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.

A pictorial classification atlas of cement extravasation with vertebral augmentation.

BACKGROUND CONTEXT: Minimally invasive procedures for the treatment of vertebral compression fractures (VCFs) have been in use since the mid-1980s. A mixture of liquid monomer and powder is introduced through a needle into one or both pedicles, and it polymerizes within the vertebral body in an exothermic chemical reaction. The interaction between cement and the fractured vertebral body determines whether and how the cement stabilizes the fragments, alters morphology, and extravasates. The cement is intended to remain within the vertebral body. However, some studies have reported cement leakage in more than 80% of the procedures. Although cement leakage can have no or minimal clinical consequences, adverse events, such as paraplegia, spinal cord and nerve root compression, cement pulmonary embolisms, or death, can occur. The details of how the cement infiltrates a vertebral body or extravasates out of the body are poorly understood and may help to identify strategies to reduce complications and improve clinical efficacy. PURPOSE: Apply novel techniques to demonstrate the cement spread inside vertebrae as well as the points and pattern of cement extravastation. STUDY DESIGN: Ex vivo assessment of vertebral augmentation procedures. METHODS: Vertebrae from six fresh whole human cadaver spines were used to create 24 specimens of three vertebrae each. The specimens were placed in a pneumatic testing system, designed to create controlled anterior wedge compression fractures. Unipedicular augmentation was performed on the central vertebra of 24 specimens using polymethylmethacrylate/barium sulfate Vertebroplastic cements (DePuy Spine, Raynham, MA, USA). The volume of cement injected into each vertebra was recorded. Fine-cut computed tomography (CT) scans of all segments were obtained (Brilliance 64; Philips Medical Imaging, Amsterdam, The Netherlands). Using multiplanar reconstructions and volume compositing three-dimensional imaging (Osirix, www.osirix-viewer.com), each specimen was carefully assessed for cement extravasation. Specimens were then immersed in a 50% sodium hypochlorite solution until all overlying soft tissues were removed, leaving the bone and cement intact. The specimens were dried and visually examined and photographed to assess cement extravasation and fracture patterns. Specimens were cut in the axial or sagittal plains to assess the gross morphology of cement infiltration and extravasation. Finally, 25-mm block sections were removed from selected specimens and imaged at 14-µm resolution using a GE Locus-SP micro-CT system (GE Healthcare, London, Ontario, Canada). RESULTS: Infiltration was characterized by an intimate capture of trabecular bone within the cement, forming an irregular border at the perimeter of the cement that is determined by the morphology of the trabeculae and marrow spaces. Extravasation of the cement was assessed as "any" if any small or large amount of extravastation was detected and was also assessed as severe if a large amount of extravasation was found. Out of the 23 levels studied, some extravasation was visibly apparent in all levels. A wide spectrum of filling patterns, leakage points, and interdigitation of the cement was observed and appeared to be determined by the interaction of the cement with the trabecular morphology. The results support the fact that the cement generally advances through the vertebrae with relatively regular and easily identifiable borders. CONCLUSIONS: Using a cadaver VCF model, this study demonstrated the exact filling and extravastation patterns of bone cement inside and out of fractured vertebrae. These data enhance our understanding of the vertebral augmentation and extravastation mechanics.

The association of occipitocervical dissociation and death as a result of blunt trauma.

