Definition of Normal Vertebral Morphometry Using NHANES-II Radiographs.

A robust definition of normal vertebral morphometry is required to confidently identify abnormalities such as fractures. The Second National Health and Nutrition Examination Survey (NHANES-II) collected a nationwide probability sample to document the health status of the United States. Over 10,000 lateral cervical spine and 7,000 lateral lumbar spine X-rays were collected. Demographic, anthropometric, health, and medical history data were also collected. The coordinates of the vertebral body corners were obtained for each lumbar and cervical vertebra using previously validated, automated technology consisting of a pipeline of neural networks and coded logic. These landmarks were used to calculate six vertebral body morphometry metrics. Descriptive statistics were generated and used to identify and trim outliers from the data. Descriptive statistics were tabulated using the trimmed data for use in quantifying deviation from average for each metric. The dependency of these metrics on sex, age, race, nation of origin, height, weight, and body mass index (BMI) was also assessed. There was low variation in vertebral morphometry after accounting for vertebrae (eg, L1, L2), and the R 2 was high for ANOVAs. Excluding outliers, age, sex, race, nation of origin, height, weight, and BMI were statistically significant for most of the variables, though the F-statistic was very small compared to that for vertebral level. Excluding all variables except vertebra changed the ANOVA R 2 very little. Reference data were generated that could be used to produce standardized metrics in units of SD from mean. This allows for easy identification of abnormalities resulting from vertebral fractures, atypical vertebral body morphometries, and other congenital or degenerative conditions. Standardized metrics also remove the effect of vertebral level, facilitating easy interpretation and enabling data for all vertebrae to be pooled in research studies. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Analysis of translation and angular motion in loaded and unloaded positions in the lumbar spine.

BACKGROUND CONTEXT: Abnormalities in intervertebral rotation and translation are important to diagnosis and treatment planning for common spinal disorders. Tests that do not sufficiently load the spine can result in mis-diagnosed motion abnormalities. Upright flexion and extension x-rays are commonly used despite known limitations. Additional evidence is needed in support of preliminary studies suggesting that the change from standing to supine may sufficiently stress the spine to diagnose motion abnormalities. PURPOSE: Compare intervertebral translation between flexion and extension to translation between upright and supine positions in a representative clinical population. STUDY DESIGN/SETTING: Prospective analysis of images retrospectively collected from routine clinical practices. METHODS: After obtaining IRB approval for analysis of previously obtained images, patients were identified via chart reviews where a neutral-lateral x-ray and an MRI or CT exam were obtained for diagnosis of a spinal disorder and where flexion-extension x-rays had been obtained to help diagnose abnormal intervertebral motion. The mid-sagittal slice from the MRI or CT exam was paired with the neutral-lateral radiograph. Intervertebral translation at the L4-L5 and L5-S1 levels between supine and standing and between flexion and extension were measured from the images using previously validated methods. The translations were classified as normal or abnormal with reference to a previously obtained database of intervertebral motion in radiographically normal and asymptomatic volunteers. RESULTS: At the L5-S1 level in particular, there tended to be greater translation between the supine and standing than between upright flexion and extension. On average, translations were below that found in asymptomatic volunteers. No abnormal translations were detected from flexion-extension radiographs whereas approximately 7% of levels had abnormal translations between supine and upright positions. CONCLUSIONS: Intervertebral translations between supine and standing, measured using the mid-sagittal slice from a MRI or CT exam and a lateral x-ray with the patient standing can help to identify abnormal motion. This would be particularly valuable for patients with limited flexion and extension. This study thereby adds to the evidence in support of measuring intervertebral motion between the supine and upright positions to detect abnormal intervertebral motion.

The Assessment of Fusion Following Sacroiliac Joint Fusion Surgery.

