[Show abstract][Hide abstract] ABSTRACT: To determine the effect of bipolar cooled radiofrequency ablation (BCRF) on bone and tumour in a lapine pathologic femoral model. Under institutional approval, twelve New Zealand white rabbits received a single femoral injection of VX2 carcinoma cells (day 0). The rabbit femora, (n = 24), were block-randomized into four experimental groups: tumour-bearing radiofrequency ablation (RFA) treated, healthy bone RFA treated, tumour-bearing shams and healthy bone shams (n = 6 per group). 15 min of thermally regulated (65 °C) BCRF was applied at day 14. Pre- and post-treatment MR imaging was performed and repeated at day 28 prior to euthanasia. Histologic evaluation was used to determine treatment effect on tumour and bone tissue. A thirteenth injected rabbit served as a histologic control (no BCRF electrode placement). Large volumes (12.9 ± 5.5 cm(3)) of thermal ablation were achieved. An eight-fold reduction in tumour growth resulted in RFA treated animals compared to tumour-bearing sham controls (p < 0.001). Osteolysis was controlled in the tumour-treated group. Therapeutic effects were best imaged using MR contrast-enhanced SPoiled Gradient Recalled (SPGR) sequences. Osteoclasts and osteoblasts were observed to be sensitive to BCRF but osteocytes were more resilient. A small number of tumour cells within BCRF treated regions appeared viable post treatment. New bone formation was stimulated in the periphery of the targeted BCRF treatment zone. Structurally large VX2 tumour volumes within bone were successfully ablated with BCRF, stimulating new bone formation in the treatment periphery, although viable appearing osteocytes and tumour cells were observed in some treated regions.
[Show abstract][Hide abstract] ABSTRACT: Potential peripheral sources of deep pain can require invasive evocative tests for their assessment. Here we perform research whose ultimate goal is development of a non-invasive evocative test for deep painful tissue.
We used a rat model of inflammation to show that intense focused ultrasound (iFU) differentially stimulates inflamed versus control tissue and can identify allodynia. To do so we applied iFU to inflamed and normal tissue below the skin of rats' hind paws and measured the amount of ultrasound necessary to induce paw withdrawal.
iFU of sufficient strength (spatial and temporal average intensities ranged from 100-350 W/cm(2)) caused the rat to withdraw its inflamed paw, while the same iFU applied to the contralateral paw failed to induce withdrawal, with sensitivity and specificity generally greater than 90%. iFU stimulation of normal tissue required twice the amount of ultrasound to generate a withdrawal than did inflamed tissue, thereby assessing allodynia. Finally, we verified in a preliminary way the safety of iFU stimulation with acute histological studies coupled with mathematical simulations.
Given that there exist systems to guide iFU deep to the skin, image-guided iFU may one day allow assessment of patient's deep, peripheral pain generators.
[Show abstract][Hide abstract] ABSTRACT: The study aims to demonstrate the unique sonographic features of the commercially available intrathecal drug delivery systems.
"Not-for-human-use" pumps were obtained, placed in a tray, and covered with an ultrasound phantom gel. The anterior surface of each pump was scanned and the sonographic features were observed and recorded.
All systems have a centrally located reservoir port (RP) and a peripherally located catheter access port (CAP) that are observable on ultrasound. The RP of the SynchroMed II system (Medtronic, Minneapolis, MN, USA) appears as an anechoic depression and a break in the bright echogenic line of the superior pump surface. The CAP appears as smaller diameter conical depression outside the circular perimeter of the pump. The RP of the MedStream system (Codman & Shurtleff, Inc., Raynham, MA, USA) has a dome-shaped appearance. The CAP appears as a smaller dome-shaped object that is off center but still contained within the circular perimeter of the pump. Similarly, the RP of the Prometra system (Flowonix Medical Inc, Mt. Olive, NJ, USA) is a dome-shaped object. The CAP visually appears similar to the reservoir access port of the SynchroMed II system, namely a small depression and a break in the bright echogenic line of the pump surface, outside the perimeter of the pump.
