The source of axial pain after cervical laminoplasty-C7 is more crucial than deep extensor muscles

Study Design. Prospective study to investigate the incidence of axial pain in the 3 different procedures of laminoplasty. Objective. To inquire which is more important in the development of axial pain after laminoplasty: C7 or deep extensor muscles. Summary of Background Data. The etiology of axial pain remains largely unknown. Some surgeons have attempted to preserve the paravertebral muscles with innovative procedures of laminoplasty and thereby reduce the incidence of axial pain. Meanwhile, we have reported that axial pain can be prevented by avoiding inclusion of C7 in laminoplasty. Methods. There were 91 patients with myelopathy who underwent our original laminoplasty, in which the deep extensor muscles were completely preserved exclusively on the hinged side. Until 2001, all candidates for laminoplasty underwent this procedure from C3-C7 (left-opened C3-C7 group, n = 37). From 2002, the same procedure was performed from C3-C6 (left-opened C3-C6 group, n = 31). From 2004, the opened side was changed from left to right (right-opened C3-C6 group, n = 23). Axial neck pain was graded as severe, moderate, or mild. Early pain during the first month after surgery and late pain during the first year after surgery were investigated. The laterality of early pain in the C3-C6 groups was recorded. Results. Significant early pain graded severe or moderate was observed in 49% in the left-opened C3-C7 group, but 15% in the left- or right-opened C3-C6 groups (P = 0.0008). Significant late pain was noted in 30% in the left-opened C3-C7 group and in 5.6% in the C3-C6 groups (P = 0.0036). Early axial pain, which usually was mild, was predominantly observed on the opened side in the C3-C6 groups. Conclusion. To prevent axial pain, C7 should not be included in cervical laminoplasty, while detachment of the deep extensor muscles does not result in significant axial pain.