Open door expansive laminoplasty and postoperative axial symptoms: a comparative study between two different procedures

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Abstract
Study design: Retrospective cohort Objective: To determine if there are differences in important clinical outcomes between patients treated with a „preservation of the unilateral posterior muscular-ligament complex (PMLC) procedure” and a „hinge side anchoring procedure (HSAP)” for the treatment of cervical spondylotic myelopathy (CSM). Methods: Nine hundred and forty-six patients underwent the above procedures for treatment of CSM between January 2006 and December 2009. Five hundred and fifty-two (58 %) subjects met study criteria and 136 were analyzed (76 % unavailable for follow-up). One group (70 patients) received a „preservation of unilateral PMLC procedure” and another group (66 patients) received an HSAP. The rate and severity of postoperative axial symptoms were assessed, and the changes of cervical-spine curvature and postoperative decompression were measured. Results: The mean time to follow-up in the preservation of unilateral PMLC group was 6.9 months (range, 6–8 months) and the HSAP group was 6.4 months (6–8 months). The overall rate of any axial symptoms (AS) among all subjects was 35 %. No AS was reported in 45.7 % of the preservation of unilateral PMLC group and 23.8 % of the HSAP group (P = .008). Severe AS was reported in 4.3 % and 11.1 % of patients per group, respectively (P = .14), (Table [ 2 ]). Cervical spinal lordosis was improved in the unilateral PMLC group and decreased in the HSAP group. The risk of losing lordosis was more than two times higher in the HSAP group compared with the unilateral PMLC group (70 % and 34 %, respectively; P < .001). Conclusion: Differences were observed between the two groups; however, a high loss to follow-up rate weakens the findings. Cervical expansive laminoplasty with preservation of unilateral PMLC may have the advantage of a lower rate of postoperative AS and maintenance of cervical spinal lordosis compared with the HSAP group. STUDY RATIONALE Postoperative AS are well described major and long-term complications of cervical laminoplasty for CSM. The overall incidence ranges from 6 % to 60 % 1, 2. The incidence and severity of AS appears to vary among different types of laminoplasty procedures. Further, various procedural approaches to the cervical spine may affect alignment, influence quality of decompression, as well as impair stability of the PMLC postoperatively 2, 3, 4, 5. OBJECTIVE To determine if there is a difference in; (1) the rate and severity of postoperative AS; (2) the change of cervical spine sagittal alignment; and (3) spinal cord decompression between patients treated with a preservation of the unilateral PMLC procedure and HSAP for the treatment of CSM. METHODS Study design: Retrospective cohort study. Inclusion criteria: We included all patients with CSM and presence of the following clinical conditions: three or more segments of spinal-cord compression developmental and degenerative stenosis of the cervical spine +/- ossified posterior longitudinal ligament age 30–75 years presence of both preoperative and postoperative clinical and radiological examinations including x-ray and magnetic resonance imaging (MRI) scans. Exclusion criteria: Patients were excluded if they had: previous cervical spine surgery ankylosing spondylitis congenital deformities severe osteoporosis cerebrovascular disease sequela motor neuron disease, or neuromuscular junction disease required simultaneous instrumented fusion or combined anterior procedures Patient population: Nine hundred and forty-six patients underwent one of two cervical laminoplasty procedures between January 2006 and December 2009. Of these, 394 (41 %) did not meet study criteria. There were 552 patients eligible for the study; however, 203 (37 %) did not have either radiology or clinical details in the follow-up records and 213 (39 %) did not return for follow-up. The remaining 136 of those eligible (24 %) were analyzed (Fig 1). Interventions: Seventy patients received preservation of unilateral PMLC procedures (Fig 2) and 66 received HSAP” (Fig 3). The decompression segments were distributed from C2 to T1. The procedure was performed according to each surgeon’s preference. There was no reason to believe that one procedure was selected over another based on disease severity. Outcomes: The existence and severity of AS were measured and graded at final follow-up according to Kawaguchi’s description 6 and Hosono grading system 7 by one of the investigators: No AS: not any axial symptoms at all Minor AS: slight symptoms which do not affect activities of daily living Major AS: obvious symptoms and occasional analgesic pain medication may be required Severe AS: very obvious symptoms that affect patient’s activities of daily living, regular analgesics are taken. The change of sagittal cervical spinal alignment was measured using the Ishihara 8 method by one of the investigators. The expansive effect was evaluated by measuring the diameter of spinal canal on standard lateral view x-rays. A description of these methods can be found in the web appendices at www.aospine.org/ebsj. Spinal cord decompression was measured using MRI, when available, by evaluating the appearance of the dura sac and the paraspinal muscles. Analysis: Categorical baseline and outcome variables were compared using a Pearson Chi-square test. Continuous baseline variables, between group changes in preoperative to postoperative changes in cervical spine curvature and preoperative to postoperative changes in the expansive effect were compared using a 2-tailed independent t-test. Within group changes in preoperative to postoperative changes in cervical spine curvature and preoperative to postoperative changes in the expansive effect were...