Identification of trunk and pelvis movement compensations in patients with transtibial amputation using angular momentum separation

The biomechanical influence of transtibial Bone-Anchored limbs during walking

Individuals with unilateral transtibial amputation (TTA) using socket prostheses demonstrate asymmetric joint biomechanics during walking, which increases the risk of secondary comorbidities (e.g., low back pain (LBP), osteoarthritis (OA)). Bone-anchored limbs are an alternative to socket prostheses, yet it remains unknown how they influence multi-joint loading. Our objective was to determine the influence of bone-anchored limb use on multi-joint biomechanics during walking. Motion capture data (kinematics, ground reaction forces) were collected during overground walking from ten participants with unilateral TTA prior to (using socket prostheses) and 12-months after bone-anchored limb implantation. Within this year, each participant completed a rehabilitation protocol that guided progression of loading based on patient pain response and optimized biomechanics. Musculoskeletal models were developed at each testing timepoint (baseline or 12-months after implantation) and used to calculate joint kinematics, internal joint moments, and joint reaction forces (JRFs). Analyses were performed during three stance periods on each limb. The between-limb normalized symmetry index (NSI) was calculated for joint moments and JRF impulses. Discrete (range of motion (ROM), impulse NSI) dependent variables were compared before and after implantation using paired t-tests with Bonferroni-Holm corrections while continuous (ensemble averages of kinematics, moments, JRFs) were compared using statistical parametric mapping (p < 0.05). When using a bone-anchored limb, frontal plane pelvic (residual: pre = 9.6 ± 3.3°, post = 6.3 ± 2.5°, p = 0.004; intact: pre = 10.2 ± 3.9°, post = 7.9 ± 2.6°, p = 0.006) and lumbar (residual: pre = 15.9 ± 7.0°, post = 10.6 ± 2.5°, p = 0.024, intact: pre = 17.1 ± 7.0°, post = 11.4 ± 2.8°, p = 0.014) ROM was reduced compared to socket prosthesis use. The intact limb hip extension moment impulse increased (pre = -11.0 ± 3.6 Nm*s/kg, post = -16.5 ± 4.4 Nm*s/kg, p = 0.005) and sagittal plane hip moment impulse symmetry improved (flexion: pre = 23.1 ± 16.0 %, post = -3.9 ± 19.5 %, p = 0.004, extension: pre = 29.2 ± 20.3 %, post = 8.7 ± 22.9 %, p = 0.049). Residual limb knee extension moment impulse decreased compared to baseline (pre = 15.7 ± 10.8 Nm*s/kg, post = 7.8 ± 3.9 Nm*s/kg, p = 0.030). These results indicate that bone-anchored limb implantation alters multi-joint biomechanics, which may impact LBP or OA risk factors in the TTA population longitudinally.

Whole body movement strategies during sit-to-stand and stair ascent in individuals with a lower limb amputation: A systematic review

BACKGROUND

Individuals with a lower limb amputation use compensatory strategies during essential tasks such as sit-to-stand and stair ascent leading to secondary physical conditions. The ensuing biomechanical parameters outlining the motion strategies they put in place need to be identified and described.

METHODS

We searched three databases (Embase, IEEE Xplore and PubMed) for articles on the spatiotemporal, the kinematics and the kinetics that compared the amputated, the intact lower limbs, or the trunk of individuals with a unilateral transtibial or transfemoral amputation with the limbs of a control group.

FINDINGS

We found twenty articles. During sit-to-stand, individuals with a lower limb amputation increased the trunk inclination angle toward the intact lower limb, explaining higher ground reaction forces and peak knee sagittal power generation. During stair ascent, individuals with a lower limb amputation increased the stance phase duration on the intact lower limb. Moreover, individuals with a lower limb amputation increased both lower limbs hip extension moment and power, and the amputated lower limb knee extension moment. In both tasks, the individuals with a transfemoral amputation presented larger differences than those with transtibial compared to the control group.