Sacroiliac joint fusions (SIJF) have been the subject of many research studies. The technical success of an SIJF is in part determined by whether osseous bridging occurs across the sacroiliac joint (SIJ). However, no validated SIJF assessment method has been described. Our objective was to document previously described SIJF assessment methods and define and validate a detailed assessment system for SIJF. Our results are only intended to establish computed tomography (CT)-based guidelines for SIJF to be used in a subsequent large clinical study to correlate them with clinical outcomes. The SIJF literature was reviewed to document previous descriptions of SIJF assessments. A detailed system was then developed for assessing SIJF from CT exams. To provide data that can be used to address a range of research questions, the system included assessing bridging bone relative to the SIJ anatomy, bridging bone immediately adjacent to the threaded implants crossing the joint, as well as bridging bone close to but not immediately adjacent to the implants. The system was applied to assessing SIJF from thin-slice CT exams in 19 patients 12 months following surgery. Two experienced radiologists implemented the assessment system, and in the event of a disagreement, an adjudicator was used. Most prior studies provide very little detail about how SIJF was assessed. Using the new assessment system, the agreement between the primary readers was substantial (0.67 using Gwet's AC1 statistic). Bridging bone representing a fusion of the SIJ was identified in most patients both immediately adjacent to the threaded implants crossing the joint, as well as distant to the implants. A detailed radiographic assessment system proved to be applicable to SIJF. The assessment system includes explicit language describing the location and extent of bridging bone across the SIJ. Standardization of the assessment of the SIJFs may allow for a more meaningful comparison of data between studies.

Threshold Limit Graphical Approach to Understanding Outcome Predictive Metrics: Data from the Osteoarthritis Initiative.

Scatter plots, bar charts, linear regressions, analysis of variance, and other graphics and tests are frequently used to document associations between an independent variable and an outcome. However, these methods are also frequently limited when understanding how to use an independent variable in subsequent research or patient management. A novel graphical approach to visualizing data-the threshold limit graph-was therefore developed. Publically available data from the Osteoarthritis Initiative was used to illustrate the graphical approach to understanding the association between the change in joint space width (ΔJSW, independent variable) over four years, and knee symptoms at four years (using the Knee Injury and Osteoarthritis Outcome Score [KOOS], dependent variable). Using data for 4,202 knees, the traditional scatter plot and linear regression approach showed a significant but weak linear relationship between the symptom subscore of the KOOS and ΔJSW. However, the threshold level of ΔJSW that affects symptoms was not clear from the data. The same dataset was then plotted using the threshold limit graphical approach, which revealed a non-linear relationship between the variables. In contrast to the scatter plot, plotting the average KOOS symptom subscore for subgroups of the data, with each subgroup defined using sequentially increasing or decreasing ΔJSW thresholds revealed that symptoms got worse with joint space loss, but only when there was a significant amount of ΔJSW. A threshold limit analysis was repeated using small, randomly selected subsets of the data (N = ~100) to demonstrate the utility of the technique for identifying trends in smaller datasets. The threshold limit graph is a simple, graphical approach that may prove helpful in understanding how an independent variable might be used to predict outcomes. This approach provides an additional option for visualizing and quantifying associations between variables.

Development of a novel radiographic measure of lumbar instability and validation using the facet fluid sign.

