I. Overview of ACL injury
The anterior cruciate ligament (ACL) of the knee is located in the joint, starting from the posterior part of the lateral surface of the intercondylar fossa of the femur and attaching anteriorly, distally, and inwardly to the anterior part of the intercondylar spine of the tibial plateau. the ACL is responsible for the anterior stability of the knee joint and part of its rotation and lateral stability, and is not palpable on the surface of the body, making it difficult for patients to directly perceive injury to this ligament.
In China, the incidence of ACL injuries in the general population does not have exact statistics, but the incidence of ACL injuries in professional female athletes is 0.71%, in men 0.29%, and in women 2.37 times more than in men. It has been reported that 80,000-250,000 ACL injuries occur in the United States each year, with young patients aged 15-25 years accounting for more than 50%; as early as 1996, the Centers for Disease Control and Prevention (CDC) stated that the United States performs approximately In 1996, the Centers for Disease Control and Prevention stated that approximately 100,000 ACL reconstructive surgeries were performed in the United States each year.
The Institute of Sports Medicine at Peking University Third Hospital, where the authors work, currently performs more than 1,400 ACL reconstructions per year. Unfortunately, a significant number of patients with ACL injuries do not receive timely and effective treatment. The lack of patient awareness of the severity of such injuries is one reason; in addition, the inconsistent knowledge of clinicians about ACL injuries also contributes to the lack of timely and effective management of some patients.
ACL injuries are typically seen in sports, with rugby, basketball, soccer, and skiing being particularly common. In addition to knee collisions, 78% of ACL injuries are non-contact and occur with landing, stopping, and violent twisting movements. In soccer, shifting defense and kicking the ball while running are relatively dangerous; in basketball, side-jumping turns and single-leg landings are relatively dangerous; in skiing, the knee rotates outward when the front end of the ski is blocked, which is a more typical non-contact injury mechanism for ACL. Acute injuries tend to have knee swelling, mainly due to blood accumulation in the joint, and can generally occur within minutes to 3 hours after the injury. In acute knee injuries (excluding fractures), 70% of those who present with blood in the knee have an ACL injury.
The incidence of ACL injuries combined with meniscal tears is around 60%. As the duration of ACL injuries increases, the rate and severity of meniscal damage increases accordingly, and some menisci can be sutured when they are first injured, but as the torn flap wears and degenerates repeatedly or as the torn flap itself retears, the rate of partial meniscectomy or resection increases.
Sometimes the meniscus undergoes a “barrel stem tear” (also called a “cradle injury”, in which the torn flap is displaced below the intercondylar fossa, causing interlocking symptoms in the knee joint, with the patient complaining of a “stuck” joint The patient complains of “stuck” joints, elastic fixation of the joint at a certain angle or limited extension or hyperflexion. If the lateral collateral ligament of the knee is injured, swelling and pain may occur in the injured collateral ligament. The medial collateral ligament injury is mostly characterized by swelling and pressure pain on the surface of the medial femoral epicondyle (the attachment point of the medial collateral ligament) or (and) pressure pain on the medial tibial tuberosity.
Second, the basics of ACL injury: etiology prevention, symptoms and related tests
1.Etiology and prevention
General traumatic disorders rarely talk about the cause of the disease, the reason is simple: the cause is trauma! However, the concept of sports medicine should not only focus on the treatment of ACL injury, but also on the prevention of the injury. Until biological and material technologies are perfectly integrated with clinical surgery, reconstructed ligaments will not be as natural as they could be! Therefore, one of our most important tasks is to try to start with the mechanism of injury. Because it is far more meaningful to let an athlete have a normal ACL than to reconstruct one for him!
From the above ACL injury-causing process, it can be seen that the following factors are involved in non-contact ACL injuries.
① Landing on one leg with the full foot on the ground to immobilize the tibia.
② Small angle flexion of the knee joint.
③ Knee valgus occurs.
④ When the quadriceps muscle fires, the N cord muscle (mainly the biceps femoris) is not effectively counteracted, resulting in excessive anterior displacement of the tibia.
Therefore, preventive measures for non-contact injuries in ACL.
① Training athletes must have sufficient forefoot support time, greater than 40ms, when landing, so that the tibia will move with the femur during the “probable injury time” to avoid excessive rotation and excessive forward movement.
② Train the athlete to land with a relatively large knee flexion angle and to control valgus.
③ Train the athlete’s N cord muscle (primarily the biceps femoris) strength to effectively oppose the quadriceps. Of course, the prevention of ACL injury is still a topic well worth studying and exploring, and requires our unremitting efforts!
2.Clinical symptoms
Clinical symptoms are divided into three categories.
①Exclusive injury symptoms of ACL, which are described in detail below.
(2) Combined meniscal, cartilage or other ligament injuries, which can be manifested as knee pain, popping, interlocking or specific to the corresponding ligament (see “I. Overview of ACL injuries”).
Most patients may have atrophy of the muscles surrounding the knee joint, especially the quadriceps muscle.
Acute phase symptoms of ACL injury.