INTERPRETATION

Both lower limbs intact joint moment and power were increased to compensate for the prosthesis passive joint and to ensure stability. Stair gait studies mainly focused on the lower limbs' biomechanical changes in the sagittal plane, while sit-to-stand studies focused on asymmetries without comparing the lower limbs independently. Better methodological descriptions are essential to enhance the external validity of previous results.

Characterizing the Gait of People With Different Types of Amputation and Prosthetic Components Through Multimodal Measurements: A Methodological Perspective

Prosthetic gait implies the use of compensatory motor strategies, including alterations in gait biomechanics and adaptations in the neural control mechanisms adopted by the central nervous system. Despite the constant technological advancements in prostheses design that led to a reduction in compensatory movements and an increased acceptance by the users, a deep comprehension of the numerous factors that influence prosthetic gait is still needed. The quantitative prosthetic gait analysis is an essential step in the development of new and ergonomic devices and to optimize the rehabilitation therapies. Nevertheless, the assessment of prosthetic gait is still carried out by a heterogeneous variety of methodologies, and this limits the comparison of results from different studies, complicating the definition of shared and well-accepted guidelines among clinicians, therapists, physicians, and engineers. This perspective article starts from the results of a project funded by the Italian Worker's Compensation Authority (INAIL) that led to the generation of an extended dataset of measurements involving kinematic, kinetic, and electrophysiological recordings in subjects with different types of amputation and prosthetic components. By encompassing different studies published along the project activities, we discuss the specific information that can be extracted by different kinds of measurements, and we here provide a methodological perspective related to multimodal prosthetic gait assessment, highlighting how, for designing improved prostheses and more effective therapies for patients, it is of critical importance to analyze movement neural control and its mechanical actuation as a whole, without limiting the focus to one specific aspect.

Lumbopelvic coordination while walking in service members with unilateral lower limb loss: Comparing variabilities derived from vector coding and continuous relative phase

BACKGROUND

Continuous relative phase and vector coding are two common approaches for quantifying lumbopelvic coordination and variability. Evaluating the application of such methodologies to the lower limb loss population is important for better understanding reported asymmetrical movement dynamics of the lumbopelvic region.

RESEARCH QUESTION

How do coordination variabilities derived from trunk-pelvic coupling angles and continuous relative phases compare among individuals with and without unilateral lower limb loss walking at self-selected speeds?

METHODS

Full-body kinematics were obtained from thirty-eight males with unilateral lower limb loss (23 transtibial and 15 transfemoral) and fifteen males without limb loss while walking along a 15 m walkway. Coordination variabilities were derived from trunk-pelvic coupling angles and continuous relative phases and compared using a multivariate approach, as well as in unilateral outcome measures between control participants and participants with lower limb loss.

RESULTS

Overall, tri-planar measures of continuous relative phase variability were 19-43% larger compared to coupling angle variabilities for individuals without limb loss and individuals with transtibial limb loss. Individuals with transfemoral limb loss had 27% and 31% larger sagittal and transverse variabilities from continuous relative phases compared to coupling angles, respectively. During both prosthetic and intact limb stance, individuals with transtibial limb loss had 19-35% greater tri-planar measures of continuous relative phase variability compared to coupling angle variabilities. During intact stance phase, tri-planar measures of continuous relative phase variability were 27%- 42% larger compared to coupling angle variabilities for individuals without limb loss.

SIGNIFICANCE

While both methods provide valid estimates of lumbopelvic movement variability during gait, continuous relative phase variability may provide a more sensitive estimate in the lower limb loss population capturing velocity-specific motions of the trunk and pelvis.

Trunk Muscle Characteristics: Differences Between Sedentary Adults With and Without Unilateral Lower Limb Amputation

OBJECTIVE

The primary purpose of this study was to compare trunk muscle characteristics between adults with and without unilateral lower limb amputation (LLA) to determine the presence of modifiable trunk muscle deficits (ie, impaired activity, reduced volume, increased intramuscular fat) evaluated by ultrasonography (US) and magnetic resonance imaging (MRI). We hypothesized that compared with adults without LLA (controls), individuals with transfemoral or transtibial LLA would demonstrate reduced multifidi activity, worse multifidi and erector spinae morphology, and greater side-to-side trunk muscle asymmetries.

