Cervical spine degeneration specific segmental angular rotational and displacements: A quantitative study.

BACKGROUND: The objective of the present isolated spine study was to evaluate the kinematic differences between groups of normal and degenerated cervical spine specimens. Previous studies on cervical spine degeneration support the existence of the unstable phase during the degeneration process; however, there is a lack of quantitative data available to fully characterize this early stage of degeneration. METHOD: For this effort five degenerated and eight normal cervical spines (C2-T1) were isolated and were subject to pure bending moments of flexion, extension, axial rotation and lateral bending. The specimen quality was assessed based on the grading scale. In the present study, the degeneration was at the C5-C6 level. A four-camera motion analysis system was used to measure the overall primary and segmental motions. FINDING: In the extension mode, the degenerated group demonstrated a significant larger angular rotation as well as antero-posterior displacement at the degenerated level (C5-C6). In contrast, in flexion mode, the degenerated group measured a drastic decrease in angular rotation, at the adjacent level (C6-C7). In other modes of loading as well as in other segmental levels, the degenerated group had similar segmental motion as the normal group. INTERPRETATION: These preliminary results provide single level degeneration specific cervical spine kinematics. The finding demonstrates the influence of degeneration on the kinematics of the normal sub adjacent segment. The degenerated group observed larger translation displacement in the extension mode, which would potentially be a critical parameter in assisting early detection of cervical spine spondylosis with just a functional X-ray scan.

Great Hospitals in North America: The Medical College of Wisconsin Neurological Surgery.

The Medical College of Wisconsin Department of Neurosurgery delivers subspecialty adult and pediatric neurosurgical care that is patient-centered, evidence-informed, and value-based. Medical College of Wisconsin research advances the science of neurological disease with the goal of a positive translational effect on clinical care. The department supports an environment of education and scholarship for trainees, faculty, and staff alike. The journey to become a neurosurgical center of excellence was accomplished with the leadership and foresight of the men and women who turned their dreams into reality. The establishment and rise of the department as a national force for neurosurgery and spine is an elegant example of the combination of individual leadership and foresight with synergistic institutional support.

Posterior cervical spine crisscross fixation: Biomechanical evaluation.

BACKGROUND: Biomechanical/anatomic limitations may limit the successful implantation, maintenance, and risk acceptance of posterior cervical plate/rod fixation for one stage decompression-fusion. A method of posterior fixation (crisscross) that resolves biomechanical deficiencies of previous facet wiring techniques and not reliant upon screw implantation has been devised. The biomechanical performance of the new method of facet fixation was compared to the traditional lateral mass plate/screw fixation method. METHODS: Thirteen human cadaver spine segments (C2-T1) were tested under flexion-compression loading and four were evaluated additionally under pure-moment load. Preparations were evaluated in a sequence of surgical alterations with intact, laminectomy, lateral mass plate/screw fixation, and crisscross facet fixation using forces, displacements and kinematics. FINDINGS: Combined loading demonstrated significantly lower bending stiffness (p < 0.05) between laminectomy compared to crisscross and lateral mass plate/screw preparations. Crisscross fixation showed a comparative tendency for increased stiffness. The increased overall motion induced by laminectomy was resolved by both fixation techniques, with crisscross fixation demonstrating a comparatively more uniform change in segmental motions. INTERPRETATION: The crisscross technique of facet fixation offers immediate mechanical stability with resolution of increased flexural rotations induced by multi-level laminectomy. Many of the anatomic limitations and potentially deleterious variables that may be associated with multi-level screw fixation are not associated with facet wire passage, and the subsequent fixation using a pattern of wire connection crossing each facet joint exhibits a comparatively more uniform load distribution. Crisscross wire fixation is a valuable addition to the surgical armamentarium for extensive posterior cervical single-stage decompression-fixation.

Unilateral atlanto-axial fractures in near side impact collisions: An under recognized entity in cervical trauma.

