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Cardiovascular

2009;():1-2. doi:10.1115/BioMed2009-83022.

To assess shear stress in the tortuous and dynamic arterial circulation, we developed polymer- and catheter-based sensors that are both flexible and deployable. The flexible MEMS device provides an entry point to address spatial and temporal components of shear stress in the complicated arterial configuration. Theoretical and Computational Fluid Dynamics (CFD) analyses were performed. Fluoroscope and angiogram provided the geometry of aorta, and the Doppler ultrasound provided the pulsatile velocity for the boundary conditions. The development of micro electro mechanical systems (MEMS) and nano-scale sensors in our group have provided a means to undertake study of atherogenic hemodynamics and vascular oxidative stress in localizing early atherosclerosis.

Commentary by Dr. Valentin Fuster
2009;():3-4. doi:10.1115/BioMed2009-83048.

A thin film nitinol covered endograft for vessel treatment was manufactured and in vivo swine testing was performed. Thin film nitinol graft material was fabricated by DC sputter deposition and stress-strain behavior and DSC characteristics were investigated. Micro size patterns were fabricated by MEMS technology in order to promote endothelial layer growth. In-vivo studies in swine were conducted to evaluate deployment, placement and patency of the implanted stent device.

Commentary by Dr. Valentin Fuster

Orthopedics

2009;():5-6. doi:10.1115/BioMed2009-83011.

Paradoxical anterior translation of the femur (undesirable anterior motion of the femoral side of the knee relative to the tibia) has been observed in patients with posterior cruciate ligament (PCL) retaining total knee devices in which the ACL is absent. Simulations of a double leg squat of several total knee implant designs were compared using measurements of tibio-femoral ‘contact positions’ similar to those published in fluoroscopic studies. The objective of the study was to examine if a femoral design with a single axis (single radius) of curvature in the para-sagittal plane undergoes paradoxical anterior translation in the same way as femoral designs with polycentric (multi-radius) geometry.

Commentary by Dr. Valentin Fuster
2009;():7-8. doi:10.1115/BioMed2009-83015.

Spondylolysis is a defect in the vertebral pars interarticularis. Its cause may be developmental or due to mechanical etiologies such as trauma. Most childhood and adolescent spondylolisthesis (defined as a slip of one vertebrae relative to another) is associated with spondylolysis of the pars interarticularis at the L5–S1 motion segment.

Topics: Motion , Stiffness
Commentary by Dr. Valentin Fuster
2009;():9-10. doi:10.1115/BioMed2009-83038.

The process of using activities of daily living to evaluate the performance of implantable devices under physiological loading conditions has been researched [1,2,3,4]. In particular, long-term stability of hip-implants, as related to fatigue, have been evaluated using normal walking [1,2,4], sit to stand [1], stair climbing [2,4], and combinations of everyday activities [3]. Current methods that utilize estimated physiological loading conditions are traditionally used as pass/fail tests to identify whether a particular design performs to a set of minimum specifications for long-term use. Such tests are also traditionally limited to a small number of physiologically representative loading conditions (i.e. walking, stair climbing, sit-to-stand).

Commentary by Dr. Valentin Fuster
2009;():11-12. doi:10.1115/BioMed2009-83047.

One of the popular methods of treating lumbar spine pathologies involves a posterior lumbar interbody fusion (PLIF) using bilateral interbody non-expandable cages. Due to the geometry of these cages, they can require extensive bony removal and nerve root retraction. Some resultant risks of the procedure include dural lacerations and post-operative neuropraxia. Expandable interbody cages may address some of these concerns and possibly decrease the risks associated with PLIF procedures. This is the first study to our knowledge evaluating the biomechanical characteristics of an expandable lumbar interbody device in a cadaveric human spine model. The objective of this study was to evaluate the biomechanical characteristics of a new expandable interbody cage in single segment posterior lumbar interbody fusion using cadaveric lumbar spines.

Topics: Biomechanics
Commentary by Dr. Valentin Fuster
2009;():13-14. doi:10.1115/BioMed2009-83056.

Rotator cuff tears can be the source of significant morbidity. Impingement syndrome involving repetitive and prolonged mechanical irritation of the rotator cuff against the roof of the shoulder creates a progression of disease. Chronic tendon inflammation can lead to structural loss of integrity, leading to partial tears, and if left unchecked, full-thickness tears. Currently, the surgeon has the ability to repair full-thickness tears using minimally invasive techniques. However, the persistent tear rate after repair is remarkably high, more than 50% in some studies. One surgical goal is to alter progression of disease, and repair partial-thickness tears, for example. Another goal is to optimize the healing environment with the repair construct itself, accounting for biomechanical considerations. When using an arthroscopic approach, the challenges for treating partial- versus full-thickness tears varies significantly given anatomic restrictions—particularly, during repair of partial-thickness tears, the surgeon is “blind” for portions of the procedure as the arthroscope is typically placed intra-articularly, while instruments are passed from above the tendon, extra-articularly. Ideally, new technologies can be developed to optimize rotator cuff repair and healing in this setting.

