LFP Oscillations in the Mesencephalic Locomotor Region during Voluntary Locomotion.

Oscillatory rhythms in local field potentials (LFPs) are thought to coherently bind cooperating neuronal ensembles to produce behaviors, including locomotion. LFPs recorded from sites that trigger locomotion have been used as a basis for identification of appropriate targets for deep brain stimulation (DBS) to enhance locomotor recovery in patients with gait disorders. Theta band activity (6-12 Hz) is associated with locomotor activity in locomotion-inducing sites in the hypothalamus and in the hippocampus, but the LFPs that occur in the functionally defined mesencephalic locomotor region (MLR) during locomotion have not been determined. Here we record the oscillatory activity during treadmill locomotion in MLR sites effective for inducing locomotion with electrical stimulation in rats. The results show the presence of oscillatory theta rhythms in the LFPs recorded from the most effective MLR stimulus sites (at threshold ≤60 µA). Theta activity increased at the onset of locomotion, and its power was correlated with the speed of locomotion. In animals with higher thresholds (>60 µA), the correlation between locomotor speed and theta LFP oscillations was less robust. Changes in the gamma band (previously recorded in vitro in the pedunculopontine nucleus (PPN), thought to be a part of the MLR) were relatively small. Controlled locomotion was best achieved at 10-20 Hz frequencies of MLR stimulation. Our results indicate that theta and not delta or gamma band oscillation is a suitable biomarker for identifying the functional MLR sites.

Analysis of weight distribution strategies in unilateral transtibial amputees during the stand-to-sit activity.

Current methods of quantifying the stand-to-sit activity (StTS) are resource intensive and have not been applied to unilateral transtibial amputees (TTAs). The purpose of this study is to define five phases of arm-rest assisted and unassisted StTS using simple instrumentation and implement this method for assessing TTA movement patterns. Twelve TTAs and 12 age-matched non-amputees performed StTS with and without arm-rest support. Symmetry of weight distribution between lower limbs was calculated for five StTS phases: Descent Initiation; Descent Deceleration; Seat-Contact; Stabilisation and Sitting. TTAs demonstrated an asymmetrical weight distribution pattern and a tendency to transfer weight to the intact limb during the course of the activity. Non-amputees had relatively higher symmetry and did not exhibit substantial weight shifts during the activity. Symmetry indices were similar for assisted and unassisted sitting in both subject groups. These results highlight a need for therapeutic interventions in TTAs for reducing loading asymmetries and associated co-morbidities. PRACTITIONER SUMMARY: This study defines a novel method for quantifying stand-to-sit movements using clinically friendly equipment and is the first to investigate the stand-to-sit activity of unilateral transtibial amputees. The observed differences in inter-limb weight distribution strategies between amputees and non-amputees could provide insights for clinical assessment and intervention.

Comparison of four different categories of prosthetic feet during ramp ambulation in unilateral transtibial amputees.

BACKGROUND: Comparative effectiveness of prosthetic feet during ramp ambulation in unilateral transtibial amputees, who function at different Medicare Functional Classification Levels, has not been published. OBJECTIVE: To determine differences in symmetry in external work between four categories of prosthetic feet in K-Level-2 and K-Level-3 unilateral transtibial amputees during ramp ascent and descent. STUDY DESIGN: Randomized repeated-measures trial. METHODS: Ten subjects completed six testing sessions during which symmetry in external work was calculated using F-scan in-sole sensors. Between testing sessions 1 and 2, subjects received standardized functional prosthetic training. In Sessions 3-6, subjects tested four feet--solid ankle cushion heel, stationary attachment flexible endoskeleton, Talux (categories K1, K2, and K3, respectively), and Proprio-Foot (microprocessor ankle)--using a study socket and had a 10- to 14-day accommodation period with each foot. RESULTS: During ramp descent, K-Level-2 subjects demonstrated higher symmetry in external work values with Talux and Proprio-Foot compared to the solid ankle cushion heel foot. K-Level-3 subjects also had higher symmetry in external work values with the Talux foot than the solid ankle cushion heel foot. Ramp ascent symmetry in external work values were not significantly different between feet. CONCLUSIONS: Prosthetic foot category appears to influence symmetry in external work more during decline walking than incline walking. K-Level-2 unilateral transtibial amputees achieve greater symmetry from K3 dynamic response prosthetic feet with J-shaped ankle and microprocessor ankles while descending ramps. CLINICAL RELEVANCE: The findings suggest that K-Level-2 unilateral transtibial amputees benefit from K3 dynamic response prosthetic feet with J-shaped ankle. These results support the prescription of K3 feet for K-Level-2 amputees who frequently negotiate ramps.

Comparison between microprocessor-controlled ankle/foot and conventional prosthetic feet during stair negotiation in people with unilateral transtibial amputation.

Contrary to stance-phase dorsiflexion of conventional prosthetic feet, the microprocessor-controlled Proprio foot permits swing-phase dorsiflexion on stairs. The purpose of this study was to compare Symmetry in External Work (SEW) between a microprocessor-controlled foot and conventional prosthetic feet in two groups with unilateral transtibial amputation (Medicare Functional Classification Levels K-Level-2 and K-Level-3) during stair ascent and descent. Ten subjects were evaluated while wearing three conventional prosthetic feet- solid ankle cushion heel (SACH), stationary attachment flexible endoskeleton (SAFE), and Talux-and the Proprio foot using a study socket and were given a 10- to 14-day accommodation period with each foot. Ground reaction forces were collected using F-scan sensors during stair ascent and descent. The SEW between the intact and amputated limbs was calculated for each foot. During stair ascent, the Proprio foot resulted in a higher interlimb symmetry than conventional prosthetic feet, with significant differences between the Pro prio and SACH/SAFE feet. The swing-phase dorsiflexion appeared to promote greater interlimb symmetry because it facilitated forward motion of the body, resulting in a heel-to-toe center of pressure trajectory. During stair descent, all feet had low symmetry without significant differences between feet. The movement strategy used when descending stairs, which is to roll over the edge of a step, had a greater influence on symmetry than the dorsiflexion features of prosthetic feet.

