Gait symmetry and regularity in transfemoral amputees assessed by trunk accelerations

<p>Abstract</p> <p>Background</p> <p>The aim of this study was to evaluate a method based on a single accelerometer for the assessment of gait symmetry and regularity in subjects wearing lower limb prostheses.</p> <p>Methods</p> <p>Ten transfemoral amputees and ten healthy control subjects were studied. For the purpose of this study, subjects wore a triaxial accelerometer on their thorax, and foot insoles. Subjects were asked to walk straight ahead for 70 m at their natural speed, and at a lower and faster speed. Indices of step and stride regularity (Ad1 and Ad2, respectively) were obtained by the autocorrelation coefficients computed from the three acceleration components. Step and stride durations were calculated from the plantar pressure data and were used to compute two reference indices (SI1 and SI2) for step and stride regularity.</p> <p>Results</p> <p>Regression analysis showed that both Ad1 well correlates with SI1 (<it>R</it>²up to 0.74), and Ad2 well correlates with SI2 (<it>R</it>²up to 0.52). A ROC analysis showed that Ad1 and Ad2 has generally a good sensitivity and specificity in classifying amputee's walking trial, as having a normal or a pathologic step or stride regularity as defined by means of the reference indices SI1 and SI2. In particular, the antero-posterior component of Ad1 and the vertical component of Ad2 had a sensitivity of 90.6% and 87.2%, and a specificity of 92.3% and 81.8%, respectively.</p> <p>Conclusions</p> <p>The use of a simple accelerometer, whose components can be analyzed by the autocorrelation function method, is adequate for the assessment of gait symmetry and regularity in transfemoral amputees.</p

Recommended number of strides for automatic assessment of gait symmetry and regularity in above-knee amputees by means of accelerometry and autocorrelation analysis

<p>Abstract</p> <p>Background</p> <p>Symmetry and regularity of gait are essential outcomes of gait retraining programs, especially in lower-limb amputees. This study aims presenting an algorithm to automatically compute symmetry and regularity indices, and assessing the minimum number of strides for appropriate evaluation of gait symmetry and regularity through autocorrelation of acceleration signals.</p> <p>Methods</p> <p>Ten transfemoral amputees (AMP) and ten control subjects (CTRL) were studied. Subjects wore an accelerometer and were asked to walk for 70 m at their natural speed (twice). Reference values of step and stride regularity indices (Ad1 and Ad2) were obtained by autocorrelation analysis of the vertical and antero-posterior acceleration signals, excluding initial and final strides. The Ad1 and Ad2 coefficients were then computed at different stages by analyzing increasing portions of the signals (considering both the signals cleaned by initial and final strides, and the whole signals). At each stage, the difference between Ad1 and Ad2 values and the corresponding reference values were compared with the minimum detectable difference, MDD, of the index. If that difference was less than MDD, it was assumed that the portion of signal used in the analysis was of sufficient length to allow reliable estimation of the autocorrelation coefficient.</p> <p>Results</p> <p>All Ad1 and Ad2 indices were lower in AMP than in CTRL (P < 0.0001). Excluding initial and final strides from the analysis, the minimum number of strides needed for reliable computation of step symmetry and stride regularity was about 2.2 and 3.5, respectively. Analyzing the whole signals, the minimum number of strides increased to about 15 and 20, respectively.</p> <p>Conclusions</p> <p>Without the need to identify and eliminate the phases of gait initiation and termination, twenty strides can provide a reasonable amount of information to reliably estimate gait regularity in transfemoral amputees.</p

Gaitography on lower-limb amputees:Repeatability and between-methods agreement

Background: Gaitography is gait parametrization from center-of-pressure trajectories of walking on an instrumented treadmill. Gaitograms may be useful for prosthetic gait analyses, as they can be rapidly and unobtrusively collected over multiple gait cycles without constraining foot placement. However, its reliability must still be established for prosthetic gait. Objectives: To evaluate (a) within-method test–retest repeatability and (b) between-methods agreement for temporal gait events (foot contact, foot off) and gait characteristics (e.g. step times, single-support duration). Study design: Cohort study with repeated measurements. Methods: Ten male proficient prosthetic walkers with a unilateral trans-femoral or trans-tibial amputation were equipped with a pressure-insole system and were invited to walk on separate days on an instrumented treadmill. Results: We found better between-methods reproducibility than within-method repeatability in temporal gait characteristics. Step times, stride times, and foot-contact events matched well between the two methods. In contrast, insole-based foot-off events were detected one-to-two samples earlier. Likewise, a similar bias was observed for temporal gait characteristics that incorporated foot-off events. Conclusion: Notwithstanding small systematic biases, the good between-methods agreement indicates that temporal gait characteristics may be determined interchangeably with gaitograms and insoles in persons with a prosthesis. However, the relatively poorer test–retest repeatability hinders longitudinal assessments with either method. Clinical relevance: Clinical practice could potentially benefit from gaitography as an efficient, unobtrusive, easy to use, automatized, and patient-friendly means to objectively parametrize prosthetic gait, with immediate availability of test results allowing for prompt clinical decision-making. Temporal gait parameters demonstrate good between-methods agreement, but poorer within-method repeatability hinders detecting prosthetic gait changes

