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Several P-wave azimuthal anisotropy studies have been conducted for the SEG Advanced Modeling Program Phase II Barrett model data. However, these analyses provide fracture property estimation that is inconsistent with the actual model properties. Therefore, we perform a feasibility study to understand the influence of the overburden and reservoir properties, and processing and inversion steps, which together determine the success of the fracture interpretation from seismic data. The 1D model properties (orthorhombic for overburden and reservoir) are first extracted from the actual Barrett model properties at two locations. Anisotropic prestack reflectivity modeling exposes the true orthorhombic response of the 1D medium in the form of common-offset and common-azimuth gathers. The true anisotropic response is obscured in the Barrett data (generated by finite-element modeling) due to the mild lateral velocity variations and orthorhombic anisotropy in the overburden. We then expose the reservoir anisotropic response using an isotropic overburden in the reflectivity modeling. This indicates that the P-wave velocity variation with azimuth (VVAZ) responses generated by the reservoir itself are weak, which leads to an unstable VVAZ inversion to estimate the interval normal moveout (NMO) velocity anisotropy. The reservoir thickness (125 m or 65 ms of two-way traveltime) or NMO velocity anisotropy (6%–7%) needs to be at least doubled to obtain a stable VVAZ inversion. Anisotropic geometric-spreading correction improves the amplitude variation with azimuth inversion results when reflectivity modeling models the orthorhombic overburden. The converted wave (C-wave) has a stronger VVAZ response compared to that of the P-wave. We suggest that the C-wave data could be useful to constrain fracture interpretation in the Barrett model. We conclude that the results of previous studies are due to the combination of the residual influence of overburden after processing and imaging and the weak anisotropy responses from the reservoir.

Enhanced hydrocarbon recovery is essential for continued economic development of unconventional reservoirs. We have focused on dynamic characterization of the Niobrara and Codell Formations in Wattenberg Field through the development and analysis of a full integrated reservoir model. We determine the effectiveness of the hydraulic fracturing and production with two seismic monitor surveys, surface microseismic, completion data, and production data. The two monitor surveys were recorded after stimulation and again after two years of production. Identification of reservoir deformation due to hydraulic fracturing and production improves reservoir models by mapping nonstimulated and nonproducing zones. Monitoring these time-variant changes improves the prediction capability of reservoir models, which in turn leads to improved well and stage placement. We quantify dynamic reservoir changes with time-lapse P-wave seismic data using prestack inversion and velocity-independent layer stripping for velocity and attenuation changes within the Niobrara and Codell reservoirs. A 3D geomechanical model and production data are history matched, and a simulation is run for two years of production. Results are integrated with time-lapse seismic data to illustrate the effects of hydraulic fracturing and production. Our analyses illustrate that chalk facies have significantly higher hydraulic fracture efficiency and production performance than marl facies. In addition, structural and hydraulic complexity associated with faults generate spatial variability in a well’s total production.

Case-control study.To identify risk factors for surgical site infections (SSIs) following vertical expandable prosthetic titanium rib (VEPTR) surgery in children.VEPTR surgery is a growth-sparing approach for early-onset scoliosis and chest or rib abnormalities. SSIs are an important complication following VEPTR surgery. We aimed to identify modifiable risk factors for SSIs following VEPTR surgery.Children who underwent VEPTR surgery at a tertiary-care children's hospital from January 2010 through November 2014 were included. SSIs following VEPTR implant or revision surgeries were identified. For each case patient, three control subjects matched by procedure type were randomly selected among those without infection. Patient and surgery-related risk factors were analyzed using conditional logistic regression.Twenty-six infections occurred in 22 subjects following 326 VEPTR surgeries (SSI rate: 8.0%). The infection rate was greater among implant than revision surgeries (15.5% vs. 4.5%; p.001). Methicillin-susceptible Staphylococcus aureus was the most common pathogen (50% of infections). On multivariate analysis, VEPTR SSI infections were associated with male gender (OR 3.5, 95% CI 0.9-13.2), assisted feeding (OR 4.5, 95% CI 1.0-20.3), administration of preoperative antibiotics more than 30 minutes before surgery (or60 minutes for vancomycin) (OR 6.9, 95% CI 1.2-39.0), and an intraoperative temperature less than 35.0°C (OR 4.3, 95% CI 0.8-23.7).Administration of preoperative antibiotics closer to the time of surgery may reduce the risk of SSI in children undergoing VEPTR surgery. Further study is needed to determine the optimal timing of antibiotic prophylaxis for children undergoing spinal surgery.Level III.

The impact of government on the Canadian urban system is explored using Revenue Canada data from personal income tax returns. Variations in taxes and in certain forms of government expenditure among urban places are linked with city size, economic base, per capita income, and rate of growth. It is found that many locations are heavily dependent on the public sector and that, overall, government programmes redistribute income toward smaller and less prosperous places. The most significant effect, however, is the stabilization of local economies by means of a large and relatively constant public sector. L'impact du gouvernement sur le systeme urbain canadien est etudie en utilisant des donnees de Revenu Canada qui proviennent des declarations d'impot sur le revenu des particuliers. Les variations de taxes et de certains types de depenses publiques parmi les regions urbaines sont associes avec les variables de taille urbaine, base economique, revenu per capita, et taux de croissance. Il est demontre que plusieurs regions sont fortement dependantes du secteur public et que, globalement, les programmes gouvernementaux redistribuent le revenue vers les regions les plus petites et les moins prosperes. Mais l'effet le plus significatif est celui de la stabilisation des economies locales par le biais d'un large et relativement constant secteur public.