Topics: Arthroscopy
Commentary by Dr. Valentin Fuster
2009;():15-16. doi:10.1115/BioMed2009-83057.

Due to the ever increasing number of total hip arthroplasties performed every year, the loading conditions typically experienced by a patient during the activities of everyday living must be accounted for in both the design and testing of an artificial joint (5). The probability of implant failure must constantly be addressed. Further, knowledge of these loading conditions may be applied to accidental events such as motor vehicle impacts to determine the potential for failure of a total hip arthroplasty during such “abnormal” occurrences. Specifically, when considering loading conditions experienced during a motor vehicle accident, one could determine if the failure of an implant was due to the inadequacy of the implant, the failure of the bone around the implant, or a pre-existing degraded condition in the implant-bone construct. The goal of this presentation is to provide an outline of the types of data and analyses that are necessary to determine the nature of a failed total hip arthroplasty subsequent to a frontal motor vehicle impact. These include data from the patient’s medical records, biomechanical properties of bone, structural and material properties of implant materials, and accident vehicle dynamics. This information may then be consolidated and analyzed in a flowchart fashion to provide a most probable cause of implant failure.

Commentary by Dr. Valentin Fuster
2009;():17-18. doi:10.1115/BioMed2009-83058.

Recently, there has been considerable interest in the ability to repair the rotator cuff tendon to its anatomic site along the articular margin of the footprint for either double row repairs or with a PASTA lesion. Unfortunately, this can often be difficult to perform since it requires placing a fixation device at the articular margin and then bringing sutures through the rotator cuff tendon. A new technology allows for easy piercing of the rotator cuff tendon under direct visualization with simultaneous placement of the anchoring device. The second preloaded anchor can then be used to create a suture bridge over the tendon for tensioning and eventual security without tying knots. We hypothesized that suture staple double row repair with a knotless anchoring system along with a traditional lateral row fixation has similar biomechanical characteristics to the TOE rotator cuff repair. Therefore, the objective of this study was to quantify and compare the biomechanical characteristics of a knotless suture staple double row (SSDR) repair and transosseous equivalent (TOE) rotator cuff repair using matched pair shoulders.

Topics: Maintenance
Commentary by Dr. Valentin Fuster
2009;():19-20. doi:10.1115/BioMed2009-83059.

Injury to the cervical spine can be debilitating injury. Fracture the Dens of the C1-C2 motion segment can lead to gross instability of the cervical spine and neurological deficit. It is important to achieve stability operatively. Posterior fusion is considered by some to be a relatively safe operation compared to other procedures. Any spinal surgery which relies on boney stabilization post-operatively must provide a sufficiently small amount of movement initially to allow bone consolidation and healing.

Topics: Cervical spine
Commentary by Dr. Valentin Fuster
2009;():21-22. doi:10.1115/BioMed2009-83061.

Hip Arthroscopy is the most rapidly growing field in Orthopaedic Surgery. The volume of hip arthroscopy has tripled since 2003. Yet, despite the rapid recent growth, it is felt that only 10% of problems that can be treated with hip arthroscopy are currently being done so. The reasons for this are multiple — lack of recognition of problems in the hip by those not experienced with non-arthritic hip problems, insufficient numbers of surgeons trained to do hip arthroscopy, and, not unimportantly, the difficulty of performing hip arthroscopy. One of the most common underlying problems affecting individuals with non-arthritic hip pain is femoroacetabular impingement (FAI). FAI was first described by Ganz in the Swiss literature in 1995, and did not make it into the English literature until 1999. Due to its very recent identification, acceptance of this problem and dissemination to clinicians has resulted in a relatively low number of clinicians being aware of this problem.

Commentary by Dr. Valentin Fuster
2009;():23-24. doi:10.1115/BioMed2009-83064.

The analysis of motor vehicle impacts and the resulting injury exposure to occupants with artificial joints can be correlated to a parameter referred to as delta-v. The delta-v of a vehicle involved in a motor vehicle impact is defined as the change of velocity of the vehicle at its center of gravity during impact. The delta-v is a function of the closing speed between the two vehicles and the mass of each vehicle. A general formula for delta-v is as follows:

ΔVi=(1+ε)·(mj/(mi+mj))·Vc
Where: Vc – closing speed between the two vehicles; ε – coefficient of restitution; m – mass of each vehicle.

Commentary by Dr. Valentin Fuster
2009;():25-26. doi:10.1115/BioMed2009-83065.

Satisfactory outcome of intraarticular distal humerus fractures depends on anatomic joint restoration and stable fracture fixation to allow early motion. Orthogonal constructs (medial plate on medial column and posterior plate on lateral column) and parallel constructs (medial plate on medial column and lateral plate on lateral column) have been proposed for fixation of these fractures. However, the optimal configuration remains controversial. There are no clinical studies comparing these constructs and existing biomechanical studies had methodological limitations and reported conflicting results.

Commentary by Dr. Valentin Fuster
2009;():27-28. doi:10.1115/BioMed2009-83069.

