The anterior cruciate ligament (ACL) is an important structure that stabilizes the knee joint. It is a serious knee injury that often leads to knee instability and reduced or lost motion. If not treated properly, it will lead to severe degenerative osteoarthritis in advanced stages. To restore the joint structure and function, it has become a consensus to reconstruct the injured ACL.
With the advancement of surgical techniques, arthroscopic reconstruction of ACL has become the main method of treating ACL injury today. 42 patients with knee ACL injury were treated with arthroscopic reconstruction of autologous semitendinosus tendon and thin femoral muscle tendon from January 2007 to March 2010, and satisfactory results were achieved, which are reported below.
1. Clinical data
There were 42 cases in this group, 23 men and 19 women. Age ranged from 18 to 60 years old, with a median of 29 years old. All were patients with knee ACL injury. There were 18 cases of left knee and 24 cases of right knee. Causes of injury: 28 cases of sports injury, 4 cases of fall injury, 6 cases of car accident injury, 1 case of fall from height injury, and 3 cases of other injuries. There were 11 cases of combined medial collateral ligament injury, 26 cases of meniscus injury, and 3 cases of combined medial collateral ligament injury and medial meniscus injury. All knees had pain, swelling, weakness, and limitation of movement.
MRI showed that the anterior and posterior diameters of the ACL were thickened and widened, and there was high signal in the ligament. The preoperative Lyshohm knee score [1] was (61.4±2.3) in this group of patients. The time between injury and consultation ranged from 2 weeks to 55 months.
2. Methods
2.1 Surgical approach
An anterolateral knee approach was used for microscopic exploration to clarify the site and extent of ACL injury and the presence of combined injuries. The hyperplastic synovial membrane and intercondylar fossa scar tissue were shaved with an arthroscopic planer to trim the ACL stump and preserve the stump. A 3 cm-long longitudinal incision was made one finger below the tibial tuberosity to free the semitendinosus tendon and the thin femoral tendon, and the 18- to 26-cm-long tendon was cut with a tendon extractor.
The two tendons were removed from the muscular and hairy parts, and the ends were braided and sutured with No. 2 polyester braided thread and left in traction, which was folded back into 4 strands to prepare a 7-10 cm long, 7-8 mm diameter, 15-20 N tension graft tendon, which was wrapped in gentamicin saline gauze.
The anteromedial and anterolateral approaches to the knee were used, preserving 1 to 2 mm of the ACL inferior stop stump, placing the tibial tunnel locator from the anteromedial approach, placing the tibial locator at an angle of 25° to 30° to the sagittal plane of the tibia and 50° to 55° to the tibial plateau, and drilling the locating guide pin with the center of the stump as the center point; the posterior superior edge of the lateral wall of the intercondylar fossa of the femur (at the position of 2 points on the left knee and 10 points on the right knee), and A hollow drill of the same diameter as the tendon was used to create tibial and femoral tunnels along the guide pin. The length of the bone tunnel was measured, and the appropriate length of Endobutton was selected.
The folded tendon was suspended from the Endobutton, and the grafted tendon was placed through the tibial tunnel, joint cavity, and femoral tunnel along the traction line, and the Endobutton was turned over at the anterolateral aspect of the distal femur. the traction line was pulled at the external opening of the tibial tunnel, and the knee joint was repeatedly flexed and extended 10 times to tighten the reconstructed ligament. After microscopic confirmation of good position and tension of the reconstructed ligament, the tibial tunnel extrusion screw was screwed in a 30° flexed knee position to firmly extrude the ligament against the tibial tunnel wall.
The tendon ends were reinforced outside the tibial tunnel with portal nail fixation in 23 cases and cortical bone screws + washers in the lower extremity in 19 cases. After reconstructing the ligament in good position and tension by microscopic examination again, the joint cavity was flushed, the incision was sutured, and wrapped with cotton pads and elastic bandages with pressure.
