Currently if someone tears their ACL the vast majority of patients don’t cope particularly well. To allow them to get back to good levels of activity an ACL reconstruction is usually recommended. This is also advised to minimise the risk of secondary damage when giving way occurs in an ACL deficient knee.
It’s that instability and “pivoting“ of the bones that causes the secondary damage. Currently we would advocate, in symptomatic patients, surgical reconstruction of the ACL to minimise this instability. This would therefore allow patients to return to sporting activity and reduce meniscal and joint surface damage.
ACL Reconstruction
Reconstruction involves removing the existing tissue - or most of it - so that the surgeons can see what they’re doing. Then they take tissue either from the patient – called an autograft (most commonly hamstrings or patellar tendon taken from the patients own knee) or donated human tendon tissue from another individual - called an allograft, and they use this graft to make a new ACL.
That graft is placed via tunnels which are made in the tibia (or shin bone) and femur (or thigh bone). Traditionally surgeons make a complete tunnel in the tibia. In the femur it is more often a socket with a pilot hole above it so that the graft can be pulled from below into the socket, locked in place and fixed with some form of fixation. This could be either a screw or a suspensory fixation on the femur, and - most commonly in the UK - a screw on the tibia. Alternatively, if one is a believer in all-inside ACL surgery, a suspensory fixation will also be employed on the tibia.
So the current treatment is to cut away all the ACL tissue or most of it, so you can see what you’re doing, and put a new ACL in place - and that's what an ACL reconstruction is. This is a good operation, and it’s stood the test of time, but sadly it’s not giving the results that surgeons would like. The literature and previous experience tells us that sadly only 61% of patients will get back to the same level of activity afterwards. Often the knee doesn’t feel quite right following an ACL reconstruction; it’s much better and it feels stable but it often just doesn’t feel normal.
Another problem is that a reconstruction like this takes a long time to heal. We always assume that by a year patients can get back to twisting sports, but often it can take a lot longer than that for the graft to fully heal. If the patient is unlucky and has a further twisting injury, the new ACL may become re-torn and the patient then has to undergo a revision procedure.
Graft failure and revision
The overall failure rate for ACL reconstruction is quoted at being approximately 5%. That’s all-comers – but if you take the young active patients - the paediatric group and those under the age of 25 who are engaging in pivoting sports - the failure rate is as high as 30% in some series that have been quoted. Certainly it is much higher than 5% and probably on average 15%, but rising to 30% in the very young group.
So, one of the problems that we have with ACL reconstruction is that the initial tunnels that we’ve drilled often have to be revisited for an ACL revision procedure. If these are well positioned they need to be expanded and enlarged. If not, new tunnels may need to be made such that a new ACL can be re-implanted.
ACL Repair & Internal Bracing
So what about ACL 'repair' rather than 'reconstruction'?
Repair was attempted many times in the late ‘70s and early ‘80s. John Feigan - one of the fathers of sports medicine and arthroscopic surgery - attempted it on a big number of military recruits in the United States. He did a large study and showed in the late ‘70s that one third healed very well but two thirds did not. So the procedure was abandoned. However when you look again at the ones that did well generally speaking, it was those ACLs that had torn from the attachment on the side of the femur. Certainly that was one of the predictors of a good outcome. He was at that time doing the surgery through an open technique with relatively poor visualisation, using primitive tools and fairly weak suture material, and we’ve moved on a lot since then.
Repair was attempted again by Werner Müller, another father of arthroscopic and sports knee surgery, in the ‘80s. He had a similar experience - some did well but some did badly. As ACL reconstruction techniques and instruments improved, it was felt that the way forward was not via repair of the native ligament but by its replacement with a new one.
Arthroscopic surgery has developed enormously in the last 10 years. Telescopes and cameras are all significantly advanced, and we have an array of new instruments that better allow us to manipulate tissue. These have come a lot from our shoulder colleagues passing sutures and passing material through ligaments and tendons. Very strong suture material and tapes are now available that have only been on the market for the last 5-10 years. So as a result of better visualisation, better equipment and new fixation devices and sutures, orthopaedic surgeons are revisiting the possibility of carrying out ACL repair - and with considerable success.
Professor Gordon Mackay from Glasgow came up with the concept of an internal brace which, like an external brace, holds a joint in the correct position allowing mobilisation in a controlled fashion. The internal brace employed is a loop of FibreTape, which is a 2mm polyethylene tape. Over a million of these have been used in the last 10-12 years very safely, and we know this mainly from shoulder surgery. So using it in the knee was an easy jump for both Gordon Mackay and for me.
We moved over to using FibreTape for augmenting or reinforcing, for making small grafts stronger, or in a revision situation using this tape to carry out a direct repair, as well as using the tape as an internal brace. In 5 years of co-operation our ideas really gathered a lot of momentum. We are very excited about how well it seems to be doing in own own hands, and also in the hands of many other surgeons around the globe. What’s interesting is that, when we run cadaveric courses, this procedure is very high on the desire list of surgeons coming through to learn new techniques. Surgeons want to be shown this procedure - they believe in it and they want to attempt to carry it out for their own patients because they feel that it makes a lot of sense.
Our combined outcomes show our ACL repair patients had only a 5% failure rate. Gordon has essentially only done these repairs in adults, while I have done them in adults and children. We are very pleased with the fact that our revision rate (or failure rate) is the same as it is for the primary ACL reconstructions and that’s got to be a good thing.
In addition the repair offers the advantages of retaining some of the nerve tissue inside the ACL remnant, which helps retain proprioception (or position sense). Also there is less of a problem with any donor site if there is no need to harvest hamstrings.
We have assessed our patients with the objective and subjective scoring tests that we have available, and found that they are doing as well as - and often better than - the standard reconstructions.
