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ACL repair in children with ski injuries

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Knee ligament injuries are common in winter sports. They can range from minor injuries to the medial collateral ligament, which could require physiotherapy to speed up the recovery, to more serious issues with the anterior cruciate ligament (ACL) which might need surgery.

Mr Jonathan Bell, Consultant Orthopaedic Knee Surgeon at Wimbledon Clinics, explains how we treat ACL rupture in children…

The ACL is an important ligament in the knee that stabilises the knee during rotational activities.

After you’ve twisted your knee, it might feel like you’ve dislocated it. However, ACL rupture is actually a tear in the ligament of the knee.

This injury occurs in all age groups, and we are seeing a rise in the number of ACL ruptures in children.

At Wimbledon Clinics we look after a large number of local families whose children ski through ski race or school clubs, frequently spending many weeks in the Alps ski racing. Our success in treating children and teenagers means we get children and families coming a long distance to see us.

Historically, it was thought that ACL rupture should be treated non operatively and wait until the child grew up to treat it — but children treated this way don’t do well, particularly if they continue to play sport.

For the past 20 years I have found that early surgery gives a much better outcome and can reduce the risk of further damage to the knee that occurs in a knee left unstable. We can use a hamstring to carry out a reconstruction of the ligament — effectively replacing the torn ligament with a strip of hamstring tendon. ACL repair is being revisited in part because we now have techniques and equipment that make it possible. Another attraction is that is is a less invasive type of surgery.

What is ACL repair?

ACL repair is where we re-attach the ruptured ligament back to the bone rather than removing the ligament and replacing it with hamstring.

Why is this a good procedure?

There are two main reasons why we recommend ACL repair for children with a ruptured ligament.

Firstly, children are not fully grown and a hamstring reconstruction isn’t guaranteed to “bulk up” as the child grows, whereas we think a repaired ligament will.

In other words, the ligament will get bigger and stronger as they grow.

Secondly, the natural ligament has got a blood supply and, more importantly, nerve endings in it. The brain relies on feedback from these nerve endings found in ligaments to help control movement and to coordinate.

So it goes without saying that if you can maintain this function, known as proprioception, this is a biologically attractive option.

Who’s suitable for ACL repair?

We need to be very careful how we select children, or adults for that matter, for ACL repair.

We are looking for those in whom the cruciate ligament has pulled away cleanly from the bone but also one that hasn’t frayed too much. Otherwise the ligament won’t have a good blood supply, it’s probably going to be slightly shortened, and its nerve supply may have been damaged. Also, because the ligament is only approximately 25mm long, we can’t stretch the ligament to make it reach the bone if it’s a bit shortened.

What that means is that the only ligaments that can be repaired are those where there’s a clean pull-off from the bone, and it has to be at the top end of the ligament (known as the proximal end).

When you become very experienced after examining thousands of ACL ruptured knees, you can start to detect these proximal injuries when you examine the knee itself. Although an MRI scan may go some way to confirming that, it’s worthwhile trying to identify a proximal injury early because you really want to do the surgery in the first few weeks.

Overall, when you look at the number of people who’ve got these injuries that are compatible with repair, it’s probably as little as 15% (although it may be quite a bit higher in children).

What are the alternatives if the ligament isn’t repairable?

In those cases, we would do a standard reconstruction but modify our technique — what we do is we thread the reconstructed ligament through the core of the existing ligament rather than remove the damaged ligament, which has been shown to improve proprioception from the reconstructed knee.

But both repair and threading a reconstructed ligament up the old one are technically difficult, particularly in small knees. Deciding on whether repair is the correct operation requires experience. So you need someone who has done a lot of ACL surgery to make the decision on whether it’s the right operation, and to carry it out.

If this procedure is carried out for ligaments that are not appropriate for repair, they will almost certainly fail — resulting in a second operation.

Mr Jonathan Bell
Consultant Orthopaedic Knee Surgeon at Wimbledon Clinics

Jonathan has 20 years’ experience of treating knee injuries in children and adolescents. He has previously worked in orthopaedics at Great Ormond Street Hospital in London.

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