(A) Overview of the anterior cruciate ligament The anterior cruciate ligament (ACL) is an important structure that stabilizes the knee joint and is the most vulnerable of all the ligaments in the knee. rupture of the ACL not only affects daily activities and sports, but also causes further damage to the intra-articular structures. Therefore, it has become a consensus that reconstruction of the damaged ACL is needed in order to restore the structure and function of the knee joint. The starting point of the ACL is located in the posterior medial part of the intercondylar concave surface of the femoral epicondyle, and the ending point is located between the intercondylar ridge of the tibia and its anterior slope, between the medial and lateral meniscus. between the anterior angles. Because the ACL is composed of fibers with distinctly different origins, ends, and courses, scholars generally advocate dividing it into different bundles. With the exception of a few authors who advocate dividing the ACL into 3 bundles, most authors advocate dividing the ACL into 2 bundles, the anteromedial (AM) and posterior-lateral (PL) bundles, depending on their relative position in the tibial attachment, and that the AM and PL differ in position and tension at different degrees of knee flexion. In fact, the ACL is relatively well divided in the mid-segment, followed by the femoral attachment, and least well divided in the tibial attachment. Even in the mid ACL, the cross-section is irregular and does not consist of a single rounded stripe or two rounded strips. The cross-sectional area of the mid ACL is approximately 35 mm2 in women and 44 mm2 in men. (ii) Indications and contraindications The purpose of reconstructing the ACL is to restore the stability of the knee joint, to provide a foundation for daily life and sports, and to avoid further damage to the meniscus and articular cartilage. Therefore, regardless of the patient’s age, all patients who wish to restore motor function and have indications for ligament reconstruction can be reconstructed. The decision to reconstruct after an ACL injury depends not only on the degree of knee instability, but also on the patient’s lifestyle and level of exercise. Although age is also a measure, the overall level of exercise is a more important factor in determining this. It is often assumed that younger individuals also have a higher level of motion and are more dependent on the normal function of the knee joint. However, an increasing number of older adults are now participating in prolonged, high-sport recreational activities, so age should not be a contraindication to ACL reconstruction. (C) Preoperative examination 1. Medical history Taking a detailed medical history and performing a physical examination is the key to an accurate diagnosis of an ACL injury. The injury is mostly caused by sports or car accidents. When the trauma occurs, the patient can hear a loud rupture sound, followed by severe knee pain, restricted movement, and obvious swelling. After the acute phase, the patient’s symptoms may be significantly reduced, and some patients may occasionally experience a “weak leg” phenomenon. However, in general, the patient’s motor functions such as running will be significantly affected, so attention should be paid to braking the knee joint and avoiding strenuous exercise. 2. Physical examination The clinical examination for ACL injury consists of three special tests: the anterior drawer test, the Lachman test and the axial shift test, each of which is performed in comparison with the healthy knee. The Lachman test and the axial shift test are more sensitive, but are often familiar only to specialists in arthroscopy or sports medicine, so there is a significant underdiagnosis of ACL injuries. The Lachman test and the axial shift test are more sensitive, but are often familiar only to specialists in arthroscopy or sports medicine. (1) anterior drawer test: the patient is lying down, the affected knee is flexed to 90°, the assistant fixes the patient’s foot, and the examiner sits on the back of the patient’s foot if the examination is performed alone, with the thumbs of both hands placed in front of the proximal calf and the other four fingers placed behind the proximal calf, and the knee is forced anteriorly. The anterior drawer test in the internal rotation position examines the ACL and lateral ligament structures, the anterior drawer test in the neutral position examines the ACL, and the anterior drawer test in the external rotation position examines the ACL and medial ligament structures. Although the anterior drawer test is the classic method to examine ACL injury, there are many disadvantages, such as the inability to flex the knee for acute injury patients due to intra-articular hematoma, the ease of false negatives due to the blockage of the posterior horn of the meniscus behind the femoral condyle, and the inability to distinguish between soft and hard termination points due to the large number of blocked structures. (2) Lachman test: The patient is lying flat, the examiner