[Introduction][1] Although surgical treatment of spondylothoracic dysplasia (STD) is controversial, we have found that an expansion thoracoplasty using a Vertical Expandable Prosthetic Titanium Rib (VEPTR; DePuy Synthes) results in favorable outcomes, including 100% survivability (at an average follow-up of 6.2 years), increased thoracic spinal length, and decreased requirements for ventilation support. [Step 1: Preoperative Preparation][2] Make anteroposterior and lateral radiographs of the spine. [Step 2: Position the Patient for the Procedure][3] The patient is placed in the prone position. [Step 3: The Incision][4] A curvilinear skin incision is made, starting proximally between the spine and the medial edge of the scapula. [Step 4: The Osteotomy][5] Perform the v-osteotomy. [Step 5: Placement of the VEPTR Device][6] A number-4 VEPTR-I device is wedged in, starting laterally within the osteotomy sites, wedging the osteotomies apart, distracting the superior ribs proximally and the inferior ribs distally, lengthening the hemithorax, and stopping approximately at the posterior axillary line, when there is maximum stress on the superior and inferior ribs, to avoid fracture, and the lamina spreaders are then removed. [Step 6: Wound Closure][7] Insert drains and local anesthetic catheters and close the wound. [Step 7: Expansion and Replacement Procedures][8] Lengthen the devices with the standard VEPTR technique of limited 3-cm incisions every three to six months. [Results][9] VEPTR treatment in patients with STD is associated with increased thoracic spine height and reduced thoracic width-to-height ratio, suggesting a greater gain in height than in width. [What to Watch For][10] [Indications][11] [Contraindications][12] [Pitfalls & Challenges][13] [Introduction][1] Although surgical treatment of spondylothoracic dysplasia (STD) is controversial, we have found that an expansion thoracoplasty using a Vertical Expandable Prosthetic Titanium Rib (VEPTR; DePuy Synthes) results in favorable outcomes, including 100% survivability (at an average follow-up of 6.2 years), increased thoracic spinal length, and decreased requirements for ventilation support. [Step 1: Preoperative Preparation][2] Make anteroposterior and lateral radiographs of the spine. [Step 2: Position the Patient for the Procedure][3] The patient is placed in the prone position. [Step 3: The Incision][4] A curvilinear skin incision is made, starting proximally between the spine and the medial edge of the scapula. [Step 4: The Osteotomy][5] Perform the v-osteotomy. [Step 5: Placement of the VEPTR Device][6] A number-4 VEPTR-I device is wedged in, starting laterally within the osteotomy sites, wedging the osteotomies apart, distracting the superior ribs proximally and the inferior ribs distally, lengthening the hemithorax, and stopping approximately at the posterior axillary line, when there is maximum stress on the superior and inferior ribs, to avoid fracture, and the lamina spreaders are then removed. [Step 6: Wound Closure][7] Insert drains and local anesthetic catheters and close the wound. [Step 7: Expansion and Replacement Procedures][8] Lengthen the devices with the standard VEPTR technique of limited 3-cm incisions every three to six months. [Results][9] VEPTR treatment in patients with STD is associated with increased thoracic spine height and reduced thoracic width-to-height ratio, suggesting a greater gain in height than in width. [What to Watch For][10] [Indications][11] [Contraindications][12] [Pitfalls & Challenges][13] [1]: #sec-12 [2]: #sec-13 [3]: #sec-14 [4]: #sec-15 [5]: #sec-16 [6]: #sec-17 [7]: #sec-18 [8]: #sec-19 [9]: #sec-20 [10]: #sec-21 [11]: #sec-22 [12]: #sec-23 [13]: #sec-24

BACKGROUND Jeune syndrome (JS) often results in lethal thoracic insufficiency syndrome. Since 1991, vertical expandable prosthetic titanium rib Dynamic PosteroLateral Expansion Thoracoplasty was used at our institution for treatment of JS. This study assesses the safety and efficacy of this procedure. METHODS Twenty-four JS patients were treated, 2 lost to follow-up, 17 with a minimum of 2-year follow-up retrospectively reviewed for clinical course: Assisted Ventilation Rate, respiratory rate, capillary blood gases, pulmonary function testings, and complications. Upright anteroposterior/lateral radiographs were measured for Cobb angle, kyphosis, lordosis, thoracic width, and thoracic/lumbar spinal height. Computed tomography scan lung volumes were obtained in 12 patients. RESULTS Mean age at initial implant was 23 months (7 to 62 mo) with an average 8.4 years (2.3 to 15.6 y) of follow-up. Average chest width increased from 121 to 168 mm at follow-up (P

The determination of how much disability should be assigned a patient has been a point of contention in many clinics and numerous court trials involving workmen's compensation and personal injury cases. The Cybex II* isokinetic system can produce objective data which, when used in a disability formula, can take the guesswork out of disability evaluation. It will also reduce legal and medical confusion regarding the determination.

