Comparison of analgesic efficacy of preoperative or postoperative carprofen with or without preincisional mepivacaine epidural anesthesia in canine pelvic or femoral fracture repair

OBJECTIVE: To compare analgesic efficacy of preoperative versus postoperative administration of carprofen and to determine, if preincisional mepivacaine epidural anesthesia improves postoperative analgesia in dogs treated with carprofen. STUDY DESIGN: Blind, randomized clinical study. ANIMALS: Dogs with femoral (n=18) or pelvic (27) fractures. METHODS: Dogs were grouped by restricted randomization into 4 groups: group 1 = carprofen (4 mg/kg subcutaneously) immediately before induction of anesthesia, no epidural anesthesia; group 2 = carprofen immediately after extubation, no epidural anesthesia; group 3 = carprofen immediately before induction, mepivacaine epidural block 15 minutes before surgical incision; and group 4 = mepivacaine epidural block 15 minutes before surgical incision, carprofen after extubation. All dogs were administered carprofen (4 mg/kg, subcutaneously, once daily) for 4 days after surgery. Physiologic variables, nociceptive threshold, lameness score, pain, and sedation (numerical rating scale [NRS], visual analog scale [VAS]), plasma glucose and cortisol concentration, renal function, and hemostatic variables were measured preoperatively and at various times after surgery. Dogs with VAS pain scores >30 were administered rescue analgesia. RESULTS: Group 3 and 4 dogs had significantly lower pain scores and amount of rescue analgesia compared with groups 1 and 2. VAS and NRS pain scores were not significantly different among groups 1 and 2 or among groups 3 and 4. There was no treatment effect on renal function and hemostatic variables. CONCLUSIONS: Preoperative carprofen combined with mepivacaine epidural anesthesia had superior postoperative analgesia compared with preoperative carprofen alone. When preoperative epidural anesthesia was performed, preoperative administration of carprofen did not improve postoperative analgesia compared with postoperative administration of carprofen. CLINICAL RELEVANCE: Preoperative administration of systemic opioid agonists in combination with regional anesthesia and postoperative administration of carprofen provides safe and effective pain relieve in canine fracture repair.

EEG signs of vigilance fluctuations preceding perceptual flips in multistable illusionary motion

This EEG study was performed to clarify the time course of brain electrical events and possible vigilance changes associated with perceptual flips during multistable perception. 13 healthy subjects (28.5 3.8 years) were recorded with a 21-channel digital EEG during a stroboscopic alternative motion paradigm implying illusionary motion with ambiguous direction. Perceptual flips were preceded by a significant decrease of EEG frequencies, and followed by a significant frequency increase with a trend to overshoot. EEG slowing is a reliable sign of vigilance decrease and can be related to thalamic deactivation. This is consistent with a recent fMRI study, which showed thalamic deactivation associated with perceptual flips. The study added important chronological information about this phenomenon and allows the conclusion that reduced vigilance facilitates perceptual discontinuities during multistable perception.

Dosimetric impact of geometric errors due to respiratory motion prediction on dynamic multileaf collimator-based four-dimensional radiation delivery

