Anterior Cruciate Ligament (ACL) Repair is Making a Comeback!

May 2, 2018 / Nev Davies

It’s funny how surgical treatments in medicine sometimes tend to turn full circle. This blog explains all about ACL repair, in contrast to ACL reconstruction, as an option to treat ACL injuries surgically. I think it offers a really good solution for some younger patients with particular types of ACL injuries. It’s important to understand however, that not all patterns of ACL injury are the same and certain criteria have to be met before I would recommend an ACL repair.


What is the ACL?

The ACL is one if the main structural ligaments inside the knee that controls the stability of the knee, particularly in pivoting and side-stepping movements – i.e. playing sports such as football, rugby, netball, as well as in dance and ballet. It also has important receptors (proprioceptors), within its tissue, that gives clever, involuntary feedback to the brain and hence help the muscles control the knee. It runs from the top of the notch in the femur (thigh bone), inwards and downwards to the front of the plateaux of the tibia (shin bone) (see picture 1).


What happens when the ACL is damaged?

Unfortunately, because more and more youngsters are involved in sports, ACL injuries are on the increase and as a knee specialist I see lots of these ruptures in all ages, but particularly those under 20 years old. Typically, but not always, the injury occurs in a non-contact situation where the foot is planted on the ground and the knee, which is slightly bent twists and ‘gives’ (see Picture 2a). A pop or click is sometimes heard or felt and usually the knee swells fairly swiftly, as the ligament bleeds into the knee joint. Sometimes other structures can be damaged at the same time, including the menisci (shock absorbing cartilages) or the joint surfaces themselves.


How is ACL injury diagnosed?

Most knee consultants and specialist physios will be able to diagnose an ACL injury with good clinical skills (taking a history and examining the knee), however with most acute knee injuries we obtain an MRI scan (see picture 3a and 3b) to confirm the diagnosis and look for those other injuries.


Types of ACL injury

There are 3 main types or patterns of ACL injury

Proximal detachment

Firstly the ligament can be pulled off or detached from its footprint at the notch of the femur which means the remnant can flap around – sometimes this can gum up and stick down to the posterior cruciate ligament (PCL) which lies just behind.

Intrasubstance rupture

Second is an intrasubstance rupture, where the ligament fails in its mid portion. It’s a bit like strands of spaghetti being pulled apart.

Bony avulsion fracture of tibial eminence / spine

Third is a bony avulsion (pull off) of the inferior attachment at the tibial plateaux – this tends to be more common in young people, as in skeletally immature patients this bony insertion point is a weaker structure than the ligament itself.

History of ACL Repair

In the late 1970s and early 1980s some of the pioneers of ligament surgery started off by trying to repair these ruptured ACLs by essentially stitching them back together. Patients stayed in hospital for a week after surgery, and were often in full leg plasters for up to 6 weeks! We have come a long way with the development of keyhole techniques, day case units, enhanced recovery and emphasis on early rehabilitation. In those early days, the results were not that good, with only about one third of patients getting better and developing a stable knee – this meant quite quickly these repair techniques were abandoned, and reconstruction (i.e. removing the damaged ligament and replacing it with a graft) came strongly into favour. Reconstruction quickly became the main surgical option for this injury in the late 1980s and remains so today.

Over the last 30 years this ACL reconstruction surgery has been refined and improved tremendously. Nowadays we perform lots of these operations and generally it is a very good procedure – it is done essentially ‘keyhole’, takes about an hour to do, and patients go home the same day with crutches and a set of exercises to get the knee moving straight away. However, it can and does have some drawbacks (see later).

More recently in the particularly in the last few years, as surgical techniques, arthroscopy technology and materials have all continued to advance, there has been a revival of interest in the ACL repair operation.

Limitations of ACL reconstruction

As an honest UK knee surgeon, I tell all my patients undergoing an ACL reconstruction the benefits of the surgery, the likely natural history of the condition if we weren’t to do the surgery (i.e. the non-operative alternatives), the risks involved (both general risks with any surgery and specific risks to that particular operation), and the likely success rates, in particular the chance of returning to pre-injury sports. It’s also important to explain that the operation is actually only the start of the journey and the period of rehabilitation, to give the knee the best chance of a good recovery and return to sports, is at least 12 months (and in some recommendations up to 18 months in younger patients). In my hands 80% of my patients having an ACL reconstruction get back to the pivoting sports they want to. With regard to re-injury and re-rupture of an ACL graft, the overall percentage quoted in the literature is around 5% but, unfortunately this is significantly higher (up to 25-30%) in the adolescent patient group.

So why all the fuss about ACL repair – basically some of the advocates of this technique are showing some really promising early results, which is starting to percolate slowly through the specialist orthopaedic knee world. In my opinion, it does have some potential advantages over ACL reconstruction, as shown below.

No donor site morbidity

The first is that there is no donor site morbidity of the graft (the majority of UK ACL surgeons take two of the hamstring tendons from the back of the thigh, to make a 4-strand graft, which can give posterior thigh pain, tweaks and issues) – this is completely avoided.

Much less risk to growth plates (in youngsters)

In the younger age group where the growth plates are still open, (boys approx. <16 years old / girls approx. <15 years old) minimising trauma to these is important to prevent possible growth arrest problems.

Better proprioception (joint position sense)

Retention of the proprioceptors in the native ACL must be of benefit in giving the brain biofeedback when performing to pivoting and cutting movements in sports and activities.

Faster rehabilitation and return to sports / activities

The rehabilitation tends to be quicker with patients getting back to sports in a faster time in some cases. There is no doubt that keeping a young sportsman or sportswoman away from sports for the necessary 12-18 months has a negative impact on their psychological wellbeing.

No bridges burnt

Perhaps the most important thing to stress is that we haven’t ‘burnt any bridges’ and it still allows us to do the default reconstruction at any point down the track.


I must emphasise although there are some surgeons who will attempt to perform ACL repair on all types of ACL rupture, in my hands I will only repair if it’s a clear proximal detachment from the femoral notch.

It’s imperative to catch these patients as early as possible and get them to theatre certainly within 6 weeks, otherwise an ACL repair becomes much harder to do and the likely success rates are much reduced – this is one of the reasons for writing this blog because historically in the UK, we aren’t great at getting these patients to the right knee specialist as quickly as we could.

We don’t have any real long-term data yet on these newer techniques. In the short-term, patients are returning to their sports and activities quicker, but how the knees will hold up in the future in terms of further meniscal damage, joint surface damage and early arthritis remains to be seen. From past series using synthetic ligaments called autograft, leaving foreign material inside a joint is not always sensible, but by using the newer more biologically friendly materials (which have been used in the shoulder joint for many years without problems) and also with the option to remove the reinforcement tape after 4-6 months and test the repair arthroscopically, which I do in all my skeletally immature patients, I feel more confident in using this technique.

The other key point here is outcomes – all our patients are entered into the National Ligament Registry which captures their PROMS data automatically for up to 5 years post operation. As time goes on we should start to yield valuable data regarding this technique.

How do we do an ACL repair?

The repair is done via arthroscopy (‘keyhole surgery’) using 2 small portals (scars) either side of the knee cap. Fluid is introduced into the knee so the pictures from the artroscopic camera are easier to see on the monitor. The remains of the ACL ligament (remnant) that has been pulled off its notch attachment are freed up with special instruments. The surface of the notch is roughened, in order for it to bleed and provide a better grip and biological healing environment for the repaired ligament. Using special grabber instruments strong sutures are passed twice into the remnant of the ACL (see pictures 4a and b).


The sutures are then pulled up through a special tunnel in the femur, to reattach the ACL to the pre-prepared area on the notch (see picture 5a). The sutures are tied over a suspensory button at the outer surface of the bone (distal thigh). A special surgical tape is then passed across the front of the repair to act as a seatbelt (see picture 5b) and help stabilise the knee whilst the repair heals. 4-6 months afterwards this synthetic tape can be removed as a day case procedure.



I hope this blog has been interesting and has stimulated thoughts and questions.

If you are a physiotherapist or sports therapist and would like to talk more about this or any other aspect of knee trauma or orthopaedics, if you would like to sit in with me in clinic, or come to an operating session, please contact my secretary on the numbers below.

If you are a parent or a patient and want to meet me in clinic to discuss anything further please also contact my secretary on the numbers below.

Nev Davies is an expert specialist knee surgeon in the Reading area with expertise in Children’s orthopaedics. He is one of 6 consultants that makes up the Reading Hip and Knee unit.

We are passionate about education and communication to give the best possible care to our patients. If you would like one of us to come to your surgery or clinic to talk on any subject around the hip or knee then please contact us.

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