Kneeling is an activity that is important in certain occupations and recreational activities. Culturally, kneeling plays a large role in Middle Eastern and Asian countries, where activities of daily living require the ability to kneel and achieve deep knee flexion.

Commentary by Dr. Valentin Fuster
2009;():29-30. doi:10.1115/BioMed2009-83070.

Shoulder arthroplasty is a reliable procedure used to treat glenohumeral arthritis thanks to the efforts of many orthopaedic surgeons and design engineers over the past thirty years. Surgeons such Drs. Charles Neer and Robert Cofield were instrumental to making clinical observations that were effectively translated into improving implant design and clinical outcomes. Yet, there remains much room for further growth and development. With the increase numbers of shoulder arthroplasties performed, new observations and problems have been recognized that remain unanswered.

Topics: Arthroplasty
Commentary by Dr. Valentin Fuster
2009;():31. doi:10.1115/BioMed2009-83071.
FREE TO VIEW

Sports medicine/joint preservation represents one of the fastest growing segments of orthopedic markets. It is estimated that the frequency of rotator cuff repair alone is increasing between 10 and 20% per year. Similar to the ongoing evolution in other medical specialties (cardiology, general surgery), an increasing number of joint preservation procedures are transitioning to less invasive techniques. However, there are significant unmet needs as soft tissue repair transitions from invasive open surgical techniques to less invasive arthroscopic methods.

Topics: Soft tissues
Commentary by Dr. Valentin Fuster
2009;():33. doi:10.1115/BioMed2009-83072.
FREE TO VIEW

This talk will discuss venture capital trends globally and specifically how these trends are impacting the orthopedic market. The discussion will include: a. Current areas of interest in the venture community — i. Spin, ii. Knee/Hip, iii. Extremities/Small Bone; b. Choosing a financial partner; c. How to approach venture firms — i. Stage focus and how it impacts the entrepreneur, ii. General investment criteria; d. Making the pitch — i. How to make contact, ii. Key content/format, iii. Who is going to read what?, iv. Preparing for success, v. Market size, vi. Team, vii. Cap table, viii. All about milestones; e. Alternative funding sources; f. The costs associated with other people’s money.

Commentary by Dr. Valentin Fuster
2009;():35. doi:10.1115/BioMed2009-83073.
FREE TO VIEW

Marketing, Sales, and Commercialization: Marketing and sales of orthopaedic medical devices are two of the most challenging and costly aspects of a successful commercial product launch. Many companies have developed an innovative product, filed for patents, passed through regulatory hurdles, and yet ultimately failed because of an inadequate marketing and sales plan. Invariably product launches cost more money and take longer to get off the ground than most companies forecast.

Commentary by Dr. Valentin Fuster
2009;():37. doi:10.1115/BioMed2009-83074.
FREE TO VIEW

OVERVIEW: a. The Art of Regulatory Science. What engineers should know about the regulatory process. Getting your class 1 or 2 device market cleared in the US. b. What about Europe. CE mark, Notified Bodies, Competent Authorities and other interesting facts. c. Regulatory pitfalls.

Commentary by Dr. Valentin Fuster
2009;():39. doi:10.1115/BioMed2009-83075.
FREE TO VIEW

Everyday, people are inventing new products with hopes of someday bringing the products to the marketplace. Often times, people believe their new products are so innovative that they can potentially revolutionize an entire industry. Many entrepreneurs dream of starting new companies founded on their inventive products, and some may even succeed.

Commentary by Dr. Valentin Fuster
2009;():41. doi:10.1115/BioMed2009-83076.
FREE TO VIEW

Development: This presentation will discuss approaches to vetting new ideas for soft tissue fixation, establishing a concept to pursue, and moving a concept into new product development.

Topics: Soft tissues
Commentary by Dr. Valentin Fuster
2009;():43. doi:10.1115/BioMed2009-83077.
FREE TO VIEW

Provide an introduction and overview of the major aspects and challenges of bringing a new spinal implant or product from concept to market.

Commentary by Dr. Valentin Fuster
2009;():45-46. doi:10.1115/BioMed2009-83078.

The purpose of this presentation is to discus the current state of the art in spine testing technology to aide the audience in planning and evaluating spine and spine implant testing.

Commentary by Dr. Valentin Fuster
2009;():47-48. doi:10.1115/BioMed2009-83079.

Once thought to be a functionless, vestigial structure, the meniscus is known to be an important load bearing and shock-absorbing structure in the knee. The lateral meniscus absorbs 70% of the load in the lateral compartment and the medial meniscus absorbs 50% of the load in the medial compartment. In addition, it has a secondary role in stabilization of the knee in conjunction with the major ligamentous restraints. Vascular supply to the meniscus is provided by branches from the geniculate arteries that penetrate into approximately 10–30% of its periphery through permeniscal capillary channels (Figure I). The remainder of the meniscus obtains nutrition through diffusion or mechanical pumping.