pads the affected knee with his or her own knee and flexes it 15° to 30°, the left hand presses the distal thigh and the right hand holds the proximal calf, pushing and pulling in the anterior-posterior direction. If the affected knee is thin, the left hand can also hold the distal thigh directly and the right hand holds the proximal calf, flexing the affected knee 15° to 30° for pushing and pulling in the anterior-posterior direction (Figure 4-7-8). Abnormal forward movement of the tibial condyle, or a significant condylar impingement sensation is (+) compared to the healthy side. This test has the following advantages: it can be examined in acute injury of ACL, the sensitivity is significantly increased because of the absence of meniscal interference, and the termination point of the ligament can be examined. (3) Pivot shift test: ACL injury can lead to knee instability, and this test is a method to reproduce joint instability using manual examination (Figure 4-7-9). The pivot shift test is performed with the patient in a supine position with the hip flexed at 45°, the knee extended, and the lower extremity abducted. There are three axial shift tests: (1) axial shift test degree 1: internally rotated calf with knee valgus stress, gradually flexing the knee from the straight position, with prerotation bounce of the tibial epicondyle near 20° and 40°; (2) axial shift test degree 2: neutral calf with knee valgus stress, gradually flexing the knee from the straight position, with prerotation bounce of the tibial epicondyle near 20° and 40°; (3) axial shift test degree 3: externally rotated calf with knee valgus (3) Axial shift test degree III: external rotation of the lower leg and application of knee valgus, gradual flexion of the knee from the straight position, with prerotation bounce of the tibial epicondyle at 20° and 40°. 3. Imaging The imaging of the knee includes routine radiographs to rule out fractures, to assess pre-existing degenerative changes and to document the overall force lines of the lower extremity. Knee stress radiographs may also be taken to clarify the degree of tibial anterior displacement. MRI is most helpful in diagnosing ACL injuries and has a higher sensitivity, as well as showing other combined injuries and pathologic changes that can help the physician decide whether surgery is needed. However, MRI can also be missed or misdiagnosed, so the results should be combined with physical examination or KT-1000 examination to make a diagnosis. The ACL fibers have been absorbed, and the normal and damaged images cannot be displayed on MRI, so no diagnosis can be made. After ACL injury, the tibia and femoral condyles become metabolically active, but after the acute trauma subsides, the metabolism becomes normal again. After ACL reconstruction, if the stability of the knee joint is restored, the bone metabolism generally tends to normalize gradually, but the speed of normalization is not consistent for each patient; if there is a more serious combined injury or the stability of the knee joint is not restored well, there will be persistent abnormal bone metabolism and the patient will have more pain. 4. Other examinations Imaging examinations such as X-rays and MRI can provide information on the anatomical morphology of the ACL, but based on the biomechanical function of the ACL, the clinic also needs information on its role in knee stabilization to determine treatment options. The knee ligament checker (KT-1000, KT-2000) is an instrument to determine the anterior and posterior displacement of the tibial condyle under standard force, and can quantitatively determine the anterior-posterior stability of the knee, i.e., the anterior-posterior laxity of the knee joint. The examination requires a bilateral comparison, and in general, a difference in anterior laxity of >2 or 5 mm on the affected side compared to the healthy side can lead to a preliminary diagnosis of ACL injury. It is worth noting that despite the high accuracy of KT-2000 measurement, when measuring knee stability, one should be familiar with its measurement principles and rule out factors affecting the measurement based on clinical experience in order to truly improve the examination. (D) Surgical methods 1. Autologous N-tendon (HT) reconstruction of ACL is the most popular method, but there are some special indications for N-tendon reconstruction of ACL: those who have already used autologous BTB to reconstruct ACL but failed, those who have patellofemoral joint disease and want to avoid aggravating symptoms, those who have high requirements for postoperative aesthetics, those who want to avoid kneeling pain and kneeling pain because of frequent kneeling work (such as carpet workers, carpenters, etc.) Those with anterior knee pain and kneeling pain, and those with short, injured or diseased patellar tendons are not suitable for BTB reconstruction of the ACL, but are more suitable for HT reconstruction of the ACL. Excluding patients whose HT has been resected, there are no absolute contraindications to the use of HT reconstruction of the ACL. Patients with systemic ligamentous laxity are a relative contraindication to the use of HT for ACL reconstruction, and these patients may be better suited for autologous or allogeneic BTB with greater ultimate stiffness, and patients with combined structural damage to the posterior medial ligament of the knee (except for simple medial collateral ligament damage) may also be unsuitable for HT for ACL reconstruction because of the potential for further damage to the posterior medial stability of the knee. If the tendon diameter is found to be too small by preoperative MRI, or when the HT is taken intraoperatively, it is also difficult to ensure the strength of the four-strand HT, and other materials should be used instead. 