Hydroxyapatite Spacers Research Articles

Modified Open-door Laminoplasty Using Hydroxyapatite Spacers and Miniplates.

ObjectiveCervical laminoplasty has been widely accepted as one of the major treatments for cervical myelopathy and various modifications and supplementary procedures have been devised to achieve both proper decompression and stability of the cervical spine. We present the retrospectively analyzed results of a modified unilateral open-door laminoplasty using hydroxyapatite (HA) spacers and malleable titanium miniplates.MethodsFrom June 2008 to May 2012, among patients diagnosed with cervical spondylotic myelopathy and ossification of posterior longitudinal ligament, the patients who received laminoplasty were reviewed. Clinical outcome was assessed using Frankel grade and Japanese Orthopaedic Association score. The radiologic parameters were obtained from plain films, 3-dimensional computed tomography and magnetic resonance images.ResultsA total of 125 cervical laminae were operated in 38 patients. 11 patients received 4-level laminoplasty and 27 patients received 3-level laminoplasty. Postoperatively, the mean Frankel grade and JOA score were significantly improved from 3.97 to 4.55 and from 12.76 to 14.63, respectively (p<0.001). Radiologically, cervical curvature was worsened from 19.09 to 15.60 (p=0.025). The percentage of range of motion preservation was 73.32±22.39%. The axial dimension of the operated spinal canal was increased from 1.75 to 2.70 cm2 (p<0.001).ConclusionIn the presenting study, unilateral open-door laminoplasty using HA spacers and miniplates appears to be a safe, rapid and easy procedure to obtain an immediate and rigid stabilization of the posterior elements of the cervical spine. This modified laminoplasty method showed effective expansion of the spinal canal and favorable clinical outcomes.

A less-invasive cervical laminoplasty for spondylotic myelopathy that preserves the semispinalis cervicis muscles and nuchal ligament

Modified cervical laminoplasty techniques have been developed to reduce postoperative axial neck pain and preserve function in patients with cervical spondylotic myelopathy (CSM). However, the previous studies demonstrating satisfactory surgical outcomes had a retrospective design. Here, the authors aimed to prospectively evaluate the 2-year outcomes of a modified cervical laminoplasty technique for CSM that preserves the paravertebral muscles. Outcomes were analyzed for 40 patients (22 men and 18 women; mean age, 66.6 years; age range 44-92 years) with CSM who underwent C4-6 laminoplasty with C-3 and C-7 partial laminectomies or C-3 total and C-7 partial laminectomies and received hydroxyapatite spacers. Neurological, pain severity, and spinal radiographic evaluations were performed preoperatively and at 3, 6, 12, 18, and 24 months postoperatively. Plain radiography and MRI of the cervical spine were performed to evaluate the range of motion (ROM), sagittal alignment, and cross-sectional areas of the deep extensor muscles. The extent of bone-spacer bonding and bony union at the gutter was assessed by CT. The mean preoperative Japanese Orthopaedic Association CSM score was 10.2, but it increased to 14.4 by 24 months after surgery. Eleven patients had axial neck pain preoperatively, but only 3 reported mild pain at 24 months, and in all 3 cases the pain was mild. The mean angle of lordosis was 11.7° preoperatively and 12.0° 2 years postoperatively. Although the ROM at the C2-7 levels was significantly reduced 3 months postoperatively, an increasing trend was observed up to 12 months, and 86% of the preoperative ROM was achieved by 2 years postoperatively. The mean paravertebral muscle cross-sectional areas were 833 ± 215 mm(2) preoperatively and 763 ± 197 mm(2) 24 months postoperatively, but the difference was not statistically significant. The rates of bone-spacer bonding and bony union at the gutter were low during the early stages but increased to 90% and 93%, respectively, by 2 years after surgery. The modified laminoplasty technique used in this study ensured very good neurological status and ROM after 2 years and was associated with low incidences of axial neck pain and serious complications. This simple and easy operative method could benefit future laminoplasty protocols.

