Leg axis malalignment and realignment osteotomy
What is meant by leg axis malalignment?
One speaks of a straight mechanical leg axis when one draws a line from the centre of the femoral head to the centre of the ankle joint and this line runs through the centre of the knee joint. If the line deviates inwards from the centre of the knee joint, a bow leg (varus malalignment) is present; if it deviates outwards, a knock-kneed leg (valgus malalignment) is present. Leg axis malalignments can either be congenital, acquired through various diseases or caused by injuries (post-traumatic).
The malalignment of the leg axis leads to an uneven distribution of the load in the knee joint. With the bow leg, the overload affects the inside of the knee joint, with the knock-kneed leg it affects the outside. Over time, the overload leads to increased wear of the meniscus, to cartilage damage and subsequently to osteoarthritis.
Symptoms of leg axis malalignment
Leg axis malalignments usually first manifest themselves through pain caused by consequential damage from the incorrect loading. The pain usually begins insidiously and is localised in the overloaded knee joint area.
Diagnosis of leg axis malalignment
In the case of severe leg axis malalignments, these can already be seen with the naked eye during the clinical examination. An x-ray examination (whole leg x-ray in standing position) serves to precisely measure the existing deformity. These images can also be used to determine whether the deformity is mainly in the femur or the tibia. This has an important influence on the surgical technique of leg axis correction.
Therapy for leg axis malalignment
In order to prevent consequential damage due to overloading, a leg axis correction should be carried out. If the leg axis malalignment is not very pronounced, a conservative (non-surgical) therapy with leg axis training can be carried out. If the leg axis malalignment is more pronounced, a surgical leg axis correction (osteotomy) is necessary.
The exact planning of the leg axis correction is done with the help of whole leg X-rays. By measuring different angles, it is determined whether the realignment osteotomy must be performed in the thigh bone (femur) or in the shin bone (tibia) and by how many degrees the correction must be made. During the realignment osteotomy, the bone is then cut almost completely with a saw, brought into the correct position according to the planning and fixed in this position with a plate and screws. A distinction is made between an open wedge technique, in which a gap is created in the bone by opening it, and a closing wedge technique, in which a bony wedge is removed from the bone. Which of the two techniques is best to use must be decided individually based on the planning.
Follow-up treatment for an realignment osteotomy
Mobilisation and exercise therapy can begin immediately after the surgery. Partial weight-bearing of the operated leg with the help of forearm crutches is necessary for a few weeks.