BACKGROUND CONTEXT: Despite multiple reports of survivability, dissociative occipitocervical injury (OCI) is generally accepted to be fatal in most cases. The actual number of trauma victims where OCI may have made the difference between life and death is unknown because multiple studies have shown that these injuries can be missed with current diagnostic methods. An improved understanding of the relative importance of OCI in blunt trauma mortality may help to refine protocols for the assessment and treatment of patients who arrive alive to the emergency room after severe blunt trauma. One way to improve our understanding is to document the relative frequency OCI relative to brain, liver, aorta, and spleen injuries in blunt trauma fatalities. PURPOSE: In this study, we aimed to glean a more accurate estimate of the absolute and relative incidence of OCI after death from blunt trauma via a systematic review of data reported in the forensic literature. STUDY DESIGN: Systematic literature review. METHODS: A systematic literature search and review were undertaken. The search aimed to answer three primary questions: What is the true incidence of cervical spine injuries in blunt trauma fatalities? What is the incidence of dissociative OCIs specifically? and What is the incidence of these injuries relative to other common injuries associated with blunt trauma fatalities (central nervous system, spleen, liver, etc)? For that, two search protocols were used and included postmortem studies of blunt trauma mechanism in adult population. RESULTS: The mean reported incidence of cervical spine injuries was 49.7% in blunt trauma fatalities. Dissociative OCIs were found to have a mean incidence of 18.1%. The relative frequencies of injuries were 49.7% for cervical spine, 41.8% for central nervous system, 20.8% for liver, 11.2% for spleen, and 10.8% for aorta. CONCLUSIONS: In this systematic literature review, cervical spine injuries were found to be the most commonly reported finding associated with blunt trauma fatalities, occurring in nearly 50% of cases with occipitocervical dissociation accounting for nearly 20%. Older pathologic studies suggested a lesser overall and relative frequency and may have underestimated their incidence. Typically, these blunt cervical spine injuries were much more commonly found to disrupt the soft tissue stabilizing restraints (ligaments, facet capsules, etc) as opposed to causing bony fractures and, accordingly, were often not detected on plain radiographs. It is likely that the frequency of this injury is underestimated in patients surviving severe blunt trauma, placing them at risk for death from an occult source in the postinjury period. Additional research is needed to determine if improved methods to diagnose OCI and improved patient management protocols to protect against secondary injuries might reduce mortality in blunt trauma victims.

Reference data for assessing widening between spinous processes in the cervical spine and the responsiveness of these measures to detecting abnormalities.

BACKGROUND CONTEXT: Traumatic injury to the spine is evaluated and treated based on the perceived stability of the spine. Recent classification schemes have established the importance of evaluating the discoligamentous complex to fully comprehend stability. There are a variety of techniques to evaluate the discoligamentous complex, including assessment of interspinous distance. However, there currently are no clinically validated methods to define and assess abnormal interspinous widening. PURPOSE: The purpose of the study was to provide reference data and evidence to support the objective use of spinous process widening in the diagnosis of cervical spine injury and instability. STUDY DESIGN: The study was designed to be biomechanical and observational. METHODS: Distances between spinous processes were measured from lateral flexion-extension X-rays of 156 skeletally mature asymptomatic subjects who reported never having had neck symptoms as well as 12 whole human cadavers before and after creating increasingly severe damage to posterior structures. Cervical interspinous distances were measured and then normalized to the width of the C4 vertebral end plate. The change in the distance from flexion to extension was also calculated. RESULTS: Descriptive statistics, including the 95% confidence intervals for each cervical level were tabulated for 863 levels in 149 analyzable asymptomatic volunteers. In the simulated cadaver model, interspinous widening was highly specific and mildly sensitive for detecting damage to the posterior structures of the cervical spine. CONCLUSIONS: This study provides reference data that can be used to quantitatively assess interspinous process widening in the cervical spine. Application of the reference data to a cadaver model of cervical trauma suggests that although objective evidence of abnormal widening may be uncommon, when present, it is suggestive of extensive damage to the cervical spine. Derived from this data were two "rule of thumb" criteria to identify abnormal interspinous widening in flexion X-rays; when greater than 30% relative to an adjacent level (40% between C1-C2 and C2-C3) or greater than 50% of the anterior-posterior width of the C4 vertebral body (30% for C2-C3).

Infectious Collet-Sicard syndrome in the differential diagnosis of cerebrovascular accident: a case of head-to-neck dissociation with skull-based osteomyelitis.

