Accuracy Of Placements Research Articles

Assessing the Intraoperative Accuracy of Pedicle Screw Placement by Using a Bone-Mounted Miniature Robot System through Secondary Registration.

IntroductionPedicle screws are commonly employed to restore spinal stability and correct deformities. The Renaissance robotic system was developed to improve the accuracy of pedicle screw placement.PurposeIn this study, we developed an intraoperative classification system for evaluating the accuracy of pedicle screw placements through secondary registration. Furthermore, we evaluated the benefits of using the Renaissance robotic system in pedicle screw placement and postoperative evaluations. Finally, we examined the factors affecting the accuracy of pedicle screw implantation.ResultsThrough use of the Renaissance robotic system, the accuracy of Kirschner-wire (K-wire) placements deviating <3 mm from the planned trajectory was determined to be 98.74%. According to our classification system, the robot-guided pedicle screw implantation attained an accuracy of 94.00% before repositioning and 98.74% after repositioning. However, the malposition rate before repositioning was 5.99%; among these placements, 4.73% were immediately repositioned using the robot system and 1.26% were manually repositioned after a failed robot repositioning attempt. Most K-wire entry points deviated caudally and laterally.ConclusionThe Renaissance robotic system offers high accuracy in pedicle screw placement. Secondary registration improves the accuracy through increasing the precision of the positioning; moreover, intraoperative evaluation enables immediate repositioning. Furthermore, the K-wire tends to deviate caudally and laterally from the entry point because of skiving, which is characteristic of robot-assisted pedicle screw placement.

Individual differences in algebraic cognition: Relation to the approximate number and semantic memory systems

The relation between performance on measures of algebraic cognition and acuity of the approximate number system (ANS) and memory for addition facts was assessed for 171 ninth graders (92 girls) while controlling for parental education, sex, reading achievement, speed of numeral processing, fluency of symbolic number processing, intelligence, and the central executive component of working memory. The algebraic tasks assessed accuracy in placing x,y pairs in the coordinate plane, speed and accuracy of expression evaluation, and schema memory for algebra equations. ANS acuity was related to accuracy of placements in the coordinate plane and expression evaluation but not to schema memory. Frequency of fact retrieval errors was related to schema memory but not to coordinate plane or expression evaluation accuracy. The results suggest that the ANS may contribute to or be influenced by spatial–numerical and numerical-only quantity judgments in algebraic contexts, whereas difficulties in committing addition facts to long-term memory may presage slow formation of memories for the basic structure of algebra equations. More generally, the results suggest that different brain and cognitive systems are engaged during the learning of different components of algebraic competence while controlling for demographic and domain general abilities.

Validation of model-guided placement of external ventricular drains

Inaccurate placement of external ventricular drains (EVDs) is a common issue in cerebrospinal diversion procedures. The conventional freehand technique results in a high fraction of sub-optimally placed catheters, and the use of image guidance can improve these results. The purpose of this paper is the validation of the use of an average model for guidance of EVD procedures. Three neurosurgeons have tested the model-based technique on three normal volunteers, and we have compared the model-based technique to the freehand technique and neuronavigation based on volunteer-specific images. Our results show that the surgeons perform significantly better when using the model-based technique than when using the freehand technique. Our results suggest that the use of an average model may improve the accuracy of catheter placements. However, further refinement of the method and testing in a clinical setting is required.

Utility of Evoked EMG Monitoring to Improve Bone Screw Placements in the Cervical Spine

EMG threshold testing as a guide to accurate screw placement was examined during posterior cervical spine instrumentation. The accuracy of screw placements was compared with the surgeon blinded and unblinded to EMG thresholds. To determine the utility of EMG threshold testing in improving screw placements in the lateral mass and pedicles of the cervical/upper thoracic spine. EMG threshold testing in the lumbar spine is generally thought to improve the accuracy of pedicle screw placements. These results may not generalize to the cervical spine, where smaller pedicles, bicortical pilot holes, and the orientation of lateral mass screws away from midline may result in different alert thresholds. Triggered EMG thresholds were obtained from pilot holes in 244 lateral mass and 113 pedicles from 32 patients. Thresholds were compared with the accuracy of screw placements as determined from postoperative computed tomography scans. The percentage of inaccurate and potentially dangerous (IAPD) screws with the surgeon blinded and unblinded to EMG thresholds was determined. EMG threshold testing was more accurate in predicting IAPD screw trajectories in the pedicles (likelihood ratio 5.1) as compared with the lateral mass (likelihood ratio 2.9). In the pedicles, the number of IAPD screws decreased from 4.5% in the blinded controls to 0% in the unblinded group. In the lateral mass, there were no IAPD screw placements in the blinded control group, whereas 2% of the screws in the unblinded group were IAPD. EMG threshold testing in the cervical spine (C3, T1) is a moderately accurate diagnostic test and more predictive of potentially dangerous screw trajectories in the pedicles (C7, T1) as compared with the lateral mass (C3-C6). EMG threshold testing may decrease potentially dangerous screw placements in the pedicles, but may have less utility in the case of the lateral mass because of less reproducible placement of the stimulating probe.

Factors associated with external ventricular drain placement accuracy: data from an electronic health record repository

We evaluated external ventricular drain placement for factors associated with placement accuracy. Data were acquired using an electronic health record data requisition tool. Medical records of all patients who underwent ventriculostomy from 2003 to 2010 were identified and evaluated. Patient demographics, diagnosis, type of guidance and number of catheter passes were searched for and recorded. Post-procedural hemorrhage and/or infection were identified. A grading scale was used to classify accuracy of catheter placements. A multiple logistic regression model was developed to assess features associated with accurate catheter placement. One hundred nine patients who underwent 111 ventriculostomies from 2003 to 2010 were identified. Patient diagnoses were classified into vascular (63 %), tumor (21 %), trauma (14 %), and cyst (2 %). Procedures were performed freehand in 90 (81 %), with the Ghajar guide in 17 (15 %), and with image guidance in 4 (4 %) patients. Eighty-eight (79 %) catheters were placed in the correct location. Trauma patients were more likely to have catheters misplaced (p = 0.007) whereas patients in other diagnostic categories were not significantly associated with misplaced catheters. Post-procedural hemorrhage was noted in 2 (1.8 %) patients on post-procedural imaging studies. Five (4.5 %) definite and 6 (5.4 %) suspected infections were identified. External ventricular drain placement can be performed accurately in most patients. Patients with trauma are more likely to have catheters misplaced. Further development is required to identify and evaluate procedure outcomes using an electronic health record repository.

The accuracy of bone tunnel position using fluoroscopic-based navigation system in anterior cruciate ligament reconstruction

The first purpose of this study was to examine whether fluoroscopic-based navigation system contributes to the accuracy and reproducibility of the bone tunnel placements in single-bundle anterior cruciate ligament (ACL) reconstruction. The second purpose was to investigate the application of the navigation system for double-bundle ACL reconstruction. A hospital-based case-control study was conducted, including a consecutive series of 55 patients. In 37 patients who received single-bundle ACL reconstruction, surgeries were performed with this system for 19 knees (group 1) and without this system for 18 knees (group 2). The positioning of the femoral and tibial tunnels was evaluated by plain sagittal radiographs. In 18 patients who received double-bundle ACL reconstruction using the navigation system (group 3), the bone tunnel positions were assessed by three-dimensional computed tomography (3D-CT). Clinical assessment of all patients was followed with the use of Lysholm Knees Score and IKDC. Taking 0% as the anterior and 100% as the posterior extent, the femoral tunnels were 74.9±3.0% in group 1 and 71.5±5.8% in group 2 along Blumensaat's line, and the tibial tunnels were 42.3±1.4% in group 1 and 42.5±4.6% in group 2 along the tibia plateau. The bone tunnel positions in group 1 were located significantly closer to the position planned preoperatively and varied less in both femur and tibial side, compared with those without navigation (group 2). (Femur: P<0.05, Tibia: P<0.001) 3D-CT evaluation of double-bundle ACL reconstruction (group 3) also demonstrated that the bone tunnel positions of both anteromedial (AM) and posterolateral (PL) were placed as we expected. The fluoroscopic-based navigation system contributed to the more reproducible placement of the bone tunnel during single-bundle ACL reconstruction compared with conventional technique. Additionally, this device was also useful for double-bundle ACL reconstruction. Case-control study, Therapeutic study, Level III.

