Quynh Nguyen

Spine fractures in patients with ankylosing spinal disorders.

Study Design. Retrospective review. Objective. To describe the spine fracture characteristics, current treatments, and their results in patients with ankylosing spinal disorders (ASD), such as ankylosing spondylitis (AS) and diffuse idiopathic skeletal hyperostosis (DISH), with the hypothesis that complication and mortality rates are high. Summary of Background Data. Spine fractures in patients with ASD are unique and have only been described in relatively small case series. Methods. Retrospective review of a large consecutive series of patients with spine fractures and ASD over a 7-year period. Complications were stratified according to parameters such as type and number of comorbidities, patient age, and mechanism of injury. Predictors of mortality were analyzed by linear regression. Similarities between patients with AS and DISH were evaluated by &khgr;2 analysis. Results. Of the 122 spine fractures in 112 consecutive patients with ASD, the majority were transdiscal extension injuries, most commonly affecting C6–C7. Eighty-one percent of the patients had at least 1 major medical comorbidity. Spinal cord injury was present in 58% of the patients, 34% of whom improved by at least 1 American Spinal Injury Association grade. Nineteen percent of patients had delayed diagnosis of their spine fracture, 81% of whom had resulting neurologic compromise. Surgery was performed on 67% of patients, consisting primarily of multilevel posterior instrumentation 3 levels above and below the injury. Eighty-four percent of all patients had at least 1 complication. Mortality was 32% and correlated with age ≥70 (P < 0.0001), number of comorbidities (P < 0.0001), and low-energy mechanism of injury (P = 0.009). AS patients were younger (P = 0.03) and had a higher risk of delayed fracture diagnosis (P = 0.012), but were otherwise similar to DISH patients. Conclusion. Patients with spine fractures and ASD are at high risk for complications and death and should be counseled accordingly. Multilevel posterior segmental instrumentation allows effective fracture healing. AS and DISH patients represent similar patient populations for the purpose of treatment and future research.

Posterior C2 instrumentation: accuracy and complications associated with four techniques.

Study Design. Retrospective review of a single tertiary care spine database to identify patients with C2 instrumentation between January 2001 and September 2008. Objective. (1) Evaluate a large series of posterior C2 screws to determine accuracy by computed tomography (CT) scan, (2) assess dimensions of “safe bony windows” with CT, and (3) assess perioperative complication rate related to errant screw placement. Summary of Background Data. The variable C2 anatomy can make instrumentation challenging and prone to potentially severe complications. New techniques have expanded available options. Methods. Clinical data were obtained from the medical record. Radiographic analyses included preoperative and postoperative CT scans to quantify the patients’ bone and to classify accuracy of instrumentation. Screws were graded using the following definitions: Type I: Screw threads completely within the bone.Type II: Less than (1/2) the diameter of the screw violates the surrounding cortex.Type III: Clear violation of transverse foramen or spinal canal. Results. Seven hundred and thirty-six screws in 383 patients were identified. Fifty-five patients were excluded because of lack of data leaving 328 patients (188 male patients, 140 female patients) with 633 screws. Three hundred and thirty-nine pedicle, 154 transarticular, 63 laminar, and 77 short pars screws were placed, and of the 509 screws with postoperative CT scans, accuracy rates (Types I and II) were 98.8%, 98.5%, 100%, and 94.6%, respectively. Eight were unacceptably placed: two medially and six encroaching on the vertebral artery foramen. One patient had a vertebral artery occlusion and another had a dissection. There were no neurologic injuries. Mean CT measurements of pedicle height, axial width, and laminar width were 8.1, 5.8, and 5.7 mm respectively, with males having significantly larger pedicle height (P < 0.001), pedicle width (P < 0.001), and laminar width (P < 0.022). Conclusion. We show a lower than previously reported incidence of complications associated with posterior C2 screw placement. The multiple techniques of posterior C2 fixation available allow for flexibility in determining ideal technique.

Unilateral C-1 lateral mass sagittal split fracture: an unstable Jefferson fracture variant.

