Contralateral Heel Research Articles

The effect of head orientation on vestibular signal-based modulation of paraspinal muscle activity during walking.

Vestibulospinal reflexes play a role in maintaining the upright posture of the trunk. Head orientation has been shown to modify the vestibulospinal reflexesduring standing. This study investigated how vestibular signals affect paraspinal muscle activity during walking, and whether head orientation changes these effects. Sixteen participants were instructed to walk on a treadmill for 8min at 78steps/min and 2.8km/h in four conditions defined by the presence of electrical vestibular stimulation (EVS) and by head orientation (facing forward and facing leftward), while bipolar electromyography (EMG) was recorded bilaterally from the paraspinal muscles from cervical to lumbar levels. In both head orientations, significant phasic EVS-EMG coherence in the paraspinal muscles was observed at ipsilateral and/or contralateral heel strikes. Compared to walking with the head forward, a significant decrease was found in EVS-evoked responses (i.e., EVS-EMG coherence and gain) when participants walked with the leftward head orientation, with which EVS induced disturbance in the sagittal plane. This overall decrease can be explained by less need of feedback control for walking stabilization in the sagittal plane compared to in the frontal plane. The decrease in coherence was only significant at the left lower vertebral levels and at the right upper vertebral levels around left heel strikes. These findings confirm the contribution of the vestibular afferent signals to the control of paraspinal muscle activity during walking and indicate that this control is changed in response to different head orientations.

Vertebral level specific modulation of paraspinal muscle activity based on vestibular signals during walking.

Evoking muscle responses by electrical vestibular stimulation (EVS) may help to understand the contribution of the vestibular system to postural control. Although paraspinal muscles play a role in postural stability, the vestibulo-muscular coupling of these muscles during walking has rarely been studied. This study aimed to investigate how vestibular signals affect paraspinal muscle activity at different vertebral levels during walking with preferred and narrow step width. Sixteen healthy participants were recruited. Participants walked on a treadmill for 8min at 78steps/min and 2.8 km/h, at two different step width, either with or without EVS. Bipolar electromyography was recorded bilaterally from the paraspinal muscles at eight vertebral levels from cervical to lumbar. Coherence, gain, and delay of EVS and EMG responses were determined. Significant EVS-EMG coupling (P < 0.01) was found at ipsilateral and/or contralateral heel strikes. This coupling was mirrored between left and right relative to the midline of the trunk and between the higher and lower vertebral levels, i.e. a peak occurred at ipsilateral heel strike at lower levels, whereas it occurred at contralateral heel strike at higher levels. EVS-EMG coupling only partially coincided with peak muscle activity. EVS-EMG coherence slightly, but not significantly, increased when walking with narrow steps. No significant differences were found in gain and phase between the vertebral levels or step width conditions. In summary, vertebral level specific modulation of paraspinal muscle activity based on vestibular signals might allow a fast, synchronized, and spatially co-ordinated response along the trunk during walking. KEY POINTS: Mediolateral stabilization of gait requires an estimate of the state of the body, which is affected by vestibular afference. During gait, the heavy trunk segment is controlled by phasic paraspinal muscle activity and in rodents the medial and lateral vestibulospinal tracts activate these muscles. To gain insight in vestibulospinal connections in humans and their role in gait, we recorded paraspinal surface EMG of cervicalto lumbar paraspinal muscles, and characterized coherence, gain and delay between EMG and electrical vestibular stimulation, during slow walking. Vestibular stimulation caused phasic, vertebral level specific modulation of paraspinal muscle activity at delays of around 40ms, which was mirrored between left, lower and right, upper vertebral levels. Our results indicate that vestibular afference causesfast, synchronized, and spatially co-ordinated responses of the paraspinal muscles along the trunk, that simultaneously contribute to stabilizing the centre of mass trajectory and to keeping the head upright.

Dynamic Changes in Lumbar Spine Kinematics During Gait May Explain Improvement in Back Pain and Disability in Patients With Hip-Spine Syndrome.

