ACL reconstruction in children
Pre-Operation
Many children are involved in high demand competitive twisting and pivoting activities, including all the codes of football as well as netball, ultimate frisbee, touch football and skiing, in particular.
The mechanism of injury, is similar to that in an adult, but children can sometimes pull the ligament off the bone attachment, with or without a fragment of bone. It is important not to miss this diagnosis, and such injuries can sometimes be repaired, with a much shorter recovery than having to under a reconstructive procedure similar to that usually performed adults.
The child often describes a collapse injury to the knee, with immediate pain, often a sense of instability and movement within the knee, with swelling becoming apparent within an hour of the injury in most cases. Swelling in a child’s knee following injury, is generally a significant injury and warrants early review by a sports physiotherapist, sports doctor or orthopaedic surgeon.
Many of these injuries occur over the weekend and presentation to an A&E department common. Even if the definitive treatment cannot be organised, the patient does require x-rays of the knee, and referral to a sports orthopaedic surgeon.
The x-ray may demonstrate an avulsion fracture (attachment pulled off the tibia) which is important not to miss, as there is the opportunity to repair this injury and “save the ligament”.
Prompt review by an orthopaedic surgery with expertise in the management of ACL injuries is advised.
The child will be examined and may require an MRI of their knee. The MRI may confirm the tear of the ACL and the presence of meniscal tears or chondral damage, but they are not 100% accurate and may not be required in some cases.
Operation
If the ACL is pulled off the attachment to the top of the leg bone (tibial plateau), a sports orthopaedic surgeon will repair the ligament. This can often be done arthroscopically (key hole surgery) thus preserving the child’s native ACL and resulting in a significantly quicker recovery, with a more predictable outcome.
If the ACL is torn in the middle of the knee (“mid-substance”), then it usually requires a reconstruction, similar to that performed in adults. A new ACL has to be made using a graft. The graft may be one of the child’s own hamstrings, but this has a 50% failure rate prior to the child reaching adulthood, at least partially due to the size and strength of the juvenile hamstring it is believed. Other options are to use cadaveric donor graft (usually a frozen graft, and possibly irradiated to sterilise). However, Dr. Porter’s preference is to use a live allograft donor (that is, usually one of the parents donate a hamstring graft). As long as there are no medical reasons to use the parent, and appropriate blood tests are check, this is a safe and effective technique, with a failure rate closer to 2% per year.
The donor (parent) is usually asleep in an adjacent theatre, so that the harvested graft can be quickly inserted into the patient to reconstruct the torn ACL.
Another concern is the risk of causing growth disturbance as a result of drilling tunnels in the child’s bones and fixing the graft. As long as the surgeon only disturbs a small percentage of the surface area of the growth plate, which is possible with careful technique and image control, and there is no rigid fixation crossing the growth plate, there should be no growth disturbance.
Dr. Porter positions the tunnels similar to the positions used for an adult, but positions the screws (which are not metal but turn to bone) so that they do not cross the growth plate. In this manner the child’s growth is not affected.