The term Osteotomy, in practice, refers to reshaping a bone. When the pelvic side of the socket is repaired, it is called “pelvic osteotomy”. There are several different types of pelvic osteotomy and the choice depends on the shape of the socket and the surgeon’s experience. When the upper end of the thigh bone is re-shaped, this is called “femoral osteotomy”.
Each of these procedures may be done alone, in combination, or together with a reduction. Children older than 2 years almost always need all three procedures to make the hip stable and return it to a more normal shape.
An arthrogram (x-ray dye injected into the hip joint) at the beginning of the surgery can help the surgeon decide exactly what needs to be corrected. Whether one or all three procedures are performed, the recovery time is about the same.
The child is usually in the hospital for 2 or 3 nights and in a body cast for 6-8 weeks. That is generally followed by bracing full-time or part-time for another 6-12 weeks.
For some osteotomy procedures, pins and plates are used. They are removed after the bone is healed. That may range from eight weeks for the pelvis to one year for the femur. Typically, they can be removed after a few months, but up to three years after surgery.
Some examples of pelvic osteotomy surgeries used to treat hip dysplasia in young children are the Dega osteotomy and Salter (Innominate) osteotomy.
Salter (Innominate) Osteotomy
Bones in young children can bend for this to happen and then they remodel after the socket is stable. This does not interfere with the size of the pelvis later in life. In these cases, the socket is round and may even be smaller than the femoral head, but the socket hasn’t developed properly and needs to be shifted so it can support the hip better.
This type of abnormal shape of the socket may be more common when the hip has never been in the socket and hasn’t rubbed on the edge of the socket.
Femoral osteotomy is done when the upper end of the thigh bone needs to be tipped so the ball points deeper into the socket. This is sometimes called a Varus De-rotational Osteotomy (VDO or VDRO). The thigh bone often needs to be shortened when the hip is dislocated high above the socket. This allows the ball to be lowered down to the level of the socket without stretching the entire leg and all the soft tissues like muscles and nerves.
When there is a high dislocation and this isn’t done, then there may be increased risk of redislocation and increased risk of damage to the growth of the hip. Surprisingly, shortening the bone actually stimulates growth of the leg so the shortening is almost always temporary as long as the hip stays in the joint and does not develop growth disturbance from AVN.
Varus osteotomy of the femur
This is a more common procedure in children older than 18 months. One advantage of the bigger procedure is that all the elements of hip dysplasia are corrected surgically so that the time in the cast is actually less than waiting for natural growth to help restore the joint to normal. However, the bigger procedure itself should not be the first choice when less invasive methods might work as well in the long run.