Bone-fibrin mixture in spinal surgery.

When bone grafting is performed adjacent to the spinal cord, instability of the grafted bone can result in compression of the spinal cord. To prevent this complication, fibrin sealant was mixed with the fine fragments of autogeneic bone, and the resultant pastelike mixture was used as a graft material. Operative procedures performed were posterolateral fusion (11 cases), anterior fusion (seven cases), and grafting into the bone defect (one case). After solidification of fibrin sealant, the autogeneic bone grafts were found to be firmly fixed in place, resulting in good bony fusion, and there were none of the neurologic symptoms associated with graft instability. No neurotoxicity was observed in any of these patients. Fibrin sealant was found to be an effective material for spinal surgery.     

The Calcaneal Osteotomy of Dwyer: An Indication for Kiel Bone

Kiel bone has been used with uniformly good results as a bone graft in 15 cases of Dwyer's calcaneal osteotomy. It is suggested that Kiel bone is indicated for this operation in preference to autogenous bone.     

后正中开门加植骨固定术治疗颈椎椎管狭窄症

目的选择一种后路手术治疗椎管狭窄症较理想的方法.方法采用不切除棘突,用线锯从后正中线锯开棘突、椎板及黄韧带,扩大椎管,锯开的棘突间植入骨块并加以固定,治疗颈椎管狭窄9例.结果 JOA评分平均改善率达88%,并且无明显手术并发症,植骨融合良好.结论线锯后正中开门加植骨固定术治疗椎管狭窄症是一种方法简便,减压彻底,手术时间短的治疗方法.     

Heterogenous transplant (Kiel bone) for the operative treatment of scoliosis

Summary and Conclusion Despite the relatively high incidence of defects found in the graft 6 months after the operation, we feel that this heterograft (Kiel bone) is a useful addition in the vertebral fusion operations.Macro and microscopic examinations carried out 6 months following the operation showed good incorporation of the Kiel bone in those cases in which rectangular pieces of cancellous Kiel bone were placed in a spread-out fashion on the top of and between the slivers of autogenous bone.Our limited experience bears out the fact that it is unwise to place the strip sof Kiel bone in contact with each other and neither should they be placed on the non osseous tissue. In those latter instances the incorporation of the Kiel bone is slow and apparently not complete, at least not within the period of 6 months following the operation.The Kiel bone does not provide a substitution for the fresh autogenous transplant in spinal fusion operations, but it provides a very useful addition to the autogenous graft.

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Zusammenfassung und Schlußfolgerung Trotz der verhältnismäßig zahlreichen Spandefekte, die 6 Monate postoperativ festgestellt wurden, sind wir der Meinung, daß der Kieler Knochenspan eine nützliche Ergänzung bei wirbelsäulenversteifenden Operationen ist.Makroskopische und mikroskopische Untersuchungen zeigten 6 Monate nach der Operation eine gute Einheilung des Kieler Knochens in solchen Fällen, in denen rechteckige Spongiosastücke des Kieler Spans auf und zwischen den Eigenspänen flächenhaft verteilt waren.Aus unserer begrenzten Erfahrung geht hervor, daß man die Kieler Knochenspäne nicht in Berührung miteinander bringen und sie auch nicht in nichtknöchernes Gewebe geben soll. Im letzteren Fall erfolgt der Einbau des Kieler Knochens langsam und offenbar unvollständig, zumindest für die Dauer der ersten 6 Monate nach ihrer Implantation.Der Kieler Knochen stellt bei Versteifungsoperationen der Wirbelsäule keinen Ersatz, jedoch eine wertvolle Ergänzung des Eigenspans dar.

     

Bone grafting for spinal fusion.

At least 250,000 spinal fusions are performed in the United States each year, nearly all requiring implantation of bone graft material. The preferred technique for most of these operations is the transplantation of structured or morcellized autologous corticocancellous bone from the iliac crest. Further, because of the increasing frequency of spinal fusion surgery during the 1990s, arthrodesis of the spine has become the most common reason for autologous bone graft harvest. This article reviews the current clinical status of autogenous bone grafts and alternative materials in spinal fusion surgery.     

