Harvey E. Smith

Trends in epidemiology and management of type II odontoid fractures: 20-year experience at a model system spine injury tertiary referral center.

Study Design A retrospective cohort study of consecutive type II Odontoid fractures presenting to a Level 1 Regional Model Systems Spinal Cord Injury Center between June 1985 and July 2006. Objective To assess trends in management of type II Odontoid fractures presenting to a Level 1 Model Systems Regional Spinal Cord Injury Center over a 20-year period. Summary of Background Data Type II Odontoid fracture management is controversial, and a majority of studies have had relatively small cohorts. There is no consensus regarding definitive treatment, particularly in older patients. Methods Medical records of 263 consecutive type II Odontoid fractures from June 1985 to July 2006 were retrospectively reviewed. Patients were excluded if they had neurologic deficits, nonacute fracture, or ambiguous fracture classification. A cohort of 192 neurologically intact, acute type II odontoid fractures were identified. Admission records were reviewed for age, date of injury, date of admission, date of discharge, mechanism of injury, associated injuries, medical comorbidities, and radiologic findings. Results There was a statistically significant increase in the rate of presentation of type II odontoid fractures with time. The average age and medical comorbidities of the patient did not change over time. The probability of operative management markedly increased over time, corresponding to a statistically significant increase in length of hospital stay for patients undergoing surgery. The discharge disposition correlated significantly to both age of the patient and associated injuries. Conclusions The number and frequency of type II odontoid fractures compared with other spine injuries seems to be increasing over the last 2 decades, which may be correlated with the increasing number of elderly persons in the population, given that referral patterns have been unchanged at our institution. Prospective outcomes data are needed to better elucidate optimal treatment algorithms from both, an outcomes and cost-efficacy perspective.

An evaluation of image-guided technologies in the placement of percutaneous iliosacral screws.

Study Design. A surgical simulation study in human cadaver spine specimens was conducted to evaluate the accuracy of 3 different surgical navigation systems compared to standard fluoroscopy in the percutaneous placement of iliosacral screws. Objectives. To compare the accuracy of percutaneous iliosacral screw placement using standard fluoroscopy, computer-assisted fluoroscopic image guidance, Iso-C3D image guidance (Medtronic Surgical Navigation Technologies, Louisville, CO), and electromagnetic fluoroscopic image guidance. Summary of Background Data. Conventional percutaneous sacroiliac screw placement has a malposition rate as high as 15%, as reported in the English-speaking literature (Hinsche et al [Clin Orthop Relat Res 2002;395:135–44] and Templeman et al [Clin Orthop Relat Res 1996;329:194–8]). Iso-C3D and computer-assisted image guidance technologies have been proposed to increase this accuracy rate. Methods. Two iliosacral screws were placed bilaterally (4 screws) in each of 4 cadavers using standard fluoroscopy, computer-assisted fluoroscopic image guidance, Iso-C3D image guidance, and electromagnetic fluoroscopic image guidance. Screw positions were analyzed by computerized tomography after instrumentation and assigned a score based on deviation from ideal screw position. Results. The StealthStation® with FluoroNav® (Medtronic Surgical Navigation Technologies) appeared to provide the highest accuracy of all guidance techniques. This result was more accurate than standard fluoroscopy. Conclusions. Computer-assisted fluoroscopy based image navigation appears to be more accurate than standard fluoroscopy in placing these screws. However, errors may occur with all techniques. Further refinement in registration procedures may highly improve the accuracy of percutaneous screw placement in a variety of spinopelvic procedures.

Using magnetic resonance imaging to accurately assess injury to the posterior ligamentous complex of the spine: a prospective comparison of the surgeon and radiologist