OBJECTIVE: Nearside impact collisions presenting with lateral mass fractures of atlanto-axial vertebrae contralateral to the impact site represents a rare fracture pattern that does not correlate with previously described injury mechanism. We describe our clinical experience with such fractures and propose a novel description of biomechanical forces involved in this unique injury pattern. The findings serve to alert clinicians to potentially serious consequences of associated unrecognized and untreated vertebral artery injury. MATERIAL AND METHODS: In addition to describing our clinical experience with three of these fractures, a review of Crash Injury Research and Engineering Network (CIREN) database was conducted to further characterize such fractures. A descriptive analysis of three recent lateral mass fractures of the atlanto-axial segment is coupled with a review of the CIREN database. A total of 4047 collisions were screened for unilateral fractures of atlas or axis. Information was screened for side of impact and data regarding impact velocity, occupant injuries and use of restraints. RESULTS: Following screening of unilateral fractures of atlas and axis for direct side impacts, 41 fractures were identified. Cross referencing these cases for occurrence contralateral to side of impact identified four such fractures. Including our recent clinical experience, seven injuries were identified: Five C1 and two C2 fractures. Velocity ranged from 14 to 43 km/h. Two associated vertebral artery injuries were identified. CONCLUSIONS: Complexity of the atlanto-axial complex is responsible for a sequence of events that define load application in side impacts. This study demonstrates the vulnerability of vertebral artery to injury under unique translational forces and supports the use or routine screening for vascular injury. Diminished sensitivity of plain radiography in identifying these injuries suggests that computerized tomography should be used in all patients wherein a similar pattern of injury is suspected.

Stabilizing effect of precontracted neck musculature in whiplash.

STUDY DESIGN: This study investigated the effect of neck muscle precontraction in aware occupants in whiplash. Head angulation relative to T1 and facet joint capsular ligament distractions were compared between aware and unaware occupants. OBJECTIVE: To quantify changes in facet joint capsular ligament distractions between aware occupants with precontracted neck muscles and unaware occupants with reflex muscle contraction. SUMMARY OF BACKGROUND DATA: Clinical studies have reported that patients aware of the impending impact had decreased symptom intensity and faster recovery after whiplash. To date, no study has investigated the effects of precontracted neck musculature on localized spinal soft tissue distortions in whiplash. METHODS: Aware occupants with precontracted neck muscles and unaware occupants with reflex muscle contraction in whiplash were simulated using a validated computational model. Muscle contraction attained maximum levels before impact in the aware occupant and implemented reflex delay, electromechanical delay, and finite muscle rise time in the unaware occupant. RESULTS: Precontraction of neck muscles in aware occupants resulted in 63% decreased maximum head angles, elimination of cervical S-curvature, and up to 75% decrease in maximum facet joint capsular ligament distractions. CONCLUSIONS: Occupants aware of an impending whiplash impact with precontracted neck muscles can markedly reduce overall head-neck and spinal motions. It is our theory that this would reduce whiplash injury likelihood.

Treating osteoporotic and neoplastic vertebral compression fractures with vertebroplasty and kyphoplasty.

BACKGROUND: Compression fractures are common in patients with osteoporosis and cancer. In particular, vertebral compression fractures are crippling, and pose an additional risk of cord compression. Although a number of nonmedical options such as bracing and exercise programs may help these patients, the combination of constant, severe pain and spinal instability was until recently almost invariably synonymous with painful gradual deterioration and a poor quality of life. Vertebroplasty, and more recently kyphoplasty, are minimally invasive procedures that aim at limiting or reversing painful collapse of the vertebrae, while providing stability to the treated segment of the spine. As these new options are highly effective and involve minimal risk, it is important that physicians be familiar with them. OBJECTIVE: This paper reviews the demographics of vertebral compression fractures, both osteoporotic and neoplastic, the technical aspects of vertebroplasty and kyphoplasty, and current results and outcomes. RESULTS: Pain relief rates in excess of 90% have been reported with both vertebroplasty and kyphoplasty in patients with vertebral compression fractures. Procedural complication rates should be very low, in the 1%-2% range at most with proper technique. CONCLUSIONS: Until the advent of vertebroplasty, almost no effective therapeutic option could be offered to patients suffering from neoplastic or osteoporotic vertebral compression fractures, which are relatively common and often crippling. The technical feasibility of these procedures is high, the risk low, and the effectiveness high. Therefore, it is important that physicians consider vertebroplasty and kyphoplasty as viable and strong options.

Ruptured saccular aneurysm of distal vertebral artery fenestration managed with Guglielmi detachable coils and intraventricular tissue plasminogen activator.

BACKGROUND: Aneurysms associated with vertebrobasilar fenestrations are uncommon. We report on an unusual presentation of such aneurysm with a dedicated arterial pedicle, manifesting with significant intraventricular hemorrhage. Equally important, the aneurysm was managed in a multidisciplinary fashion, which, we think, greatly contributed to a good outcome. CASE DESCRIPTION: A 55-year-old man presented in good condition after subarachnoid and massive intraventricular hemorrhage. The aneurysm location and the extent of intraventricular hemorrhage both presented concerns regarding treatment approach. The aneurysm was first treated with transarterial coil obliteration, and intraventricular tissue plasminogen activator (tPA) infusion was given, with rapid resolution of evolving hydrocephalus. The patient had an excellent outcome. CONCLUSION: To our knowledge, this is the first report of a vertebrobasilar fenestration saccular aneurysm with a dedicated pedicle projecting toward the foramen of Magendie with significant intraventricular hemorrhage. In addition, this patient was successfully managed with endovascular obliteration and intraventricular tPA infusion.

