Probing peripheral neural pathways in electrically stimulation induced sensation

This article outlines a modified Icex® (Ossur Americas, Foothill Ranch, CA) casting technique and documents statistically significant (p ≤ 0.05) volume changes in circumferential measurements of the residuum after the application of this casting technique. The investigator-proposed hypothesis for this study was that the modified Icex casting technique would achieve sufficient volume reduction to validate the efficacy of using the technique. The investigator retrospectively collected demographic and measurement data of patients with transtibial amputation, from the University of Oklahoma Health Sciences Center in the Orthotic and Prosthetic Section, whose residua were cast using the modified Icex casting technique. The patients were initially identified through a billing code search of all patients treated from January 2001 through December 2008. Seventy-eight patients who underwent a total of 82 transtibial amputations who met the inclusion criteria with sufficient measurement information documented in the chart were included. One patient's data were excluded because of the extreme brevity of the residuum resulting in insufficient normalized data. All of the patients' residual limbs (n = 81) were cast for their initial preparatory prosthetic socket. Twenty-four of the original 78 patients were also cast for their first definitive socket during the same period. The subjects included 56 male and 22 female patients with a mean age of 50.6 (20–72) years. The studied population included 44 right and 38 left transtibial residual limbs, with the breakdown of the type of surgical amputation being 33 traditional and 49 osteomyoplastic amputations. Circumferential measurement data were collected for all casting procedures to analyze volume reduction achieved through the application of the casting bladder pressurized to 120 mm Hg. Residual limb circumferential measurement data were normalized to three levels: proximal, middle, and distal for statistical analysis in the Statistical Package for the Social Sciences (SPSS) version 18 (SPSS Inc, 2010).1 Statistical analysis, using a two-way repeated analysis of variance (ANOVA), yielded significant (p < 0.001) volume reduction at all three levels of the residual limb. The reduction in volume is not only scientifically significant but also clinically relevant.

Real-time patient-specific finite element analysis of residual limb stresses in transtibial amputees during treadmill walking

Moderatorsʼ Summary: Amputee Care

Surface EMG recording of heteronymous reflex excitation of semitendinosus motoneurones by group II afferents

We tested the hypothesis that magnetic stimulation of muscle evokes cerebral potentials by causing a muscle contraction that then activates muscle receptors. We measured cerebral evoked potentials accompanying magnetic stimulation of muscle in 3 patients during surgery both before and after muscle paralysis with succinylcholine, a depolarizing agent. The magnetic stimulation was at low intensity (30%) and at a 2/s rate. The administration of succinylcholine sufficient to produce muscle paralysis did not alter cerebral potentials evoked by either low-intensity magnetic stimulation of muscle (gastrocnemius/soleus) or electrical stimulation of peripheral nerve (tibial nerve). In 1 normal subject, the S1 nerve root action potentials conducting at rapid velocity (> 60 m/s) were detected at the S1 foramen with a needle electrode using electrical stimulation of the tibial nerve. However, no S1 nerve root potentials could be identified to magnetic stimulation of muscle that evoked a cerebral potential. We conclude that magnetic stimulation of muscle activates terminal afferents in the muscle to provide the afferent drive for the cerebral potentials independent of muscle contraction. The failure to detect the afferent volley in S1 nerve root to magnetic stimulation suggests that only a few afferents are activated or that the activation of afferents is temporally dispersed. © 1996 John Wiley & Sons, Inc.

Limb movement between the residuum and socket continues to be an underlying factor in limb health, prosthetic comfort, and gait performance yet techniques to measure this have been underdeveloped. Develop a method to measure motion between the residual limb and a transtibial prosthetic socket. Single subject, repeated measures with mathematical modeling. The gait of a participant with transtibial amputation was recorded using a motion capture system using a marker set that included arrays on the anterior distal tibia and the lateral epicondyle of the femur. The proximal or distal translation, anterior or posterior translation, and angular movements were quantified. A random Monte Carlo simulation based on the precision of the motion capture system and a model of the bone moving under the skin explored the technique's accuracy. Residual limb tissue stiffness was modeled as a linear spring based on data from Papaioannou et al. Residuum movement relative to the socket went through ~30 mm, 18 mm, and 15° range of motion. Root mean squared errors were 5.47 mm, 1.86 mm, and 0.75° when considering the modeled bone-skin movement in the proximal or distal, anterior or posterior, and angular directions, respectively. The measured movement was greater than the root mean squared error, indicating that this method can measure motion between the residuum and socket. The ability to quantify movement between the residual limb and the prosthetic socket will improve prosthetic treatment through the evaluation of different prosthetic suspensions, socket designs, and motor control of the prosthetic interface.

