Anatomic study of the semispinalis cervicis for reattachment during laminoplasty

Some patients who had cervical laminoplasty with subsequent substantial loss of cervical lordosis have shown failed healing of a repaired semispinalis cervicis. We also have identified some patients in whom it is difficult to repair the C2 spinous process during laminoplasty. We therefore quantitatively analyzed the morphologic features of the C2 insertion of the semispinalis cervicis and obtained data relevant to the repair of the muscle. In 24 cadavers, the width and height of the semispinalis cervicis insertion in C2 and the length and opening angle of the C2 spinous process were measured. We observed considerable individual variations in the morphologic features of the C2 spinous process and the C2 insertion of the semispinalis cervicis. The opening angle of the C2 spinous process was smaller in males than in females. In most of the cases, the width of the insertion was narrower than the width of the spinous process spacers that commonly are used in laminoplasty. Preoperative prediction of the morphologic features of insertion at the original site is possible by measuring the opening angle of the C2 spinous process using three-dimensional computed tomography because the muscle insertion correlated with the angle of the C2 spinous process. This information may be useful in reattaching the semispinalis cervicis during cervical laminoplasty.