Biomechanical analyses of whiplash injuries using an experimental model.

Neck pain and headaches are the two most common symptoms of whiplash. The working hypothesis is that pain originates from excessive motions in the upper and lower cervical segments. The research design used an intact human cadaver head-neck complex as an experimental model. The intact head-neck preparation was fixed at the thoracic end with the head unconstrained. Retroreflective targets were placed on the mastoid process, anterior regions of the vertebral bodies, and lateral masses at every spinal level. Whiplash loading was delivered using a mini-sled pendulum device. A six-axis load cell and an accelerometer were attached to the inferior fixation of the specimen. High-speed video cameras were used to obtain the kinematics. During the initial stages of loading, a transient decoupling of the head occurs with respect to the neck exhibiting a lag of the cranium. The upper cervical spine-head undergoes local flexion concomitant with a lag of the head while the lower column is in local extension. This establishes a reverse curvature to the head-neck complex. With continuing application of whiplash loading, the inertia of the head catches up with the neck. Later, the entire head-neck complex is under an extension mode with a single extension curvature. The lower cervical facet joint kinematics demonstrates varying local compression and sliding. While the anterior- and posterior-most regions of the facet joint slide, the posterior-most region of the joint compresses more than the anterior-most region. These varying kinematics at the two ends of the facet joint result in a pinching mechanism. Excessive flexion of the posterior upper cervical regions can be correlated to headaches. The pinching mechanism of the facet joints can be correlated to neck pain. The kinematics of the soft tissue-related structures explain the mechanism of these common whiplash associated disorders.

Lateral supratentorial endodermal cyst: case report and review of literature.

OBJECTIVE AND IMPORTANCE: Epithelial cysts of the central nervous system are unusual entities, with the majority reported to occur in the spinal canal. More unusual is the intracranial presentation, which shows a predilection for midline localization in the posterior fossa, brainstem, and suprasellar regions. This report discusses the differential diagnosis, pathogenesis, radiographic presentation, and therapeutic considerations of a laterally positioned cerebral convexity endodermal cyst. CLINICAL PRESENTATION: A 49-year-old right-handed man presented with approximately a 30-month history of short- and long-term memory difficulties. A magnetic resonance imaging study revealed a large, nonenhancing, extra-axial cystic lesion overlying the right lateral frontal convexity. INTERVENTION: A right frontoparietal craniotomy exposed a large extra-axial cyst with an opaque, yellowish-white membrane containing a mucoid fluid. Histological analysis disclosed a layer of unremarkable, ciliated columnar epithelium with a basement membrane that stained positive for cytokeratin, periodic acid-Schiff, and Alcian blue. No evidence of either a muscular or cartilaginous layer around the mucosa was present to further delineate neurenteric versus bronchogenic origin of the cyst. CONCLUSION: This case involved the occurrence of a solitary endodermal cyst as an extra-axial mass localized over the lateral frontal lobe. The lateral supratentorial localization of this lesion illustrates the need for consideration of the pathogenesis of this entity as well as its diagnostic differentiation from other cystic abnormalities in this region. A review of the histochemistry of endodermal, neuroepithelial, and other cerebral cysts is presented.

Biomechanics of the cervical spine 4: major injuries.

This review presents considerations regarding major cervical spine injury, including some concepts that are presently undergoing evaluation and clarification. Correlation of certain biomechanical parameters and clinical factors associated with the causation and occurrence of traumatic cervical spine injuries assists in clarifying the pathogenesis and treatment of this diverse group of injuries. Instability of the cervical column based on clinical and mechanistic perspectives as well as the role of ligaments in determining instability is discussed. Patient variables such as pre-existing conditions (degenerative disease) and age that can influence the susceptibility or resistance to injury are reviewed. Radiological considerations of major injuries including dynamic films, CT and MRI are presented in the diagnosis and treatment of cervical trauma. Specific injury patterns of the cervical vertebral column are described including attention to the relative mechanisms of trauma. From a biomechanical perspective, quantification of injury tolerance is discussed in terms of external and human-related variables using laboratory-driven experimental models. This includes force vectors (type, magnitude, direction) responsible for injury causation, as well as potential influences of loading rate, gender, age, and type of injury.