Postoperative nutrition is best provided enterally; however, patients often develop intolerance to enteral feedings. Our aim was to prospectively identify abdominal examination and jejunal pressure activity associated with postoperative intolerance of enteral feedings. Twenty-nine patients underwent abdominal operation and needle catheter jejunostomy placement. Elemental tube feedings were started on the day after surgery and advanced to the caloric goal rate over three days. Patients whose feedings were slowed at the attending surgeon's discretion were defined as intolerant. Jejunal manometry and a standardized abdominal exam were performed on postoperative days 1, 3, and 5. Fifteen patients (52%) were intolerant of tube feedings and had decreased jejunal motor activity but more active bowel sounds prior to feedings. After feedings, intolerant patients developed abdominal distension, but other abdominal findings were inconsistent. A marked decrease in phase II of the migrating motility complex (MMC) and the lack of a fed response were present in both groups. The overall jejunal motility present on day 1 following surgery identifies patients that will not tolerate enteral feedings. The abdominal examination, MMC parameters, and motor response to feeding did not predict feeding intolerance.

Study Design. Early and long-term postoperative outcome were analyzed by retrospective record review and compared with results of intraoperative somatosensory evoked potential (SEP) findings in 70 patients with chronic lumbar stenosis. of Background Data. Adverse SEP changes occur in up to 2% of patients during scoliosis surgery and may reverse with intraoperative intervention. Little is known about the short- or long-term results of intraoperative intervention based on adverse SEP changes in patients with chronic lumbar stenosis during lumbar decompression and fusion. Objective. To compare intraoperative SEP changes with immediate and long-term neurologic outcome in patients undergoing lumbar decompression, instrumentation and fusion for chronic lumbar stenosis and to determine whether the early correlation between intraoperative SEP deterioration and clinical outcome persisted. Methods. Monitoring SEPs using an alternating arm and leg stimulation paradigm allowed rapid identification of intraoperative changes. Retrospective record review was conducted without knowledge of intraoperative SEP findings. Clinical and SEP findings were then compared. to determine whether the strong association between intraoperative SEP results and early clinical outcome persisted. Results. Nine of 12 patients who had unilateral intraoperative SEP deterioration that resolved with intervention had no adverse sequelae; the remaining three had new ipsilateral weakness that persisted during a 9-24-month follow-up. Intraoperative SEPs deteriorated in 15% of patients with normal and abnormal baseline SEPs. Intraoperative SEP deterioration could not be predicted by preoperative radicular pain, focal symptomatology or baseline SEP findings. 80% of patients with normal SEPs but only 54% with abnormal SEPs had immediate and sustained pain relief. SEP deterioration that reversed with surgical intervention or high-dose steroids resulted in no adverse neurologic outcome. Conclusions. Acute, unilaterai, unresolved intraoperative SEP deterioration was associated with long-term ipsilateral weakness not predicted by clinical or neurologic findings before surgery. Clinical improvement persisted in 92% of patients, 4% were unchanged, and 4% had persistent neurologic changes during an average 12-month follow-up period. The findings underscore the need for monitoring SEPs during surgery in all patients undergoing invasive lumbar surgery and for rapid identification and intervention should a unilateral SEP change persist.

We conducted a study at Stratton Field, a large gas-producing property in Kleberg and Nueces Counties in south Texas, to determine how to best integrate geophysics, geology, and reservoir engineering technologies to detect thin-bed compartmented reservoirs in a fluvially deposited reservoir system. This study documents that narrow, meandering, channel-fill reservoirs less than 20 ft (6 m) thick and as narrow as 200 ft (61 m) can be detected with 3-D seismic imaging at depths exceeding 6000 ft (1800 m) if the 3-D seismic data are carefully calibrated to subsurface stratigraphy using vertical seismic profile (VSP) control. Even though the 3-D seismic images show considerable stratigraphic detail in the interwell spaces and indicate where numerous thin-bed compartment boundaries could exist, the seismic images cannot by themselves specify which stratigraphic features are the flow barriers that create the reservoir compartmentalization. However, when well production histories, reservoir pressure histories, and pressure interference tests are incorporated into the 3-D seismic interpretation, a compartmentalized model of the reservoir system can be constructed that allows improved development drilling and reservoir management to be implemented. This study illustrates how realistic, thin-bed, compartmented reservoir models result when geologists, engineers, and geophysicists work together to develop a unified model of a stratigraphically complex reservoir system.

Latinos are the fastest growing ethnic population in the United States and type 2 diabetes is a major health burden in this population, but little effort has been made to study the prevalence of diabetic vertebral fragility in Latinos. We performed a cross-sectional study to determine vertebral fracture prevalence in a hospital-based population of South Texas residents (N = 296). We defined fractures in X-rays as a >20 % reduction in vertebral body height. Numerous variables were recorded, including age, body mass index, indicators of diabetes management and others. 71 % of the sample (N = 296) was Latino. The prevalence of vertebral fracture was increased in diabetic subjects relative to non-diabetic subjects (diabetic 27.9 %, non-diabetic 13.8 %) and, regardless of sex and diabetics status, decreased in Latinos relative to non-Latinos (Latino 16.7 %, non-Latino 26.4 %). These data suggest that vertebral fractures may be a growing concern for diabetic Latinos as well as diabetics of any racial/ethnic background.