Ball tip technique for thoracic pedicle screw placement in patients with adolescent idiopathic scoliosis

The aim in this study was to evaluate the efficacy of the ball tip technique in placing thoracic pedicle screws (TPSs), as compared with the conventional freehand technique, in both a cadaveric study and a clinical study of patients with adolescent idiopathic scoliosis. Although posterior spinal surgery using TPSs has been widely applied, these screws are associated with the potential risk of vascular, pulmonary, or neurological complications. To further enhance the accuracy and safety of TPS placement, the authors developed the ball tip technique. After creating an appropriate starting point for probe insertion, a specially designed ball tip probe consisting of a ball-shaped tip with a flexible metal shaft is used to make a guide hole into the pedicle. Holding the probe with the fingertips while using an appropriate amount of pressure or by tapping it gently and continuously with a hammer, one can safely insert the ball tip probe into the cancellous channel in the pedicle. In a cadaveric study, 5 spine fellows with similar levels of experience in placing TPSs applied the ball tip or the conventional technique to place screws in 5 cadavers with no spinal deformities. The incidence of misplaced screws was evaluated by dissecting the spines. In a clinical study, 40 patients with adolescent idiopathic scoliosis underwent posterior surgery with TPS placement via the ball tip or conventional technique (20 patients in each treatment group). The accuracy of the TPS placements was evaluated on postoperative axial CT scanning. In the cadaveric study, 100 TPSs were evaluated, and the incidence of misplaced screws was 14% in the ball tip group and 34% in the conventional group (p = 0.0192). In the clinical study, 574 TPSs were evaluated. One hundred seventy-one intrapedicular screws (67%) were recognized in the conventional group and 288 (90%) in the ball tip group (p < 0.01). In the conventional and ball tip groups, the respective numbers of TPSs with a pedicle breach of < or = 2 mm were 20 (8%) and 15 (5%), those with a pedicle breach of > 2 mm were 32 (13%) and 9 (3%; p < 0.01), and those located in the costovertebral joints were 32 (13%) and 7 (2%). In both cadaveric and clinical studies the ball tip technique enhanced the accuracy of TPS placement as compared with the conventional freehand technique. Thus, the ball tip technique is useful for the accurate and safe placement of TPSs in deformed spines.

Intraosseous Ultrasound in the Placement of Pedicle Screws in the Lumbar Spine

Experimental and intraoperative evaluation of the efficiency of a novel technique. To determine the accuracy of pedicle screw hole placements before screw implantation in the lumbar spine. Deviations from planned trajectories occur in a significant number of screw placements in posterior lumbar fixation. Several techniques have been proposed to minimize this complication, although none has gained general acceptance. This may be due to costs associated with their implementation or considerably extended operating times required by some techniques. Pedicle screw holes were placed in 24 pedicles of 2 postmortem human lumbar spine specimens. Sixteen optimal trajectories were placed and 8 intentional cortical breaches. Each pedicular drill hole was examined using a 360 degrees ultrasound transducer and CT scanning. The ultrasonographic images were reviewed by 3 independent investigators who were blinded to the CT findings. In addition, 20 screw holes were placed intraoperatively in 3 patients, and equally assessed by intraoperative intraosseous ultrasonography and postoperative CT scanning. Ultrasonographic images of pedicle screw holes in postmortem human spine specimen were correctly interpreted in 99% of cases. No cortical breech was missed, i.e., no false-negatives occurred. Intraoperative findings closely matched the experimental data. None of the intraoperative ultrasound scans demonstrated a cortical breach, a finding confirmed by postoperative CT. The intraoperative time required for the ultrasonographic analysis of each pedicle was about 1 minute and the interpretation of the resulting images was judged intuitive by the evaluating neurosurgeons. Intraosseous ultrasound is a highly reliable technique for the intraoperative assessment of pedicle screw holes before pedicle screw placement. Additional expenses with respect to procedure time and manpower are minimal.