DESIGN

Cross-sectional imaging study.

SETTING

Research laboratory and imaging center.

PARTICIPANTS

Sedentary adults (n=38 total) with LLA (n=9 transfemoral level; n=14 transtibial level) and controls without LLA (n=15).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

We examined bilateral multifidi activity using US at levels L3/L4-L5/S1. MRI was performed using 3-dimensional quantitative fat-water imaging; bilateral L1-L5 multifidi and erector spinae were manually traced, and muscle volume (normalized to body weight) and percentage intramuscular fat were determined. Between-group and side-to-side differences were evaluated.

RESULTS

Compared with adults without LLA, participants with LLA demonstrated reduced sound-side multifidi activity; those with transfemoral LLA had larger amputated-side multifidi volume, whereas those with transtibial LLA had greater sound- and amputated-side erector spinae intramuscular fat (P<.050). With transfemoral LLA, side-to-side differences in erector spinae volume, as well as multifidi and erector spinae intramuscular fat, were found (P<.050).

CONCLUSIONS

Impaired trunk muscle activity and increased intramuscular fat may be modifiable targets for intervention after LLA.

Relationships between mediolateral trunk-pelvic motion, hip strength, and knee joint moments during gait among persons with lower limb amputation

BACKGROUND

Repeated exposures to larger lateral trunk-pelvic motion and features of knee joint loading likely influence the onset of low back pain and knee osteoarthritis among persons with lower-limb amputation. Decreased hip abductor strength can also influence frontal plane trunk-pelvic motion and knee moments; however, it is unclear how these are inter-related post-amputation.

METHODS

Twenty-four participants with unilateral lower-limb amputation (14 transtibial; 10 transfemoral) and eight uninjured controls walked at 1.3 m/s while full-body biomechanical data were captured. Multiple linear regression and Cohen's f² predicted (P < 0.05) the influences of mediolateral trunk and pelvic ranges of motion and angular accelerations, and bilateral isometric hip abductor strength on peak (intact) knee adduction moment and loading rate.

FINDINGS

There were no group differences in hip strength, peak knee adduction moment or pelvis acceleration (p > 0.06). The combination of hip strength, and mediolateral trunk and pelvic motion did not predict (F_(5,29) = 2.53, p = 0.06, adjusted R² = 0.27, f² = 0.08) peak knee adduction moment. However, the combination of hip strength and trunk and pelvis acceleration predicted knee adduction moment loading rate (F_(7,29) = 3.59, p = 0.008, adjusted R² = 0.45, f² = 0.25), with peak trunk acceleration (β = 0.72, p = 0.008) and intact hip strength (β = 0.78, p = 0.008) significantly contributing to the model.

INTERPRETATION

These data suggest increased hip abductor strength counteracts increased lateral trunk acceleration, concomitantly influencing the rate at which the ground reaction force vector loads the intact knee joint. Persons with lower-limb amputation perhaps compensate for increased intact limb loading by increasing trunk motion, thereby increasing demand on hip abductors to attenuate this preferential loading.

Dynamic neural network approach to targeted balance assessment of individuals with and without neurological disease during non-steady-state locomotion

Background

Clinical balance assessments often rely on functional tasks as a proxy for balance (e.g., Timed Up and Go). In contrast, analyses of balance in research settings incorporate quantitative biomechanical measurements (e.g., whole-body angular momentum, H) using motion capture techniques. Fully instrumenting patients in the clinic is not feasible, and thus it is desirable to estimate biomechanical quantities related to balance from measurements taken from a subset of the body segments. Machine learning algorithms are well-suited for this type of low- to high-dimensional mapping. Thus, our goal was to develop and test an artificial neural network that to predict segment contributions to whole-body angular momentum from linear acceleration and angular velocity signals (i.e., those typically available to wearable inertial measurement units, IMUs) taken from a sparse set of body segments.