Study design The study compared the presence of the high-intensity zone on magnetic resonance imaging with the results of awake discography. Objectives To see if there was a correlation between the results of awake discography and the presence of a high-intensity zone on magnetic resonance imaging. Summary of background data The evaluation of discogenic pain has proved to be somewhat elusive. Recent studies have indicated the high-intensity zone as being highly sensitive in the diagnosis of the painful discogenic segment. The present study was designed to investigate whether the presence of a high-intensity zone is associated with a concordant pain response on awake discography. Methods Magnetic resonance images were obtained in 29 patients with low back pain with and without radiculopathy. Consecutive patients were considered for surgical intervention after falling to respond to conservative treatment. The presence of a high-intensity zone was specifically looked for within the posterior anulus. Each patient subsequently underwent awake discography with computed tomography. Computed tomography was classified according to the Dallas Discogram Scale and the presence of a concordant pain response. Chi-square analysis was used to calculate the presence of a high-intensity zone versus disc disruption and the correlation of high-intensity zone and concordant pain response. Results There was no statistically significant correlation between the presence of a high-intensity zone and a concordant pain response at any level. The high-intensity zone was, however, never seen in a morphologically normal disc. Conclusions Although the high-intensity zone is present within the posterior anulus of some abnormal discs, it is not necessarily associated with a concordant pain response.

Roksandic’s discussion is superb! Because so few papers are submitted to Geophysics that deal with seismic interpretation theory, we were concerned that our philosophy of thin‐bed interpretation might not be appreciated by the readership. We encourage Roksandic, and other interpreters who have his ability to explain concepts, to continue to submit interpretation‐based papers to Geophysics.

Kyphoscoliosis is considered a relative contraindication to treatment with the Vertical Expandable Prosthetic Titanium Rib (VEPTR(®); Synthes Inc, Paoli, PA). Nevertheless, patients do present with early-onset kyphoscoliosis and thoracic insufficiency syndrome, and no suitable alternative treatments are currently available. However, it is unclear whether VEPTR(®) is reasonable for treating patients with kyphoscoliosis.We determined whether VEPTR(®) controls progression in patients with kyphoscoliosis and, if so, what methods might be used to improve control of deformity progression in these patients.We retrospectively reviewed 14 patients who had VEPTR(®) treatment of early-onset kyphoscoliosis. Degrees of kyphosis and scoliosis before, during, and after treatment were measured, and levels of instrumentation, thoracic dimensions, and complications were recorded. Minimum followup was 1.7 years (average, 5.8 years; range, 1.7-12.8 years).While scoliosis was stabilized, kyphosis increased a mean of 22° at last followup. Supple kyphosis became rigid during treatment. Proximal cradle cutout was a recurring problem. Distal anchors placed too proximally had inadequate lever arms to control kyphosis.Progression of kyphosis can be minimized during VEPTR(®) treatment by early extension of the construct to the second ribs bilaterally, distal extension of hybrid constructs to the pelvis, use of bilateral hybrid VEPTR(®) implants, and use of redesigned VEPTR(®) constructs that enhance fixation at the upper end. While our early results suggest these devices control progression of kyphosis, longer followup with more patients will be required to confirm the concept in these patients.

A prospective, randomized, double-blind study was performed to evaluate the clinical efficacy of intradiscal steroid injections. Criteria for entrance were one-level internal disc disruption or nonsequestered nuclear prolapse with or without sciatica and a positive pain response on awake discography. Exclusion criteria were multilevel disease, central or lateral stenosis, prior lumbar surgery, or medical disease requiring systemic steroids. A total of 25 patients were randomly assigned to Treatment Group A (methylprednisolone, Depo-Medrol 80 mg/ml, The Upjohn Co., Kalamazoo, Michigan) or Treatment Group B (bupivacaine, Marcaine .5% 1.5 ml, Sanofi Winthrop Pharmaceuticals, New York, New York). Fourteen patients received Depo-Medrol, with 21% showing subjective improvement and 79% no improvement; 0% were clinically worse. Eleven patients received intradiscal Marcaine, with 9% showing clinical improvement and 91% no improvement; 0% were clinically worse. To quantify clinical response, a pain diagram grid score, a visual analog scale, and the Oswestry Pain Questionnaire were used before injection and 10-14 days after injection. No statistically significant benefit was identified in the use of intradiscal steroids.

