This study was funded by Boston Scientific Neuromodulation.

1. Introduction:
Spinal cord stimulation, or SCS, has been clinically applied since 1967, when Dr Norman Shealy first implanted stimulation electrodes over the dorsal columns in an attempt to provide relief for patients with chronic, intractable pain (Shealy et al., 1967). SCS is the clinical implementation of the Gate Theory, which posits that activation of large myelinated afferent nerves which mediate touch and pressure sensations, can inhibit, or "close the gate" on transmission of pain signals to higher centers in the brain (Melzack &amp; Wall, 1965). Technology for SCS has improved over the decades, with more reliable stimulation equipment better designed to stimulate the dorsal columns has evolved.
Key to these improvements has been an increased understanding of the neuroanatomy and neurophysiology of the spinal cord relevant to clinical electrical stimulation. This understanding has been advanced by computational modeling of SCS. Computational modeling of neurons has been used to understand basic mechanisms for neural stimulation since Hodgkin and Huxley's mathematical model was first described (Hodgkin and Huxley, 1952). Neural activity is modulated by electric fields applied as intracellular current injection and extracellular potential fields. Ranck qualitatively discussed how changes in the extracellular voltage in the vicinity of an axon cause some regions of the axon membrane to depolarize and others to hyperpolarize (Ranck, 1975).
A computational model for SCS was initially developed by Coburn and Sin (Coburn, 1980) and was significantly furthered by Holsheimer and colleagues, beginning with Struijk and Holsheimer's development of a three dimensional field model of SCS (Holsheimer and Struijk, 1988). Their computational model estimated the effect of anatomic parameters on the thresholds of dorsal column fibers (Struijk et al., 1992), predicted the potential location of excitation in dorsal root fibers (Struijk et al., 1993b), and analyzed the effect of CSF thickness (Struijk et al., 1993a) with clinical validations (He et al., 1994; Holsheimer et al., 1995a; Holsheimer et al., 1994). The model contributed significantly to design of stimulation lead design, suggesting optimal parameters for contact size and spacing (Holsheimer and Struijk, 1992; Holsheimer and Wesselink, 1997), to favor preferential stimulation of dorsal column fibers over root fibers (Holsheimer et al., 1995b).
2. Methods:
Mathematical Model Definition
A finite element mathematical (FEM) model was created of the low-thoracic spinal cord and its surrounding environment. The FEM model consisted of spinal cord white and gray matter, cerebrospinal fluid, dura, epidural space tissue, vertebral bone, and two cylindrical multicontact leads. Each lead consisted of eight cylindrical platinum-iridium contacts (conducting domains, 3mm length and 1.25 mm diameter), separated by 1mm lengths of insulating polymer (non-conducting domains, 1mm length). The leads were positioned dorsally, atop the dura, and symmetric, 1mm to each side of the midline of the spinal cord. In the model, the "thickness" of the cerebrospinal fluid layer between the contacts and the dorsal surface of the spinal cord (dCSF) was specified to be 3.2mm. The geometry of the model is illustrated in Figure 1A and electrical resistivities are given in Table I, values coming predominantly from the literature (Holsheimer, 2002; Wesselink et al., 1999). The volume was meshed with over 1 million nodes, with a high-density mesh in the region close to where electrodes are located as illustrated in Figure 1B.
<img src="/files/ftp_upload/2443/2443fig1.jpg" alt="Figure 1" /> 
Figure 1. Depiction of the mesh of the FEM for the spinal cord and multicontact lead. (A) Components and structure of model. (B) Model mesh - only the high density part is shown. The mesh was segmented into sections of variable node density: near the contacts (&le; 300 &mu;m); insulator, dura and spinal cord (&le; 750 &mu;m); epidural space (&le; 3000 &mu;m); and vertebral bone (&le; 5000 &mu;m).
