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S D Boden

Publications and source records attributed to S D Boden.

At least 55 records · Page 3Linked to original sources
PubMed1998

Bone repair and enhancement clinical trial design. Spine applications.

Spine fusion represents over half of all current bone grafting procedures. It is an important clinical area for bone augmentation because use even of the most successful graft material, autogenous iliac crest bone, is fraught with an unacceptably high failure rate. Various new options that biologically will control bone induction currently are under development. To prevent unnecessary clinical failures, it is important that surgeons understand the principles of clinical trial design, whether they actively are using the reported results or simply reviewing them in an effort to decide if they will use the new technology in their own practice. This review highlights the important issues relevant to designing a clinical trial for studying the efficacy of a bone augmentation product in a spine application. Some of the design challenges are generic, but others are unique to the spine because of difficulty in defining a clear diagnostic group, difficulty in noninvasively assessing the technical success of surgery, and frequent dissociation of the clinical and radiographic results.

Bone Regeneration↗
PubMed1998

LMP-1, a LIM-domain protein, mediates BMP-6 effects on bone formation.

Glucocorticoids can promote osteoblast differentiation from fetal calvarial cells and bone marrow stromal cells. We recently reported that glucocorticoid specifically induced bone morphogenetic protein-6 (BMP-6), a glycoprotein signaling molecule that is a multifunctional regulator of vertebrate development. In the present study, we used fetal rat secondary calvarial cultures to determine genes induced during early osteoblast differentiation as initiated by glucocorticoid treatment. Glucocorticoid, and subsequently BMP-6, was found to induce a novel rat intracellular protein, LIM mineralization protein-1 (LMP-1), that in turn resulted in synthesis of one or more soluble factors that could induce de novo bone formation. Blocking expression of LMP-1 using antisense oligonucleotide prevented osteoblast differentiation in vitro. Overexpression of LMP-1 using a mammalian expression vector was sufficient to initiate de novo bone nodule formation in vitro and in sc implants in vivo. These data demonstrate that LMP-1 is an essential positive regulator of the osteoblast differentiation program as well as an important intermediate step in the BMP-6 signaling pathway.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Laparoscopic anterior spinal arthrodesis with rhBMP-2 in a titanium interbody threaded cage.

Anterior lumbar interbody arthrodesis is commonly performed for conditions involving infection, deformity, and instability. The purpose of this investigation was to determine the effective dose of recombinant human bone morphogenetic protein-2 (rhBMP-2) as a bone graft substitute inside a titanium threaded interbody fusion cage using a nonhuman primate model of laparoscopic anterior lumbar interbody arthrodesis. Eight adult rhesus monkeys underwent laparoscopic exposure of the lumbosacral spine followed by insertion of a hollow titanium threaded cylindrical cage (Sofamor-Danek, Memphis, TN, U.S.A.). Before insertion, the chamber of the cage was filled with a collagen sponge delivery vehicle soaked with either 0 mg/ml (sham, buffer only), 0.75 mg/ml (low dose), or 1.5 mg/ml (high dose) of rhBMP-2 (Genetics Institute, Cambridge, MA, U.S.A.). Fusions were evaluated in a blinded fashion with plain radiographs and computed tomography (CT) scans 12 and 24 weeks after surgery, and by manual palpation and histology after euthanasia 24 weeks after surgery. All five monkeys treated with a cage filled with rhBMP-2 obtained a solid fusion as assessed by manual palpation. The two monkeys that received no growth factor did not achieve solid fusions. Plain radiographs were of limited value, with fusions best assessed on sagittally reconstructed CT scans. Scans from the two animals treated without growth factor showed ingrowth of bone only into the outer edges of the cage, but not through the center. Scans from the rhBMP-2-treated animals demonstrated arthrodesis with continuous bone growth through the cage. Histologic analysis demonstrated normal mature trabecular bone surrounding and growing through the cages, which correlated with the CT scan findings. We conclude that rhBMP-2 delivered in a threaded titanium interbody cage can serve as a bone graft substitute in a nonhuman primate model. Sagittal reconstructed CT may be a better method to assess for fusion with this device.

Animals↗
PubMed1998

The Marshall R. Urist Young Investigator Award. Gene expression during autograft lumbar spine fusion and the effect of bone morphogenetic protein 2.

