Preliminary experience with a novel facet-based lateral mass drill guide for the placement of lateral mass screws compared to freehand technique: a cadaveric study.

BACKGROUND CONTEXT: Lateral mass screw fixation is the standard for posterior subaxial cervical fixation. Several freehand surgical techniques for placing lateral mass screws have been described which rely on anatomical landmarks and surgeon mastery of the technique to safely place screws. The accuracy of these freehand techniques is inherently variable and can be influenced by a surgeon's level of clinical experience. A novel technique was developed that utilizes the plane of the facet joint to create lateral mass screw pilot holes parallel with the joint line to improve the safety and accuracy of lateral mass screw placement regardless of experience. PURPOSE: To assess the safety and accuracy of lateral mass screw placement using a novel lateral mass drill guide instrument (LM Guide), compared to standard freehand technique. STUDY DESIGN: Randomized cadaveric study utilizing multiple surgeon evaluators to compare the safety and accuracy of guided cervical lateral mass placement compared to traditional freehand techniques. MATERIALS AND METHODS: Lateral mass screws were placed from C3 to C7 in 20 cadaver specimens by 8 spine surgeons of varying levels of clinical experience (4 attendings, 4 fellows). Screws were placed bilaterally using standard anatomic landmarks ("freehand") randomly allocated on one side and using the LM Guide on the other. Cadaveric specimens were imaged with high-resolution CT to assess screw placement. Zone grading for safety was conducted based on screw tip position and clinical severity of screw breach was based on proximity to surrounding neurovascular anatomy. Screws were graded as safe, at-risk, or critical, with at-risk and critical screws considered malpositioned. To assess the accuracy of screw trajectory placed using the LM Guide compared to freehand, sagittal screw angle was measured and compared to an "ideal" screw path parallel to the facet joint line. Freehand and LM Guide groups were compared using Pearson's chi-square correlation. RESULTS: Screw placement using the LM guide yielded a significantly lower rate of screw malpositioning, with 7 of 91 (7.7%) compared with 18 of 99 (18.2%) screws placed in the At-Risk or Critical Zones, p<.05. Of the 91 screws inserted using the LM Guide, 84 (92.3%) were in the Safe Zone, 7 (7.7%) were At-Risk, and 0 were in Critical zones. There was no incidence of neural or transverse foramen breaches with the LM Guide. In comparison, for the 99 screws inserted freehand, 81 (81.8%) were Safe, 14 (14.1%) were At-Risk, and 4 (4.1%) were in Critical zones. The 4 Critical zone freehand screw breaches included 1 neural foramen breach, 2 transverse foramen breaches, and 1 facet breach. The LM Guide also resulted in higher accuracy of screw trajectory, as indicated by a significant reduction in sagittal screw angle compared with freehand, p<.01. Notably, in the less-experienced surgeon cohort, the LM Guide significantly reduced the sagittal screw angle and resulted in no critical screw breaches compared to 3 critical breaches with freehand technique suggesting there might be a benefit in decreasing the learning curve associated with lateral mass screw placement. CONCLUSIONS: Lateral mass screw placement with a novel LM Guide that uses the facet joint to control screw trajectory improved the accuracy and reproducibility of screw placement with a significant reduction in screw breach rate and sagittal screw angle compared to freehand techniques regardless of surgeon experience level. CLINICAL SIGNIFICANCE: The inherent variability of freehand lateral mass screw placement can increase the risk of clinical complications associated with screw malpositioning. The technique presented in this cadaveric study may be a viable alternative to standard freehand technique that can improve the overall safety of lateral mass screw placement.

Publisher Correction: Mitochondrial DNA copy number is associated with psychosis severity and anti-psychotic treatment.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Mitochondrial DNA copy number is associated with psychosis severity and anti-psychotic treatment.

