as with any operation complications can occur, and need to be addressed.
All surgery carries some risk to the patient. The chance of a major complication following an osteotomy is in the order of 1%. The risk include the following:
- Procedure-specific risks: delayed bone union, non union of bone, recurrence of symptoms, further surgery (includes plate removal)
- General risks of surgery: clots, bleeding, infection, wound healing problems
Delayed union and Non-union
Delayed union of the bone is a major problem with any knee osteotomy. Delayed union means it takes a bit longer for the bone to unite to than it should. More serious is ‘non union’ where the bone actually does not ever unite. In this particular operation we like to see the osteotomy gap fill in with new bone within a year, and definitely by 18 months. At this time we should be able to take the plates out. In our series – approximately 100 patients – we have had one case of delayed union (the patient had to go on to be bone-grafted and then did go on to unite) and we have had no non-unions. The main series that is quoted for the TOMOfix plate that we are using now - which is a plate developed from some fantastic work on fractures – is that of Dr Alex Staubli. He has had no cases of non-union, and only a couple of cases of delayed union and they were all in smokers. So it is not a problem we often see.
An osteotomy is also not advised in a patient who has a lot of other medical problems, for instance somebody who has relatively poorly-controlled diabetes, or is obese, very elderly, or has significant skin problems. A good candidate is someone who is fit and healthy, with no heart or lung problems. With regard to age, the cut off is 65 – this is the upper limit of age that you would consider for osteotomy. That is because you need the bone to be in good shape for healing.
Delayed union is not something that a patient has to particularly worry about – it is something that we pick up by monitoring the X-rays. It is more likely in an opening-wedge osteotomy than a closing-wedge osteotomy. In a closing-wedge you have two flat surfaces of bone against each other, whereas in the opening-wedge you are actually opening a gap between the bones that you have to fill in with new bone. Patients used to routinely have that osteotomy gap grafted with synthetic material or their own bone, and what we have now found out is that you really don’t need to put bone substitute in the osteotomy gap. In Alex Staubli’s series his widest opening is about 2 cms and even though he never used bone graft in any of his patients, they all went on to unite. We tend to have a cut off, so that we do tend to pack some bone graft in if we go beyond 12 mms. This is rare. By just being sensible and picking the right patients we have not had a single non-union in over a hundred patients. If the osteotomy gap is over 12 mm and graft needs to be used, we can either borrow patient's own bone (this is ideal) or use bone substitute or donor bone. In the latter case, we mention to the patient that although this is someone else’s bone tissue, it is has been used routinely in major hip and spinal surgery as a form of graft for years and quite safely. So we take chips of properly treated allograft and use this if we are doing a more than 12 mm opening wedge.
One of the advantages of the Staubli TOMOfix plate is that it is a ‘locking plate’ – the screws actually lock into the plate – and it works on the principle of being like one of those frames that you see people walking around with where the wires are coming out of the bone. The idea is that the plate holds the bone still but also creates significant micro-motion at the fracture site - which the cells like and it helps them to do their job, ie. heal the bone Too much movement and they don’t work, not enough movement and they don’t work, but if you allow them to move enough but not too much it speeds up the healing process massively. We use that technology in this new plate. It is a very flexible plate that acts as an internal ‘external fixator’ if you see what I mean – it is put inside the skin but acts very much like that external frame, and instead of having wires coming out of the body you have these long screws going into the bone. Because it is flexible, by allowing movement it significantly aids the healing of the fracture that you have created by performing an osteotomy.
The Tomofix is a robust plate unlike its predecessors, the most notable being the Puddu plate. One of the problems we had with the Puddu plate was that it broke when people mobilised on them, and patients needed to be asked to be non-weight-bearing for six weeks on crutches for the sake of the plate. You can quite safely fully weight-bear from day one on this Staubli TOMOfix plate if you have had a straight-forward osteotomy. The TOMOfix plate is a titanium plate that is specially designed. It has been tried and tested by the AO Foundation - an international world-renowned group dealing with fractures. They have been developed many fixation devices over the last 50 years and Dr Staubli has taken these fixation devices and moved them into the world of osteotomy by producing the TOMOfix plate – an adaptation of the LISS plate, an angular stable plate, made of titanium.
When we were first doing this procedure a few years ago, we put the plate in through a longitudinal incision, but what we tend to do now is do it through a slightly oblique incision which is slightly smaller.
Recurrence of symptoms
If you over-correct someone, then you can over-stress the normal compartment and they can go on to have problems in what was a relatively normal compartment. That used to be a problem when the osteotomy was done in the original haphazard fashion.
To be honest, up until quite recently, when we used the closing-wedge technique(opening wedge only came in about 10 years ago), if you asked the surgeon “How big a piece are you going to remove?” it was always a centimetre! Then surgeons started to template their patients more accurately, and started to work out the closing angles on the lateral side in millimetres. This templating was then applied to the medial side when opening wedge came into vogue, over the last 5-10 years. But with appropriate planning based on long leg X-rays, whether you use a computer or not, you can be pretty accurate as regards to where you are going to place the weight-bearing line. In some units the use of intra-operative X-rays can help confirm whether the correction is accurate. If you get it wrong in someone who has medial compartment arthritis and you overload the lateral side too much they can get lateral osteoarthritis.