In all programmable intrathecal pumps, the RP can be readily identified sonographically. Potentially, the dome-shaped configuration of RP for the Prometra and MedStream systems make the access easier, when compared with SynchroMed II system. Ultrasound could potentially be utilized to localize the RP and CAP for all the systems as each of the three systems has a unique sonographic appearance.
[Show abstract][Hide abstract] ABSTRACT: Chronic low back pain related to degenerative spondylosis is commonly managed by the radiofrequency ablation of sensory nerves. Fluoroscopic guidance has been considered mandatory to ensure placement of the active tip of the cannula parallel to the nerve to provide adequate neurolysis. Conversely, analgesic (or diagnostic) blockade is usually accomplished by placing the needle perpendicular to the nerve using either fluoroscopy or ultrasound (US) guidance. The recently introduced disposable equipment of internally cooled radiofrequency allows the denervaion procedure to be performed similarly to the routine diagnostic block. Consequently, US may now potentially be used for image-guided radiofrequency neurotomy. We sought to compare the accuracy using a novel US-based technique with the traditional fluoroscopy-guided placement.
The proof of concept study was performed using a magnetic positioning US-guided system. The precision of needle placements was compared with the standard fluoroscopic guidance. The primary outcome of this study was defined as the procedural accuracy. Procedural and radiation exposure time was also recorded. In addition, projected operational expenses were calculated.
Ultrasound-guided procedural accuracy reached 97%. Both the imaging and procedure times were similar between the 2 forms of imaging guidance. Of significant importance, the US-guided approach (no radiation exposure) was quantitatively advantageous over fluoroscopy-guidance, which required an average of 170 seconds of radiation per procedure. Thus, the US method seems to be cost effective.
A magnetic positioning system allows accurate and quick US-guided placement of radiofrequency cannula to the desired anatomical targets, sparing patients and personnel from exposure to ionized radiation.
Regional anesthesia and pain medicine 12/2013; 39(1). DOI:10.1097/AAP.0000000000000032 · 3.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cancer spread to the spine affects bone stability and can lead to pathologic fracture and neurologic impairment. Radiofrequency ablation (RFA) recently has gained popularity in treating skeletal tumors. Conventional RFA devices use a monopolar design, which limits the ability to comprehensively treat large tumors in bony tissues and may pose risks to adjacent critical normal neurologic tissues when applied to vertebrae. New bipolar-cooled radiofrequency (BCRF) may generate larger controlled lesions without the same degree of risk to adjacent structures.
The spine journal: official journal of the North American Spine Society 11/2013; 14(2). DOI:10.1016/j.spinee.2013.08.041 · 2.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Echogenicity of regional anesthesia needles has been tested on different preclinical models; however, previous studies were done in an ideal experimental setting utilizing high-frequency insonation and superficially located targets. Because steep-angle deep injections are typically required for spinal and other chronic pain procedures, and low-frequency transducers are used, further feasibility study is warranted.
To determine effectiveness of steep-angle deep injections, typically required for spinal and other chronic pain procedures.
Experimental laboratory study.
Willed Body Program, University of Washington.
In-plane lumbar spine procedures with 50° and 70° angles were performed on a human cadaver. The images and video clips of a non-echogenic (Quincke-type) and echogenic (SonoPlex, StimuQuick, and EchoStim) needle placements were presented to 3 blinded assessors who rated the needle visibility on a 4-point scale. The data was statistically analyzed to determine the differences in visibility between the needles with and without the digital image enhancement, and to compare the video clips to captured images.
ANOVA analysis demonstrated that overall SonoPlex was significantly better (P = 0.02) than other needles. SonoPlex maintained its superiority in the subset of facet joint injections (P = 0.02), followed by Quincke-type, then the StimuQuik, and EchoStim needles. In deep procedures, EchoStim was comparable with SonoPlex (P = 0.03), and they both were better than the other 2 needles. The enhanced images received higher rates, with a 0.6 point mean improved rating (P = 0).
This study is limited by choice of needles, number of experiments performed, and potential postmortem changes of echogenicity.