OBJECT The object of this study was to describe an unusual fracture subtype within C-1 injuries with a propensity to result in late deformity and pain. Most patients with C-1 injuries are nonsurgically treated using external immobilization unless there is an injury of the transverse atlantal ligament. The authors describe an unusual variant involving a unilateral sagittal split with a high tendency to late deformity and pain. They also review the literature and treatment of C-1 fractures. METHODS A retrospective review of 12,671 CT scans from a Level I trauma center over a 6-year period yielded 54 patients with C-1 fractures. Among these patients, 6 had an unusual unilateral lateral mass sagittal split, which resulted in a late cock-robin deformity in all survivors and thus a surgical deformity correction with occipital-cervical instrumented fusions. Patient charts and radiographs were reviewed, this fracture subtype is described, and its treatment discussed. RESULTS Radiographic studies in 6 patients with C-1 fractures demonstrated a unilateral sagittal split of the lateral mass but an intact transverse atlantal ligament. In the 3 surviving patients, a late cock-robin deformity, significant loss of neck rotation, and severe neck pain developed. Vertebral artery occlusion, as revealed on CT angiography, occurred in 1 patient. All patients were placed in traction and underwent successful occipital-cervical fusion and deformity correction. At the final follow-up, all patients had satisfactory pain relief and improved head alignment. CONCLUSIONS Patients with a unilateral sagittal split of the C-1 lateral mass have unstable injuries and must be carefully monitored, with a low threshold for surgical reconstruction or prolonged traction. Patients with late deformity can be successfully treated with occipital-cervical instrumented fusions.

Vertebral artery anomalies at the craniovertebral junction in the US population.

Study Design. Retrospective review. Objective. To evaluate the prevalence of anatomical variations of the vertebral artery at the craniovertebral junction and the posterior arch of the atlas in the US population. Summary of Background Data. Recent studies from Asia have reported a 5% to 10% prevalence of a persistent first intersegmental vertebral artery and 1% to 2% prevalence of a fenestrated artery. These anomalous vertebral artery courses lie directly over the starting point for atlas lateral mass screw insertion. The relatively high reported prevalence of these anomalies suggests that routine preoperative computed tomographic angiogram be considered prior to upper cervical fixation. We have not observed this anomaly as commonly as reported. Methods. The authors analyzed the records of 975 patients from a level I trauma center and adjacent university hospital who underwent computed tomographic angiography to evaluate the incidence of anomalous variations in the third segment of the vertebral artery. These results were compared with similar studies performed in Korea and Japan. Results. The mean age of the patients was 52.9 years. The ethnic distribution of the patients was as follows: 69.3% of the patients were Caucasian, 11% Asian, 10.8% African American, and 6% Hispanic. The prevalence of a persistent intersegmental artery was 0.01% (1/975); a fenestrated vertebral artery was 0.01% (1/975); and origin of a posterior inferior cerebellar artery was 0.4% (4/975). The incidence of these anomalies was significantly lower than those previously published from Korea and Japan. Conclusion. Vertebral artery course anomalies in the upper cervical spine were rare (0.42%) in our patient population. This finding contrasts with recent published reports from Asia, citing as high as a 10% rate of vertebral artery presence over the starting point for C1 lateral mass screw insertion. On the basis of the infrequent occurrence of this anomaly, we do not recommend routine computed tomographic angiography when planning upper cervical instrumentation. Level of Evidence: N/A

Partial rescue of growth failure in Growth Hormone (GH)-deficient mice by a single injection of a double-stranded adeno-associated viral vector expressing the GH gene driven by a muscle-specific regulatory cassette

Growth hormone (GH) deficiency (GHD) causes somatic growth impairment. GH has a short half-life and therefore it must be administered by daily subcutaneous injections. Adeno-associated viral (AAV) vectors have been used to deliver genes to animals, and double-stranded AAV (dsAAV) vectors provide widespread and stable transgene expression. In the present study we tested whether an intramuscular injection of dsAAV vector expressing GH under the control of a muscle creatine kinase regulatory cassette would ensure sufficient systemic GH delivery in conjunction with muscle-specific expression. Virus-injected GHD mice showed a significant (p < 0.05) increase in body length and body weight, without reaching full normalization, and significant (p < 0.05) reduction in absolute and relative visceral fat. Quantitative RT-PCR showed preferential GH expression in skeletal muscles that was confirmed by qualitative fluorescence analysis in mice injected with a similar virus expressing green fluorescent protein. The present study shows that systemic GH delivery to GHD animals is possible via a single intramuscular injection of dsAAV carrying a muscle-specific GH-expressing regulatory cassette.

A retrospective review of fixation of C1 ring fractures--does the transverse atlantal ligament (TAL) really matter?