<img src="/files/ftp_upload/2443/2443table1.jpg" alt="Table 1" /> 
Table 1. Resistivity values of the FEM domains (Holsheimer, 2002; Wesselink et al., 1999) and modification (epidural space) to match clinical data.
The spinal cord geometry (Figure 2) was created using a combination of features from relevant literature sources. The cross-section of the cord was derived from Kameyama et al., and the dorsal root (DR) trajectory of Struijk et al. was adopted (Kameyama et al., 1996; Struijk et al., 1993b). Dorsal column (DC) fibers were placed on regular grid of (200um for mediolateral direction and 100um dorsoventral direction; see Figure 2A) and projected in the rostrocaudal direction. Each DR was modeled as a larger diameter 'mother' fiber connected to bifurcated 'daughter' fibers of smaller diameter (Fig 2B).
 <img src="/files/ftp_upload/2443/2443fig2.jpg" alt="Figure 2" /> 
Figure 2. Structure of spinal cord model. (A) Transactional view of spinal cord and location of dorsal column fibers. (B) Dorsal roots are composed of a mother fiber and bifurcated daughter fibers. The trajectory of the mother fiber was digitized from Struijk 1993. (C) Three dimensional view of spinal cord and DR fibers.
Model Investigation
Once the leads were positioned within the model, the two types of stimulators were implemented by defining the currents for two parallel contacts. For a single source system, there were three possible methods to deliver current: a. the leftmost contact has all the current; b. the two contacts each deliver 50% of the current; c. the rightmost contact delivers all the current. We note here that the impedance of the two contacts is assumed equal, though this is unlikely to be true in clinical application.
For the multisource system, each contact was defined to have its own current source controllable in 1% incremental current changes between the contacts. In other words, if the total current delivered to the two contacts is 10mA, in the multisource system the current to each contact was specified to any fraction of the total, so long as the sum of the currents through each contact equal 10mA. For example, the leftmost contact might deliver 6.8 mA where the rightmost contact would then deliver 3.2 mA. For the multisource system, 100 fractional splits of current were programmed in this manner.
To calculate the region of activation within the dorsal columns by each system, an activating function analysis was performed. The activating function is an approximation of the change in the transmembrane potential when extracellular stimulating current is applied to neural tissue for a given electrode and fiber geometry. The region of activation was defined as the locus of fibers in the model where the activating function (or simply second difference of voltages along axon) exceeded a predetermined threshold (ex. 0.1mV/mm2). The central point of stimulation was defined and calculated as the geometric centroid of the 3-dimensional region of activation.
To determine stimulation amplitude, the two contacts were specified to be cathodes (50% and 50% negative potential on two contacts) in a monopolar configuration (sourced current delivered with equivalent current density from model borders). The stimulation amplitude was then iteratively increased until the first fiber activated was observed (this was always a dorsal column fiber). This first activation was assumed to correlate to first perception of paresthesia by a patient in the clinical setting. In the model, the current was then increased to 1.4*(mA to activate first fiber) and the centroid of the resulting region of activation was calculated. Centroids of all steering steps (100:0 to 0:100) were computed with amplitude determined in the previous step. Average resolution of centroid change was centroid location range divided by current steps. 