2. bone-patellar tendon-bone reconstruction of the ACL Reconstruction of the ACL using BTB grafts used to be the gold standard for ACL reconstruction. The advantage of this technique is that the graft has sufficient strength and stiffness, and studies have shown that the average strength of a 14 mm to 15 mm wide BTB graft is equivalent to 168% of a normal ACL. In addition, the bone blocks at the ends of the graft allow for early and reliable healing of the BTB graft to the bone tunnel. The main disadvantage of using BTB for ACL reconstruction, in addition to donor complications, is the inability to perform anatomic reconstruction of the ACL. In the “true” “gold standard” reconstruction of the ACL with BTB, both ends of the graft are fixed with interface screws. This method of fixation has some drawbacks: first, at the femoral end, the femoral tunnel is not as close as possible to the overdetermination point due to the use of interface screws, and even with precautions, there is a possibility of tunnel wall rupture; in addition, the reliability of screw fixation is not guaranteed due to the varying degree of bone laxity of the tunnel wall, the different degree of matching between the tunnel and the bone pins, and the variation of the degree of parallelism between the screw and the bone pins during screw extrusion. . On the other hand, since the healing time between the bone peg and the bone tunnel is only about 6 weeks, there is almost no possibility of non-healing, and the need for strong screw extrusion is questionable. In the case of ACL reconstruction with BTB, a change to suspension fixation can effectively avoid some of the disadvantages of interface screws. The goal of ACL reconstruction is to restore knee stability and avoid recurrence of injury and damage to the meniscus and articular cartilage. Patients of any age who wish to restore motor function and who do not have contraindications to using the patellar tendon as a graft can undergo ligament reconstruction with BTB. There are some special indications for ACL reconstruction using BTB: HT is relatively contraindicated in patients with generalized ligamentous laxity, and BTB is the best choice if autograft reconstruction is necessary due to its greater stiffness; HT is also contraindicated in patients with combined injury to the posterior medial ligamentous structures of the knee, because the N cord muscle is the posterior medial knee For patients with a combined injury to the posterior medial ligament structure of the knee, HT should not be used to reconstruct the ACL because the N cord is a dynamic stabilizing structure of the posterior medial knee. BTB reconstruction of ACL is contraindicated in patients who frequently kneel (such as carpet workers, carpenters, etc.) because the anterior knee pain and kneeling pain caused by this method will directly affect their work; BTB reconstruction of ACL is contraindicated in patients with short patellar tendon, injury or lesion, and the patellar tendon itself is not available; BTB reconstruction of ACL is also contraindicated in patients with patellofemoral joint disease to avoid aggravating the symptoms. 3.Allograft tendon reconstruction of ACL Allograft tendon reconstruction is the same as autologous reconstruction, the advantage is that it does not need to take the autologous tendon. The disadvantage is that it may be rejection and more expensive. In the case of good economic condition, it is recommended. 4.Artificial ligament Artificial ligaments have a history of more than 10 years. In the past, the artificial ligament was the same in design, mostly simple carbon fiber or nylon compilation structure, which was prevalent for a while when it first appeared, but with the emergence of various complications (such as synovitis, ligament elongation and loosening, etc.), it was gradually eliminated by the clinic. The LARS ligament is now more commonly used internationally, and all of the indications for HT are also applicable to LARS ligament reconstruction of the ACL, which is particularly useful for patients who enjoy sports, especially professional athletes who are eager to return to competition. Because the LARS ligament does fixate, postoperative rehabilitation can be relatively aggressive and recovery is relatively quick. However, the disadvantage is that it has a certain lifespan.