Methods

Optical motion capture data were collected from five able-bodied individuals and five individuals with Parkinson's disease (PD) walking on a non-steady-state locomotor circuit comprising stairs, ramps and changes of direction. Motion data were used to calculate angular momentum (i.e., “gold standard” output data) and body-segment linear acceleration and angular velocity data from local reference frames at the wrists, ankles and neck (i.e., network input). A dynamic nonlinear autoregressive neural network was trained using the able-bodied data (pooled across subjects). The neural network was tested on data from individuals with PD with noise added to simulate real-world IMU data.

Results

Correlation coefficients of the predicted segment contributions to whole-body angular momentum with the gold standard data were 0.989 for able-bodied individuals and 0.987 for individuals with PD. Mean RMS errors were between 2 and 7% peak signal magnitude for all body segments during completion of the locomotor circuits.

Conclusion

Our results suggest that estimating segment contributions to angular momentum from mechanical signals (linear acceleration, angular velocity) from a sparse set of body segments is a feasible method for assessing coordination of balance—even using a network trained on able-bodied data to assess individuals with neurological disease. These targeted estimates of segmental momenta could potentially be delivered to clinicians using a sparse sensor set (and likely in real-time) in order to enhance balance rehabilitation of people with PD.

Statistical analysis of timeseries data reveals changes in 3D segmental coordination of balance in response to prosthetic ankle power on ramps

Active ankle-foot prostheses generate mechanical power during the push-off phase of gait, which can offer advantages over passive prostheses. However, these benefits manifest primarily in joint kinetics (e.g., joint work) and energetics (e.g., metabolic cost) rather than balance (whole-body angular momentum, H), and are typically constrained to push-off. The purpose of this study was to analyze differences between active and passive prostheses and non-amputees in coordination of balance throughout gait on ramps. We used Statistical Parametric Mapping (SPM) to analyze time-series contributions of body segments (arms, legs, trunk) to three-dimensional H on uphill, downhill, and level grades. The trunk and prosthetic-side leg contributions to H at toe-off when using the active prosthesis were more similar to non-amputees compared to using a passive prosthesis. However, using either a passive or active prosthesis was different compared to non-amputees in trunk contributions to sagittal-plane H during mid-stance and transverse-plane H at toe-off. The intact side of the body was unaffected by prosthesis type. In contrast to clinical balance assessments (e.g., single-leg standing, functional reach), our analysis identifies significant changes in the mechanics of segmental coordination of balance during specific portions of the gait cycle, providing valuable biofeedback for targeted gait retraining.

Trunk movement compensations and corresponding core muscle demand during step ambulation in people with unilateral transtibial amputation

The objective of this investigation was to identify demands from core muscles that corresponded with trunk movement compensations during bilateral step ambulation in people with unilateral transtibial amputation (TTA). Trunk rotational angular momentum (RAM) was measured using motion capture and bilateral surface EMG was measured from four bilateral core muscles during step ascent and descent tasks in people with TTA and healthy controls. During step ascent, the TTA group generated larger mediolateral (P = 0.01) and axial (P = 0.01) trunk RAM toward the leading limb when stepping onto the intact limb than the control group, which corresponded with high demand from the bilateral erector spinae and oblique muscles. During step descent, the TTA group generated larger trunk RAM in the sagittal (P < 0.01), frontal (P < 0.01), and transverse planes (P = 0.01) than the control group, which was an effect of falling onto the intact limb. To maintain balance and arrest trunk RAM, core muscle demand was larger throughout the loading period of step descent in the TTA group. However, asymmetric trunk movement compensations did not correspond to asymmetric core muscle demand during either task, indicating a difference in motor control compensations dependent on the leading limb.

Trunk kinetic effort during step ascent and descent in patients with transtibial amputation using angular momentum separation

BACKGROUND

Patients with transtibial amputation adopt trunk movement compensations that alter effort and increase the risk of developing low back pain. However, the effort required to achieve high-demand tasks, such as step ascent and descent, remains unknown.