3. Outcome:
When steering stimulation mediolaterally between dual leads, the computational model predicts that a device with independent current sources for each contact can target more central points of stimulation on the dorsal column than a single source system (100 vs 3). As a result of this, the resolution of adjustment of the central point of stimulation is 30 um with a multisource system, an approximate 50-fold increase compared to single-source systems (see Figure 3).
<img src="/files/ftp_upload/2443/2443fig3.jpg" alt="Figure 3" /> 
Figure 3. The computational model makes the following predictions. A. Dual lead configuration: 2.0 mm separation between leads with monopole stimulation. B. Single source devices that provide a single, shared power source for all contacts can target three central points of stimulation when shifting stimulation mediolaterally (a step size of 1 mm on average with 2 mm lead separation). C: A device with a dedicated power source for each contact can target 100 central points laterally in the dorsal column when fractionalizing current in 1% increments, or 10 central points when fractionalizing in 10% increments (a step size of 0.02 mm for 1% steps and 0.2 mm for 10% steps on average).

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The authors are employees of Boston Scientific Neuromodulation.

The ability to center stimulation regions in the dorsal column with high resolution may allow for better optimization of paresthesia-pain overlap in patients. That is, in a given patient, the region of activation in the dorsal columns may be focused to maximize coverage of painful areas while minimizing side-effects (due to stimulation of undesired fibers, which may generate paresthesia in undesireable locations or create motor or autonomic effects).

<ul>
<li>NEURON (<a href="http://www.neuron.yale.edu">http://www.neuron.yale.edu</a>)</li>
<li>ANSYS (Canonsburg, PA, <a href="http://www.ansys.com">http://www.ansys.com</a>)</li>
<li>Matlab (Natick, MA, <a href="http://www.mathworks.com">http://www.mathworks.com</a>)</li>
</ul>

dorsal column steerability with dual parallel leads using dedicated power sources:  a computational model

In spinal cord stimulation (SCS), concordance of stimulation-induced paresthesia over painful body regions is a necessary condition for therapeutic efficacy. Since patient pain patterns can be unique, a common stimulation configuration is the placement of two leads in parallel in the dorsal epidural space. This construct provides flexibility in steering stimulation current mediolaterally over the dorsal column to achieve better pain-paresthesia overlap. Using a mathematical model with an accurate fiber diameter distribution, we studied the ability of dual parallel leads to steer stimulation between adjacent contacts on dual parallel leads using (1) a single source system, and (2) a multi-source system, with a dedicated current source for each contact. The volume conductor model of a low-thoracic spinal cord with epidurally-positioned dual parallel (2 mm separation) percutaneous leads was first created, and the electric field was calculated using ANSYS, a finite element modeling tool. The activating function for 10 um fibers was computed as the second difference of the extracellular potential along the nodes of Ranvier on the nerve fibers in the dorsal column. The volume of activation (VOA) and the central point of the VOA were computed using a predetermined threshold of the activating function. The model compared the field steering results with single source versus dedicated power source systems on dual 8-contact stimulation leads. The model predicted that the multi-source system can target more central points of stimulation on the dorsal column than a single source system (100 vs. 3) and the mean steering step for mediolateral steering is 0.02 mm for multi-source systems vs 1 mm for single source systems, a 50-fold improvement. The ability to center stimulation regions in the dorsal column with high resolution may allow for better optimization of paresthesia-pain overlap in patients.

Watch this Scientific Journal Video about Dorsal Column Steerability with Dual Parallel Leads using Dedicated Power Sources:  A Computational Model at JoVE.com

Dorsal Column Steerability with Dual Parallel Leads using Dedicated Power Sources:  A Computational Model

Using a mathematical model of spinal cord stimulation, we found that a multi-source system with independent power sources for each contact can target more central points of stimulation on the dorsal column (100 vs 3) and has 50-fold more field steering resolution (0.02mm vs 1mm) than a single-source system.

In spinal cord stimulation (SCS), concordance of stimulation-induced paresthesia over painful body regions is a necessary condition for therapeutic ...

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11.8K Views.  Neuromodulation. Using a mathematical model of spinal cord stimulation, we found that a multi-source system with independent power sources for each contact can target more central points of stimulation on the dorsal column (100 vs 3) and has 50-fold more field steering resolution (0.02mm vs 1mm) than a single-source system.

Video: Dorsal Column Steerability with Dual Parallel Leads using Dedicated Power Sources:  A Computational Model

A Novel Capsulorhexis Technique Using Shearing Forces with Cystotome

Purpose:
To demonstrate a capsulorhexis technique using predominantly shearing forces with a cystotome on a virtual reality simulator and on a human eye.
Method:
Our technique involves creating the initial anterior capsular tear with a cystotome to raise a flap. The flap left unfolded on the lens surface. The cystotome tip is tilted horizontally and is engaged on the flap near the leading edge of the tear. The cystotome is moved in a circular fashion to direct the vector forces. The loose flap is constantly swept towards the centre so that it does not obscure the view on the tearing edge.
Results:
Our technique has the advantage of reducing corneal wound distortion and subsequent anterior chamber collapse. The capsulorhexis flap is moved away from the tear leading edge allowing better visualisation of the direction of tear. This technique offers superior control of the capsulorhexis by allowing the surgeon to change the direction of the tear to achieve the desired capsulorhexis size.
Conclusions:
The EYESI Surgical Simulator is a realistic training platform for surgeons to practice complex capsulorhexis techniques. The shearing forces technique is a suitable alternative and in some cases a far better technique in achieving the desired capsulorhexis.

