The ACL is the most common type of knee injury and the most commonly injured knee ligament. The ACL usually tears as a result of sudden change in direction causing the knee to rotate inwards. This causes an excessive force to go through the knee joint and through the ACL and if this force exceeds the mechanical strength of the ACL the ACL will tear. This usually happens in sporting injuries and can be due to contact, for example during a tackle and sometimes and mostly in a non-contact situation when landing from a jump awkwardly. The most common sports are football for men and netball in women that result in ACL injury. ACL injuries can also occur in other sports where twisting around the knee can take place such as skiing. Injuries to the knee can also occur during accidents such as trips and falls down the stairs or road traffic accidents.
Do you need ACL surgery?
The decision to proceed to ACL surgery is reached after a careful history, examination and interpretation of the MRI investigations and a discussion with the patient. High level athletes and elite sportspeople require surgery to get back to playing sport at their previous pre-injury level. Non-elite athletes and normal people who have sustained an ACL injury should consider whether they would like to undergo surgery to restore stability to their knee but not everyone requires an ACL reconstruction to have stability. A small proportion of patients can regain knee stability with physiotherapy alone. This depends on a number of factors and these are best discussed with your consultant knee surgeon.
In some individuals, despite physiotherapy, the knee carries on giving way even when walking and therefore surgery becomes essential. In other patients walking and running in a straight line is okay but any twisting or turning results in the giving way of the knee and if the patient requires this level of function, then an ACL reconstruction is recommended. Some individuals have manual jobs which are very strenuous and require complete knee stability and therefore for these individuals an ACL reconstruction is also recommended.
For individuals with high levels of function and demands from their knee (professional sports people and high functioning non-professionals), an ACL reconstruction is usually required to regain knee stability.
What is ACL reconstruction?
ACL reconstruction surgery is a complex operation which is designed to restore stability to the human knee. When an ACL ruptures, a lot of force goes through the knee and it is very unusual for an ACL to be ruptured in isolation. The ACL becomes injured along with other anatomical structures within the knee which help to provide stability. It is imperative that a proper assessment is carried out by a specialised knee surgeon and an appropriate plan made for the surgery.
Other pathologies, like meniscal tears, root tears and ramp lesions must be addressed to ensure a good outcome and minimise the risk of re-injury and re-rupture, which can be disastrous for patients.
How is ACL surgery carried out?
The surgery is carried out under general anaesthesia where the patient is asleep. Sometimes a nerve block is also carried out to provide good pain relief following the operation. The operation is carried out arthroscopically (keyhole surgery).
The knee joint is thoroughly assessed during surgery. The torn anterior cruciate ligament must be replaced by new tissue. A discussion around what type of tissue would be best suited to each individual will take place preoperatively.
The options around the tissue are an autograft which is the patient’s own tissue. This can be hamstrings, patellar tendon or a newer technique using the quadriceps tendon (please see below around graft selection). The tissue is harvested from the donor site taking care not to injure any other structures. Tunnels and sockets are drilled within the tibia and femur and once the graft is prepared it is placed in the anatomical position and tensioned to ensure that the graft performs its function appropriately. At the same time if any other tissues need to be repaired, for example meniscal tears or ramp lesions (please see section on meniscal surgery), these will be carried out at the same time to restore stability to the knee and minimise any risk of further instability and re-ruptures of the graft.
How long does ACL surgery take?
The length of surgery depends on the complexity of the operation. If it is an anterior cruciate ligament reconstruction alone with no other injuries, this can be achieved in around an hour. If other structures require repair then the operation can take longer than sixty minutes, up to around two hours.
What are the aims of ACL surgery?
The aim of ACL reconstruction surgery is to restore stability to the knee joint whilst retaining a full range of movement and allowing the patient to get back to high levels of pre-injury activity and sport.
The success rate of ACL surgery is generally very good in the literature. This depends on the surgeon, the surgical technique and the type of graft used. The overall aim is to restore function and reduce the risks of re-rupture of the graft.
What are the risks of ACL surgery?
The risks of surgery can be divided into general and specific risks. The general risks of surgery are infection, bleeding, damage to nearby blood vessels and nerves and pain. The specific risks to ACL surgery are re-rupture of the graft which is anywhere between 5-10% in the literature. In our practice we have audited our results and our re-rupture rates are as low as 2%. There is also the risk of knee stiffness which can take place after any knee surgery due to the body’s reaction to the surgery and a condition called arthrofibrosis which causes scarring around the knee joint and can result in a stiff knee; the risks of this are generally low.