(1) Knee pain, located inside the joint, patients may be afraid to move due to severe pain in the knee joint, some patients can walk with mild pain or even continue to exercise in small amounts.
(2) Knee swelling, which usually occurs within a few minutes to 3 hours of the knee sprain.
(iii) Restriction of knee extension and inflammatory irritation from the ACL rupture with the ligament stump overturned to the anterior aspect of the intercondylar fossa. Some patients may have limited extension or flexion due to meniscal injury. Combined medial collateral ligament injuries sometimes also present with limitation of extension.
Some patients may feel a misalignment in the knee joint at the time of injury (some patients may hear a sound), and start to feel a wobbling sensation in the knee joint when they resume walking about 1-2 weeks after the injury.
(5) Limited knee mobility, mostly due to swelling and pain in the knee joint caused by traumatic synovitis.
ACL injury more than 6 weeks is old, and old ACL rupture mostly has instability symptoms, and instability is manifested in the following 3 degrees.
①Severe instability: ACL combined with poor knee muscle compensation results in a misalignment of the knee joint, which can be felt when walking or jogging in daily life, and this misalignment is usually manifested as a left-right misalignment of the femur and tibia of the knee joint.
(2) Moderate instability: ACL rupture combined with moderate muscle compensation, manifested as not daring to accelerate fast running, not daring to stop or turn sharply when running fast.
③Mild instability: ACL rupture combined with good muscle compensation, manifested as the patient can engage in general sports, the patient can run, carry the ball, but some movements in the game such as jumping up and landing on one foot, using the affected lower limb to support the shot with the healthy foot, etc. cannot be completed, or need a reaction time to complete (reduced motor ability). Regardless of which instability the patient exhibits, the tendency to repeatedly sprain the knee joint during sports or life is also a hallmark clinical manifestation of an ACL fracture.
III. Major treatments for ACL injuries
ACL rupture generally requires surgical treatment, i.e., arthroscopic ACL reconstruction. The current mainstream technique is still to use autologous N-tendon as graft for arthroscopic ACL reconstruction, which is a mature technique with reliable clinical results. The autologous N cord tendon used in the reconstruction surgery is two tendons of the medial thigh: the semitendinosus tendon and the thin femoral tendon (, the tendon is taken in full length and full segment), and the surgeon can complete the tendon extraction with a small incision of about 3 cm in length.
Reconstruction of the ACL requires the drilling of bone channels in the tibia and femur, and then the tendon is grafted into the joint cavity and into the bone channels at both ends in place of the ACL, and the tendon is fixed at both ends of the channels with an internal fixation device. This fixation device is used according to the needs of the procedure and is usually a combination of absorbable and metal nails. Whether the internal fixation should be removed or not depends on whether there is a foreign body reaction at the site of internal fixation, and there is no pain at the site of internal fixation after surgery.
Patients can generally return to office work after 3-4 weeks of rest according to the doctor’s recommendation. Patients with a successful rehabilitation program will walk on crutches in January, off crutches in February, normal walking with splints removed in March, jogging in April-May, general sports and fast running in six months after surgery, and confrontational sports in 10-12 months after surgery.
Some patients are concerned about the difference in clinical outcomes between single- and double-bundle, which is still controversial in clinical practice. Those who originally insisted on single-bundle are still insisting on it, and those who originally advocated double-bundle are now divided into two groups: those who are still diligently pursuing it and those who are returning to single-bundle technique. Until clinical evidence that can convince me emerges, the authors will only do single-beam reconstruction for now.
IV. Indications and timing of ACL reconstruction surgery
Young patients with a confirmed ACL injury need to undergo ACL reconstruction surgery if any of the following are present.
① Repeated sprains of the knee joint.
(2) A feeling of knee instability (see “Clinical Symptoms of ACL Injury” for the classification of instability).
(3) Combined injury to the meniscus or other important stable structures of the knee.
(4) Those with definite cartilage damage in the knee requiring repair.
Patients who do not require ligament reconstruction surgery.
①No indication for surgery as described above and no joint instability.
②The ligament has been ruptured for many years and the cartilage damage is very serious, so other treatment measures should be taken according to the specific situation.
Timing of reconstructive surgery.
①Patients with simple ACL rupture can undergo surgery after the acute phase, when the swelling of the joint has basically subsided and the mobility of the joint is basically normal. If surgery is temporarily not possible, the braking brace should be removed after the acute period, normal walking should be resumed, and muscle strength should be practiced diligently to prevent muscle atrophy.
②In case of combined sutureable meniscal injury or cartilage injury requiring repair (as judged by the doctor), surgery should be performed as soon as possible after the acute period in order to get a chance to repair the meniscus or cartilage, preferably not longer than 3 months.
③In the second point, if there are symptoms of syndesmosis, aim to operate within 3 weeks to prevent difficulties in functional exercise of the joint after surgery.
④In combination with medial and lateral collateral ligament injuries that require sutures, it is best to operate within 2 weeks. After the acute period, the above ligaments basically cannot be sutured, and additional reconstruction is less effective than sutures, and more traumatic and costly.