Anterior Cruciate Ligament (ACL) rupture is very common particularly among young people who participate in competitive sports. The most common symptom after ACL rupture is instability, where the knee feels as if it will ‘give way’ particularly during rotational movements. However pain, recurrent swelling and locking of the knee are also fairly common symptoms especially if there is associated damage to either the articular cartilage or either of the menisci (See Cartilage Injuries).
Arthroscopic view of absent ACL due to chronic rupture (Click to Enlarge)
The indication for reconstruction of the ACL is persistent instability. If a ruptured ACL is left untreated there is a very high risk of subsequent tears to the menisci and damage to the articular cartilage. By reconstructing the ACL and thereby stabilising the knee this risk may be minimised and may therefore reduce the likelihood of osteoarthritis developing in later years.
The outcome of ACL reconstruction is improved with earlier surgery. The current recommendation is for early rehabilitation with physiotherapy to regain movement and muscle strength followed by surgery within 6-12 weeks from injury. However if the diagnosis is initially not made, reconstruction can be undertaken at a later time.
Step 2: Diagram showing how ACL graft is put in place (Click to Enlarge)
Step 1: Drill holes for ACL reconstruction (Click to Enlarge)
ACL reconstruction involves an inpatient stay of 2-3 days. The operation is performed under a general anaesthetic. The patient is usually admitted on the day of surgery and will need to remain fasted for 6 hours prior to the procedure. The surgeon will see the patient before their operation and will mark the leg to be operated on.
During ACL reconstruction, a new ligament is made by harvesting tissue from the patient; this is called an autograft. Two common autografts are used; either from the patellar (kneecap) tendon or by combining two of the hamstring tendons. The outcome from both is similar but there is slightly less scarring with hamstring reconstruction.
Step 3 : How the ACL graft is fixed in the femur (Click to Enlarge)
Step 4 : After tightening, the ACL graft is fixed in the tibia (Click to Enlarge)
ACL reconstruction is carried out arthroscopically (keyhole surgery) which enables treatment of any other problems within the knee, e.g. torn menisci, at the same time. Drill holes are made in the tibia and femur where the ACL used to be. The graft is then passed through these holes, tightened and fixed at both ends (see picture). This graft acts as a scaffold; the body slowly grows a new ACL over the graft. This takes between 4 and 6 months.
Smoking significantly affects this process and must be stopped prior to surgery.
ACL graft in place (Click to Enlarge)
ACL graft in place - knee extended (Click to Enlarge)
At the end of the operation a drain is usually inserted into the knee; this is removed 24 hours later. The wounds are closed with absorbable sutures and steristrips, dressings applied, and a bandage placed around the knee.
Most ACL reconstructions do not require a knee brace. Postoperative physiotherapy begins on the day after surgery and continues as an outpatient. There are three main phases of rehabilitation:
During these phases the reconstructed ligament must be protected – the physiotherapists supervise ACL rehabilitation programmes carefully. It takes approximately 6 months before sports-specific training can be undertaken, and return to full sporting activities is usually between 8-9 months.
No operation can guarantee success but the risks of ACL reconstruction are low. Complications due to general anaesthetic are rare as most people undergoing ACL reconstruction are relatively young.
Complications specific to ACL reconstruction include:
