Postoperative displacement of hydroxyapatite spacers implanted during double-door laminoplasty: Clinical article

Department of Orthopedics, National Hospital Organization Osaka Minami Medical Center, Kawachinagano, Osaka Japan.
Journal of Neurosurgery Spine (Impact Factor: 2.38). 06/2009; 10(6):551-6. DOI: 10.3171/2009.2.17680
Source: PubMed


Double-door laminoplasty using hydroxyapatite (HA) spacers has been widely performed for compressive cervical myelopathy and has provided good neurological outcome. Although HA spacers are used for preventing reclosure of the opened laminae, they are often displaced or dislocated from their original position. The authors investigated the incidence and patterns of postoperative HA spacer displacement to determine the reasons for this unfavorable event.
Eighty-six patients with compressive myelopathy underwent double-door laminoplasty in which a total of 278 HA spacers were used. The displacement of HA spacers and opened laminae were assessed using postoperative lateral radiographs and CT scans.
Postoperative dorsal migration > 2 mm was found in 116 (42%) of 278 implanted HA spacers. In addition, 33 (38%) of 86 HA spacers rotated > 10 degrees and 29 (34%) of the 86 opened laminae tilted > 10 degrees. Moreover, deformation of the newly formed spinal canal was observed in 51 (59%) of 86 cases, and bone fusion between the HA spacer and spinous process was achieved in only 15 (8.7%) of 172 cases. Neurological worsening and neck pain, however, were not associated with displacement of HA spacers or deformation of the spinal canal.
In double-door laminoplasty, postoperative displacement of the HA spacer with deformation of the enlarged spinal canal occurred frequently. Hydroxyapatite spacers tend to become displaced after surgery. Placing the HA spacer at the base of the spinous process close to the dura mater may prevent postoperative displacement.

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    • "HA have several advantages compared with autologous bone grafts for expansive midline splitting laminoplasty, including good biomechanical stability and reductions in operation time, blood loss, and donor site morbidity8,12,14,15). Although HAs have been shown to be biocompatible and to fuse with lamina2-4,6,10), no previous study had analyzed the relationship between HA shape and outcomes. We therefore assessed the effects of HA shape (winged versus wingless) on clinical and radiological outcomes. "
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    ABSTRACT: Although hydroxyapatite (HA) spacer has been used for laminoplasty, there have been no reports on factors associated with fusion and on the effects of HA shape. During January 2004 and January 2010, 45 patients with compressive cervical myelopathy underwent midline-splitting open door laminoplasty with winged (33 cases) and wingless (12 cases) HAs by a single surgeon. Minimal and mean follow up times were 12 and 28.1 months, respectively. Japanese Orthopedic Association (JOA) score was used for clinical outcome measurement. Cervical X-rays were taken preoperatively, immediately post-operatively, and after 3, 6, and 12 months and computed tomography scans were performed preoperatively, immediately post-operatively and after 12 months. Cervical lordosis, canal dimension, fusion between lamina and HA, and affecting factors of fusion were analyzed. All surgeries were performed on 142 levels, 99 in the winged and 43 in the wingless HA groups. JOA scores of the winged group changed from 10.4±2.94 to 13.3±2.35 and scores of the wingless group changed from 10.8±2.87 to 13.8±3.05. There was no significant difference on lordotic and canal dimensional change between two groups. Post-operative 12 month fusion rate between lamina and HA was significantly lower in the winged group (18.2 vs. 48.8% p=0.001). Multivariate analysis showed that ossification of the posterior longitudinal ligament, male gender, and wingless type HA were significantly associated with fusion. Clinical outcome was similar in patients receiving winged and wingless HA, but the wingless type was associated with a higher rate of fusion between HA and lamina at 12 months post-operatively.
    Journal of Korean Neurosurgical Society 07/2012; 52(1):27-31. DOI:10.3340/jkns.2012.52.1.27 · 0.64 Impact Factor
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    ABSTRACT: No previous studies have reported 10-year follow-up results for double-door laminoplasty using hydroxyapatite (HA) spacers. The purpose of this study was therefore to explore the long-term results of double-door laminoplasty using HA spacers and to determine if non-union or breakage of HA spacers is related to restenosis of the enlarged cervical canal. The study group consisted of 68 patients with a minimum of 10 years of follow-up after double-door laminoplasty using HA spacers. The average postoperative Japanese Orthopaedic Association score improved significantly after surgery and was maintained until the final follow-up. The average range of motion decreased by 42.6% in patients with cervical spondylotic myelopathy (CSM) and 65.8% in patients with ossification of the posterior longitudinal ligament (OPLL). The enlarged cervical canal area was preserved almost until the final follow-up. The average non-union rates of HA spacers were 21% in CSM and 17% in OPLL, and the average breakage rates were 24 in CSM and 21% in OPLL at the final follow-up. Although non-union and breakage of HA spacers were common, neither of these factors were correlated with restenosis of the enlarged cervical canal.
    European Spine Journal 02/2011; 20(9):1560-6. DOI:10.1007/s00586-011-1724-7 · 2.07 Impact Factor
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