What tendon is your anterior cruciate ligament made of?
Jaarlijks ondergaan in Nederland ongeveer negenduizend mensen een voorste kruisband reconstructie. Voor het maken van een nieuwe kruisband wordt een pees gebruikt die als kruisband gaat functioneren. Hiervoor zijn verschillende mogelijkheden. De pees die gebruikt wordt om een kruisband van te maken wordt in medisch jargon een “graft” genoemd. Van welke pees wordt jouw voorste kruisband gemaakt is nuttig om te weten. In deze blog lees je op basis van welke factoren de orthopedisch chirurg jouw graft kiest en wat de verschillen tussen de grafts zijn.
Michael de Levie and Wybren van der Wal Orthopedic surgeons at the Bergman Clinic and Gelderse Vallei
What is an anterior cruciate ligament?
The ACL is a Dynamic structure, rich in neurovascular supply and comprised of distinct bundles, which function synergistically to facilitate normal knee kinematics in concert with bony morphology. Characterized by individual uniqueness, the ACL is inherently subject to both anatomic and morphological variations as well as physiologic aging.
– Freddie Fu –
What are the graft choices?
Different types of tendons can be used for anterior cruciate ligament reconstruction. A simple division can be made between the body's own material (autograft), donor material (allograft) and synthetic material. In addition, in some cases the patient's own anterior cruciate ligament can be sutured.
In a first anterior cruciate ligament reconstruction, body-derived material (autograft) is almost always chosen. Exceptions are possible, of course.
The different tendons from which an anterior cruciate ligament is made.
The anterior cruciate ligament surgery in 5 steps
- Removing the tendon from the thigh.
- Watch surgery; the knee is assessed on the inside and any other injuries are treated (such as a meniscus tear or cartilage defect)
- Drilling tunnels in the lower leg and upper leg (into which the new cruciate ligament will be placed)
- Inserting and fixing the cruciate ligament in the tunnels
- Closing the wounds.
The anterior cruciate ligament surgery by hamstring technique.
Autograft (body's own material):
The advantages of an autograft are that it is the body's own material which will not be rejected. Furthermore, the risk of retearing the reconstructed cruciate ligament is lower when using an autograft compared to an allograft (donor material). In addition, it is cheaper to use autograft material than donor material.
For an autograft, the orthopedic surgeon can choose from three tendons. The patellar tendon (patellar tendon) and the hamstring tendon are the most commonly used grafts. The quadriceps tendon has been increasingly used in recent years.
This person has had multiple anterior cruciate ligament surgeries.
The hamstring tendon:
There are three hamstring tendons on the back of the thigh: the Biceps Femoris, Semimembranosus and Semitendinosus tendons. The Semitendinosus tendon is used to create the hamstring graft. Depending on the thickness of this tendon, the Gracilis tendon may also be used to make the new cruciate ligament. This is because the new cruciate ligament must have a minimum diameter of 8 millimeters to reduce the chance of tearing again.
The hamstring has another important job besides bending the knee. In sports, slowing down a sprint or landing is a risk for cruciate ligament injury. Here, the hamstring has the ability to take power away from the knee and direct it toward the strong glutes. By using part of the hamstring for the graft, the remaining part may be less able to perform this task. However, it has been shown that in about two-thirds of people in whom the semitendinosus tendon is removed, it grows back and is properly functional.
The long strands are the hamstring tendons
One advantage of using the hamstring as a graft is that there is little risk of symptoms resulting from the removal of the tendon (so-called donor-site morbidity: pain at the site of the incision where the hamstring was removed). A second advantage is that there is less risk of knee stiffness than when using the patellar or quadriceps tendon. In addition, the hamstring tendon can handle large tensile forces (2.5 times more than the original cruciate ligament). The risk of re-rupture is the same as with the use of other tendons. Of course, this advantage does not outweigh the preservation of the original cruciate ligament. The native anterior cruciate ligament is superior in strength, function and anatomical position to a reconstructed cruciate ligament.
A possible disadvantage of the hamstring tendon is that over the years it tends to become somewhat more lax (stretching) than the patellar tendon. Some studies show this while others find no differences. Another disadvantage of using a hamstring tendon is that it does not grow in as quickly as the kneecap tendon. Because of this, the hamstring tendon has about 8 weeks left to grow in firmly while the kneecap tendon needs 5-6 weeks. However, it does not mean that the new cruciate ligament can be loaded 100 percent after 8 weeks. The tendon has grown attached but still goes through several stages to be converted from tendon to cruciate ligament. In this process, the tendon is weakest between 8 and 12 weeks and gets stronger in the months that follow.