The SonoPlex needle appeared to have better echogenicity in this study. While non-echogenic Quincke-type needle visibility was adequate in superficial placements, it was limited in deep injections. An imaging enhancement is effective in improving needle visibility and should be used whenever possible.
[Show abstract][Hide abstract] ABSTRACT: Intercostal nerve (ICN) injections are routinely performed under anatomic landmark or fluoroscopic guidance for acute and chronic pain indications. Ultrasound (US) is being used increasingly to perform ICN injections, but there is lack of evidence to support categorically the benefits of US over conventional techniques. We compared guidance with US versus anatomic landmarks for accuracy and safety of ICN injections in cadavers in a 2-phase study that included evaluation of deposition of injected dye by dissection and spread of contrast on fluoroscopy.
A cadaver experiment was performed to validate US as an imaging modality for ICN blocks. In the first phase of the study, 12 ICN injections with 2 different volumes of dye were performed in 1 cadaver using anatomic landmarks on one side and US-guidance on the other (6 injections on each side). The cadaver was then dissected to evaluate spread of the dye. The second phase of the study consisted of 74 ICN injections (37 US-guided and 37 using anatomic landmarks) of contrast dye in 6 non-embalmed cadavers followed by fluoroscopy to evaluate spread of the contrast dye.
In the first phase of the study, the intercostal space was identified with US at all levels. Injection of 2 mL of dye was sufficient to ensure compete staining of the ICN for 5 of 6 US-guided injections but anatomic landmark guidance resulted in correct injection at only 2 of 6 intercostal spaces. No intravascular injection was found on dissection with either of the guidance techniques. In the second phase of the study, US-guidance was associated with a higher rate of intercostal spread of 1 mL of contrast dye on fluoroscopy compared with anatomic landmarks guidance (97% vs 70%; P = 0.017).
Ultrasound confers higher accuracy and allows use of lower volumes of injectate compared with anatomic landmarks as a guidance method for ICN injections in cadavers. Ultrasound may be a viable alternative to anatomic landmarks as a guidance method for ICN injections.
Regional anesthesia and pain medicine 10/2013; 38(6). DOI:10.1097/AAP.0000000000000006 · 3.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Implanted peripheral nerve stimulation is one of the earliest developed methods of neuromodulation for the treatment of chronic neuropathic pain. It is traditionally performed by surgical exposure and implantation of a paddle lead. Ultrasound-guided percutaneous placement of cylindrical leads has been proposed as an alternative. However, those leads are fragile and prone to migration. Minimally invasive paddle lead implantation may improve long-term results while minimizing surgical insult. A feasibility laboratory study was performed.
Ultrasound-guided placements of a narrow paddle lead were performed in the upper and lower extremities of a human cadaver. Ultrasonography was used to record the lead position relative to the target nerves. Dissections were performed, and digital photography was completed. Anatomic images were analyzed.
All experiments were successfully accomplished. Although ultrasound localization of the upper extremity nerves was straightforward and clear, all procedural steps were technically easier at the lower extremity. For the latter, fewer attempts were required to maintain the lead in the desired tissue plane. Ultrasound revealed an acoustic shadowing of the underlying nerves in both the short- and long-axis views by the inserted lead. All dissections revealed a parallel to the nerve lead placement with at least four contacts facing the nerve. The lead appeared to be more mechanically stable at the lower extremity.
This anatomic study confirmed technical feasibility of percutaneous placement of a narrow paddle-type lead for the peripheral nerve stimulation that may potentially improve stimulation and reduce migrations.