The synchronization of dynamic multileaf collimator (DMLC) response with respiratory motion is critical to ensure the accuracy of DMLC-based four dimensional (4D) radiation delivery. In practice, however, a finite time delay (response time) between the acquisition of tumor position and multileaf collimator response necessitates predictive models of respiratory tumor motion to synchronize radiation delivery. Predicting a complex process such as respiratory motion introduces geometric errors, which have been reported in several publications. However, the dosimetric effect of such errors on 4D radiation delivery has not yet been investigated. Thus, our aim in this work was to quantify the dosimetric effects of geometric error due to prediction under several different conditions. Conformal and intensity modulated radiation therapy (IMRT) plans for a lung patient were generated for anterior-posterior/posterior-anterior (AP/PA) beam arrangements at 6 and 18 MV energies to provide planned dose distributions. Respiratory motion data was obtained from 60 diaphragm-motion fluoroscopy recordings from five patients. A linear adaptive filter was employed to predict the tumor position. The geometric error of prediction was defined as the absolute difference between predicted and actual positions at each diaphragm position. Distributions of geometric error of prediction were obtained for all of the respiratory motion data. Planned dose distributions were then convolved with distributions for the geometric error of prediction to obtain convolved dose distributions. The dosimetric effect of such geometric errors was determined as a function of several variables: response time (0-0.6 s), beam energy (6/18 MV), treatment delivery (3D/4D), treatment type (conformal/IMRT), beam direction (AP/PA), and breathing training type (free breathing/audio instruction/visual feedback). Dose difference and distance-to-agreement analysis was employed to quantify results. Based on our data, the dosimetric impact of prediction (a) increased with response time, (b) was larger for 3D radiation therapy as compared with 4D radiation therapy, (c) was relatively insensitive to change in beam energy and beam direction, (d) was greater for IMRT distributions as compared with conformal distributions, (e) was smaller than the dosimetric impact of latency, and (f) was greatest for respiration motion with audio instructions, followed by visual feedback and free breathing. Geometric errors of prediction that occur during 4D radiation delivery introduce dosimetric errors that are dependent on several factors, such as response time, treatment-delivery type, and beam energy. Even for relatively small response times of 0.6 s into the future, dosimetric errors due to prediction could approach delivery errors when respiratory motion is not accounted for at all. To reduce the dosimetric impact, better predictive models and/or shorter response times are required.

Hip2Norm: an object-oriented cross-platform program for 3D analysis of hip joint morphology using 2D pelvic radiographs

We developed an object-oriented cross-platform program to perform three-dimensional (3D) analysis of hip joint morphology using two-dimensional (2D) anteroposterior (AP) pelvic radiographs. Landmarks extracted from 2D AP pelvic radiographs and optionally an additional lateral pelvic X-ray were combined with a cone beam projection model to reconstruct 3D hip joints. Since individual pelvic orientation can vary considerably, a method for standardizing pelvic orientation was implemented to determine the absolute tilt/rotation. The evaluation of anatomically morphologic differences was achieved by reconstructing the projected acetabular rim and the measured hip parameters as if obtained in a standardized neutral orientation. The program had been successfully used to interactively objectify acetabular version in hips with femoro-acetabular impingement or developmental dysplasia. Hip(2)Norm is written in object-oriented programming language C++ using cross-platform software Qt (TrollTech, Oslo, Norway) for graphical user interface (GUI) and is transportable to any platform.

Range of motion in anterior femoroacetabular impingement

The range of motion of normal hips and hips with femoroacetabular impingement relative to some specific anatomic reference landmarks is unknown. We therefore described: (1) the range of motion pattern relative to landmarks; (2) the location of the impingement zones in normal and impinging hips; and (3) the influence of surgical débridement on the range of motion. We used a previously developed and validated noninvasive 3-D CT-based method for kinematic hip analysis to compare the range of motion pattern, the location of impingement, and the effect of virtual surgical reconstruction in 28 hips with anterior femoroacetabular impingement and a control group of 33 normal hips. Hips with femoroacetabular impingement had decreased flexion, internal rotation, and abduction. Internal rotation decreased with increasing flexion and adduction. The calculated impingement zones were localized in the anterosuperior quadrant of the acetabulum and were similar in the two groups and in impingement subgroups. The average improvement of internal rotation was 5.4 degrees for pincer hips, 8.5 degrees for cam hips, and 15.7 degrees for mixed impingement. This method helps the surgeon quantify the severity of impingement and choose the appropriate treatment option; it provides a basis for future image-guided surgical reconstruction in femoroacetabular impingement with less invasive techniques.