Mixture ratios of local bone to artificial bone in lumbar posterolateral fusion

There have been no reports on the effects of the mixture ratio of local bone graft to artificial bone on the outcome of intervertebral bone fusion. The purpose of this study was to determine whether the mixture ratio of local bone removed from laminae and spinous processes to apatite- and wollastonite-containing glass ceramic (AWGC) granules affected fusion rates in spinal fusion. Posterolateral lumbar fusion at two levels without spinal instrumentation was performed in 35 patients who were diagnosed with lumbar spinal canal stenosis. The patients were randomly divided into three groups, each of which received a different mixture ratio of local bone to AWGC granules: 2:1, 1:1, and 1:2. The total mass of grafted bone was 20 g in all three groups. The fusion rate was approximately 80% in all three groups. Our results indicate that lumbar posterolateral fusion can be successfully achieved even when the mixture ratio of local bone graft to AWGC granules is 1:2.     

The efficacy of interconnected porous hydroxyapatite in achieving posterolateral lumbar fusion in sheep

STUDY DESIGN: An animal study was performed to evaluate lumbar spinal fusion radiologically and mechanically. OBJECTIVES: To assess the efficacy of interconnected porous hydroxyapatite in achieving posterolateral lumbar arthrodesis in sheep. SUMMARY OF BACKGROUND DATA: Posterolateral spinal arthrodesis with autologous bone graft is the gold standard procedure for lumbar fusion. The procedure for harvesting bone from the iliac crest increases morbidity. Interconnected porous hydroxyapatite has been used effectively as an alternative to cancellous bone graft material in metaphyseal bone defects. Little is known about the efficacy of interconnected porous hydroxyapatite in achieving lumbar spinal fusion. METHODS: Four groups of seven sheep underwent bisegmental posterolateral lumbar fusion with instrumentation using different intertransverse graft material. In group 1, no graft material was used. In group 2, autologous bone was used. Group 3 had interconnected porous hydroxyapatite. Group 4 had an equip of interconnected porous hydroxyapatite and autologous bone. The animals were killed at 20 weeks after surgery. Radiographs and computed tomography images were obtained. The fusion masses were graded for bone resorption and trabecular connectivity on the computed tomography images. Mechanical testing of the specimens was performed, and the three-dimensional segmental motion was measured in flexion/extension, axial rotation, and lateral bending. RESULTS: The radiographic images were difficult to interpret because of the radiodense interconnected porous hydroxyapatite granules. According to mechanical stability criteria, the fusion rate for the different groups was as follows: 100% (14/14) for the autologous bone group, 72% (10/14) for the bone/interconnected porous hydroxyapatite group, 50% (7/14) for the pure interconnected porous hydroxyapatite group, and 15% (2/14) for the sham group. CONCLUSIONS: Spinal arthrodesis using interconnected porous hydroxyapatite alone or mixed with bone as graft material reduced segmental motion. It was not, however, as effective as autologous bone graft material in achieving spinal arthrodesis. The sheep model using autologous bone achieved a 100% fusion rate. Because the nonunion rate for a single level in humans may be as high as 40%, the fusion rate with bone/interconnected porous hydroxyapatite in humans may be lower than the 72% found in the sheep model. The little resorption of the radiodense interconnected porous hydroxyapatite granules made the radiologic evaluation of the fusion masses difficult.     

The effect of anti-resorptive therapies on bone graft healing in an ovariectomized rat spinal arthrodesis model

Bone grafting is commonly used to treat skeletal disorders associated with a large bone defect or unstable joint. Spinal arthrodesis surgery, which is the most common application of bone graft, is performed in the elderly and anti-resorptive therapy is sometimes started postoperatively in patients with bone fragility due to osteoporosis, despite insufficient knowledge about the effects of these drugs on bone graft healing. Therefore, we studied the effect of bisphosphonates (BP) and selective estrogen receptor modulators (SERM) on bone graft healing in an ovariectomized rat spinal arthrodesis model. Female Sprague-Dawley rats (n=100) were ovariectomized or sham-operated, and randomized into four groups: Sham (sham-operated+vehicle), Ovx (ovariectomy+vehicle), Ovx-Rlx (ovariectomy+raloxifene, 1 mg/kg/day), and Ovx-Aln (ovariectomy+alendronate, 0.01 mg/kg/day). Four weeks after ovariectomy, lumbar spinal arthrodesis surgery was performed using an autologous bone graft. Animals were killed 2, 4, and 8 weeks after surgery, and fusion assessment, three-dimensional micro-computed tomography, histomorphometry, mRNA expression analysis, and serum bone metabolic marker analysis were performed. The results indicated that neither BP nor SERM significantly altered the fusion rate, but the bone graft healing process was differentially affected. BP inhibited endochondral ossification and graft bone resorption, but induced the growth of a larger, denser fusion mass compared to Ovx by strongly suppressing osteoclastic activity. SERM mildly suppressed bone remodeling, but did not significantly inhibit the ossification process, leading to a fusion mass comparable with that of Sham animals. These findings suggested that spinal fusion surgery outcome is not likely to be altered by BP or SERM treatment started immediately after spinal arthrodesis surgery; however, to avoid adverse effects of BP on bone graft healing, BP treatment should be delayed during the immediate postoperative period.     