[Show abstract][Hide abstract] ABSTRACT: Previous studies have observed that individual pulses of intense focused ultrasound (iFU) applied to inflamed and normal tissue can generate sensations, where inflamed tissue responds at a lower intensity than normal tissue. It was hypothesized that successively applied iFU pulses will generate sensation in inflamed tissue at a lower intensity and dose than application of a single iFU pulse. This hypothesis was tested using an animal model of chronic inflammatory pain, created by injecting an irritant into the rat hind paw. Ultrasound pulses were applied in rapid succession or individually to rats' rear paws beginning at low peak intensities and progressing to higher peak intensities, until the rats withdrew their paws immediately after iFU application. Focused ultrasound protocols consisting of successively and rapidly applied pulses elicited inflamed paw withdrawal at lower intensity and estimated tissue displacement values than single pulse protocols. However, both successively applied pulses and single pulses produced comparable threshold acoustic dose values and estimates of temperature increases. This raises the possibility that temperature increase contributed to paw withdrawal after rapid iFU stimulation. While iFU-induction of temporal summation may also play a role, electrophysiological studies are necessary to tease out these potential contributors to iFU stimulation.
The Journal of the Acoustical Society of America 08/2013; 134(2):1521-9. DOI:10.1121/1.4812872 · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Object:
Surgical exposure of a peripheral nerve can be technically challenging, making the operation more extensive and time consuming, particularly in the treatment of small nerves with an anatomically variable position. This study describes the application of ultrasound to facilitate surgical access and localization of targeted peripheral nerves.
A preclinical feasibility study was performed at the University of Washington's Willed Body Program laboratory. Unembalmed cadavers were placed on the dissection table in positions mimicking those typically required for surgical access to specific nerves that can be challenging to localize. A high-frequency portable ultrasound system was used to identify the nerves. An extraneural injection of methylene blue immediately adjacent to the target nerve was performed under ultrasound guidance as the experimental nerve mapping procedure. Surgical dissections through a small skin incision parallel to skin tension lines were guided by the transducer position and angle. Success was determined by the accuracy and rapidity of surgical identification and exposure of the nerve.
Using ultrasound-guided mapping, all anticipated peripheral nerves were correctly identified via a direct approach from the skin incision. This was confirmed by performing an anatomical dissection to expose and identify the intended nerve and its relation to the injected methylene blue dye. In no case was intraneural injection of the dye observed.
Preoperative ultrasound-guided nerve mapping may be useful in facilitating surgical access to a targeted nerve and thereby minimizing tissue dissection and operating time.
Journal of Neurosurgery 07/2013; 119(3). DOI:10.3171/2013.5.JNS122243 · 3.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We tested the hypothesis that neuropathic tissue is more sensitive to stimulation by intense focused ultrasound (iFU) than control tissue. We created a diffusely neuropathic paw in rats via partial ligation of the sciatic nerve, whose sensitivity to iFU stimulation we compared with sham-surgery and normal control paws. We then applied increasing amounts of iFU (individual 0.2 s pulses at 1.15 MHz) to the rats' paws, assaying for their reliable withdrawal from that stimulation. Neuropathic rats preferentially withdrew their injured paw from iFU at smaller values of iFU intensity (84.2 W/cm(2) ± 25.5) than did sham surgery (97.7 W/cm(2) ± 11.9) and normal control (> 223 W/cm(2)) animals, with greater sensitivity and specificity (85% for neuropathic rats and 50% each of sham surgery and normal control rats). These results directly support our hypothesis as well as Gavrilov's idea that doctors may some day use iFU stimulation to diagnose patients with neuropathies.
Ultrasound in medicine & biology 01/2013; 39(1):111-6. DOI:10.1016/j.ultrasmedbio.2012.08.012 · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective:
Potential peripheral sources of pain from subcutaneous tissue can require invasive evocative tests for their localization and assessment. Here, we describe studies whose ultimate goal is development of a noninvasive evocative test for subcutaneous, painful tissue.
We used a rat model of a focal and subcutaneous neuroma to test the hypothesis that intense focused ultrasound can differentiate focal and subcutaneous neuropathic tissue from control tissue. To do so, we first applied intense focused ultrasound (2 MHz, with individual pulses of 0.1 second in duration) to the rat's neuroma while the rat was under light anesthesia. We started with low values of intensity, which we increased until intense focused ultrasound stimulation caused the rat to reliably flick its paw. We then applied that same intense focused ultrasound protocol to control tissue away from the neuroma and assayed for the rat's response to that stimulation.
