Information about Key hole surgery for correction of knock knees
This operation has been invented and almost exclusively practiced by the author. We have experience of having performed this operation on more than 90 patients, with minimum side effects.
Knock knee is a deformity where the knees collide with each other. Moderate knock knees are normal in growing children up to 8 years of age. Whatever deformity is left after that, usually does not correct by itself. It is conventional to wait and watch for possible spontaneous resolution of the deformity till the age of 12 years. In some cases, the deformity is severe enough even at 8 years, and has potential to damage knee ligaments, and hence surgical correction even at early age is desirable.
There are three methods in vogue for correcting knock knees surgically (see table for comparison):
1. Growth modulation: This is a technique where the growth centre of the lower end of the thigh bone is so regulated that one side (medial side) is forced to stop growing for some time by stopping its growth by using a clamp across the growth plate. Over a period of time (usually a year or two), the outer side continues to grow and equalises the growth on two sides. This leads to correction of deformity. This is done by surgery which involves putting some implant (staples or plate) across the growing part. The same is removed once the growth is compensated. In a way the growth of the limb is modulated, hence the name.
The major side effect of this surgery is that at least two operations are required. It can only be done if sufficient growth potential is left (10 to 14 years of age). It takes time for the correction to show up, and there is a certain amount of uncertainty about over and under correction. Incision of approximately 2 inches is required. Good part is that no plaster or bone cutting is required, and the child can be pursuing his normal activity all through.
2. Corrective osteotomy: This is an age-old technique of open surgery, where the bone cut at the lower end of the thigh bone, and is realigned. It needs and incision of approximately 3 to 4 inches, and usually some kind of internal fixation device (plate) is used to keep the bones in corrected position.
The major side effect is a big scar. Once fixed, no possibility of fine-tuning the correction. Plate removal is usually required, and hence another surgery. Other side effects are those associated with any surgery around a joint - stiffness, non union and delayed union, malunion. It does need rest for 6 to 8 weeks for recovery. Benefit is that it’s done under vision, and hence a fairly safe and reproducible operation in average hands.
3. Key hole surgery: This technique has been devised by the author, considering two main disadvantages of above conventional methods: (a) two operations are mandatory, one for putting the implant and one for removing; (b) cosmetically unacceptable scar; (c) takes long follow up in first method, and other possible complications.
In this technique, through a 1 cm cut, the bone is weakened from within at the strategic spot with a tool called osteotome. Once the bone is sufficiently weakened it is cracked using force, akin to breaking a soft branch of a plant. The same can be now brought to corrected position and held there with the help of plaster of Paris for 3 to 4 weeks. The place of weakening and correction to be achieved is monitored using a video x ray machine (called C-arm) in the operation theatre. Once the surgeon is satisfied with the correction, a well-fitting plaster is applied from groin to just above the ankle. If the correction, by any chance, is not up to the mark, the same can be corrected simply by cutting open the plaster, correcting appropriately, and putting another plaster. Since there is no foreign implant used inside the body, there is no need for removal. The bone is held in corrected position ‘internally’ by a thin, tough tissue envelop covering the bone – called periosteum. Externally it is held in position by plaster. The position of the bones are monitored with x rays after 2 weeks and 4 weeks (done at home with portable x-rays machine).
The main side effect of this technique is need of plaster for 3 to 4 weeks and a further period of 3-4 weeks of not being able to put the leg on the ground (and hence need for walking with crutches or walker). This is particularly so in patients undergoing correction on both knees at the same time as they will have to be in bed for 3 to 6 weeks. There is need for physiotherapy for a period of 6 weeks after removal of the plaster. It takes 2 to 3 months for the patient to walk again on the operated legs. In less than 5 % cases the position of the bones may move inside the plaster, and may need putting the plaster again under anaesthesia or even formal open surgery as in option 2. Rarely the knee gets stiff more than expected, and manipulation under anaesthesia (no surgery) is required.
Since it is a key-hole technique and a lot depends upon the skills of the surgeon. There is a potential to damage the neuro-vascular structure of the limb, a serious complication which may need urgent surgical repair of the damaged vessel. In author’s experience this has happened only one time out of 70 cases. The said child underwent repair and became okay. It is this last reason for which the author has not promoted this technique for use by others. But, in the background of all the other benefits as mentioned above, in author’s hand it continues to be a popular option, particularly for young girls who do not want to exchange deformity with unsightly scar.
Comparison between different techniques of correction of Knock Knees
|Technique||Operations||Metal plate used||Scar||Time taken to correct||Bed rest||Crutch walking||Complications|
|Growth modulation||2 times||Yes||3-4 cm||1-2 years||Nil||Nil||Uncertaininty, Only possible between 12 to 14 yrs of age.|
|Osteotomy and fixation||2 times||Yes||10-15 cm||immediate||10 days||Total 3 month||Malunion, non union, stiff knee|
|Key-hole correction||1 time||No||1 cm||immediate||4 weeks||4 weeks after bed rest, total 3 months||5% repeat surgery, 1 % complications: vascular injury and its surgery, stiff knee needing manipulation|
The usual procedure is as follows:
- Some special x rays are carried out in the hospital.
- You are admitted on the morning of the operation. The operation is carried out sometimes during the day. It is done under general anaesthesia, and takes about 45 minutes for both sides.
- Immediately after the operation your legs would be in plater cast from groin to ankle. A check x ray will be done to record that position of the bones are okay.
- You will be required to be in the hospital for 48 hours, after which you will be discharged. You will be required to be in bed (absolute bed rest including daily chores) for 6 to 8 weeks. This is the most taxing part of this otherwise wonderful treatment method.
- One can travel by car, ambulence, train or by air, with proper arrangements. For outstation patients within India, this is possible to go home stright from the hospital, but for out of country patients, it is desirable that they stay in Delhi for 10 days post surgery. We will help in getting suitable accomodation. Distant outstation patients and those from abroad would be permitted to travel after 10 days, once day-10 post op check x ray is satisfactory.
- The bone position may shift within the first 10 days (1/20 cases) and a change in plaster may be required under anaesthesia and short admission. The chances of the bones shifting position after 10 days is rare, but monitoring with x rays every 10 days is required for first one month (day 10, day 20 and day 30).
- The plaster is kept for a period from total of 4 to 6 weeks (depending upon age). No stitch removal is required as its only a small (1 cm) cut. After removal of plaster, the patient will still be in bed for another 2 weeks, but will be permitted to move the knee, but not walk.
- After 8 weeks, the patient will be trained to walk with support of a walker/crutches, under guidence of a physiotherapist. The support will be used till healing occurs, usually 3 months from operation. It may take a few more weeks to get the knee to proper bending position. It may take another few weeks to feel fit.
- In an exceptional situation, if the position of bones shifts and is not in acceptable limits, open surgery and fixation with plates and screws may become necessary (1/100). This is a proper open surgery with 6 inches cut, and additional cost (nearly double that of the first operation).
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