BACKGROUND CONTEXT In contrast to the majority of outcome data, many consider C1 fractures to be benign injuries and so have advocated for conservative management, except in the case of concomitant transverse atlantal ligament (TAL) injury where C1-C2 or occiput-C2 fusions are recommended. PURPOSE Our goal was to evaluate a series of unstable C1 fractures treated with C1 open reduction and internal fixation (ORIF) to assess clinical and radiographic outcomes by determining the success of reduction and pain relief. STUDY DESIGN/SETTING This is a retrospective cohort review. PATIENT SAMPLE The sample includes adult patients with unstable C1 fractures treated with open reduction and primary internal fixation. OUTCOME MEASURES Primary outcome measures included visual analog pain scale (VAS), radiographic reduction (lateral mass displacement), maintenance of reduction, C1-C2 instability, and complications. METHODS A retrospective review of all patients with C1 fractures between September 2002 and September 2013 identified 12 consecutive patients from a level I trauma center who were treated with primary internal fixation without fusion. Electronic medical records and preoperative and postoperative radiographs were reviewed. The surgical technique consisted of a posterior cervical approach to the C1 arch and open reduction using bilateral C1 lateral mass screws connected transversely with a rod. Pre- and postoperative computed tomography scans were used to assess reduction. Long-term follow-up flexion and extension radiographs were used to assess C1-C2 stability. The authors did not receive relevant funding in relation to this research. RESULTS Twelve patients underwent C1 ORIF, with a mean age of 43 (9 males and 3 females) and a mean follow-up of 17 months. Transverse atlantal ligament was found to be disrupted with type I or type II injury in 11 of the 12 patients: 5 type I and 6 type II. Preoperative lateral mass displacement averaged 7.1 mm, with postoperative displacement after reduction averaging 2.4 mm (p-value <.001). The VAS score averaged 0.7 at latest follow-up. No patients went on to develop C1-C2 instability on final flexion-extension films. No patients had a complication that resulted in neurologic deficit or vascular injury associated with the procedure. No patients were found to have late sequelae of malunion or loss of reduction. Two surgically related complications occurred, namely one patient with errant screw requiring return to the operating room (OR) and one with arthrosis of the occipital-C1 joint. CONCLUSIONS Although a small series, early evidence suggests that patients with unstable C1 ring fractures can be successfully managed with primary ORIF. Open reduction and internal fixation results in a stable construct that maintains reduction, results in excellent pain control, and does not lead to C1-C2 instability. In our series, we have not observed the presence of TAL injury to adversely affect outcomes, and thus do not believe it is a contraindication to ORIF. Comparative studies comparing internal fixation with non-operative, C1-C2, or occiput-C2 fusions would yield more insight into optimal treatment options for these fractures.

A Case of Tophaceous Gout in the Lumbar Spine: A Review of the Literature and Treatment Recommendations

Study Design Case report. Objective The objective of this study is to report the occurrence of tophaceous gout in the lumbar spine. Methods Using a case report to illustrate the key points of gout in the spine, we provide a brief review of gout in the literature as it relates to its orthopedic and spinal manifestations as well as guidelines for management. Results This case report details the occurrence of a large and clinically significant finding of tophaceous gout in the lumbar spine in a 24-year-old man with a known history of gout and a 3-year history of progressive back pain. Conclusion A high index of suspicion can assist in diagnosis of patients presenting with back pain or neurologic findings with a history of gout. A previous history of gout (especially the presence of tophi), hyperuricemia, and the radiological characteristics presented here should aid the clinician in making the diagnosis of spinal gout. Early diagnosis has the potential to prevent the need for surgical intervention.

Emergency radiology and mass casualty incidents-report of a mass casualty incident at a level 1 trauma center.

The aims of this article are to describe the events of a recent mass casualty incident (MCI) at our level 1 trauma center and to describe the radiology response to the event. We also describe the findings and recommendations of our radiology department after-action review. An MCI activation was triggered after an amphibious military vehicle, repurposed for tourist activities, carrying 37 passengers, collided with a charter bus carrying 45 passengers on a busy highway bridge in Seattle, WA, USA. There were 4 deaths at the scene, and 51 patients were transferred to local hospitals following prehospital scene triage. Nineteen patients were transferred to our level 1 trauma center. Eighteen casualties arrived within 72 min. Sixteen arrived within 1 h of the first patient arrival, and 1 casualty was transferred 3 h later having initially been assessed at another hospital. Eighteen casualties (94.7 %) underwent diagnostic imaging in the emergency department. Of these 18 casualties, 15 had a trauma series (portable chest x-ray and x-ray of pelvis). Whole-body trauma computed tomography scans (WBCT) were performed on 15 casualties (78.9 %), 12 were immediate and performed during the initial active phase of the MCI, and 3 WBCTs were delayed. The initial 12 WBCTs were completed in 101 min. The mean number of radiographic studies performed per patient was 3 (range 1–8), and the total number of injuries detected was 88. The surge in imaging requirements during an MCI can be significant and exceed normal operating capacity. This report of our radiology experience during a recent MCI and subsequent after-action review serves to provide an example of how radiology capacity and workflow functioned during an MCI, in order to provide emergency radiologists and response planners with practical recommendations for implementation in the event of a future MCI.

