Human Peripheral Nerve-Derived Pluripotent Cells Can Be Stimulated by In Vitro Bone Morphogenetic Protein-2.

We have recently identified a population of cells within the peripheral nerves of adult rodent animals (mice and rats) that can respond to Bone Morphogenetic Protein-2 (BMP-2) exposure or physical injury to rapidly proliferate. More importantly, these cells exhibited embryonic differentiation potentials that could be induced into osteoblastic and endothelial cells in vitro. The current study examined human nerve specimens to compare and characterize the cells after BMP-2 stimulation. Fresh pieces of human nerve tissue were minced and treated with either BMP-2 (750 ng/mL) or a PBS vehicle for 12 h at 37 °C, before being digested in 0.2% collagenase and 0.05% trypsin-EDTA. Isolated cells were cultured in a restrictive stem cell medium. Significantly more cells were obtained from the nerve pieces with the BMP-2 treatment in comparison with the PBS vehicle controls. Cell colonies started to form at Day 3. Expressions of the four transcription factors, namely, Klf4, c-Myc, Sox2, and Oct4, were confirmed at both the transcriptional and translational levels. The cells can be maintained in the stem cell culture medium for at least 6 weeks without changing their morphology. When the cells were transferred to a fibroblast growth medium, dispersed spindle-shaped motile cells were noted and became fibroblast activated protein-α (FAP) positive with immunocytochemistry staining. The data suggest that human peripheral nerve tissue also contains a population of cells that can respond to BMP-2 and express Klf4, Sox2, cMyc, and Oct4-the four transcription factors driving cell pluripotency. These cells are able to differentiate into FAP-positive fibroblasts. In summary, in human peripheral nerves also reside a population of quiescent cells with pluripotency potential that may be the same cells as rodent nerve-derived adult stem (NEDAPS) cells. It is proposed that these cells are possibly at the core of a previously unknown natural mechanism for healing an injury.

Cervical fusion for treatment of degenerative conditions: development of appropriate use criteria.

BACKGROUND CONTEXT: High quality evidence is difficult to generate, leaving substantial knowledge gaps in the treatment of spinal conditions. Appropriate use criteria (AUC) are a means of determining appropriate recommendations when high quality evidence is lacking. PURPOSE: Define appropriate use criteria (AUC) of cervical fusion for treatment of degenerative conditions of the cervical spine. STUDY DESIGN/SETTING: Appropriate use criteria for cervical fusion were developed using the RAND/UCLA appropriateness methodology. Following development of clinical guidelines and scenario writing, a one-day workshop was held with a multidisciplinary group of 14 raters, all considered thought leaders in their respective fields, to determine final ratings for cervical fusion appropriateness for various clinical situations. OUTCOME MEASURES: Final rating for cervical fusion recommendation as either "Appropriate," "Uncertain" or "Rarely Appropriate" based on the median final rating among the raters. METHODS: Inclusion criteria for scenarios included patients aged 18 to 80 with degenerative conditions of the cervical spine. Key modifiers were defined and combined to develop a matrix of clinical scenarios. The median score among the raters was used to determine the final rating for each scenario. The final rating was compared between modifier levels. Spearman's rank correlation between each modifier and the final rating was determined. A multivariable ordinal regression model was fit to determine the adjusted odds of an "Appropriate" final rating while adjusting for radiographic diagnosis, number of levels and symptom type. Three decision trees were developed using decision tree classification models and variable importance for each tree was computed. RESULTS: Of the 263 scenarios, 47 (17.9 %) were rated as rarely appropriate, 66 (25%) as uncertain and 150 (57%) were rated as appropriate. Symptom type was the modifier most strongly correlated with the final rating (adjusted ρ2 = 0.58, p<.01). A multivariable ordinal regression adjusting for symptom type, diagnosis, and number of levels and showed high discriminative ability (C statistic = 0.90) and the adjusted odds ratio (aOR) of receiving a final rating of "Appropriate" was highest for myelopathy (aOR, 7.1) and radiculopathy (aOR, 4.8). Three decision tree models showed that symptom type and radiographic diagnosis had the highest variable importance. CONCLUSIONS: Appropriate use criteria for cervical fusion in the setting of cervical degenerative disorders were developed. Symptom type was most strongly correlated with final rating. Myelopathy or radiculopathy were most strongly associated with an "Appropriate" rating, while axial pain without stenosis was most associated with "Rarely Appropriate."

