BACKGROUND:Prosthesis loosening and wear are still the main problems in the failure of total ankle replacement,which are closely related to the micro-motion of the implant-bone interface,the contact stress of the articular surface and joint motion.The design of artificial joint components,including insert and tibial/talar stem prosthesis,is a key factor affecting the force,motion,and micromotion of the contact interface of the ankle joint.The development of new inserts is of great significance to improve the survival rate of artificial ankle joints. OBJECTIVE:The finite element model of the total ankle replacement model was constructed to detect the biomechanical properties of the porous structure-optimized inserts,and the effect of the porous structure-optimized inserts on reducing prosthesis micromotion and improving the contact behavior of the articular surface was analyzed. METHODS:Based on the CT scan data of the right ankle joint of a healthy adult and the INBONE Ⅱ system product manual,a three-dimensional model including bone and artificial joint system was established,and the total ankle replacement model(model A)was obtained after osteotomy and prosthesis installation,and then through four new types of inserts,G50,G60,D50,and D60,were obtained by transforming the porous structure of the original insert,and the original one was replaced with different inserts to establish an optimized total ankle replacement model(models B-E)corresponding to the inserts.The gait loads were applied on the five models to simulate the gait conditions.The differences in micromotion and articular surface contact behaviors at the implant-bone interface of all five models were compared. RESULTS AND CONCLUSION:(1)In the gait cycle,the micromotion of the prosthesis of the four optimized total ankle replacement models was lower than that of the original model.Compared with model A,the micromotion of the prosthesis in models B-E decreased by 5.4%,10.1%,8.1%,and 20.9%,respectively.The high micromotion area of t ??he tibial groove dome in the optimized model was significantly smaller than that of the original model.(2)The four optimized models obtained a larger articular surface contact area.Compared with model A,the average contact area of t ??he inserts in models B-E increased by 11.8%,14.7%,8.1%,and 32.6%,respectively.(3)Similar to the effect of increasing the contact area,compared with the original model,the contact stress of the optimized model decreased in varying degrees,and the value of model E decreased the most significantly(P<0.05),it is due to good mechanical properties and large porosity of the Diamond lattice that constitutes the D60-type insert.(4)The research results show that the use of porous structure to improve the inserts can improve the elasticity of the inserts and increase its ability to absorb joint impact,for favorable conditions are created for reducing micromotion at the implant-bone interface and improving joint contact behavior.

OBJECTIVETo observe the influence of betahistine on the expression of histamine H3 receptor in the medial vestibular nucleus (MVN) following unilateral labyrinthectomy (UL).

METHODSFifty-six healthy guinea pigs were randomly divided into three groups:the sham-operated group (group I), the UL group[group II, and UL+betahistine (BET) group (group III)], BET was intraperitoneally injection at 2.17 mg×kg(-1)×d(-1) for 7 days. The expression of histamine H3 receptor was analyzed by immunohistochemistry at 1 day, 3 days and 7 days after UL.

RESULTSH3 receptors were presented in the MVN and the expression of histamine H3 receptor were increased significantly in the ipsilateral MVN at 1 and 3 days after UL(P < 0.05), the change turned into the normal value at 7 days(P > 0.05). In the UL+BET group, the intensity of histamine H3 receptor was lower than that in the UL at 1 day and 3 days(4.25 ± 0.71, 3.50 ± 0.92 vs 5.75 ± 0.71, 5.50 ± 0.93, P < 0.05). However, the changes turned into the normal values at 3 and 7 days (P > 0.05).

CONCLUSIONSThe early stage of the vestibular compensation process may be associated with the change of H3 receptor expression in MVN. In the UL+BET group the histamine H3 receptor recovered quickly.

Animals ; Betahistine ; metabolism ; Ear, Inner ; Guinea Pigs ; Otologic Surgical Procedures ; Receptors, Histamine H3 ; metabolism ; Vestibular Nuclei ; metabolism ; Vestibule, Labyrinth ; surgery

OBJECTIVE: To discuss the influence of artificial ankle elastic improved inserts (hereinafter referred to as "improved inserts") in reducing prosthesis micromotion and improving joint surface contact mechanics by finite element analysis. METHODS: Based on the original insert of INBONE Ⅱ implant system (model A), four kinds of improved inserts were constructed by adding arc or platform type flexible layer with thickness of 1.3 or 2.6 mm, respectively. They were Flying goose type_1.3 elastic improved insert (model B), Flying goose type_2.6 elastic improved insert (model C), Platform type_1.3 elastic improved insert (model D), Platform type_2.6 elastic improved insert (model E). Then, the CT data of right ankle at neutral position of a healthy adult male volunteer was collected, and finite element models of total ankle replacement (TAR) was constructed based on model A-E prostheses by software of Mimics 19.0, Geomagic wrap 2017, Creo 6.0, Hypermesh 14.0, and Abaqus 6.14. Finally, the differences of bone-metal prosthesis interface micromotion and articular surface contact behavior between different models were investigated under ISO gait load. RESULTS: The tibia/talus-metal prosthesis interfaces micromotion of the five TAR models gradually increased during the support phase, then gradually fell back after entering the swing phase. The improved models (models B-E) showed lower bone-metal prosthesis interface micromotion when compared with the original model (model A), but there was no significant difference among models A-E ( P>0.05). The maximum micromotion of tibia appeared at the dome of the tibial bone groove, and the ​​micromotion area was the largest in model A and the smallest in model E. The maximum micromotion of talus appeared at the posterior surface of the central bone groove, and there was no difference in the micromotion area among models A-E. The contact area of the articular surface of the insert/talus prosthesis in each group increased in the support phase and decreased in the swing phase during the gait cycle. Compared with model A, the articular surface contact area of models B-E increased, but there was no significant difference among models A-E ( P>0.05). The change trend of the maximum stress on the articular surface of the inserts/talus prosthesis was similar to that of the contact area. Only the maximum contact stress of the insert joint surface of models D and E was lower than that of model A, while the maximum contact stress of the talar prosthesis joint surface of models B-E was lower than that of model A, but there was no significant difference among models A-E ( P>0.05). The high stress area of the lateral articular surface of the improved inserts significantly reduced, and the articular surface stress distribution of the talus prosthesis was more uniform. CONCLUSION Adding a flexible layer in the insert can improve the elasticity of the overall component, which is beneficial to absorb the impact force of the artificial ankle joint, thereby reducing interface micromotion and improving contact behavior. The mechanical properties of the inserts designed with the platform type and thicker flexible layer are better.
Adult ; Male ; Humans ; Ankle ; Ankle Joint/surgery* ; Finite Element Analysis ; Tibia/surgery* ; Talus ; Stress, Mechanical ; Biomechanical Phenomena