Mitochondrial pathology has been implicated in the pathogenesis of psychotic disorders. A few studies have proposed reduced leukocyte mitochondrial DNA (mtDNA) copy number in schizophrenia and bipolar disorder type I, compared to healthy controls. However, it is unknown if mtDNA copy number alteration is driven by psychosis, comorbidity or treatment. Whole blood mtDNA copy number was determined in 594 psychosis patients and corrected for platelet to leukocyte count ratio (mtDNAcnres). The dependence of mtDNAcnres on clinical profile, metabolic comorbidity and antipsychotic drug exposure was assessed. mtDNAcnres was reduced with age (ß = -0.210, p < 0.001), use of clozapine (ß = -0.110,p = 0.012) and risperidone (ß = -0.109,p = 0.014), dependent on prescribed dosage (p = 0.006 and p = 0.026, respectively), and the proportion of life on treatment (p = 0.006). Clozapine (p = 0.0005) and risperidone (p = 0.0126) had a reducing effect on the mtDNA copy number also in stem cell-derived human neurons in vitro at therapeutic plasma levels. For patients not on these drugs, psychosis severity had an effect (ß = -0.129, p = 0.017), similar to age (ß = -0.159, p = 0.003) and LDL (ß = -0.119, p = 0.029) on whole blood mtDNAcnres. Further research is required to determine if mtDNAcnres reflects any psychosis-intrinsic mitochondrial changes.

Genetic variants of increased waist circumference in psychosis.

OBJECTIVE: We examined whether established metabolic risk genetic variants in the population confer a risk for increased waist circumference in patients with schizophrenia spectrum disorders and also an association with schizophrenia spectrum disorders irrespective of waist circumference. PATIENTS AND METHODS: We analyzed the association in (i) a case-case model in which patients with schizophrenia spectrum disorder with increased waist circumference (≥80 cm for women and ≥94 cm for men) (n=534) were compared with patients with normal waist circumference (<80 cm for women; <94 cm for men) (n=124), and in (ii) a case-control model in which schizophrenia spectrum disorder patients with increased waist circumference or irrespective of waist circumference were compared with population-derived controls (n=494) adjusted for age, sex, fasting glucose, smoking, and family history of diabetes. RESULTS: Genetic variants in five genes (MIA3, MRAS, P2RX7, CAMKK2, and SMAD3) were associated with increased waist circumference in patients with schizophrenia spectrum disorder (P<0.046). Genetic variants in three other genes (PPARD, MNTR1B, and NOTCH2) were associated with increased waist circumference in patients when compared with control individuals (P<0.037). Genetic variants in the PPARD, MNTR1B, NOTCH2, and HNF1B were nominally associated with schizophrenia spectrum disorder irrespective of waist circumference (P<0.027). No differences in waist circumference between specific psychosis diagnoses were detected. CONCLUSION: Increased waist circumference in patients with schizophrenia spectrum disorder may be explained, in part, by increased metabolic risk gene burden, and it indicates a shared genetic susceptibility to metabolic disorder and psychosis per se. Along these lines, common metabolic risk genetic variants confer a risk for increased waist circumference in patients with schizophrenia spectrum disorders.

Troponin T levels associated with genetic variants in NOTCH2 and MTNR1B in women with psychosis.

Psychosis patients have increased prevalence of metabolic disorders, which increase the risk for cardiovascular disease. Elevated troponin T level is an early biomarker of cardiovascular damage. We tested for association between troponin T levels and genetic risk variants of elevated blood glucose level in psychosis. Glucose and troponin T levels correlated positively. MTNR1B rs10830963 and NOTCH2 rs10923931 associated with troponin T levels in women, adjusted for glucose levels. These findings may indicate metabolic genetic influences on troponin T levels among women with psychosis.

Prediction of Cervical Endplate Size: One Size Does Not Fit All.