Prospective cohort. Determine if total hip arthroplasty (THA) changes lumbar spine kinematics during gait in a manner that explains the improvements in back pain seen in patients with hip-spine syndrome. For patients with hip-spine syndrome, improvements in both hip and back pain have been demonstrated after THA; however, the exact mechanism of improvement in back pain remains unknown, as no corresponding changes in lumbar spine static radiographic parameters have been identified. Thirteen patients with severe, unilateral hip osteoarthritis scheduled to undergo THA with concomitant back pain and disability were tested at baseline and 6 months after THA. Harris Hip Score (HHS) and Oswestry Disability Index questionnaires were completed; the static orientation of the spine and pelvis were measured on standing radiographs, and lumbar spine kinematics were measured during treadmill walking using a validated measurement system that matched subject-specific bone models created from CT scans to dynamic biplane radiographs. After THA, both the Oswestry Disability Index (36.3-11.3, P <0.001) and Harris Hip Score (55.7-77.9, P <0.001) improved; however, there were no changes in static intervertebral or pelvis orientation. During gait after THA, the overall lumbar spine (L1 to L5) was less lordotic from heel strike to contralateral toe off ( P <0.001), the L4 and L5 vertebra were less anteriorly tilted by 3.9° ( P =0.038) from midstance to contralateral heel strike and by 3.9° ( P =0.001) during stance, respectively. The decreased anterior tilt of the 2 lowest lumbar vertebrae and the corresponding loss of lumbar lordosis may reduce facet loading during the stance phase of gait after THA. This change in lumbar spine kinematics during gait is a potential mechanism to explain the observed improvements in back pain and disability after THA. 4.

A Novel Framework in Quantifying Oscillatory Coupling to Gait Disturbance in Parkinson's Disease.

Phase-amplitude coupling (PAC) based on the uniform phase empirical mode decomposition (UPEMD) is proposed to improve the accuracy of PAC assessment. The framework is applied to investigate the mechanism and improvement measure of gait disturbance for Parkinson's disease (PD). Hβ modulation is suppressed at the time of contralateral heel strikes and rebounds when the contralateral foot rests on the ground and the ipsilateral foot is raised. Prominent PACs exist between δ and Lβ/Hβ activities. Auditory cue improves the gait; meanwhile, it enhances the Hβ modulation, and suppresses the δ-Lβ/Hβ PACs, which may rebound toward the before-cue stage afterward. Our findings suggest the proposed UPEMD-PAC is a useful framework in quantifying PAC with pre-determined frequencies, whereas the δ-Lβ/Hβ PACs in the subthalamic nucleus serve as potential biomarkers for gait disturbance in PD. Clinical Relevance- This manifests the efficacy of auditory cues on gait disturbance. The proposed framework may be useful in diagnosing the severity of motor impairment.

Emergency Foot Fillet Free Flap Based on Posterior Tibial Vessels for Reconstruction of Contralateral Heel and Sole: A Unique Spare Part Surgery

IntroductionReconstruction of the sole is an extremely challenging problem for a reconstructive microsurgeon. The specialized nature of its skin and subcutaneous tissue makes reconstruction arduous. When posed with complex bilateral lower extremity trauma where one limb was nonsalvageable, we harvested the uninjured foot fillet flap for free flap cover to reconstruct the contralateral sole. We report two such cases with follow-up assessment. Patients and MethodsTwo cases of sole reconstruction with emergency foot fillet free flap scavenged from the amputated contralateral limb were retrospectively analyzed. In both the patients, foot fillet free flap based on the posterior tibial neurovascular bundle was used. The follow-up assessment data collected included flap status, presence of any complications and prosthesis use, and functional status of the limbs at final follow-up. ResultsBoth the free flaps survived. Postoperative period was uneventful. No complications such as wound infection, delayed healing, flap necrosis, or scar breakdown were noted. The plantar flaps had recovery of protective sensation. Both the patients are ambulant; the first man with a fitted prosthesis and the second woman with the aid of a walker. ConclusionThe opportunity to utilize spare tissue from the amputated limb should be seized. Loss of the plantar aspect of foot poses a real challenge. The plantar foot fillet free flap is a durable flap with preservation of plantar sensations. It is probably the best choice as it replaces “like with like.” Prerequisites for utilizing the “spare part surgery” concept are meticulous initial debridement as well as emergency free tissue transfer, which require senior input and excellent infrastructure.

