Laminar closure rates in patients with cervical myelopathies treated with either open-door laminoplasty with reattachment of spinous processes and extensor musculature or Hirabayashi open-door laminoplasty: a case–control study

Purpose: The presence of preoperative kyphosis has been identified as a risk factor for laminar closure (LC). We have been performing modified open-door laminoplasty with reattachment of the spinous processes and extensor musculature for patients with reduced cervical lordosis because this procedure can prevent progression of cervical kyphosis. This procedure may also prevent LC. The purpose of this study was to evaluate the rate of LC after the modified open-door laminoplasty. Methods: A total of 104 patients who underwent open-door laminoplasty were retrospectively reviewed. Of these patients, 18 underwent modified open-door laminoplasty (group M), whereas the other 86 underwent Hirabayashi open-door laminoplasty (group H). Group H was divided into two classes according to the preoperative cervical lordosis angle (group H1 ≤ 10° vs. group H2 ≥ 11°). All 18 patients in group M had a preoperative lordosis angle ≤10°. The outcomes were assessed using the rate of LC, the cross-sectional area (CSA) of the erector muscle on magnetic resonance imaging, and the Japanese Orthopaedic Association score (JOA score). Results: The rate of laminar closure was significantly lower in group M (39 %) than in group H1 (76 %) (P < 0.01). The CSAs tended to be larger in the muscle preservation side of group M than in the other groups. There was no significant difference in the JOA score among the three groups. Conclusions: Although patients with decreased cervical lordosis have a higher risk of LC, the results suggested that modified open-door laminoplasty could reduce the rate of LC compared with Hirabayashi open-door laminoplasty.