Loss of sensory function for upper-limb amputees inevitably devastates their life qualities, and lack of reliable sensory feedback is the biggest defect to sophisticated prosthetic hands, greatly hindering their usefulness and perceptual embodiment. Thus, it is extremely necessary to accomplish an intelligent prosthetic hand with effective tactile sensory feedback for an upper-limb amputee. This paper presents an overview of three kinds of existing sensory feedback approaches, including cutaneous mechanical stimulation (CMS), transcutaneous electrical nerve stimulation (TENS) and direct peripheral nerve electrical stimulation (DPNES). The emphasis concentrates on major scientific achievements, advantages and disadvantages. The TENS on the skin areas with evoked finger sensation (EFS) at upper-limb amputees’ residual limbs might be one of the most promising approaches to realize natural sensory feedback.

Changes in interface pressures and shear stresses over time on trans-tibial amputee subjects ambulating with prosthetic limbs: comparison of diurnal and six-month differences

"Jumping Stump" syndrome is a rare postoperative complication seen in the residual limb of amputees, with only a few cases documented in the literature. It has been defined as a peripherally induced movement disorder leading to either dystonia, myoclonus, tremors, or choreiform movements in the amputated residual limb. It is often associated with significant discomfort and an inability to ambulate with a prosthetic limb. Treatment options remain inconclusive at this time.We present a case of "Jumping Stump" syndrome in a young female transtibial amputee following revision transtibial amputation (TTA) with myodesis and targeted muscle reinnervation. About six weeks after revision surgery, the patient started experiencing significant myoclonus of the right residual limb when extending the knee. She was trialed on various oral pharmacologic agents over six months and had multiple prosthetic adjustments without any symptomatic relief. Moreover, the patient was also prescribed a daily knee range of motion (ROM) and stretching program. Six months after symptom onset, she underwent a diagnostic right sciatic nerve block and right biceps femoris point block with immediate and significant improvement in symptoms. She had a greater ROM in the affected limb without myoclonus and was able to ambulate once again with her prosthetic limb. Our patient’s response to a diagnostic nerve and motor point block, as well as her marked improvement of symptoms with a consistent home exercise (stretching) program, suggests that desensitization of a muscle-tendon stretch response likely accounted for the improvement of symptoms. It is hypothesized that chemodenervation via botulinum toxin, in addition to the consistent home stretching program, would have accelerated the improvement of symptoms and should be further explored as a potential treatment modality for "Jumping Stump" syndrome.

Individuals with prostheses use sensations experienced through the residual limb during ambulation to perceive the state of the prosthesis. For lower-limb prosthetic users, the loss of proprioception can affect stability and contribute to falls. In this work, we developed a vibrotactile device to enhance residual limb proprioception, which can be used for rehabilitation training of persons with transtibial amputation. The system consists of two vibrating motors, a solenoid, a goniometer, and a control interface. Two types of vibrotactile feedback can be generated: a short vibration via the motors and a single knock via the solenoid. The device is universally designed to fit standard prosthetic components and is inserted in line between the pylon and the socket adapter allowing the vibration to propagate from the unit to the residual limb. The design and the results of the initial functionality test of the vibrotactile unit are reported.

There is a rapid growth in limb amputation, particularly of the lower limb has been observed over the years due to road traffic accidents (TRA), infections and uncontrolled diabetes in developing countries. Peripheral vascular diseases are the leading cause of amputation in the developed countries. The prosthetic socket design aims to maximize comfort and functionality for an amputee towards ambulation. Prosthetic socket fit has a great impact on the amputee’s quality of life. The body-weight of an amputee transfers optimally through the socket to the ground during the different phases of the gait pattern/cycle and is directly is in contact with the human residual limb while prosthesis is on. Thus, socket designs play an important role in prosthetic rehabilitation; encapsulating the residual limb becomes the weight-bearing structure within the residuum–prosthesis complex. Additionally, biomechanical considerations in the socket design with pressure distribution to tolerant areas and relief to the sensitive part of the stump/residuum promote greater comfort. It acts as an interface between the residual limb and the prosthesis. The socket fit cannot be the same for all, as it differs with the individual level of amputation, shape, and dimension of the residual limb. The goal of prosthetic socket must fulfill the user's needs of increased Range of Motion (ROM) and total suspension to achieve near-normal gait pattern and optimal functioning. The knowledge of socket biomechanics, materials, and residual limb behavior improve the function, comfort, and satisfaction of the end-users. Currently, the Patellar Tendon Bearing (PTB), Total Surface Bearing (TSB), Silicone Socket Suspension (3S), and Vacuum-assisted Socket Suspension (VASS) socket designs are being used globally to optimize the amputee functioning. The clinician's expertise plays an important role in deciding the type of socket. Prosthetic socket design with the feature of self-adaptation in real time during various gait phases is one of the challenges for future research.KeywordsProsthesisSocketRehabilitationTranstibialHealthcareAmputeeTechnologyDesignBiomechanics