BACKGROUND CONTEXT: Collet-Sicard syndrome (CSS) is a rare condition that includes palsies of cranial nerves IX, X, XI, and XII. There are multiple reported causes in the literature, although infection is particularly unusual. PURPOSE: To report an unusual case of CSS as a result of infection causing head-to-neck dissociation with involvement of the upper cervical spine. STUDY DESIGN: Case report. METHODS: A 56-year-old male with medical comorbidities developed a cranial-based infection secondary to initial incomplete treatment of otitis media. The mass effect of the infection resulted in multiple cranial nerve palsies and extremity symptoms initially confused with a cerebrovascular accident. Clinical course of the patient and a review of CSS are presented. RESULTS: With progression of the disease, further evaluation revealed a disseminated upper cervical and skull-based infection causing destructive head-to-neck infectious instability. This was treated with posterior occipitocervical debridement, fixation, and fusion and appropriate long-term antibiotics. Over the course of several months, the infection resolved and there was a significant improvement in his dysphagia, dysarthria, and hearing. CONCLUSIONS: Delay in diagnosis of CSS is common, and this syndrome should be considered in patients who present with a constellation of lower cranial nerve palsies. Early recognition and treatment should result in successful recovery, but even in cases of delayed detection, suitable intervention can result in substantial clinical improvement.

Internal decapitation: survival after head to neck dissociation injuries.

STUDY DESIGN: Case series. OBJECTIVE: To describe survival and outcomes after occipitocervical dissociation injuries. SUMMARY OF BACKGROUND DATA: Historically, occipitocervical dissociation injuries have a high rate of associated neurologic deficit with a relatively high incidence of mortality. METHODS: Six patients with occipitocervical dissociation injuries are reported and their management and imaging findings reviewed. Possible contributory factors for survival are discussed. RESULTS: All patients had upper neck and head dissociation injuries. The pattern of injury in all of these cases included a distraction type mechanism. All cases demonstrated soft tissue disruption in the zone of injury, which was consistent and apparent on all imaging studies. In these patients, the extent and severity of injury was more apparent on magnetic resonance imaging (MRI) than on radiograph or computed tomography scan. Management of these injuries included immobilization followed by surgery with particular care taken to avoid application of distraction forces to the neck. CONCLUSION: Patients with occipitocervical dissociation injuries may survive their injury and even retain neurologic integrity. Initial in-line head stabilization is emphasized to prevent catastrophic neurologic injury. The resting osseous relationships and vertebral alignment at the time of imaging evaluation may be deceivingly normal, and the damage often primarily or exclusively involves disruption of the perivertebral soft tissue structures. Prevertebral soft tissue swelling was apparent in all cases. For these injuries that involve primarily damage to the ligamentous structures, MRI seems to be the optimal test for revealing the magnitude of the injury.

[Pleomorphic carcinoma of the lung heralded as bilateral leg pain].

This is a case of a 70 year old male patient suffering from bilateral leg pain for 2 months. Physical examination disclosed clubbing. X-rays of the legs showed bilateral periosteal elevation with subperiosteal bone formation. 99TM-diphosphonate bone scan was negative. A search for malignancy revealed pleomorphic carcinoma of the right lung. Pain symptom disappeared 2 days after resection of the tumor. Repeated X-rays of the legs, three and a half months later showed no change and the clubbing persisted. Hence, unexplained bilateral leg pain should raise suspicion of hypertrophic osteoarthropathy, and elicit a search for secondary disease especially lung tumor. It is interesting to point out the negative bone scan and the rapid resolution of patient symptoms after resection of the tumor.

Biological and antigenic characterization of Netivot virus, an unusual new Orbivirus recovered from mosquitoes in Israel.

The antigenic and biological characteristics of a new Orbivirus, designated Netivot virus, are described. This agent was originally recovered in cultures of the C6/36 clone of Aedes albopictus cells from a pool of Culex pipiens captured in Israel. Netivot virus is not pathogenic for newborn mice, nor did it initially produce detectable cytopathic effect (CPE) in Vero cells. It is closely related antigenically to Umatilla and Llano Seco viruses; these 3 agents appear to constitute a new serogroup within the genus Orbivirus. Netivot virus is also more distantly related to a number of other orbiviruses in the blue-tongue, epizootic hemorrhagic disease of deer, and Eubenangee serogroups. Netivot virus replicated to high titer and produced CPE in a variety of mosquito cell cultures, but it did not grow in 2 sand fly cell lines. Inoculation of Ae. aegypti and Ae. albopictus with Netivot virus resulted in almost 100% mortality in both species within 15 days after infection. The recovery of this and a number of other yet unidentified viral agents from field-collected mosquitoes in cultures of C6/36 cells, but not in the conventional vertebrate assay systems, suggests the existence in nature of many yet unrecognized mosquito-associated viruses. It also demonstrates the value of using new isolation methods in arbovirus studies.