Frequency Nesting Interactions in the Subthalamic Nucleus Correlate With the Step Phases for Parkinson's Disease.

Gait disturbance in Parkinson’s disease (PD) can be ameliorated by sound stimulation. Given that excessive β synchronization in basal ganglia is linked to motor impairment in PD, whether the frequency nesting interactions are associated with the gait problem is far from clear. To this end, the masking phase-amplitude coupling (PAC) method was proposed to overcome the trade-off between intrinsic nonlinearity/non-stationarity and demand for predetermined frequencies, normally extracted by the filter. In this study, we analyzed LFPs recorded from 13 patients (one female) with PD during stepping with bilateral deep brain electrodes implanted in the subthalamic nucleus (STN). We found that not only high-frequency oscillation (100–300 Hz) was modulated by β (13–30 Hz) but also β and γ amplitude were modulated by their low-frequency components in δ/θ/α and δ/θ/α/β bands. These PAC values were suppressed by sound stimulation, along with an improvement in gait. We also showed that gait-related high-β (Hβ) modulation in the STN was sensitive to auditory cues, and Hβ gait-phase modulation increased with a metronome. Meanwhile, phase-locking values (PLVs) across all frequencies were significantly suppressed around contralateral heel strikes, manifesting the contralateral step as a critical gait phase in gait initiation for PD. Only the PLVs around contralateral steps were sensitive to auditory cues. Our results support masking PAC as an effective method in exploring frequency nesting interactions in LFPs and reveal the linkages between sound stimulation and couplings related to gait phases in the STN. These findings raise the possibility that nesting interactions in the STN work as feasible biomarkers in alleviating gait disorders.

Sensory Reconstruction of a Posterior Heel Defect Using a Proximally Based Sensate Medial Plantar Flap with Retrograde Nerve Cleavage Technique.

Reconstruction of posterior heel defects is important because it requires thick and durable skin that can withstand pressure and shear from shoe and bed contact. Therefore, the sensate flap could be a better option for the defect. This paper reports on the safety of a medial plantar sensory flap for these defects as well as an objective measurement of the sensation of the medial plantar flap and the plantar surface distal to the donor site. Twelve patients had soft-tissue defects in the posterior heel and underwent reconstructive surgery using a proximally based sensate medial plantar sensory flap. Cases of plantar defects involving not posterior heel were excluded. For wider flap coverage, special neurovascular dissection was required. We evaluated levels of sensation quantitatively using Semmes-Weinstein (SW) monofilaments and a two-point discriminator at the final follow-up. All flaps survived without major complications. Postoperative follow-up was 12 to 64 months (mean 26 months). All 12 flaps healed without postoperative complications. There was no significant difference in minimal two-point discrimination and SW evaluator size between the transferred medial plantar flap area and the contralateral heel area or between the plantar area distal to the donor site and the contralateral side. Patients could walk normally and sleep without protective shoes or brace. A proximally based sensate medial plantar flap is a good option for the reconstruction of posterior heel defects. It can restore the characteristics of the posterior heel for shoe wearing and sleeping.