Effect of BMP-2 Adherent to Resorbable Sutures on Cartilage Repair: A Rat Model of Xyphoid Process.

Meniscal tears are often seen in orthopedic practice. The current strategy for meniscal repair has only had limited success with a relatively high incidence of re-operative rate. This study evaluates the therapeutic effects of Bone morphogenetic protein-2 (BMP-2) soaked sutures for cartilage repair, using a rat model of xyphoid healing. Vicryl-resorbable sutures were presoaked in BMP-2 solutions prior to animal experimentation. Rat xyphoid process (an avascular hyaline cartilage structure) was surgically ruptured followed by repair procedures with regular suture or with sutures that were pre-soaked in BMP-2 solutions. In vitro assessment indicated that presoaking the Vicryl-resorbable sutures with 10 µg/mL BMP-2 resulted in a sustained amount of the growth factor release up to 7 days. Histological analysis suggested that application of this BMP-2 soaked suture on the rat xyphoid process model significantly improved the avascular cartilage healing compared to non-soaked control sutures. In conclusion, data here confirm that the rat xyphoid process repair is a reproducible and inexpensive animal model for meniscus and other cartilage repair. More importantly, coating of BMP-2 on sutures appears a potential avenue to improve cartilage repair and regeneration. Further study is warranted to explore the molecular mechanisms of this strategy.

Prevention and management of osteoporosis and osteoporotic fractures in persons with a spinal cord injury or disorder: A systematic scoping review.

Objectives: The primary objective was to review the literature regarding methodologies to assess fracture risk, to prevent and treat osteoporosis and to manage osteoporotic fractures in SCI/D.Study Design: Scoping review.Settings/Participants: Human adult subjects with a SCI/D.Outcome measures: Strategies to identify persons with SCI/D at risk for osteoporotic fractures, nonpharmacological and pharmacological therapies for osteoporosis and management of appendicular fractures.Results: 226 articles were included in the scoping review. Risk of osteoporotic fractures in SCI is predicted by a combination of DXA-defined low BMD plus clinical and demographic characteristics. Screening for secondary causes of osteoporosis, in particular hyperparathyroidism, hyperthyroidism, vitamin D insufficiency and hypogonadism, should be considered. Current antiresorptive therapies for treatment of osteoporosis have limited efficacy. Use of surgery to treat fractures has increased and outcomes are good and comparable to conservative treatment in most cases. A common adverse event following fracture was delayed healing.Conclusions: Most of the research in this area is limited by small sample sizes, weak study designs, and significant variation in populations studied. Future research needs to address cohort definition and study design issues.

Biomechanical evaluation of CIBOR spine interbody fusion device.

BACKGROUND: The CIBOR PEEK spinal interbody fusion device is an anterior lumbar interbody fusion construct with a hollow center designed to accommodate an osteoinductive carbon foam insert to promote bony ingrowth to induce fusion where rigid stabilization is needed. METHODS: Three different sizes of the device were investigated. Part-I: implants were tested under axial compression and rotation using polyurethane foam blocks. Part-II: simulated 2-legged stance using cadaveric specimen using the L5-S1 lumbar spine segment. Part-III: a survey feedback form was used to investigate two orthopedic surgeons concern regarding the implant. RESULTS: In Part-I, the subsidence hysteresis under axial compression loading was found to be statistical significant difference between these three implant sizes. It was noted that the implants had migration as rotation applied, and the amount of subsidence was a factor of the axial compression loads applied. In Part-II, a minor subsidence and carbon foam debris were observed when compared to each implant size. Poor contact surface of the implant with the end plates of the L5 or S1 vertebrae from the anterior view under maximum loads was observed; however, the implant seemed to be stable. Each surgeon has their own subjective opinion about the CIBOR implant. DISCUSSION: Two out of the three different sizes of the device (medium and large sizes) provided appropriate rigid stabilization at the physiological loads. Neither orthopedic surgeon was 100% satisfied with overall performance of the implant, but felt potential improvement could be made. CLINICAL RELEVANCE: This study indicates an option for operative treatment of spine interbody fusion, as the CIBOR spine interbody fusion device has a hollow center. This hollow center is designed to accommodate a carbon foam insert to promote bony ingrowth. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1157-1168, 2017.