A prospective animal study of posterolateral lumbar spine arthrodesis was performed to determine the temporal and spatial pattern of gene expression and to determine the effect of recombinant human bone morphogenetic protein 2 on the gene expression pattern of a healing spine fusion mass. In Group 1, 20 adult New Zealand rabbits underwent L4-L5 posterolateral intertransverse process arthrodesis using autograft alone. Two rabbits were euthanized at each of the following points: 0, 2, and 4 days, and 1, 2, 3, 4, 5, 6, and 10 weeks after surgery. The same surgical technique was used for 16 rabbits in Group II, except that the autograft first was soaked in a solution of recombinant human bone morphogenetic protein 2 before implantation. Ribonucleic acid was extracted from different regions of the fusion mass at each point and analyzed for expression of bone and cartilage related genes using reverse transcription polymerase chain reaction. A reproducible temporal sequence and spatial pattern of gene expression was found in healing spine fusions. In the central portion of the fusion mass a temporal lag in gene expression was observed that parallels the lag in healing within the central zone previously observed in histologic studies. Treatment of bone graft with recombinant human bone morphogenetic protein 2 resulted in an increase in the early expression of bone morphogenetic protein 6 which was associated with expression of higher levels of Type I collagen, osteocalcin, and other bone related genes. These findings suggest that central nonunion may be associated with delayed expression of osteoblast related genes in the central region of the forming fusion mass. The growth factor, recombinant human bone morphogenetic protein 2, increased the level of bone related gene expression throughout the fusion mass, eliminated the delay in healing within the central zone, and may decrease the likelihood of a nonunion.

Animals↗
PubMed1998

Biomechanical study of lumbar pedicle screws: does convergence affect axial pullout strength?

We tested the hypothesis that two pedicle screws placed in convergence offer more resistance to axial pullout than do two pedicle screws placed in parallel. Eight fresh cadaveric lumbar spines, L2-L5, were harvested. Individual vertebra were then paired for testing. Into each L2 and L3 vertebra, a pair of pedicle screws were inserted. The screws were placed parallel (i.e., at 0 degrees convergence) in L2 and at 30 degrees convergence in L3, in the first pair. In the second pair of L2 and L3, this order was reversed. Alternating the convergence angle was carried out on each successive pair of L2 and L3. A section of standard longitudinal rod was attached to each pedicle screw by using top-loading three-point shear clamp fixation with tangential lock screws. Transverse connectors were attached superiorly and inferiorly to the longitudinal rods. As in L2 and L3, each L4 and L5 received a pair of screws placed at either 0 or 30 degrees convergence, with the angle of convergence alternated on each successive pair. Each pair of screws in each vertebra was tested in axial pullout at 1 mm/s. Fourteen pairs of vertebra were tested and two findings emerged: paired pedicle screws at 30 degrees of convergence offered more resistance to axial pullout (28.6% on average) and sustained higher loads at the clinical threshold of loosening (101% on average) than paired pedicle screws placed in parallel. Thus there seems to be an advantage to screws placed in 30 degrees of convergence as compared with screws in parallel.

Bone Screws↗
PubMed1998

An assessment of the early management of spine problems and appropriateness of diagnostic imaging utilization.

Low back pain may affect up to 80% of all adults and is the second leading reason for physician visits in ambulatory medicine. Estimates for the annual direct medical costs for treating patients with back pain approach $25 million, despite the fact that it is a self-limited condition in at least 90% of patients with recovery occurring within 6 to 12 weeks. Recent scrutiny of health care delivery has produced numerous observations documenting a high variability in use of resources for medical conditions including low back pain, but few studies have attempted to examine the medical appropriateness of diagnostic and therapeutic decisions.

Adult↗
PubMed1998

Management of low back pain. Current assessment and formulation of a blueprint for the health care delivery system of the future.

This article outlines the authors' recommendations for future health care delivery to patients with low back pain and presents one potential blueprint for a modified delivery system. A group of multidisciplinary physicians and support staff that functions as a unified team with common goals is best positioned to overcome the challenges of providing quality care in a managed care environment. The burden on those who manage patients with spine disorders is to define and prove that high quality medical care results in genuine cost savings and better value for the health care customer.

Cost Savings↗
PubMed1997

Glucocorticoid-induced differentiation of fetal rat calvarial osteoblasts is mediated by bone morphogenetic protein-6.