Topics: Wounds , Knee
Commentary by Dr. Valentin Fuster
2009;():49. doi:10.1115/BioMed2009-83080.
FREE TO VIEW

Presentation will review the epidemiology, risk factors and treatments of fractures of the pelvis and femur associated with total hip arthroplasty. The attendee will be exposed to classification systems and treatment rationale base on accepted criteria. Additionally the at risk patient will be clarified in respect to types of implants, duration of service and pathologic comorbidities.

Commentary by Dr. Valentin Fuster
2009;():51. doi:10.1115/BioMed2009-83081.
FREE TO VIEW

Ligament injuries in the knee are a common cause of disability in the active population. The advent of arthroscopy and arthroscopic surgical techniques has changed our ability to diagnose and treat these injuries. Arthroscopy has become the gold standard for diagnosis of intra-articular ligament injuries, as well as meniscal and articular cartilage pathology. It combines optimal visualization and the ability to manipulate tissue under anesthesia to best understand the degree of ligament injury and knee instability. Arthroscopy has also evolved into the primary means for the surgical treatment of injuries to intra-articular ligaments, articular cartilage, and meniscus.

Topics: Knee , Arthroscopy
Commentary by Dr. Valentin Fuster
2009;():53-54. doi:10.1115/BioMed2009-83083.

Articular cartilage is a unique biphasic tissue composed of chondrocytes surrounded by extracellular matrix (ECM). This thin layer of tissue covers the articular surface of diarthroidal joints and provides a durable, low friction interface which also helps to reduce the load transmitted to the underlying subchondral bone.

Topics: Wounds , Cartilage , Knee
Commentary by Dr. Valentin Fuster
2009;():55-56. doi:10.1115/BioMed2009-83093.

Key Questions — Learning Objectives: A. What has lead to the historical progress with rotator cuff repairs? B. Is there basic science supporting an “all-arthroscopic” rotator cuff repair? C. What are the future technologies that are promising to enhance rotator cuff healing?

Topics: Maintenance
Commentary by Dr. Valentin Fuster
2009;():57. doi:10.1115/BioMed2009-83095.
FREE TO VIEW

Intercarpal arthrodesis is a common motion sparring procedure for post-traumatic arthritis of the wrist. Untreated scaphoid non-union or scapholunate ligament injury often leads to progressive arthritis of the wrist that can be salvaged by proximal row carpectomy (PRC), limited intercarpal arthrodesis or total wrist fusion. Most surgeons elect to perform a motion sparring procedure in lieu of total wrist fusion. PRC is favored by many because of the ease of surgery and no need to obtain bony union. However, several reports are pessimistic about the out comes of the PRC operation in the long term. Most agree that the four corner arthrodesis with scaphoid excision is the optimal reconstruction to maintain wrist motion and strength and provide long-term durability.

Commentary by Dr. Valentin Fuster
2009;():59. doi:10.1115/BioMed2009-83096.
FREE TO VIEW

External fixation has been used for the treatment of distal radius fractures for more than 50 years. Although the fixator configurations have undergone considerable modification over time, the type of fixator itself is not as important as the underlying principles that provide the foundation of external fixation. Although volar plate fixation is currently in vogue, the indications for external fixation remain largely unchanged. New fixator designs have also expanded hrte traditional usage to include nonbridging applications that allow early wrist motion. The following discussion focuses on the myriad uses for external fixation as well as the shortcomings and potential pitfalls.

Commentary by Dr. Valentin Fuster
2009;():61-62. doi:10.1115/BioMed2009-83138.

Rotator cuff tears (RCT) commonly start at the anterior insertion of the supraspinatus and have been shown to propagate posteriorly. Early detection and repair of small or medium size tears has been shown to result in better clinical outcome and structural integrity than that of large or massive tears. However, it is unknown at which stage of rotator cuff tear propagation the biomechanical environment becomes altered. Previous biomechanical studies have not considered rotator cuff propagation based on the footprint anatomy, rotational glenohumeral joint kinematics, and the influence of anatomy-based muscle loading including pectoralis major and latissmus dorsi. Therefore, the purpose of this study was to determine the relationship between progressive rotator cuff tear and glenohumeral joint biomechanics using a rotator cuff tear progression model and anatomically based muscle loading including the influence of the pectoralis major and latissmus dorsi. Our hypotheses were 1) cuff tear progression will lead to abnormal glenohumeral joint biomechanics, specifically in kinematics (rotational range of motion and the path of humeral head apex) and abduction capability and 2) the pectoralis major and latissmus dorsi muscles will act as a stabilizer of the humeral head in large or massive tear.

Topics: Biomechanics , Muscle
Commentary by Dr. Valentin Fuster

Advanced Technology

2009;():63-64. doi:10.1115/BioMed2009-83004.

RF Ablation Efficacy Testing: Modern surgical techniques utilize radio frequency ablation tools in minimally invasive procedures around the world today. The safety and efficacy of these tools must be verified before being used in human trials. This verification is typically performed on bovine, ovine, or porcine tissues which simulate clinical use.