Differentiation of nerve-derived adult pluripotent stem cells into osteoblastic and endothelial cells.

BACKGROUND CONTEXT: Stem cell-involved tissue engineering has gained dramatic attention as a therapeutic strategy for tissue regeneration including bone repair. However, the currently available possibilities to use embryonic stem cells and induced pluripotent stem cells (iPCs) face potential ethical issues, as well as risks of malignant transformation and immune rejection. Recently identified peripheral nerve-derived adult pluripotent stem cells (NEDAPS) that quickly proliferate after exposure to bone morphogenetic protein-2 (BMP-2) or nerve trauma and exhibit many embryonic stem cell characteristics may provide an attractive source cells for a variety of regenerative therapies. PURPOSE: The study aimed to examine the differentiation potential of the NEDAPS cells into osteoblastic cells and endothelial cells. STUDY DESIGN/SETTING: An in vitro investigation was undertaken to induce mouse NEDAPS cells into the phenotypes of osteoblastic and endothelial cells. METHODS: NEDAPS cells were isolated from low-dose BMP-2-exposed mouse sciatic nerves by collagenase and trypsin extraction. The cells were cultured in a stem cell maintenance medium, and the expression of KLF4, Sox2, c-Myc, and Oct4 before differentiation was confirmed. The cells were then subcultured in a complete osteogenic cell induction medium or endothelial cell growth medium, respectively, at 37°C and 5%CO2 atmosphere. Histologic, morphologic, and molecular assessments were performed 7 days later. RESULTS: The cells propagated in complete osteogenic medium for 7 days showed strong staining for type I collagen and alkaline phosphatase, suggesting the structural and functional properties of the osteoblastic cells. Further, real-time polymerase chain reaction (RT-PCR) revealed a significant expression of the osteoblast markers osteocalcin, osteopontin, and type I collagen. Similarly, the cells in endothelial growth medium were successfully differentiated into cobblestone-shaped endothelial cells expressing vascular endothelial growth factor (VEGF) receptors Flk-1 and Flt-1 demonstrated by RT-PCR. CONCLUSIONS: NEDAPS cells are readily induced to osteoblastic and endothelial cells, suggesting therapeutic potential for bone repair and other regenerative therapies.

Ablation of the basivertebral nerve for treatment of back pain: a clinical study.

BACKGROUND CONTENT: Lumbar axial back pain arising from degenerative disc disease continues to be a challenging clinical problem whether treated with nonsurgical management, local injection, or motion segment stabilization and fusion. PURPOSE: The purpose of this study was to determine the efficacy of intraosseous basivertebral nerve (BVN) ablation for the treatment of chronic lumbar back pain in a clinical setting. STUDY DESIGN: Patients meeting predefined inclusion or exclusion criteria were enrolled in a study using radiofrequency energy to ablate the BVN within the vertebral bodies adjacent to the diagnosed level. Patients were evaluated at 6 weeks, and 3, 6, and 12 months postoperatively. PATIENT SAMPLE: Seventeen patients with chronic, greater than 6 months, low back pain unresponsive to at least 3 months of conservative care were enrolled. Sixteen patients were treated successfully following screening using magnetic resonance imaging finding of Modic type I or II changes and positive confirmatory discography to determine the affected levels. The treated population consisted of eight male and eight female patients; the mean age was 48 years (34-66 years). OUTCOME MEASURES: Self-reported outcome measures were collected prospectively at each follow-up interval. Measures included the Oswestry Disability Index (ODI), visual analogue scale score, and Medical Outcomes Trust 36-Item Short-Form Health Survey (SF-36). MATERIALS AND METHODS: This is an industry-sponsored study to evaluate the effectiveness of intraosseous nerves in the treatment of chronic back pain. Consented and enrolled patients underwent ablation of the BVN using radiofrequency energy (INTRACEPT System, Relievant Medsystems, Inc, Redwood City, CA, USA) guided in a transpedicular or extrapedicular approach. Preoperative planning determined targeted ablation zone and safety zones. RESULTS: Mean baseline ODI of the treated cohort was 52±13, decreasing to a mean of 23±21 at 3 months follow-up (p<.001). The statistically significant improvement in ODI observed at 3 months was maintained through the 12-month follow-up. The mean baseline visual analogue scale score decreased from 61±22 to 45±35 at 3 months follow-up (p<.05), and the mean baseline physical component summary increased from 34.5±6.5 to 41.7±12.4 at 3 months follow-up (p=.03). CONCLUSION: Ablation of the BVN for the treatment of chronic lumbar back pain significantly improves patients' self-reported outcome early in the follow-up period; the improvement persisted throughout the 1-year study period.

