Acquisition of Surface EMG Using Flexible and Low-Profile Electrodes for Lower Extremity Neuroprosthetic Control.

For persons with lower extremity (LE) amputation, acquisition of surface electromyography (sEMG) from within the prosthetic socket remains a significant challenge due to the dynamic loads experienced during the gait cycle. However, these signals are critical for both understanding the clinical effects of LE amputation and determining the desired control trajectories of active LE prostheses. Current solutions for collecting within-socket sEMG are generally (i) incompatible with a subject's prescribed prosthetic socket and liners, (ii) uncomfortable, and (iii) expensive. This study presents an alternative within-socket sEMG acquisition paradigm using a novel flexible and low-profile electrode. First, the practical performance of this Sub-Liner Interface for Prosthetics (SLIP) electrode is compared to that of commercial Ag/AgCl electrodes within a cohort of subjects without amputation. Then, the corresponding SLIP electrode sEMG acquisition paradigm is implemented in a single subject with unilateral transtibial amputation performing unconstrained movements and walking on level ground. Finally, a quantitative questionnaire characterizes subjective comfort for SLIP electrode and commercial Ag/AgCl electrode instrumentation setups. Quantitative analyses suggest comparable signal qualities between SLIP and Ag/AgCl electrodes while qualitative analyses suggest the feasibility of using the SLIP electrode for real-time sEMG data collection from load-bearing, ambulatory subjects with LE amputation.

An Ankle-Foot Prosthesis for Rock Climbing Augmentation.

This research presents the design and preliminary evaluation of an electromyographically (EMG) controlled 2-degree-of-freedom (DOF) ankle-foot prosthesis designed to enhance rock climbing ability in persons with transtibial amputation. The prosthesis comprises motorized ankle and subtalar joints, and is capable of emulating some key biomechanical behaviors exhibited by the ankle-foot complex during rock climbing maneuvers. The free space motion of the device is volitionally controlled via input from EMG surface electrodes embedded in a custom silicone liner worn on the residual limb. The device range of motion is 0.29 radians of each dorsiflexion and plantar flexion, and 0.39 radians each of inversion and eversion. Preliminary evaluation of the device was conducted, validating the system mass of 1292 grams, build height of 250 mm, joint velocity of 2.18 radians/second, settling time of 120 milliseconds, and steady state error of 0.008 radians. Clinical evaluation of the device was performed during a preliminary study with one subject with transtibial amputation. Joint angles of the ankle-foot, knee, and hip were measured during rock climbing with the robotic prosthesis and with a traditional passive prosthesis. We found that the robotic prosthesis increases the range of achieved ankle and subtalar positions compared to a standard passive prosthesis. In addition, maximum knee flexion and hip flexion angles are decreased while climbing with the robotic prosthesis. These results suggest that a lightweight, actuated, 2-DOF EMG-controlled robotic ankle-foot prosthesis can improve ankle and subtalar range of motion and climbing biomechanical function.

Flexible Dry Electrodes for EMG Acquisition within Lower Extremity Prosthetic Sockets.

Acquisition of surface electromyography (sEMG) from a person with an amputated lower extremity (LE) during prosthesis-assisted walking remains a significant challenge due to the dynamic nature of the gait cycle. Current solutions to sEMG-based neural control of active LE prostheses involve a combination of customized electrodes, prosthetic sockets, and liners. These technologies are generally: (i) incompatible with a subject's existing prosthetic socket and liners; (ii) uncomfortable to use; and (iii) expensive. This paper presents a flexible dry electrode design for sEMG acquisition within LE prosthetic sockets which seeks to address these issues. Design criteria and corresponding design decisions are explained and a proposed flexible electrode prototype is presented. Performances of the proposed electrode and commercial Ag/AgCl electrodes are compared in seated subjects without amputations. Quantitative analyses suggest comparable signal qualities for the proposed novel electrode and commercial electrodes. The proposed electrode is demonstrated in a subject with a unilateral transtibial amputation wearing her own liner, socket, and the portable sEMG processing platform in a preliminary standing and level ground walking study. Qualitative analyses suggest the feasibility of real-time sEMG data collection from load-bearing, ambulatory subjects.

Intensity of acute aerobic exercise but not aerobic fitness impacts on corticospinal excitability.

Aerobic exercise (AE) modulates cortical excitability. It can alter both corticospinal excitability and intra-cortical networks, which has implications for its use as a tool to facilitate processes such as motor learning, where increased levels of excitability are conducive to the induction of neural plasticity. Little is known about how different intensities of AE modulate cortical excitability or how individual-level characteristics impact on it. Therefore, we investigated whether AE intensities, lower than those previously employed, would be effective in increasing cortical excitability. We also examined whether the aerobic fitness of individual participants was related to the magnitude of change in AE-induced cortical excitability. In both experiments we employed transcranial magnetic stimulation to probe corticospinal excitability before and after AE. We show that 20 min of continuous moderate- (40% and 50% of heart rate reserve, HRR), but not low- (30% HRR) intensity AE was effective at increasing corticospinal excitability. We also found that while we observed increased corticospinal excitability following 20 min of continuous moderate-intensity (50% HRR) AE, aerobic fitness was not related to the magnitude of change. Our results suggest that there is a lower bound intensity of AE that is effective at driving changes in cortical excitability, and that while individual-level characteristics are important predictors of response to AE, aerobic fitness is not. Overall these findings have implication for the way that AE is used to facilitate processes such as motor learning, where increased levels of cortical excitability and plasticity are favourable.