BACKGROUND: Lumbar spinal instability is frequently referenced in clinical practice and the scientific literature despite the lack of a standard definition or validated radiographic test. The Quantitative Stability Index (QSI) is being developed as a novel objective test for sagittal plane lumbar instability. The QSI is calculated using lumbar flexion-extension radiographs. The goal of the current study was to use the facet fluid sign on MRI as the "gold standard" and determine if the QSI is significantly different in the presence of the fluid sign. METHODS: Sixty-two paired preoperative MRI and flexion-extension exams were obtained from a large FDA IDE study. The MRI exams were assessed for the presence of a facet fluid sign, and the QSI was calculated from sagittal plane intervertebral rotation and translation measurements. The QSI is based on the translation per degree of rotation (TPDR) and is calculated as a Z-score. A QSI > 2 indicates that the TPDR is > 2 std dev above the mean for an asymptomatic and radiographically normal population. The reproducibility of the QSI was also tested. RESULTS: The mean difference between trained observers in the measured QSI was between -0.28 and 0.36. The average QSI was significantly (P = 0.047, one-way analysis of variance) higher at levels with a definite fluid sign (2.3±3.2 versus 0.60±2.4). CONCLUSIONS: Although imperfect, the facet fluid sign observed may be the best currently available test for lumbar spine instability. Using the facet fluid sign as the "gold standard" the current study documents that the QSI can be expected to be significantly higher in the presence of the facet fluid sign. This supports that QSI might be used to test for sagittal plane lumbar instability. CLINICAL RELEVANCE: A validated, objective and practical test for spinal instability would facilitate research to understand the importance of instability in diagnosis and treatment of low-back related disorders.

Treatment Planning and Fracture Prediction in Patients with Skeletal Metastasis with CT-Based Rigidity Analysis.

PURPOSE: Pathologic fractures could be prevented if reliable methods of fracture risk assessment were available. A multicenter prospective study was conducted to identify significant predictors of physicians' treatment plan for skeletal metastasis based on clinical fracture risk assessments and the proposed CT-based Rigidity Analysis (CTRA). EXPERIMENTAL DESIGN: Orthopedic oncologists selected a treatment plan for 124 patients with 149 metastatic lesions based on the Mirels method. Then, CTRA was performed, and the results were provided to the physicians, who were asked to reassess their treatment plan. The pre- and post-CTRA treatment plans were compared to identify cases in which the treatment plan was changed based on the CTRA report. Patients were followed for a 4-month period to establish the incidence of pathologic fractures. RESULTS: Pain, lesion type, and lesion size were significant predictors of the pre-CTRA plan. After providing the CTRA results, physicians changed their plan for 36 patients. CTRA results, pain, and primary source of metastasis were significant predictors of the post-CTRA plan. Follow-up of patients who did not undergo fixation resulted in 7 fractures; CTRA predicted these fractures with 100% sensitivity and 90% specificity, whereas the Mirels method was 71% sensitive and 50% specific. CONCLUSIONS: Lesion type and size and pain level influenced the physicians' plans for the management of metastatic lesions. Physicians' treatment plans and fracture risk predictions were significantly influenced by the availability of CTRA results. Due to its high sensitivity and specificity, CTRA could potentially be used as a screening method for pathologic fractures.

Efficacy of MRI for assessment of spinal trauma: correlation with intraoperative findings.

STUDY DESIGN: Observational diagnostic study on consecutive patients. OBJECTIVE: To assess the efficacy of magnetic resonance imaging (MRI) for detecting spinal soft tissue injury after acute trauma using intraoperative findings as a reference standard. SUMMARY OF BACKGROUND DATA: Recognizing injuries to spinal soft tissue structures is critical for proper decision making and management for blunt trauma victims. Although MRI is considered the gold standard for imaging of soft tissues, its ability to identify specific components of soft tissue damage in acute spine trauma patients is poorly documented and controversial. METHODS: Intraoperative findings were recorded for 21 acute spinal trauma patients (study group) and 14 nontraumatic spinal surgery patients (control group). Preoperative MRI's were evaluated randomly and blindly by 2 neuroradiologists. MRI and intraoperative findings were compared. By using the intraoperative findings as the reference standard, sensitivity, specificity, positive and negative predictive values of MRI in detecting spinal soft tissue injury were determined. RESULTS: MRI was 100% sensitive and specific in detecting injury to the anterior longitudinal ligament. MRI was moderately sensitive (80%) but highly specific (100%) for injury to the posterior longitudinal ligament. In contrast, MRI was highly sensitive but less specific in detecting injury to paraspinal muscles (100%, 77%), intervertebral disk (100%, 71%), and interspinous ligament (100%, 64%). MRI was moderately sensitive and specific in detecting ligamentum flavum injury (80% and 86.7%) but poorly sensitive for facet capsule injury (62.5%). CONCLUSIONS: MRI demonstrated high sensitivity for spinal soft tissue injuries. However, MRI showed a definite trend to overestimate interspinous ligament, intervertebral disk, and paraspinal muscle injuries. On the basis of these results, we would consider MRI to be a useful tool for spine clearance after trauma. Conversely, caution should be applied when using MRI for operative decision making due to its less predictable specificity.