Commentary by Dr. Valentin Fuster
2009;():65. doi:10.1115/BioMed2009-83008.
FREE TO VIEW

Medical device developers frequently invest enormous amounts of money and inventor hours to develop and commercialize new devices and treatments. Once commercialized, however, these devices and treatments often can be duplicated by competitors for a fraction of the initial investments. A strong patent portfolio protects these investments by deterring the manufacture, sale, and importation of unauthorized duplications. In addition, a strong patent portfolio can capture venture capital interest and increase a company’s market value. Medical device developers should employ prudent defensive and offensive patent strategies during the early stages of product development. Such strategies not only provide for an effective defense against unauthorized product duplication but also increase the value of their products. This presentation will provide insights into building a strong patent portfolio that can withstand the attacks of competitors. In particular, this presentation will discuss various effective strategies that include: • Timely Invention Capture and Patent Filings — + Discover the activities that can cause an unintentional loss of patent rights and how to avoid them. + Learn the necessary recording and documentation of inventive activity needed to prevail in litigation. + Hear how patents can help you control a competitor’s ability to improve their products by obtaining blocking patents. • Creating a Valuable Application Disclosure — + Use your technical expertise to help your patent attorney fully disclose your invention and all conceivable variations and modifications. + Know why the Patent Office requires disclosing the “best” way of practicing your invention, and how failing to do so can affect your patent rights. • Obtaining Commercially Significant Claims — + Consider what it will take to prove infringement of your claims. + Ensure your claims target as many infringers as possible through the use of various claim types and scope. + Be certain your claims account for future improvements or “design-arounds” to your product. + Ensure your patent attorney is aware of the competition and has drafted claims that cover their devices and foreseeable enhancements. • Inventorship and Ownership — + Understand improper inventorship and how it can destroy patent rights. + Find out who is an “inventor” and how to determine inventorship. + Ensure your company owns the rights to a patent. • Avoiding Patent Procurement Pitfalls — + Learn about the Patent Office’s “Duty of Disclosure” and who must comply. + Ensure your compliance with the “Duty of Disclosure.” + Understand how inventor and corporate failure to comply with the “Duty of Disclosure” can destroy patent rights. In summary, building a strong patent portfolio in concert with a company’s business objectives is imperative in today’s technologically complex and rapidly changing economy. Many successful companies understand that a strong patent portfolio, which protects core technologies and contains offensive and defensive patents, can provide a competitive advantage in the marketplace. By employing the strategies in this presentation, a company can build a strong patent portfolio that reflects present and future business goals and enhances the value of the company.

Topics: Patents
Commentary by Dr. Valentin Fuster
2009;():67-68. doi:10.1115/BioMed2009-83020.

A novel piezo-driven micro-jet injection system is presented for transdermal drug delivery. The system uses an amplified piezoelectric actuator and a precision ball screw to accumulate the displacement of each pulsed injection. The device effectively eliminates the flow restrictor in the ampoule.

Commentary by Dr. Valentin Fuster
2009;():69-70. doi:10.1115/BioMed2009-83032.

This paper presents an overview of two advanced surface mechanical testing techniques: the instrumented indentation testing and the single point scratch testing techniques. Both can be used for studying bulk or thick materials, they are however powerful tools in the cases of thin layers and small features, elastic materials and surfaces with poor optical contrast. Most samples can be tested “as is” or with minimal preparation.

Commentary by Dr. Valentin Fuster
2009;():71-72. doi:10.1115/BioMed2009-83036.

There are approximately 65,000 patients on sustaining hemodialysis in the United States for renal disease. While hemodialysis is traditionally performed three times weekly, several studies have shown improved patient results with increased treatment frequency and shorter treatment time. A more portable hemodialysis treatment would represent an improvement over current treatments by giving patients the ability to dialyze at their convenience, and more often for shorter treatment times. A prototype wearable artificial kidney has been developed by Gura et al.

Topics: Design , Modeling , Kidney
Commentary by Dr. Valentin Fuster
2009;():73-74. doi:10.1115/BioMed2009-83051.

Microelectromechanical systems (MEMS) have great potential for use in gastrointestinal (GI) imaging. Ultrasound and magnetic resonant imaging can provide useful information about the GI tract, but only optical coherence tomography (OCT) delivered endoscopically can be used to perform an optical biopsy of the GI tissue. In monitoring a condition such as Barrett’s esophagus, which typically requires regular random biopsies, the ability to achieve an optical biopsy is indispensible. While the existing method for obtaining an optical biopsy of the GI tract tissue produces functional images, there are drawbacks that could be improved upon. The gear-and-shaft assembly used to couple force from the motor at the proximal end to the distal imaging end requires a complex design [1]. By introducing a rotational MEMS device into the distal imaging end, a rotating optical coupling joint is no longer required at the proximal end, there is no need to precisely align the fixed fiber with the rotational drive shaft, and the metallic reinforcement sleeve can be eliminated leaving a simpler, more flexible delivery method [2]. In order to produce 3D OCT images, displacement in the z-direction needs to be coupled with rotation. A MEMS device that can achieve both vertical displacement and rotation further increases the simplicity of the device and decreases potential alignment and coupling errors. Our MEMS devices needs to be able to bend an OCT beam of light 90°, rotate that beam of light 360°, and simultaneously scan in the z-direction in order to produce 3D OCT images. Also, the device must fit inside the 1 mm diameter available in the endoscope. To accomplish this, we have designed, and are continuing to develop, a paraffin actuated micro mirror. The thermal expansion properties of paraffin wax have often been utilized in MEMS devices [3, 4]. We have made use of these properties in designing a piston like actuator. Heat is applied to a reservoir of paraffin enclosed by a parylene membrane. The paraffin expands and pushes the post above it upward with the developed force from its expansion. The amount of paraffin in each reservoir is controlled by the reservoir’s geometry and so by controlling the amount of heat applied, we can control how far the post above it moves in the vertical direction. Each device has three heaters, three reservoirs, and three posts. All three posts are attached to a single mirror. By appropriately cycling the applied heat to each reservoir, we expect to be able to move the mirror in a spiral like fashion. This will bend an applied beam of light 90° and rotate it 360° while achieving displacement in the z-direction.