In vivo analysis of hip joint loading on Nordic walking novices

ObjectiveTo evaluate the influence of Nordic walking (NW) on hip joint loads in order to determine whether it can be safely performed during postoperative physiotherapy in patients after orthopeadic surgery of the hip.MethodsInternal hip joint loads were directly measured in vivo in 6 patients using instrumented hip prostheses during NW and ordinary walking (OW). All patients received training in two different NW techniques (double-poling and the diagonal technique) by a certified NW instructor. Measurements were conducted on a treadmill at a speed of 4 km/h on level ground, at 10% inclination and at 10% slope as well as on a level lawn at a self chosen comfortable speed. Resultant contact force (Fres), bending moment (Mbend) and torsional torque (Mtors) were compared between NW and OW as well as between both NW techniques.ResultsJoint loads showed a double peak pattern during all setups. Neither NW technique significantly influenced hip joint loads at the time of the first load peak during contralateral toe-off (CTO), which was also the absolute load peak, in comparison to OW. Compared to OW, double-poling significantly reduced Fres and Mbend at the time of the second load peak during the contralateral heel strike (CHS) on level ground both on the treadmill (− 6% and − 7%, respectively) and on the lawn (− 7% and − 9%). At 10% inclination, the diagonal technique increased Fres and Mbend at CHS (by + 6% and + 7%), but did not increase the absolute load peak at CTO.ConclusionJoint loads during NW are comparable to those of OW. Therefore, NW can be considered a low-impact activity and seems to be safe for patients that are allowed full weight bearing, e.g. during postoperative rehabilitation after THA.

Hip Abduction Strength: Relationship to Trunk and Lower Extremity Motion During A Single-Leg Step-Down Task in Professional Baseball Players.

BackgroundThe single-leg step down task (SLSD) is a clinical tool to assess movement and control of the lower extremity and trunk. Hip abduction weakness may impact movement quality during the SLSD, however the relationships between movement and strength are unclear.PurposeTo determine the relationship between hip abduction isometric strength and movement during the SLSD of trunk lean, pelvic drop, knee valgus, and hip flexion.Study DesignCross sectional, cohort studyMethodsOne hundred-eighteen Minor League baseball players (age=21.6 ± 2.0 years; n=68 pitchers, n=50 position players) participated. Bilateral hip abduction isometric strength was measured using a handheld dynamometer (HHD), and then multiplied by distance from the greater trochanter to the HHD and expressed as hip abduction torque. Video cameras captured the SLSD, with participants standing on one leg while lowering their contralateral heel to touchdown on the floor from a 0.203m (8in.) step. Trunk lean, trunk flexion, pelvic drop, knee valgus, and hip flexion were measured using Dartfish at heel touchdown. A value of 180° indicated no knee valgus. Pearson correlations examined the relationships between hip abduction torque and SLSD motions.ResultsThere were no significant correlations for position players. For pitchers, on the lead leg increased hip abduction torque weakly correlated with a decrease in knee valgus (r= 0.24, p=0.049). Also for pitchers on the trail leg, increased hip abduction torque weakly correlated with decreased pelvic drop (r= -0.28, p=0.021).ConclusionHip abduction strength contributes to dynamic control of the trunk and legs. Specifically in pitchers, hip abduction weakness was related to increased movement of the lower extremity and lumbopelvic regions during the dynamic SLSD task. These deficits could translate to altered pitching performance and injury.Levels of Evidence2.

UVB irradiation induces contralateral changes in galanin, substance P and c-fos immunoreactivity in rat dorsal root ganglia, dorsal horn and lateral spinal nucleus

The selection of control group is crucial, as the use of an inadequate group may strongly affect the results. In this study we examine the effect on contralateral tissue protein levels, in a model of unilateral UVB irradiation, as the contralateral side is commonly used as a control. Previous studies have shown that UVB irradiation increases immunoreactivity for inflammatory regulated neuropeptides.Unilateral UVB irradiation of rat hind paw was performed and corresponding contralateral spinal cord and dorsal root ganglia (DRG) were collected 2–96 h after and investigated for changes in galanin, substance P and c-fos immunoreactivity. Control tissue was collected from naïve rats. Measurement of skin blood flow from contralateral heel hind paws (Doppler), revealed no change compared to naïve rats. However, UVB irradiation caused a significant reduction in the contralateral proportion of galanin immunopositive DRG neurons, at all-time points, as well as an increase in the contralateral spinal cord dorsal horn, around the central canal and in the lateral spinal nucleus (2–48 h). The contralateral proportion of SP positive DRG neurons and dorsal horn immunoreactivity was unchanged, whereas the lateral spinal nucleus area showed increased immunoreactivity (48 h). UVB irradiation also induced a slight contralateral upregulation of c-fos in the dorsal horn/central canal area (24 and 48 h). In summary, unilateral UVB irradiation induced contralateral changes in inflammatory/nociceptive neuropeptides in spinal cord and afferent pathways involved in pain signaling already within 24 h, a time point when also ipsilateral neurochemical/physiological changes have been reported for rats and humans.

