Hydroxyapatite laminar spacers and titanium miniplates in cervical laminoplasty

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Object. The authors describe a new surgical technique for cervical laminoplasty that was performed in 25 patients. The posterior elements along with the various ligaments are removed en bloc and are stabilized in a lift-up position by placing hydroxyapatite (HA) laminar spacers and titanium miniplates and screws. The procedure and clinical results are discussed.

Methods. The posterior spinal elements, including the lamina(e), spinous process(es), and various attached ligaments, are removed en bloc by incising the lamina in its lateral aspect. Trapezoid-shaped HA spacers are placed between the cut ends of the laminae or between the laminae and lateral masses bilaterally at each level. Malleable titanium miniplates and screws are used for fixation of the spacers. The fixation of transected laminae was judged to be successful. Postoperative care included application of a soft neck collar for 1 week but no further restriction of activity. Surgery-related outcome was assessed in the 21 patients who attended more than 6 months of follow up after laminoplasty. There were 18 men and three women who ranged in age from 27 to 81 years. Cervical stenotic myelopathy was demonstrated in 15 patients who underwent decompressive and expansive laminoplasty, and spinal tumors were documented in six patients who underwent a nonexpansive laminoplasty. Postoperative and follow-up computerized tomography scans demonstrated no hardware failure. Bone formation around the spacers was observed either at 6- or at 9-month follow-up examination in all 21 patients. Fusion of the reconstructed laminae was found to be completed at 12 months in all 18 patients able to attend follow up for this duration. Spinal alignment and the range of motion of the cervical spine were well preserved. In patients with stenotic cervical myelopathy, neurological and anatomical outcome of canal expansion were satisfactory.

Conclusions. This technique enables rigid laminoplasty while maintaining anatomical and biomechanical integrity of posterior elements of cervical spine. Expansive and nonexpansive laminoplasty procedures are possible.

Article Information

Address reprint requests to: Kenji Ohata, M.D., Department of Neurosurgery, Osaka City University Graduate School of Medicine, Medical School, 1–4–3 Asahi-machi, Abeno-ku, Osaka 545–8586, Japan. email: kohata@med.osaka-cu.ac.jp.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Diagrams illustrating the surgical procedure. A: En bloc laminotomy. B: Selection of the suitable-size HA spacer. C: An expanded lamina made with the titanium plate and the HA spacer. D: Replacement of reconstructed lamina to complete the expanded laminoplasty.

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    Photograph showing laminar spacers. The trapezoid-shaped spacer is made up of HA and is 6 mm in width regardless of its length. Its length facing the dural side is 3 (left), 5 (center) and 8 mm (right). The small hole in the spacer is for suture fixation of spacer to the miniplate for prevention of displacement during the procedure.

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    Photograph of the construct model from the cranial side (left) and in an oblique orientation (right). Spacers and miniplates appear as a bridge between the lamina and lateral mass. Note that the spacer is designed to fit the bone edge bilaterally.

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    Line drawing showing the method of measurement of the cervical curvature and ROM of the cervical spine. Two lines are drawn along the posterior borders of C-2 and C-7 in the flexion (a), neutral (b), and extension (c) positions. The angle formed at the crossing point of these two lines is measured in each position. The angle in neutral position is expressed as cervical curvature (b), and the sum of cervical curvature at maximum flexion (a), and maximum extension (c) as the ROM.

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    Case 7. Magnetic resonance imaging. Left: Preoperative sagittal T2-weighted MR image revealing spinal canal stenosis. Right: Postoperative sagittal T2-weighted MR image demonstrating the results of the laminoplasty and the enlargement of the cervical canal size.

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    Serial CT studies obtained in Case 3 (upper row) and Case 18 (lower row). The studies shown are (from left to right) preoperative, immediate postoperative, 6-month follow-up, and 12-month follow-up scans, respectively. Upper Row: A preoperative axial CT scan revealed developmental stenosis of the spinal canal associated with osteophytic spur on the left side. Follow-up axial CT scans obtained at the level of C-4 after expansive laminoplasty in a case of cervical stenotic myelopathy with ossification of posterior longitudinal ligament. An HA spacer of medium size was inserted on the left and one of large size on the right at this level. At 6 months after surgery, new bone formation was observed from the vertebral side to the spacer, especially on the left; at 12 months, bone union was observed bilaterally. Lower Row: A preoperative CT scan at C-4 demonstrated a cervical ependymoma. Small-sized HA spacers were placed bilaterally. At 6 months some new bone formation from the vertebral side to spacer was observed bilaterally. At 12 months bone union was demonstrated around the spacers. Titanium miniclips used for dural closure are seen as small hyperdense spots inside the spinal canal.

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