Differentiation between solid-ankle cushioned heel and energy storage and return prosthetic foot based on step-to-step transition cost

Decreased push-off power by the prosthetic foot and inadequate roll-over shape of the foot have been shown to increase the energy dissipated during the step-to-step transition in human walking. The aim of this study was to determine whether energy storage and return (ESAR) feet are able to reduce the mechanical energy dissipated during the step-to-step transition. Fifteen males with a unilateral lower-limb amputation walked with their prescribed ESAR foot (Vari-Flex, Ossur; Reykjavík, Iceland) and with a solid-ankle cushioned heel foot (SACH) (1D10, Ottobock; Duderstadt, Germany), while ground reaction forces and kinematics were recorded. The positive mechanical work on the center of mass performed by the trailing prosthetic limb was larger (33%, p = 0.01) and the negative work performed by the leading intact limb was lower (13%, p = 0.04) when walking with the ESAR foot compared with the SACH foot. The reduced step-to-step transition cost coincided with a higher mechanical push-off power generated by the ESAR foot and an extended forward progression of the center of pressure under the prosthetic ESAR foot. Results can explain the proposed improvement in walking economy with this kind of energy storing and return prosthetic foot

PERFORMANCE EVALUATION OF THE NEW OTTO BOCK “DynamicArm” BY MEANS OF BIOMECHANICAL MODELLING

Through infra-red motion analysis systems it is possible to acquire the 3D joint kinematics of a patient while performing every day activities. These data, combined with a biomechanical model of the anatomical structures under investigation and clinical rating scales, can form the basis for an objective assessment of the patient motor ability. When the subject acquired is an amputee fitted with a new prosthetic arm, the information provided can be useful not only for the practitioner but also for the prosthesis designer. The aim of this work is to give an example of this kind of clinical/technology assessment, presenting the results obtained for a young trans-humeral amputee fitted with a prototype of the new Otto Bock DynamicArm. In particular, the analysis intended to quantitatively evaluate: 1) the performances of the Otto Bock arm, and in particular of the electromechanic elbow, when controlled in-vivo by the patient EMG signals; 2) how the patient controls the prosthesis, in order to identify critical movements and prevent possible disorders; 3) if the new prosthesis increases the patient abilities

Soft Tissue Artefact Assessment in Humeral Axial Rotation

The accuracy of upper-limb kinematic data acquired from optoelectronic systems with retro-reflective markers is poor, mainly due to soft tissue artefact (STA). For the upper-arm, humeral internal/external rotation (HIER) is the movement most affected by STA, which is measured as a percentile fraction (K) of the effective humeral axial rotation performed. The aim of this work was to quantify STA during HIERs, with independently varying attitude of the humerus and elbow flexion, and to test the possibility of estimating its mean value over the tested upper-limb orientations using one simple trial. Six able-bodied subjects performed a series of HIERs in combination with elbow flexion for different humeral planes and degrees of elevation. During the trials the instantaneous attitudes of two humeral anatomical frames were compared, one being affected by the STA to be measured, and the other assumed as the gold standard. K was found to range from 20% to 48% of the effective humeral axial rotation performed, depending on the subject, humeral attitude and elbow flexion. These last two factors comparably affect STA and resulted in mean K coefficients of variation among the subjects of about 9% and 7%, respectively. Common patterns of K with elbow flexion and humerus elevation are discussed. The data also show that the mean of K of a subject is very close to the value assessed in a specific upper-limb configuration consistent among the subjects. This result from this study could be used to build up a time-saving STA compensation procedure suitable for clinical applications