2.2 Postoperative management
Immediately after surgery, ankle pump exercises were performed, and isometric contraction of quadriceps and N cord muscles and straight leg raising exercises were gradually performed; 1 week after surgery, incomplete weight-bearing exercises of the affected limb were performed, together with joint flexion and extension and balance exercises; 2 weeks after surgery, complete weight-bearing exercises of the affected limb were performed; 3 months after surgery, the brace was removed and daily life resumed; 6 months after surgery, strenuous exercise or specialized training was gradually resumed. Specialized training.
3.Results
In this group, the incision was healed at stage I. The knee flexion and extension function returned to normal 6-8 weeks after surgery. There were no complications such as incision infection, joint cavity infection, or deep vein embolism. The postoperative joint cavity had varying degrees of stasis, which were cured by cold compresses, elevation of the affected limb, knee puncture and fluid extraction or pressure bandaging. All patients in this group received follow-up for 6 to 18 months. All patients returned to work with knee flexion over 120°.
One patient had knee pain and tenderness during strenuous exercise, three patients had mild claudication, and the rest had a basically normal gait. The drawer test and Lachman test were positive in 2 cases, and suspicious positive in 4 cases. The postoperative Lysholm score was (92.5±3.66).
4. Discussion
ACL injury is a serious intra-articular knee injury, which can significantly affect knee stability and lead to motor dysfunction, and if not treated in time or improperly treated, it can further cause damage to the knee joint. Arthroscopic reconstruction of ACL has the advantages of small incision, less tissue damage, accurate intraoperative positioning, less chance of infection, no obvious postoperative complications, and fast postoperative healing, etc. It has been widely carried out at home and abroad, and is currently the best method to treat ACL injury.
4.1 Selection of grafts
The most commonly used grafts for reconstruction of ACL mainly include autologous middle 1/3 bone-patellar tendon-bone, autologous N cord tendon, allograft tendon, artificial ligament, etc. The tissue characteristics of each graft differ, resulting in different stability, early functional rehabilitation, graft longevity, and postoperative complications of the reconstructed knee joint after ACL.
The use of allograft tendons for ACL reconstruction is associated with the risk of immune rejection and disease transmission; therefore, we do not recommend the use of allograft tendons for initial reconstruction or single bundle ACL reconstruction, but generally as an option for ACL revision and repair of multi-ligament injuries in the knee. Reconstruction of the ACL using artificial ligaments has the following disadvantages: the long-term outcome is uncertain; worn out artificial ligament fragments can cause refractory synovitis; there is a high potential for infection, which is difficult to eliminate once infected; there are problems with histocompatibility; and the surgery is expensive.
ACL reconstruction using autologous mid 1/3 bone-patellar tendon-bone was once the gold standard for ACL reconstruction [2]. However, this method has the disadvantages of being highly invasive and prone to postoperative anterior patellar pain, and is now mainly used for reconstructive ACL revision. At present, the use of autologous 4-femoral N-tendon tendon for ACL reconstruction has the tendency to become the “gold standard” for ACL reconstruction. The initial strength of the semitendinosus tendon and the thin femoral tendon can reach 4,589 N after folding, which is much greater than the strength of the normal ACL (1,730 N) and can fully meet the tensile strength of the reconstructed ACL [3]. Moreover, it is less traumatic when taking the N cord tendon and has less impact on the function of the knee joint on the tendon taking side.
In addition, there is no problem of rejection when autologous 4-strand N cord muscle tendon is used for ACL reconstruction. Therefore, we believe that autologous 4-stranded N-tendon is an ideal material to replace ACL. In our clinical work, we also found that the stability of the knee joint in the early postoperative period was good regardless of the type of graft used and the thickness of the reconstructed ligament. However, with the passage of time and the increase of patients’ activities, the tension and strength of the reconstructed ligament decreased to different degrees, and some patients showed positive or suspicious positive drawer test and Lachman test, and individual patients even showed clinical symptoms of knee instability.
