| Background context: Pedicle screw was becoming one of the standard methods of instrumentation in the thoracolumbar fracture. Implant failures of pedicle screw fixation often occurred. Bending, breakage and loosening of instrument were main cause of failures.Objectives: To analyze the biomechanics of pedicle screws, the change of the bone-screw interface was. studiedMethods: Thirty patients with thoracolumbar fracture instrumented with pedicle screws, were followed-up from 1 to 2 years. The change of the bone-screw interface in histology and imaging was. studied, analyzed by spss10.0Results: Inflammation and fibrous tissue formation were the main tissue reaction to the implant. Fibrous tissue was often observed at the bone-screw interface without direct contact of screw and bone. The CT mean value of back screws increased 32.81% and 39.07% than the front and the middle (p<0.05), and there was no significant difference betweenthe mean CT value in screws of the front and the middle.Conclusion:There was high density zone at the bone-screw interface in imaging, the density and the thickness of response bone indicated the biomechanics of screws. As for the biomechanics of screws, the back of screws was the main stress-burden region.The fibrous tissue remained at the bone-screw interface, and it was obvious around the loosening screws. The tissue reaction and inflammation were considered to be one of the main causes of loose. |