The effect of custom carbon ankle-foot orthosis alignment on roll-over shape and center of pressure velocity.

Maintaining an optimal rolling of the foot over the ground is thought to increase the stability and efficiency of pathologic gait. Ankle-foot orthoses are often prescribed to improve gait mechanics in individuals with lower extremity injuries; however, their design may compromise how the foot rolls over the ground. The aim of this study was to investigate the effects of the sagittal plane ankle-foot orthosis alignment on roll-over shape and center of pressure velocity in individuals with lower limb reconstructions. Randomized cross-over study with a control group comparison. In total, 12 individuals with lower limb reconstruction who used a custom carbon ankle-foot orthosis and 12 uninjured controls underwent gait analysis. Ankle-foot orthosis users were tested in their clinically-provided ankle-foot orthosis alignment, with an alignment that was 3° more plantarflexed, and with an alignment that was 3° more dorsiflexed. Components of roll-over shape and center of pressure velocity were calculated from heel strike on the ankle-foot orthosis limb to contralateral heel strike. Roll-over shape radius was not affected by 3° changes to alignment and was not significantly different from controls. Aligning the ankle-foot orthosis in more dorsiflexion than clinically provided resulted in a smaller peak center of pressure velocity that occurred later in stance. Individuals using custom carbon ankle-foot orthoses can accommodate 3° alterations in the dorsiflexion or plantarflexion alignment.

Load response of an osseointegrated implant used in the treatment of unilateral transfemoral amputation: An early implant loosening case study

BackgroundOsseointegrated implants for transfemoral amputees facilitate direct load transfer between the prosthetic limb and femur; however, implant loosening is a common complication, and the associated implant-bone loads remain poorly understood. This case study aimed to use patient-specific computational modeling to evaluate bone-implant interface loading during standing and walking in a transfemoral amputee with an osseointegrated implant prior to prosthesis loosening and revision surgery. MethodsOne male transfemoral amputee with an osseointegrated implant was recruited (age: 59-yrs, weight: 83 kg) and computed tomography (CT) performed on the residual limb approximately 3 months prior to implant failure. Gait analyses were performed, and the CT images used to develop a finite element model of the patient's implant and surrounding bone. Simulations of static weight bearing, and over-ground walking were then performed. FindingsDuring standing, maximum and minimum principal strains in trabecular bone adjacent to the implant were 0.26% and −0.30%, respectively. Strains generated at the instant of contralateral toe-off and contralateral heel strike during walking were substantially higher and resulted in local trabecular bone yielding. Specifically, the maximum and minimum principal strains in the thin layer of trabecular bone surrounding the distal end of the implant were 1.15% and −0.98%, respectively. InterpretationLocalised yielding of trabecular bone at the interface between the femur and implant in transfemoral amputee osseointegrated prosthesis recipients may present a risk of implant loosening due to periprosthetic bone fracture during walking. Rehabilitation exercises should aim to produce implant-bone loading that stimulates bone remodelling to provide effective bone conditioning prior to ambulation.