To demonstrate that amputees performing "virtual" movements of their amputated limb activate cortical areas previously devoted to their missing limb, we studied amputees with functional magnetic resonance imaging (fMRI) and positron emission tomographic (PET) scans and compared the results with those of normal volunteers performing imaginary movements during fMRI acquisitions. Ten amputees (age range, 33-92 yr; average age, 49 yr; six men and four women; eight upper-limb and two lower-limb amputations) able to move their phantom limb at will were studied by fMRI (all patients) and PET scan (seven patients). The time between amputation and fMRI and PET studies ranged from 1 to 27 years (average, 13 yr). Patients were asked to perform virtual movements of the amputated limb and normal movements of the contralateral normal limb according to the functional images acquisition procedure. Movements of the stump were also used to differentiate stump cortical areas from virtual movement-activated areas. Ten right-handed volunteers, age- and sex-matched to the amputees, were also studied by fMRI. All volunteers were asked to perform four tasks during their fMRI study: imaginary movements of their right arm (1 task) and foot (1 task) and real movements of their left arm (1 task) and foot (1 task). In amputees, virtual movements of the missing limbs produced contralateral primary sensorimotor cortex activation on both fMRI and PET scans. These activation areas, different from the stump activation areas, were similar in location to contralateral normal limb-activated areas. Quantitatively, in two amputees who claimed to be able to perform both slow and fast virtual movements, regional cerebral blood flow measured by PET scan in the precentral gyrus increased significantly during fast movements in comparison with slow virtual movements. In normal subjects, significant differences between real versus imaginary fMRI activations were found (for both foot and hand movements); imaginary right hand and foot tasks activated primarily the contralateral supplementary motor areas, with no significant activation detected in the contralateral precentral or postcentral gyri. Primary sensorimotor cortical areas can be activated by phantom-limb movements and thus can be considered functional for several years or decades after amputation. In this study, we found that the location of the activation of these areas is comparable to that of activations produced by normal movements in control subjects or in amputees.

While previous studies assessed corticospinal excitability changes during and after motor imagery (MI) or action observation (AO) combined with peripheral nerve electrical stimulation (ES), we examined, for the first time, the time course of corticospinal excitability changes for MI during AO combined with ES (AO-MI + ES) using transcranial magnetic stimulation to measure motor evoked potentials (MEPs) in healthy individuals. Fourteen healthy volunteers participated in the following three sessions on different days: AO-MI alone, ES alone, and AO-MI + ES. In the AO-MI task, participants imagined squeezing and relaxing a ball, along with the respective actions shown in a movie, while passively holding the ball. We applied ES (intensity, 90% of the motor threshold) to the ulnar nerve at the wrist, which innervates the first dorsal interosseous (FDI) muscle. We assessed the FDI muscle MEPs at baseline and after every 5min of the task for a total of 20min. Additionally, participants completed the Vividness of Movement Imagery Questionnaire-2 (VMIQ-2) at the beginning of the experiment. Compared to baseline, AO-MI + ES significantly increased corticospinal excitability after 10min, while AO-MI or ES alone had no effect on corticospinal excitability after 20min. Moreover, the AO-MI + ES-induced cortical excitability changes were correlated with the VMIQ-2 scores for visual and kinaesthetic imagery. Collectively, our findings indicate that AO-MI + ES induces cortical plasticity earlier than does AO-MI or ES alone and that an individual's imagery ability plays an important role in inducing cortical excitability changes following AO-MI + ES.

The relationship of hip strength to walking and balance performance in unilateral lower limb prosthesis users differs by amputation level.

Objective. Peripheral nerves serve as a link between the central nervous system and its targets. Altering peripheral nerve activity through targeted electrical stimulation is being investigated as a therapy for modulating end organ function. To support rapid advancement in the field, novel approaches to predict and prevent nerve injury resulting from electrical stimulation must be developed to overcome the limitations of traditional histological methods. The present study aims to develop an optical imaging-based approach for real-time assessment of peripheral nerve injury associated with electrical stimulation. Approach. We developed an optical coherence tomography (OCT) angiography system and a 3D printed stimulating nerve stabilizer (sNS) to assess the real-time microvascular and blood flow changes associated with electrical stimulation of peripheral nerves. We then compared the microvascular changes with established nerve function analysis and immunohistochemistry to correlate changes with nerve injury. Main results. Electrical stimulation of peripheral nerves has a direct influence on vessel diameter and capillary flow. The stimulation used in this study did not alter motor function significantly, but a delayed onset of mechanical allodynia at lower thresholds was observed using a sensory function test. Immunohistochemical analysis pointed to an increased number of macrophages within nerve fascicles and axon sprouting potentially related to nerve injury. Significance. This study is the first to demonstrate the ability to image peripheral nerve microvasculature changes during electrical stimulation. This expands the knowledge in the field and can be used to develop potential biomarkers to predict nerve injury resulting from electrical stimulation.