Endplate changes following discectomy: natural history and associations between imaging and clinical data.

PURPOSE: Some patients will experience post-operative back pain following lumbar discectomy, and the potential sources for that pain are poorly understood. One potential source is the vertebral endplates. The goal of this study was to document the changes that occur in lumbar endplates following discectomies, and to assess associations between endplate changes and clinical outcomes. METHODS: Changes in lumbar endplates and discs were assessed from X-rays, CT and MRI exams by comparing preoperative imaging with imaging obtained at yearly intervals up to 5 years. 260 endplates in 137 patients with single-level herniation and discectomy were analyzed. The geometry of osseous defects in the endplates was measured from the CT exams, and marrow and disc changes adjacent to endplates were assessed from the MRI exams. Clinical outcome assessments were collected at each time point. Descriptive statistics were used to describe endplate defect sizes, and logistic regression and analysis of variance were used to identify potential associations between endplate and vertebral body changes and clinical outcomes. RESULTS: Approximately 14 % of the endplates had osseous defects prior to surgery. After surgery, 24 % of inferior and 43 % of superior endplates had defects. Change occurred within the first year and remained relatively constant over the next few years. Disc signal intensity worsened and disc height decreased following surgery. New Modic changes were also observed. None of these changes were associated with having achieved a clinically significant improvement in outcome scores. The follow-up rates were low at the later time points and significant associations cannot be ruled out. CONCLUSIONS: This study documents lesion characteristics in detail and supports that osseous defects in the endplates at the level of a lumbar discectomy may be a relatively common finding following surgery, along with disc height loss, loss of disc signal intensity, and Modic changes. The clinical significance of these imaging findings could not be conclusively determined in this study.

Development of a computer-assisted forensic radiographic identification method using the lateral cervical and lumbar spine.

Medical examiners and coroners (ME/C) in the United States hold statutory responsibility to identify deceased individuals who fall under their jurisdiction. The computer-assisted decedent identification (CADI) project was designed to modify software used in diagnosis and treatment of spinal injuries into a mathematically validated tool for ME/C identification of fleshed decedents. CADI software analyzes the shapes of targeted vertebral bodies imaged in an array of standard radiographs and quantifies the likelihood that any two of the radiographs contain matching vertebral bodies. Six validation tests measured the repeatability, reliability, and sensitivity of the method, and the effects of age, sex, and number of radiographs in array composition. CADI returned a 92-100% success rate in identifying the true matching pair of vertebrae within arrays of five to 30 radiographs. Further development of CADI is expected to produce a novel identification method for use in ME/C offices that is reliable, timely, and cost-effective.

Optimizing success with lumbar disc arthroplasty.