Glucocorticoids (GCs) at physiological concentrations promote osteoblast differentiation from fetal calvarial cells, calvarial organ cultures, and bone marrow stromal cells; however, the cellular pathways involved are not known. Bone morphogenetic proteins (BMPs) are recognized as important mediators of osteoblast differentiation. Specific roles for individual BMPs during postembryonic membranous bone formation have yet to be determined. We recently reported that GC potentiated the osteoblast differentiation effects of BMP-2 and BMP-4, but not of BMP-6, which, by itself, was the most potent of the three. In the present study, we used fetal rat secondary calvarial cultures to study the role of BMP-6 during early osteoblast differentiation. Treatment with the GC triamcinolone (10(-9) M) resulted in a 5- to 8-fold increase in BMP-6 steady-state messenger RNA levels, peaking at 12 h. In contrast, BMPs -2, -4, -5, -7, and transforming growth factor (TGF)-beta1 messenger RNA levels increased by less than 2-fold, after GC treatment, compared with untreated control cultures at 24 h. BMP-6 protein secretion increased 6- to 7-fold by 12 h and 12-fold (from 7.5 to 90 ng/ml) by 24 h, as measured by quantitative Western analysis. Treatment of cells with oligodeoxynucleotides antisense to BMP-6 diminished secretion of BMP-6 protein and significantly inhibited the GC-induced differentiation, as determined by a 10-fold decrease in the number of mineralized bone nodules, compared with controls that were treated with sense oligonucleotides or no oligonucleotides (ANOVA, P < 0.05). The antisense oligonucleotide inhibition of differentiation was rescued by treatment with exogenous recombinant human BMP-6. We conclude that GC-induced differentiation of osteoblasts from the pluripotent precursors is mediated, in part, by BMP-6. These results suggest that BMP-6 has an important and unique role during early osteoblast differentiation.

Animals↗
PubMed1997

In vivo evaluation of a resorbable osteoinductive composite as a graft substitute for lumbar spinal fusion.

The purpose of this prospective animal study was to evaluate the efficacy of a resorbable coral particulate to serve as a carrier with several doses of a bovine-derived osteoinductive bone protein mixture. A previously validated rabbit model for posterolateral intertransverse process lumbar spinal fusion was used. Posterolateral intertransverse process arthrodeses were performed at L5-L6 in 64 adult New Zealand white rabbits. The bone graft substitute evaluated consisted of a Biocoral/collagen composite with one of four doses (0, 100, 300, or 1,000 micrograms) of a bovine-derived osteoinductive bone protein extract (BP). Fusions were assessed at 5 weeks by manual palpation, radiography, histology, and biomechanical testing. Use of the Biocoral/collagen carrier without BP resulted in no solid fusions. Biocoral/collagen with 100 micrograms BP resulted in solid fusions in 31% (4 of 13) of the rabbits. Biocoral with 300 micrograms or 1,000 micrograms BP resulted in solid spinal fusion in all rabbits (27 of 27). There were no neurologic complications related to the growth factor or carrier. Small subcutaneous collections of serous fluids were noted in 26% of the animals in the 1st postoperative week, but resolved without problems by the 5th week. Such seromas may limit the clinical utility of this growth factor-carrier combination. Biocoral/collagen combined with the appropriate dose of bovine-derived osteoinductive bone protein was efficacious as a bone graft substitute for achieving posterolateral lumbar spinal fusion in the rabbit model. A dose of 300 micrograms BP was determined as the threshold to reliability produce solid spinal fusions.

Absorption↗
PubMed1997

Analysis of chondroitin sulfate in lumbar intervertebral discs at two different stages of degeneration as assessed by discogram.

Previous studies have presented evidence that an underlying cause of intervertebral disc degeneration is related to changes in the sulfation of the proteoglycans. The sulfation of the chondroitin in cadaveric lumbar intervertebral discs, at two different stages of degeneration as assessed by discogram, were analyzed. Fourteen of 28 lumbar discs were graded 2 and the other 14 were graded 4 (i.e., more degenerated). From each disc, six regional segments were carefully isolated. Proteoglycans were solubilized from the disc tissue with 4 M GuHCl. Chondroitin sulfate chains were analyzed by diethylaminoethyl (DEAE)-Sephacel and high-performance liquid chromatography (HPLC) anion exchange chromatography. The major differences in sulfation of the chondroitin between grade 2 and grade 4 discs only occurred in the posterior central annulus and nucleus segments. The chondroitin in the posterior central nucleus segments of the grade 2 and grade 4 intervertebral discs were undersulfated as compared with the other segments, and the differences between these segments and the others were more accentuated in the grade 4 discs than in grade 2 discs.

Cadaver↗
PubMed1996

Video-assisted lateral intertransverse process arthrodesis. Validation of a new minimally invasive lumbar spinal fusion technique in the rabbit and nonhuman primate (rhesus) models.