METHODS

Kinematics were collected during bilateral step ascent and descent tasks from two groups: 1) seven patients with unilateral transtibial amputation and 2) seven healthy control subjects. Trunk kinetic effort was quantified using translational and rotational segmental moments (time rate of change of segmental angular momentum). Peak moments during the loading period were compared across limbs and across groups.

FINDINGS

During step ascent, patients with transtibial amputation generated larger sagittal trunk translational moments when leading with the amputated limb compared to the intact limb (P=0.01). The amputation group also generated larger trunk rotational moments in the frontal and transverse planes when leading with either limb compared to the healthy group (P=0.01, P<0.01, respectively). During step descent, the amputation group generated larger trunk translational and rotational moments in all three planes when leading with the intact limb compared to the healthy group (P<0.017).

INTERPRETATION

This investigation identifies how differing trunk movement compensations, identified using the separation of angular momentum, require higher kinetic effort during stepping tasks in patients with transtibial amputation compared to healthy individuals. Compensations that produce identified increased and asymmetric trunk segmental moments, may increase the risk of the development of low back pain in patients with amputation.

Cross-Sectional Assessment of Factors Related to Pain Intensity and Pain Interference in Lower Limb Prosthesis Users

OBJECTIVE

To determine relationships between pain sites and pain intensity/interference in people with lower limb amputations (LLAs).

DESIGN

Cross-sectional survey.

SETTING

Community.

PARTICIPANTS

Lower limb prosthesis users with unilateral or bilateral amputations (N=1296; mean time since amputation, 14.1y).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Patient-Reported Outcomes Measurement Information System (PROMIS) pain intensity (1 item to assess average pain), PROMIS pain interference (4-item short form to assess the consequences of pain in desired activities), and questions that asked participants to rate the extent to which each of the following were a problem: residual limb pain (RLP), phantom limb pain (PLP), knee pain on the nonamputated side, back pain, and shoulder pain.

RESULTS

Nearly three quarters (72.1%) of participants reported problematic pain in 1 or more of the listed sites. Problematic PLP, back pain, and RLP were reported by 48.1%, 39.2%, and 35.1% of participants, respectively. Knee pain and shoulder pain were less commonly identified as problems (27.9% and 21.7%, respectively). Participants also reported significantly (P<.0001) higher pain interference (T-score ± SD, 54.7±9.0) than the normative sample based on the U.S. population (T-score ± SD, 50.0±10.0). Participants with LLAs rated their pain intensity on average ± SD at 3.3±2.4 on a 0-to-10 scale. Pain interference (ρ=.564, P<.0001) and intensity (ρ=.603, P<.0001) were positively and significantly correlated with number of pain sites reported.

CONCLUSIONS

Problematic pain symptoms, especially RLP, PLP, and back pain, affect most prosthetic limb users and have the potential to greatly restrict participation in life activities.

Separation of rotational and translational segmental momentum to assess movement coordination during walking

This investigation presents an analysis of segmental angular momentum to describe segmental coordination during walking. Generating and arresting momentum is an intuitive concept, and also forms the foundation of Newton-Euler dynamics. Total segmental angular momentum is separated into separate components, translational angular momentum (TAM) and rotational angular momentum (RAM), which provide different but complementary perspectives of the segmental dynamics needed to achieve forward progression during walking. TAM was referenced to the stance foot, which provides insight into the mechanisms behind how forward progression is achieved through coordinated segmental motion relative to the foot. Translational and rotational segmental moments were calculated directly from TAM and RAM, via Euler's 1st and 2nd laws in angular momentum form, respectively, and are composed of the effects of intersegmental forces and joint moments. Using data from 14 healthy participants, the effort required to generate and arrest momentum were assessed by linking the features of segmental angular momentum and the associated segmental moments to well-known spatiotemporal and kinetic features of the gait cycle. Segmental momentum provides an opportunity to explore and understand system-wide dynamics of coordination from an alternative perspective that is rooted in fundamentals of dynamics, and can be estimated using only segmental kinematic measurements.