The timing of locomotor propulsion in healthy adults walking at multiple speeds

In computational models of human walking, both magnitude and timing of locomotor propulsion are important for mechanical and metabolic efficiency, suggesting that these are likely tightly controlled by the neuromuscular system. Studies of actual human walking have focused primarily on magnitude-related measures of propulsion, often ignoring its timing. The purpose of this study was to quantify the timing of onset and peak propulsion relative to contralateral heel strike (HS) in healthy, young adults walking at multiple speeds. Propulsion was quantified at the ground-level using the anterior component of the anteroposterior ground reaction force, the limb-level using individual limb power, and the joint-level using ankle power. Contrary to common computational models, most of our timing-related measures indicated that propulsion occurred after contralateral HS. Timing-related measures of propulsion also changed with walking speed – as speed increased, individuals initiated propulsion earlier in the support phase. Timing of locomotor propulsion is theoretically important for walking performance, especially metabolic efficiency, and could therefore provide important clinical information. This study provides a set of relatively simple metrics that can be used to quantify propulsion and benchmark data that can be used for future comparisons with individuals or populations with gait impairments.

Hip abductor muscle volumes are smaller in individuals affected by patellofemoral joint osteoarthritis

The aims of this study were twofold: firstly, to compare hip abductor muscle volumes in individuals with patellofemoral joint (PFJ) osteoarthritis (PFJ OA) against those of healthy controls; and secondly, to determine whether hip muscle volumes and hip kinematics during walking are related in individuals with PFJ OA and healthy controls. Fifty-one individuals with PFJ OA and thirteen asymptomatic, age-matched healthy controls ≥40 years were recruited. Volumes of the gluteus medius, gluteus minimus and tensor fasciae latae were obtained from magnetic resonance (MR) images. Video motion capture was used to measure three-dimensional hip joint kinematics during overground walking. Significantly smaller gluteus medius (P=0.017), gluteus minimus (P=0.001) and tensor fasciae latae (P=0.027) muscle volumes were observed in PFJ OA participants compared to controls. Weak correlations were observed between smaller gluteus minimus volume and larger hip flexion angle at contralateral heel strike (CHS) (r=-0.279, P=0.038) as well as between smaller gluteus minimus volume and increased hip adduction angle at CHS (r=-0.286, P=0.046). Reduced hip abductor muscle volume is a feature of PFJ OA and is associated with increased hip flexion and adduction angles during the late stance phase of walking for PFJ OA participants and healthy controls.

Dynamic stability and spatiotemporal parameters during turning in healthy young adults

Background and purposeTurning while walking has a frequent occurrence in daily life. Evaluation of its dynamic stability will facilitate fall prevention and rehabilitation scheme. This knowledge is so limited that we set it as the first aim of this study. Another aim was to investigate spatiotemporal parameters during turning.MethodsFifteen healthy young adults were instructed to perform straight walking, 45° step turn to the left and 45° spin turn to the right at natural speed. Dynamic stability was measured by margin of stability (MoS) in anterior, posterior, left and right direction at each data point where significant differences were detected using 95% bootstrap confidence band. Common spatiotemporal parameters were computed in each condition subdivided into approach, turn and depart phases.ResultsResults showed that minimum anterior MoS appeared at middle of swing while minimum lateral MoS at contralateral heel strike in all conditions. Posterior MoS decreased before middle of turn phase in spin whereas after middle of turn phase in step. Lateral MoS and stride width declined in turn phase of spin while in depart of step. Spin had a long step and stride length. Long swing phases were observed in turns.ConclusionsThese data help explain that people are most likely to fall forward at middle of swing and to fall toward the back and the support side at heel strike. Our findings demonstrate that instability mainly exist in turn phase of spin and depart phase of step turn.

Alternating Modulation of Subthalamic Nucleus Beta Oscillations during Stepping.

