The distal tibiofibular syndesmosis is an important joint to stabilize the ankle. Alao it is a common clinical injury, accounting for 5-10% of ankle sprain and 23% of ankle fracture [1,3,4]. In the most cases, it is accompanied by other ankle injuries, which can easily cause lateral instability of the ankle(LIA) with long-term chronic pain and traumatic osteoarthritis, which seriously affects the quality of life and work of patients. At present, the treatment of the distal tibiofibular syndesmosis injury is a hot topic in our research. The main method of conservative treatment is to recover by functional exercise after 6-8 weeks fixed with gypsum or support, but for unstable lower tibia and fibula combined injury, surgical treatment is generally recommended. Nowdays , the widely applicable clinical surgical treatment includes rigid fixation (mainly cortical screw fixation) and elastic fixation (mainly Endobutton system)[9-10]. A few scholars have found that the incidence of broken nails is high due to its rigid fixation in the cortical screw fixation , patients can not early weight-bearing exercise, prone to ossification, ankle stiffness and traumatic arthritis, and often need secondary surgical removal, which increased the patient's mental trauma and financial burden, the risk of recurrence is high extremely [10,14,16], Mehdi et al . experiments have proved that Significant screw bending occurred in severe patients with heavy weight after operation. taking these risks into account, some scholars have attempted to treat inferior tibiofibular joint injury by Endobutton plate fixation[8-10,16,18]. The Endobutton device is a novel inferior tibiofibular fixation device with a fixation strength close to the screw, and the semi-rigid biomechanical properties of the device allow physiological fretting between the lower tibia and fibula, thus accelerating ligament healing; no secondary surgery is required to reduce trauma [3,19,21]. Experiments show that there is no risk of screw breakage, no need for routine removal after surgery by Endobutton,and it can better restore ankle function, reduce related complications and other advantages, less trauma [ 16,20].
Although Endobutton plate fixation solves many clinical problems, some studies have reported that it also has some shortcomings. Lou YL et al . research shows that the number of clinical surgical cases is too small at present, it is necessary to accumulate experience through the department operation practice, combined with relevant reports at home and abroad, and we can not guarantee the accuracy of the operation because of the problems of the angle of the needle entry, the position of the fixed device and the quantity of the device placed. As can be seen that double Endobutton the difficulty of double Endobutton plate fixation is the establishment of an ideal and safe and accurate transosseous tunnels . The length of the loop can not be adjusted at will in the operation. We must accurately determine the drill points on the tibia and fibula and the angle and size of the tunnel. in order to identify the ideal transosseous tunnels and coracoid process, many studies have investigated the anatomical features of the dital tibiofibular syndesmosis.But in fact, the location and method of drilling a transosseous tunnels in the tibia and fibula vary depending on the operator and the patient's skeletal structure can be affected.In that case, we combined the anatomical basis of the dital tibiofibular syndesmosis to study and design a personalized 3D printing guide design, placed on the exposed dital tibiofibular syndesmosis, to help find the precise anatomical location of the cross-bone tunnel borehole during surgery, and we experimentally compared the virtual 3 D model with the double Endobutton plate fixation using the 3 D navigation module to build the transosseous tunnels. From our experimental measurements, we found that there was almost no difference between the real model and the virtual model of Endobutton plate fixation. It can be seen that this method can improve the accuracy of transosseous tunnels and reduce the drilling accuracy risk of complications. So transosseous tunnels module based on the 3D printing guide design of the distal tibiofibular syndesmosis reconstruction of the is reliable and can be carried out.
However, the following shortcomings also existed in our study :(1) this study only collected CT and MRI data from a hospital in southwest china, did not contain population data from multiple regions and between different races, and the subjects of the experiment were also patients in this hospital, which was not widely representative. (2) This study is an in vitro study and its rationality and availability are to be confirmed by further studies in clinical trials.
Our study has some weaknesses. First, the samples and individualized 3D printed guide design are imitated in this study. These prospective CT scans without considering whether the AC joint itself affect the building of the 3D guide design, which may lead to some observational errors. Finally, this study is an in vitro research, and its rationality and availability need to be confirmed by further studiess in clinical trials.