What is the difference between ACL repair vs reconstruction?
ACL repair is a procedure which aims to repair the torn native ACL back to its attachment on the femur. This procedure was first attempted in the 1980’s and 90’s but the success rates were poor. In modern times new techniques and equipment have become available which allow the direct repair of the ACL ligament. Unfortunately, this procedure is not available to everybody and depends entirely on how much of the torn ligament is remaining in the knee and the integrity of this. It is a very difficult procedure to perform successfully and around 10% of patients may be eligible for this. The procedure is evolving and this is an area where we have a special interest and are researching how to improve the outcomes of repairing the native ACL so that tissue harvest and autograft donation can be minimised.
How is the graft site for ACL reconstruction chosen?
The choice of graft to use for ACL reconstruction is a very important area of discussion. All grafts have their pros and cons. Overall, the performance of the grafts and re-rupture rates are similar in the literature. The main decision making around what graft would be best depends on the requirements of the athlete or individual.
Hamstrings – The hamstrings are the most commonly used autograft type. The semitendinosus and gracilis tendons are long hamstring muscles at the back of the thigh and attach around the medial side of the tibia. These tendons are frequently harvested and prepared and used for ACL reconstruction. This is a tried and tested graft type and has very good performance data in the literature. The re-rupture rates are comparable to patellar tendon and quadriceps tendon. Overall, this graft type has many positives. The main drawback of this graft is donor site pain following the procedure as harvesting these tendons is extremely painful. It also defunctions the semitendinosus and gracilis muscles which have a role to play in acceleration, deceleration and medial sided dynamic knee stability. I would not recommend this graft type for sprinting athletes or for example strikers in football or wingers in rugby.
Patellar tendon – The patellar tendon is also a well-tried and tested graft choice and is the second most commonly used graft in the literature. The patellar tendon has very high tensile strength and due to the bone block taken from the patella and the tibia, it is very good at incorporating into the knee after the surgery. It has many positives and is a very strong graft choice but unfortunately once the patellar tendon is harvested, up to 50% of patients report knee pain at the front of the knee and an inability to kneel down following the surgery. The patellar tendon harvest can also be painful. The patellar tendon does not however defunction any muscles and hamstring strength and speed is retained.
Quadriceps tendon – The quadriceps tendon has become of interest in recent times. It does not result in pain at the front of the knee and patients can kneel down. No muscles are defunctioned around the thigh or hamstrings and therefore the patient retains full power, speed and acceleration. The main drawback with the quadriceps tendon is that it does not have as much long-term data and has previously been prone to stretching out. Due to newer techniques and hardware, the quadriceps tendon can be reinforced to avoid stretch-out.
How much does ACL reconstruction surgery cost?
The cost of ACL reconstruction surgery is in the region of five to six thousand pounds.
Do you need to do anything before ACL surgery? What is involved in prehabilitation?
It is very important to start prehabilitation before ACL reconstruction surgery. The reason for this is that following surgery there is significant muscle atrophy and muscle wasting due to many factors. With good prehabilitation the quadriceps and hamstring muscles as well as core muscle strength, gluteal strength and range of movements around the knee and balance, results in a much faster recovery and therefore this is highly recommended.
How long does it take to recover from ACL reconstruction surgery?
We would recommend a minimum of two weeks off work following surgery. If more than an ACL reconstruction is carried out, for example a meniscal repair or a ramp lesion repair, then the patient may be in a brace after surgery and up to six weeks might be required off work.
A commonly asked question is around recovery from surgery. There are multiple phases of recovery:
Phase one - Immediate postoperative phase lasts around two weeks. There is usually significant swelling, pain and bruising from the surgery and this takes around two weeks to start settling down.
Phase two – Two to six weeks after the initial phase of postoperative recovery the swelling continues to reduce and the range of movement around the knee starts to improve. At around six weeks the knee starts to feel more comfortable.
Phase three – Six weeks to four months. This is a critical period of recovery. This is the time where the ligamentisation process takes place. Ligamentisation is when the graft goes through a physical change from being a tendon-type tissue to a ligament-type tissue where the collagen fibres are realigned and the inherent strength of the new ligament is built up. This is when the graft is at its weakest and following strict physiotherapy guidelines is very important. During this period closed chain exercises and quadriceps and hamstring work as well as proprioception is very important.
Phase four – Four months to nine to twelve months. This is a longer phase of rehabilitation where exercise such as straight line running and progression up to twisting and turning take place. This is the final phase of recovery where regular physiotherapy assessment is required and once this phase is finished, usually around nine to twelve months, patients can return to sport.