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S D Boden

Publications and source records attributed to S D Boden.

At least 73 records · Page 4Linked to original sources
PubMed1996

Do diurnal changes in loading affect the interpretation of MRI scans of the lumbar spine?

We tested the hypothesis that the visual interpretation of magnetic resonance imaging (MRI) scans of the asymptomatic lumbar spine are affected by diurnal changes in fluid exchange in the intervertebral discs. Ten male subjects carried a 20-kg backpack in the intervening 3-h period between two MRI scans of the lumbar spine. After the subjects arrived at the MRI center (within 45 min of awakening), they lay on a bed for 45 min. The first set of MRI scans were obtained. Each subject was then fitted with a 20-kg backpack. After they walked for 3 h, the pack was removed, and a second set of MRI scans were obtained immediately. The sets of MRI scans were reviewed by three radiologists: none of the three radiologists found differences in the interpretation of the MRI scans. On the basis of these results, diurnal changes in fluid exchange in the asymptomatic intervertebral disc (exaggerated in our case by the backpack) are undetectable by visual reading of MRI scans.

Adult↗
PubMed1995

1995 Volvo Award in basic sciences. The use of an osteoinductive growth factor for lumbar spinal fusion. Part I: Biology of spinal fusion.

STUDY DESIGN: The histology of lumbar intertransverse process spinal fusion was studied in an experimental model in rabbits. OBJECTIVES: To qualitatively and quantitatively analyze the sequential histology of spinal fusion using a previously validated animal model. SUMMARY OF BACKGROUND DATA: Few previous studies have described the sequential histology during the posterolateral spinal fusion healing process using autogenous bone, and a basic understanding of the biology of this repair process is lacking. METHODS: Fourteen adult New Zealand white rabbits underwent single-level posterolateral lumbar intertransverse process arthrodesis with autogenous iliac bone graft. Animals were killed 1-10 weeks after surgery, and the fusion masses were analyzed histologically and quantitated using a semiautomated image analysis system. RESULTS: Three distinct phases of healing were identified (inflammatory, reparative, and remodeling) and occurred in sequence but in a delayed fashion in the central zone of the fusion mass compared with the outer transverse process zones. Membraneous bone formation, evident first at the ends of the fusion eminating from the decorticated transverse processes, was the predominant mechanism of healing. The central zone was somewhat different in that there was a period of endochondral bone formation during weeks 3 and 4 in this zone where cartilage formed and was converted to bone. Remodeling in the central zone had equilibrated with the transverse process zones by 10 weeks. CONCLUSIONS: Lumbar intertransverse process spinal fusion is a complex process from a spatial and temporal standpoint. When autogenous bone is used as the graft material, this process critically depends on a variety of factors from the decorticated host bone and exposed marrow. The persistence of a central cartilage zone may be related to some types of nonunions and deserves future investigation. This enhanced understanding of the biology of spinal fusion with autogenous bone graft will provide a foundation for optimizing the use of osteoinductive bone growth factors in this healing process.

Animals↗
PubMed1995

1995 Volvo Award in basic sciences. The use of an osteoinductive growth factor for lumbar spinal fusion. Part II: Study of dose, carrier, and species.

STUDY DESIGN: Efficacy of a bovine-derived osteoinductive growth factor was studied in a rabbit model and in a nonhuman primate model of posterolateral lumbar spinal fusion. OBJECTIVES: To determine the minimum effective dose of growth factor and the influence of different carrier material on the outcome of intertransverse process lumbar fusion. SUMMARY OF BACKGROUND DATA: Bone morphogenetic proteins and related growth factors are becoming increasingly available in purified extract or genetically engineered forms and are capable of inducing new bone formation in vivo. Osteoinductive growth factors to enhance lumbar spinal infusion have not been well studied in models of posterolateral intertransverse process fusion. Because of the diminished potential of bone regeneration in primates (including humans) compared with phylogenetically lower animals, extrapolations regarding dose and efficacy cannot be made directly from results obtained in experiments performed on phylogenetically lower animals. Experiments on non-human primates are a critical step before attempting to use these growth factors on humans. METHODS. One hundred fifteen adult New Zealand white rabbits and 10 adult rhesus macaques underwent single level posterolateral intertransverse process lumbar spinal arthrodesis to evaluate different doses and carrier materials for a bovine-derived osteoinductive bone protein extract. Rabbit fusion masses were evaluated 5 weeks after arthrodesis by manual palpation, radiography, biomechanical testing, and light microscopy. Monkey fusion masses were evaluated 12 weeks after arthrodesis by radiography and light microscopy. RESULTS: Successful posterolateral intertransverse process spinal fusions were achieved in the rabbit models using an osteoinductive growth factor with three different carriers (autogenous iliac bone, demineralized allogeneic bone matrix, and natural coral). There was a dose-dependent response to the osteoinductive growth factor in the rabbit model, indicating that a threshold must be overcome before bone formation is induced. The methodology for biologic enhancement of spinal fusion developed in the rabbit model transferred successfully to the rhesus monkey, where the use of the osteoinductive growth factor with a demineralized bone matrix carrier resulted in spinal fusion in 12 weeks. CONCLUSION: These experiments provide an essential building block in the understanding of the biology of spinal fusion and the use of osteoinductive growth factors to enhance a posterolateral intertransverse process spinal fusion. The achievement of posterolateral spinal fusion in the rhesus monkey using an osteoinductive growth factor is a significant step toward the biologic enhancement of spinal fusion in humans.