Experimental application of calcium phosphate granulate for the substitution of conventional bone transplants (author's transl)]

Autologous spongiosa, a calcium phosphate ceramic and Kiel bone chips were implanted in the tibiae of dogs and compared with respect to tissue compatibility and osteogenetic effect. After the ceramic implants and the autologous spongiosa had been left in the tibial fat marrow for six weeks, bone tissue and bone marrow had formed to the same extent around both materials. Their stimulating effect on osteogenesis was comparable. In contrast to the ceramic material, together with which they had been implanted in active bone marrow, the Kiel bone chips were surrounded by fibrous tissue in addition to bone tissue. All of the three types of implant proved to be tissue compatible. On the whole, the calcium phosphate ceramic was found to be equal to autologous and superior to heterologous spongiosa from a biological point of view. In technical terms the ceramic implant was superior also to the autologous graft.     

Fibrillar collagen-biphasic calcium phosphate composite as a bone graft substitute for spinal fusion.

The osteoconductive capacity of fibrillar collagen-biphasic calcium phosphate composition was compared to autogenous bone in a canine spinal fusion model. All animals underwent a standard intervertebral body fusion (L2-L4) with rigid internal fixation and received either autogenous bone alone or a mixture of the ceramic and autogenous bone (3:1) as the graft material. Animals were followed for 12 months and the quality of fusion in each animal assessed by biomechanical testing and histological analysis. The fused L2-L4 segment of each dog was embedded in bone cement and mounted in a specially designed mechanical tester for testing in flexion, extension, and side bending. Overall, the mean rigidity of the fusion mass was not significantly different between the two groups [10.5 +/- 4.1 (SD) for autogenous bone vs. 11.3 +/- 1.7 for the ceramic plus autogenous bone, p greater than 0.05]. Similar findings were obtained for mean bending moment, compressive load, angular deformation, and energy absorbed for the two groups. Histological analysis was performed on transverse nondecalcified specimens. Quantitation of bone ingrowth using back-scattered electron imaging disclosed no significant differences in the amount of new bone formed at the graft site between autogenous bone and the ceramic plus autogenous bone recipients (23.4 +/- 10% vs. 25.8 +/- 8.8%) when correction for the autogenous bone volumes was performed. Light microscopic analysis of toluidine blue-stained transverse sections demonstrated new bone growth around and through the ceramic bone graft material. These results suggest that use of a collagen-biphasic calcium phosphate ceramic and autogenous bone mixture (3:1) provides a suitable osteoconductive alternative to the use of autogenous bone and results in the formation of a mechanically competent fusion mass not significantly different from that obtained with autogenous bone alone.     

Value of heterologous bone transplants in the surgical therapy of habitual shoulder dislocation

45 heterologous bone grafts of "Kiel Bone" were radiologically examined after operative treatment of recurrent shoulder dislocation in the technique of M. Lange. The postoperative period differed between 1 and 17 years. Bony consolidation was achieved in 80% of the cases. Signs of resorption were postoperatively found in 14 cases. Five of them consolidated secondaryly. The results of our study show the usefulness of "Kiel Bone" in the treatment of recurrent shoulder dislocation. It should not be used as a bone graft in cases which require quick an secure consolidation. In these cases autologous bone grafts are superior.     

Natural history of posterior iliac crest bone graft donation for spinal surgery: a prospective analysis of morbidity.