This video demonstrates a novel capsulorhexis technique in modern cataract surgery. Capsulorhexis is the most difficult and important part of phacoemulsification surgery.

Purpose:
To demonstrate a capsulorhexis technique using predominantly shearing forces with a cystotome on a virtual reality simulator and on a human eye....

In vivo Dual Substrate Bioluminescent Imaging

Our understanding of how and when breast cancer cells transit from established primary tumors to metastatic sites has increased at an exceptional rate since the advent of in vivo bioluminescent imaging technologies 1-3. Indeed, the ability to locate and quantify tumor growth longitudinally in a single cohort of animals to completion of the study as opposed to sacrificing individual groups of animals at specific assay times has revolutionized how researchers investigate breast cancer metastasis. Unfortunately, current methodologies preclude the real-time assessment of critical changes that transpire in cell signaling systems as breast cancer cells (i) evolve within primary tumors, (ii) disseminate throughout the body, and (iii) reinitiate proliferative programs at sites of a metastatic lesion. However, recent advancements in bioluminescent imaging now make it possible to simultaneously quantify specific spatiotemporal changes in gene expression as a function of tumor development and metastatic progression via the use of dual substrate luminescence reactions. To do so, researchers take advantage for two light-producing luciferase enzymes isolated from the firefly (Photinus pyralis) and sea pansy (Renilla reniformis), both of which react to mutually exclusive substrates that previously facilitated their wide-spread use in in vitro cell-based reporter gene assays 4. Here we demonstrate the in vivo utility of these two enzymes such that one luminescence reaction specifically marks the size and location of a developing tumor, while the second luminescent reaction serves as a means to visualize the activation status of specific signaling systems during distinct stages of tumor and metastasis development. Thus, the objectives of this study are two-fold. First, we will describe the steps necessary to construct dual bioluminescent reporter cell lines, as well as those needed to facilitate their use in visualizing the spatiotemporal regulation of gene expression during specific steps of the metastatic cascade. Using the 4T1 model of breast cancer metastasis, we show that the in vivo activity of a synthetic Smad Binding Element (SBE) promoter was decreased dramatically in pulmonary metastasis as compared to that measured in the primary tumor 4-6. Recently, breast cancer metastasis was shown to be regulated by changes within the primary tumor microenvironment and reactive stroma, including those occurring in fibroblasts and infiltrating immune cells 7-9. Thus, our second objective will be to demonstrate the utility of dual bioluminescent techniques in monitoring the growth and localization of two unique cell populations harbored within a single animal during breast cancer growth and metastasis.

In vivo Dual Substrate Bioluminescent Imaging

Herein we describe the methods to construct, visualize, and quantify the bioluminescent reactions of both firefly and renilla luciferase enzymes expressed in metastatic breast cancer cells during their growth and metastasis in vivo.

Our understanding of how and when breast cancer cells transit from established primary tumors to metastatic sites has increased at an exceptional rate ...

Deep Neuromuscular Blockade Leads to a Larger Intraabdominal Volume During Laparoscopy

Shoulder pain is a commonly reported symptom following laparoscopic procedures such as myomectomy or hysterectomy, and recent studies have shown that lowering the insufflation pressure during surgery may reduce the risk of post-operative pain. In this pilot study, a method is presented for measuring the intra-abdominal space available to the surgeon during laproscopy, in order to examine whether the relaxation produced by deep neuromuscular blockade can increase the working surgical space sufficiently to permit a reduction in the CO2 insufflation pressure. Using the laproscopic grasper, the distance from the promontory to the skin is measured at two different insufflation pressures: 8 mm Hg and 12 mm Hg. After the initial measurements, a neuromuscular blocking agent (rocuronium) is administered to the patient and the intra-abdominal volume is measured again. Pilot data collected from 15 patients shows that the intra-abdominal space at 8 mm Hg with blockade is comparable to the intra-abdominal space measured at 12 mm Hg without blockade. The impact of neuromuscular blockade was not correlated with patient height, weight, BMI, and age. Thus, using neuromuscular blockade to maintain a steady volume while reducing insufflation pressure may produce improved patient outcomes.