Animals↗
PubMed1995

Biologic factors affecting spinal fusion and bone regeneration.

STUDY DESIGN: Literature review. OBJECTIVES: This article reviews the existing data on the multiplicity of local and systemic factors affecting lumbar spinal fusion and the general biology of bone regeneration. SUMMARY OF BACKGROUND DATA: Arthrodesis is one of the most commonly performed, yet incompletely understood, procedures in spinal surgery. There exists a paucity of knowledge about the basic biology involved in achieving a successful fusion. METHODS: Medline and manual search of all relevant articles were performed and summarized. RESULTS: The success or failure of spinal fusion may be influenced by a host of local and systemic factors. CONCLUSIONS: Future research should focus on expanding our existing knowledge pertaining to the basic biology of bone regeneration specific to spinal fusion.

Bone Regeneration↗
PubMed1995

Biologic enhancement of spinal fusion.

STUDY DESIGN: Literature review. OBJECTIVES: To review the available animal and clinical data on biologic enhancements of spinal fusion. SUMMARY OF BACKGROUND DATA: Lumbar spinal arthrodesis may result in pseudarthrosis in 5% to 35% of patients. Although much research has focused on the mechanical factors affecting spinal fusion, the use of internal fixation has not eliminated the problem of spinal nonunions. Accordingly, biologic enhancement of spinal fusion has become an important focus of spinal research. METHODS: Medline and hand searches. RESULTS: Electric stimulation, bone graft substitutes, and bone growth factors have been researched most extensively. Electric stimulation and early attempts at bone graft substitutes (allograft, xenograft) have yielded variable results. The feasibility of biologic enhancement of spinal fusion with osteoinductive growth factors has been shown in animals. CONCLUSION: The efficacy of bone growth factors for lumbar fusion remains to be definitively established in humans.

Animals↗
PubMed1995

The effect of nicotine on incorporation of cancellous bone graft in an animal model.

STUDY DESIGN: A basic science study using a rabbit model of bone graft revascularization in the distal femoral metaphysis. OBJECTIVES: The goal of the present study was to determine the effect of nicotine on the revascularization and incorporation of autogenous iliac crest bone graft implanted in an orthotopic location. SUMMARY OF BACKGROUND DATA: Although nicotine is the major toxin in cigarettes, it has not been confirmed as the primary factor affecting bone metabolism, and although the effects of smoking on bone homeostasis have been well studied, the effect of nicotine on new bone formation and neovascularization in the setting of bone graft transplantation has not been well studied. METHODS: Twenty-four New Zealand white rabbits were randomly divided into two groups to be exposed to nicotine or saline control. A cancellous iliac crest bone graft was harvested and implanted in the lateral distal femur. Mini-osmotic pumps were used to deliver continuous serum levels of nicotine. The animals were killed at the following intervals: 1 week (n = 6), 2 weeks (n = 12), and 4 weeks (n = 6). The vascular tree was injected with Microfil silicone rubber solution, and the degree of revascularization was determined with a semiautomated image analysis system to determine the area of vascularization for each specimen. RESULTS: All seven of the control (no nicotine) animals harvested at 1 or 2 weeks had over 50% bony vascular ingrowth, whereas only four of the nine nicotine-exposed animals showed over 50% bony vascular ingrowth. These differences were statistically significant (P = 0.03) using the Fischer exact test. By the fourth week (after nicotine levels in experimental animals had diminished), the revascularization of the nicotine-exposed grafts was indistinguishable from that of grafts in the animals that were not exposed to nicotine. CONCLUSIONS: We conclude the following. 1) Uniform dosages of nicotine in the rabbit model decreases the vascular ingrowth into autogenous cancellous bone graft. 2) The inhibitory effect of nicotine varies between animals, suggesting predisposition in some. 3) The vascular effects are reversible within 2 weeks of elimination of nicotine, although late bony resorption continues beyond the time of high serum nicotine levels.

Animals↗
PubMed1995

The effect of nicotine on spinal fusion.

