Causes
ACL injury can occur when the knee is forcefully hyperextended or forcefully abducted.
1. Pathogenesis
ACL rupture is usually the result of forceful hyperextension or forceful abduction of the knee. A simple ACL injury can occur with forceful hyperextension under non-weight bearing. ACL injuries can also occur with knee hyperflexion. ACL injuries are higher in the body than in the femoral condylar attachment point and in the tibial attachment point, and the tibial attachment point injury is sometimes manifested as an avulsion fracture. 50 cases were counted by Kennedy (1974), and the most common injury was to the middle ligament, accounting for 36 cases (72%), while the femoral condylar attachment injury was only 9 cases (18%), the tibial attachment point injury was 2 cases (4%), and 3 cases (6%) were unknown. In the past two years, the author has repaired and reconstructed more than 30 cases of old ACL injuries under arthroscopy, except for one case of tibial avulsion fracture, all of which were parenchymal ligament ruptures.
2.Clinical manifestations
Some patients feel the sound of tearing in the knee joint during strong trauma, followed by knee weakness, severe joint pain, rapid swelling, blood accumulation in the joint, and subcutaneous bruising around the joint often indicate joint capsule injury and joint dysfunction. Patients with old injuries may develop quadriceps atrophy, a feeling of weakness (giving way) or misalignment, and decreased motor ability. The examination may show a positive anterior drawer test (ADT), a positive Lachman test, and a positive axial shift test.
3.Complications
Intra-articular fracture or avulsion fracture may occur in a small number of patients.
4.Examination
Laboratory tests
No relevant laboratory tests.
Other auxiliary tests
Lachman’s test The patient is lying down with the knee bent at 15°-20° and the foot on the bed. The examiner grasps the lower end of the patient’s femur with one hand and the upper end of the tibia with the other hand and pushes forward and backward in opposite directions. If there is forward movement beyond the healthy side, it should be considered positive. However, care must be taken to distinguish whether the patient is being pulled back from the posterior sunken position to the normal position or whether there is indeed an anterior displacement. The original intent of this test was to detect anterior displacement to clarify ACL, and in particular to facilitate the determination of anterior internal or posterior external bundle injury in ACL (Figure 1).
Knee radiographs may show a tibial intercondylar ramus tear fracture, with widening of the joint space on one side on internal and external stress examination. Segond fractures are occasionally seen.
MRI In the acute phase, MRI can confirm the diagnosis by more than 5%. In the chronic phase, MRI is not necessary due to clear signs.
Knee arthroscopy.
5. Diagnosis
With a history of trauma and obvious knee signs, combined with X-ray and MRI examinations, the diagnosis is generally not difficult. A small number of patients with acute injury pain, protective quadriceps spasm and negative anterior drawer test require further examination under anesthesia, and the method is detailed in posterior cruciate ligament injury.
Arthroscopy of the knee, flushing out the blood collection, reveals bleeding or small clots at the fractured end of the ACL. Injury to the subsynovial ligament, which appears normal under arthroscopy but has abnormal length and tension, may suggest the possibility of this injury.
X-ray examination of the knee may show a fracture of the intercondylar ridge of the tibia, and widening of the joint space on one side is seen on internal and external stress examination.
6 Treatment
Whether to treat conservatively or surgically in the acute phase after an ACL injury has been the subject of controversy. Noyes et al. found that with conservative treatment, 1/3 of patients had no joint instability, 1/3 had instability during exercise, and 1/3 had instability during usual activities, all of which suggest that ACL injury can be treated conservatively in the early stage, but ACL tibial attachment point or tibial attachment point avulsion However, early surgical treatment is preferable for better recovery of cruciate ligament function.
Non-surgical treatment For simple ACL rupture or incomplete rupture, the affected knee can be fixed in a 30° flexion position with a long-leg cast, paying attention to pushing the upper end of the affected tibia backward before the cast is formed, and fixing it for 4 to 6 weeks. Quadriceps training is started after 3 days of cast immobilization.