Winning the hamstring tendon
The cutaneous nerve to the lower leg runs near the incision from which the hamstring is extracted. As a result, it is common for this nerve to be damaged. The result is dullness of the skin. Very gradually feeling returns over the months, but often an area of skin continues to feel duller. An alternative technique is to approach the hamstring from the back of the thigh. This leaves the dermal nerve intact.
All in all, the hamstring technique is a widely used and popular technique for anterior cruciate ligament repair.
The benefits of the hamstring tendon are:
- No or lower risk of knee stiffness or pain than with the quadriceps and patellar tendon.
- Hamstring is a strong tendon, however, the re-rupture probability is not lower.
- Hamstring tendon gives less pain compared to the patellar tendon technique (sawing out bone blocks).
- Smaller incision where the tendon must be extracted with less chance of residual pain.
- The length and thickness of the hamstring tendon is difficult to predict
- A weakening of hamstring strength. In two-thirds of people, the semitendinosus recovers.
- The hamstring tendon may possibly develop some laxity over time.
- The ingrowth of the hamstring graft takes longer than the kneecap tendon (8 weeks on average).
- During surgery, the cutaneous nerve can be damaged, causing a numb sensation on the skin.
The kneecap tendon (patellar tendon) is attached to the underside of the kneecap and extends to the front of the lower leg. The tendon is responsible for stretching the knee. Using the patellar tendon to repair the cruciate ligament is a technique that has been used for a long time (1963). It is also called the Bone Patella Bone (BPB) technique. The name refers to the bone blocks at the ends of the patellar tendon (kneecap tendon). During surgery, two bone blocks are sawed out. One bone block comes from the lower leg where the patellar tendon attaches (tuberositas tibiae) and the other bone block comes from the lower part of the kneecap.
The patellar tendon is a strong and stiff tendon. This makes it a commonly used tendon for anterior cruciate ligament reconstruction. Another advantage of the patellar tendon over the hamstring technique is that it is less likely to dull the skin. Another advantage is that the bone blocks of the graft grow into the tunnels faster (5-6 weeks). The fusing process can be compared to the healing process of a bone fracture.
The patellar tendon with the bone blocks at the ends.
The main disadvantage of this technique is that pain is usually indicated to a greater or lesser degree at the site where the bone blocks are cut out. The degree of pain also depends, among other things, on the size of the incision (1 large or two small ones).
Drawing anatomy for determining insicion
Because of the use of this tendon and the additional pain and swelling from surgery, the strength of the upper leg muscle decreases rapidly. Regaining muscle control and building muscle strength usually takes more time compared to the hamstring technique. In addition, the knee is often a bit stiffer with bending and stretching. This recedes as rehabilitation progresses. Another relatively minor risk occurs after sawing out the bone block from the kneecap. This can cause the kneecap to break when subjected to large forces. But fortunately, this rarely occurs.
The benefits of the patellar tendon are:
- Strong and rigid tendon.
- Smaller chance of skin dullness.
- Rapid ingrowth of the bone blocks 5-6 weeks.
- Good fixation of bone to bone.
- Greater likelihood of persistent pain in the front under the kneecap (where the bone blocks were removed). This often causes symptoms when sitting on the knees.
- Slower recovery and building of upper leg muscles.
- Increased risk of knee stiffness with stretching and bending.
- Low risk of kneecap fracture.
Relative to the patellar tendon, the quadriceps tendon sits at the top of the kneecap. The difference with the kneecap tendon is that it has a bone block on one side. This, like the patellar tendon, has the advantage of growing into place faster. However, the quadriceps tendon can also be gained without a bone piece. The quadriceps is a strong and thick tendon and therefore suitable as a graft for anterior cruciate ligament reconstruction.
Extracting the quadriceps tendon
Why was the quadriceps tendon added to the existing grafts?
The patellar tendon technique usually produces pain at the front of the knee to a greater or lesser degree. The hamstring technique is an alternative in this regard. But the hamstring is also the muscle that inhibits the forward displacement of the lower leg and thus supports the function of the anterior cruciate ligament. Compared to the quadriceps, the hamstrings are naturally less powerful muscles. The idea behind using the quadriceps tendon is to prevent pain at the front of the knee (patellar tendon) and maintain hamstring function. Another advantage is that the quadriceps tendon is easy to gain. In addition, it is a strong and thick tendon.
The disadvantage of the quadriceps technique is that the quadriceps muscle is affected by the removal of part of the tendon. Recovery of control and strength requires more time because of this. Flexion also usually needs more time and attention to recover. Because of both factors, rehabilitation generally takes longer and recovery takes relatively longer. A cosmetic drawback may be reduced healing of the skin. Because of the pulling forces on the wound, the scar may not recover as nicely. In conclusion, the use of the quadriceps tendon is a fairly new technique. Because of this, few long-term effects are yet known.