Quiescent pluripotent stem cells reside within murine peripheral nerves that can be stimulated to proliferate by recombinant human bone morphogenic protein 2 or by nerve trauma.

BACKGROUND: The clinical use of recombinant human bone morphogenic protein 2 (rhBMP-2, Infuse) has been associated with nerve-related complications including new-onset sciatica, and retrograde ejaculation. PURPOSE: To better understand the interaction of rhBMP-2 and peripheral nerves with the intent of making procedures safer. STUDY DESIGN/SETTING: Using a mouse model to examine the direct effect of diluted rhBMP-2 (Infuse) on murine sciatic nerves. METHODS: Animal studies were approved by the Institutional Animal Care and Use Committee. Balb/c mouse sciatic nerves were surgically exposed and 60 ng (in 10 µL) of rhBMP-2 was applied to the nerve. In separate experiments, the sciatic nerves were subjected to mechanical compression using forceps (and not exposed to rhBMP-2). The third group of mice received direct injection of the same amount of rhBMP-2, or sterile saline as a control, into the hamstring area of the posterior thigh without surgery. Mouse limbs with intact sciatic nerve were collected at 24, 48, or 72 hours after treatment for histology processing. A separate set of identically treated sciatic nerves were retrieved from mice at the same time points and cells were isolated by collagenase and trypsin digestion. The isolated cells were cultured in a stem cell medium containing 20% knockout serum and human leukemia inhibitory factor. Immunohistochemical or immunofluorescent cell stains against KLF4, Sox2, c-Myc, and Oct4 were performed on the mouse tissue sections and cell culture slides. In addition, real-time polymerase chain reaction (PCR) was performed to quantify the mRNA expression profiles of the stem cell marker genes in cultured cells. RESULTS: Profound morphological changes of the mouse sciatic nerves were noted after exposure to rhBMP-2, with a rapid and robust cell proliferation within the nerves followed by migration of these cells into surrounding tissue. Immunohistochemical stain revealed strong nuclear stains of KLF4, Sox2, Oct4, and c-Myc on the overwhelming majority of these proliferating cells in the nerve. Intramuscular injections of rhBMP-2 or willful physical compression of the nerves showed similar cell proliferation effects as the direct application of Infuse to the sciatic nerve. The cells in stem cell culture medium grew steadily without feeder cells and appeared fairly uniform. They were adherent to substrate and were motile. Double fluorescent staining on the cells indicated colocalizationof all pairs of the four stem cell markers in the cell nuclei. Real-time PCR confirmed the strong mRNA expressions of KLF4, Sox2, Oct4, and c-Myc in these isolated cells. CONCLUSION: Exposure to BMP-2 causes a marked proliferation of previously quiescent cells within peripheral nerves. These cells simultaneously express KLF4, Sox2, Oct4, and c-Myc, the transcription factors that confer embryonic pluripotency. Work described in the companion paper reveals some of the differentiation capacity of the cells and their likely clinical significance. In addition, the effects of direct exposure of nerves to rhBMP-2 as described here should clearly illuminate the mechanism of BMP-2-related nerve complications. We would suggest that the use of this agent in proximity to known neural structures should only be done with extreme caution.

Management of Pediatric Supracondylar Humerus Fractures With Vascular Injury.