OBJECT Magnetic resonance imaging has been proposed as a powerful technique for assessing the integrity of the posterior ligamentous complex (PLC) in spinal trauma. Because MR imaging is often used to determine appropriate treatment, it is important to determine the accuracy and reliability of MR imaging in diagnosing PLC disruption. The purpose of this study is to compare the ability of the radiologist and surgeon to assess disruption of the PLC in the setting of acute cervical and thoracolumbar trauma using MR imaging. METHODS The components of the PLC in 89 consecutive patients with cervical or thoracolumbar fractures following acute spinal trauma were evaluated using MR imaging by both a musculoskeletal radiologist and an independent spine surgeon and assessed intraoperatively under direct visualization by the treating surgeon. The MR imaging interpretations of the musculoskeletal radiologist and surgeon were compared with the intraoperative report for accuracy, sensitivity, specificity, and positive and negative predictive values. A comparison between the radiologists and spine surgeons accuracy of MR imaging interpretation was performed. RESULTS The agreement between both the spine surgeons and radiologists MR imaging interpretation and the actual intraoperative findings was moderate for most components of the PLC. Overall, the MR imaging interpretation of the surgeon was more accurate than that of the radiologist. The interpretation of MR imaging by the surgeon had negative predictive value and sensitivity of up to 100%. However, the specificity of MR imaging for both the surgeon and radiologist was lower, ranging from 51.5 to 80.5%. CONCLUSIONS Comparison of the MR imaging interpretations between surgeon and radiologist indicates that the surgeon was more accurate for some PLC components. The relatively low positive predictive value and specificity for MR imaging in assessing PLC integrity suggests that both the surgeon and radiologist tend to overdiagnose PLC injury using MR imaging. This can lead to unnecessary surgeries if only MR imaging is used for treatment decision making.

Cervical myelopathy: a clinical and radiographic evaluation and correlation to cervical spondylotic myelopathy.

Study Design. Retrospective analysis of a cohort of patients treated between April 2006 and January 2008, and diagnosed with cervical degenerative disease. Objective. To determine the correlation of the clinical findings associated with cervical myelopathy to the presence of spinal cord compression or cord signal abnormalities on magnetic resonance imaging (MRI). Summary of Background Data. There are numerous reports describing the radiographic features of cervical spondylosis, however, no publication specifically describes the association between the physical signs of cervical myelopathy and the presenting imaging findings. Methods. Myelopathy was defined as the presence of greater than one long-tract sign localized to the cervical spinal cord (Hoffman or Babinski signs, clonus, hyper-reflexia, crossed abductor sign, and/or gait dysfunction) on physical examination in the absence of other neurologic condition(s). The presence of these signs, MRI imaging features of spinal cord compression and hyperintense T2 intraparenchymal cord signal abnormality, and patient demographics were recorded. Results. One hundred three patients met inclusion criteria (age >18, symptomatic cervical degenerative disease and complete neurologic assessment). Of these, 54 had clinical findings of cervical myelopathy. Radiographic features of cord compression were present in 62% of patients, and 84% had myelopathy on examination. No patients without cord compression presented with myelopathy (P < 0.0001). Thirty-five percent of the patients presented with hyperintense signal on T2 MRI within the spinal cord parenchyma. This finding correlated with the presence of myelopathy (P < 0.0001). Multivariate analysis on the subset with cord compression indicates that the likelihood of myelopathy increased with the presence of cord signal hyperintensity (odds ratio [OR], 11.4), sensory loss (OR, 16.9), and age (OR, 1.10 per year). Conclusion. The diagnosis of cervical myelopathy is based on presenting symptoms and physical examination. This analysis illustrates that radiographic cervical spinal cord compression and hyperintense T2 intraparen chymal signal abnormalities correlate with the presence of myelopathic findings on physical examination.

The use of computerized image guidance in lumbar disk arthroplasty.

Objectives: Surgical navigation systems have been increasingly studied and applied in the application of spinal instrumentation. Successful disk arthroplasty requires accurate midline and rotational positioning for optimal function and longevity. A surgical simulation study in human cadaver specimens was done to evaluate and compare the accuracy of standard fluoroscopy, computer-assisted fluoroscopic image guidance, and Iso-C3D image guidance in the placement of lumbar intervertebral disk replacements. Methods: Lumbar intervertebral disk prostheses were placed using three different image guidance techniques in three human cadaver spine specimens at multiple levels. Postinstrumentation accuracy was assessed with thin-cut computed tomography scans. Results: Intervertebral disk replacements placed using the StealthStation with Iso-C3D were more accurately centered than those placed using the StealthStation with FluoroNav and standard fluoroscopy. Intervertebral disk replacements placed with Iso-C3D and FluoroNav had improved rotational divergence compared with standard fluoroscopy. Iso-C3D and FluoroNav had a smaller interprocedure variance than standard fluoroscopy. These results did not approach statistical significance. Relative to both virtual and standard fluoroscopy, use of the StealthStation with Iso-C3D resulted in improved accuracy in centering the lumbar disk prosthesis in the coronal midline. Conclusions: The StealthStation with FluoroNav appears to be at least equivalent to standard fluoroscopy and may offer improved accuracy with rotational alignment while minimizing radiation exposure to the surgeon. Surgical guidance systems may offer improved accuracy and less interprocedure variation in the placement of intervertebral disk replacements than standard fluoroscopy. Further study regarding surgical navigation systems for intervertebral disk replacement is warranted.