STUDY DESIGN: An animal model of posterior lateral intertransverse process fusion healing in the face of systemic nicotine. OBJECTIVES: To evaluate the effect of systemic nicotine on the success of spinal fusion and its effect on the biomechanic properties of a healing spinal fusion in an animal model. SUMMARY OF BACKGROUND DATA: Clinical observations suggested that cigarette smoking interferes with the healing of bony fusion. No direct link has been made to implicate nicotine as a cause for impaired healing of spinal fusions or fractures. METHODS: Twenty-eight adult female New Zealand white rabbits underwent single level lumbar posterior lateral intertransverse process fusion using autologous iliac bone graft. Animals were randomly assigned to either receive systemic nicotine or receive no nicotine. Animals were killed 35 days after surgery. Manual testing of the fusion mass was performed to determine the fusion status. Each fusion mass underwent biomechanic testing. RESULTS: Fifty-six percent of the control animals were judged to have solidly fused lumbar spines, and there were no solid fusions in the nicotine group (P = 0.02). The mean relative fusion strength in the control group was greater (P = 0.09) than in the nicotine group. For the comparable stiffness figures, the control group was greater than the nicotine group (P = 0.08). CONCLUSIONS: This animal model established a direct relationship between the development of a nonunion in the presence of systemic nicotine. The results suggested that bone formed in the face of systemic nicotine may have inferior biomechanic properties.

Animals↗
PubMed1995

Experimental spinal fusion with recombinant human bone morphogenetic protein-2.

STUDY DESIGN: Lumbar intertransverse process arthrodesis using recombinant human bone morphogenetic protein-2 was performed in a previously established rabbit model for posterolateral spinal fusion and compared with fusions achieved using autogenous bone graft. OBJECTIVES: To qualitatively compare different recombinant human bone morphogenetic protein-2 dosages and carriers and to determine the efficacy of recombinant human bone morphogenetic protein-2 as a bone graft substitute to produce lumbar intertransverse process fusion in a validated rabbit model for posterolateral spinal fusion. SUMMARY OF BACKGROUND DATA: Autogenous bone was considered the most successful bone graft material used for spinal arthrodesis. Problems with its use may occur in 25-30% of patients and prompted the search for and investigation of bone graft substitutes and osteoinductive growth factors, such as bone morphogenetic proteins. Recombinant human bone morphogenetic protein-2 was used successfully in orthotopic sites to generate bone in animal mandibular and long bone defect models. METHODS: Posterolateral intertransverse process arthrodeses were performed at L5-L6 in 56 rabbits using recombinant human bone morphogenetic protein-2 or autogenous bone graft. Rabbits were killed either 5 weeks later to qualitatively compare fusions achieved using different recombinant human bone morphogenetic protein-2 dosages and carriers or 4 weeks later to compare the efficacy of recombinant human bone morphogenetic protein-2 in achieving spinal fusion compared with using autogenous bone graft. Inspection, manual palpation, radiography, histology, and biomechanic testing were used to assess the fusion. RESULTS: All rabbits implanted with recombinant human bone morphogenetic protein-2 achieved solid spinal fusion by manual palpation and were fused radiographically, whereas only 42% of the autograft control fusions were solid. More mature fusions with greater trabecular bone formation were shown radiographically and histologically in rabbits implanted with the high-dose recombinant human bone morphogenetic protein-2 than with the low-dose recombinant human bone morphogenetic protein-2. Fusions achieved using recombinant human bone morphogenetic protein-2 delivered in the collagen carrier were more remodeled and homogeneous compared with using recombinant human bone morphogenetic protein-2 delivered in autograft +/- collagen carrier. Fusions achieved with recombinant human bone morphogenetic protein-2 were biomechanically stronger and stiffer than fusions achieved using autogenous bone graft. CONCLUSIONS: Recombinant human bone morphogenetic protein-2 successfully and reliably achieved lumbar intertransverse process fusion in a validated rabbit model for posterolateral spinal fusion. Radiographically and histologically, greater and more rapid bone formation, consolidation, and remodeling were shown with recombinant human bone morphogenetic protein-2 compared with autogenous bone graft. Fusions achieved with recombinant human bone morphogenetic protein-2 were biomechanically stronger and stiffer than autograft fusions.

Animals↗
PubMed1995

An experimental lumbar intertransverse process spinal fusion model. Radiographic, histologic, and biomechanical healing characteristics.

