Vertebral artery injuries in cervical spine surgery

Background contextVertebral artery injuries (VAIs) are rare but serious complications of cervical spine surgery, with the potential to cause catastrophic bleeding, permanent neurologic impairment, and even death. The present literature regarding incidence of this complication largely comprises a single surgeon or small multicenter case series.PurposeWe sought to gather a large sample of high-volume surgeons to adequately characterize the incidence and risk factors for VAI, management strategies used, and patient outcomes after VAI.Study designThe study was constructed as a cross-sectional study comprising all cervical spine patients operated on by the members of the international Cervical Spine Research Society (CSRS).Patient sampleAll patients who have undergone cervical spine surgery by a current member of CSRS as of the spring of 2012.Outcome measuresFor each surgeon surveyed, we collected self-reported measures to include the number of cervical cases performed in the surgeon's career, the number of VAIs encountered, the stage of the case during which the injury occurred, the management strategies used, and the overall patient outcome after injury.MethodsAn anonymous 10-question web-based survey was distributed to the members of the CSRS. Statistical analysis was performed using Student t tests for numerical outcomes and chi-squared analysis for categorical variables.ResultsOne hundred forty-one CSRS members (of 195 total, 72%) responded to the survey, accounting for a total of 163,324 cervical spine surgeries performed. The overall incidence of VAI was 0.07% (111/163,324). Posterior instrumentation of the upper cervical spine (32.4%), anterior corpectomy (23.4%), and posterior exposure of the cervical spine (11.7%) were the most common stages of the case to result in an injury to the vertebral artery. Discectomy (9%) and anterior exposure of the spine (7.2%) were also common time points for an arterial injury. One-fifth (22/111) of all VAI involved an anomalous course of the vertebral artery. The most common management of VAI was by direct tamponade. The outcomes of VAIs included no permanent sequelae in 90% of patients, permanent neurologic sequelae in 5.5%, and death in 4.5%. Surgeons at academic and private centers had nearly identical rates of VAIs. However, surgeons who had performed 300 or fewer cervical spine surgeries in their career had a VAI incidence of 0.33% compared with 0.06% in those with greater than 300 lifetime cases (p=.028).ConclusionsThe overall incidence of VAI during cervical spine surgery reported from this survey was 0.07%. Less experienced surgeons had a higher rate of VAI compared with their more experienced peers. The results of VAI are highly variable, resulting in no permanent harm most of the time; however, permanent neurologic injury or death occur in 10% of cases.     

The development of a dynamic,six-axis spine simulator

Background contextAlthough a great deal of research has been completed to characterize the stiffness of spinal specimens, there remains a limited understanding of the spine in 6 df and there is a lack of data from dynamic testing in six axes.PurposeThis study details the development and validation of a dynamic six-axis spine simulator.Study designBiomechanical study.MethodsA synthetic spinal specimen was used for the purpose of tuning the simulator, completing positional accuracy tests, and measuring frequency response under physiological conditions. The spine simulator was used to complete stiffness matrix tests of an L3–L4 lumbar porcine functional spinal unit. Five testing frequencies were used, ranging from quasistatic (0.00575 Hz) to dynamic (0.5 Hz). Tests were performed without an axial preload and with an axial preload of 500 N.ResultsThe validation tests demonstrated that the simulator is capable of producing accurate positioning under loading at frequencies up to 0.5 Hz using both sine and triangle waveforms. The porcine stiffness matrix tests demonstrated that the stiffness matrix is not symmetrical about the principal stiffness diagonal. It was also shown that while an increase in test frequency generally increased the principal stiffness terms, axial preload had a much greater effect.ConclusionsThe spine simulator is capable of characterizing the dynamic biomechanics of the spine in six axes and provides a means to better understand the complex behavior of the spine under physiological conditions.     