Histological Analysis of Bone Bonding and Ingrowth into Connected Porous Hydroxyapatite Spacers in Spinal Surgery

To evaluate the osteoconductive potential of connected porous hydroxyapatite (HAp), we histologically analyzed the newly formed bone inside unidirectional porous HAp (Regenos®, Kuraray, Japan; 75% porosity, n=17) and interconnected porous HAp (Neobone®, Covalent Materials, Japan; 75% porosity, n=10) 26 weeks after their implantation as bone spacers between the split lumbar laminae of goats. As a control, non-connected porous HAp spacers (Apaceram®, Pentax, Japan; 50% porosity, n=5) were used. After staining non-decalcified samples with Villanueva Goldner, changes in pore shape were evaluated microscopically and new bone formation in HAp spacers was quantitatively analyzed. In addition, blood vessel distribution was evaluated by hematoxylin and eosin staining. Changes in pore shape were observed in 76% of the Regenos® spacers and 90% of the Neobone® spacers but were not detected in the Apaceram® spacers. Only limited new bone formation was observed in the Regenos® and Neobone® spacers, whereas vascular-like structures were detected in 82% of the Regenos®, 70% of the Neobone®, and 80% of the Apaceram® spacers. The changes in pore shape were thought to have resulted from the low initial compression strength of the connected porous HAp, which may have limited the inherent osteoconductive potential of connected HAp. Our findings suggest that the maintenance of pore shape is required for promoting new bone formation in connected porous HAp when used as lamina spacers in spinal surgery.

Midline-Splitting Open Door Laminoplasty Using Hydroxyapatite Spacers : Comparison between Two Different Shaped Spacers

ObjectiveAlthough 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.MethodsDuring 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.ResultsAll 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.ConclusionClinical 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.

Remarkable epidural scar formation compressing the cervical cord after osteoplastic laminoplasty with hydroxyapatite spacer

The authors report on an 81-year-old woman whose condition deteriorated 2 months after undergoing osteoplastic laminoplasty with placement of hydroxyapatite spacers. Magnetic resonance imaging showed postlaminectomy scar formation compressing the cervical spinal cord. The patient underwent laminectomy and removal of remarkably thick epidural scar tissue, which resulted in resolution of her symptoms. Histological diagnosis of the scar was fibrous granulation tissue with foreign body granuloma, characterized by multinucleated giant cells and marked increases of capillary vessels, fibroblasts, and collagen fibers. This case of symptomatic postlaminectomy scar formation after osteoplastic laminoplasty suggests that osteoplastic laminoplasty cannot always prevent laminectomy membrane formation.

Long-term results of double-door laminoplasty using hydroxyapatite spacers in patients with compressive cervical myelopathy

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.

Cervical Unilateral Open-Door Laminoplasty With Titanium Miniplates Through Newly Designed Hydroxyapatite Spacers -Technical Note-

A newly designed hydroxyapatite (HA) spacer for cervical laminoplasty is provided with a hole through which the titanium miniplate is passed. A new method of unilateral open-door laminoplasty with titanium miniscrew and miniplate through this HA spacer is described. Twenty-two patients with cervical stenotic disorders were treated by this procedure. Only the predominantly affected side of the laminae is exposed. The supraspinous and interspinous ligaments and the deep muscle layer in the contralateral side are left intact. A 4-mm wide gutter near the intervertebral joint is made and contralateral hinges are made under the deep muscle layer with minimum detachment of these muscles. The opened lamina is fixed with the titanium miniplate passed through the hole in the newly designed HA spacer. Mean operative time for the 22 operations was 193.5 minutes. Mean enlargement of the minimum spinal canal diameter was 50.9%. Neurological outcomes after 3 months were evaluated according to the Japanese Orthopaedic Association (JOA) scoring. Mean recovery rate of JOA score by Hirabayashi's method was 49.5%. Only 2 patients reported postoperative axial neck pain. Our method for unilateral open-door laminoplasty provides adequate decompression and tight fixation of laminae, and is less invasive to the posterior supporting elements of cervical spine.