OBJECTIVE: The purpose of this investigation was to develop, characterize, and validate an animal model for lumbar intertransverse process fusion. STUDY DESIGN: This study used a rabbit model to characterize the radiographic, histologic, and biomechanical properties of the intertransverse process spinal fusion healing process. METHODS: Sixty adult New Zealand white rabbits underwent bilateral posterolateral spinal fusion at L5-L6 using autogenous iliac bone graft. Four of the rabbits were used as negative controls: two received bone graft without decortication of the transverse process, and two underwent decortication without bone grafting. Rabbits were killed at 2, 3, 4, 5, 6, or 10 weeks and the spinal fusions were analyzed by radiography, manual palpation, and uniaxial tensile mechanical testing or light microscopy. RESULTS: Overall the nonunion rate was 33% in animals 4 or more weeks from surgery. Biomechanical strength and stiffness of the fusions became statistically different from the adjacent unfused control levels after the third week (P < 0.05). Tensile strength of the nonunions (1.4 times unfused control levels) was statistically less (P < 0.05) than that of the solidly fused levels (1.8 times unfused controls) in weeks 4, 5, 6, and 10. Fusion was not achieved in any of the control animals with omission of decortication or bone grafting. Light microscopic analysis showed three distinct and reproducible phases of spinal fusion healing. CONCLUSIONS: This animal model overcomes the limitations of previous models by more closely replicating the human procedure in surgical technique, graft healing environment, and outcome (i.e., a nonunion rate similar to that seen in humans). This model provides an opportunity to explore questions relevant to the biology of intertransverse process fusion and to investigate the coupling of the membranous and endochondral mechanisms of bone formation during spinal fusion.

Animals↗
PubMed1995

Lumbar intertransverse-process spinal arthrodesis with use of a bovine bone-derived osteoinductive protein. A preliminary report.

The use of a bovine bone-derived osteoinductive protein extract as a bone-graft substitute was evaluated in a rabbit model of intertransverse process arthrodesis of the lumbar spine. Forty-five adult New Zealand White rabbits had arthrodesis between the fifth and sixth lumbar vertebrae with use of one of three graft materials: autogenous iliac-crest bone, osteoinductive protein delivered in an allogeneic demineralized bone matrix/collagen carrier, or demineralized bone matrix/collagen carrier or demineralized bone matrix/collagen carrier without osteoinductive protein. Fusion was assessed by manual palpation, radiography, biomechanical testing, and light microscopy at two and five weeks after the operation. At two weeks, light microscopic analysis of the arthrodesis site in which osteoinductive protein had been used showed that most of the demineralized bone matrix was still present, with small amounts of membranous and endochondral bone formation at the peripheral margins of the implant. Light microscopic analysis of the five-week specimens showed increased new-bone formation and a more homogeneous and mature fusion mass with the osteoinductive bone protein than with the autogenous bone graft. At five weeks, the fusions with the osteoinductive protein extract were characterized by more secondary spongiosa, with formation of bone marrow centrally and a cortical rim peripherally. Of the thirty-five rabbits that were examined at five weeks, all ten in the group that had received osteoinductive bone protein had a solid fusion, but the rate of fusion was significantly less in the other two groups: eight of thirteen rabbits (p = 0.05) in the group that had received autogenous bone graft and two of twelve rabbits (p = 0.0001) in the group that had received demineralized bone matrix/collagen carrier without osteoinductive bone protein. The use of osteoinductive bone protein resulted in stronger (p = 0.02) and stiffer (p = 0.005) fusions compared with those obtained with the use of autogenous iliac-crest graft.

Animals↗
PubMed1995

Lumbar spine after surgery for herniated disk: imaging findings in the early postoperative period.

Imaging the lumbar spine after surgery for disk herniation is all too often an unrewarding challenge. A constellation of findings is inevitable, and determining their significance is often impossible. The challenge is greatest during the first few months following surgery, when the rules of scar enhancement, deformity, and mass effect do not apply to differentiation of the abnormal from the normal. A clear understanding of normal postoperative healing is necessary to avoid overreaction to misleading findings. This report reviews imaging of the lumbar spine in the early postoperative period (i.e., the first 6 months after surgery), focusing on the normal healing process that so often mimics complicating or recurrent disease.

Cicatrix↗
PubMed1994

Spine update. Animal use in spinal research.

Progress in biomedical research often has depended on the use of animals as a testing ground for both experimental and clinical hypotheses. Animal models have been widely used in all specialties of medicine and have been crucial for acquiring basic science and clinical knowledge pertaining to spinal surgery. In addition to overcoming the many ethical and societal restrictions normally encountered in human studies, the use of animal models permits certain methodologic approaches inapplicable in humans. The purpose of this article is to: 1) review the general concepts of models, 2) discuss recommendations and regulations regarding the use of animals in biomedical research, and 3) present guidelines for the selection of the most suitable model for a particular study. Animal data are only as applicable as the model from which it is derived. Thus, future animal models must be carefully chosen using rational guidelines and should overcome the deficiencies and limitations of previous models.

Animals↗