No difference in postoperative complications,pain, and functional outcomes up to 2 years after incidental durotomy in lumbar spinal fusion: a prospective,multi-institutional,propensity-matched analysis of 1,741 patients

BackgroundIncidental durotomies occur in up to 17% of spinal operations. Controversy exists regarding the short- and long-term consequences of durotomies.PurposeThe primary aim of this study was to assess the effect of incidental durotomies on the immediate postoperative complications and patient-reported outcome measures.Study designProspective study.Patient sampleA total of 1,741 patients undergoing index lumbar spine fusion were selected from a multi-institutional prospective data registry.Outcome measuresPatient-reported outcome measures used in this study included back pain (BP-Visual Analog Scale), leg pain (LP-Visual Analog Scale), and Oswestry Disability Index.MethodsA total of 1,741 patients were selected from a multi-institutional prospective data registry, who underwent primary lumbar fusion for low back pain and/or radiculopathy between January 2003 and December 2010. We collected and analyzed data on patient demographics, postoperative complications, back pain, leg pain, and functional disability over 2 years, with risk-adjusted propensity score modeling.ResultsIncidental durotomies occurred in 70 patients (4%). Compared with the control group (n=1,671), there was no significant difference in postoperative infection (p=.32), need for reoperation (p=.85), or symptomatic neurologic damage (p=.66). At 1- and 2-year follow-up, there was no difference in patient-reported outcomes of back pain (BP-Visual Analog Scale), leg pain (LP-Visual Analog Scale), or functional disability (Oswestry Disability Index) (p>.3), with results remaining consistent in the propensity-matched cohort analysis (p>.4).ConclusionWithin the context of an on-going debate on the consequences of incidental durotomy, we found no difference in neurologic symptoms, infection, reoperation, back pain, leg pain, or functional disability over a 2-year follow-up period.     

Preliminary results of Zenith Fenestrated abdominal aortic aneurysm endovascular grafts

Background

Patients with juxtarenal aortic aneurysms who are unfit for open repair may be considered for fenestrated endovascular repair (fenEVAR). We report our initial experience with fenEVAR.

Methods

We reviewed the data on all our patients receiving fenEVAR for juxtarenal aortic aneurysms.

Results

Eight patients, average age 75 years, underwent fenEVAR. Endografts were designed from details obtained from preoperative computed tomography angiography. There were 6 grafts with superior mesenteric scallops and bilateral renal fenestrations, 1 with bilateral renal scallops, and 1 with a single renal fenestration. All patients survived 30 days. There was no renal failure requiring dialysis. At 10 weeks, 1 patient died from acute intestinal ischemia and multisystem organ failure, and another died from respiratory failure.

Conclusions

It is feasible to offer fenEVAR to patients who are poor candidates for open repair. However, these procedures are technically challenging. Early outcomes are less favorable than other aortic endovascular procedures.     

Expression of Phosphofructokinase in Skeletal Muscle Is Influenced by Genetic Variation and Associated With Insulin Sensitivity

Using an integrative approach in which genetic variation, gene expression, and clinical phenotypes are assessed in relevant tissues may help functionally characterize the contribution of genetics to disease susceptibility. We sought to identify genetic variation influencing skeletal muscle gene expression (expression quantitative trait loci [eQTLs]) as well as expression associated with measures of insulin sensitivity. We investigated associations of 3,799,401 genetic variants in expression of >7,000 genes from three cohorts (n = 104). We identified 287 genes with cis-acting eQTLs (false discovery rate [FDR] <5%; P < 1.96 × 10⁻⁵) and 49 expression–insulin sensitivity phenotype associations (i.e., fasting insulin, homeostasis model assessment–insulin resistance, and BMI) (FDR <5%; P = 1.34 × 10⁻⁴). One of these associations, fasting insulin/phosphofructokinase (PFKM), overlaps with an eQTL. Furthermore, the expression of PFKM, a rate-limiting enzyme in glycolysis, was nominally associated with glucose uptake in skeletal muscle (P = 0.026; n = 42) and overexpressed (Bonferroni-corrected P = 0.03) in skeletal muscle of patients with T2D (n = 102) compared with normoglycemic controls (n = 87). The PFKM eQTL (rs4547172; P = 7.69 × 10⁻⁶) was nominally associated with glucose uptake, glucose oxidation rate, intramuscular triglyceride content, and metabolic flexibility (P = 0.016–0.048; n = 178). We explored eQTL results using published data from genome-wide association studies (DIAGRAM and MAGIC), and a proxy for the PFKM eQTL (rs11168327; r² = 0.75) was nominally associated with T2D (DIAGRAM P = 2.7 × 10⁻³). Taken together, our analysis highlights PFKM as a potential regulator of skeletal muscle insulin sensitivity.