The tension of the PCL is highest in the flexion position of the knee joint, and tibial avulsion fracture mainly occurs in knee flexion. In the flexion position, the lateral condyle of the femur moves backward, and the femur rotates outwards. The force from front to back causes the posterior tibia to be impacted by the femoral condyle, and the tension of the PCL increases sharply, which eventually leads to avulsion fracture of the PCL tibial insertion point[8]. Because the contact area between the posteromedial tibia and the medial femoral condyle is larger than that between the posterolateral tibia and the lateral femoral condyle, PCL tibial avulsion fracture fragments are increasingly larger. If not intervened, they can seriously affect the stability of the posterior part of the knee joint, and the fracture block protrudes behind the tibial intercondylar ridge, which may induce impingement syndrome[9]. In the late stage, quadriceps atrophy, joint effusion, articular cartilage degeneration and secondary meniscus injury can become aggravated, which will seriously affect the quality of life of patients. Therefore, the current view is that PCL tibial avulsion fractures should be firmly fixed to avoid postoperative displacement or poor healing, resulting in the instability of the knee joint [10].
There are many kinds of surgical methods for PCL tibial avulsion fracture, including arthroscopic and open surgical approaches. Arthroscopic surgery has the advantages of minimal trauma, a small amount of soft tissue damage and fast recovery. However, in most total arthroscopic surgeries, a bone tunnel must be drilled on the tibia. The tunnel introduces an internal fixator through the tunnel, which has the characteristics of complex operation, high equipment requirements and a long learning time, limiting its development [11]. Open surgery for PCL tibial avulsion fractures has been widely carried out. The internal fixation materials mainly include steel wires, absorbable screws, hollow screws, Kirschner wires, and wire anchors. Steel wire fixation is convenient and economical, but it easily causes further fracture of the fracture block in the process of the operation, causing secondary damage to the blood supply of the fracture block and affecting fracture healing; moreover, to avoid the fracture of the steel wire after the operation, long-term braking is necessary, resulting in limited joint function and joint stiffness[12]. The absorbable screw material can be absorbed after the operation, and it is unnecessary to remove the internal fixator, avoiding a secondary operation and trauma. However, the external fixation time of absorbable screws, such as plasters or braces, is long, and 4~6 weeks of fixation is advocated. At the same time, absorbable screws have low strength and are characterized by weak fixation and easy displacement[13]. Simple cannulated screw fixation has high fixation strength and stability, but all the stress is concentrated in the screw tail, which easily leads to stress concentration, refracture and internal fixation failure[14].
Due to comminuted fracture, small bone fragments are often difficult to fix, but early rehabilitation exercise requires relatively stable fixation. For the treatment of this kind of fracture, in addition to conventional surgical methods such as tension band steel wire fixation, purse suture fixation and special plate fixation are also currently commonly used. For patients with posterior cruciate ligament avulsion fracture and repair difficulties, a more classic treatment method is to insert two button plates into the broken end of the fracture. The sutures are sewn out along the aponeurosis, and then the two circuits are sewn and knotted with each other. With a button plate, the fracture block is fixed reliably, the fracture surface is in good contact, and the PCL is connected by a nonabsorbable tension suture. This method can reduce any large movement of the fracture block during knee joint functional exercise, disperse the concentrated stress around the button plate during knee joint flexion, reduce the risk of refracture, promote fracture healing and avoid joint adhesion complications[15,16].
The use of double button plate fixation technology has the following advantages: less trauma, shorter operation time, convenient use of instruments and fixtures, and it does not need to be taken out again, thus avoiding secondary trauma. Moreover, the strength of the suture is large, and the tension of the posterior cruciate ligament can be fully reduced by tying the suture band. Double button plate fixation under direct vision is safe and reliable without the need for additional equipment. Even comminuted fractures can also be effectively fixed by knotting.
Limitations
There are also shortcomings in this study, such as small sample size , which may lead to deviations in the evaluation of curative effect. Further expansion of sample size and long-term follow-up are needed to confirm this.