STUDY DESIGN: A prospective study was conducted to examine bone graft donor site morbidity in 106 consecutive patients undergoing posterior spinal fusion. OBJECTIVES: To perform a prospective analysis of donor site morbidity, to document the incidence of major complications, and to collect information on the impact of autologous bone graft harvesting from the posterior iliac crest on the overall outcome of spinal surgery. SUMMARY OF BACKGROUND: Bone graft harvesting from the posterior iliac crest for spinal fusion is a source of significant morbidity. Previous retrospective case studies indicate that minor complications are common, but they do not define the natural history and complications of posterior iliac crest bone graft harvesting. METHODS: A standardized harvesting technique was used. At 3, 6, and 12 months after surgery, the patients completed a proforma questionnaire rating symptoms on a visual analog scale and underwent a postoperative examination by the surgeon. Finally, overall surgical outcome was assessed at 12 months. RESULTS: The major component of morbidity is donor site pain. Mean pain scores were 1.640 at 3 months, 1.812 at 6 months, and 1.207 at 12 months. The pain at 12 months was significantly less than at 3 and 6 months (P = 0.005), with a trend toward the highest scores at 6 months. A pain score of 0 was reported by 55% of the patients. Local sensory loss was found in 10% of the patients. Outcome assessment showed significant differences in morbidity for surgery performed at different spinal levels (P = 0.001), with lumbosacral surgery resulting in worse outcomes than either cervical (P < 0.05) or thoracolumbar (P < 0.05) surgery. Significantly higher visual analog scores were observed at 6 months in patients with poorer overall outcomes. CONCLUSIONS: According to this study, it is reasonable to reassure patients that a good result from spinal surgery will not be compromised by severe symptoms or major morbidity secondary to posterior iliac crest bone graft donation. Before surgery, patients may be advised concerning the risks of donor site pain, which improves significantly by 12 months, local tenderness, and uncommonly localized sensory loss.     

脊柱结核病灶清除并椎间支撑植骨术后并发症的防治

目的 探讨脊柱结核病灶清除并椎间支撑植骨术后并发症的防治方法.方法 2000年1月—2015年12月,宁夏医科大学总医院采用病灶清除并椎间支撑植骨术治疗脊柱结核患者326例.通过术后X线片、MRI及CT分析植骨融合情况及植骨相关并发症发生情况.结果 所有患者术后化疗3～36(7.89±5.92)个月,结核灶全部治愈、植骨融合后停药,无新的结核灶形成.共使用348个植骨材料,其中髂骨290个,多根肋骨捆绑20个,肋髂骨捆绑26个,钛网12个.术后植骨融合过程中发生植骨倾斜9例(2.8％),植骨骨折8例(2.5％)、植骨吸收4例(1.2％)、植骨下沉3例(0.9％)、植骨移位1例(0.3％)、假关节形成1例(0.3％),相应给予延长制动时间、辅助外固定、再次手术彻底清除病灶或硬化骨、延长用药时间等措施,直至植骨融合、病灶治愈.结论 脊柱结核病灶清除并椎间支撑植骨术后植骨融合过程中可能出现植骨块倾斜、骨折、吸收、下沉、移位及假关节形成等并发症,应注意预防并给予相应处理,促进病灶治愈和植骨融合.     

Quantitative histologic study of the influence of anterior spinal instrumentation and biodegradable polymer on lumbar interbody fusion after corpectomy. A canine model.

Histomorphometric and microradiographic studies were performed to investigate whether there are different rates of bone remodeling based on the intrinsic stability with anterior spinal instrumentation and to evaluate if biodegradable polymer could be used clinically as the material of choice for anterior spinal instrumentation. Twenty-one coon hounds underwent anterior and posterior spinal destabilizing procedures to produce a reproducible amount of spinal instability: corpectomy of L5, discectomies and partial facetectomies of L4-5 and L5-6, resections of L5 lamina, spinous process, supra- and interspinous ligament, and ligamentum flavum. Group 1 (N = 7) underwent anterior autogenous ulna strut graft alone at L4-6; group 2 (N = 7) underwent anterior biodegradable polymer strut alone at the same level; group 3 (N = 7) underwent same bone graft as in group 1, augmented by anterior Kaneda device. Six months after surgery quantitative histologic study showed that device-related osteopenia occurred in spines treated with Kaneda device. Within the L5 vertebral body the volumetric density of bone (mm3/cm3) was less for the group with Kaneda device (group 3) compared with that without instrumentation (group 1, P less than 0.05). In the spine treated with biodegradable polymer, no adverse host tissue responses were observed histologically. In addition, osteoconductive abilities of the polymer were suggested microscopically. Its mechanical property, however, was not rigid enough to stabilize the corpectomized spine.     

