Clinical Anatomy, Biomechanical And Clinical Study Of Bionic Elastic Fixing Device In The Treatment Of Distal Tibiofibular Syndesmosis Rupture

The incisura fibularis connects the medial surface in lowerpart of fibula by ligament fiber to form distal tibiofibular syndesmosis,functioning as an important structure to maintain the stability of the anklejoint. The original structure of ankle joint is changed when the distaltibiofibular syndesmosis is ruptured that often associated with the anklejoint injury. If the treatment for the distal tibiofibular syndesmosis injuryis inappropiate and not able to restore the alignment and function ofsyndesmosis, sequelae as instability, chronic pain, functional deteriorationand traumatic arthritis may will be inevitable. Researchers continuouslymake efforts to improve clinical outcomes of distal tibiofibularsyndesmosis injuries， and designed a variety of internal fixation device.We have made innovations in the fields of the hole preparation methodfor internal fixation device in ORIF. We have modified the angle ofdevice placement in ORIF for syndesmosis. The first part of this researchaim to provide anatomical evidences to back up the clinical usage of thisnew technique. We also have designed a new internal fixation devicecalled “Bionic elastic fixing device”, which is combined with the boltsand Suture-button system. This device can be effective in fixing thesyndesmosis and maximally retains its original function. In the secondpart of the study，biomechanical properties of intact syndesmosis andinjury model fixed with different divices were performed and compareseparately. Result will show which one is the best for syndesmosis.Clinical study was then carried out to prove the effectiveness of thisfixation method and fixing divice. Part1Clinical anatomical observation of the distal tibiofibularsyndesmosisObjective: To analyze the Structural characteristics of the distaltibiofibular syndesmosis and improve the operation method through theanatomic investigation of the complex ligament of distal tibiofibularsyndesmosis.Methods:6adult lower legs of frozen-fresh specimens were selected.The anterior tibiofibular ligament (ATFL) and posterior tibiofibularligament (PTFL) were carefully observed. The process coruse and therelationships to each others were carefully observed, the preciseanatomical parameters (length, width) of ATFL and PTFL were alsomeasured by divider and vernier caliper (the accuracy of0.02mm).Using Kirschner wires and a protractor measure the angle between eachligament and the coronal plane, and the articular surface of the ankle.Results: In six cases, the average length of upper part of ATFL is8.12±0.65mm, length of lower part19.78±1.69mm, width of ATFL17.45±1.30mm.The average angle between ATFL and Coronal plane is24°±5°, ATFL and ankle joint surface angle is31°±4°. The average lengthof upper part of PTFL is9.77±0.90mm, length of lower part20.35±2.33mm, width of PTFL18.58±1.63mm. The average anglebetween PTFL and Coronal plane is14°±3°, PTFL and ankle joint surfaceangle is18°±2°.Conclusion: Its is by ATFL, PTFL and interosseous ligament (IL)maintained the stability of distal tibiofibular syndesmosis. Fixing deviceis placed from posterolateral fibula to anteromedial tibia. And the medialpart is raised slightly.Part2Biomechanical comparative study on cortical serew, bionicelastic fixing device and double Endo-button system in the treatmentof distal tibiofibular syndesmosis ruptureObjective: To investigate the stability of fixation with3differentinternal fixation devices and intact syndesmosis through thisbiomechanical comparison, with an aim to provide scientific evidence for the clinical use of bionic elastic fixing device on distal tibiofibularsyndesmosis rupture.Methods: Six specimens of frozen-fresh adult cadaveric lower legswere used for analysis. To simulate the clinical injury of the distaltibiofibular syndesmosis by cutting the ligament of the distal tibiofibularsyndesmosis in6cadaveric specimens. We use three type of internalfixation devices by which the injury model was fixed:(1) φ3.5mmcortical serew,(2) bionic elastic fixing device, and (3) doubleEndo-button system. All the holes for placing fixing devices have a samedirection (from posterolateral fibula to anteromedial tibia, coronal angleof25°～30°, tibial elevation10°～15°). The proximal tibia isconnected to the motion unit of Bose ElectroForce3520-AT testingmachine. The strain gages were sticked to distal tibiofibular bone. Wheneach samples’ ankle joint is placed in neutral position, dorsiflexion (10°),plantar flexion (15°), varus (10°), and valgus (15°), we load slowlythe axial force from0to700N, record the displacement of syndesmosisand strain changes of tibia and fibula. In the neutral position and300Nload on each samples’ ankle joint, we give internal and external rotationtorque from0to5Nm, then record the changes. Statistical analysis wasperformed using variance analysis of the randomized block design andSNK test.Results: Whether the specimen bearing load or torque, screwfixation group produced the smallest displacement values, and in mostcases (neutral position, dorsiflexion, varus, plantar flexion of the low load,high load on valgus position, internal and external rotation), were lessthan the other3groups (P<0.05). Although bionic fixed group and doubleEndo-button fixation group get considerable number of displacement, andslightly larger than the intact sample (only very few exceptions), thedifference between them are almost no statistical significance (P>0.05).After fixation, the magnitude of strain changing decreases on tibia(excluding external rotation in twist test), while screw fixation group reducing is most obvious (there are significant differences, excluding theneutral position and dorsiflexion in load test). There are no differencebetween the bionic fixation group and double Endo-button plate group,while the strain on the fibula almost did not change significantly.Conclusion: Fixation with screws through four layers of corticalhinders syndesmosis motion. In the distal tibiofibular syndesmosis injuryoperation, we should choose the bionic elastic fixing device which iscloser to physiological needs for fixation. This device can stably fixsyndesmosis, while retain the motion function of syndesmosis. It isbeneficial to patients with early ankle rehabilitation, promote the functionrecovery, reduce the complications and improve the prognosis.Part3Treatment with bionic elastic fixing device in distal tibiofibularsyndesmosis injuryObjective: To evaluate the clinical and radiological outcomes ofbionic elastic fixing device.Methods: Between June2013and January2014,12patients whohad distal tibiofibular syndesmosis injury were treated with bionic elasticfixing device, included7males and5females, who were aged15to58years old with a mean age37.2±12.3. According to Danis-Weberclassification,5cases of B type, C type in7cases (4type C1,3type C2).According to Lauge-Hansen classification,4cases of Pronation-Eversion,3cases of Pronation-Abduction,5cases of Supination-Eversion. Allpatients were fixed with the bionic elastic fixation device in the same way(from posterolateral fibula to anteromedial tibia, coronal angle of25°～30°, tibial elevation10°～15°).Results: All of them were followed up for5～9months(mean6.5months). Radiological follow-up found1cases healed on8weeks and11cases on12weeks. One patient had full weight-bearing exercise at8weeks after operation,10patients after12weeks. Only one patient haddelayed weight-bearing exercise, as nonunion in other parts of the body.No fixation failure was observed. No joint degeneration, no arthritis signs and no osteolysis was found at radiological follow-up. According toAOFAS score system,8cases were excellent in,3cases were good and1case in general.Conclusion: Bionic elastic fixation device can ensure the stability ofthe ankle joint after surgery. It is demonstrated that bionic elastic fixationdevice for ankle fracture with tibiofibular syndesmosis injury couldrecover the normal motion function and reduce the recovery time, it couldalso avoid the breakage of internal fixation and other complications.