Cyclic loads do not compromise functionality of the interspinous spacer or cause damage to the spinal segment: an in vitro analysis.

STUDY

DESIGN

A biomechanical study to evaluate the effects of interspinous spacer under cyclic complex loading.

OBJECTIVES

To determine the risk of device migration and to assess damage on the device and specimen under extreme coupled motion. Another objective was to evaluate the effect on vertebral foramen and canal dimensions after spacer implantation.

SUMMARY OF BACKGROUND DATA: Interspinous spacers are a relatively new treatment option that are clinically exposed to complex loads. However, the biomechanical performance of these spacers has not been well characterized.

METHODS

Six human cadaveric motion segments were used for this study. The interspinous spacer (SuperionTM, Vertiflex Inc, California) was tested for 5 degrees extension/10 degrees flexion coupled with an axial rotation of +/-3 degrees. CT images were taken for specimens in neutral, 5 degrees extension, and 10 degrees flexion before and after the implantation of the spacer. Vertebral foramen and canal dimensions were quantified.

RESULTS

There was no device migration or subsidence. Specimens did not sustain any significant injury during testing. Canal area was minimally altered and foramen height, width, and area increased in extension and were statistically significant as compared to intact.

CONCLUSION

Interspinous spacer effectively prevents the motion at the implanted level and does not change the anatomy significantly.