However, from the perspective of safety, effectiveness, economy, reduction of surgical trauma and long-term efficacy, we believe that the application of autologous 4 femoral N cord tendon for ACL reconstruction is a more ideal choice.
4.2 Positioning of tibial and femoral tunnels
Isometric reconstruction of the ACL is an important guarantee of good function and stability of the knee joint, which requires high requirements for the positioning of the tibial and femoral tunnels. In clinical practice, we have selected the posterior superior edge of the lateral wall of the femoral intercondylar fossa (at the position of 2 points on the left knee and 10 points on the right knee), 5 mm from the posterior wall, as the positioning point of the femoral tunnel, where the isometric fixed grafts can have the best effect.
For the establishment of the bone tunnel, we have the following understanding.
(i) Many scholars fix the angle of the tibial locator at 45°, but in general, because the arthroscopic anterior internal incision is higher than the intercondylar ridge, when the tibial locator is fixed, the upper arm of the locator is mostly at an angle of 5° to 10° to the cross-section of the tibial plateau[u1], so we often set the tibial locator angle between 50° and 55°.
② The femoral tunnel is mostly established via the tibial tunnel, so we also require an angle of 25° to 30° inward in the coronal plane [u2] when positioning the tibial tunnel so that it is possible to position the femoral tunnel to a slightly lower position, otherwise an anterior inferior internal auxiliary incision is also required to position the femoral tunnel.
4.3 Fixation of the endoprosthesis
With the continuous development of endoprosthetic materials, there are now various types of endoprosthetic fixation methods, such as: titanium extrusion screws, resorbable extrusion screws, transverse penetration nails, portal nails and internal buttons. However, any fixation method is subject to micromovement in the early postoperative period, which may also contribute to the enlargement of the bone tunnel and ligamentous laxity. On the femoral side, we use Endobutton micro-perforated plates to suspend the tendon, and good healing between tendon-bone can be achieved.
Generally, six months after reconstruction, the phenotype of the grafted tendon is similar to that of a normal ACL [7]. Due to the suspension fixation, the tendon exerts less pressure on the wall of the bone tract, allowing the posterior wall of the femoral tract to be preserved thinner in order to bring the superior stop of the reconstructed ACL closer to the anatomical point[u3] . On the tibial side, we routinely use dual fixation, and in the tibial tunnel we use absorbable interface screw fixation with good results. Resorbable interface screw fixation is convenient, reliable, and does not require secondary surgical removal, and it reduces the “wiper effect” and “bungee effect” and the enlargement of the bone tunnel.
In the application of resorbable interface screw fixation, the tibial tunnel length is appropriately extended to prevent entry into the joint cavity, and the nail diameter is ≥l mm compared with the bone tunnel to enhance the fixation reliability. In addition to the use of absorbable interface screws in the tunnel, we also used portal nails or plain screws outside the tibial tunnel to enhance fixation to increase initial stability and facilitate earlier rehabilitation.
4.4 ACL stump preservation
There is a debate on whether the ACL stump is preserved or not. Liu Yujie et al [8] suggested that there are two advantages of preserving the ACL stump: (i) it is beneficial to the revascularization of the implanted ligament, which is easy to form synovial wraps; and (ii) it is beneficial to the recovery of proprioception. However, there is a lack of scientific means to test whether preserving the ACL stump is beneficial to the recovery of proprioception.
We believe that two points should be noted in preserving the ACL stump.
(1) The surgeon must have extensive surgical experience so that the stump does not affect the accuracy of positioning;
②After the tibial bone tract is established, the tibial drill can be inserted 1 cm into the joint cavity via the bone tract[u4] and the knee can be gradually flexed and extended under arthroscopic observation to understand whether the stump is impinging or not, and if it is, it needs to be removed.
In addition, planned and progressive postoperative functional exercises and rehabilitation of the affected knee can avoid knee adhesion stiffness, improve muscle strength, and enhance joint stability. Particular emphasis should be placed on exercises for the medial femoral muscles to avoid weakness in walking and leg weakness in the affected knee.