Commentary by Dr. Valentin Fuster
2009;():75-76. doi:10.1115/BioMed2009-83084.

In some cases an object can not be completely imaged with a single image. These cases call for taking multiple images and stitching the images together to form a complete view of the object. The images that are dealt with are taken with a confocal laser-scanning microscope. This produces a stack of two-dimensional images that represent the volume in the microscope’s field of view. While the microscope automatically creates a z stack, the positioning of the tiles in x and y is done manually. Therefore, the slices within each stack are assumed to be already aligned. Our technique will take multiple stacks of images and stitch them together to form a single volume. We will use a particle swarm optimization technique to calculate the proper transformations required to produce the final volume.

Commentary by Dr. Valentin Fuster

Posters

2009;():77-78. doi:10.1115/BioMed2009-83014.

Visualization of spinal pathologies such as scoliosis is imperative to proper surgical treatment. Current visualization techniques use 2D representations of the anatomy in the form of radiographs, CT, or MRI. The ability to view patient anatomy in three dimensions prior to surgical intervention allows for a more thorough evaluation and planning of the surgical requirements. Manufacturing methods such as three dimensional printing can be employed to rapidly generate a physical 3D representation of patient anatomy which can be used for visualization and/or surgical planning.

Commentary by Dr. Valentin Fuster
2009;():79-85. doi:10.1115/BioMed2009-83019.

Hypertension is a perplexing multiorgan disease involving renal primary pathology and enhanced angiotensin II vascular reactivity. Hypertension is more common and severe in diabetic patients, placing them at increased risk of cardiovascular disease, stroke and end-stage renal disease. Diarrhoea, constipation & epigastric pain are common complaints in type 2 diabetic patients with hypertension. Delayed gastric emptying and disturbance of intestinal motility are frequent findings in type 2 diabetic patients. Impaired intestinal motility is often followed by small intestinal bacterial overgrowth (SIBO). The prevalence of SIBO & its association with orocecal transit time has not yet been studied in diabetic patients with hypertension. Gastrointestinal abnormalities in diabetic patients with hypertension may disturb gastrointestinal (GI) motility and as a result SIBO. Therefore, this study was planned. In this study, 57 diabetic patients with hypertension and 72 diabetic patients (who had GI symptoms) between the age range 30–70 years were enrolled. One hundred age and sex matched healthy volunteers with normal bowel habits were also taken for this study. Small intestinal bacterial overgrowth & orocecal transit time were studied by using non-invasive glucose and lactulose hydrogen breath tests respectively. Out of 57 patients of type 2 diabetic mellitus with hypertension, 30 (52.6%) were the males while 27 out of 57 (47.4%) females. 39 out of 72 (54.2%) were the males while 33 out of 72 (45.8%) females. In control group, 56 out of 100 (56%) were males while 44 out of 100 (44%) females. Glucose hydrogen breath test was suggestive of SIBO in 7 out of 57 (12.3%) in patients with type 2 diabetic mellitus with hypertension and in 8 out of 72 (11.1%) in type 2 diabetic patients while in 1 out of 100 (1%) in controls. The difference was statistically significant between diabetic patients with hypertension vs controls and diabetic patients vs controls. Range of orocecal transit time was 150 to 255 minutes in patients of type 2 diabetic mellitus with hypertension, who were suggestive of bacterial overgrowth while 75–180 minutes in patients of type 2 diabetic mellitus with hypertension, who were negative for glucose H2BT. Range of orocecal transit time was 135 to 240 minutes in patients of type 2 diabetic mellitus, who were suggestive of bacterial overgrowth while 60–180 minutes in patients of type 2 diabetic mellitus, who were negative for glucose H2BT. In control group, the range of orocecal transit time was 60–120 minutes. It appears from the results obtained in this study that the orocecal transit time was delayed in patients of type 2 diabetic mellitus with hypertension, and patients with diabetic mellitus (who were suggestive of bacterial overgrowth) as compared to the patients of type 2 diabetic mellitus with hypertension and patients with diabetic mellitus, who have negative glucose H2BT. When the mean ± SD (145.26 ± 47.21 minutes) of orocecal transit time of all type 2 diabetic patients with hypertension and mean ± SD (136.32 ± 52.37 minutes) of type 2 diabetic patients was compared with the mean ± SD (90.41 ± 15.36 minutes) of controls, it was significantly delayed. It appears that the orocecal transit time in type 2 diabetic patients with hypertension, and patients with diabetic mellitus was significantly delayed (resulting to SIBO) as compared to controls. Thus these patients should be treated with prokinetic agents and antibiotics.