Correlation of C2 fractures and vertebral artery injury.

Study Design. Retrospective review of prospectively collected data. Summary of Background Data. Vertebral artery injuries (VAI) occur commonly after cervical spine trauma. No study has yet examined the association between VAI and specific variants of C2 fractures. Objective. To evaluate the incidence of VAI (as defined by magnetic resonance imaging/angiography [MRI/A]) in subtypes of C2 fractures. To define the association between the incidence, morphology, and severity of C2 fractures, based on fracture angulation and comminution, and the occurrence of VAI. Methods. Patients admitted to the hospital with C2 fractures between October 2006 and December 2008 to a tertiary care referral center were identified through a prospectively maintained database. Computed tomography (CT) and MRI/A studies were individually reviewed to evaluate the specific C2 fracture type and the occurrence of VAI. Fracture displacement and angulation were measured. Incidence of VAI was compared between different types and subtypes of C2 fractures. The effects of displacement and angulation of the fracture, morphology of foramen transversarium fracture, patient age, and patient gender on VAI were also analyzed. Results. One hundred one patients were identified with C2 fractures that met inclusion criteria, and 18 (17.8%) had VAI by MRI/A. There was no correlation between fracture types and VAI. However, in subtype analysis, there was a correlation of VAI with traumatic spondylolisthesis of axis (TSA) and greater degree of angulation (P = 0.0023), communition fracture (P = 0.0341), and presence of bone fragment(s) within the foramen transversarium (P = 0.0075). Multivariate logistic regression indicated that age, gender and the presence of fragments within foramen transversarium were associated with greater risk of VAI. Conclusion. Vertebral artery injuries are more likely to occur in C2 fractures with comminuted fractures involving the foramen transversarium, with fractures manifesting bony fragment(s) within the foramen transversarium, or with fractures having greater angulation. These risk factors should be considered when a patient presents with isolated axis fracture.

Cell therapy for the degenerating intervertebral disc

Spinal conditions related to intervertebral disc (IVD) degeneration cost billions of dollars in the US annually. Despite the prevalence and soaring cost, there is no specific treatment that restores the physiological function of the diseased IVD. Thus, it is vital to develop new treatment strategies to repair the degenerating IVD. Persons with IVD degeneration without back pain or radicular leg pain often do not require any intervention. Only patients with severe back pain related to the IVD degeneration or biomechanical instability are likely candidates for cell therapy. The IVD progressively degenerates with age in humans, and strategies to repair the IVD depend on the stage of degeneration. Cell therapy and cell-based gene therapy aim to address moderate disc degeneration; advanced stage disease may require surgery. Studies involving autologous, allogeneic, and xenogeneic cells have all shown good survival of these cells in the IVD, confirming that the disc niche is an immunologically privileged site, permitting long-term survival of transplanted cells. All of the animal studies reviewed here reported some improvement in disc structure, and 2 studies showed attenuation of local inflammation. Among the 50 studies reviewed, 25 used some type of scaffold, and cell leakage is a consistently noted problem, though some studies showed reduced cell leakage. Hydrogel scaffolds may prevent cell leakage and provide biomechanical support until cells can become established matrix producers. However, these gels need to be optimized to prevent this leakage. Many animal models have been leveraged in this research space. Rabbit is the most frequently used model (28 of 50), followed by rat, pig, and dog. Sheep and goat IVDs resemble those of humans in size and in the absence of notochordal cells. Despite this advantage, there were only 2 sheep and 1 goat studies of 50 studies in this cohort. It is also unclear if a study in large animals is needed before clinical trials since some of the clinical trials proceeded without a study in large animals. No animal studies or clinical trials completely restored IVD structure. However, results suggest cause for optimism. In light of the fact that patients primarily seek medical care for back pain, attenuating local inflammation should be a priority in benchmarks for success. Clinicians generally agree that short-term back pain should be treated conservatively. When interventions are considered, the ideal therapy should also be minimally invasive and concurrent with other procedures such as discography or discectomy. Restoration of tissue structure and preservation of spinal motion are desirable.

