Biomechanical Comparison Of Locking Proximal Humerus Plate Combined With Cannulated Compression Screw And Intramedullary Nail Fixation For Tibiotalocalcaneal Arthrodesis

Background Tibiotalocalcaneal arthrodesis(TTCA)is a procedure to fix both the ankle joint and the subtalar joint,keeping the foot and ankle stable and relieving pain of patients.The methods for fusion include plates,screws,retrograde intramedullary nails(IMNs)and external fixation.TTCA is currently predominantly performed with IMNs,which,however,requires skilled performers as well as it leads to a higher complication rate.Concerning plates for TTCA,locking plates for fixation are superior to blade plates in terms of stability and compression strength and cause a lower complication rate.The objective of the study is to compare the stability of the locking proximal humerus plate(LPHP)combined with a cannulated compression screw for TTCA to the intramedullary nail fixation for TTCA.Methods Acquired six pairs of artificial lower shank models,one model was randomly selected from each pairs respectively for the operation of TTCA with IMN,namely the group of IMN.While the rest was operated for TTCA with LPHP and a compression screw,namely the group of locking plate.Removed the fibula,forefoot and midfoot of each sample,leaving the hintfoot alone,then a 25 cm long sample was obtained by amputating the proximal end of the sample horizontally.The prepared samples were fixed to the biomechanical test machine and compressed axially at the speed of 1mm/min,loading to 700 N force gradually.Meanwhile,recorded the force-displacement curve at a rate of 10 HZ as well as the relative displacement D3 between the distal end of the tibia and calcaneus.The stiffness of samples was calculated to compare the biomechanical stability between the two groups.At the same time,we also contrasted the press capacity of the IMN and that of the LPHP combined with a compression screw.Results Samples did not fail at the end of test.The average stiffness and D3 of samples in the locking plate group was 419.08±20.90 N/mm and 0.10±0.02 mm respectively while the average stiffness and D3 of samples in the IMN group was 569.59±8.78 N/mm and 0.29±0.02 mm.There was statistically significant regarding the two parameters,(t=-16.264,p<0.01)and(t=-14.724,p<0.01).Conclusion Locking proximal humerus plate combined with a compression screw for fixation of TTCA showed lower stability than intramedually nail for fixation of TTCA,which is a better alternative of the procedure,whereas press capacity of the IMN is weaker.Further fatigue endurance test and finite element analysis should be taken into consideration to corroborate the study.