Topics: Diabetes
Commentary by Dr. Valentin Fuster
2009;():87-88. doi:10.1115/BioMed2009-83035.

Monodisperse micron-sized aerosol is ideal for pulmonary drug delivery. This paper reports delivery of monodisperse aerosol of medicinal droplets generated by MHz ultrasonic nozzles using an anatomically realistic upper airway model. The MHz ultrasonic nozzle is fabricated using MEMS technology, and comprised of a piezoelectric drive section and a silicon resonator of multiple Fourier horns (see Fig. 1) [1]. The dissolved medication is pumped into a central channel (200×200 μm2 ) inside the nozzle and exits at the nozzle tip that vibrates longitudinally at the nozzle resonant frequency. The novel design of multiple horns facilitates generation of a column of monodisperse droplets at electric drive power as low as 15mW [1]. Monodisperse ethanol droplets 2.4 μm and water droplets 4.5 μm in diameter have been produced, respectively, using 1.5 MHz and 1.0 MHz nozzles. We used an aqueous solution of 25mg/ml (2.5wt%) β2 -agonist (isoproterenol) for generation of monodisperse droplets using the 1.0 MHz ultrasonic nozzles. A yield of >54% (to the lower airways on total amount of inhaled isoproterenol basis), significantly higher than the reported highest lower airways deposition (32%) using metered-dose-inhalers (MDIs) [2], has been accomplished.

Topics: Aerosols , Nozzles , Silicon
Commentary by Dr. Valentin Fuster
2009;():89-92. doi:10.1115/BioMed2009-83042.

Epilepsy is characterized by unprovoked, recurring seizures that disrupt the nervous system and can cause mental and physical dysfunction. It affects all age groups. About 14% of epilepsy patients are under 15 years old and 24% are over 64, with 62% being between those ages. There is an increased risk of death due to accidents, suicide and other medical conditions. There are also cases where the death appears to be directly related to epilepsy itself, usually referred to as Sudden Unexpected Death in Epilepsy (SUDEP). This information is not always passed from doctor to patient, for various reasons. Epilepsy share is an uncontrolled electrical discharge from nerve cells in the cerebral cortex. This is the part of the brain that integrates higher mental functions, general movement, and the functions of the internal organs in the abdominal cavity, perception, and behavioral reactions. The early warning system will be based on three factors: 1. Detection of abnormal electrical activity of brain. 2. Detection of abnormal breathing (too fast or too slow) that almost always accompanies the onset of an attack. 3. Unusual sensations or movements of parts of body such as muscles relaxation and tightening.

Commentary by Dr. Valentin Fuster
2009;():93-94. doi:10.1115/BioMed2009-83052.

The TMJ is a bilateral joint of the jaw that functions as a single entity during normal masticatory activities, speaking, yawning and swallowing. TMJ replacement has been indicated in cases of joint trauma, advanced degenerative disease, tumors, developmental anomalies and ankylosis of the joint following injury. Alloplastic replacement of the TMJ (an artificial replacement in the form of a TMJ condylar implant with a glenoid fossa component that articulates with the undersurface of the skull on the temporal bone) renders the anatomical space devoid of the natural mandibular condyle (Fig. 1). Compared to hip and knee prostheses, TMJ implants have not been studied in detail. The goals of this study were to quantify the stress distribution in a commercially available TMJ implant (TMJ Implants, Inc, CO), bone and implant-bone interface, to compare the stresses and strains with different bone conditions, and to compare the stresses and strains with different implant materials using a finite element software package.

Commentary by Dr. Valentin Fuster
2009;():95-96. doi:10.1115/BioMed2009-83060.

The Charite III artificial disc replacement was approved for use in the United States in October of 2004 by the FDA. Another similarly designed lumbar disc replacement called the ProDisc II was also approved by the FDA a year later in January of 2006. The purpose of this study was to retrospectively review 29 patients with either the Charite III or the Prodisc II disc replacement surgery and complications.

Topics: Disks , Failure
Commentary by Dr. Valentin Fuster
2009;():97-98. doi:10.1115/BioMed2009-83062.

A transosseous-equivalent rotator cuff repair has shown improved biomechanical characteristics compared to other more cumbersome arthroscopic double row repairs. However, the transosseous equivalent repair, which requires knot tying, still can be challenging when tensioning the repair construct. We hypothesized that a knotless dual row loop repair has similar biomechanical characteristics to the transosseous-equivalent rotator cuff repair. Therefore, the objective of this study was to quantify and compare the biomechanical characteristics of a knotless double row repair and transosseous equivalent rotator cuff repair using matched pair shoulders.

