Hearing a "pop" sound during exercise does not necessarily mean a ruptured anterior cruciate ligament? Doctor: First do 3 major tests to clarify
What I’m most afraid of is hearing a “pop” sound while exercising! How to confirm whether the anterior cruciate ligament is ruptured?
Anterior cruciate ligament rupture is one of the worst nightmares for anyone who loves sports. However, clinically, there are still many people who are not aware of the injury and think it is a repeated knee sprain. After seeking medical treatment, they discover that the anterior cruciate ligament is ruptured, causing knee instability. Anterior cruciate ligament injuries often occur when one foot lands on the ground in an unstable state, or when the foot does not rotate with the body when a sudden stop is made or the direction of a sprint is changed. This causes the ligaments to be torn apart by the inertia of the body.
“When I was injured at that time, I heard a snap in my knee, and then my knee swelled up. I went to the clinic to pump water, and when it came out, it was dark red.” This is the most commonly heard injury story. How do you know if your anterior cruciate ligament is stable? You can do the following tests and checks.
Anterior drawer test: The subject lies on his back, with the hip of the tested foot flexed at 45 degrees and the knee flexed at 90 degrees. The tester stands at the subject’s feet, wraps his hands around the subject’s knees and hips, places his thumbs on the joint surface, and pulls his hands in the direction of the subject. Use your thumb to feel whether there is any front-to-back displacement of the joint.
Lachman test: The subject lies flat on his back. The subject will slightly bend the foot being tested 20-30 degrees and turn it slightly outward. He will hold the thigh with one hand and the calf with the other hand and put his thumb on it. On the tibial tuberosity. Pull the thighs back and the calves forward to move forward and backward. And feel the degree of displacement.
Pivot shift test: The subject lies on his back with the foot being tested straight and flat. The tester turns the foot under test inward with one hand, and applies pressure from the outside of the knee inwards with the other hand to make the knee inward. Knee valgus force. Maintain this position with your hips flexed 30 degrees, then slowly bend your knees from the straight position to the end, and feel if there is any abnormal movement of the knees “rebounding”.
When testing, pay attention to comparing both feet. Some athletes are born with looser ligaments. If there is no obvious difference between the two feet, it does not necessarily mean that the ligaments are ruptured. Sometimes, athletes are stronger, so the examination method will be slightly different.
If the patient is too strong or too weak, the results will be affected. Among the three tests, “it” has the highest accuracy.
According to research, the pull-forward test is the easiest to perform, but it is also the less accurate test. Some studies have pointed out that the sensitivity of this test is only 38%; that is, out of 100 patients with anterior cruciate rupture, only 38 may have a positive reaction to the anterior pull test. Reasons for inaccurate testing include inflammation and swelling after an acute injury that prevents the knee from bending to 90 degrees, or fear of pain that produces a protective mechanism of reflex contraction of the hamstrings, resulting in the inability to pull the tibia forward.
The Lachman test has high sensitivity and high specificity. When done correctly, the accuracy can be as high as 96% for completely ruptured anterior cruciate ligaments. This examination is commonly used clinically to rule out cruciate ligament rupture, which means that if Rahman’s reaction is negative, ligament injury can be ruled out. However, the Lachman test is somewhat difficult to implement in practice. Commonly encountered difficulties are as follows:
The examiner’s hands are too small and not strong enough, or the patient is too strong and has too developed muscles.
The patient exerts excessive force on his thighs.
The torque displacement test is currently recognized as the most specific test. That is, when the test is positive, it can be highly suspected that it is an anterior cruciate ligament rupture. But it is also the most difficult test to perform clinically. The principle of the torque-displacement test is to reduce the knee from a subluxated state. Subjects are prone to feeling discomfort when they are clearly conscious, so this test alone is generally not used to diagnose ACL rupture.
These 3 tests can all be examined together clinically. Generally speaking, I will start with the pull-forward test; if the reaction is negative, I will do the Lachman test. If there is a positive reaction in any of the above two tests, a torque displacement test will be performed to evaluate stability. In addition, there are other auxiliary inspections that can be used for downgraded inspections.
How to rebuild the anterior cruciate ligament tissue? Which areas of tendon can be considered for removal?
The tests and examinations of the anterior cruciate ligament are mentioned above, so how to reconstruct the damaged tissue clinically? In fact, after the anterior cruciate ligament is ruptured, it usually cannot be sutured back. It is necessary to take tendons from other parts of the original attachment points at both ends as a replacement for the anterior cruciate ligament reconstruction. The location of the tendon is related to the location of another wound, the strength of the ligament after reconstruction, and the healing ability of the attachment point. It is indeed a science.
Generally speaking, the most common tendon harvesting sites are as follows:
Semitendinosus and gracilis: High strength, high mobility of the two tendons, few postoperative complications, tendons may re-grow, but tendon length and width are relatively unstable.
Patellar tendon: The patellar tendon can be removed together with the cortical bone at both ends of the head and tail, so the attachment point has good healing ability. However, there is a risk of patella fracture after removing the tendon in this area; in addition, the wound is on the knee, which is prone to pain when kneeling.
Quadriceps tendon: Patellar cortical bone can be removed to increase the healing ability of the attachment point. In the initial stage, the knee extension function will be impaired and the length of the tendon will be shorter.
Peroneus longus: The width and length of the tendon are sufficient, and its strength exceeds that of the normal anterior cruciate ligament. However, the stability of the foot will be reduced after removal, and the ankle joint is prone to stiffness after surgery.
Are there any concerns about insufficient strength of allogeneic tendon transplantation? Is “artificial ligament” no longer a mainstream option?
In addition, some people use “allogeneic tendon” as an option for anterior cruciate ligament reconstruction. The advantage of allograft is that it reduces another wound. It is an option when multiple ligaments need to be reconstructed or are ruptured again after reconstruction and there is a lack of usable tendons. Although the allograft ligament is removed from the human body, there is less problem of immune rejection because the tendon does not have blood vessels. However, in terms of strength, it is still weaker than the native tendon.
Many people confuse “artificial ligament” with “allogeneic ligament”. Artificial ligaments are woven with high-strength textile threads and claim to be able to attach fibers, tendon cells or other tissues, but the overall survival rate is only 10 years. Although it can still be seen in certain places, due to the high risk of re-rupture, foreign bodies in the knee, and adhesion problems, it is no longer a standard ACL reconstruction surgery option.
The choice of ligaments depends on the patient’s physical condition and the surgeon’s habits and experience. After you learn more, you can have a more detailed discussion with your doctor.
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