Gait disturbances in Parkinson's disease are commonly refractory to current treatment options and majorly impair patient's quality of life. Auditory cues facilitate gait and prevent motor blocks. We investigated how neural dynamics in the human subthalamic nucleus of Parkinsons's disease patients (14 male, 2 female) vary during stepping and whether rhythmic auditory cues enhance the observed modulation. Oscillations in the beta band were suppressed after ipsilateral heel strikes, when the contralateral foot had to be raised, and reappeared after contralateral heel strikes, when the contralateral foot rested on the floor. The timing of this 20–30 Hz beta modulation was clearly distinct between the left and right subthalamic nucleus, and was alternating within each stepping cycle. This modulation was similar, whether stepping movements were made while sitting, standing, or during gait, confirming the utility of the stepping in place paradigm. During stepping in place, beta modulation increased with auditory cues that assisted patients in timing their steps more regularly. Our results suggest a link between the degree of power modulation within high beta frequency bands and stepping performance. These findings raise the possibility that alternating deep brain stimulation patterns may be superior to constant stimulation for improving parkinsonian gait.SIGNIFICANCE STATEMENT Gait disturbances in Parkinson's disease majorly reduce patients' quality of life and are often refractory to current treatment options. We investigated how neural activity in the subthalamic nucleus of patients who received deep brain stimulation surgery covaries with the stepping cycle. 20–30 Hz beta activity was modulated relative to each step, alternating between the left and right STN. The stepping performance of patients improved when auditory cues were provided, which went along with enhanced beta modulation. This raises the possibility that alternating stimulation patterns may also enhance beta modulation and may be more beneficial for gait control than continuous stimulation, which needs to be tested in future studies.

Effect of arm swinging on lumbar spine and hip joint forces

During level walking, arm swing plays a key role in improving dynamic stability. In vivo investigations with a telemeterized vertebral body replacement showed that spinal loads can be affected by differences in arm positions during sitting and standing. However, little is known about how arm swing could influence the lumbar spine and hip joint forces and motions during walking. The present study aims to provide better understanding of the contribution of the upper limbs to human gait, investigating ranges of motion and joint reaction forces.A three-dimensional motion analysis was carried out via a motion capturing system on six healthy males and five patients with hip instrumented implant. Each subject performed walking with different arm swing amplitudes (small, normal, and large) and arm positions (bound to the body, and folded across the chest). The motion data were imported in a commercial musculoskeletal analysis software for kinematic and inverse dynamic investigation.The range of motion of the thorax with respect to the pelvis and of the pelvis with respect to the ground in the transversal plane were significantly associated with arm position and swing amplitude during gait. The hip external-internal rotation range of motion statistically varied only for non-dominant limb. Unlike hip joint reaction forces, predicted peak spinal loads at T12-L1 and L5-S1 showed significant differences at approximately the time of contralateral toe off and contralateral heel strike.Therefore, arm position and swing amplitude have a relevant effect on kinematic variables and spinal loads, but not on hip loads during walking.

Dynamic Trunk Stability During A Step-down Task In Baseball Players

Trunk stability is critical for the transfer of energy from the lower extremity to upper extremity during throwing. Defining lower extremity kinematics during dynamic tasks will enable understanding of their contribution to trunk stability. PURPOSE: To examine the effects of trunk stability on lower extremity kinematics during a step-down task (SDT). METHODS: Professional baseball players (n=70; 22.6 ± 2.2 years; 91.8 ± 9.9kg; 185.8 ± 6.6cm) volunteered. A SDT was performed on their lead leg from a 20.3cm box, lowering their contralateral heel to the ground and then returning to the starting position. Participants were filmed in the frontal and sagittal planes. Data were analyzed at heel strike using Dartfish. Trunk stability was defined as ‘poor’ when trunk motion (sum of trunk flexion and lean) was >24.9°, the median of the sample. ‘Good’ stability was defined as <24.9°. A one-way ANOVA was performed to determine if kinematics were different between participants with poor and good trunk stability. Pearson Product correlations characterized the relationship between trunk motion and lower extremity kinematics. RESULTS: See Table 1. Knee flexion (p=0.04) and hip flexion (p=0.03) were significantly greater in participants with good trunk stability. Significant negative correlations between trunk motion and knee (r=-0.323) and hip flexion (r=-0.360) were observed. CONCLUSION: Participants with poor trunk stability had significantly less knee and hip flexion during the SDT. Correlations indicate that as lower extremity motion decreases, trunk stability decreases. Deficits in knee and hip motion may have contributed to trunk instability, or they are a compensation strategy for the increased trunk motion in those classified with poor trunk stability. Research is needed to assess the impact of altered lower extremity kinematics and trunk stability on energy transfer during throwing.Table 1: SDT data in participants with good and poor trunk stability. Mean (SD).