Anteroposterior pelvic radiographs to assess acetabular retroversion: high validity of the "cross-over-sign"

Acetabular retroversion has been proposed to contribute to the development of osteoarthritis of the hip. For the diagnosis of this condition, conventional AP pelvic radiographs may represent a reliable, easily available diagnostic modality as they can be obtained with a reproducible technique allowing the anterior and posterior acetabular rims to be visible for assessment. This study was designed to: (i) determine cranial, central, and caudal anatomic acetabular version (AV) from cadaveric specimens; (ii) establish the validity and reliability of the radiographic measurements of central acetabular anteversion; and (iii) determine the validity and reliability of the radiographic "cross-over-sign" to detect acetabular retroversion. Using 43 desiccated pelvises (86 acetabuli) the anatomic AVs were measured at three different transverse planes (cranially, centrally, and caudally). From these pelvises, standardized AP pelvic radiographs were obtained. To directly measure central AV, a modified radiographic method is introduced for the use of AP pelvic radiographs. The validity and reliability of this radiographic method and of the radiographic cross-over-sign to detect cranial acetabular retroversion were determined. The mean central and caudal anatomic AVs were approximately 20 degrees , and the mean cranial AV was 8 degrees . Cranial retroversion (AV < 0 degrees ) was present in 19 of 86 hips (22%). A linear correlation was found between the central and cranial AV. Below 10 degrees of central AV, all acetabuli were cranially retroverted. Between 10 degrees and 20 degrees , 30% of the acetabuli were cranially retroverted, and above 20 degrees , only 1 of 45 acetabuli was cranially retroverted. The radiographic measurement of the central AV (20.3 +/- 6.5 degrees ) correlated strongly with the anatomic AV (20.1 +/- 6.4 degrees ). The sensitivity of the cross-over-sign to detect a cranial acetabular anteversion of less than 4 degrees was 96%, its specificity 95%, and the positive predictive and negative predictive values 90% and 98%, respectively. Both the modified radiographic anteversion measurements and the cross-over-sign demonstrated substantial inter- and intraobserver reliability. Retroversion is almost exclusively a problem of the cranial acetabulum. The cranial AV is on average 12 degrees lower than the central AV, with the latter directly measurable from AP pelvic radiographs. A central AV of less than 10 degrees was associated with cranial retroversion. The presence of a positive cross-over-sign is a highly reliable indicator of cranial AV of <4 degrees.

Application and assessment of a robust elastic motion correction algorithm to dynamic MRI

The purpose of this study was to assess the performance of a new motion correction algorithm. Twenty-five dynamic MR mammography (MRM) data sets and 25 contrast-enhanced three-dimensional peripheral MR angiographic (MRA) data sets which were affected by patient motion of varying severeness were selected retrospectively from routine examinations. Anonymized data were registered by a new experimental elastic motion correction algorithm. The algorithm works by computing a similarity measure for the two volumes that takes into account expected signal changes due to the presence of a contrast agent while penalizing other signal changes caused by patient motion. A conjugate gradient method is used to find the best possible set of motion parameters that maximizes the similarity measures across the entire volume. Images before and after correction were visually evaluated and scored by experienced radiologists with respect to reduction of motion, improvement of image quality, disappearance of existing lesions or creation of artifactual lesions. It was found that the correction improves image quality (76% for MRM and 96% for MRA) and diagnosability (60% for MRM and 96% for MRA).