STUDY DESIGN: Cadaveric anatomic and in vivo survival animal studies were performed to develop a new arthrodesis technique for the lumbar spine. OBJECTIVES: To examine the feasibility, efficacy, and safety of a minimally invasive lumbar intertransverse process arthrodesis technique using an osteoinductive growth factor (rhBMP-2) delivered in a collagen sponge carrier. The technique was first developed using a rabbit model and modified for the nonhuman primate (rhesus monkey), a larger animal with the most similar bone biology to humans. SUMMARY OF BACKGROUND DATA: The morbidity of conventional posterolateral lumbar intertransverse process arthrodesis includes graft donor site morbidity; paraspinal muscle devascularization, denervation, and scarring and nonunion in up to 36% of patients. Minimally invasive anterior lumbar interbody arthrodesis techniques have been developed, but these often require a metal implant and carry risks to major vessels and development of retrograde ejaculation. A minimally invasive technique for posterolateral intertransverse process arthrodesis has not been described previously. METHODS: In Part 1, we examined seven New Zealand white rabbits and five rhesus monkeys at necropsy and during nonsurvival surgeries to determine the best access routes and to develop special instruments for video-assisted lateral intertransverse process arthrodesis. In Part 2, 38 New Zealand white rabbits underwent L4-L5 intertransverse process arthrodesis: the "OPEN" group (n = 16) underwent a standard open muscle-splitting approach using rhBMP-2 (bone morphogenetic protein) and collagen as a bone graft substitute; the "video-assisted control" group (n = 6) underwent video-assisted lateral intertransverse process arthrodesis with the collagen implant only (no growth factor); and the "video-assisted-BMP" group (n = 16) underwent video-assisted lateral intertransverse process arthrodesis with rhBMP-2 and collagen as the graft material. In Part 3, rhesus monkeys (n = 4) underwent video-assisted lateral intertransverse process arthrodesis using rhBMP-2 and collagen after laminectomy of L4-L5. RESULTS: In Part 1, we identified expedient, minimally invasive routes to the intertransverse process interval appropriate for each species: an intermuscular approach for the rabbit and a lateral, extramuscular approach for the rhesus monkey. In Part 2, all rabbits in the OPEN and video-assisted-BMP groups achieved solid intertransverse process lumbar fusions when assessed at 10 weeks. There were no neurologic impairments nor any difference between the two groups in the frequency of postoperative infection or other complications. None of the animals in the video-assisted control group showed evidence of fusion. In Part 3, exposure, decortication and grafting with rh-BMP-2 and collagen was accomplished successfully in all four monkeys through the video-assisted minimally invasive approach without complications. CONCLUSION: Video-assisted lateral intertransverse process arthrodesis is a feasible, effective, and safe method of lumbar spinal fusion in the rabbit and rhesus monkey. Use of this arthrodesis procedure will minimize the morbidity of paraspinal muscle denervation and devascularization seen with open intertransverse process fusion techniques, and the use of an osteoinductive growth factor will eliminate the problem of graft donor site morbidity and possibly increase the chances for successful fusion.

Animals↗
PubMed1996

The outcome of posterolateral fusion in highly selected patients with discogenic low back pain.

STUDY DESIGN: A prospective analysis of the clinical outcome of a consecutive series of patients treated with posterior lumbar arthrodesis. Preoperative data were collected retrospectively by chart review. OBJECTIVES: To measure by independent review the clinical outcome of posterolateral intertransverse fusion as a treatment for discogenic low back pain in a highly selected group of patients. SUMMARY OF BACKGROUND DATA: Although numerous studies have reported on the surgical management of degenerative disc disease, they have been difficult to interpret because they lack patient-oriented outcome assessment and objective pain measurement criteria, independent review, and include patients with diagnoses other than degenerative disc disease. METHODS: Between 1991 and February 1993 all patients seen by a single surgeon, evaluated with magnetic resonance imaging and discography, and treated with posterolateral lumbar fusion were reviewed by independent investigation. Outcome was assessed in the areas of radiographic fusion, pain, function, and patient satisfaction. RESULTS: Twenty-three patients (12 women, 11 men; 100% follow-up an average of 47 months after surgery [range, 24-84 months]) met the inclusion criteria. Overall, 39% had a good or excellent result, 13% fair, and 48% poor. Nine of 10 patients receiving worker's compensation had a poor result, four of five patients with radiographic pseudarthrosis had a poor result. Statistically significant improvement in the visual analogue scale was noted in the good and excellent group (P = 0.0001) and the fair group (P = 0.002) with no change in the poor group. Patients out of work more than 3 months before surgery tended to have poor results. Overall, 56% of patients were extremely satisfied with the result of their surgery. CONCLUSION: Posterolateral intertransverse fusion can be used to successfully manage chronic discogenic back pain. However, patient selection remains a challenge, and successful outcome appears to be limited in the subset of patients receiving worker's compensation and those chronically disabled. Prospective and randomized study with objective pain criteria, independent review, and patient-oriented outcome is recommended.