This study was undertaken to determine the correlation between awake discography findings and magnetic resonance imaging in the evaluation of symptomatic lumbar disc disease. The study included 164 consecutive patients who underwent evaluation with discography and magnetic resonance imaging for lumbar disc disease from August 1987 to September 1989. Chronic low-back pain, with or without radicular symptoms, was the presenting complaint in each case. Each patient had previously failed conservative treatment. The average age was 36 (range, 19-66 years). Magnetic resonance images were performed before discography in each case. Discography was performed with patients minimally sedated and under local anesthesia. A lateral approach was used. Magnetic resonance imaging and discography correlated in 90 cases (55%) and differed in 74 (45%). Considering disc levels, discography and magnetic resonance imaging correlated in 371 discs (80%). There were 172 normal discs and 199 abnormal discs. Of the abnormal discs, 151 (76%) reproduced symptoms. In 60 discs (13%), magnetic resonance images showed abnormal findings and the discogram normal findings. Discs levels classified as abnormal on magnetic resonance imaging demonstrated that 108 discs (37%) were asymptomatic. Magnetic resonance imaging showed normal findings and the discogram abnormal findings in 34 discs (7%), of which 21 (5%) recreated exact symptoms and 13 (2%) caused no pain. Magnetic resonance imaging is a static test and discography the only available dynamic test for disc evaluation. Awake discography is a diagnostic study that can determine which abnormal discs are symptomatic via the pain response.

Study design Prospective clinical trial of vertical expandable prosthetic titanium rib (VEPTR) surgery in patients with congenital thoracic scoliosis with thoracic insufficiency syndrome and cervical tilt. Objective Report efficacy and safety of VEPTR mid-thoracic opening wedge thoracostomy in treatment of cervical tilt and head/truncal decompensation in children with thoracic insufficiency syndrome associated with thoracic congenital scoliosis. Summary of background data Cervical tilt in children is a rare problem, usually associated with congenital cervical or cervical-thoracic scoliosis, and in progressive deformity, surgical fusion or hemi-vertebrectomy risks neurologic injury, loss of motion of the cervical spine, and unknown effect on pulmonary function. VEPTR patients with congenital scoliosis can have severe neck tilt with poor cosmesis, with the risk of neck pain in adulthood. VEPTR mid-thoracic opening wedge thoracostomy treats thoracic insufficiency syndrome, and paradoxically also appears to improve the neck alignment cosmesis. Materials methods Patients with fused ribs and congenital scoliosis, thoracic insufficiency syndrome, and cervical tilt were treated with VEPTR mid-thoracic thoracostomy. Complication rates, respiratory outcome, pulmonary function tests in older children, Cobb angles, head/truncal decompensation, T1 oblique take-off, space available for lung, height of the thoracic spine, and cervical tilt angle were measured. Results Fourteen patients with cervical tilt, fused ribs, progressive congenital scoliosis, and TIS were treated. The primary thoracic scoliosis and space available for lung improved, cervical tilt stabilized, and head and truncal decompensation improved. One child was weaned off a ventilator. Complications included device migration, infection, and transient brachial palsy. Conclusion Mid-thoracic VEPTR opening wedge thoracostomy can stabilize cervical tilt associated with thoracic congenital scoliosis and fused ribs and may be an alternative to cervicothoracic spine fusion or hemi-vertebrectomy in some young children.

The past four decades have witnessed the arrival of numerous interventional procedures for the treatment of sciatica and back pain. Some have failed to gain general acceptance and have simply faded away, and others continue to be used without evidence of efficacy. What is unique about chymopapain is that it has fallen out of favor despite convincing evidence of its utility and efficacy in the treatment of sciatica from lumbar disc protrusion. It has been shown to be superior to placebo in no less than three double-blind, randomized controlled trials (1,2), and to be cost-effective with low morbidity when compared with open surgery (3).

We studied 100 patients in whom symptomatic pseudarthrosis had been established at more than 9 months after lumbar spine fusion. All patients were treated with a pulsed electromagnetic field device worn consistently 2 hours a day for at least 90 days. Solid fusion was achieved in 67% of patients. Effectiveness was not statistically significantly different for patients with risk factors such as smoking, use of allograft, absence of fixation, or multilevel fusions. Treatment was equally effective for posterolateral fusions (66%) as with interbody fusions (69%). For patients with symptomatic pseudarthrosis after lumbar spine fusion, pulsed electromagnetic field stimulation is an effective nonoperative salvage approach to achieving fusion.

Hardage et al. (1994) conducted a study at Stratton Field with the purpose of detecting thin‐bed compartmented reservoirs in a fluvially deposited system (Oligocene Frio Formation), and rightly concluded that, in order to determine which seismically imaged stratigraphic changes are compartment boundaries, it is necessary to incorporate geologic and reservoir engineering data (particularly reservoir pressure data) into seismic interpretation. Their interpretation philosophy consisted of defining depositional stratal surfaces (I would rather say paleodepositional surfaces), and in analyzing seismic reflection amplitude behavior on such surfaces.

The overall aim of this study is to compare the effectiveness of cervical lateral mass plate (CLMP) fixation to that of cervical lateral mass rod (CLMR) fixation and transpedicular fixation in providing stability to the cervical spine. Twenty-one cervical spines will be tested intact and with instrumentation in varying degrees of instability including posterior instability, anterior/posterior instability, corpectomy, and reconstructed corpectomy. The biomechanical testing will be conducted on an MTS 858 Mini Bionix testing system with specially designed fixation methods for producing axial torsion, flexion/extension, and lateral bending. Data for each of the constructs in all conditions will consist of stiffness and energy absorption that can be compared across constructs and conditions.