Intense focused ultrasound of sufficient strength (I(SATA) of 600 +/- 160 W/cm(2) ) applied to the neuroma caused the rat to flick its paw, while the same intense focused ultrasound applied millimeters to a centimeter away failed to induce a paw flick.
Successful stimulation of the neuroma by intense focused ultrasound required colocalization of the neuroma and intense focused ultrasound supporting our hypothesis.
Pain Medicine 11/2012; 14(1). DOI:10.1111/j.1526-4637.2012.01510.x · 2.30 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective. The criterion commonly used to determine whether radiofrequency neurotomy may be recommended is based on patient-reported, short-term pain relief following facet block injections. This study evaluated the concordance between two commonly used outcomes for pain relief: the pain numerical rating scale (NRS) and the global perceived improvement (GPI) scale.
Design. This is a retrospective cohort study.
Methods. Data were obtained from a consecutive cohort of patients through a review of the electronic medical records, with the following inclusion criteria: medial branch facet blocks at either cervical or lumbar spinal regions.
Outcome Measures. Pain NRS (baseline, postprocedure, and hourly up to 6 hours) and GPI scale are expressed as percent improvement at 6 hours, relative to baseline.
Results. The percent improvement in pain NRS corresponded to 49%, 43%, 34%, 21%, and 36% for baseline vs immediately post-block, 1 hour, 3 hours, 6 hours and average of all postscores, respectively. Average GPI reported at 6 hours was 44%, and differed significantly only to the baseline vs 6 hours percent improvement on the NRS (P < 0.01). Multiple regression analysis indicated that there were no demographic or baseline factors that accounted for the discrepancy between GPI vs NRS.
Conclusions. Asking patients about their pain relief in retrospect can be misleading. It is possible that patients' report on the GPI is weighed by their total experience of pain reduction and retrospective recall. Therefore, when choosing to address percent improvement on NRS measures, it is important to take into account multiple instances of NRS measures following treatment.
Pain Medicine 07/2012; 13(9):1131-6. DOI:10.1111/j.1526-4637.2012.01442.x · 2.30 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: SUMMARY Ultrasound-guided procedures are well established and utilized in the regional anesthesia and radiology practice. Conversely, there have been considerable difficulties in implementation of ultrasound in pain medicine. Ultrasonography has to compete with the more established modalities such as fluoroscopy and computed tomography; however, ultrasound has the advantage of radiation safety and point-of care imaging. It also allows direct visualization of tissue planes, blood vessels and nerves. Ultrasound-guided spine interventions are technically feasible and reasonably accurate when validated with conventional radiological modalities. Epidural, zygapophysial joint and caudal injection techniques have been published. The main pitfall of the ultrasound-guided spinal procedures lies in the inability to diagnose intravascular injections. Future technological improvements will help to solve this problem. Diagnostic spinal sonography may also contribute to the practice of medicine helping in the clinical workup of scoliosis and paraspinal pathology.
[Show abstract][Hide abstract] ABSTRACT: The transversus abdominis plane (TAP) block is an established technique to manage post-cesarean delivery pain. Transversus abdominis plane blocks with a local anesthetic only offer no analgesic benefits compared with intrathecal morphine. Adjuvants to extend TAP block duration and possibly reduce wound hyperalgesia, known to be a risk factor for chronic pain, have not been studied. We hypothesized that a TAP block with clonidine will affect postsurgical wound hyperalgesia and improve pain outcomes.
Ninety women were randomly assigned to receive 1 of 3 TAP blocks after cesarean delivery: saline (placebo), bupivacaine (BupTAP), or bupivacaine + clonidine (CloTAP). The primary outcome was wound hyperalgesia index at 48 hours. Secondary outcomes included pain scores, analgesic consumption, and pain descriptors up to 12 months.
