Ortopedia e Traumatologia

The knee is the joint between the femur and the tibia; in a normal knee, these two bones are not aligned on the same axis, rather they have an angle of about 3-6°.
A decrease (varus condition) or an increase (valgoid condition) of such angle leads to a pathologic deviation of the alignment axis and to an overloading of one joint area. Over time, such overwload leads to a degeneration of a part of the joint (arthrosis), due to wear: as a consequence, the joint will start hurting, swelling, and movement abilities will decrease. In order to avoid or slow down such degeneration, when the axis of the knee is not aligned, it is necessary to perform a corrective osteotomy (either varus or valgoid, according to which direction the correction must be take); it is necessary to surgically fracture the femur or the tibia and, through particular systems, fix the bone itself in a more correct position that can ensure a good alignment of the joint.

This is why osteotomy is performed with the aim of preventing arthrosis or slow down its degeneration process where already existing.

There are various techniques that can be used to change the axis of the knee after the osteotomy:
- the removal of a bone wedge (the aim of the osteotomy is to "remove");
- the fixing of a bone wedge (the aim of the osteotomy is to "add");
- progressive alignment of the axis after a semicircular osteotomy;
- progressive alignment of the axis after a horizontal osteotomy.

If the first two techniques are used, then it is necessary to stabilise the alignment achieved with internal fixation devices (metal clamps, screws and plates, blade-clamps); if the other two techniques are used, then the stabilisation of the bone must be done with external fixation devices, that is long screws (fiches) that come out of the leg skin and that are connected to each other through an external metal bar (body of the fixation device): the days after the operation, by gradually moving the screws of the body of the fixation device, a gradual change of the axis of the knee is obtained, until the expected correction is finally achieved. The external fixation device is left in place until the osteotomy has finally consolidated.

The advantages linked to the use of internal fastening devices are the following:
- immediate and definitive fixation of the osteotomy;
- no metal fixation devices coming out of the skin;
- the patient does not need to make any adjustments to the fastening device.
However, it also has some disadvantages:
- the presence of a permanent internal fastening device that over the years might need to be removed with new surgery;
- when undergoing surgery, it is absolutely necessary to establish the exact degree of the correction since, in the future, such system has no way to change the achieved axis;
- after the operation, it is necessary to immobilise the knee (most of the times, an orthopaedic knee brace for a few weeks may be sufficient);
- during the first 6-8 weeks, the patient cannot carry the whole body weight while walking; longer rehabilitation times for movements and muscular tone.

CORRECTIVE TIBIAL OSTEOTOMY

The use of external fixation devices instead has the following advantages:
- the progressive modification of the axis of the knee that can be monitored at sight and through X-rays. Therefore, it can be stopped when such modification is considered to be sufficient;
- after the operation, there is no need to immobilise the knee;
- very fast rehabilitation of movement and the consequent maintenance of a good muscular tone;
- the patient can immediately walk and carry his/her body weight on both legs.

The disadvantages such technique has are the following:
- it cannot be performed if the bone is affected by osteoporosis;
- the external fixation device is cumbersome and has to remain in place for about three months;
- the fixation device needs to be completely removed when the osteotomy has finally healed (the removal is carried out with no anaesthesia and with out-patients assistance);
- the patient must have an active role in the healing process, especially as for the gradual modification of the axis: after leaving the hospital, the patient will need to continue the gradual modification by acting on the screw of the body of the fastening device, in line with the directions received;
- for the whole time the fastening device is kept in place, the fiches need to be medicated in order to avoid potential infections.
For all these reasons, osteotomy with an external fixation device is usually performed only on young and very cooperative patients.

OSTEOTOMY'S POSSIBLE COMPLICATIONS

1 . UNSATISFACTORY DEGREE OF MODIFICATION: it can be gradually modified if the external fixation device was used before the osteotomy had completely healed;
if an internal fixation device was used, then further surgery is needed. However, it is a very rare complication.

2 . PARTIAL LOSS OF THE MOVEMENT OF THE KNEE: being this an extra-joint operation, such loss is a very rare complication and movement rehabilitation is generally complete, regardless of the technique used..

3 . INFECTION OF THE FIXATION DEVICES: if an internal fixation device was used, such infection is a very rare complication; in the first few weeks, it is treated with a full-dose antibiotic therapy. Later, if the infection continues, it might be necessary to remove the osteosynthesis and wash the site of infection. If an external fastening device was used, the infection usually concerns the implant of one or two fiches: generally, medications, local washings and antibiotics are enough to stop the degeneration of the infection; if this does not happen, then the fiches must be surgically removed and replaced.

4 . THROMBO-PHLEBITIS OF THE LEG: it indicates the inflammation of the veins of the operated leg (seldom the other one) which is revealed by a large swelling of the foot and of the leg itself, a strong sense of heaviness of the limb and calf pain. In order to decrease the occurrence of such complication, it is necessary to carefully follow the heparin therapy recommended when discharged from the hospital, to avoid standing still for a long time, to start the rehabilitation therapy as soon as possible and follow it consistently.

5 . PULMONAR EMBOLISM: : it indicates the detachment of a thrombus that has developed in one of the veins as a consequence of the previously described complication. The thrombus reaches the lungs and causes chest pain, difficulties in breathing, cough, sometimes bronchial catarrh containing a little bit of blood. This is a dreadful and very dangerous complication that requires immediate hospitalisation in an internal medicine ward. In order to prevent such complication from arising, the same preventive measures for complication n° 4 need to be followed.