This report describes the definition of an interactive 3D simulation of the spine using the system previously developed to simulate the upper and lower extremities. Up to three effective axes of motion are defined for each spinal segment based upon the generally accepted descriptions in the literature. The effects of these functional anatomy definitions upon ligament function and structural stiffness are hypothesized using simulated motion and segment positions. Structures, developed from the NLM Visible Male CT database are sufficient for analyses at a certain level of detail, but hypotheses relating facet joint form and function will require greater detail.

The purpose of the study is to investigate one of the factors that appear to be responsible for the high incidence of back pain and disability, inefficacious lumbar lordosis. It has been the observation of many back pain specialists that patients with back pain and disc problems have a decreased lumbar curvature; this has been presumed by some to be a result of muscle spasm, but by others as a cause of the primary malady. Six cadaver spinal segments were tested on a materials testing system (MTS) in varying degrees of lumbar curvature to see whether the curvature had an affect on stability with compression and rotation, the motions responsible for many back injuries. In all cases, increased lumbar lordosis correlated with increased stiffness, This correlation was at a maximum with respect to the spines tested, in the one with the least amount of osteopenia (estimated by radiographs and age of specimens). The results suggest that lumbar lordosis correlates with increased stiffness in cadaveric specimens. This study is ongoing and preliminary results suggest a larger sample size for the mechanical testing is needed for the study to be conclusive and statistically valid. Once that is achieved, the correlations and clinical significance can be determined.

Background: Jarcho-Levin syndrome represents a spectrum of clinical and radiographic irregularities including abnormal vertebral segmentation or formation defects, rib deformities, and short-trunk dwarfism. These abnormalities cause reduced thoracic capacity for lung development, resulting in thoracic insufficiency syndrome. In the present study, we reviewed outcome measures related to scoliotic curve correction, thoracic growth, and respiratory function following VEPTR treatment in patients with Jarcho-Levin syndrome. Methods: Twenty-nine patients with Jarcho-Levin syndrome, subclassified as spondylocostal dysostosis (SCD) or spondylothoracic dysplasia (STD), were treated with VEPTR expansion thoracoplasty and followed for at least two years since the initial implantation. Spinal and respiratory measures were collected prior to the initial VEPTR implantation, immediately after implantation, and at the most recent follow-up. Results: VEPTR treatment was associated with improved clinical respiratory function and with increases in thoracic height (by 50% in the SCD group and 42% in the STD group) and thoracic width (by 37% in the SCD group and 28% in the STD group). VEPTR treatment resulted in scoliosis curve correction (improvement in the Cobb angle of 41% [22°] in the SCD group and 26% [3.7°] in the STD group) and in improved thoracic symmetry in patients with SCD. Patients with SCD displayed increased lumbar lordosis, and both groups of patients developed increased thoracic kyphosis approaching normal. Conclusions: VEPTR treatment improved thoracic symmetry, controlled spinal deformity, and was associated with improved clinical respiratory function. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Multicomponent seismic data allow geologic sequences to be defined with both P-waves and S-waves. These two distinct types of body waves provide different options for defining stratigraphy and facies within stratigraphic intervals. Either wave (P or S) can propagate as fast and slow modes in

In order to assess the effectiveness of calcium sulphate (plaster of Paris; POP) as a substitute for autologous bone graft, we performed lumbar intervertebral fusion in mature sheep using POP and a variety of other graft materials, and reviewed the literature. The osteoconductivity of the POP grafts was compared to that of grafts carried out with autogenous iliac crest, frozen allogeneic bone, and ProOsteon 500 coralline bone. We also compared the osteogenicity of POP to admixtures of autogenous iliac crest bone with POP and coralline bone, and to an osteoinductive demineralized sheep bone preparation (DBM). The substrates were loaded into tubular titanium mesh, implanted into excavated disc spaces and recovered after a period of 4 months. Fusion mass segments tested in flexion and tension showed that POP was equal to autogenous bone and most other substrates. The POP fusions were significantly tougher than the DBM fusions, even though histomorphometry failed to reveal differences in the amount of trabecular bone. We conclude that POP can be used to achieve a biomechanically stable interbody lumbar vertebral fusion. In addition, our literature review indicated that POP can be used as a vehicle for local delivery of antibiotics in bone infections.

This review presents the history of chemonucleolysis, the techniques, indications, contraindications, and complications. Presenting an historical overview and comparison of success rates with surgical discectomy may provide a fresh understanding of the controversy surrounding chemonucleolysis and establish its efficacy in relation to more invasive treatments. A review of the literature from 1973 through 1998 for chemonucleolysis, open discectomy, and microdiscectomy provided published success rates for these procedures, and a mean rate with standard deviation was determined. In the experience and opinion of the authors, chemonucleolysis remains a viable alternative for patients who have exhausted all conservative means of treatment. Proper patient selection leads to success rates comparable to open discectomy and microdiscectomy.