Significant variations exist in the footprint size of cervical vertebral endplates. In anterior cervical spine surgery, an implant that maximizes coverage of the endplate and contacts the apophyses may reduce subsidence and decrease risk of endplate fracture. The ability to accurately predict a patient's vertebral endplate size may be helpful for surgeons to preoperatively choose the optimal implant for the patient's specific anatomy. The purpose of this study was to (1) demonstrate the range of vertebral endplate sizes between individual patients and cervical levels and (2) determine if vertebral endplate size can be predicted based on patient characteristics and vertebral level. Fifty cervical computed tomography scans of patients 18 to 65 years old were selected for analysis. Superior vertebral endplate sizes of C3-C7 were measured medial-laterally and anteriorly-posteriorly. The medial-laterally measurement was taken from the midbody coronal view at the flat central region of the superior endplate, and the anteriorly-posteriorly measurement was taken at the midbody axial view from the front to back edge of the vertebral body. Age, height, weight, gender, and race were recorded for all patients. One-way analysis of variance, linear regressions, and multivariate regressions were performed. Patient height, age, gender, and race accounted for 51% to 71% of the variance between individuals, and endplate size increased by 1 mm in width and 0.6 mm in depth for each progressively more caudal vertebral level. Vertebral endplate size could be reliably calculated based on patient height, age, gender, and vertebral level. These data may be useful to assist surgeons in preoperative planning for patient-specific implant selection. [Orthopedics. 2016; 39(3):e526-e531.].

Diabetes and glucose disturbances in patients with psychosis in Sweden.

OBJECTIVE: The objectives of this study were to (1) analyze the prevalence of diabetes, prediabetes, and antidiabetic medication in patients with psychosis compared with control subjects and (2) determine what factors in patients with psychosis were associated with antidiabetic medication. METHOD: We studied 977 patients with psychosis recruited from outpatient clinics in Stockholm County, Sweden, and they were compared with 3908 non-psychotic control subjects for fasting plasma glucose levels; prevalence of diabetes, prediabetes, antidiabetic treatment, and tobacco use; and blood pressure, weight, height, and waist circumference. Group differences were evaluated with analysis of variance and χ(2) test, and factors associated with antidiabetic treatment were evaluated with logistic regression. RESULTS: Diabetes was observed in 94 (10%) patients with psychosis, 2.7 times the prevalence observed in control subjects. Among patients with psychosis, 87 (10%) had prediabetes (fasting glucose, 6.1-6.9 mmol/L) compared with 149 (3.8%) control subjects. Most patients with psychosis (77%) who had prediabetes fulfilled criteria for metabolic syndrome. In patients with psychosis, both lipid-lowering medication and fasting glucose were significantly associated with antidiabetic treatment. There was no significant relation between antidiabetic treatment and lifestyle factors such as smoking or degree of psychiatric illness. CONCLUSIONS: The high prevalence of impaired fasting glucose and metabolic syndrome in patients with psychosis warrants further clinical research in preventing or delaying the onset of diabetes in these patients by pharmacotherapy and/or lifestyle intervention.

Genetic and Clinical Factors Affecting Plasma Clozapine Concentration.

OBJECTIVE: To assess (1) the variance of plasma clozapine levels; (2) the relative importance of sex, smoking habits, weight, age, and specific genetic variants of cytochrome P450 1A2 (CYP1A2), uridine diphosphate glucuronosyltransferase 1A4 (UGT1A4), and multidrug resistance protein 1 (MDR1) on plasma levels of clozapine; and (3) the relation between plasma clozapine levels, fasting glucose levels, and waist circumference. METHOD: There were 113 patients on clozapine treatment recruited from psychosis outpatient clinics in Stockholm County, Sweden. Patients had genotype testing for single nucleotide polymorphisms: 2 in MDR1, 3 in CYP1A2, and 1 in UGT1A4. Multiple and logistic regression were used to analyze the relations. RESULTS: There was a wide variation in plasma concentrations of clozapine (mean = 1,615 nmol/L, SD = 1,354 nmol/L), with 37% of the samples within therapeutic range (1,100-2,100 nmol/L). Smokers had significantly lower plasma clozapine concentrations than nonsmokers (P ≤ .03). There was a significant association between the rs762551 A allele of CYP1A2 and lower plasma clozapine concentration (P ≤ .05). Increased fasting glucose level was 3.7-fold more frequent in CC and CA genotypes than AA genotype (odds ratio = 0.27; 95% confidence interval, 0.10-0.72). There was no significant relation between higher fasting glucose levels, larger waist circumference, and higher clozapine levels. CONCLUSIONS: It is difficult to predict plasma clozapine concentration, even when known individual and genetic factors are considered. Therefore, therapeutic drug monitoring is recommended in patients who are treated with clozapine.

