There are three different types of patient that would be suitable for either a var-ising or a valg-ising osteotomy - and it is a spectrum.
The spectrum includes -
Osteotomy to protect mild degrees of joint surface damage within one compartment
At one end of the spectrum may be someone who has pain following the resection of some or all of their shock-absorber (meniscal) cartilage, as well as some joint surface damage which may be relatively minor but is significant enough to cause medial or lateral knee pain. This kind of patient is most likely to benefit from an osteotomy. If they seek surgical help relatively early the degree of wear and tear within the knee may be relatively mild. When the osteotomy is preformed early, the weight-bearing load can be transferred from the problematic compartment to the good compartment and that may be the last time the patient needs to have any surgery on their knee.
In these early cases the signs might be very subtle, ie the patient may be in slight varus (bow-legged) alignment, and it is only when you do the long leg X-rays that you determine the true extent of their mal-alignment.
For instance, if you have a young patient with ongoing knee pain that hasn’t settled with conservative measures, or even arthroscopic chondral or meniscal surgery, then by carrying out an osteotomy, the painful knee compartment can be offloaded, thereby significantly improving their symptoms.
A knee osteotomy is a good pain relieving procedure for the younger, fit patient with localised knee arthritis. It allows that patient to keep their native knee and delay the need for knee replacement.
Osteotomy to protect fragile surgery
The next major group includes patients who need advanced knee surgery and require the best possible environment for that surgery to work. For instance, if the patient has cartilage transplantation surgery, a microfracture, or a meniscal transplantation, and their knee is not well aligned, the surgery has a lower chance of success. So, getting the alignment right is crucial - either for straight-forward knee pain or when creating the best environment for other surgical procedures to succeed. Performing a cartilage transplant procedure in the medial compartment of a patient with varus mal-alignment (who already has very excessive forces going through their medial compartment) is unlikely to work.
Osteotomy as part of management of an unstable knee
Another important but less common indication for osteotomy surgery is in the very unstable knee. Here ligament surgery alone may not be sufficient and the knee may require realignment surgery to allow the required ligament reconstruction to work. The most common problem in this group of patients is severe valgus instability - where there may be a lateral collateral ligament deficiency or following a big posterolateral corner injury when the patient develops a varus thrust. Correcting the alignment from varus to slightly valgus would significantly increase the chance of the lateral/postero-lateral reconstruction working.
When looking at lateral (side-on) x-rays of the knee, the incline at the top of the tibia (tibial slope) can be calculated. If this slope is unusually steep, the femur will tend to roll off the back of the tibia and tends to ‘slide down the hill’. This would be very detrimental in a patient with ACL deficiency. So if a patient is ACL deficient, flattening the slope would improve their knee stability, as the tibia would be less likely to slide forwards on to the femur. In fact, the first surgeons that realised the importance of tibial slope were the veterinary surgeons who noted that just performing an osteotomy to flatten the tibial slope would more than stabilise the knees of ACL deficient greyhounds, making ligament reconstruction itself unnecessary.
The reverse is true in PCL deficient patients (in whom the tibia has a tendency to go backwards under the femur when weight-bearing), who can regain much of their knee stability from an increase in their tibial slope alone (which shifts the tibia forward), without reconstructing the ligament itself.
What about terrible arthritis like extremes of bow legs and knock knees?
This operation used to be done for people like the gentleman in Part 1a whose legs are very bow-legged and whose X-ray shows very arthritic knees medially.
Now, it used to be said that osteotomy was done for these patients and they didn’t do well – and they didn’t do well for all the reasons I have said before – the technique, the fixation device, the post-operative rehabilitation, the planning. Actually these patients now get very good results with osteotomy, and it is a very good alternative to a knee replacement but the indications for surgery have to be met. It was thought that osteotomy didn't work in severely arthritic knees, and that you put patients through a big operation and bought them 2 or 3 years at best. In fact we are now seeing very good 5 and 10 year results with people with severely arthritic knees localised to one compartment who are having this operation.
With the digital pre-operative planning, improved surgical techniques and revolutionary new plates, osteotomy has become a highly successful and well-established treatment for the painful arthritic knee.