Unilateral C-1 lateral mass sagittal split fracture: an unstable Jefferson fracture variant: Clinical article

OBJECT The object of this study was to describe an unusual fracture subtype within C-1 injuries with a propensity to result in late deformity and pain. Most patients with C-1 injuries are nonsurgically treated using external immobilization unless there is an injury of the transverse atlantal ligament. The authors describe an unusual variant involving a unilateral sagittal split with a high tendency to late deformity and pain. They also review the literature and treatment of C-1 fractures. METHODS A retrospective review of 12,671 CT scans from a Level I trauma center over a 6-year period yielded 54 patients with C-1 fractures. Among these patients, 6 had an unusual unilateral lateral mass sagittal split, which resulted in a late cock-robin deformity in all survivors and thus a surgical deformity correction with occipital-cervical instrumented fusions. Patient charts and radiographs were reviewed, this fracture subtype is described, and its treatment discussed. RESULTS Radiographic studies in 6 patients with C-1 fractures demonstrated a unilateral sagittal split of the lateral mass but an intact transverse atlantal ligament. In the 3 surviving patients, a late cock-robin deformity, significant loss of neck rotation, and severe neck pain developed. Vertebral artery occlusion, as revealed on CT angiography, occurred in 1 patient. All patients were placed in traction and underwent successful occipital-cervical fusion and deformity correction. At the final follow-up, all patients had satisfactory pain relief and improved head alignment. CONCLUSIONS Patients with a unilateral sagittal split of the C-1 lateral mass have unstable injuries and must be carefully monitored, with a low threshold for surgical reconstruction or prolonged traction. Patients with late deformity can be successfully treated with occipital-cervical instrumented fusions.

380. Therapeutic Capacity of AAV-Delivered Muscle-Specific-Expressed Micro-Utrophin (ΔR4-R21/ΔCT) in mdX4cv Skeletal Muscles

Duchenne muscular dystrophy (DMD) is a severe muscle wasting disorder caused by dystrophin mutations. Utrophin is a dystrophin paralogue that can prevent necrosis in the mdx mouse DMD model. We designed an expression plasmid containing a miniaturized M-creatine kinase regulatory cassette (CK8e) and a rationally designed micro-utrophinΔR4-21/ΔCT (µUtrn) to accommodate the limited capacity of recombinant adeno-associated virus (rAAV). Both intramuscular (IM) and intravascular (IV) delivery of rAAV6-CK8-µUtrn at 2 weeks of age profoundly mitigated the dystrophic phenotype in skeletal muscles when examined at 3-6 months of age. These improvements were observed in many but not all skeletal muscle histological and functional parameters. At a pathological level µUtrn production was associated with significant reductions in centrally nucleated muscle fibers and with a greatly reduced prevalence of muscle regions containing inflammatory cells. µUtrn production also restored dystrophin-glycoprotein-complex (DGC) components β-Dystroglycan, Δ-Sarcoglycan, α-Dystrobrevin-2, and α1-Syntrophin to the sarcolemma. As expected, nNOS was not restored, presumably because CK8-µUtrn lacks direct nNOS binding sites. Analysis of µUtrn immunostaining intensities 3-months post-treatment suggested lower µUtrn levels in many of the 1, 2a and 2d/x fibers than in the 2b fibers. These differences would be consistent with the relative transcriptional activities of the CK8e regulatory cassette in different adult mouse fiber types: 2b > 2d/x > 2a > 1. Given the important structural role of costameres in connecting the sarcolemma to sarcomeres, we examined utrophin and µUtrn localization patterns and found endogenous utrophin localized in a costameric pattern adjacent to Z-line end points while abutting sarcolemma junctions. However, while µUtrn was also associated with a costameric lattice, its striations were unexpectedly only ~0.8 µm apart compared to ~2.2 µm for endogenous utrophin in untreated mdx4cv muscles. How the presence of two different costameric lattice patterns may affect skeletal muscle function is not known. Since mdx4cv mice are known to exhibit a fragmented synaptic phenotype, we also examined neuromuscular junctions (NMJs) in treated and untreated mice and found that µUtrn prevented synapse fragmentation and also restored the depth of synaptic folds. Interestingly, the NMJs in µUtrn-treated muscles exhibited a more highly branched architecture of the synaptic folds, and this may have compensated for the reduced number of fold openings observed in untreated mice. µUtrn treatment also provided partial restoration of the reduced Achilles myotendinous junction folds seen in mdx4cv mice, and did not lead to either the myotendinous strain injury or the ringed fiber formation associated with micro-dystrophinΔR4-R23/ΔCT mediated therapy. Importantly, physiological studies indicated that IM treated tibialis anterior muscles maintained peak force production and exhibited partially improved specific force production. Overall, rAAV6-CK8-µUtrn treatment of mdx4cv mice provided major improvements in many muscle parameters. However, it did not overcome all dystrophic deficits, and it modified the normal costameric lattice structure. Further improvements might be achieved by expressing µUtrn via regulatory cassettes with higher relative activity in 1, 2a and 2d/x fibers, and by further modifications of µUtrn (ΔR4-R21/ΔCT)s design.