PURPOSE: This study aimed at determining the variables that may prove useful in predicting clinical outcomes following lumbar disc arthroplasty. METHODS: Pre- and post-operative imaging assessments were obtained for 99 single-level lumbar disc arthroplasty patients from a prospective IDE study. The assessments and patient demographics were tested to identify variables that were significantly associated with clinical outcomes. RESULTS: Clinical outcome data were available for 85 % of patients at the 5-year follow-up. Numerous assessments made from the pre-operative imaging were found to have statistically significant associations with clinical outcomes at 2 and 5 years. The most notable factors were related to the amount of degeneration at the index level, with patients achieving better outcome scores at 5 years if they have higher grades of degeneration preoperatively. CONCLUSIONS: Several variables may prove effective at optimizing clinical outcomes including a preoperative disc height <8 mm, Modic type 2 changes adjacent to the target disc, a low amount of lordosis present at the treatment level, low levels of fatty replacement of the paraspinal musculature, a prominent amount of facet joint or disc degeneration, and the presence of flat or convex vertebral endplates. There were also post-operative findings associated with better patient outcomes including a larger percent of the endplate covered with the implant, larger implant heights, greater increases in disc space heights, and a larger increase in index level lumbar lordosis. These variables could be explored in other clinical studies to facilitate meta-analyses that could identify effective strategies to optimize clinical outcomes with lumbar disc arthroplasty.

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.

C1 lateral mass screw placement via the posterior arch: a technique comparison and anatomic analysis.

BACKGROUND CONTEXT: Instrumentation of C1 is becoming increasingly common. Starting points initially described for C1 lateral mass screws at the lateral mass/posterior arch junction are technically challenging. Recently, a number of techniques have evolved advocating varying starting points and trajectories. Despite being technically easier, there are new safety concerns. Insufficient evidence exists for optimal C1 lateral mass screw placement with starting points in the posterior arch. PURPOSE: To determine anatomic variability of the C1 lateral mass and posterior ring and to compare safety and feasibility of C1 lateral mass screw placement techniques via the posterior arch. STUDY DESIGN: Descriptive anatomy for surgical technique. METHODS: One hundred thin-cut cervical spine computed tomography scans were acquired and formatted for virtual surgery. Four different described techniques were used for virtual placement of C1 lateral mass screws. Success was defined as avoidance of critical structures including the transverse foramen, vertebral groove, and spinal dura. Anatomic variability of the C1 vertebra and safe zones for screw placement were also clarified. RESULTS: Overall screw placement success for the four techniques was 50% (Resnick), 92% (Tan et al.), 58% (Ma et al.), and 85% (Christensen et al.). Average posterior arch height was 6.7±2.1 mm, and vertebral groove height 4.9±1.1 mm was the most limiting dimension to safe screw placement. A safe zone for screw placement was found in 100% of cases (200 screws), 17.0±1.1 mm from midline and a width of 12.6±1.7 mm. Posterior tubercle morphology was variable. CONCLUSIONS: C1 lateral mass screws could be virtually placed bilaterally in each of 100 clinical cases without violating critical structures. However, none of the previously described approaches worked in every case because of significant anatomic variability. The vertical starting point was particularly critical, and vertebral groove height was the most limiting variable. Although a reliable safe zone could be found in every case, preoperative planning is essential to avoid critical structures.

A cadaver study to compare vertebral augmentation with a high-viscosity cement to augmentation with conventional lower-viscosity cement.

STUDY DESIGN: Comparison of extravasations in fractured cadaver vertebrae augmented with commercial low-viscosity versus high-viscosity cements. OBJECTIVE: Use of high-resolution, 3-dimensional (3D) imaging to test the hypothesis that high-viscosity cements can reduce the type and severity of extravasations after vertebral augmentation procedures. SUMMARY OF BACKGROUND DATA: Cement extravasations are one of the primary complications of vertebral augmentation procedures. There is some evidence that high-viscosity cements might reduce extravasations, but additional data are needed to confirm the early findings. METHODS: A range of vertebral fractures were created in fresh human cadavers. One group was then augmented with a low-viscosity polymethylmethacrylate (PMMA)-based cement and the other group injected with high-viscosity PMMA-based cement. High-resolution computerized tomography exams were obtained, and extravasations were assessed using 3D volume renderings. The type and severity of extravasations were recorded and analyzed. RESULTS: The proportion of vertebrae with any type of extravasation through the posterior wall to the spinal canal, into small vessels laterally or anteriorly, through the endplates, or anywhere around the body was not significantly different between the high-viscosity and low-viscosity groups. There was significantly less severe extravasation through the endplates (P=0.02), and a trend toward less severe extravasation through vessels (P=0.06) with the high versus low-viscosity cements. CONCLUSIONS: In agreement with previous research, high-viscosity PMMA-based cement may help to reduce the more severe forms of extravasations after vertebral augmentation procedures in newly fractured vertebrae.

