Atrophy of the nuchal muscle and change in cervical curvature after expansive open-door laminoplasty.

We analyzed computed tomography (CT) images and plain X-ray films of 53 patients who had undergone expansive open-door laminoplasty, in a 3-year study. The relationship between the postoperative changes in the nuchal muscles and those in the cervical curvature was investigated. On postoperative CT images, the cross-sectional area of all nuchal muscles was reduced to approximately 80% of its preoperative size. This atrophic change was especially intense in the multifidus muscle and the semispinalis cervicis muscle. Postoperative cross-sectional area of the deep nuchal muscles was reduced approximately 30% from its preoperative size. No significant correlation was found between the all cross-sectional area of the nuchal muscles and the cervical curvature. However, a weak correlation was found between the deep nuchal muscles area and the curve index (correlation coefficient 0.29).