Mg Urbanchek

Innovations in prosthetic interfaces for the upper extremity.

Summary: Advancements in modern robotic technology have led to the development of highly sophisticated upper extremity prosthetic limbs. High-fidelity volitional control of these devices is dependent on the critical interface between the patient and the mechanical prosthesis. Recent innovations in prosthetic interfaces have focused on several control strategies. Targeted muscle reinnervation is currently the most immediately applicable prosthetic control strategy and is particularly indicated in proximal upper extremity amputations. Investigation into various brain interfaces has allowed acquisition of neuroelectric signals directly or indirectly from the central nervous system for prosthetic control. Peripheral nerve interfaces permit signal transduction from both motor and sensory nerves with a higher degree of selectivity. This article reviews the current developments in each of these interface systems and discusses the potential of these approaches to facilitate motor control and sensory feedback in upper extremity neuroprosthetic devices.

Clinical factors associated with replantation after traumatic major upper extremity amputation.

Background: Little knowledge exists concerning replantation following traumatic major upper extremity amputation. This study characterizes the injury patterns and outcomes of patients suffering major upper extremity amputation and ascertains clinical factors associated with the decision to attempt replantation. Methods: A retrospective cohort study was conducted on patients treated at a Level I trauma center between June of 2000 and August of 2011. Patients who experienced traumatic upper extremity amputation at or proximal to the radiocarpal joint were included in the study. The subset of patients subsequently undergoing replantation was identified. Medical records were reviewed and bivariate analysis was performed to identify factors associated with attempted replantation and replant survival. Results: Sixty-two patients were treated for traumatic upper extremity amputation and 20 patients underwent replantation. Injury factors associated with attempted replantation included a sharp/penetrating injury (p = 0.004), distal level of amputation (p = 0.017), Injury Severity Score less than 16 (p = 0.020), absence of avulsion (p = 0.002), absence of significant contamination (p ⩽ 0.001), and lack of multilevel involvement (p = 0.007). Replantation exhibited a complete replant survival rate of 70 percent. An Injury Severity Score of 16 or more was associated with replant failure (p = 0.004). Patients who underwent replantation demonstrated increased rates of secondary surgical revisions (p ⩽ 0.001) and complications (p = 0.023) and had a greater length of hospital stay (p = 0.024). Conclusions: Several injury characteristics are associated with the decision to attempt replantation of the major upper extremity. A high global injury severity (Injury Severity Score ≥ 16) is associated with replantation failure when attempted. Patients who undergo replantation demonstrate higher resource use, warranting further cost-analysis and outcomes investigation. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

Abstract 17: prototype sensory regenerative peripheral nerve interface for artificial limb somatosensory feedback.

total of 85 patients completed the primary outcome assessments, 47/49 patients in the study group and 38/44 in the control group. Seventy-one patients had DIEP flaps and 14 patients had free muscle-sparing TRAM flaps. There were 11 postoperative complications (13%), 7 in the treatment group, 4 in the control group, and none was related to TAP catheter, and there were no flap failures. Randomization resulted in a balanced distribution of patients, and there were no differences in age, BMI, clinical or demographic characteristics between the two groups. For the primary outcome, the reduction in parenteral morphine consumption was only significantly different between the two groups on POD 1. In the Bupivacaine group, the mean parenteral morphine consumption was 20.7 (SD=20.1) mg compared to 30.0(SD=19.1) mg in the placebo group (p=0.02) on POD 1. There were no differences between the two groups in any of the secondary outcomes measures.

Abstract 147: CHARACTERIZATION OF SIGNAL ISOLATION IN BIOTIC AND ABIOTIC RPNI SCAFFOLDS

Introduction: We have developed a Regenerative Peripheral Nerve Interface (RPNI) for volitional control of bioengineered neuroprostheses. Multiaxial control of individual prosthetic joints requires implantation of multiple proximate RPNIs. Differentiating independent RPNI signals relies on signal isolation techniques, which may require use of a biologically compatible insulating substrate. We investigated the in vivo insulating capacity of small intestinal submucosa (SIS) and silicone.

LOP31: Reliability and Validity of RPNI Signaling of Gait Phases during Voluntary Walking

Introduction: Regenerative Peripheral Nerve Interfaces (RPNIs) are neurotized muscle grafts that control prostheses through electromyography (EMG). RPNI signals have not been quantified during phases of voluntary movements. This study: a) characterizes active RPNI signaling compared to background activity and b) defines the reliability and validity of RPNI function during gait phases of rat walking. Material and Methods: Rat groups were: Control (n=3), RPNI (n=3), Denervated (n=3). Bipolar electrodes were implanted onto the soleus muscles in each group. The Control group was left intact. The Denervated group had the tibial nerve transected. For RPNIs, the soleus muscle was freely grafted to the ipsilateral thigh and neurotized by the transected tibial nerve. While walking on a treadmill, rats were videographed and raw EMG signals were simultaneously recorded. Outcome measurements were integrated EMG (iEMG) and iEMG normalized (NiEMG) to stance, swing, or sit gait phase. Results: Majority of EMG activity was observed within the stance phase—70% for Control and 79% for RPNI—as expected for active soleus postural muscles. Stance NiEMG signals were greater than swing NiEMG averages for Control and RPNI groups (Fig 1). The Denervated group stance and swing NiEMG signals were not different without peripheral nerve control. Fidelity of RPNI stance activity (NiEMG signal to background signal) was 5.6 to 1, or double the Control signal fidelity. Correlations between iEMG and stance time for the Control (r=0.74) and RPNI (r=0.76) indicate strong signal reliability (Fig. 2). Conclusion: Measurements of fidelity, reliability, and validity for RPNI signal detection all exceeded normal probability (p<0.05) during voluntary movement.

Abstract 73: SIGNAL TRANSDUCTION FROM SKELETAL MUSCLE VIA THIN-FILM POLYIMIDE ELECTRODE ARRAYS

Background: The regenerative peripheral nerve interface (RPNI) consists of a unit of free muscle that has been reinnervated by a peripheral nerve. Electrophysiologic nerve signals may be transduced via an electrode from the muscle component of the RPNI. Thin- lm polyimide electrode arrays exhibit superior  exibility compared to other available electrodes and as such may yield a better long term biocompatibility. The purpose of this study is to demonstrate in vivo recording of bioelectric signals from polyimide arrays applied to intact muscle.