Adult↗
PubMed1996

A rabbit model for nonunion of lumbar intertransverse process spine arthrodesis.

STUDY DESIGN: A rabbit model for lumbar intertransverse process spine arthrodesis was utilized, with blind evaluation of the control and experimental animals. OBJECTIVES: To establish an animal model for motion-induced nonunion of lumbar intertransverse process spine arthrodesis and to determine if there was an early time period during which excessive motion at the arthrodesis site was deleterious to fusion. SUMMARY OF BACKGROUND DATA: Most previously reported animal models for nonunion of lumbar spine arthrodesis do not use intertransverse process fusion and do not allow variable control of the nonunion-inducing factor. METHODS: Forty-two adult New Zealand white rabbits underwent posterolateral intertransverse process spine arthrodesis with autogenous iliac crest graft. Rabbits in the experimental group (n = 23) underwent a lifting protocol to produce motion at the arthrodesis site; those in the control group (n = 12) remained undisturbed in their cages. Arthrodeses were assessed radiographically and manually to determine if fusion had occurred. RESULTS: Lifted rabbits exhibited a 13% fusion rate compared to a 50% fusion rate in controls. Rabbits lifted during only the first 2 postoperative weeks exhibited a fusion rate that was significantly less (P = 0.03) than that of controls. CONCLUSIONS: A small animal model for motion-induced nonunion of lumbar intertransverse process spine arthrodesis has been established. With respect to excessive motion as a promoter of nonunion in spine arthrodeses, the early postoperative time period appears critical.

Animals↗
PubMed1996

Noninvasive markers of bone metabolism in the rhesus monkey: normal effects of age and gender.

Measurement of bone turnover in conditions such as osteoporosis has been limited by the need for invasive iliac bone biopsy to reliably determine parameters of bone metabolism. Recent advances in the area of serum and urinary markers of bone metabolism have raised the possibility for noninvasive measurements; however, little nonhuman primate data exist for these parameters. The purpose of this experiment was to define the normal range and variability of several of the newer noninvasive bone markers which are currently under investigation in humans. The primary intent was to determine age and gender variability, as well as provide some normative data for future experiments in nonhuman primates. Twenty-four rhesus macaques were divided into equal groups of male and female according to the following age groupings: 3 years, 5-10 years, 15-20 years, and > 25 years. Urine was collected three times daily for a four-day period and measured for several markers of bone turnoverm including pyridinoline (PYD), deoxypyrodinoline (DPD), hydroxyproline, and creatinine. Bone mineral density measurements of the lumbar spine were performed at the beginning and end of the study period. Serum was also obtained at the time of bone densitometry for measurement of osteocalcin levels by radioimmunoassay. There were no significant differences in bone mineral density, urine PYD, or urine DPD based on gender. Bone density was lowest in the youngest animals, peaked in the 15-20-year group, but again decreased in the oldest animals. The osteocalcin, PYD, and DPD levels followed an inversely related pattern to bone density. The most important result was the relative age insensitivity of the ratio of PYD:DPD in monkeys up to age 20 years. Since bone density changes take months or years to become measurable and iliac biopsies are invasive, the PYD/DPD marker ratio may have important implications for rapid noninvasive measurement of the effects of potential treatments for osteoporosis in the non-human primate model.

Age Factors↗
PubMed1996

Differential effects and glucocorticoid potentiation of bone morphogenetic protein action during rat osteoblast differentiation in vitro.

