Osteotomy for Arthritis Of the Knee
An osteotomy is an operation in which a bone about the knee is realigned. This is done to transfer weight away from a damaged part of the knee to a normal compartment. By unloading the damaged part of the knee pain can be significantly reduced, the rate of further wear will be diminished and the life of the joint can be prolonged.
An Osteotomy can provide good function and pain relief for many years. When successful which is 80-90% of the time in appropriate cases, the result is not only better than a knee replacement, but can delay replacement for 10-15 more years in most cases.
As a general rule when the deformity is varus (bow legged) the correction is made in the tibia (shin bone) and when the deformity is valgus (knock knees) the correction is done in the femur (thigh bone).
|Opening Medial Tibial Osteotomy
||Opening Lateral Femoral Osteotomy
Who is suitable for osteotomy
To get best results certain criteria:
- The wear needs to be confined to one compartment.
- The weight bearing line (A line from the middle of the hip to ankle) passes through the damaged compartment.
- The patellofemoral (knee cap) joint needs to be relatively asymptomatic.
- The knee joint needs to have a good ROM and ideally can go straight.
- Low risks of non-union (bones joining together).
The advantage of osteotomy
- The joint is not artificial (metal and plastic of a knee replacement) and therefore it does not have a specific lifespan. This is why it may be recommended especially if you are in a younger age group.
- Rarely any further restriction of motion to the knee.
- When successful the knee feels "normal", and it allows moderate activity such as cycling and swimming.
- Unlike knee replacement most people can kneel and squat.
- If it fails then a replacement can still be undertaken. This is easier than revising a total knee replacement.
Longevity of Osteotomy
Current figures would suggest that most people can expect 10-15 years of good function from there osteotomy. There are however a good number who function to well past 20 years, and some who never end up with a replacement. On the other hand, there is a also a smaller group who do not get significant relief from their osteotomy despite good correction of alignment. This group represents about 10% of all osteotomies, and come to premature knee replacement because of this.
Timing of Osteotomy
Osteotomy works the best when it is not left to the last resort. Once the wear is too bad, the results of osteotomy are not as good. Obviously symptoms have to be present to a sufficient degree to make it seem worthwhile, but if the joint is wearing out on one side, this is the only thing that will slow the wear down.
If the joint is bad enough to be borderline for re-alignment, but not bad enough to consider replacement, then some will elect to sit it out and go directly to replacement. This is a reasonable option if function is still reasonable, and if you are old enough to consider replacement as an option.
Technique of osteotomy
The bone is cut is and then opened to create a triangular defect. This changes the alignment of the leg. In order to achieve the desired correction, the computer is used in conjunction with an alignment system. This means that 2 rods, with a tracker attached are placed in each bone (femur and tibia), and the computer then analyses the relationships between the bones, in order to determine alignment.
When the correct alignment has been achieved, a plate is applied to the outside of the bone, using a series of screws. Along with the initial cut, the plate and screws are applied with the aid of the image intensifier. This helps determine level of cut, the angle of the cut, position of plate, and the length of screws, thus making the procedure more accurate.
The procedure includes an arthroscopy to both clean up the joint and to inspect the good half of the joint.
Time to union
X-rays will be taken at 6 weeks, three months and 6 months. Full healing usually occurs between 3-6 month mark. Removal of the plate around 12 months is thought to be sensible because the bone can grow solidly into the screws. This can then make removal quite difficult. In addition to this problem, the plate and screws need to be removed in order for a knee replacement to be performed. Ideally this should be done well in advance of that replacement, thus allowing time for the bones to strengthen, and the soft tissues healing to mature.
This is a moderate sized procedure. You will be in hospital 2-3 nights depending on your level of pain and mobility. Initially the procedure is sore however multimodal analgesia will be provided. After about 2 weeks the pain is much easier to control. You will require crutches for 5-6 weeks.
By six weeks most can walk reasonably well on the leg with just a mild limp. By three months walking should be fairly easy, and there should be no limp.
The osteoarthritic pain can take some months to settle.
The knee will continue to improve out to about 12 months, when hopefully it will be much more a symptomatic. By that stage, the plate will have to be removed and the function should be good. Removing the plate is usually a day procedure and recovery quick.
Time off work
If you have a sedentary jobs should allow at least 4 weeks. If standing all day is required, then this may take 3 or more months, depending on how quickly the bone unites. When the bone does finally heal however, it does allow much more normal activity.
Prolonging the life of the knee
The knee will still slowly degenerate and therefore needs to be looked after in order to get the maximum benefit of the procedure. It is preferable to do non-impact loading type exercises, rather than activities that involve impact loading. Activities such as bike riding, swimming, rowing machines, cross trainers etc are preferred over running, power walking, stair climbing jumping etc.
Bleeding and bruising are relatively common because the bone is living, and it does bleed when cut. Despite this, significant bleeding is uncommon, even though for most people a low dose anti-coagulant is used to try and prevent DVT's from occurring. Elevation in the first week or so is very helpful to reduce this problem, but in contrast, hanging the leg down will make it bleed and swell more, thus making it sore.
Swelling is normal for this procedure. Very occasionally "fracture blisters" occur due to the amount of swelling. They do resolve with time and are not in themselves harmful.
Compartment syndrome is a complication of all tibial surgery that is uncommon but possible. It is due to excessive swelling, in the muscle compartments around the tibia. This can eventually cause the muscle to die. If this complication develops the leg may have to be opened to relieve the pressure. The wounds can be closed of skin grafted subsequently.
DVT's (deep vein thromboses) occur, but are uncommon, less than 5 %.
P.E (Pulmonary Embolism) is when a DVT goes to the lung.
Superficial infection involving the skin is not all that uncommon in tibial osteotomy, This is usually treatable by antibiotics,.
Deep infection is very uncommon, perhaps because prophylactic antibiotics are always given for these procedures. If it occurs, it can be difficult to treat, often requiring a washout and intravenous antibiotics. Rarely would the plate and screws have to be removed.
Non union of the osteotomy can occur. It is also more likely in the older patient, 55 and over. It is also more than twice as likely to occur in a smoker to a non smoker. If there is a substantial delay in union, then stimulation of the osteotomy site by graft may help. Similarly techniques such as ultrasonic stimulation may be helpful.
Loss of correction can occur, but with the current generation of plates, it is uncommon.
Screw breakage or plate failure are very uncommon. Usually these events happen because the bone in not healing, and the plate is under too much stress. For this reason, protection of the osteotomy with crutches is beneficial in the first 5-6 weeks.
Pain over the plate is common, both in the femur and the tibia. The plate is quite large and is prominent. As soon as the bone is healed therefore, it should be removed. This is relatively minor to do, and mostly can be done as a day case procedure.
Pain in the knee can persist despite the re-alignment. The arthritis is still present, even though unloaded.
Patellofemoral pain can occur if the patella is already a bit worn out.
Progression of arthritis - however should be reduced with the realignment.
Numbness on the outside of the wound used for tibial osteotomy is normal. The superficial skin nerves come across the scar area, and are cut when this procedure is done. This largely recovers over about a year, but the feeling is never quite normal. The superficial nerves do not supply any muscles however, so there is no associated weakness. Although initially bothersome, by a year most people no longer notice this.
Questions and Concerns
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