Proximal ACL Avulsion Injuries

Written By Mandy Gilchrist

Why some ACL tears may heal or be repaired

Not all ACL tears are the same. A proximal ACL avulsion occurs close to the ligament’s femoral attachment and has favourable healing features.

Compared to mid-substance tears, a proximal ACL injury may:

  • Heal without surgery, more on this below

  • Be suitable for surgical repair, thereby avoiding the need for ACL reconstruction

Sherman classification

The Sherman classification describes ACL tears according to their location. Type 1 and Type 2 tears occur close to the femoral attachment and generally have the greatest potential for healing or repair.

An ACL can heal but remain loose

A proximal ACL tear may heal close to its normal position. In other cases, it heals in a more anterior and vertical position within the notch, or it may heal to nearby PCL fibres well away from its original attachment.

MRI may show continuous or apparently healed ACL fibres as a result, while the ligament remains functionally loose. Patients may continue to experience giving way, difficulty pivoting and reduced confidence in the knee.

For this reason, ACL function cannot be determined by MRI alone. Clinical assessment of knee stability remains essential.

Our results

We have analysed our own results. Over the past two years, 76 patients underwent ACL repair after an average of 90 days of unsuccessful non-operative treatment.

In 42% of cases, the MRI report described the ACL as normal, intact or healed. Despite this, clinical examination demonstrated persistent laxity and the patients remained functionally unstable.

MRI was most accurate when performed within two weeks of injury, correctly identifying the ACL tear in 87.5% of patients. Accuracy reduced when imaging was delayed, likely because the ligament had begun to scar or heal in a non-anatomical position.

Take-home message

  • Early MRI is important when an ACL injury is suspected

  • Clinical assessment is the key to manage ACL injuries, with MRI as an adjunct

  • ACL repair is possible in proximal ACL avulsions

  • Some proximal ACL avulsions may heal in reasonable position without surgery

 

Mandy Gilchrist
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