Biomechanical Characteristics of Kissing Spine During Extension Using a Human Cadaveric Lumbar Spinal Model.

Introduction: Although kissing spine syndrome in the lumbar spinal region is a relatively common condition in older adults, no study examining its biomechanical characteristics has been reported. We hypothesized that kissing of the spinous processes during extension causes an increase in the flexural rigidity of the spine and significantly limits the deformation behavior of extension, which in turn might cause lower back pain. Methods: Three test models (human cadavers A, B, and C) were prepared by removing supraspinal/interspinous ligaments between L4 and L5. The dental resin was attached to the cephalocaudal spinous process so that the spinous processes between L4 and L5 were almost in contact with each other to simulate the condition of a kissing spine. The flexion-extension direction's torque-range-of-motion (torque-ROM) curve was generated with a six-axis material tester for biomechanical measurements. Results: In all three models, the maximum ROMs at the time of extension were smaller than those at the time of flexion, and no sudden increase in torque was observed during extension. Conclusion: The results indicated no apparent biomechanical effects of kissing between the spinous processes, suggesting that the contact between the spinous processes has little involvement in the onset of lower back pain.