The American Academy of Orthopaedic Surgeons has developed the Appropriate Use Criteria (AUC) document Management of Pediatric Supracondylar Humerus Fractures With Vascular Injury. Evidence-based information, in conjunction with the clinical expertise of physicians, was used to develop the criteria to improve patient care and obtain the best outcomes while considering the subtleties and distinctions necessary in making clinical decisions. The AUC clinical patient scenarios were derived from patient indications that generally accompany a pediatric supracondylar humerus fracture with vascular injury, as well as from current evidence-based clinical practice guidelines and supporting literature. The 6 patient scenarios and 18 treatments were developed by the Writing Panel, a group of clinicians who are specialists in this AUC topic. Next, the Review Panel, a separate group of volunteer physicians, independently reviewed these materials to ensure that they were representative of patient scenarios that clinicians are likely to encounter in daily practice. Finally, the multidisciplinary Voting Panel (made up of specialists and nonspecialists) rated the appropriateness of treatment of each patient scenario using a 9-point scale to designate a treatment as Appropriate (median rating, 7 to 9), May Be Appropriate (median rating, 4 to 6), or Rarely Appropriate (median rating, 1 to 3).

Gene therapy for spinal fusion using an insect vector.

COMMENTARY ON: Fu T-S, Chang Y-H, Wong C-B, Wang I-C, Tsai T-T, Lai P-L, et al. Mesenchymal stem cells expressingbaculovirus-engineered BMP-2 and VEGF enhance posterolateral spine fusion in a rabbit model. Spine J 2015;15(9):2036-44.

Management of Pediatric Supracondylar Humerus Fractures.

The American Academy of Orthopaedic Surgeons has developed Appropriate Use Criteria (AUC) on the Management of Pediatric Supracondylar Humerus Fractures (PSHF). Evidence-based information, in conjunction with the clinical expertise of physicians, was used to develop the criteria to improve patient care and obtain the best outcomes while considering the subtleties and distinctions necessary in making clinical decisions. The PSHF AUC clinical patient scenarios were derived from patient indications that generally accompany a PSHF as well as from current evidence-based clinical practice guidelines and supporting literature. The 220 patient scenarios and 14 treatments were developed by the Writing Panel, a group of clinicians who are specialists in this AUC topic. Next, the Review Panel, a separate group of volunteer physicians, independently reviewed these materials to ensure that they were representative of patient scenarios that clinicians are likely to encounter in daily practice. Finally, the multidisciplinary Voting Panel (made up of specialists and nonspecialists) rated the appropriateness of treatment of each patient scenario using a 9-point scale to designate a treatment as Appropriate (median rating, 7 to 9), May Be Appropriate (median rating, 4 to 6), or Rarely Appropriate (median rating, 1 to 3).

Effect of vertebroplasty on the compressive strength of vertebral bodies.

BACKGROUND CONTEXT: Percutaneous vertebroplasty has been used successfully for many years in the treatment of painful compressive vertebral fractures due to osteoporosis. PURPOSE: To compare the effect of vertebroplasty on the compressive strength of unfractured vertebral bodies. STUDY DESIGN: Biomechanical study on cadaveric thoracic vertebrae. METHODS: Forty vertebral bodies from four cadaveric thoracic spines were used for this experiment. Before testing, each thoracic spine was submitted to bone density testing and radiographic evaluation to rule out any obvious fractures. Under image intensification, 6 mL of a mixture of polymethylmethacrylate (PMMA) with barium (8 g of barium/40 g of PMMA) was injected into every other vertebral body of each spine specimen. After vertebroplasty, all soft tissues were dissected from the spine, and the vertebral bodies were separated and potted for mechanical testing. Testing to failure was performed using a combination of axial compression and anterior flexion moments. Two pneumatic cylinders applied anterior and posterior loads at a distance ratio of 4:3 relative to the anterior vertebral body wall, whereas two additional cylinders applied lateral loads, each at a constant rate of 200 N/s. RESULTS: The average failure loads for nonvertebroplasty specimens was 6724.02 ± 3291.70 N, whereas the specimens injected with PMMA failed at an average compressive force of 5770.50 ± 2133.72 N. No statistically significant difference in failure loads could be detected between intact specimens and those that had undergone vertebroplasty. CONCLUSIONS: Under these specific loading conditions, no significant increase in compressive strength of the vertebral bodies could be documented. This suggests that some caution should be applied to the concept of "prophylactic" vertebroplasty in patients at risk for fracture.

