TREATMENTS

Osteotomies around the knee

Description

The word osteotomy is used by orthopaedic surgeons to describe, quite simply, the cutting of bone. This straightforward procedure is one of the oldest and best tried techniques in orthopaedics. It is used to straighten bones when they are deformed and it can also be used to alter the line of weight bearing through an arthritic joint to relieve pain.

When is an osteotomy indicated?

Osteotomy is now almost always used only in patients less than 60 years old who are too young for total knee replacement. With the improved results from total knee replacement the place of osteotomy is getting less and less but it is a very good option for people who are really quite young and unfortunate enough to have early arthritic joint usually as a result of injury or repeated injuries. In these patients osteotomy is used to alter the way that weight is taken through the knee joint. In young people the knee will usually wear out either on the inner side or the outside producing a bow leg or knock knee deformity. Correcting the alignment of the leg by an osteotomy or cutting the bone and then fixing it straight will take the weight away from the worn out area and allow it to be taken through the good part of the joint. This will not only relieve pain but prevent further damage to the worn part of the joint.

In young children and adolescents, there are conditions which give rise to quite severe knock knees or bow legs. Here osteotomy to straighten the legs is commonly done to correct these deformities and gives very grateful patients.

How is osteotomy done?

Osteotomies around the knee are done either on the femur or thigh bone above the knee or in the tibia or shin bone below the knee. The decision on where to do the osteotomies is made by the surgeon based on inspection and examination of the patient and after looking at and measuring the x-rays. It is usually helpful to take long x-rays of both legs so that they can be compared and exact degree of misalignment calculated. The appropriate amount off correction can then be worked out before the operation starts.

Under anaesthetic (usually general), osteotomy is performed under very controlled conditions and very carefully. An incision which is often quite small is made over the part of the bone where it has been decided to cut. The bone is exposed and using a very fine saw the bone is simply cut across. The deformity is then corrected either by bending the bone once it is cut into the correct position and holding it there usually with a plate and screws. Alternatively to straighten the bone a wedge of bone, like a slice of cake, is cut out of the bone and then the two cut edges are brought together correcting the deformity. Again this is held either with a plate and screws or sometimes a small metal staple. Whatever metal implants are used they can be left in permanently or removed at a separate operation once the osteotomy has healed, which it does so in exactly the same way as a broken bone heals. It can be expected to be almost fully healed in 6 weeks and certainly completely healed in 3 months.

Post operative care

Depending on the type of osteotomy and how it has been fixed at the operation will determine whether or not a plaster cast is applied to the limb following the operation. More and more nowadays a plaster is not used which allow patients to get out of bed and start walking, often putting some weight on the limb quite early on although crutches will almost always be required. This also allows the knee to start moving as early as possible which is vitally important to prevent further arthritic change.

Examples

Probably the commonest use of osteotomy in knee surgery now is for the patient who has had an injury of the knee during adolescence and has had to have one of the cartilages partly or even completely removed. This means that side of the knee where the cartilage has been removed is not protected and can start to wear out quite early producing deformity at the knee. Osteotomy will correct this deformity and allow weight to be taken on the other side of the joint protecting it for the future and also allowing the patient to get back to some sporting activity, which would not be possible with a knee joint replacement. The benefit of osteotomy can be expected to last ten years after which a knee joint replacement is a good option.