Study Design. In adult female sheep, histologic and biomechanical criteria were used to determine whether the osteoconductive performance of plaster of paris would promote the incorporation of the tubular titanium mesh implants used for interbody vertebral fusions. Objectives. To compare the osteogenicity of plaster of paris with that of autogenous iliac crest bone and bone marrow 6 months after they were loaded into tubular titanium mesh cages and implanted as L3-L5 bridges after L4 corpectomies. Summary of Background Data. One of the aims of surgery for vertebral pathology is to stabilize the spine by interbody fusions. The morbidity associated with the use of iliac crest autograft bone for fusion grafts prompted trials using plaster of paris as an osteoconductive substrate. Methods. The total volume of bone that invested the L3-L5 mesh cages after 6 months was quantitated by computed tomography scans. All specimens subsequently were cut into fusion mass segments for biomechanical testing in flexion, extension, compression, and torsion, and then embedded in plastic for sectioning and histomorphometry to determine the trabecular bone volume within the titanium mesh. Results. In each experimental model, implants of plaster of paris were the osteoconductive equal of autogenous iliac crest bone/marrow preparations. The volumes of bone formed around and within the titanium mesh were identical, and the tissues were biomechanically indistinguishable. A partial mechanism was determined by modifying the system for midshaft femoral defects. Conclusions. In the sheep, a tubular titanium mesh packed with plaster of paris forms an osteoconductive conduit to achieve a biomechanically stable interbody lumbar vertebral fusion.

The O-acetylserine sulfhydrylase (OASS) reaction has been studied using a number of spectral probes including UV--visible, fluorescence, circular dichroism, and 31P NMR spectroscopy. The addition of L-cysteine, L-alanine, and glycine to OASS results in a shift in lambda max of 412 nm for the internal Schiff base to 418 nm resulting from the formation of the external Schiff base. The addition of L-serine or O-methyl-D,L-serine gives decreases of the absorbance of unliganded enzyme at 412 nm of about 50% and 20%, respectively, concomitant with an increase in the absorbance at 320 nm and a shift in the lambda max of the remaining visible absorbance to 418 nm. The spectral shifts observed in the presence of L-serine are suggestive of establishing an equilibrium between different forms of external Schiff base. The concentration dependence of the changes at 440 (L-cysteine) and 320 nm (L-serine) provides an estimate of the dissociation constant for the external aldimine. The pH dependence of the dissociation constant suggests the alpha-amine of the amino acid must be unprotonated for nucleophilic attack at C4' of PLP, and an enzyme side chain must be unprotonated to hydrogen-bond the thiol or hydroxyl side chain of the amino acid. When L-cysteine is the amino acid, the thiol side chain must be protonated to hydrogen-bond to the unprotonated enzyme side chain. The 31P NMR chemical shift is increased from 5.2 ppm for unliganded enzyme to 5.3 ppm in the presence of L-cysteine, signaling a tighter interaction at the 5'-phosphate upon formation of the external Schiff base.(ABSTRACT TRUNCATED AT 250 WORDS)

The pH dependence of kinetic parameters using natural and alternative reactants was determined in order to obtain information on the chemical mechanisms of the A and B isozymes of O-acetylserine sulfhydrylase (OASS) from Salmonella typhimurium. A general mechanism is proposed for OASS in which OAS binds with its alpha-amine unprotonated to carry out a nucleophilic attack on C4' of the protonated Schiff base and with the acetyl carbonyl hydrogen-bonded to a protonated enzyme group (or a water molecule), which aids in the beta-elimination of acetate. The enzyme lysine that was in Schiff base linkage with the active site pyridoxal 5'-phosphate deprotonates the alpha-carbon in the beta-elimination reaction, and a proton is likely released with the acetate product. Sulfide likely binds as HS- to undergo nucleophilic attack on the alpha-aminoacrylate intermediate, followed by protonation of the alpha-carbon by the enzyme lysine. In OASS-A, HS- is hydrogen-bonded to the enzyme group that assists in the beta-elimination of acetate, but this is not the case for OASS-B. The pH independent equilibrium constant for the first half-reaction of OASS-A is 1.6 x 10(-3), while the second half-reaction is practically irreversible.

The purpose of this clinical study was to evaluate the safety and effectiveness of using the.Simmons Plating System as an adjunct to posterior lumbar fusion. The System may be used to address a wide variety of indications which require spinal arthrodesis, including degenerative disk disease, pseudarthrosis, fractures, and unsuccessful spinal fusions. The System provides superior stability for maximum fusion augmentation without limiting surgical flexibility.

Colchicine, a drug used for centuries in the treatment of gout, has been reported to be effective for low-back pain due to disc disorders. A prospective, randomized, double-blind study evaluating the therapeutic effect of intravenous colchicine was conducted in a group of patients with low-back pain with symptoms originating less than 6 months previously. Each patient completed a questionnaire and a pain drawing. Laboratory studies including uric acid and sedimentation rate were performed, as was a detailed physical examination and lumbar thermography. All treatment parameters (including physical therapy, anti-inflammatory medications, and instructions) were constant except that each patient received either intravenous colchicine or intravenous saline. Results indicate a significant difference between the two groups, the intravenous colchicine group showing improvement in symptoms for a few hours or days over a 3-week course of treatment. However, the relief was often of short duration.