Histologic identification of brown adipose and peripheral nerve involvement in human atherosclerotic vessels.

The disease mechanisms and histology of plaque development associated with atherosclerosis remain incredibly complex and not entirely understood. Recent investigations have emphasized the importance of inflammation in atherosclerosis. Several studies have also indicated heterotopic or extraskeletal bone formation in atherosclerotic vessels. The mechanisms behind heterotopic ossification appear to have similarities to those underlying atherosclerosis, with inflammation being a key inductive component to heterotopic ossification. Therefore, in the present study, we evaluated the histology associated with pathologies of atherosclerosis and heterotopic ossification in 271 coronary vessel tissue samples. We examined the prevalence and features of the inflammatory response as well as new vessel and bone formation. Inflammation and neovascularization were observed both in the adventitia and within the atherosclerotic lesions of the vessels themselves. Intriguingly, neural changes, including collections of inflammatory cells and expression of neuroinflammatory factors, were detected in the adventitial nerves of the vessels. Mature lamellar bone was found in 18 coronary vessels (7%), often with hematopoietic elements and active bone remodeling. Brown adipocytes, which pattern heterotopic bone formation, were present within the atherosclerotic lesions (28%, or 75/271). As expected, there was a strong correlation between the presence of cholesterol and plaque formation (P < .0001), but there also seemed to be a trend toward a connection between the presence of brown adipocytes and plaque. From this histologic evaluation, along with cholesterol and dystrophic calcification, we noted a novel appearance of brown adipocytes as well as neural changes, which may provide new insights to further our understanding of atherosclerosis.

Prospective randomized phase II Trial of accelerated reepithelialization of superficial second-degree burn wounds using extracorporeal shock wave therapy.

BACKGROUND: As extracorporeal shock wave therapy (ESWT) can enhance healing of skin graft donor sites, this study focused on shock wave effects in burn wounds. METHODS: A predefined cohort of 50 patients (6 with incomplete data or lost to follow-up) with acute second-degree burns from a larger study of 100 patients were randomly assigned between December 2006 and December 2007 to receive standard therapy (burn wound debridement/topical antiseptic therapy) with (n = 22) or without (n = 22) defocused ESWT (100 impulses/cm at 0.1 mJ/mm) applied once to the study burn, after debridement. Randomization sequence was computer-generated, and patients were blinded to treatment allocation. The primary endpoint, time to complete burn wound epithelialization, was determined by independent, blinded-observer. A worst case scenario was applied to the missing cases to rule out the impact of withdrawal bias. RESULTS: Patient characteristics across the 2 study groups were balanced (P > 0.05) except for older age (53 ± 17 vs. 38 ± 13 years, P = 0.002) in the ESWT group. Mean time to complete (≥95%) epithelialization (CE) for patients that did and did not undergo ESWT was 9.6 ± 1.7 and 12.5 ± 2.2 days, respectively (P < 0.0005). When age (continuous variable) and treatment group (binary) were examined in a linear regression model to control the baseline age imbalance, time to CE, age was not significant (P = 0.33) and treatment group retained significance (P < 0.0005). Statistical significance (P = 0.001) was retained when ESWT cases with missing follow-up were assigned the longest time to CE and when controls with missing follow-up were assigned the shortest time to CE. CONCLUSIONS: In this randomized phase II study, application of a single defocused shock wave treatment to the superficial second-degree burn wound after debridement/topical antiseptic therapy significantly accelerated epithelialization. This finding warrants confirmation in a larger phase III trial (ClinicalTrials.gov identifier: NCT01242423).

Toward the establishment of optimal computed tomographic parameters for the assessment of lumbar spinal fusion.

