The Kinematics Study Of Intramedullary Nail And Fragments Based On Computed Tomography After Operation Of Intertrochanteric Fractures

Intertrochanteric fracture is one of the most common fractures in the elderly.It has been estimated that the number of intertrochanteric hip fractures worldwidewill increase from1.6to6.3million per year by the year2050. Because mostpatients with intertrochanteric hip fracture are elderly, operative treatment hasbecome an effective way to reduce mortality. In recent years, with theintramedullary nail applied increasingly wildely in the treatment ofintertochanteric fractures, the relevant mechanical failure and postoperativecomplications are also gradually caused the attention of the orthopaedic surgeon.Many scholars have studied the kinematics of intramedullary nail after operationof intertrochanteric fractures. Subject to the conditions,previous studies have beenconducted based on X-rays. By establishing a new measuring method based oncomputed tomography, this study analyze the kinematics of intramedullary nailand fragments after operation of intertrochanteric fractures and related factors, toinvestigate the reason of mechanical failure and complications of intramedullarynail.Objective: The aim of this study is to establish a new measuring methodbased on computed tomography with higher accuracy and precision to study thekinematics and relevant factors of intramedullary nail and fragments afteroperation of intertrochanteric fractures.Method: Collect general information and radiographs of53patients withintertrochantric fracture who were received the treatment of intramedullary nailin PLA general hospital between September2009and November2013. Theradiographs included preoperative, postoperative CT immediately and after3 months. Postoperative CT and the software of Mimics16.0were applied tomeasure lateral migration with telesoping and the movement of Intramedullarynail on the defined first and second plane. Investigate the kinematics of theintramedllary nail after operation and analyze its relationship with age, gender,type of internal fixation, fracture stability, the quality of reduction and integrity ofthe first plane.Result:The lateral migration with telescoping was-1.09（-2.60,-0.17）mm.The movement of the intramedllary nail was-0.3（-1.52,0.43）mm on the firstplane and-0.21（-1.03,0.36）mm on the second plane, respectively. There was nosignificant correlation between age, gender, fracture stability, the quality ofreduction and kinematics of intramedullary nail and fragments after operation ofintertrochanteric fractures (P>0.05). The integrity of the first plane had asignificant correlation with the lateral migration with telescoping and themovement of the intramedllary nail on the second plane （P<0.05).Conclusion:1.There was no significant correlation between age, gender ofthe patients and the kinematics of intramedullary nail.2.Fracture stability basedon the AO classification had no significant correlation with the kinematics ofintramedullary nail. Currently method of evaluating the quality of reduction couldnot accurately predict the movement of intramedullary nail after operation. Theintegrity of the first plane could be used as a predictor of the lateral migrationwith telescoping and postoperative intramedullary nailing movement.