| Objective: By applying the Minimally positioning trephine invasive screw internal fixation of ankle arthrodesis,to determine the safety approach of percutaneous fusion,and what kind of surgery approach is more mechanical advantage,fixed more strong and reliable through biomechanical analysis.Besides measure the ankle fusion area and the percentage of the total ankle dome roof area,so as to provide a reliable basis for clinical choice of fixation.Methods: This experiment chooses 16 adult calf-ankle specimens,all the specimens stored in the refrigerator,and were taken out the day before the experiment,and natural thawed at room temperature.The specimens were randomly divided into two groups A and B,and were numbered.Group B was set as the experimental group,Group A was the control group.Made surgical approach markers on the specimens.Two groups used the same bone graft fusion approach,the first marker was located 2.5-3.0cm ahove the external malleolus,approximately 4.0cm inwardly,with tibial middle line about 15 ° angle.The second marker was located 0.8-1.0cm on the tip of the medial malleolus,at about 4.0cm outwardly,with tibial middle line about 15 ° Angle.Under X-ray fluoroscopy,respectively,from the marked points in the direction of the ankle has reached one guide pin into the ankle joint gap,determine the two needle was located in the central ankle joint,make the core along the guide pin into the ankle joint,and wedge into the ankle joint gap,insert the hollow trephine and twisted it into the joint,control bit depth under X-ray fluoroscopy,then take out the trephine,promote the core like pushing the syringe,then get bone columnar,remove the soft tissue and Articular cartilage of the bone column,the remaining bone for bone graft.Make the bone graft sleeve insert joint gap along the dril,implant the bone into the drill tube,consolidate with bone graft sticks,if the bone is not enough,it requires the allograft bone.Consolidate the ankle after adjust the ankle dorsiflexion maintained at 0 °,eversion 0 °-5 °,5 °-10 ° external rotation position,and keep the talus mild shift back[1].The first marker of group A within the screw internal fixation surgical approach is at 2cm above the ankle joint line,against the inside of the posterior tibial tendon,with one screw down outward direction from the marker screwed into the outer talus pulley.The second marker is at 2 cm above the ankle joint line,close to the lateral extensor digitorum longus,with one screw down inside from the marker screwed into the inner side of the head of the talus.The third marker is located in the leading edge of the tibial,5 cm above the ankle joint line,with one screw from the marker screwed into the front of the processus posterior;The first marker of group A within the screw internal fixation surgical approach is at 2cm above the ankle joint line,against the inside of the posterior tibial tendon,with one screw down outward direction from the marker screwed into the outer talus pulley.The second marker is at 2 cm above the ankle joint line,close to the lateral extensor digitorum longus,with one screw down inside from the marker screwed into the inner side of the head of the talus.The third marker is at 2 cm above the tip of the external malleolus,with one screw screw into from the marker to fix the external malleolus and talus.After fixation was completed,the conduct the biomechanical experiment with the two groups,got the displacement in the axial test,dorsiflexion test,and torsion test after ankle fusion,compared the stability between the two groups.Use vernier caliper to measure the length,width and the radius of the arc after hollow trephine drilled tunnel of the two group.To calculate the area of the tunnel axis,and the percentage of ankle dome area.Results: Through the experiment of 16 specimens,in the torsion test,the torque was±5.0Nm,the frequency was 0.25 Hz,and the 700N’s continuous pressure was applied in the torsion test.under the same torque,the angle displacement of group B was less than that of group A,there is significant difference.In the axial test,a frequency of 0.25 Hz,pressure from 0 gradually loaded to 700 N was applied in the axial test,under the same load,the longitudinal displacement of the group B was shorter then group A,there is significant difference.In the dorsiflexion test,a frequency of 0.5Hz,torque increases from 0 to 50 nm was applied in the test,under the same torque,the displacement of group B was shorter than that of group A,there is significant difference.The above conclusion can be concluded that the stability of the B group is greater than that of the group A,which is more stable and reliable.No articular cartilage was retained in the bone graft tunnel,and the bone was fully filled in the fusion tunnel.In addition,the application of Auto CAD2014(Autodesk company,USA)software to calculate the tibia and axial fusion area of the two groups were(649±34)㎜ 2 and(597±26)㎜ 2,respectively accounting for 70.70% and 65.03% of the ankle dome roof area,more than 50% in both groups.Conclusions:1 Experimental study of ankle joint fusion by minimally invasive percutaneous trephine,it confirmed through the front ankle and medial anterolateral approach,avoiding the ankle important structures.Anteromedial and anterolateral approach were located in 2.5-3.0cm ahove the external malleolus,approximately 4.0cm inwardly,and 0.8-1.0cm on the tip of the medial malleolus,about 4.0cm outwardly,the Angle of the percutaneous trephine with tibia middle line was about 15 ° Angle.The tibia and axial fusion area of the two groups were(649±34)㎜ 2and(597±26)㎜ 2,respectively accounting for 70.70% and 65.03% of the ankle dome roof area,more than 50% in both groups,to ensure the fusion rate of the ankle joint.2 The two groups respectively adopted two different kinds of fixed way,although the group A has achieved satisfactory results in the clinic,but the group B fixation mode can form a stable three-dimensional triangular structure,was more stable and reliable than the group A,besides,the group B has better mechanical advantage and better effect.The two groups were tested with the torsion test,axial test and dorsiflexion test,The fixing strength of the experimental group was significantly better than the control group,there is significant difference. |
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