Research Of Digital Rapid Prototyping Technology Application In Individualized Treatment About Foot-drop Caused By Common Peroneal Damage

Background:With the coming of precision medical era,digital medicine has been developed rapidly through integrating information science technology with medicine.Digital medicine has influenced every aspect of medical science,and improved the development and level of medicine.The orthopedic surgery in the department of orthopedics also has stepped into the digital age.By studying the biomechanics of ankle and foot with finite element analysis has significant meaning in the treatment and prevention of injury and surgical reconstruction.Additionally,it also has guiding value for the patients with postoperative rehabilitation training.Objective:To reconstruct the three-dimensional finite element model of foot,ankle bones and tendons in patients with foot drop caused by common peroneal nerve injury.Then to carry out surgical simulation of tendon transposition with the model and analysis of mechanical characteristics.Therefore,this model would give significant guidance in operation and prognosis,and also provide a feasible and precise medical mode for young orthopedic doctors.Methods:1.In order to reconstruct foot and ankle bones with a series software,such as MIMICS,Cero,Abaqus,ANSYS,CT data of a male patient with left foot drooping caused by left common peroneal nerve injury was collected and imported in the software;2.Ten young male volunteers with proportioned physiques and without leg disorders were enrolled.Their muscle strength were measured by electrical trigger potentiometer and the Root mean square amplitude of surface EMG – RMS were calculated;3.To establish the finite element model of the normal foot by limiting material parameters of every part and ultimate angles of four directions of the ankle joint;4.Based on this model,we assumed that the muscle strength of the common peroneal nerve innervated was 0,then simulated the foot drooping state caused by total injury of the common peroneal nerve;5.The posterior tibial tendon transposition,Entocuneiform,Mesocuneiform and Ectocuneiform were identified as the tendon anchored points,the foot was fixed at dorsiflexion position 100 through the transferent tendon,and the tibialis posterior muscle strength would drop one level after the transposition;6.The analysis and calculation of Finite element on the two droop states of three different anchoring positions showed the ankle dorsiflexion angles,internal and external rotation angles and the maximum stress of the transposition of the tendon which were calculated under these six conditions.Results: Biomechanics Finite element model of ankle and foot preliminary simulated the normal foot,dropped foot dorsiflexion and plantar flexion state.That showed great significance to the understanding of mechanical characteristics of ankle foot and would give guidance to treatment and evaluation of prognosis.The design of the tendon transposition of the dropped foot surgery was performed around these different anchored positions.The comparison in various cases showed: tendon transposition anchored on the Mesocuneiform had maximum correction angle and minimum stress of the tendon;tendon transposition anchored on the Ectocuneiform had the worst effect of correction of deformity and maximum stress of the tendon compared to the other two.Making Mesocuneiform as anchor point,then better mechanical effects can be obtained by posterior tibial tendon transposition surgery in the treatment of foot drop.Whether it was normal foot,dropping foot or the foot after tendon transposition operation,the tendon stress concentrated in the contact surface of the tendon and bone,suggesting that this position was weak to be damaged,even avulsion fracture.It should be strong fixed during surgery and protected by plaster after operative until the formation of tendon bone healing.Conclusion:1.The ankle biomechanical model established by the finite element can simulate normal foot and drop foot;2.Making Mesocuneiform as anchor point means better orthopedic effect about drop foot;3.The stress concentration point of the transposition tendon lies in the contact surface of the tendon and bone,and it should be firmly fixed during the operation.