Accuracy of Bony Gutter Placement in Cervical Laminoplasty Assisted by 3-D Print Modeling, and Associations with Posterior Spinal Cord Shift and Radiculopathy

INTRODUCTION: We evaluated the positioning of the bony gutter (PBG) in cervical laminoplasty aided by three-dimensional (3-D) printed models, and assessed associations between PBG accuracy¸ posterior shift of the spinal cord (PSSC), and clinical results. METHODS: Of 35 patients who underwent cervical laminoplasty for cervical myelopathy between January 2013 and September 2015, 20 were treated using a conventional free-hand technique (Group A). For the other 15 patients (Group B), surgeons also used 3-D printed models to select a PBG on the edge of the medial aspect of the zygapophyseal joint to maximize the angle of the opened lamina (AOL). We measured the PBG and AOL on axial computed tomography images, and the PSSC on midsagittal magnetic resonance imaging obtained before and 7 days after surgery. Clinical outcomes were evaluated by Japanese Orthopaedic Association (JOA) scores and recovery rates, and by the incidence of postoperative radiculopathy. We compared the PBG, AOL, PSSC, and clinical outcomes between the groups. RESULTS: The PBG was significantly lower in Group B than in Group A at the C4 left and right sides (P = 0.033, P < 0.0001) and C6 left side (P = 0.004), and the AOL was larger at the C4 right side, C5 left and right sides, C6 left side, and C7 right side (P = 0.040, 0.043, 0.016, 0.016, and 0.027, respectively). Group B had a higher percentage of on-target PBGs at the right sides of C4 and C5 and the left side of C7 (P = 0.005, 0.037, and 0.028), a larger PSSC at C4 and C5 (P = 0.023, 0.008), and a higher incidence of radiculopathy (P = 0.026). Groups A and B did not differ significantly in JOA score or recovery rate. CONCLUSIONS: Three-dimensional modeling improved PBG accuracy. However, maximizing the spinal canal increased the PSSC and subsequent radiculopathy.