Multidirectional Flexibility of the Spine Following Posterior Decompressive Surgery After Single-Level Cervical Disc Arthroplasty

In vitro human cadaveric biomechanical study. This study quantifies the multidirectional flexibility of the spine following laminoplasty and laminectomy after cervical disc arthroplasty. Posterior decompressive surgery may be used to treat recurrence of myeloradiculopathy following disc arthroplasty. This is the first study investigating the biomechanical effects of posterior decompressive surgery combined with cervical disc arthroplasty. Seven human cervical spines were biomechanically evaluated under the following conditions: (1) intact; (2) discectomy (C5-C6); (3) disc arthroplasty (C5-C6); (4) arthroplasty + 3-level laminoplasty (C3-C5); (5) arthroplasty + 4-level laminoplasty (C3-C6); (6) arthroplasty + 5-level laminoplasty (C3-C7); (7) arthroplasty + 5-level laminoplasty (C3-C7) without hydroxyapatite spacers; and (8) arthroplasty + laminectomy (C3-C7). Multidirectional flexibility testing used unconstrained pure moments of ±2 Nm for flexion-extension, axial rotation, and lateral bending. Quantification of C5-C6 and C3-C7 range of motion (ROM) and neutral zone (NZ) were normalized to the intact spine (100%). Flexion-extension loading of the discectomy condition demonstrated ROM of 22.05° ± 4.17° at the operative level (P < 0.05). Implantation of the porous coated motion device restored segmental motion near the intact condition (ROM, 9.97° ± 6.44°; NZ, 5.82° ± 6.18°). There were no statistical differences between 3-level (13.79° ± 6.49°), 4-level (14.51° ± 5.76°), and 5-level (15.67° ± 5.71°) laminoplasty; however, additional levels demonstrated a trend toward increased motion at the arthroplasty level. Laminoplasty without spacers (17.45°) and laminectomy (18.27°) indicated even greater segmental motion (P > 0.05). Axial rotation and lateral bending indicated trends similar to those for flexion-extension. Posterior decompressive surgery increased ROM and NZ in all loading modes compared to arthroplasty alone, and laminectomy markedly increased motion compared with laminoplasty. Use of hydroxyapatite spacers and minimization of the extent of laminoplasty appear to be biomechanically favorable in this in vitro model.

Union and Laminar Bone Growth around Hydroxyapatite Spacers with Split Spinous Process in Double-Door Laminoplasty for Multilevel Cervical Spondylotic Myelopathy and Ossification of Posterior Longitudinal Ligament

Union and Laminar Bone Growth around Hydroxyapatite Spacers with Split Spinous Process in Double-Door Laminoplasty for Multilevel Cervical Spondylotic Myelopathy and Ossification of Posterior Longitudinal Ligament

New Titanium Spacer for Cervical Laminoplasty: Initial Clinical Experience -Technical Note-

Many commercially available hydroxyapatite (HA) spacers for cervical laminoplasty have been introduced but have disadvantages such as lack of plasticity, easy cracking, and occasional difficulty in fixation by sutures. Here we present the short-term results of a newly designed titanium spacer (Laminoplasty Basket) in open-door cervical laminoplasty, and evaluated clinically and radiologically. The titanium box-shaped spacer with two arms for fixation was easily inserted and fixed into the laminoplasty space with 4-mm or 5-mm length screws after the posterior cervical arch was repositioned for the canal expansion. Twenty-one patients with cervical myelopathy due to spondylosis or ossification of the longitudinal ligament or developmental narrow canal observed for more than 6 months postoperatively were enrolled in this study. The neurological condition of these patients improved from 9.4 points on the Japanese Orthopaedic Association scale preoperatively to 13.5 points at 6 months after surgery. Postoperative radiological evaluation showed no laminar closure or implant failure and cervical spine curvature was maintained. These results seemed to have no significant difference compared with those using HA spacers. This titanium spacer is a potential substitute for conventional HA or other similar devices in cervical laminoplasty.

The problem of posterior expansive laminoplasty with hydroxyapatite spacer in elderly patients

The problem of posterior expansive laminoplasty with hydroxyapatite spacer in elderly patients

Postoperative displacement of hydroxyapatite spacers implanted during double-door laminoplasty

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.

ERRATUM: Clinical and Radiological Outcomes of Anterior Cervical Interbody Fusion Using Hydroxyapatite Spacer

[This corrects the article on p. 300 in vol. 46, PMID: 19893716.].

