#treatment - Knee
With arthritis, the articular cartilage in the knee joint wears away, to expose bare bone surfaces. If the cartilage wears away equally in the inner (medial) and lateral (outer) compartments (sides) of the knee, then the ‘gap’ between the bones will reduce symmetrically. However, quite often arthritis can affect one side of the knee more than the other. The medial side of the knee is affected more frequently than the lateral side. If the cartilage on one side only wears away then this can cause asymmetric joint space narrowing, in which case the loaded knee will begin to ‘bend’. This bending deformity can potentially be corrected surgically with a realignment osteotomy, which straightens the leg and offloads some of the pressure off the damaged side of the knee.
‘Osteotomy’ means ‘cutting of a bone’. There are various different types of osteotomy. If there is a varus deformity in the knee then probably the best osteotomy is a medial opening wedge proximal tibial osteotomy. For valgus deformities, probably the best osteotomy is a distal femoral lateral opening wedge osteotomy. With these osteotomies, the bone (either the femur or the tibia) is cut, the alignment of the bone is corrected, the gap in the bone that this causes (which is wedged-shaped) is filled with bone graft, and the position of the bone is then held with a metal plate and screws. The bone then heals up just like a fracture does. The angle of correction of the osteotomy is calculated so as to take the weight-bearing axis away from the damaged compartment and across, slightly more into the other normal side.
Prior to any potential osteotomy being performed, first it is essential that full-length standing weight-bearing views of both legs are obtained, to allow accurate measurement on the actual deformity in the knee. From this, one can calculate the number of degrees of angular correction required and hence the size of the osteotomy wedge.
The tibia is cut at an angle under X-ray guidance with an oscillating saw blade.
The cut in the tibia is cranked open.
The bone is fixed in its straightened position with a metal plate and screws, and the bone gap is filled with bone graft.
(This is an Arthrex Titanium Puddu Locking Plate with an Osferion bone-substitute wedge.)
Realignment osteotomy can give very good results; decreasing patients’ pain, increasing their function and keeping their knees going for longer, and delaying the time when they might eventually end up needing a knee replacement anyway. However, it does not ‘cure’ the arthritis in the knee joint – it just buys extra time for those patients who are too young for knee replacement surgery.
X-rays and MRI scans can often be misleading. Therefore, I always tend to perform a knee arthroscopy prior to any realignment osteotomy (either some time in advance, or else immediately prior to the actual osteotomy, during the same anaesthetic). This is for two reasons: first, to double check the knee, and in particular to make sure that the ‘other’ ‘normal’ compartment in the knee is actually in good enough condition for me to be able to proceed with the osteotomy; second, to tidy up the knee as best as possible (remove any loose bits of cartilage, smooth off and stabilize any rough or unstable articular cartilage, and trim any meniscal tears) as this can make a very significant positive difference to the joint and the patient’s symptoms, on top of the effects of the subsequent osteotomy.
Realignment osteotomy is actually quite a big deal. The surgery is performed as an in-patient, under a general or spinal anaesthetic, with a 2 or 3 days in hospital post-operatively. Effectively, the surgery involves breaking the bones to realign them, and it can take several weeks for the bone to heal and for the patient to make a full recovery. I normally initially keep my patients on crutches, partial weight-bearing, for the first 6 to 8 weeks, until X-rays show some evidence of early bone healing. I then recommend a gradual increase back towards full weight bearing. It can take patients 3+ months to really get over the operation, and anything up to 6 months to really feel the full benefits.
As with all surgery, there are potential risks, and these include:-
- blood clots (DVTs)
- nerve or blood vessel damage
- failure of the osteotomised bone to heal (non-union)
The pain, hassle, risks and time involved with these kinds of procedures are all factors that perhaps contribute to the fact that osteotomy surgery is not actually particularly commonly indicated/performed. However, in those patients with significant deformities (>10o), and with significant symptoms but who are too young to go straight for joint replacement surgery, osteotomy does still remain a very good and useful option in appropriate cases.