Helmet use is associated with a decrease in intracranial hemorrhage following all-terrain vehicle crashes.

BACKGROUND: With the recent increase in size and horsepower of all-terrain vehicles (ATVs), it is imperative that preventable injuries be identified to protect the large population using ATVs. Currently, many states have no laws regulating ATV or helmet use. By identifying preventable injuries, the legislature can design appropriate laws to protect both children and adults. METHODS: A retrospective review of all patients with ATV injuries presenting between the years 2005 and 2010 was conducted. The data were grouped in several ways for analysis. This included age less than 9 years, weight less than 30 kg, crash at night, substance abuse, and presence of a helmet. RESULTS: There were 481 patients included in the study. Only 28 (8%) were using a helmet at the time of the crash. Helmet use was associated with less intracranial hemorrhage (3% vs. 22%, p = 0.01) and a decreased incidence of loss of consciousness (14% vs. 35%, p = 0.01). Patients testing positive for alcohol intoxication with or without drugs were significantly more likely to have intracranial hemorrhage, to crash at night, to have facial fracture, to have rib fracture, to arrive intubated, and to have a higher Injury Severity Score (ISS) (p < 0.01 for all). CONCLUSION: With the recent increase in size and horsepower of ATVs, it is imperative that preventable injuries be identified to help protect a growing population of ATV operators. This study reveals a high rate of intracranial hemorrhage following an ATV crash in operators who do not use a helmet. Legislative efforts to implement strict helmet laws for ATV operators may be warranted. LEVEL OF EVIDENCE: Prognostic study, level III.

Suspected bile duct injuries and appropriate early referral can reduce chances of litigation.

Bile duct injury following laparoscopic cholecystectomy is one of the most feared complications related to performing a cholecystectomy. Early identification and repair can be life saving for patients with bile duct injuries. Since the early 1990s, laparoscopic cholecystecomy (LC) has replaced open cholecystectomy as the preferred treatment of symptomatic cholethiasis, biliary dyskinesia, and cholecystitis. LC has decreased the length of hospital stay and post-operative pain and resulted in a subsequent faster return to normal daily activities; nonetheless, LC has a higher incidence in bile duct injury as compared to open cholecystectomy. Nearly all studies report the incidence of bile duct injury following open cholecystectomy between 0.1% and 0.2%. In comparison, LC has a reported incidence of bile duct injury between 0.4% and 0.7%. The aim of this article is to review our initial experience with work-up and repair of bile duct injuries following LC performed at outside facilities and referred to the University of Mississippi Medical Center (UMMC) for definitive therapy. We will also review the classification of these injuries, preferred methods of diagnosis, and benefits of early treatment as well as factors that frequently lead to litigation following bile duct injury.

The role of laparoscopy in small bowel obstruction after previous laparotomy for trauma: an initial report.

Presently, there are no guidelines to help predict which patients are more likely to have successful laparoscopic adhesiolysis. We attempt to define which preoperative characteristics of trauma patients who later develop small bowel obstruction are most amenable to a laparoscopic operation. We did a retrospective review of all patients with small bowel obstruction after previous laparotomy for trauma. For the patients that received an operation to relieve the obstruction, the location of transition zone via CT scan and location of the previous abdominal scar were recorded. A previous upper abdominal surgical incision and a transition zone outside of the pelvis on CT scan were preoperative predictors of a successful laparoscopic adhesiolysis. The laparoscopic group had a shorter length of stay. Laparoscopic surgery as the initial operative approach in the management of SBO after previous laparotomy for trauma is safe and effective. Characteristics that make the laparoscopic approach most favorable are CT transition point above the pelvis and previous midline incision above umbilicus.

Differential expression of prognostic factors and effect on survival in young (< or =40) breast cancer patients: a case-control study.

The belief that young women develop more aggressive forms of breast cancer than other women is controversial. The purpose of this study was to determine if women 40 years of age and under with breast cancer have more negative prognostic indicators and a higher 5-year mortality than those women over 40 years of age. From January 1998-December 2002, all women with breast cancer were identified from our tumor registry. Women with metastatic disease at presentation were excluded from our study. The women were divided into two groups, women under 40 (cases) and women 40 and over (controls). Seventy-eight cases were identified and matched to 228 controls. These cohorts were matched 3:1 (cases:controls) based on tumor staging. The data collected on each patient included prognostic factors such as tumor size, tumor type, estrogen and progesterone receptors, Her2/neu, and Ki-67. Information on surgical procedure, postoperative therapy, recurrence, and mortality was also gathered. The mean ages for cases and controls were 35 and 59 years, respectively. The rates of modified radical mastectomy were similar in the two groups, but young women were more likely to have breast reconstruction (33.7% vs 9.8%). The rates of breast conservation therapy were actually lower in the group under 40 (32.5% vs 37.6%). Tumors in the 40 and under group were more frequently estrogen receptor negative (33.8% vs 21.9%: P = 0.046) and progesterone receptor negative (50.0% vs 35.5%: P = 0.033). Younger women also experienced a greater prevalence of Ki-67 (P < 0.001) and higher levels of Her2/neu overexpression (P = 0.013). Women over 40 were more likely to receive hormonal therapy (39.7% vs 36.1%). Women over 40 had a lower overall rate of recurrence. A difference in overall survival does exist between these two groups of women, which trends toward significance. The women 40 and under had a lower overall 5-year survival. The reason for this difference remains unclear. Although we demonstrate a higher percentage of younger women with negative biochemical markers, the only factors independently and significantly related to higher mortality were estrogen receptor negativity and tumor stage at presentation.