The ACL is an important anteriorly stable structure of the knee joint, and its ability to heal on its own after injury is poor, affecting motor function. Therefore, ACL reconstruction is usually performed arthroscopically after ACL injury. The fixation of the ligament stop is the most critical step in the procedure, and the failure of ligament reconstruction is mostly caused by poor fixation. Kurosaka et al. showed that ACL reconstruction failure occurred more on the fixation side than on the ligament itself, and noted that the highest immediate postoperative stiffness could be obtained with compression screw fixation. Good fixation allows for early postoperative bed mobility and weight bearing, which facilitates tendon bone healing, and the use of reasonable fixation methods can increase fixation strength and stiffness. At present, there are three methods of ACL reconstruction fixation: (1) indirect fixation away from the articular surface, such as button plate, portal nail, etc.; (2) direct fixation in the bone tunnel near the articular surface, including various transverse nails, interface screws implanted from outside to inside and inlay fixation, etc.; (3) direct fixation, i.e., interface screws of different materials are used from inside the joint. Indirect fixation is far from the normal ACL anatomical stop, and the longitudinal movement between the graft and the bone tract produces a “bungee” effect and lateral movement produces a “wiper” effect, enlarging the bone tunnel and affecting tendon-bone healing by synovial fluid immersion. Direct fixation and direct-like fixation reduce these disadvantages of indirect fixation. The resorbable interface screws in the bone tunnel are resorbable, flexible, and have little damage to the grafted tendon, and the image is not affected during postoperative MRI and does not need to be removed during revision. The Rigidfix fixation system is a double cross-pin fixation system in which two cross-pin nails are crossed vertically to fix the femoral end of the reconstructed ACL to make soft contact between the tendon and the femoral tunnel so that the femoral tunnel is not prone to collapse. The nail sheath separates the screw from the tendon to avoid the cutting effect of the squeeze screw, which can prevent the rupture of the tendon and make the tendon and the bone tunnel more closely united to promote its healing, and also prevent the leakage of joint fluid. The nails are resorbable polylactic acid (PLA), which can be completely absorbed after 2-3 years, avoiding two surgeries. kousa and Joshua et al. concluded that the application of transverse nail fixation can produce a smaller enlargement of the bone tunnel, and that the best results are obtained with transverse nail fixation at the femoral end, which is significantly better than the extrusion screw, and with Intrafix fixation at the tibial end. In our data, Rigidfix transverse nailing was applied to the femoral side and intrafix expanding squeeze screw was applied to the tibial side, and the knee function scores showed significant improvement compared with the preoperative period after 3, 6, 12, and 24 months of postoperative follow-up. The clinical results were satisfactory. The use of the Rigidfix absorbable transverse nail at the femoral end is a reliable fixation method that is simple and shortens the operative time compared to button plates, but there are certain requirements for the operator’s operation, which we believe should be noted during surgery: ①. The femoral tunnel was established by hooking the posterior wall of the femoral epicondyle, and then the femoral offset guide was adjusted in an abduction manner. (②) The installation of the tunnel rod and connecting rod fixation should be secure, with the transverse nail sleeve located on the anterolateral femoral condyle. ③, after the transverse nail orifice is established, attention should be paid to observe that there should be flushing fluid out, and both ends should be probed for patency using a kerfing needle. Zantop et al. found that 6 weeks after ACL reconstruction, the strength of the extruded nail decreased by 81% and the stiffness decreased by 67%, whereas the Rigidfix as a control group showed a 48% decrease in strength and a 52% increase in stiffness. Several studies have shown that the graft (biologic screw) is uniformly tightly bonded to the bone tract, which facilitates graft healing. In this group of cases, for tibial end tendon fixation, intrafix expanding squeeze screws were used, and the caudal end of the transplanted tendon was squeezed into the nail sheath in four bundles first to establish the expanding channel of the squeeze screws, and then screwed into the squeeze screws to make 360° contact between the squeeze screws and the bone tunnel, with matching squeeze and uniform distribution, and the nail sheath separating the screws from the tendon, and intraoperative operation should be noted: ①, the nail sheath should be located as far as possible in the four bundles under the loop suture guide The central part of the grafted tendon. ②, screwing into the expandable squeeze screw is not easy to use too much force, and it is appropriate to stop, otherwise it is advisable to squeeze the tibial tunnel, resulting in surgical failure. In this group, no collapse of the tibial tunnel was observed. ③, the tail end of the squeeze screw should not be exposed too much, which can lead to pain at the skin incision, there was one case in this group with too much tail end, which was healed after the second stage surgery. (iv) Absorbable sutures should be reinforced to close the tendon stump outside the tunnel, but large suture nodules should not be left. The choice of ACL reconstruction graft must have sufficient strength, overcome graft displacement under circulatory loading, and facilitate healing of the tendon graft to the bone tunnel. The autologous N cord tendon has good biomechanical properties as a graft, with tensile strength and stiffness sufficient for physiologic function. The anterior cruciate ligament needs to withstand a tension of about 500 N during normal activity, so the initial strength of fixation should be no less than this value. The maximum load of the braided four-strand N cord tendon joint graft is 4090N, 229% of that of the ACL, which has a strong antitension load with little effect on the donor area and is structurally closer to the anatomical structure and biological activity of the original ACL, which is conducive to tendon-bone healing.Catalin [6] et al. collected 37 cases and compared the use of autologous N cord tendon with earlier reconstruction of ALC using BPB The former was considered less invasive and had a faster and better recovery. None of our cases had anterior knee pain using autologous cord tendon graft and no graft failure occurred after follow-up, which was able to accommodate high intensity activities and withstand excessive stress. The differences in tibial anterior displacement Rolimeter measurements of the knee, which were statistically extrapolated using the mean two-by-two comparison (SNK method), were statistically significant (P<< span="">0.01) between the preoperative patient’s bilateral knees, between the preoperative and 1 month postoperative comparisons of the affected knee, and between 1 month postoperative and 12 months postoperative comparisons of tibial anterior displacement of the affected knee was not statistically significant (P>0.05). Conclusion Arthroscopic fixation of the 4-strand single bundle autologous N cord tendon using the absorbable Rigidfix transverse penetration nail with Intrafix expandable extrusion screws and reconstruction of the ACL can rapidly restore the stability of the knee joint and reduce pain with less trauma and complications, and can provide early initial stability and later biological stability, which is suitable for clinical application and promotion in primary care hospitals. There is still much room for research on the factors influencing tendon bone healing and biomechanical studies and experimental studies between grafts and fixed biomaterials.