Bone morphogenetic proteins (BMPs) induce cartilage and bone differentiation in vivo and promote osteoblast differentiation from calvarial and marrow stromal cell preparations. Functional differences between BMP-2, -4, and -6 are not well understood. Recent investigations find that these three closely related osteoinductive proteins may exert different effects in primary rat calvarial cell cultures, suggesting the possibility of unique functions in vivo. In this study, we use a fetal rat secondary calvarial cell culture system to examine the differential effects of BMP-2, -4, and -6 on early osteoblast differentiation. These cells do not spontaneously differentiate into osteoblasts, as do cells in primary calvarial cultures, but rather require exposure to a differentiation initiator such as glucocorticoid or BMP. We determined that BMP-6 is a 2- to 2.5-fold more potent inducer of osteoblast differentiation than BMP-2 or -4. BMP-6 induced the formation of more and larger bone nodules as well as increased osteocalcin secretion. The effects of all three of these BMPs were potentiated up to 10-fold by cotreatment or pretreatment with the glucocorticoid triamcinolone (Trm). The Trm effects were synergistic with those of BMP-2 or -4, suggesting that this glucocorticoid may increase the cell responsiveness to these BMPs. Finally, BMP-6 did not require either cotreatment or pretreatment with Trm to achieve greater amounts of osteoblast differentiation than seen with BMP-2 or BMP-4 treatment, suggesting that BMP-6 may act at an earlier stage of cell differentiation.

Animals↗
PubMed1996

Orientation of the lumbar facet joints: association with degenerative disc disease.

The orientation of the lumbar facet joints was studied with magnetic resonance imaging in 140 subjects to determine if there is an association between facet tropism and intervertebral disc disease or between the orientation of the facet joints and degenerative spondylolisthesis. The 140 subjects were divided into four groups: sixty-seven asymptomatic volunteers, forty-six of whom did not have a herniated disc on magnetic resonance scans (Group I) and twenty-one who did (Group II); forty-six symptomatic patients who had a herniated disc confirmed operatively (Group III); and twenty-seven patients who had degenerative spondylolisthesis at the interspace between the fourth and fifth lumbar vertebrae (Group IV). Axial scans were made at each lumbar level and digitized, and the facet joint angle was measured by two independent observers with use of image analysis software in a personal computer. The technique of measurement of the facet angles on magnetic resonance scans was validated with a subset of subjects who also had computed tomography scans made. Similar values were obtained with the two methods (r = 0.92; p = 0.00001). For the forty-six asymptomatic volunteers who did not have a herniated disc on the magnetic resonance scans (Group I), the median facet tropism was 5 to 6 degrees and was more than 10 degrees in 24 per cent (eleven) of the subjects. There was no association between increased facet tropism and disc degeneration. At the level of the fourth and fifth lumbar vertebrae, the median facet tropism was 10.3 degrees in the symptomatic patients who had a herniated disc at the same level and 5.4 degrees in the asymptomatic volunteers (Group I) (p = 0.05). The mean orientation of the lumbar facet angles relative to the coronal plane was more sagittal at all levels in the patients who had degenerative spondylolisthesis. The greatest difference was at the level of the fourth and fifth lumbar vertebrae (p = 0.000001). The mean facet angle was 41 degrees (95 per cent confidence interval, 37.6 to 44.6 degrees) in the asymptomatic volunteers and 60 degrees (95 per cent confidence interval, 52.7 to 67.1 degrees) in the patients who had degenerative spondylolisthesis. Furthermore, both the left and the right facet joints were more sagittally oriented in the patients who had degenerative spondylolisthesis. An individual in who both facet-joint angles at the level of the fourth and fifth lumbar vertebrae were more than 45 degrees relative to the coronal plane was twenty-five times more likely to have degenerative spondylolisthesis (95 per cent confidence interval, seven to ninety-eight times). The increase in facet angles at levels other than that of the spondylolisthesis suggests that increased facet angles represent variations in anatomy rather than a secondary result of spondylolisthesis.

Adult↗
PubMed1996

Morphology of the lumbar intertransverse process fusion mass in the rabbit model: a comparison between two bone graft materials--rhBMP-2 and autograft.

We used computed tomography and the rabbit model to seek an explanation for the biomechanical superiority of recombinant human bone morphogenetic protein-2 (rhBMP-2) as compared with autogenous iliac bone in lumbar intertransverse process fusions, i.e., the rhBMP-2 fusions demonstrated significantly higher strength and stiffness. The results show that the fusion masses using rhBMP-2 have higher volume, and higher minimum contact area of fusion mass attachment to the transverse process. For both bone graft materials there was a correlation between site of failure and the fusion mass quadrant that contained the minimum contact area of attachment to the transverse process. The ideal graft material would be one that produced strong, mature, early fusions that failed along their length at random positions, rather than failing with high frequency at the transverse process. The fusions using rhBMP-2 were nearer to the ideal than those using autograft: These were stronger, more mature, and only 6 of 9 rhBMP-2 failed in the quadrant that contained the minimum contact area of attachment to the transverse process, as opposed to 11 of 12 for autograft.

Animals↗