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.

Reference data for interpreting widening between spinous processes in the lumbar spine.

BACKGROUND CONTEXT: Traumatic injury to the lumbar spine is evaluated and treated based on the perceived stability of the spine. Recent classification schemes have established the importance of evaluating the posterior ligamentous complex (PLC) to fully comprehend stability. There are a variety of techniques to evaluate the PLC, including assessment of interspinous distance. However reference data to define normal widening are poorly developed. PURPOSE: Define normal interspinous widening in the lumbar spine. STUDY DESIGN: Biomechanical and observational. To establish reference data for asymptomatic population and use the reference data to suggest criteria for routine clinical practice to be validated in future studies. METHODS: Interspinous distances were measured from lateral lumbar X-rays of 157 asymptomatic volunteers. Measurements from the asymptomatic population were used to define normal limits and create a simple screening tool for clinical use. Distances were calculated from the relative position of landmarks at each intervertebral level. The distances were normalized to the anterior-posterior width of the superior end plate of L3. The change in interspinous process distance from flexion to extension was calculated, and the change in interspinous widening between flexion and extension with respect to widening at the adjacent levels was also calculated. RESULTS: Seven hundred seventy-two thoracolumbar levels were available for analysis. The observed interspinous motion was slightly more than the interlaminar motion. However, the tips of the spinous processes were more difficult to identify in some images, so the interlaminar line distances were considered more reliable. Significant difference in interlaminar distances was not found between levels. The upper limit (UL) of normal spacing measured between the interlaminar lines was approximately 85% of the L3 end plate width at all levels except L5-S1, which was 105%. The UL of normal for interlaminar displacements between flexion and extension was 30% of the L3 end plate width at L1-L2 to L4-L5 and 40% at L5-S1. CONCLUSIONS: This study provides normative data and methods that can be used in developing guidelines to objectively assess interspinous process widening. Simple rules can be applied to quickly assess interspinous widening. Additional research is required to validate these guidelines. A simple measurement such as spinous process widening is unlikely to be proven as an isolated clinically effective screening test but combining that with other patient evaluation's screening modalities may prove to be a sensitive evaluation protocol for the screening of injuries to the PLC.

Sagittal alignment after Bryan cervical arthroplasty.

STUDY DESIGN: Prospective, randomized, Food and Drug Administration Investigational Device Exemption trial from one study site. OBJECTIVE: Examine the radiographic sagittal alignment of the Bryan cervical disc for one-level disease. SUMMARY OF BACKGROUND DATA: Prospective, randomized studies demonstrate Bryan arthroplasty provides statistically better functional outcomes than anterior cervical discectomy and fusion. Uncontrolled case reports describe kyphosis after disc replacement. No prospective study has critically assessed sagittal alignment after cervical arthroplasty. METHODS: Forty-eight patients reviewed with a minimum follow-up of 2 years. Quantitative motion analysis determined the change in overall (C2-C7) and treatment-level sagittal alignment, disc space heights, and range of motion. RESULTS: Preoperatively, overall sagittal alignment was equivalent in the two groups. At 24-month follow-up, overall lordosis for the cohorts was not statistically different from preoperative values for each group. In addition, overall lordosis was not significantly different at 24 months when comparing Bryan patients with the fusion patients. The average change in disc angle from preoperative to immediate postoperative at the treated level in the Bryan disc group was a nonsignificant increase in lordosis of 0.92°. The anterior disc height was the same at all time points, but the posterior disc height was slightly (0.7 mm) more in the Bryan than in the fusion patients (P = 0.04). The angular range of motion in the Bryan group was statistically equivalent at all time points. At the fused levels, average range of motion decreased from 6.4° to 0.9° at 24 months (P < 0.0001). CONCLUSION: With the Bryan disc, there was an insignificant increase in lordosis of 0.9° at immediate postoperative time point. Overall cervical sagittal alignment is not different between the experimental and control populations. This prospective study does not demonstrate a clinically significant increase in segmental kyphosis after Bryan disc arthroplasty. Global cervical lordosis is statistically equivalent between arthroplasty and fusion groups at 2 years follow-up.