Psychotic disorder is an independent risk factor for increased fasting glucose and waist circumference.

BACKGROUND: Psychosis is associated with excess cardiovascular morbidity and mortality. AIMS: To determine the prevalence of cardiovascular risk factors in patients with psychotic disorders compared with the population. METHODS: 731 consecutive patients with psychosis recruited from psychiatric outpatient clinics in Stockholm County, Sweden, were compared with 5580 individuals from a population study performed in the same area. The main outcome measures were waist circumference, body mass index (BMI) and fasting glucose. RESULTS: Mean waist circumference in patients vs. controls was for males 106 and 94 cm, respectively, and for females 97 and 85 cm, respectively (P < 0.001); mean fasting glucose in patients vs. controls was for males 5.8 and 5.2 mmol/l, respectively, and for females 5.6 and 4.8 mmol/l, respectively (P < 0.001). Comparisons were controlled for differences in age and family history of diabetes. Increased waist circumference was more common in psychotic patients compared with controls (OR = 3.99; 95% CI 3.09-5.15), controlling for fasting insulin, differences in gender, blood pressure, fasting glucose, family history of diabetes, age and tobacco use. Increased fasting blood glucose was also more common in psychotic patients (OR = 2.41; 95% CI 1.84-3.14) controlling for the same factors with the exception of fasting glucose and with the addition of increased waist circumference. CONCLUSION: Our study shows that the psychosis illness per se can be considered as a cardiovascular risk factor, independent of the traditional risk factors such as age and smoking.

Cellular localization of three vesicular glutamate transporter mRNAs and proteins in rat spinal cord and dorsal root ganglia.

Glutamate is transported into synaptic vesicles by vesicular glutamate transporter (VGLUT) proteins. Three different VGLUTs, VGLUT1, VGLUT2, and VGLUT3, have recently been characterized, and they are considered to represent the most specific marker so far for neurons using glutamate as transmitter. We analyzed the cellular localization of VGLUT1-3 in the rat spinal cord and dorsal root ganglia (DRGs) in control rats and after dorsal rhizotomy. Using in situ hybridization, VGLUT1 mRNA containing neurons were shown in the dorsomedial part of the intermediate zone, whereas VGLUT2 mRNA-expressing neurons were present in the entire intermediate zone, both populations most likely representing interneurons. VGLUT3 mRNA could not be detected in the spinal cord. In the ventral horn, a dense plexus of VGLUT1-immunoreactive (ir) nerve terminals was present, with large varicosities abutting on presumed motoneurons. In the dorsal horn a similarly dense plexus was seen, except in laminae I and II. A very dense plexus of VGLUT2-ir fibers was distributed in the entire gray matter of the spinal cord, with many fibers lying close to presumed motoneurons. Few VGLUT3-ir fibers were distributed in the white and gray matter, including lamina IX. However, a dense VGLUT3-ir plexus was seen in the sympathetic intermedio-lateral column (IML). Multiple-labeling immunohistochemistry revealed that the VGLUT1-, VGLUT2-, and VAChT-containing varicosities in lamina IX all represent separate entities. There was no colocalization of VGLUT3 with VAChT or 5-HT in varicose fibers of the ventral horn, but some VGLUT3-ir fibers in the IML were 5-HT-positive. Lesioning of the dorsal roots resulted in an almost complete disappearance of VGLUT1-ir fibers around motoneurons and a less pronounced decrease in the remaining gray matter, whereas the density of VGLUT2- and VAChT-ir fibers appeared unaltered after lesion. Many VGLUT1-ir neurons were observed in DRGs; they were almost all large and did not colocalize calcitonin gene-related peptide (CGRP), and there was no overlap between these markers in fibers in the superficial dorsal horn. VGLUT2 was, at most, seen in a few DRG neurons. Taken together, these results suggest that the VGLUTs mRNAs are present in distinct subsets of neuronal populations at the spinal level. VGLUT1 is mainly present in primary afferents from large, CGRP-negative DRG neurons, VGLUT2 has mainly a local origin, and VGLUT3 fibers probably have a supraspinal origin.