Cervical paraspinal muscle compartment pressure after laminoplasty: A cadaveric study.

Axial neck pain is a common complaint after cervical laminoplasty and the causes are still not well-understood. We hypothesized that abnormal paracervical muscle compartment pressures might be one of them. The cervical paraspinal muscle compartment pressures of 10 cadavers were measured in six different areas under four different conditions. The posterior cervical area was divided into two sides: open side and hinge side. Then each side was divided into upper, middle, and lower areas. The compartment pressures of each area were measured under four different conditions: before and after dissection of posterior paravertebral (paraspinal) muscles, after laminoplasty and after laminoplasty with removal of the spinous processes. There was a statistically significant difference between the pressures after dissection versus after laminoplasty on the hinge side at all upper, middle and lower areas [p < 0.01, <0.001 and =0.009 respectively]. There was a difference in the pressures after laminoplasty between the open and hinge sides [p < 0.001, <0.001 and =0.023 respectively]. We also found the following significant differences: the pressures between before dissection and after laminoplasty on the hinge side, as well as between after laminoplasty and after removal of the spinous process on the hinge side in the upper and middle areas [p < 0.001, =0.0016 and p = 0.002, =0.023 respectively]. Cervical paraspinal muscle compartment pressures on the hinge side were significantly increased after laminoplasty. This may be a contributor to axial neck pain following laminoplasty. The pressure was then significantly decreased after removal of the spinous processes.