This article presents a method for measuring the working abdominal volume during laproscopic myomectomy using the surgical grasper, and applies this technique to obtain pilot data on whether deep neuromuscular blockade (NMB) can enable the use of lower insufflation pressure. Reduced insufflation pressure during laproscopic surgery has been shown to reduce post-operative pain, and thus the use of NMB during surgery may enable improved patient outcomes.

Shoulder pain is a commonly reported symptom following laparoscopic procedures such as myomectomy or hysterectomy, and recent studies have shown that ...

Ischemic Tissue Injury in the Dorsal Skinfold Chamber of the Mouse: A Skin Flap Model to Investigate Acute Persistent Ischemia

Despite profound expertise and advanced surgical techniques, ischemia-induced complications ranging from wound breakdown to extensive tissue necrosis are still occurring, particularly in reconstructive flap surgery. Multiple experimental flap models have been developed to analyze underlying causes and mechanisms and to investigate treatment strategies to prevent ischemic complications. The limiting factor of most models is the lacking possibility to directly and repetitively visualize microvascular architecture and hemodynamics. The goal of the protocol was to present a well-established mouse model affiliating these before mentioned lacking elements. Harder et al. have developed a model of a musculocutaneous flap with a random perfusion pattern that undergoes acute persistent ischemia and results in ~50% necrosis after 10 days if kept untreated. With the aid of intravital epi-fluorescence microscopy, this chamber model allows repetitive visualization of morphology and hemodynamics in different regions of interest over time. Associated processes such as apoptosis, inflammation, microvascular leakage and angiogenesis can be investigated and correlated to immunohistochemical and molecular protein assays. To date, the model has proven feasibility and reproducibility in several published experimental studies investigating the effect of pre-, peri- and postconditioning of ischemically challenged tissue.

The window of the murine dorsal skinfold chamber presented visualizes a zone of acute persistent ischemia of a musculocutaneous flap. Intravital epi-fluorescence microscopy permits for direct and repetitive assessment of the microvasculature and quantification of hemodynamics. Morphologic and hemodynamic results can further be correlated with histological and molecular analyses.

Despite profound expertise and advanced surgical techniques, ischemia-induced complications ranging from wound breakdown to extensive tissue necrosis are ...

Using Saccadometry with Deep Brain Stimulation to Study Normal and Pathological Brain Function

The oculomotor system involves a large number of brain areas including parts of the basal ganglia, and various neurodegenerative diseases including Parkinson's and Huntington's can disrupt it. People with Parkinson's disease, for example, tend to have increased saccadic latencies. Consequently, the quantitative measurement of saccadic eye movements has received considerable attention as a potential biomarker for neurodegenerative conditions. A lot more can be learned about the brain in both health and disease by observing what happens to eye movements when the function of specific brain areas is perturbed. Deep brain stimulation is a surgical intervention used for the management of a range of neurological conditions including Parkinson's disease, in which stimulating electrodes are placed in specific brain areas including several sites in the basal ganglia. Eye movement measurements can then be made with the stimulator systems both off and on and the results compared. With suitable experimental design, this approach can be used to study the pathophysiology of the disease being treated, the mechanism by which DBS exerts it beneficial effects, and even aspects of normal neurophysiology.

This paper describes the use of quantitative measurement of eye movements in conjunction with stimulation of focal areas of the deep brain in order to study physiology, pathophysiology, and the mechanisms of deep brain stimulation.

The oculomotor system involves a large number of brain areas including parts of the basal ganglia, and various neurodegenerative diseases including ...

Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and drugs. It is widely used in many studies on the physiological functions of vascular smooth muscle, the pathogenesis of vascular diseases such as hypertension, and the development of smooth muscle relaxant drugs. The mouse is a widely used model animal with a large pool of disease models and genetically modified strains. We introduced this method to measure the isometric contraction of mouse mesenteric artery in detail. A 1.4-mm segment of mouse mesenteric resistance artery was isolated and mounted on a myograph chamber by passing two steel wires through its lumen. After equilibration and normalization steps, the vessel segment was potentiated by a high-K+ solution twice prior to the contraction assay. As an example of the application of this method in drug development, we measured the relaxant effect of a novel natural substance, neoliensinine, isolated from a Chinese herb, embryos of the lotus seed (Nelumbo nucifera Gaertn.) on mouse mesenteric arteries. The vessel segments mounted on the myograph chamber were stimulated with a high-K+ solution. When the force tension reached a stable sustained phase, cumulative doses of neoliensinine were added to the chamber. We found that neoliensinine had a dose-dependent relaxant effect on smooth muscle contraction, thus suggesting that it bears potential activity against hypertension. In addition, as the vessel segment can survive at least 4 hours after mounting and maintain contractility induced by the high-K+ solution for many times, we suggest that the wire myograph system may be used for the time-consuming process of drug screening.

The wire myograph technique is used to investigate vascular smooth muscle functions and screen new drugs. We report a detailed protocol for measuring the isometric contractility of the mouse mesenteric artery and for screening new relaxants of vascular smooth muscle.

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and ...

Murine Model of Central Venous Stenosis using Aortocaval Fistula with an Outflow Stenosis

Central venous stenosis is an important entity contributing to arteriovenous fistula (AVF) failure. A murine AVF model was modified to create a partial ligation of the inferior vena cava (IVC) in the outflow of the fistula, mimicking central venous stenosis. Technical aspects of this model are introduced. The aorta and IVC are exposed, following an abdominal incision. The infra-renal aorta and IVC are dissected for proximal clamping, and the distal aorta is exposed for puncture. The IVC at the midpoint between the left renal vein and the aortic bifurcation is carefully dissected to place an 8-0 suture beneath the IVC. After clamping the aorta and IVC, an AVF is created by puncturing the infra-renal aorta through both walls into the IVC with a 25 G needle, followed by ligating a 22 G intra-venous (IV) catheter and IVC together. The catheter is then removed, creating a reproducible venous stenosis without occlusion. The aorta and IVC are unclamped after confirming primary hemostasis. This novel model of central vein stenosis is easy to perform, reproducible, and will facilitate studies on AVF failure.

An aortocaval fistula was created by puncturing the murine infra-renal aorta through both walls into the inferior vena cava and was followed by creation of a stenosis in its outflow via partial ligation of the inferior vena cava. This reproducible model can be used to study central venous stenosis.

Central venous stenosis is an important entity contributing to arteriovenous fistula (AVF) failure. A murine AVF model was modified to create a partial ...

A Porcine Corneal Endothelial Organ Culture Model Using Split Corneal Buttons

Experimental research on corneal endothelial cells is associated with several difficulties. Human donor corneas are scarce and rarely available for experimental investigations as they are normally needed for transplantation. Endothelial cell cultures often do not translate well to in vivo situations. Due to the biostructural characteristics of non-human corneas, stromal swelling during cultivation induces substantial corneal endothelial cell loss, which makes it difficult to perform cultivation for an extended period of time. Deswelling agents such as dextran are used to counteract this response. However, they also cause significant endothelial cell loss. Therefore, an ex vivo organ culture model not requiring deswelling agents was established. Pig eyes from a local slaughterhouse were used to prepare split corneal buttons. After partial corneal trephination, the outer layers of the cornea (epithelium, bowman layer, parts of the stroma) were removed. This significantly reduces corneal endothelial cell loss induced by massive stromal swelling and Descemet&#39;s membrane folding throughout longer cultivation periods and improves general preservation of the endothelial cell layer. Subsequent complete corneal trephination was followed by the removal of the split corneal button from the remaining eye bulb and cultivation. Endothelial cell density was assessed at follow-up times of up to 15 days after preparation (i.e., days 1, 8, 15) using light microscopy. The preparation technique used allows a better preservation of the endothelial cell layer enabled by less stromal tissue swelling, which results in slow and linear decline rates in split corneal buttons comparable to human donor corneas. As this standardized organo-typically cultivated research model for the first time allows a stable cultivation for at least two weeks, it is a valuable alternative to human donor corneas for future investigations of various external factors with regards to their effects on the corneal endothelium.