A PRELIMINARY KINEMATIC ANALYSIS OF THE UPPER LIMB DURING THE WHEELCHAIR TENNIS SERVE

INTRODUCTION Up to 78% of wheelchair users, athletes and non athletes, report shoulder pain [1]. The weight-bearing role of the shoulder is thought to be one cause as this joint was designed for mobility rather than for stability [2]. Wheelchair athletes, in addition, put increased load and repetitive stress through their shoulders during sporting activities. An accurate and quantitative biomechanical analysis of the athletes during the execution of the specific sport exercises is the only way to understand the causes of this overuse injury. This type of analysis has been performed extensively on able-bodied tennis players (APs) and weakly on wheelchair tennis players (WPs). Only a recent study examined the specific kinematic and kinetic analysis of wheelchair tennis serve [3]. However, the protocol adopted did not consider all the degrees of freedom of the shoulder joint. CLINICAL SIGNIFICANCE The aim of the present study was to better understand the causes of the shoulder joint overuse injury in WPs, using a validated specific protocol of the upper limbs [4]. METHODS Fig.1 Subject on wheelchair with marker-set. Two caucasian Italian right-handed athletes were acquired using a stereo-photogrammetric system (Vicon 612, 9 cameras, 100Hz). The first subject (SubW) was a WP (31st in the world ranking) and suffered from a complete L1 spinal cord injury, with no pathologies at the shoulder. The second subject (SubC) was an AP, middle national level. Two repetitions of the 9 combinations among 3 serve types were acquired: first and second, lateral and central, and from the deuce and the advanced service box. A validated specific protocol of the upper limbs was used [4]. From the biomechanical viewpoint, the racket arm was modelled as an open kinematic chain formed by 4 segments (thorax, shoulder girdle, humerus and forearm), with 7 degrees of freedom: 2 describing the mobility of the shoulder girdle [5], 3 of the glenohumeral joint, and 2 of the elbow. The following phases were identified: cocking (from the backswing racket’s highest point (BHP) to maximum external rotation of the glenohumeral joint (MER)) and forward-swing (from MER to the racket ball pre-impact (IMP))[3]. RESULTS 316 No differences of girdle, glenohumeral and elbow kinematics were found among serve types in both athletes. As expected, the trunk range of motion of SubW was limited with respect to SubC. The mean and standard deviation values of range of motion in the sagittal, the transverse, and the frontal plane were 29.2±5.9°, 36.5±5.2°, 45.7±5.0°, for SubW and 80.1±5.8°, 67.8±7.6°, 114.0±19.4°, for SubC. The girdle joint of SubW showed clearly a different pattern of movement in both degrees of freedom (fig 2). At the BHP the SubW girdle was more retracted (-32.6±5.1°) than the SubC girdle (-9.5±1.4°). This difference, during the cocking phase, increased and only at the IMP the subjects exhibited more similar values. Furthermore, the girdle of SubW was more depressed during the cocking phase reaching a minimum of -11.1±4.2°. As for the glenohumeral (fig 3) and the elbow joint, different pattern of motion in the cocking phase were found. On the contrary, during the forward swing phase, the players exhibited more similar pattern of motion (fig 3). Although the MER showed similar values (100.5±5.2° and 103.5±3.9°), it had a different timing (79% and 93% of the serve for SubW and SubC, respectively). DISCUSSION The comparison between AP and WP showed similar patterns for the glenohumeral and the elbow joints only during the forward-swing, while patterns of the shoulder girdle were different during the entire serve. The differences in the cocking phase are justified by the limited trunk range of motion and the constrained position on the wheelchair. The typical WPs shoulder pain could be related to these kinematics differences. However, to support these hypotheses a larger number of WPs and APs will be acquired and analyzed

Autobiographical memory and psychological distress in a sample of upper-limb amputees.

Amputation is a traumatic and life-changing event that can take years to adjust to. The present study (a) examines psychological adjustment in a specific trauma-exposed sample, (b) compares the phenomenology (e.g., vividness) of amputation-related memories to more recent memories, and (c) tests whether memory phenomenology is associated with psychological distress. A total of 24 upper-limb amputees recalled two autobiographical memories--an amputation-related memory and a recent memory--and rated the phenomenological qualities of each memory, including Vividness, Coherence, Emotional Intensity, Visual Perspective, and Distancing. Participants also completed self-rated measures of psychological distress and personality. The sample was generally well adjusted; participants showed no relevant symptoms of anxiety and depression, and personality scores were similar to the general population. There were no significant differences in phenomenology between the two types of memories recalled. Even though amputation-related memories were, on average, almost 20 years older than the recent memories, they retained their intense phenomenology. Despite the intensity of the memory, none of the phenomenological dimensions were associated with psychological distress. It is worth to further define which dimensions of phenomenology characterize memories of traumatic events, and their association with individuals' psychological reactions