To investigate the clinical efficacy of modified open-door laminoplasty with preservation of the unilateral paraspinal muscle ligament complex in treating ossification of posterior longitudinal ligament (OPLL) of the cervical spine.

From June 2015 to July 2017, thirty-two patients with OPLL of the cervical spine who underwent modified open-door laminoplasty with preservation of the unilateral paraspinal muscle ligament complex were retrospectively analyzed (modified group). There were 20 males and 12 females with the average age of 61.72±8.41 years (range 46-75 years). The de-compression segment range included three cases of C₂-C₆, seven cases of C₂-C₇, eight cases of C₃-C₆, and fourteen cases of C₃-C₇. Moreover, twenty-three patients with OPLL of the cervical spine who underwent traditional unilateral open-door laminoplas-ty at the same time were included as controls (control group). The demographics, operation duration, and blood loss volume was recorded. The visual analogue scale (VAS), Japanese Orthopaedic Association scores (JOA), improvement rate of JOA score and neck disability index (NDI) were recorded and analyzed at preoperation, three months after operation, six months af-ter operation and at the final follow-up. The cervical curvature, cervical curvature index (CCI), range of motion (ROM) were measured and statistically analyzed on the lateral X-ray film of the cervical spine. The union rate of the lamina hinge and that of spinous process-lamina was measured on the cross section of the CT scan. Bilateral cervical posterior muscle volume was re-corded and analyzed at cross-section plane on MRI. Axial symptoms, C₅ nerve root palsy and other complications were also re-corded.

All the patients were followed-up for 6 to 18 months (mean, 13.04±4.67 months in control group, 11.81±4.93 months in modified group). At the final follow-up, the JOA, VAS and NDI scores improved from preoperatively 6.09±0.79 to 13.43±1.53, 4.22±1.04 to 2.83±1.15 and 25.48%±3.20% to 8.83%±5.41% in the control group, versus 6.28±1.05 to 13.88±1.48, 4.09±1.00 to 1.16±0.57 and 25.06%±3.24% to 5.66%±2.46% in the modified group. The postoperative JOA score and recovery rate of the two groups was not significantly different, whereas the VAS and NDI scores were significantly reduced in the modified group compared to the control group. The maximum cervical flexion angle, cervical curvature, ROM and CCI of control group were 6.26°±3.31°, 30.17°±4.56°, 11.39°±1.95° and 9.74%±4.05% at the final follow-up, which were reduced significantly compared to pre-op-eration. The maximum cervical flexion angle, cervical curvature, ROM and CCI of modified group were 10.06°±1.93°, 35.03°±5.01°, 17.03°±2.86° and 14.22%±5.00%, and there were no significant differences compared to pre-operation. There were signifi-cant differences among two groups. At the final follow-up, the posterior muscle volume of the two groups at open side was de-creased compared to preoperation, but there was no significant difference between the two groups. At the last follow-up, the posteri-or muscle volume at hinge side was not changed compared to preoperation in modified open-door laminoplasty group, while the vol-ume of the posterior muscle at hinge side in the traditional control group decreased compared to preoperation. The difference was statistically significant. A total of eight patients with axial symptom were present after operation. There were two patients (6%, 2/32) in the modified group and six patients (26%, 6/23) in the control group. The difference of axial symptoms incidence was statisti-cally significant between the two groups.

Modified open-door laminoplasty with preservation of the unilateral para-spinal muscle ligament complex is an effective technique in treating OPLL of the cervical spine. The technique not only guaran-teed to have good recovery of neurological function and to maintain cervical curvature and range of motion, but also contributed to decrease the occurrence of postoperative axial symptoms.

Cervical vertebrae; Ossification of posterior longitudinal ligament; Decompression, surgical