Part 3: The Exact Location of the Injury - & the role of an 'internal brace'

Brief overview...main content below...

The Exact Location of the Injury & the role of an internal brace

With the patient asleep and relaxed, the pivot shift, Lachman and anterior drawer can be subjectively repeated and the laxity clinically confirmed and compared with the normal side.

Attempts may be made also to objectively record the laxity. The KT-2000 is just too bulky for the knee in small children. A better option is the KIRA (below) - which is app-based.

Prior to any definitive decisions regarding the surgery, an arthroscopy is performed through anteromedial (AM) and anterolateral (AL) portals. The surgeon assesses:

  • the integrity of the menisci
  • the cartilage joint surfaces
  • the femoral attachment site
  • the tibial attachment site
  • the integrity of the central portion of the ACL
  • the integrity of the PCL

The surgical management will depend upon the nature of the injury.

Proximal Detachment (when femoral end is detached)

The proximal tears are the ones that lend themselves most readily to repair, and the procedure is straightforward.

The technique involves lassoing the free end of the ACL and pulling it back onto its original footprint on the femur via a tunnel or socket drilled in the femur, where is it fixed with a fixation device.

Should the surgeon decide that the ligament is too flimsy and vulnerable on its own, it may be supported by an 'internal brace' of a braided polyethylene, which can be removed after a few months. Such an internal brace would involve the need to drill a second tunnel in the tibia so that the brace can be securely fixed on both ends, usually with a button and suspensory ligament which are removed at the time that the polyethylene itself is removed.​

If we can carry out a repair we can do so with very small tunnels - just 3 mm or less to pass sutures. It’s not burning any bridges - you are using the patients existing tissue. You are not harvesting tissue and therefore causing further secondary damage which is what we have to do with a conventional reconstruction. Patients rehab much quicker because of the quick healing process and the minimally invasive surgery that is carried out. With objective and subjective assessment if all is going well they can return to full activity at 3-4 months, which is completely different to how careful we need to be following a traditional reconstruction.

Mid-substance Tear (when the ligament itself is torn)

For the mid-substance injuries, depending on the quality of the tissue, it may still be possible to retension and do a standard repair technique with the internal brace. However, if the tissue is poor quality then the surgeon can change to a hybrid graft and run alongside some tissue - usually the semi-tendinosis - as a biological internal brace. Parental allograft is another alternative for a hybrid graft, that is using the native ACL as a repair and living parental allograft as an augmentation. There is no tissue typing or matching needed for such an allograft - it's avascular (has no blood supply) and has no immune potential. So in reality the ACL graft can be 'anyone-to-anyone', unlike blood transfusions or an organ transplant.

Distal Avulsion (when the tibial end is detached)

When the injury occurs at the tibial end of the ACL it is usually associated with a bony fracture or avulsion. We would call it an 'insertional injury' (because it is at the ligament's insertion, rather than its origin on the femur). This type of injury associated with a bony avulsion is called a 'Mckiever', and these injuries have their own classification - type I, II and III depending on the amount of displacement.

If a patient presents with a Mckiever injury, in other words with a bony avulsion, historically the patient would have been put into a plaster in full extension, and the avulsed fragment would have been allowed to “gum up”. These days really have gone and anyone doing that is doing historical treatment. Modern treatment is to do an arthroscopic procedure - to actually go into the knee, debride (or clean up) the footprint where the avulsed fragment has come from, remove any clot, and reduce the fracture, taking the avulsed fragment and putting it back perfectly like a piece of a jigsaw puzzle. Once the surgeon is happy that good reduction has been achieved, then two drill holes are made outside of it up through the tibia using a jig, and sutures are passed around that bony fragment and back down the second tunnel. It is effectively lashed back down onto the tibia and tied over a button or some form of fixation device for the sutures on the tibia.

So if any of you are being told that a good form of treatment is to allow that bony fragment just to sort of heal by itself that is not what is currently felt to be best practice, and will almost 100% end up with a lax knee that will require further treatment in the future.

Further Reading

Knee Surg Sports Traumatol Arthrosc. 2016 Jun;24(6):1845-51. doi: 10.1007/s00167-016-4150-x. Epub 2016 May 3.Paediatric ACL repair reinforced with temporary internal bracing.Smith JO1,2, Yasen SK1,2, Palmer HC1,2, Lord BR1,2, Britton EM1,2, Wilson AJ3,4.

Additional Resources (Click to view)

Arthrex cadaveric demonstration by Greg DeFelice helps you to understand the instrumentation for a repair when the ACL is torn from the wall of the femur. This is an adult, but the process is comparable.

Internal Bracing Reinforcement


Here are answers to some frequently asked questions:

Don't you get synovitis from the tape?

What are the indications for internal bracing?

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