The biomechanical study of minimally invasive technique for transverse patella fracture

Objective To evaluate the biomechanical strength and stability minimally invasive tension band method for treating transverse patella fracture.Methods Cadaver extremities with quadriceps tendon-patella tendon and an intact capsular apparatus were studied.Transverse osteotomies of the patella were performed and simulated fractures were fixed with three techniques,including either open or minimally invasive method of pin tension band,cancellous bone screw tension band or biodegradable tension band technique.The tibia and femur were mounted in an Instron Testing System,and the tibiofemoral joint was held at 36 degree of flexion.Tension was applied to the patella through the quadriceps tendon and fracture displacement was measured with linear motion transducers.The stability of patella under either elongation or fatigue circulation of accumulation load was tested.The internal fixation was considered failure when fracture gap exceeding 1 mm.Results All techniques functioned adequately under 500 N loading of quadriceps tendon,and the gap was less than 1 mm in each method.All of them could bear tensile force over 294 N and may provide sufficient fixation to allow immediate range of motion.There was no significant difference in miniinvasive technique and open technique either before or after fatigue (P 0.05). However,the cancellous bone screw tension band had strong fixation and good stability (P 0.05). Conclusion According to biomechanical principal,the minimally invasive tension band internal fixation treating patella fractures can fits the stability needs of fracture heal,and provides sufficient fixation to allow immediate range of motion.