Benefits of the quadriceps tendon are:
- The tendon can be extracted with unilateral bone block or without.
- Lower risk of kneecap injuries.
- Hamstring strength is not affected.
- A good and safe tendon to extract.
- A strong, thick and tensile tendon.
- Prolonged rehabilitation due to impaired quadriceps strength building.
- Prolonged stiffness of the knee on bending.
- There is a chance that the scar may not recover as nicely.
- Fairly new technology, there are few long-term effects known.
The donor tendon is biological material taken from a deceased person. Usually the Achilles or hamstring tendon is used. You don't have to be afraid of the tendon being shed. The tendon is processed so that this does not happen.
The great advantage of using a donor tendon is that the muscles around the knee remain intact. As a result, you have less pain and muscle loss. Recovery is often faster in the beginning. The main disadvantages are that a donor tendon is very expensive and of limited availability. In addition, it is not clear who the tendon comes from and what that person's background is. The quality of tendons varies between people and depends in part on age, lifestyle (smoking, for example) and sports background. The main disadvantage of using a donor tendon is that it is more likely to tear again, compared to using one's own tendon.
The benefits of a donor tendon are:
- No risks in extracting the graft.
- Less pain after surgery
- faster recovery of muscle function
- less scarring
- The quality of the tendon is less predictable
- Expensive alternative
- Restricted availability
- Greater re-rupture probability
History of use of plastic materials:
In the past, plastic materials were more often used to make an anterior cruciate ligament plastic. The benefits are the same as with a donor tendon, only the high recurrence rate led to this being discontinued. But developments are not standing still.
New techniques in anterior cruciate ligament surgery.
In recent years, there has been increasing research into repairing one's own cruciate ligament. Recently, a study was started in the Netherlands that is being conducted at several hospitals. The study examines whether the own cruciate ligament can be repaired in selected patients. It involves cruciate ligament injuries in which the cruciate ligament is torn at the location of the upper leg. The torn cruciate ligament is sutured back and reinforced with a plastic band. The great advantage is that the patient's own tissue is preserved and only narrow tunnels need to be drilled. It is also possible to return to the old level of sports faster.
Internal bracing Brace Enhanced ACL Repair (BEAR)
There are an increasing number of studies reporting that the anterior cruciate ligament has a chance of spontaneous repair. In ons blog gaan we hier dieper op in (volgt nog). In 50-60% of cases, the anterior cruciate ligament attaches to the posterior cruciate ligament, regaining some stability. This blog addresses this. The spontaneous repair and or regrowth of the anterior cruciate ligament has led to the BEAR technique (Brigde, Enhanced ACL Repair). The cruciate ligament is sutured and given additional stimulation with the patient's own blood to grow back into place. This procedure should be performed within three weeks. The advantage for young athletes is that this is a technique where only small drill tunnels are made. As a result, there is a lower risk of damaging the growth plates. The results have now only been carried out in pilot(s) studies (USA), but the prospects are interesting.
Take home message
Van welke pees wordt jouw voorste kruisband gemaakt is nuttig om te weten. Het is goed om de voor- en nadelen te kennen van de verschillende grafts. De specialist zal zorgvuldig met jou de geschikte graft keuze bepalen. Al met al liggen de resultaten van de verschillende graft keuzes dicht bij elkaar. Op dit moment loopt er zelfs een onderzoek waarbij geen verschil wordt verwacht tussen de verschillende grafts. Uiteraard volgt er een update wanneer deze resultaten bekend zijn.
However, the choice of graft is only one of many factors in the success of anterior cruciate ligament reconstruction.
Some key factors affecting recovery:
- Being selective with who qualifies for anterior cruciate ligament reconstruction.
- Surgical technique (tunnel placement)
- Other injuries such as meniscus, cartilage and/or ligament injuries
- Preparation for surgery
- Status and function of the knee before surgery
- Knee rehab
- Psychological factors
- Therapy compliance
- Going through surgery and rehabilitation at a knee specialist.
Mocht je na het lezen van deze blog “van welke pees wordt jouw voorste kruisband gemaakt” nog vragen hebben, bespreek je vragen met je arts en/of fysiotherapeut. Eventueel kan je een ook een bericht achterlaten en kunnen mensen uit het netwerk reageren of cliënten om hun ervaring te delen.
Good luck with your recovery!
Podcast: van welke pees wordt jouw voorste kruisband gemaakt? door Wybren van der Wal