Here, a step-by-step protocol for the preparation and cultivation of porcine split corneal buttons is presented. As this organo-typically cultivated organ culture model shows cell death rates within 15 days, comparable to human donor corneas, it represents the first model allowing long-term cultivation of non-human corneas without adding toxic dextran.

Experimental research on corneal endothelial cells is associated with several difficulties. Human donor corneas are scarce and rarely available for ...

In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy

Several hip pathologies have been attributed to abnormal morphology with an underlying assumption of aberrant biomechanics. However, structure-function relationships at the joint level remain challenging to quantify due to difficulties in accurately measuring dynamic joint motion. The soft tissue artifact errors inherent in optical skin marker motion capture are exacerbated by the depth of the hip joint within the body and the large mass of soft tissue surrounding the joint. Thus, the complex relationship between bone shape and hip joint kinematics is more difficult to study accurately than in other joints. Herein, a protocol incorporating computed tomography (CT) arthrography, three-dimensional (3D) reconstruction of volumetric images, dual fluoroscopy, and optical motion capture to accurately measure the dynamic motion of the hip joint is presented. The technical and clinical studies that have applied dual fluoroscopy to study form-function relationships of the hip using this protocol are summarized, and the specific steps and future considerations for data acquisition, processing, and analysis are described.

In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy

Dual fluoroscopy accurately captures in vivo dynamic motion of human joints, which can be visualized relative to reconstructed anatomy (e.g., arthrokinematics). Herein, a detailed protocol to quantify hip arthrokinematics during weight-bearing activities of daily living is presented, including the integration of dual fluoroscopy with traditional skin marker motion capture.

Several hip pathologies have been attributed to abnormal morphology with an underlying assumption of aberrant biomechanics. However, structure-function ...

Modified Posterior Vertebral Column Resection for Patients with Thoracolumbar Kyphotic Deformity

Old compression vertebrae fracture or congenital kyphoscoliosis with abnormal vertebral body development and other diseases that invade the spine may cause severe thoracolumbar kyphotic deformity, often accompanied by intractable low back pain or compression of the spinal cord, leading to severe neurological symptoms or even paralysis. If conservative treatment cannot relieve the symptoms or correct the deformities, surgical treatment is usually needed. For severe kyphotic deformity, reconstruction of the physiological curvature and rigid fixation determine the prognosis of the patients. Osteotomy and orthopedics are the standard procedure for deformities with severe compression of the front and middle column, but the trauma to the patients is high, with a long operation time and massive blood loss. To avoid these disadvantages, we have developed a modified technique to remove the diseased vertebra unilaterally. In this technique, we use a modified trephine to resect the vertebral columns like in the pedicle screw technique by adding a locking instrument that can restrict the trephine to lower the risk of osteotomy and shorten the surgery time and blood loss.

We describe a modified technique for resecting the posterior vertebral column unilaterally based on a modified trephine for patients with thoracolumbar kyphotic deformity.

Old compression vertebrae fracture or congenital kyphoscoliosis with abnormal vertebral body development and other diseases that invade the spine may ...

Dorsal Column Steerability with Dual Parallel Leads using Dedicated Power Sources: A Computational Model

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Using Saccadometry with Deep Brain Stimulation to Study Normal and Pathological Brain Function

Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography

Murine Model of Central Venous Stenosis using Aortocaval Fistula with an Outflow Stenosis

A Porcine Corneal Endothelial Organ Culture Model Using Split Corneal Buttons

In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy

Modified Posterior Vertebral Column Resection for Patients with Thoracolumbar Kyphotic Deformity