The efficacy of different commercially available demineralized bone matrix substances in an athymic rat model

OBJECTIVE: Bone graft substitutes have been developed because there is a limited supply of autogenous graft and the harvesting of iliac crest bone graft is associated with significant morbidity. Currently, there are a number of different commercially available demineralized bone matrix (DBM) products available that have been prepared by different methods and have different carriers. The objective of this study was to compare eight different commercially available DBM products. METHODS: Eight different DBMs were used to attempt a spinal fusion between the L4-L5 transverse processes in athymic rats. There were 10 rats in each group, and 5 rats were killed at both 4 and 8 weeks. Radiographic and histologic analyses were performed. Manual palpation testing was also performed. RESULTS: At 4 weeks, Osteofil Paste had the highest radiographic scores, whereas Grafton Putty had the best radiographic scores at 8 weeks. Conversely, the spines implanted with Allomatrix had the lowest radiographic scores at both 4 and 8 weeks. In regard to forming a spinal fusion confirmed by manual palpation, Osteofil Paste was the most effective at 4 weeks, whereas Grafton Flex and Grafton Putty had the highest rate of fusion at 8 weeks. Conversely, the lowest rates of fusion were seen in the Allomatrix and Grafton Crunch groups. Statistical analysis showed that there were significant differences among the groups seen on radiographs and by manual palpation. Qualitative differences could be appreciated between the groups histologically. CONCLUSION: Significant differences exist among commercially available DBMs in forming a spinal fusion in an athymic rat.     

Effects of autogenous bone graft impaction and tricalcium phosphate on anterior interbody fusion in the porcine lumbar spine

Background Impaction grafting can be achieved inside the spinal fusion cages, but its effect on bone graft incorporation and spinal fusion has not been studied. Animals and methods We investigated the effect of impaction grafting on the bone graft healing and fusion potential of beta-tricalcium phosphate (beta-TCP) inside the carbon fiber reinforced spinal fusion device (Brantigan cage) in 10 Danish landrace pigs. Lumbar spine interbody fusion of L2/3, L4/5 and L6/7 using carbon fiber cages was performed on each pig. Cages filled with either loosely-packed autologous iliac bone graft, rod-impacted autologous bone graft or beta-TCP were randomly distributed to the three fusion levels. Half of the animals were followed for 8 weeks, and the other half for 16 weeks. Results Radiographs and CT evaluations showed that autograft levels had significantly better results than beta-TCP levels (p<0.001 Fisher's Exact Test). However, the difference between impacted and loosely-packed levels was not significant. Histomorphometric analysis showed no difference between the loosely-packed and impacted cages with regard to bone volume, bone marrow volume, cartilage and fibrous tissue volume, while both of the autograft levels differed from the beta-TCP levels in all of the aforementioned parameters. Fluorochrome studies demonstrated that bone mineral apposition rate was significantly higher in the impacted cages than in the loosely-packed cages at 16 weeks. Interpretation Manual impaction of autologous bone graft into the carbon fiber cages resulted in a faster mineral apposition rate by 16 weeks. Bone ingrowth and spinal fusion were not influenced by impaction grafting.     

一期后路病灶清除内固定椎体间植骨治疗脊柱结核

目的探讨一期后路病灶清除内固定椎体间植骨融合术治疗脊柱结核的临床效果。方法 2006年7月~2013年9月,对36例胸腰段脊柱结核患者均采用一期后路病灶清除内固定椎体间植骨融合术治疗。后路内固定采用椎弓根螺钉系统,病灶清除后采用结构性支撑,自体大块髂骨植骨9例,椎间融合器椎间植骨并自体髂骨骨粒植骨27例。结果平均随访22个月,所有病例植骨均骨性融合,内固定无松动、断裂,3例有神经功能障碍者恢复良好。结论脊柱结核手术治疗中,后路病灶清除内固定是安全有效的。后路植骨融合率高,是一种较好的手术方式。     

Effects of autogenous bone graft impaction and tricalcium phosphate on anterior interbody fusion in the porcine lumbar spine