Once-per-step control of ankle-foot prosthesis push-off work reduces effort associated with balance during walking.

BackgroundIndividuals with below-knee amputation have more difficulty balancing during walking, yet few studies have explored balance enhancement through active prosthesis control. We previously used a dynamical model to show that prosthetic ankle push-off work affects both sagittal and frontal plane dynamics, and that appropriate step-by-step control of push-off work can improve stability. We hypothesized that this approach could be applied to a robotic prosthesis to partially fulfill the active balance requirements of human walking, thereby reducing balance-related activity and associated effort for the person using the device.MethodsWe conducted experiments on human participants (N = 10) with simulated amputation. Prosthetic ankle push-off work was varied on each step in ways expected to either stabilize, destabilize or have no effect on balance. Average ankle push-off work, known to affect effort, was kept constant across conditions. Stabilizing controllers commanded more push-off work on steps when the mediolateral velocity of the center of mass was lower than usual at the moment of contralateral heel strike. Destabilizing controllers enforced the opposite relationship, while a neutral controller maintained constant push-off work regardless of body state. A random disturbance to landing foot angle and a cognitive distraction task were applied, further challenging participants’ balance. We measured metabolic rate, foot placement kinematics, center of pressure kinematics, distraction task performance, and user preference in each condition. We expected the stabilizing controller to reduce active control of balance and balance-related effort for the user, improving user preference.ResultsThe best stabilizing controller lowered metabolic rate by 5.5% (p = 0.003) and 8.5% (p = 0.02), and step width variability by 10.0% (p = 0.009) and 10.7% (p = 0.03) compared to conditions with no control and destabilizing control, respectively. Participants tended to prefer stabilizing controllers. These effects were not due to differences in average push-off work, which was unchanged across conditions, or to average gait mechanics, which were also unchanged. Instead, benefits were derived from step-by-step adjustments to prosthesis behavior in response to variations in mediolateral velocity at heel strike.ConclusionsOnce-per-step control of prosthetic ankle push-off work can reduce both active control of foot placement and balance-related metabolic energy use during walking.Electronic supplementary materialThe online version of this article (doi:10.1186/s12984-015-0027-3) contains supplementary material, which is available to authorized users.

Scaling of musculoskeletal models from static and dynamic trials

Subject-specific scaling of cadaver-based musculoskeletal models is important for accurate musculoskeletal analysis within multiple areas such as ergonomics, orthopaedics and occupational health. We present two procedures to scale ‘generic’ musculoskeletal models to match segment lengths and joint parameters to a specific subject and compare the results to a simpler approach based on linear, segment-wise scaling. By incorporating data from functional and standing reference trials, the new scaling approaches reduce the model sensitivity to assumed model marker positions. For validation, we applied all three scaling methods to an inverse dynamics-based musculoskeletal model and compared predicted knee joint contact forces to those measured with an instrumented prosthesis during gait. Additionally, a Monte Carlo study was used to investigate the sensitivity of the knee joint contact force to random adjustments of the assumed model marker positions (+/− one marker diameter). The model based on linear scaling showed the highest variation in the knee joint contact force of 1.44 body weight (BW) around contra-lateral heel strike, and a variation in root mean square deviation (RMSD) of 0.36 BW. The proposed methods reduced the variation to 1.0 BW (RMSD 0.26 BW) for the anatomical landmark based method and 0.47 BW (RMSD 0.06 BW) for the functional based method. Variation in model predictions due to uncertainty in marker positions is a trait of all marker-based musculoskeletal modelling approaches. The presented methods solve part of this problem and rely less on manual identification of anatomical landmarks in the model. The work represents a step towards a more consistent methodology in musculoskeletal modelling.