Isolation of viruses from mosquitoes of the Negev, Israel.

In a survey of the mosquito population of the Negev carried out between July 1982 and September 1984, over 85,000 insects belonging to 10 species were tested for the presence of viruses. They yielded 91 virus isolates in C-6/36 mosquito cell cultures; 20 of the isolates were recovered also in Vero cell cultures and in suckling mice inoculated intracerebrally. Of the 20 isolates recovered in the vertebrate systems 17 were identified as Sindbis, and three as West Nile viruses. 71 viruses which have been isolated only in mosquito cell cultures remain unidentified. Sindbis and West Nile arboviruses were isolated only from Culex pipiens and from Cx perexiguus, while the unidentified viruses were isolated from these and from five other mosquito species.

Adaptation of an Aedes aegypti mosquito cell line to growth at 15 degrees C and its response to infection by Sindbis virus.

Aedes aegypti mosquito cells, usually cultured at 28 to 30 degrees C, were adapted to grow at 15 degrees C. They were designated A. aegypti (c) cells, and had an estimated doubling time of 10 days. Sindbis virus (SV) replicated in these cells to peak titres of over 1.0 x 10(9) p.f.u./ml 8 to 10 days after inoculation. These, or about 10-fold lower titres, continued to be produced over a 130 day test period without causing visible cell damage. Continuous virus proliferation and the yield of uniformly large plaque forming progeny viruses are the two most important features which differentiate infection with this virus in A. aegypti (c) cells from that of A. aegypti cells grown at 28 degrees C (Peleg & Stollar, 1974). Absence of homologous interference vis-à-vis cell-virus coexistence suggests that homologous interference is not a prerequisite for maintaining cell-virus coexistence. Preinoculation of A. aegypti (c) cultures with a small plaque forming Sindbis virus (SV-S) leads, under certain conditions, to the establishment of homologous interference.

The significance and nature of defective interfering viruses.

Deletions in viral genomes appear to be a common occurrence in the replication of all DNA and RNA viruses which have been adequately studied. Such defective genomes can replicate in the presence in the same cell of a helper virus as long as the deletion does not involve the initiation site for genome replication. Coinfection of a cell with defective and "normal" infectious virus leads to reduction in the yield of the latter. The nature of DI viruses and genomes found in Sindbis virus-infected vertebrate cells during "undiluted passage" series is discussed. This procedure leads to the accumulation of progressively shorter viral RNA genomes with internal deletions. The enrichment is limited to genome lengths which are integral fractions (1/2, 1/3, 1/4, etc.) of the complete genome, and these are also found in viral particles released at the corresponding passage levels. It is believed that the selective accumulation of these fragments is governed by constraints of assembly which demand that one full genome equivalent be packaged in a released particle. In contrast to vertebrate cells, cultured mosquito cells do not seem to produce or "recognize" DI particles. Possible implications for the epidemiology of arthropod-transmitted alphaviruses are presented.

In vivo behavior of a Sindbis virus mutant isolated from persistently infected Aedes aegypti cell cultures.

A mutant of the Sindbis virus SV-S was found to interfere with the regular course of infection by the wild strain of the virus SV-W in A. aegypti mosquitoes and in suckling mice. In mosquitoes, this result was manifested by a reduced titer of SV-W in the presence of SV-S and by a failure of the mosquitoes to transmit SV-W. In the brains of suckling mice, in the presence of SV-S, the growth of sc inoculated SV-W was suppressed, and as a result, the usually lethal course of infection by this virus was converted into a nonlethal one.