Experimental Study On Internal Fixations For The Fractures Of Distal Femurs With Computer Assisted Orthopedic Surgery System

PartⅠObservation and Measurement of Femoral CondyleObjective:To observe and measure the femoral condyle for internal fixations for the fractures of distal femurs.Methods:86 femurs were obtained and can be studied.9 parameters of the femoral condyle were obtained,including the anteroposterior diameter of lateral condyle(X1),the depth of anterior patellar groove(X2),the anteroposterior diameter of patellar groove(X3),the depth of intercondylar fossa(X4),the height of lateral condyle(X5),the depth of lower patellar groove(X6),the depth index of anterior patellar groove(X2/X1),the depth index of intercondylar fossa(X4/X1)and the depth index of lower patellar groove(X6/X5).The distribution and relationship of the data were analyzed statistically.Results:The femoral condyle is irregular bone,and each part has some morphological character.X1:57±4.7mm,X2:6.3±2.3mm,X3:23.1±2.9mm,X4:28.1±3.0mm,X5:35.8±4.8mm,X6:8.7±1.1mm.X2/X1:0.109±0.040(95%reference range 0.032-0.199),X4/X1:0.488±0.028(95% reference range 0.431-0.549),X6/X5:0.246±0.033(95%reference range 0.198 -0.323).There is correlation between X1and X2 or X4,There is no correlation between X1 and X2/X1 or X4/X1;There is correlation between X5 and X6,and between X5 and X6/X5.Conclusions:1.It's useful for operation of internal fixations for the fractures of distal femurs to observe and measure the femoral condyle;2.It's the first time to study the depth index of anterior patellar groove,the depth index of intercondylar fossa and the depth index of lower patellar groove.And the parameters is very useful for accurate location and orientation for operation of internal fixations for the fractures of distal femurs.PartⅡExperiment of Internal Fixations for The Fractures of Distal Femurs with Computer Assisted Orthopedic Surgery SystemObjective:To investigate the methods and application value of CAOSS (computer assisted orthopedic surgery system)in the internal fixations for the fractures of distal femurs.Methods:33B1 and 33C1 fracture models were produced according to different fixation methods.And integrated models were made of the fracture models(or the intact femurs)and polymeric sponge.Three cancellous screws were fixed in each of 33B1 fracture models with conventional method or CAOSS randomly.DCS(Dynamic Condylar Screw)and two cancellous screws were fixed in each of 33C1 fracture models with conventional method or CAOSS randomly.DFN(Distal Femoral Nail)was fixed in each of intact femur models with conventional method or CAOSS randomly.Several indexes were noticed and analyzed statistically.Results:The additional time using CAOSS:time for disposition and connection of machines is 363±26s,time for starting machines is 434±4s,time for one X-ray fluoroscopy is 110±28s.The accuracy of the methods to measure the length of screw path:the measurements of the two methods(by virtual probe and by orthopedic depth finder)are not significant different(P＞0.05),but both are significant different from the measurements of the triangular compasses(P＜0.05),especially during measuring the screw path in femoral condyles,and the errors are 4.4±2.6mm and 3.3±1.9mm.During the fixations of cancellous screws,the rate of fault drilling and the angle of screw deviation with CAOSS are significant smaller,and the disposition of screws is significant reasonable (P＜0.05).During the fixations of DCS,the changed femoral condyle-shaft angle is significant smaller with CAOSS(P＜0.05).During the fixations of DFN,the rate of fault drilling of distal locking is 0%with CAOSS,and 11.8% with the conventional method;the time of locking is significant different between two methods(P＜0.05)Conclusions:1.CAOSS can be used for the internal fixation for the fractures of distal femurs with the advantages,such as safety,accuratissime, less exposure;2.It's useful for location with CAOSS according to the morphological character of femoral condyle.