Influence of gait training and prosthetic foot category on external work symmetry during unilateral transtibial amputee gait.

BACKGROUND: Prosthetic foot prescription guidelines lack scientific evidence and are concurrent with an amputee's concurrent with an amputee's Medicare Functional Classification Level (K-Level) and categorization of prosthetic feet. OBJECTIVE: To evaluate the influence of gait training and four categories of prosthetic feet (K1, K2, K3, and microprocessor ankle/foot) on Symmetry in External Work for K-Level-2 and K-Level-3 unilateral transtibial amputees. DESIGN: Randomized repeated-measures trial. METHODS: Five K-Level-2 and five K-Level-3 subjects were tested in their existing prosthesis during Session 1 and again in Session 2, following 2 weeks of standardized gait training. In Sessions 3-6, subjects were tested using a study socket and one of four randomized test feet. There was an accommodation period of 10-14 days with each foot. Symmetry in External Work for positive and negative work was calculated at each session to determine symmetry of gait dynamics between limbs at self-selected walking speeds. RESULTS: K-Level-2 subjects had significantly higher negative work symmetry with the K3 foot, compared to K1/K2 feet. For both subject groups, gait training had a greater impact on positive work symmetry than test feet. CONCLUSION: Higher work symmetry is possible for K-Level-2 amputees who are trained to take advantage of K3 prosthetic feet designs. There exists a need for an objective determinant for categorizing and prescribing prosthetic feet.

Application of self-report and performance-based outcome measures to determine functional differences between four categories of prosthetic feet.

We examined the application of outcome measures to determine changes in function caused by standardized functional prosthetic gait training and the use of four different prosthetic feet in people with unilateral transtibial limb loss. Two self-report measures (Prosthetic Evaluation Questionnaire-Mobility Scale [PEQ-13] and Locomotor Capabilities Index [LCI]), and three performance-based measures (Amputee Mobility Predictor with a prosthesis [AMPPRO], 6-minute walk test [6MWT] and step activity monitor [SAM]) were used. Ten people with unilateral transtibial limb loss, five with peripheral vascular disease (PVD) and five without PVD, completed testing. Subjects were tested at baseline and after receiving training with their existing prosthesis and with the study socket and four prosthetic feet, i.e., SACH (solid ankle cushion heel), SAFE (stationary attachment flexible endoskeletal), Talux, and Proprio feet, over 8 to 10 weeks. Training was administered between testing sessions. No differences were detected by the PEQ-13, LCI, 6MWT, or SAM following training and after fitting with test feet. The AMPPRO demonstrated differences following training with the existing prosthesis in the PVD group and between selected feet from baseline testing ( p

Weight distribution symmetry during the sit-to-stand movement of unilateral transtibial amputees.

This study characterises weight distribution symmetry between the intact and amputated limbs of unilateral transtibial amputees during a sit-to-stand movement. A total of 12 amputees and 12 age-matched, non-amputees performed the activity for two conditions - rising with and without chair arm-rest assistance. The sit-to-stand movement was divided into five events: Pre-Ascent; Ascent Initiation; Seat-Off; Deceleration; Standing. Symmetry in ground reaction forces between limbs was calculated at each event together with the rise time. Results indicate that during the course of the movement, amputees increased loading of the intact limb by approximately 27%, resulting in a significant asymmetry at seat-off and deceleration events. Non-amputees loaded the dominant limb more than the non-dominant limb throughout the activity but did not exhibit substantial weight shifts. Weight distribution symmetry was not significantly different between the two rising conditions in either population. Amputees had significantly longer rise times than non-amputees only while rising without arm-rest assistance. STATEMENT OF RELEVANCE: Sit-to-stand movements are performed frequently every day. Incorrect movement biomechanics caused by musculoskeletal impairments can lead to reduced functional independence and secondary co-morbidities. This study defines five events of a sit-to-stand cycle and is the first to address asymmetries of transtibial amputees, providing ergonomic insights for clinical assessment and intervention.

Symmetry in external work (SEW): a novel method of quantifying gait differences between prosthetic feet.

Unilateral transtibial amputees (TTAs) show subtle gait variations while using different prosthetic feet. These variations have not been detected consistently with previous experimental measures. We introduce a novel measure called Symmetry in External Work (SEW) for quantifying kinetic gait differences between prosthetic feet. External work is the result of changes in kinetic and potential energy of body center of mass (CoM). SEW is computed by integrating vertical ground reaction forces obtained using F-scan in-sole sensors. Since various prosthetic feet have different designs, we hypothesized that SEW will vary with the type of foot used. This hypothesis was tested with a single unilateral TTA using four prosthetic feet (Proprio, Trias+, Seattle Lite and SACH). The Proprio (mean symmetry 94.5% +/- 1.1%) and the Trias+ (92.1% +/- 2.5%) feet exhibited higher symmetry between the intact and prosthetic limbs, as compared to the Seattle (67.8% +/- 19.3%) and SACH (35.7% +/- 11.1%) feet. There was also a good agreement in vertical CoM excursion between the intact foot and prosthetic feet with heel-toe foot plate designs. Results indicate that SEW measure may be a viable method to detect kinetic differences between prosthetic feet and could have clinical applications because of relatively low cost instrumentation and minimal subject intervention.