A radiopaque electrospun scaffold for engineering fibrous musculoskeletal tissues: Scaffold characterization and in vivo applications

UNLABELLED Tissue engineering strategies have emerged in response to the growing prevalence of chronic musculoskeletal conditions, with many of these regenerative methods currently being evaluated in translational animal models. Engineered replacements for fibrous tissues such as the meniscus, annulus fibrosus, tendons, and ligaments are subjected to challenging physiologic loads, and are difficult to track in vivo using standard techniques. The diagnosis and treatment of musculoskeletal conditions depends heavily on radiographic assessment, and a number of currently available implants utilize radiopaque markers to facilitate in vivo imaging. In this study, we developed a nanofibrous scaffold in which individual fibers included radiopaque nanoparticles. Inclusion of radiopaque particles increased the tensile modulus of the scaffold and imparted radiation attenuation within the range of cortical bone. When scaffolds were seeded with bovine mesenchymal stem cells in vitro, there was no change in cell proliferation and no evidence of promiscuous conversion to an osteogenic phenotype. Scaffolds were implanted ex vivo in a model of a meniscal tear in a bovine joint and in vivo in a model of total disc replacement in the rat coccygeal spine (tail), and were visualized via fluoroscopy and microcomputed tomography. In the disc replacement model, histological analysis at 4 weeks showed that the scaffold was biocompatible and supported the deposition of fibrous tissue in vivo. Nanofibrous scaffolds that include radiopaque nanoparticles provide a biocompatible template with sufficient radiopacity for in vivo visualization in both small and large animal models. This radiopacity may facilitate image-guided implantation and non-invasive long-term evaluation of scaffold location and performance. STATEMENT OF SIGNIFICANCE The healing capacity of fibrous musculoskeletal tissues is limited, and injury or degeneration of these tissues compromises the standard of living of millions in the US. Tissue engineering repair strategies for the intervertebral disc, meniscus, tendon and ligament have progressed from in vitro to in vivo evaluation using a variety of animal models, and the clinical application of these technologies is imminent. The composition of most scaffold materials however does not allow for visualization by methods available to clinicians (e.g., radiography), and thus it is not possible to assess their performance in situ. In this work, we describe a radiopaque nanofibrous scaffold that can be visualized radiographically in both small and large animal models and serve as a framework for the development of an engineered fibrous tissue.

Correlations between quantitative T2 and T1ρ MRI, mechanical properties and biochemical composition in a rabbit lumbar intervertebral disc degeneration model.

Improved diagnostic measures for intervertebral disc degeneration are necessary to facilitate early detection and treatment. The aim of this study was to correlate changes in mechanical and biochemical properties with the quantitative MRI parameters T2 and T1ρ in rabbit lumbar discs using an ex vivo chymopapain digestion model. Rabbit lumbar spinal motion segments from animals less than 6 months of age were injected with 100 μl of saline (control) or chymopapain at 3, 15, or 100 U/ml (n = 5 per group). T2 and T1ρ MRI series were obtained at 4.7T. Specimens were mechanically tested in tension–compression and creep. Normalized nucleus pulposus (NP) water and GAG contents were quantified. Stepwise multiple linear regression was performed to determine which parameters contributed significantly to changes in NP T2 and T1ρ. When all groups were included, multiple regression yielded a model with GAG, compressive modulus, and the creep time constants as variables significantly impacting T2 (multiple r2 = 0.64, p = 0.006). GAG and neutral zone (NZ) modulus were identified as variables contributing to T1ρ (multiple r2 = 0.28, p = 0.08). When specimens with advanced degeneration were excluded from the multiple regression analysis, T2 was significantly predicted by compressive modulus, τ1, and water content (multiple r2 = 0.71, p = 0.009), while no variables were significant predictors in the model for T1ρ. These results indicate that quantitative MRI can detect changes in the mechanical and biochemical properties of the degenerated disc. T2 may be more sensitive to early stage degenerative changes than T1ρ, while both quantitative MRI parameters are sensitive to advanced degeneration.

Spine care: evaluation of the efficacy and cost of emerging technology.

Over the last decade a number of new technologies have been introduced to the area of spine care. Although this recent explosion of innovation has brought advances to patient care, it has also brought concerns regarding overuse, increasing costs, and safety. A value-based approach to assessing and purchasing new technology depends on a shift toward comparative effectiveness analysis, transparency in pricing and potential conflicts of interest, and an alignment of incentives and goals among purchasers, consumers, and payers. How to assess the effectiveness of new technology in patient care is an unresolved issue for any cost-effectiveness analysis, as models traditionally used to assess medical therapies (ie, quality-adjusted life years) may not be directly applicable to analysis of surgical intervention. Spine surgeons must be involved in multidisciplinary collaborative efforts to develop models of efficacy analysis and to direct outcomes-based research to appropriately evaluate the benefits of surgical interventions and new technologies.