Modeling of metal interaction geometries for protein–ligand docking

The accurate modeling of metal coordination geometries plays an important role for structure-based drug design applied to metalloenzymes. For the development of a new metal interaction model, we perform a statistical analysis of metal interaction geometries that are relevant to protein-ligand complexes. A total of 43,061 metal sites of the Protein Data Bank (PDB), containing amongst others magnesium, calcium, zinc, iron, manganese, copper, cadmium, cobalt, and nickel, were evaluated according to their metal coordination geometry. Based on statistical analysis, we derived a model for the automatic calculation and definition of metal interaction geometries for the purpose of molecular docking analyses. It includes the identification of the metal-coordinating ligands, the calculation of the coordination geometry and the superposition of ideal polyhedra to identify the optimal positions for free coordination sites. The new interaction model was integrated in the docking software FlexX and evaluated on a data set of 103 metalloprotein-ligand complexes, which were extracted from the PDB. In a first step, the quality of the automatic calculation of the metal coordination geometry was analyzed. In 74% of the cases, the correct prediction of the coordination geometry could be determined on the basis of the protein structure alone. Secondly, the new metal interaction model was tested in terms of predicting protein-ligand complexes. In the majority of test cases, the new interaction model resulted in an improved docking accuracy of the top ranking placements.

Reproducibility of irregular radiation fields for malignant lymphoma.

Radiation treatment for malignant lymphoma requires large field irradiation with irregular blocks according to the individual anatomy and tumor configuration. For determination of safety margins (PTV) we quantitatively analysed the accuracy of field and block placement with regard to different anatomical regions. Forty patients with malignant lymphoma were irradiated using the classical supra-/infradiaphragmatic field arrangements. Treatment was performed with 10-MeV photons and irregularly shaped, large opposing fields. We evaluated the accuracy of field and block placements during the treatment courses by comparing the regularly performed verification-with the simulation films. Deviations were determined with respect to the field edges and the central axis, along the x- and z-axis. With regard to the field edges, mean deviations of 2.0 mm and 3.4 mm were found along the x- and z-axis. The corresponding standard deviations were 3.4 mm and 5.5 mm, respectively. With regard to the shielding blocks, mean displacement along the x- and z-axis was 2.2 mm and 3.8 mm. In addition, overall standard deviations of 5.7 mm (x-axis) and 7.1 mm (z-axis) were determined. During the course of time an improved accuracy of block placement was notable. Systematic analysis of port films gives information for a better defining safety margins in external radiotherapy. Evaluation of verification films on a regular basis improves set-up accuracy by reducing displacements.

Roles of Somatostatin and Growth Hormone-Releasing Factor in Ether Stress Inhibition of Growth Hormone Release

In order to evaluate the release of somatostatin (SRIF) and growth hormone-releasing factor (GRF) into the pituitary gland in response to ether stress, a push-pull perifusion (PPP) technique has been used in freely moving rats. Push-pull cannulae (PPC) were implanted into the anterior pituitary (AP) glands of male rats. After a 7-day recovery period the rats were fitted with indwelling jugular catheters. The next day the animals were subjected to PPP of the AP during 1 h followed by ether stress (2 min) and another hour of perifusion. The perifusion flow was 20 microliters/min and 10-min fractions were collected and assayed for SRIF and GRF by RIA. Plasma growth hormone (GH) levels were assayed every 10 min. At the end of the experiments, the accuracy of PPC tip placements was ascertained with a dissecting microscope. Under basal conditions there were 2.9 pulses/h of SRIF with an amplitude of 12.76 +/- 0.46 pg. The output of SRIF and GRF in the 10-min period beginning with application of ether was increased 2-fold (p less than 0.005 and p less than 0.01, respectively). Interestingly, the increased release of SRIF continued for an additional 10 min, whereas GRF output decreased and was almost undetectable. The release of both GRF and SRIF had returned to basal values 20-30 min after stress. Mean plasma GH levels were significantly lowered 10 min after stress. Each of the 9 animals showed a restoration of pulsatile GH release to basal levels within 20-30 min after stress. Our findings provide compelling evidence that SRIF plays a prominent role in stress-induced inhibition of GH release in the rat by blocking the response to the transient elevation of GRF and continuing to suppress GH release for 20 min.