The objective of this research was to determine the efficacy and safety of an experimental instrumentation device designed for transpedicular spinal fixation by evaluating fusion rates and clinical pain and function scores; to determine complication rates associated with the device; and to compare the obtained data with that previously published in the literature. Four hundred forty-two consecutive patients were enrolled in this 4-year, Food and Drug Administration-monitored investigational device exemption trial to undergo surgery for implantation of the device. Eighteen surgeons at 11 nationwide medical centers performed the operations and subsequent evaluations. The study population was derived from three diagnostic categories: degenerative disc disease, multioperated back, and vertebral fracture. The data source consisted of radiographs, clinical examination, and structured forms and questionnaires. Patients were evaluated preoperatively, intraoperatively, and postoperatively at 3, 6, 12, and 24 months. By the 24-month postoperative interval, attrition had reduced the study population to 342 patients, among whom bony fusion was obtained in 91.5%. Pain scores demonstrated a statistically significant improvement in clinical outcome. Intraoperative complications occurred in 21.9% of patients. Of the 442 study patients, 2.9% experienced device-related complications. Moreover, a total of 2,304 screws and bolts were implanted in this patient population. Of these, 0.39% were reported to have fractured. Among the 342 study patients observed during 24 months, the breakage rate of device components (bolt or screw) was 2.63%. These data compare favorably to existing reports of spinal arthrodesis effected with other types of instrumentation and without device implantation. In a 4-year trial, the experimental transpedicular fixation instrumentation produced successful spinal fusion in the majority of our study population, with acceptable complication rates.

The mechanism mediating the chronic pain associated with lumbar disc degeneration may involve neurotransmitters elaborated by dorsal root ganglion (DRG). This hypothesis has been tested in an applicable rabbit model of disc degeneration. Twenty control male rabbits underwent a soft-tissue release; 20 experimental rabbits sustained a facetectomy and capsulotomy and received an acute torsional lumbar injury. The levels of calcitonin gene-related peptide, vasoactive intestinal peptide, and substance P were measured in the DRG, spinal cord, and disc at 10, 30, 60, and 90 days postoperatively. Torsional injury was associated with a statistically significant increase in most DRG and spinal cord neurotransmitter values after 60-90 days. These points in time marked the periods of maximum biomechanical instability and disc narrowing. Such data support concepts about the association between chronic lumbar spinal instability, disc degeneration, and pain.

Torsional injuries may be a precursor to intervertebral disc degeneration, but published rabbit models indicate a latent time of 6 months. We describe a rabbit model in which instability and disc degeneration appear within 3 months. Sixty-five male New Zealand rabbits underwent presurgical irradiation to inhibit heterotopic bone formation. Control animals then underwent either a soft-tissue release or facetectomy and capsulotomy, whereas experimental animals received surgery and an acute 30 degrees torsional lumbar injury. Capsulotomy, as well as facetectomy without torsion, failed to effect disc degeneration. However, the rabbits that received torsion exhibited clear indications of degenerative disc changes (thinning, increased PLA2 levels, and decreased nucleus pulposus volume) within 60-90 days. The observations associate disc degeneration with a destabilizing acute torsional injury.

Thirty single-pedicle and triangulated pedicle screws were subjected to pull-out tests until complete dislodgment was achieved. Peak load, displacement curves, angle of triangulation, and equivalent mineral density were recorded. Dual pedicle screw triangulation produced a 154.4% increase in peak pull-out strength compared with that of the single pedicle screw. Salvage triangulation (replacing failed screws with a triangulation construct) produced a 127.4% increase in peak strength over that of the single screw. Positive correlation was found between individual screw peak strength, bone mineral density, and displacement at peak load. Primary and salvage triangulation produced higher resistance to pull-out than a single pedicle screw, which reflects the potential, beneficial effect of using this technique. Triangulation, therefore, can be used as primary (prophylactic) technique to enhance pedicular screw pull-out during forceful vertebral manipulation.

The migration flow patterns that we observe include processes that take place at various spatial and temporal scales. One means of temporal disaggregation is to compare flow patterns over successive 5-year periods. Such an analysis of the Canadian urban system reveals a continuing size/distance/cultural pattern a short-term economic growth pattern and a distinct shift in migrant preference away from larger centers and toward smaller places. It is not clear whether this latter shift is simply a short-term perturbation or marks a significant alteration in a long-term trend. (EXCERPT)

The use of colchicine for the treatment of low-back pain has been controversial; however, recent studies have shown its effectiveness when used intravenously. Studies using oral colchicine alone are lacking. The purpose of this study is to evaluate in a prospective, double-blind fashion the use of oral colchicine in the treatment of low back pain. Group I patients (15) were treated with a placebo capsule, and Group II (12) patients were treated with a colchicine capsule prescribed in a "burst dose" regimen. Patients were evaluated at 1, 2, 4, 6, and 12 weeks with a mean followup of 12 weeks. Parameters studied included patient characteristics, compliance, the McCoy pain drawings, pain analogue scales, the Million scale and objective tests. In terms of therapeutic response, the study shows no statistically significant difference between oral colchicine and placebo. The colchicine group did have an increased number of side effects.