Clinical and Radiological Outcomes of Anterior Cervical Interbody Fusion Using Hydroxyapatite Spacer

This is retrospective study of clinical and radiological outcomes of anterior cervical fusion using Bongros-HA (BioAlpha, Seongnam, Korea) which is a type of synthetic hydroxyapatite (HA) spacer to evaluate the efficacy in its clinical application and usefulness as a reliable alternative to autograft bone. Twenty-nine patients were enrolled in this study and 40 segments were involved. All patients were performed anterior cervical interbody fusion using HA spacer and plating system. Indications for surgery were radiculopathy caused by soft-disc herniation or spondylosis in 18 patients, spondylotic myelopathy in 1 patient, and spinal trauma in 10 patients. Cervical spine radiographs were obtained on postoperative 1day, 1week, and then at 1, 2, 6, and 12 months in all patients to evaluate intervertebral disc height, and the degrees of lordosis. Cervical computed tomography was done at postoperative 12 month in all patients to confirm the fusion status. The mean period of clinical follow-up was 17 months. Complete interbody fusion was achieved in 100% of patients. Preoperative kyphotic deformities were corrected in all cases after surgery. Intervertebral disc height was well maintained during follow up period. There were no cases of graft extrusion, graft deterioration and graft fracture. HA spacer is very efficient in achieving cervical fusion, maintaining intervertebral disc height, and restoring lordosis. When combined with the placement of a cervical plate, immediate stability can be achieved and graft related complication can be prevented.

Dural Laceration

The authors describe 4 cases of delayed dural laceration by hydroxyapatite (HA) spacer causing tetraparesis following double-door laminoplasty. There are few reports of iatrogenic spinal cord lesions developing after double-door laminoplasty, although some complications such as postoperative C-5 paralysis or axial symptoms have been reported. The purpose of this report is to draw attention to the possibility of delayed dural laceration and its triggering mechanism. One hundred thirty patients treated for cervical myelopathy were followed up for an average of 2 years and 9 months after laminoplasty. Four patients experienced aggravation of cervical myelopathy. Anterior dislodgement of HA spacers was shown on plain lateral radiographs. Follow-up T2-weighted magnetic resonance imaging demonstrated that the dislodged HA spacers were surrounded by cerebrospinal fluid at the time of aggravation. The dislodged HA spacers were removed and the dural membrane defects were repaired by patching with the fascia of the gluteus maximus muscle. The preoperative symptoms improved after the second operation in all patients. It is hypothesized that the loosening of the HA spacer in split spinous processes could occur with the movement of the cervical spine and/or the breakage of the suture before bone bonding. Anterior dislodgement of the HA spacer toward the spinal canal would cause dural laceration by direct friction between the dural membrane and the dislodged HA spacer, resulting in clinical aggravation. Despite the well-documented advantages of using HA spacers for double-door laminoplasty, possible laceration due to a dislodged HA spacer should be considered as a late complication.

Delayed dural laceration by hydroxyapatite spacer causing tetraparesis following double-door laminoplasty

The authors describe 4 cases of delayed dural laceration by hydroxyapatite (HA) spacer causing tetra-paresis following double-door laminoplasty. There are few reports of iatrogenic spinal cord lesions developing after double-door laminoplasty, although some complications such as postoperative C-5 paralysis or axial symptoms have been reported. The purpose of this report is to draw attention to the possibility of delayed dural laceration and its triggering mechanism. One hundred thirty patients treated for cervical myelopathy were followed up for an average of 2 years and 9 months after laminoplasty. Four patients experienced aggravation of cervical myelopathy. Anterior dislodgement of HA spacers was shown on plain lateral radiographs. Follow-up T2-weighted magnetic resonance imaging demonstrated that the dislodged HA spacers were surrounded by cerebrospinal fluid at the time of aggravation. The dislodged HA spacers were removed and the dural membrane defects were repaired by patching with the fascia of the gluteus maximus muscle. The preoperative symptoms improved after the second operation in all patients. It is hypothesized that the loosening of the HA spacer in split spinous processes could occur with the movement of the cervical spine and/or the breakage of the suture before bone bonding. Anterior dislodgement of the HA spacer toward the spinal canal would cause dural laceration by direct friction between the dural membrane and the dislodged HA spacer, resulting in clinical aggravation. Despite the well-documented advantages of using HA spacers for double-door laminoplasty, possible laceration due to a dislodged HA spacer should be considered as a late complication.