Background?Impaction grafting can be achieved inside the spinal fusion cages, but its effect on bone graft incorporation and spinal fusion has not been studied. Animals and methods?We investigated the effect of impaction grafting on the bone graft healing and fusion potential of ß-tricalcium phosphate (ß-TCP) inside the carbon fiber reinforced spinal fusion device (Brantigan cage) in 10 Danish landrace pigs. Lumbar spine interbody fusion of L2/3, L4/5 and L6/7 using carbon fiber cages was performed on each pig. Cages filled with either loosely-packed autologous iliac bone graft, rod-impacted autologous bone graft or ß-TCP were randomly distributed to the three fusion levels. Half of the animals were followed for 8 weeks, and the other half for 16 weeks. Results?Radiographs and CT evaluations showed that autograft levels had significantly better results than ß-TCP levels (p<0.001 Fisher's Exact Test). However, the difference between impacted and loosely-packed levels was not significant. Histomorphometric analysis showed no difference between the loosely-packed and impacted cages with regard to bone volume, bone marrow volume, cartilage and fibrous tissue volume, while both of the autograft levels differed from the ß-TCP levels in all of the aforementioned parameters. Fluorochrome studies demonstrated that bone mineral apposition rate was significantly higher in the impacted cages than in the loosely-packed cages at 16 weeks. Interpretation?Manual impaction of autologous bone graft into the carbon fiber cages resulted in a faster mineral apposition rate by 16 weeks. Bone ingrowth and spinal fusion were not influenced by impaction grafting.     

Complete pelvic ring failure after posterior iliac bone graft harvesting.

STUDY DESIGN: Case report. OBJECTIVE: To present a rare complication of posterior iliac bone graft harvesting. SUMMARY OF BACKGROUND DATA: Although iliac bone graft harvesting is a common procedure in spinal surgery, it is not without complications. One such complication is fracture of the ilium that is seen most often in older women with osteopenia. METHOD: In this case a severe complication of posterior iliac bone graft harvesting was identified in a patient with steroid-induced osteoporosis that led to multiple pelvic fracture, nonunions, and eventual failure of the entire pelvic ring. Imaging studies showed osteoporotic bone and multiple nonunions of the pelvis with structural collapse. RESULTS: Staged sequential platings of the iliac wings were performed to stabilize the pelvis. The initial fixation of the left iliac wing apparently united after hardware failure. The right iliac wing was successfully fixed with plates supplemented with bone cement and allograft. Anterior fixation was planned. CONCLUSIONS: Care should be taken when considering autograft harvesting in patients with risk factors for osteoporosis. The outcome could be debilitating.     

Safety of recombinant human bone morphogenetic protein-2 after spinal laminectomy in the dog

STUDY DESIGN: This was a randomized, blinded trial of the safety of the application of recombinant human bone morphogenetic protein (rhBMP)-2 or autologous bone graft onto a laminectomy defect of the dog in the presence or absence of a dural membrane puncture. OBJECTIVE: To test the safety of rhBMP-2 in an application in which direct contact of the material with neural tissue occurs. SUMMARY OF BACKGROUND DATA: Application of rhBMP-2 in laboratory animals stimulates local bone formation to effect spinal fusion and healing of segmental bone defects. The use of rhBMP-2 as a bone graft substitute in spinal fusion would eliminate donor site morbidity and may augment the rate of successful fusion. Because rhBMP-2 may unintentionally come in contact with neural tissue, the consequences of such a safety issue must be addressed in an animal model before human trials. METHODS: Twenty skeletally mature beagles underwent spinal exposure followed by bilateral laminectomy at L5. In half of the dogs, a puncture wound was made to the dura with the expression of cerebrospinal fluid at the site of the puncture. In randomly selected animals, the exposed dural elements received either autologous bone graft with the bone removed from the laminectomy site or an implant of the rhBMP-2 device. The animals was observed for 12 weeks with periodic clinical examinations and monthly computed tomographic scans. RESULTS: There was no clinical, radiographic, or histologic evidence of neurologic abnormalities in these animals. The rhBMP-2 stimulated bone growth in the laminectomy defect and came into direct contact with the dural membrane. There was no evidence of abnormal mineralization within the thecal sac or in the spinal cord itself. CONCLUSIONS: The rhBMP-2 implant stimulated bone formation in the laminectomy site. Neither autologous bone, rhBMP-2, nor the dural puncture had deleterious consequences for the animals.