TREATMENTS

Anterior cruciate ligament replacement

What is the Anterior Cruciate Ligament?

The knee joint is a complex structure which is supported by four main ligaments. Two of these four ligaments lie outside the knee joint and two lie inside. The ligaments lying outside the knee joint are called the medial and the lateral collateral ligaments and the ones lying inside the knee joint are called the anterior and the posterior cruciate ligaments.

The cruciate ligaments cross each other inside the knee joint and one lies in front of the other. The main function of these ligaments is to provide stability to the knee joint in all activities. Specifically, the main function of the anterior cruciate ligament (ACL) is to prevent the shin bone (tibia) from subluxing on the thigh bone (femur) and preventing the knee from giving way or collapsing.

How does the ACL get damaged?

The ligament is damaged usually in sporting activities which involve the foot being fixed onto the ground and the body twisting above it causing the ligament to rupture. Typically, this can take place whilst skiing, playing football or rugby. When the ligament ruptures, usually a crack or a pop is heard and the knee gives way and swells immediately. It is difficult to take weight through the knee joint. In the acute stage of injury which last for about 3-6 weeks the knee is swollen, difficult to straighten and feels unstable. It is also difficult to examine the knee joint appropriately at this stage and the advice given is to rest the knee, take pain relief and also apply an elasticated stocking to reduce the swelling.

An x-ray is usually done at this time to make sure that there are no other bony injuries or fractures. Once this acute phase has subsided the knee can be examined appropriately and physical signs of instability can be elicited. Following an appropriate clinical examination a magnetic resonance scan (MRI) is usually arranged to assess the status of the cartilage, ligaments and also the soft tissues in and around the knee. Occasionally the diagnosis is in question and an examination under anaesthetic and an arthroscopy (keyhole surgery) may be required to confirm the diagnosis.

Who needs Reconstructive Surgery?

Once the diagnosis has been confirmed and if there is no other injury to the knee joint for e.g. a cartilage or meniscal tear, a course of physiotherapy to strengthen the quadriceps is recommended. If, despite the initial physiotherapy the knee continues to give way and on clinical examination there is increased laxity in the knee joint it is appropriate to consider reconstruction of the ACL. The main reason for reconstructing the ACL to my mind is to prevent this extra instability in the knee joint which can secondarily lead to damage of the meniscus and the cartilage inside the knee joint and thereby increase the chances of osteoarthritis in the long run.

What is the correct timing of the Operation?

It is usually not considered appropriate to consider reconstructive surgery in the acutely injured knees. A four to six week period of rest followed by physiotherapy is essential for the knee to settle down, the swelling to subside and also quadricep muscles to be built up and proceed to reconstructive surgery.

What does the operation involve?

The operation involves three stages. The first stage is to prepare a graft which will be used as the new ACL. The graft can be made of synthetic materials, it can be taken from donors who have died and donated their grafts and also can be taken from the patient, themselves.

The problem with the synthetic materials is that there is a significantly higher rate of failure and also infection and inflammation. Patella tendon allografts can be used from donors that have died but again there is a higher failure rate as they are significantly weaker in strength and also there is the possibility of transmission of infection via prions (small viral particles). Finally, the commonest form of grafts used presently, are the central third of the patella tendon or the hamstring tendons harvested from the patients’ themselves. The patella tendon graft is a 1 cm wide strip which is taken from the central third of the patella tendon along with small blocks of bone from the bottom of the kneecap (patella) and also the upper part of the shin bone (tibia). As far the hamstring tendons are concerned, they are present on the inside of the leg and go up into the thigh. A small incision is made in front of the knee joint along the shin bone and these tendons are harvested. Very rarely there may be a problem in harvesting these grafts and then one has to consider alternative options. In a sense, before consenting for surgery both options should be explained and the patient be prepared for hamstrings as well as the central third patella tendon graft.

The second stage of the procedure is preparation of the knee for insertion of the graft. This procedure is carried out arthroscopically (keyhole surgery). The old or the ruptured anterior cruciate ligament remnants are taken away and the shin bone and thigh bone are prepared for making tunnels through which the graft would be passed. The tunnels are made with the help of special jigs and the final stage consists of inserting the graft appropriately with adequate tension and fixation into the tunnels with screws or special transfixation pins.

How long does the operation last?

The operation usually takes about 40-60 minutes and assessment of the other structures in the knee is also made at the same time.

What happens after the operation?

Following the operation the wound is dressed in the standard manner and a cryocuff (ice pack) is applied to decrease swelling and physiotherapy commenced within 24 hours of surgery. CPM (continuous passive motion) is also commenced within 24 hours of surgery. CPM consists of placing the leg into a machine which assists in extending and flexing the knee. The inpatient stay is usually between 1 to 3 days but finally depends upon the patient’s circumstances and the surgeon’s preference. In our practice we aim to get the patients home within 2 days following the operation. However, the patient is discharged only when he/she is safe on crutches and able to negotiate stairs. We do not routinely use braces or a plaster following anterior cruciate ligament reconstruction in our practice.

What happens following discharge from the hospital?

Following discharge from the hospital, the process of rehabilitation begins. A great deal of success of the reconstruction depends upon the subsequent post operative physiotherapy regime. This continues for a period of 6-9 months and usually at the end of this period one is able to return to high contact sports like football or skiing.

What are the complications?

Although the ACL reconstruction is a fairly safe and rewarding operation it is not free from complications. The main complications that are to be borne in mind are infection, a clot in the leg (DVT) and graft failure. The graft can fail early due to an insecure fixation or late due to a further injury or gradual attrition. If the patella tendon is used as a graft then there is usually a patch of numbness or sensory disturbance in front of the knee joint. This is secondary to bruising or damage to the skin nerves that supply the area and may be permanent. It is also difficult to kneel following this type of graft.