Anterior Cruciate Ligament Injury and Treatment
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The anterior cruciate ligament (ACL) is one of the main restraining ligaments of the knee (see anatomy above). The ACL is sited in the centre of the knee and runs from the back of the femur to the front of the tibia and acts to prevent excessive forward movement of the tibia. It’s action, however, is to keep the knee stable during rotational movements like twisting, turning or side-stepping activities.
Injuries to the ACL typically occur during a non-contact twisting movement and a popping sensation can often be felt or heard. Immediate swelling often occurs due to bleeding into the knee (a haemarthrosis). Other injuries to the knee can occur at the same time including meniscal tears (cartilage) or damage to the joint surface.
The ACL also provides important information to the muscles around the knee (proprioception), which are involved in protecting the knee during activities.
If the ACL is torn the knee is likely to give way with twisting activities and if this is associated with knee swelling, it is likely that damage is being done to the joint surface and/or meniscal cartilage. Continued damage will eventually result in osteoarthritis.
The symptoms of patients with an injury to the ACL include a feeling of instability or giving way. They may involve swelling and pain. Typically this will be with twisting activities, however a small proportion of patients become so unstable that even simple activities may cause giving way. There are also some patients who are able to return to pivoting activities without giving way although this is rare.
A ruptured ACL can normally be diagnosed from the history of the injury and confirmed with specific tests at the time of your examination. The diagnosis can be difficult in some cases (especially fresh injuries where examination may be too uncomfortable and those with other injuries to the knee); in these cases the diagnosis can usually be confirmed by MRI scan. A torn ACL cannot be seen on x-ray.
Late diagnosis of ACL injuries is very common but unfortunately the knee often sustains further damage during the delay months (or even years) due to patients trying to return to twisting activities. Unfortunately this additional knee injury adversely affects the ultimate outcome of reconstructive surgery.
Surgery is required for most ACL injuries in patients wishing to return to an active lifestyle. Some patients with this injury choose to alter their lifestyle in order to avoid activities that make the knee give way. A small proportion of patients are able to continue with their activities without major problems. These “copers” are typically (but not always) patients with lower physical activity levels, who do not participate in pivoting/twisting activities.
Non-surgical treatment of an ACL injury involves a supervised physiotherapy programme concentrating specifically on:
Functional Knee Braces are sometimes prescribed to help patients with damaged ACL’s. Their benefits are not fully understood although they may help with proprioception (see above). They are expensive and may not provide much in the way of support to knee stability.
Following an ACL rupture your surgeon may decide, after discussion with you, that reconstruction is appropriate.
ACL reconstruction is the commonest ligament reconstruction performed around the knee. ACL reconstruction is an attempt to replace the stabilizing function of the anterior cruciate ligament. The ACL reconstruction procedure involves removing the remains of the damaged ACL and replacing it with a graft. A number of grafts are available for use to replace the ACL.
The two commonest graft techniques are to use two “hamstring tendons” – the semitendinosus and gracilis muscle tendons – or a so-called BTB (bone tendon bone, or patella tendon graft). The preference of the Yorkshire Knee Clinic Surgeons is to use hamstring grafts as first choice. The evidence in the medical literature is that there is little or nothing to choose between these two main grafts in terms of results.
Other grafts are available in more unusual situations.
Anterior cruciate ligament reconstruction is usually performed using arthroscopic (keyhole) surgery. There is however a small (4 to 5 cm) incision below the knee where the tendons for the graft are harvested from. The basic technique of anterior cruciate ligament reconstruction is to identify the correct insertion points on the femur and tibia for the ACL. At these insertion points tunnels of an appropriate size to match the graft are drilled through the bone. The graft is then pulled up through the bone and is secured using screws, pins, staples or other specialised anchoring devices.
ACL reconstruction may be performed either as day case or overnight surgery.
In patients who are having the operation for appropriate reasons and who comply with rehabilitation (6-9 months), there is a 90 to 95% chance of a good result: that is, where stability is restored enough for the patient to undertake activities, including sports, that they were previously unable to.
Complications include infection (<1% significant), nerve damage (a numb patch of skin, quite common over a small area, but rarely a problem), stiffness (uncommon) and failure of the graft due to re-injury or unexplained failure.
Anatomic ACL reconstruction
The aim of ACL reconstruction is to replicate the normal anatomy of the ligament in order to allow a greater chance of returning to pre-injury level of activity. Over the past 20 years the surgeon’s understanding of the anatomy of the ligament has increased with the result being a shift in the position within the knee of where the graft should be placed.
More recently a technique using two separate grafts (Double Bundle Technique) was advocated. Clinical results to date have failed to show any convincing benefit of adopting this technique for what is a more technically demanding and risky operation. As a result this procedure has fallen out of favour with most surgeons.
‘Anatomic ACL reconstruction’ represents another concept in ACL reconstruction that is increasingly being discussed by specialist knee surgeons but some consider the term to be misleading as previous techniques also aim to reconstruct the ACL as ‘anatomically’ as possible.
The surgeons of The Yorkshire Knee Clinic endeavour to use the current optimal (clinically-proven) surgical techniques to give the best possible outcome for their patients following surgery.