| Objective:The fibula fracture is one of the common extremities fractures,which accounts for10%-15%of all the extremities fractures. Due to directforce,it mostly can be seen in children and young adults. Delayed–union ornon-union always occurs in middle and lower fibula fracture.The distaltibiofibular syndesmosis rupture is a common injury in ankle fractures ordislocation. External rotation force is the most important injury mechanism forthe rupture. When the force is high enough or accompanied with footabduction,with the interosseous membrane involved, the main ligamentsaround the syndesmosis are damaged resulting in the syndesmosis rupture.The general treatment methods of the middle and lower fibula fracturecombined with the distal tibiofibular syndesmosis rupture are externalfixations,such as making a plaster cast or a splint and internal fixations,suchas using screws, bone lock-bolts or plates. The effects of these methods aredifferent and the shortcomings of these methods are also existed, forinstance,the unstable fixation, the failure of fixation, the activity limitation,the malalignment, limited indications, or even causing instability of the anklejoint, traumatic arthritis and stiff ankle joint etc. There is no consolidatedstandard of internal fixation to the domestic orthopaedic doctors in operations.Some doctors use lag screws and plate to fix the injury, and some doctors putthe lag screws through the plate. There is no evident biomechanical theoreticalproof to compare the two internal fixation methods.Our study aimed to assess the effect of the two internal fixationmethods(whether the lag screw goes through the distal hole of the plate)on theartificial cadaver models of the middle and lower fibula fracture combinedwith the distal tibiofibular syndesmosis rupture by analyzing the data from the biomechanical experiments.Methods:16cadaver legs were collected from the Trauma andEmergency Center of the3rdHospital of Hebei Medical University from May2013to February2014.We made16cadaver leg specimens with intacttibiofibular interosseous membrane, anterior inferior tibiofibular ligament,posterior inferior tibiofibular ligament and intact talus and ligaments aroundthe ankle joints. We put the specimens on the BOSE biomechanical machineto proceed vertical compress experiments and torsional experiments. Thevertical compress experiment was to add force on the base of thebiomechanical machine through the cadaver leg specimens to the maximumload of700N by the velocity of25N/s. Recorded the width of the markedposition above the ankle joint by1cm. The data must be recorded twice whenthe force was increased by100N by using a vernier caliper. The torsionalexperiment was to rotate the legs externally by using the BOSE biomechanicalmachine to the maximum rotation degree of20°by the velocity of0.2°/s andrecord the torque.First of all, we did the experiments on the intact cadaver leg specimens,and record the width and the torque. Then we made cadaver models of themiddle and lower fibula fracture combined with the distal tibiofibularsyndesmosis rupture by cutting off the TFIOM, the AITFL,the PITFL andsawing off the middle and lower fibula. There were two internal fixationmethods to those cadaver models. The first one was to place one quadricorticallag screw on the position of3cm above the ankle mortise from the fibula tothe tibia，and place one7-hole LCP on the posterior-lateral aspect of thefibula(3locking screws on each side of the fracture line). The second methodwas to place one8-hole LCP on the posterior-lateral aspect of the fibula(thelast hole was on the position of3cm above the ankle mortise, drive aquadricortical lag screw through that hole,3locking screws on each side ofthe fracture line). We performed the two experiments on those two kinds ofmodels individually, and recorded the width and the torque.We used the SPSS to analyze the experimental statistics by using the independent-samples T test.Result:The experimental statistics of the three groups were in accordancewith the homogeneity test of variance and normal distribution test. Theaverage width of the three groups (±s)were:①the group of intactspecimens(63.790±0.185）mm②the group of the first internal fixation methodto the model（64.174±0.219）mm③the group of the second internal fixationmethod to the model（63.816±0.265）mm. There was no significant differencebetween①group and③group(P＜0.05). However,the statisticalsignificance of the width between②group and①,③groups were evident(P＞0.05). The results showed that the effect of the second internal fixationmethod is superior to the first internal fixation method for the tibiofibularsyndesmosis. The average torque of the three groups(±s) were:①the groupof intact specimens(11.866±7.217）Nm②the group of the first internal fixationmethod to the model（10.044±6.535）Nm③the group of the second internalfixation method to the model（11.240±6.976）Nm. There were no significantdifferences of the torque between the three groups by using theindependent-samples T test(P＞0.05). The results showed that theanti-rotational effect of the two internal fixation methods were equal.Conclusion:It has become a consensus to cure the middle and lowerfibula fracture combined with the distal tibiofibular syndesmosis rupture byusing plates and screws. When the lag screw is drived through the hole of theplate from the fibula to tibia, the strength of the internal fixation method isequal to the normal body. If the lag screw is not drived through the hole of theplate,the strength of the internal fixation method is inferior to theabove-mentioned method. However, the anti-rotational ability are equalbetween the two methods and the normal body. |
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