Open reduction and palmar plate-osteosynthesis in combination with a nanocrystalline hydroxyapatite spacer in the treatment of comminuted fractures of the distal radius

Open reduction and palmar plate-osteosynthesis in combination with a nanocrystalline hydroxyapatite spacer in the treatment of comminuted fractures of the distal radius

Open reduction and palmar plate-osteosynthesis in combination with a nanocrystalline hydroxyapatite spacer in the treatment of comminuted fractures of the distal radius

In a prospective study, we used the nanocrystalline hydroxyapatite paste Ostim (Osartis, Obernburg, Germany) in combination with a palmar plate to treat comminuted radius fractures with a metaphyseal and articular component in order to examine the clinical use of Ostim as a bone substitute. Twenty-one patients with 22 radius fractures of AO types C2 and C3 were included in the study. The measurements, taken 10.2+/-1.3 months after the initial treatment, revealed a dorsopalmar tilt of 8.8+/-3.7 degrees , a radioulnar inclination of 18.8+/-2.8 degrees and an ulnar variance of 0.8+/-1.8mm. According to the Gartland and Werley evaluation, eight of the treated fractures attained an excellent, 11 a good and the remaining three a fair result. The study demonstrates that Ostim, in combination with angularly stable osteosynthesis, can be used as an acceptable bone substitute for the treatment of type C2 and C3 radial fractures.

Open Door Laminoplasty using Autogenous Spinous Process H-beam Grafts for Cervical Radiculomyelopathy

Purpose : To evaluate the results and effectiveness of laminoplasty in which autogenous spinous process grafts were used for the treatment of cervical spondylotic radiculomyelopathy. Materials and Methods : Sixteen patients with cervical spondylotic radiculomyelopathy were treated by laminoplasty from October 2001 to June 2004. The average follow-up period was 28 months (range, 14-47 months), the average age of the patients was 58 years old (range, 33-74 years old), and there were 14 men and 2 women. The operative procedure was a modified Itoh's laminoplasty with and H-beam shaped strut bone graft, which was harvested by sacrificing the spinous process. The results of the operative procedure were evaluated with a Pavlov ratio in a radiologic study and the JOA score and recovery rate by Hirabayashi in the clinical study. Results : At the final follow-up, the average JOA score increased from 7.8 to 13.2. The recovery rate was 58.7%. The Pavlov ratio improved from 0.58 to 0.93 post-operatively and to 0.92 at the final follow-up. The brace was removed at an average of 6 weeks and there was no change in the Pavlov ratio until union. There was neither evidence of instability in flexion and extension of the cervical spine nor neurologic aggravation and complications. Conclusion : Laminoplasty using an autogenous spinous process in patients with cervical spondylotic radiculomyelopathy produced stability and could produce sufficient decompression. The advantages of an autogenous spinous process graft are: an early return to normal activity by shortening the period of the need for a brace, and no extra-cost and complications with the autogenous iliac graft, allograft, heterograft, or hydroxyapatite spacer. It can be considered as the optimal surgical procedure due to providing complete union at the last follow-up and no complications in the radiologic and clinical studies.

Cervical laminoplasty: evaluation of bone bonding of a high porosity hydroxyapatite spacer.

The purpose of this study was to evaluate the usefulness of a high-porosity hydroxyapatite (HA) spacer in cervical laminoplasty. Bone-spacer bonding rates, complications associated with the implant, and factors related to bone bonding were examined. The authors evaluated 33 consecutive patients with cervical myelopathy who underwent high-porosity HA spacer-assisted laminoplasty and were followed for at least 1 year (mean 30 months). The results of bone-spacer bonding of the 147 implants were evaluated using computerized tomography (CT) scanning. The symptoms significantly improved in 30 patients. No difference in results was detected between patients with cervical spondylosis and those with ossification of posterior longitudinal ligament. Breakage of seven spacers occurred in four patients without causing neck pain or neurological deficits. There were no other HA spacer-related complications. The spacers became rigidly bound to bone in 61% of the cases, and bone regrowth developed around the spacer in 91%. The rate of bone-spacer bonding increased over time, and the CT-documented attenuation value (Hounsfield unit) of the spacer adjacent to the bone-spacer junction in the group in which union occurred was significantly higher than in the nonunion group. High-porosity HA spacer-augmented laminoplasty produced good bonding-related results. Bone bonding continued to progress 1 year after surgery, indicating the good osteoconductive capability of high-porosity HA. To avoid breakage of a spacer, a minimum 7-mm distance between spacers is necessary.