Topics: Maintenance
Commentary by Dr. Valentin Fuster
2009;():99-100. doi:10.1115/BioMed2009-83066.

Unstable thoracolumbar burst fractures are serious injuries and their management remains controversial. Some authors advocate the use of short-segment posterior instrumentation (SSPI) for certain burst fractures which offers several benefits including preservation of motion segments; however, clinical studies have shown mixed results. Whether crosslinks contribute sufficient stability to this construct has not been determined, therefore the objective of this study was to evaluate the biomechanical characteristics of short-segment posterior instrumentation, with and without crosslinks, in an unstable human burst fracture model.

Commentary by Dr. Valentin Fuster
2009;():101-103. doi:10.1115/BioMed2009-83067.

Quantitative measurements of cell osmotic behavior and membrane transport properties is critical for the development of cell-type-specific, optimal cryopreservation conditions. A microfluidic perfusion system has been developed here to measure the kinetic changes of cell volume under various extracellular conditions, in order to determine cell osmotic behavior and membrane transport properties. The system is fabricated using soft lithographic techniques and is composed of inlets, outlets, micchannels and a perfusion chamber for trapping cells. In this study Dendritic cells (DCs) are using as a model to validate our microfluidic system with a commercialized Beckham Coulter Counter (Multisizer 3). DCs are antigen presenting cells that have been increasingly used in immunotherapy for the treatment of various diseases. Cryopreservation and banking of DCs is critical to facilitate flexible and effective immunotherapy treatment. Using mouse DCs (MDC), membrane transport properties were first investigated using our microfluidic perfusion system. Cells in the microfluidic system were perfused with 3x phosphate buffer solution. The kinetics of cell volume changes under the specific extracellular conditions were monitored by a digital camera and analyzed using a biophysical model to determine water and cryoprotectant transport properties of the cell membrane. DCs were later tested using Beckman Coulter Counter, where the kinetic osmotic behaviors of cells were quantified through the correlation between electric pulses and their corresponding cell sizes. It was shown from this study that the cryobiological characteristics of DCs determined using microfluidic perfusion system and Coulter Counter agreed well.

Topics: Measurement
Commentary by Dr. Valentin Fuster
2009;():105-106. doi:10.1115/BioMed2009-83068.

Vertically unstable fractures of the pelvis are uncommon high-energy injuries. There exist various methods of fixation for posterior pelvic ring injuries such as anterior plating, tension band-plating, trans-iliac bars, spinopelvic fixation, and iliosacral (IS) screws. Recent literature supports that triangular osteosynthesis (spinopelvic fixation) provides superior fixation strength compared to traditionally placed IS screw fixation. The theoretical advantage of triangular osteosynthesis fixation is that this technique combines unilateral spinopelvic distraction osteosynthesis for vertical stabilization with ipsilateral iliosacral screw fixation for horizontal stabilization, thereby providing biplanar stability. While spinopelvic fixation provides biplanar biomechanical stability there are inherent risks of spinal instrumentation, including neurologic injury from malpositioned pedicle screws, hardware loosening or breakage, local infection, wound dehiscence, hardware prominence requiring removal, and predisposition of spinal arthritis. Iliosacral screws are thought to be advantageous in that they can be applied percutaneously or as an open procedure, potentially limit soft tissue dissection, and minimize blood loss. However, IS screw fixation alone has been associated with fixation failure in unstable vertical shear pelvic fractures. There exists a vertical shear repair technique that has been used in revisional and non-union cases, which utilizes trans-sacral screws to stabilize vertical shear fractures. This trans-sacral technique provides biplanar stability and can be implemented without spinal instrumentation. The purpose of this study was to compare the structural integrity of trans-sacral (TS) versus triangular osteosynthesis (TO) in an unstable sacral fracture model.

Commentary by Dr. Valentin Fuster
2009;():107-109. doi:10.1115/BioMed2009-83086.

The manipulation of particles in fluids using microfluidic devices is a fundamental task in Lab-on-a-Chip applications. Grooved structures have been widely studied in particle handling and fluid mixing in microfluidic channel systems. In this study, we report use of patterning flows produced by a series of grooved surfaces with different geometrical setups integrated into a microfluidic device, to continuously manipulate the flowing particles, ranging from 6 to 20 μm in diameters, of comparable sizes to the depth of the channel. COMSOL, a multiphysics modeling software that can help predict engineering trends, is used to systematically quantify the following parameters: 1) channel depth, 2) groove width, 3) groove depth, 4) groove angle, and 5) flow speed, which may affect the performance of separation for flowing particles inside the channel. The device is fabricated using softlithographic techniques and is composed of inlets, microfluidic channels, and outlets for loading, manipulating and retrieving cell suspensions, respectively. Experimental results indicated that the particles were evenly distributed in the entrance of the microchannel and illustrate patterns of enriching, focusing, or size-selective profiles after passing through the grooved area. The preliminary simulation results also demonstrated that particles tend to bias towards the sidewall after flowing through the grooves.

Commentary by Dr. Valentin Fuster

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