Surgical treatment
Femoral condyle attachment point avulsion repair: the severed end of the ligament should be re-sutured back to the medial side of the femoral epicondyle posteriorly. The fixation point is anteriorly biased is a mistake that is easily made, especially since the anterior medial bundle should be sutured posteriorly so that the new suture conforms to the normal attachment position (Figure 2).
Repair of tibial attachment point avulsion: by drilling a tunnel from the anteromedial aspect of the upper tibia toward the intercondylar ridge of the tibia, the ligament severed end is sutured with a fixation wire and the wire is led out of the tunnel and fixed to the anteromedial aspect of the upper tibia (Figure 3). The wire was stretched tightly and the ligamentous end was embedded behind the bone hole and ligated and fixed in the 30° flexion position of the affected knee.
Repair of ligament parenchymal rupture: the acute phase is generally not treated, as described below in both ends of the ligament parenchymal rupture, respectively, fixed with Bunnel method sutures, with the suture on the side near the femoral condyle attachment point fixed after penetration from the bone hole of the upper tibia, and the suture on the side against the tibial attachment point fixed after penetration from the bone hole of the femoral epicondyle. Most patients still have instability after surgery and require reconstruction again.
Repair of avulsion fractures of the intercondylar tibial ridge: sutures can be used to pass through the tendon bone attachment or across the bone fragment and then through the anterior and inferior tibial bone holes to tie and fix (Figure 4).
Postoperative management: fix the knee in a 20° to 30° flexion position with a long-leg cast. Exercise the quadriceps contraction. For avulsion fracture suture, immobilize for 4 weeks; for stop point avulsion and central fracture, immobilize for 6 weeks and practice knee movement after removal.
From the above methods, it can be seen that the repair method varies depending on the site of the ACL fracture. In the author’s case, the best results were obtained in the ACL tibial attachment point avulsion fracture repair group with wire suture fixation, all of which were superior. The results of ligamentous attachment point avulsion repair with wire sutures were not as good as the former. There are two reasons for this: (1) the avulsion fracture heals faster than the ligament, the external fixation time is slightly shorter, and the joint function is restored earlier; (2) the repair of the ligament attachment point is different between the two methods. As described in the previous anatomy, the attachment points of each fiber in the ligament are arranged in a certain form, and in avulsion fractures, the attachment points of the ligament are completely restored to normal after the fracture is repositioned. In the case of avulsion fractures, the attachment points of the ligaments are completely normalized after the fracture is repositioned, whereas in the case of avulsion fractures, although the attachment points are still accurate under direct vision, the arrangement and tension of the ligaments are difficult to reach the original anatomy.
In cases of tibial and femoral stop avulsion fractures, the closure cannot be repositioned and early surgical repositioning should be performed.
Those with medial meniscus rupture with knee interlock that cannot be self-reduced should be surgically explored.
In knee dislocation, ACL rupture combined with PCL and LCL rupture, early repair of LCL is advisable, if PCL degree III injury, reconstruction of PCL and posterior external horn injury is required first, combined with medial collateral ligament injury can be treated conservatively first.
Indications: The indications for surgery for fresh injury are
ACL repair methods.
Obsolete ACL injuries
There are two conditions of old ACL injuries.
An avulsion fracture of the intercondylar ramus of the tibia, for which surgical incision and repositioning should be performed due to the fracture displacement, which occurs anteriorly in the knee joint to block the knee joint movement and restrict the knee extension. If the avulsion fracture is not completely bony at the displacement, the scar tissue in the fracture notch can be removed and the avulsion fracture can be repositioned and fixed with wires as if it were a fresh fracture, and the postoperative result is still satisfactory. In the case of a long time, even if the ligaments are somewhat contracted, the fracture can be restored to its original position by slowly traction of the clamped ligaments and flexion of the joint during the operation. In the advanced cases treated by the author, the knee function was restored to excellent level.
In the case of old ligament avulsion or rupture, the main symptom is knee instability, which is anteriorly straight or accompanied by rotational instability. Knee movement is normal.
7.Prognosis
After treatment, the prognosis is generally fair.