Biomechanical analysis of a novel percutaneously placed low profile interspinous device

English Keywords:Lumbar spine  Interspious implant  Percutaneous  Biomechanicas

English Abstract:

  【Abstract】　Objective：To investigate the influence of the interspinous spacer implant on the kinematics of the lumbar spine.Method：Six cadaver spine functional units（L1-L5） were observed.The muscles were removed while the discs，ligaments and joint capsules were intact.The cranial portion of L1 and caudal portion of L5 vertebrae were secured in polymethylmethacrylate（PMMA）.Specimens were initially tested by applying a 400N axial compression，followed by a ±7.5Nm bending moment in six directions（lexion and extension，left and right axial rotation，and left and right lateral bending） with a speed of 0.5°/s.The range of motion（ROM） at L2/3 and L3/4 of the intact group was measured，while the ROM at the L3/4 was measured after the Bullet interspinous device was placed.After the measurement，force was imposed with a frequency of 2Hz.Flexsion and extension were done 20000 time，lateral flexion was done 15000 times，and rotation was done 5000 times.X-ray was taken to see the positions of the implants，whether there was fracture of the spinous processes，whether the implants were deformed or broken.Result：The ROM in flexion-extension of L3/4 at intact state was 4.62°±2.26° and 4.07°±1.92° respectively.The ROM in flexion-extension at the instrumented level was 3.87°±2.06° and 2.57°±2.06°，the ROM of both groups in flexion-extension were significantly different（P<0.05），whereas there was no significant effect on the other directions.The novel device had the ability to resist fatigue.Conclusion：Similar to other interspinous implants，the novel percutaneously placed low profile inter-spinous device has an effect on the control of flexibility of the treated segments.It can provide spine stabilization while in extension，but has little effect on the range of motion in flexion，lateral bending and axial rotation.