Perspectives in Plant Serotaxonomy

The capacity to view recent data in proper relation to other information, or the ability to correctly judge the significance of facts and ideas, requires a knowledge of both the past mistakes and the forward strides within a discipline. This paper is intended to help the reader formulate perspectives concerning 65 years of plant serotaxonomic research. The discovery that the immune reaction was only relatively specific and that the degree of crossreactivity was essentially proportional to the degree of relationships between organisms had important implications for comparative systematic serology. It is the specific reactions, between determinants and antideterminants, which provide a measurement of protein similarities. The comparison of protein mixtures, rather than purified single proteins, has dominated taxonomic research because such an approach provides serological overall similarity, and thus a multicharacter comparison. The antisystematic reactions have recently been shown to result from variation in the systematic ranges of determinants; and the absorption (presaturation) technique for removing common determinants increases the accuracy of serological placements. The following items were evaluated: antigenic preparations, adjuvants, injection procedures, single versus mixed protein extractions, kind of plant tissue extracted, and the interference of secondary compounds. Cornus canadensis and C. suecica were found to be serologically very similar. The tested species of the genus Cornus were divided into three distinct serological groupings. The serological data support the separation of the Cornaceae and Nyssaceae; and the inclusion of Camptotheca and Nyssa in the Nyssoideae, and Davidia in the Davidioideae, both of the family Nyssaceae. Nyssa biflora and N. sylvatica were serologically very similar; N. ogeche and N. aquatica were serologically distinct from each other and from N. biflora and N. sylvatica. Nyssa ogeche was the most distinct species of the genus. Corokia cotoneaster had very little serological similarity with any of the tested species of the Cornales. To have the capacity to view recent data in proper relation to other information, or the ability to correctly judge the significance of facts and ideas, requires a knowledge of past mistakes and the forward strides within a discipline. It also requires a degree of knowledge of the individual components as well as the total products resulting from the various component combinations. The author hopes this manuscript will provide the reader with the necessary information and literature citations which will allow the formulation of perspectives concerning 65 years of plant serotaxonomic research. The present age of chemosystematics or chemotaxonomic publications commenced to appear in the early 1950's. The oldest of the present age approaches is serotaxonomy and the newest is amino acid sequencing (Cronquist, 1976). The discovery of serological reactions in Austria via the occurrence of precipitin reactions took place 80 years ago (Kraus, 1897). This discovery provided a new technique which was soon used to aid in the investigation of systematic problems in animals. Within two years after the discovery of the precipitin re' I dedicate this publication to the memory of my friend and fellow phytoserologist, Dr. Josef Kloz, who died in his 55th year on October 22, 1976 in Czechoslovakia. The research was supported by NSF Grants GB-13202 and BMS 75-17805. 2 Department of Botany, Rutgers University, New Brunswick, New Jersey 08903. ANN. Missoum BOT. GARD. 64: 147-160. This content downloaded from 157.55.39.255 on Mon, 23 May 2016 05:55:00 UTC All use subject to http://about.jstor.org/terms 148 ANNALS OF THE MISSOURI BOTANICAL GARDEN [VOL. 64 action the technique was applied to comparative problems by the Frenchman Bordet (1899). This was followed by a series of extensive comparative studies which were conducted with various animals by the Englishman Nuttall (1901, 1904). Thus biologists have known for 75 years that organisms may share antigenic material (substances capable of inducing the formation of antibodies and able to react with the antibodies); and that when they share the same antigenic material in different proportions it is assumed that the organisms are related. At first it was believed that the immune reaction was absolutely specific, that is, that an antiserum would react only with the antigen that stimulated its production. However, Bordet (1899) in conducting research with birds reported that the reaction was only relatively specific and that the degree of cross-reactivity was essentially proportional to the degree of relationships between organisms. It was this early discovery which had important implications for systematics and started the pioneer investigations in the discipline of comparative animal sys-