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.

Motion within the unstable cervical spine during patient maneuvering: the neck pivot-shift phenomenon.

BACKGROUND: Cervical extrication collars are applied to millions of blunt trauma victims despite the lack of any evidence that a collar can protect against secondary injuries to the cervical spine. Cadaver studies support that in the presence of a dissociative injury, substantial motion can occur within the occipitocervical spine with collar application or during patient transfers. Little is known about the biomechanics of cervical stabilization; hence, it is difficult to develop and test improved immobilization strategies. MATERIALS: Severe unstable injuries were created in seven fresh whole human cadavers. Rigid collars were applied with the body in a neutral position. Computed tomographic examinations were obtained before and after tilting the body or backboard as would be done during patient transport or to inspect the back. Relative displacements between vertebrae at the site of the injury were measured from the Computed tomographic examinations. The overall relative alignment between body and collar was assessed to understand the mechanisms that may facilitate motion at the injury site. RESULTS: Intervertebral motion averaged 7.7 mm±6.8 mm in the axial plain and 2.9 mm±2.5 mm in the cranial-caudal direction. The rigid collars appeared to create pivot points where the collar contacts the head in the region under the ear and where the collar contacts the shoulders. DISCUSSION: Rigid cervical collars appear to create pivot points that shift the center of rotation lateral to the spine and contribute to the intervertebral motions that were measured. Immobilization strategies that avoid these neck pivot-shift phenomena may help to reduce secondary injuries to the cervical spine. The whole cadaver model with simulation of patient maneuvers may provide an effective test method for cervical immobilization.

Long-term functional implications of the iatrogenic rotational malalignment of healed diaphyseal femur fractures following intramedullary nailing.

BACKGROUND: The long-term functional implications for patients with iatrogenic femoral malrotation following femoral intramedullary nail fixation remain unclear. This study examined the extent and direction of rotational alignment of the femur treated with intramedullary nail fixation and its long-term functional effects on patients' standing, walking, and subjective outcome. METHODS: Rotational alignment was measured using a CT-based protocol. Foot alignment while standing or walking was determined bilaterally using a pressure mat. Subjective functional outcome was assessed using a questionnaire. FINDINGS: Sixteen patients (5F, 11 M; age: mean 44.3 years, range 24-75 years) with a healed femur fracture were included. Femur alignment demonstrated internal rotation in five patients (mean 6°; range 2-13°), and external rotation in 11 (mean 18°; range 3-32°). Static foot rotation demonstrated neutral rotation in two patients, internal rotation in four (mean 13°; range 5-22°), and external rotation in 10 (mean 15°; range 5-24°). Dynamic foot rotation demonstrated neutral rotation in two patients, internal rotation in two (mean 11°; range 4-26°), and external rotation in 12 (mean 11°; range 3-22°). There was a trend for increasing dynamic malrotation with femoral rotation (r(2)=0.27; p=0.055). In half the patients, dynamic foot rotation correlated with the extent of femoral malrotation. There was no association (p=0.6) between overall patient satisfaction (10 fully satisfied; 5 partially satisfied; and 1 dissatisfied) and foot alignment. INTERPRETATION: Patients can compensate for even significant femoral malrotation and tolerate it well. External femoral malrotation appears to be better compensated/tolerated than internal malrotation.