Wound hyperalgesia index at 48 hours (median [25th-75th percentiles]) was 1.07 (0.48-3.26) in the placebo group, 1.27 (0.59-2.95) in the BupTAP group, and 0.74 (0.09-2.25) in the CloTAP group (P = 0.48). Morphine request in the postanesthesia care unit was significantly higher in the placebo group compared with the other TAP groups (P = 0.01). Postoperative pain scores and requests for breakthrough medication at 48 hours (30% in the placebo group, 24% in the BupTAP group, and 12% in the CloTAP group, P = 0.25) or chronic pain descriptors reported up to 12 months did not differ significantly among groups.
Adding clonidine to a TAP block with bupivacaine did not affect wound hyperalgesia index and it did not improve short-term or long-term pain scores in women undergoing elective cesarean delivery. Further studies are warranted to determine the benefits of antihyperalgesic adjuvants in TAP solutions for specific individuals at risk for chronic pain.
Regional anesthesia and pain medicine 06/2012; 37(5):508-14. DOI:10.1097/AAP.0b013e318259ce35 · 3.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background: The suprascapular nerve block is frequently implemented to treat chronic shoulder pain. Although effective the nerve blockade provides only a short-term relief, and more compelling apaproaches have been investigated. Pulsed radiofrequency (pRF) has been anecdotally reported as safe and reliable method. However, formal efficacy study has not been published. Ostensibly evidence-based validation of a new method is necessary for both scholastic and practical purposes.
Methods: This study was designed as a randomized active placebo-control double-blind trial. Because of encountered difficulties in recruitment and high rate of dropout, the study was redesigned as to allow a smaller sample size and statistical analyses were performed utilizing the last observation carry forward method. Lidocaine injections alone or with combination of the pRF were performed. Participants were followed up during 6 months, and multiple subjective and objective outcome variables were recorded.
Results: Thirteen of 22 participants completed 6 months follow-up. Dropout rate was higher in the lidocaine group. A significant linear trend (P < 0.05) for improvement on the numeric rating scale, Shoulder Pain and Disability Index and Constant-Murley score was observed in the pRF group, but not in the lidocaine group. Patients in the pRF group were on average more satisfied than the lidocaine group at 1 month (P = 0.041) and at 3 months (P = 0.035).
Discussion: Considering limitations of the study design and statistics, it seems plausible to attribute better results in the pRF group to unique properties of this physical modality.
Pain Practice 05/2012; 13(2). DOI:10.1111/j.1533-2500.2012.00560.x · 2.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Quantifying pain through assay of a human's or animal's response to a known stimulus as a function of time of day is a critical means of advancing chronotherapeutic pain management. Current methods for quantifying pain, even in the context of etiologies involving deep tissue, generally involve stimulation by quantifiable means of either cutaneous (heat-lamp tests, electrical stimuli) or both cutaneous and subcutaneous tissue (von Frey hairs, tourniquets, etc.) or study of proxies for pain (such as stress, via assay of cortisol levels). In this study, we evaluate the usefulness of intense focused ultrasound (iFU), already shown to generate sensations and other biological effects deep to the skin, as a means of quantifying deep diurnal pain using a standard animal model of inflammation. Beginning 5days after injection of Complete Freund's Adjuvant into the plantar surface of the rat's right hind paw to induce inflammation, the rats were divided into two groups, the light-phase test group (09:00-18:00h) and the dark-phase test group (23:00-06:00h), both of which underwent iFU application deep to the skin. We used two classes of iFU protocol, motivated by the extant literature. One consisted of a single pulse (SP) lasting 0.375s. The other, a multiple pulse (MP) protocol, consisted of multiple iFU pulses each of length 0.075s spaced 0.075s apart. We found the night group's threshold for reliable paw withdrawal to be significantly higher than that of the day group as assayed by each iFU protocol. These results are consistent with the observation that the response to mechanical stimuli by humans and rodents display diurnal variations, as well as the ability of iFU to generate sensations via mechanical stimulation. Since iFU can provide a consistent method to quantify pain from deep, inflamed tissue, it may represent a useful adjunct to those studying diurnal pain associated with deep tissue as well as chronotherapeutics targeting that pain.