Energy harvesting from body motion using rotational micro-generation

Autonomous system applications are typically limited by the power supply operational lifetime when battery replacement is difficult or costly. A trade-off between battery size and battery life is usually calculated to determine the device capability and lifespan. As a result, energy harvesting research has gained importance as society searches for alternative energy sources for power generation. For instance, energy harvesting has been a proven alternative for powering solar-based calculators and self-winding wristwatches. Thus, the use of energy harvesting technology can make it possible to assist or replace batteries for portable, wearable, or surgically-implantable autonomous systems. Applications such as cardiac pacemakers or electrical stimulation applications can benefit from this approach since the number of surgeries for battery replacement can be reduced or eliminated. Research on energy scavenging from body motion has been investigated to evaluate the feasibility of powering wearable or implantable systems. Energy from walking has been previously extracted using generators placed on shoes, backpacks, and knee braces while producing power levels ranging from milliwatts to watts. The research presented in this paper examines the available power from walking and running at several body locations. The ankle, knee, hip, chest, wrist, elbow, upper arm, side of the head, and back of the head were the chosen target localizations. Joints were preferred since they experience the most drastic acceleration changes. For this, a motor-driven treadmill test was performed on 11 healthy individuals at several walking (1-4 mph) and running (2-5 mph) speeds. The treadmill test provided the acceleration magnitudes from the listed body locations. Power can be estimated from the treadmill evaluation since it is proportional to the acceleration and frequency of occurrence. Available power output from walking was determined to be greater than 1mW/cm³ for most body locations while being over 10mW/cm³ at the foot and ankle locations. Available power from running was found to be almost 10 times higher than that from walking. Most energy harvester topologies use linear generator approaches that are well suited to fixed-frequency vibrations with sub-millimeter amplitude oscillations. In contrast, body motion is characterized with a wide frequency spectrum and larger amplitudes. A generator prototype based on self-winding wristwatches is deemed to be appropriate for harvesting body motion since it is not limited to operate at fixed-frequencies or restricted displacements. Electromagnetic generation is typically favored because of its slightly higher power output per unit volume. Then, a nonharmonic oscillating rotational energy scavenger prototype is proposed to harness body motion. The electromagnetic generator follows the approach from small wind turbine designs that overcome the lack of a gearbox by using a larger number of coil and magnets arrangements. The device presented here is composed of a rotor with multiple-pole permanent magnets having an eccentric weight and a stator composed of stacked planar coils. The rotor oscillations induce a voltage on the planar coil due to the eccentric mass unbalance produced by body motion. A meso-scale prototype device was then built and evaluated for energy generation. The meso-scale casing and rotor were constructed on PMMA with the help of a CNC mill machine. Commercially available discrete magnets were encased in a 25mm rotor. Commercial copper-coated polyimide film was employed to manufacture the planar coils using MEMS fabrication processes. Jewel bearings were used to finalize the arrangement. The prototypes were also tested at the listed body locations. A meso-scale generator with a 2-layer coil was capable to extract up to 234 µW of power at the ankle while walking at 3mph with a 2cm³ prototype for a power density of 117 µW/cm³. This dissertation presents the analysis of available power from walking and running at different speeds and the development of an unobtrusive miniature energy harvesting generator for body motion. Power generation indicates the possibility of powering devices by extracting energy from body motion.

Pelvic radiography in ATLS algorithms: A diminishing role?

ABSTRACT: BACKGROUND: Pelvic x-ray is a routine part of the primary survey of polytraumatized patients according to Advanced Trauma Life Support (ATLS) guidelines. However, pelvic CT is the gold standard imaging technique in the diagnosis of pelvic fractures. This study was conducted to confirm the safety of a modified ATLS algorithm omitting pelvic x-ray in hemodynamically stable polytraumatized patients with clinically stable pelvis in favour of later pelvic examination by CT scan. METHODS: We conducted a retrospective analysis of all polytraumatized patients in our emergency room between 01.07.2004 and 31.01.2006. Inclusion criteria were blunt abdominal trauma, initial hemodynamic stability and a stable pelvis on clinical examination. We excluded patients requiring immediate intervention because of hemodynamic instability. RESULTS: We reviewed the records of n = 452 polytraumatized patients, of which n = 91 fulfilled inclusion criteria (56% male, mean age = 45 years). The mechanism of trauma included 43% road traffic accidents, 47% falls. In 68/91 (75%) patients, both a pelvic x-ray and a CT examination were performed; the remainder had only pelvic CT. In 6/68 (9%) patients, pelvic fracture was diagnosed by pelvic x-ray. None of these 6 patients was found having a false positive pelvic x-ray, i.e. there was no fracture on pelvic CT scan. In 3/68 (4%) cases a fracture was missed in the pelvic x-ray, but confirmed on CT (false negative on x-ray). None of the diagnosed fractures needed an immediate therapeutic intervention. 5 (56%) were classified type A fractures, and another 4 (44%) B 2.1 in computed tomography (AO classification). One A 2.1 fracture was found in a clinically stable patient who only received CT scan (1/23). CONCLUSION: While pelvic x-ray is an integral part of ATLS assessment, this retrospective study suggests that in hemodynamically stable patients with clinically stable pevis, its sensitivity is only 67% and it may safely be omitted in favor of a pelvic CT examination if such is planned in adjunct assessment and available. The results support the safety and utility of our modified ATLS algorithm. A randomized controlled trial using the algorithm can safely be conducted to confirm the results.