BACKGROUND CONTEXT: The accurate detection of the extent of bony fusion after attempted lumbar arthrodesis is important given that subsequent efforts-such as decisions regarding need for continued external bracing, use of enhancing modalities (electrical stimulation and pulsed ultrasound), recommended activity levels, return to employment, early surgical intervention, and others-may be needed to reduce the risk of late failure, especially in light of the fact that late revisions for failed fusions often result in poor outcomes and significant costs. Thin-cut computed tomography (CT) has emerged as the study of choice for this purpose. PURPOSE: To delineate the optimal CT parameters for determining fusion versus pseudarthosis after attempted lumbar fusion. STUDY DESIGN: Blinded CT assessment with cadaveric specimen as a gold standard. METHODS: A human cadaveric spine specimen with a T10 to S1 thoracolumbar posterolateral fusion augmented by instrumentation and anterior lumbar interbody fusions was used as a gold standard. Two experienced spine surgeons and one musculoskeletal radiologist-all blinded to the pathology results-assessed a series of CT scans of the specimen, each CT using one of six predefined sets of parameters. RESULTS: Predictive values and sensitivity generally improved with decreasing slice thickness and slice spacing, but only modestly. All sets of parameters had higher negative predictive value (NPV) than positive predictive value (PPV). Computed tomographic parameters of 0.9-mm thick sections with 50% overlap showed the highest PPV and NPV, where NPV was 90, but PPV was only 59. CONCLUSIONS: In this study, using the best widely available CT technologies and the ideal gold standard, thin-cut CT remained less than ideal for the assessment of lumbar arthrodesis/pseudarthrosis. Tuning slice thickness and slice spacing down generally improves detail, but marginally. We have successfully defined "optimal" as "best available," but "optimal" as "nearly perfect" awaits further technological advances.

An injectable method for noninvasive spine fusion.

BACKGROUND CONTEXT: Bone morphogenetic proteins (BMPs) induce bone formation but are difficult to localize, and subsequent diffusion from the site of interest and short half-life reduce the efficacy of the protein. Currently, spine fusion requires stripping, decortications of the transverse processes, and an autograft harvest procedure. Even in combination with BMPs, clinical spinal fusion has a high failure rate, presumably because of difficulties in localizing sufficient levels of BMP. PURPOSE: The goal was to achieve reliable spine fusion through a single injection of a cell-based gene therapy system without the need for any surgical intervention. STUDY DESIGN: Eighty-seven immunodeficient (n=44) and immune-competent (n=43) mice were injected along the paraspinous musculature to achieve rapid induction of heterotopic ossification (HO) and ultimately spinal arthrodesis. METHODS: Immunodeficient and immune-competent mice were injected with fibroblasts, transduced with an adenoviral vector to express BMP2, along the paraspinous musculature. Bone formation was evaluated via radiographs, microcomputed tomography, and biomechanical analysis. RESULTS: ew bridging bone between the vertebrae and the fusion to adjacent skeletal bone was obtained as early as 2 weeks. Reduction in spine flexion-extension also occurred as early as 2 weeks after injection of the gene therapy system, with greater than 90% fusion by 4 weeks in all animals regardless of their genetic background. CONCLUSIONS: Injection of our cell-based system into the paraspinous musculature induces spinal fusion that is dependent neither on the cell type nor on the immune status. These studies are the first to harness HO in an immune-competent model as a noninvasive injectable system for clinically relevant spinal fusion and may one day impact human spinal arthrodesis.

Cell-based gene therapy for repair of critical size defects in the rat fibula.

More than a decade has passed since the first experiments using adenovirus-transduced cells expressing bone morphogenetic protein 2 were performed for the synthesis of bone. Since this time, the field of bone gene therapy has tackled many issues surrounding safety and efficacy of this type of strategy. We present studies examining the parameters of the timing of bone healing, and remodeling when heterotopic ossification (HO) is used for bone fracture repair using an adenovirus gene therapy approach. We use a rat fibula defect, which surprisingly does not heal even when a simple fracture is introduced. In this model, the bone quickly resorbs most likely due to the non-weight bearing nature of this bone in rodents. Using our gene therapy system robust HO can be introduced at the targeted location of the defect resulting in bone repair. The HO and resultant bone healing appeared to be dose dependent, based on the number of AdBMP2-transduced cells delivered. Interestingly, the HO undergoes substantial remodeling, and assumes the size and shape of the missing segment of bone. However, in some instances we observed some additional bone associated with the repair, signifying that perhaps the forces on the newly forming bone are inadequate to dictate shape. In all cases, the HO appeared to fuse into the adjacent long bone. The data collectively indicates that the use of BMP2 gene therapy strategies may vary depending on the location and nature of the defect. Therefore, additional parameters should be considered when implementing such strategies.