More commonly, the problem is insufficient correction. If you don’t move the weight-bearing line enough, then the patient won’t actually get any better. What we tend to do is to think about each patient and their knee individually and work out the optimal amout of correction required. If the problem is early arthritis – just a bit of damage to the joint surface and some meniscal damage – we move the weight bearing line just slightly into the lateral compartment.
If the patient has severe medial compartment wear and is very varus, then you really do want to valg-ise him, I place the weight-bearing line well into the lateral compartment. In advanced cases like this, you are hoping to buy your patient 10 years and carry out a knee replacement when they are 59 as opposed to 49. So recurrence of symptoms isn’t something that we tend to see as a potential problem.
What we tend to see in osteotomy is patients coming in before the surgery and their pain is a 8 or 9 out of 10. What they get from the osteotomy is that they get a reduction in that pain so it is manageable. So most of the time it doesn’t get rid of all the pain, but it reduces it to 2 or 3 out of 10 – so it is a nuisance, a bit of a niggle, but you can be active, do your stuff and not worry about your knee in the same way that you were before the surgery. That’s the kind of result that we are looking for.
If you have under or over-corrected then you need to have a very long and hard discussion with the patient in those first few weeks after the surgery and explain the situation and the options available. This is not something I have any experience with but when I was working on my Fellowship one of the senior surgeons under-corrected a patient. That same week the patient went back to theatre and had the procedure more finely tuned and ended up with a good result.
Further surgery, including plate removal
In 25% of individuals the osteotomy plate causes an irritation, and once the osteotomy has healed up it is a very simple matter to open up the old wound and remove the plate. Patient can walk normally immediately with no crutches and the recovery is very quick. You go home the day after surgery, have a week off work so the wound can heal up and then you can begin normal activities again. It is nothing like the rehabilitation associated with putting the plate in.
Inadvertent damage to nearby structures
We use a tourniquet for the procedure. With the operating time for a straightforward osteotomy just under an hour (sometimes if we are doing complex osteotomies or perhaps double osteotomies the tourniquet goes on for two hours), the use of the tourniquet is not something that leads to complications afterwards.
The wound is medial and the nerves supplying sensation to the skin overlying the tibia come from the medial side so you often end up with a small numb patch over the outer aspect of the leg. Patients don’t worry about it if they know about it – but they don't like if you haven’t warned them about it. The numbness fades over the course of 12 months and doesn’t tend to cause major problems. If you look into the literature, there are lots of papers indicating damage that has been caused with the saw during this operation. At the front you’ve got the patellar tendon which can be cut – this is a disaster. At the back of the tibia are the neurovascular structures – the nerve, artery and vein at the back of the leg. With modern surgery done in a controlled fashion, it is inexcusable to have an injury to the front or the back of the knee. As long as you know what you are doing and you put your retractors where you are supposed to, it just shouldn’t happen. The surgeon warns the patient routinely that these structures are there, and that they can become damaged, but I don’t think you would be able to defend it if you damaged the patellar tendon or the structures at the back of the knee.
With the new techniques, nerve damage is not something you should have a problem with. It is like all these things, if you go and see someone who only does one a year and hasn’t been properly trained, then I think the risks are quite high. But I have never ever seen a nerve problem with this operaion. When I did the ‘Complications of Osteotomy’ talk at our course, I looked into all the papers that have been written on this subject. I also wrote a paper for my old boss Peter Myers on his experience of 300 osteotomies (just about to be published – it has taken quite a long time) at the Brisbane Orthopaedics and Sports Medicine Centre and there were no nerve complications at all and those are 15 year results. Like all these things you want someone who does a lot of osteotomies to do yours.
General risks of surgery
In terms of the other risks associated with osteotomy, deep vein thrombosis, bleeding, infection and wound healing problems, probably the most important complication is infection.
Superficial infection is something that can easily be treated with antibiotics, but deep infection around the plate – which is very rare (somewhere in the order of 1%), is difficult to manage. After the surgery hallmarks of obvious infection are: a wound that becomes hot, painful, breaks down or discharges. More subtle signs are a patient who has been doing well and then suddenly develops slightly more pain and it becomes slightly more painful for them to weight bear. Blood tests may show that the inflammatory markers (blood parameters used to monitor infection) are going up (and not down as you would expect after surgery).
The threshold for washing out the wound and starting antibiotics is low and based on clinical experience and judgement. If the patient becomes unwell or the wound looks red and swollen, an early washout of the wound can significantly reduce the bacterial load and get the infection under control. Then the patient stays on antibiotics until the infection is gone. If you are unable to completely eradicate the infection at least you can suppress the infection until the bone has had a chance to heal up. Infection is very rare but it is the most serious complication.
We use mechanical thromboprophylaxis (clot prevention) in the form of AV pneumatic compression boots. The patient has a boot on the non-operated leg during the procedure and the boot goes on the operated leg as soon as the operation is finished. The boots stay on until the patient is fully up and about, which usually takes 4 or 5 days. When the patients go home we don’t routinely give them blood-thinning medications, because there is no evidence to suggest that it actually offers the patient any benefit. Of course, every patients' risk of developing blood clots is calculated individually and ther anti-clot regimen worked out accordingly.