Children's ACL injuries — Sports Healing

Anterior cruciate ligament injuries in children and adolescence.

Why is paediatric ACL injury becoming more common?

ACL injuries in children are becoming increasingly common. Although the cause of this is not confirmed, it is likely that children are playing more competitive sports more frequently, many adolescents are also much bigger in height and frame than they were 20 years ago, and injuries are being diagnosed more frequently because MRI scans are readily available.

What is the mechanism of paediatric ACL injury?

Most paediatric anterior cruciate ligament injuries occur as the result of a noncontact twisting injury. This can occur in twisting sports such as soccer, netball, skiing, lacrosse, basketball.

As with adults, the shin bone moves out of position relative to the thigh bone, the so-called pivot type injury.

Can other structures be injured as well as the ACL?

The most common structures that are involved that are injured in conjunction with the ACL are the medial collateral ligament, meniscal cartilages, and sometimes bruising occurs on the bones of the femur and tibia, the so-called pivot bone bruise or impaction fracture.

How do we diagnose paediatric ACL injuries?

As with adults, diagnosis depends on a thorough history of the accident, and examination of the knee, particularly when it is less sore or swollen.

Is an MRI scan necessary?

It is becoming increasingly clear that any child who has a swollen knee as the result of an injury should have an MRI scan to determine which structure has been damaged. ACL injuries are most commonly confirmed by MRI scanning.

What do you see on MRI scan?

Reading MRI scans is a complex process.

The scan effectively slices the knee in three different directions. We look for differences in greyness in the structures. This is known as signal. A white or light grey area is known as high signal (on “fat saturated”images).

ACL injuries show high signal in the substance of the ACL or where the ACL attaches to the femur or tibia.

Can children's ACL injuries be managed without surgery?

Whilst it is possible to manage paediatric ACL injuries without surgery, long-term studies have shown better results with ACL reconstruction. In particular, reconstruction of the ACL leads to a more stable knee and prevent further damage to the meniscal cartilages.

The British knee Society, therefore recommends that all paediatric anterior cruciate ligament injuries are treated by a surgeon that is appropriately qualified and experienced in management. Early surgery and reconstruction should be considered.

What does a paediatric ACL reconstruction involve?

The operation involves taking tendon from another part of the knee and transplanting this where the damaged cruciate ligament is situated in order to replace this ligament. This is known as autograft anterior cruciate ligament reconstruction.

Which donor site can be used?

The most commonly used tendon is the hamstring tendon on the inner aspect of the thigh and knee. These tendons are the gracilis and semitendinosus tendons. Other tendon grafts include the quadriceps tendon.

If the teenager is fully grown with no growth left, patella tendon can be used.

How do you replace the damaged ACL?

There are many different techniques to plug the new graft into the bone.

Most commonly, tunnels are drilled in the shin bone and the thigh bone. The graft is then passed through the tunnels.

The graft then may be fixed in the thigh bone and the shin bone with some form of suspensory button or Screw fixation.

How do you decide which type of ACL reconstruction in child?

There are many factors that decide this:

Age and skeletal maturity. Below the age of 11 years it is best not to disturb the growth plates of the bone and there are certain techniques that are used known as extra physeal ACL reconstruction.
Between 11 and 14 years, different surgeons use different techniques. Mr Gupté uses a trans-physeal, (physeal respecting) technique involving minimal damage to the growth plates and several precautions being taken to avoid growth plate injury.
Between the ages of 15 and 18 in girls and 16 and 18 in boys, an adult type ACL reconstruction can be considered if the growth plates are determined to be fully closed.

What happens after surgery?

Most commonly needs placed in a brace and crutches are required for between four and six weeks after surgery. We then follow a five stage rehabilitation protocol as detailed in the attached PDF in the patient resources section of this website.

What is the success and rerupture rate after ACL reconstruction?

This really depends on the nature and age of the injury as well as whether the patient has hyperlax or elastic joints.

The quoted failure rate of ACL reconstruction in under 18s is between seven and 15% at five years.

This does however mean that 85% of children will have a good result with a stable knee that allows a return to sport.

The failure rate is likely to be higher in children than adults because children have an inherent elasticity to their tendons which make them more prone to be rupture.

In children and adolescents, bone growth probably leads to more stress on the newly transplanted tendon and this can predispose to rupture later on.

There are many techniques thought to improve success rate after ACL reconstruction children.

These include:

Using a thicker tendon graft
fixing the graft on the bone with more secure methods.
Performing a supplementary operation known as a lateral extra-articular tenodesis. This effectively gives a second anterior cruciate reinforcement on the outside of the knee. Although this does involve an extra scar biomechanical studies show that these knees are probably stronger especially in hyper lax patients.

The best knee surgeons in children’s and adolescent knee surgery will take into account the needs of the individual child, the nature of the injury, the biology of the knee and the child's body, and psychology. They will thn employ the most biomechanically sound techniques with a good evidence base that minimises the risk of complications and maximises the chances of a successful result.