Trunk-pelvis motion, joint loads, and muscle forces during walking with a transtibial amputation

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.

Comparing spinal loads in individuals with unilateral transtibial amputation with and without chronic low back pain: An EMG-informed approach

Chronic low back pain (cLBP) is highly prevalent after lower limb amputation (LLA), likely due in part to biomechanical factors. Here, three-dimensional full-body kinematics and kinetics during level-ground walking, at a self-selected and three controlled speeds (1.0, 1.3, and 1.6 m/s), were collected from twenty-one persons with unilateral transtibial LLA, with (n = 9) and without cLBP (n = 12). Peak compressive, mediolateral, and anteroposterior L5-S1 spinal loads were estimated from a full-body, transtibial amputation-specific OpenSim model and compared between groups. Predicted lumbar joint torques from muscle activations were compared to inverse dynamics and predicted and measured electromyographic muscle activations were compared for model evaluation and verification. There were no group differences in compressive or anterior shear forces (p > 0.466). During intact stance, peak ipsilateral loads increased with speed to a greater extent in the cLBP group vs. no cLBP group (p=0.023), while during prosthetic stance, peak contralateral loads were larger in the no cLBP group (p=0.047) and increased to a greater extent with walking speed compared to the cLBP group (p=0.008). During intact stance, intact side external obliques had higher activations in the no cLBP group (p=0.039), and internal obliques had higher activations in the cLBP group at faster walking speeds compared to the no cLBP group. Predicted muscle activations demonstrated similar activation patterns to electromyographic-measured activations (r = 0.56-0.96), and error between inverse dynamics and simulated spinal moments was low (0.08 Nm RMS error). Persons with transtibial LLA and cLBP may adopt movement strategies during walking to reduce mediolateral shear forces at the L5-S1 joint, particularly as walking speed increases. However, future work is needed to understand the time course from pain onset to chronification and the cumulative influence of increased spinal loads over time.

Adults with lower-limb amputation: Reduced multifidi muscle activity and extensor muscle endurance is associated with worse physical performance

Trunk muscles may be an overlooked region of deficits following lower-limb amputation (LLA). This study sought to determine the extent that trunk muscle deficits are associated with physical function following amputation. Sedentary adults with a unilateral transtibial- (n = 25) or transfemoral-level (n = 14) amputation were recruited for this cross-sectional research study. Participants underwent a clinical examination that included ultrasound imaging of the lumbar multifidi muscles, the modified Biering-Sorensen Endurance Test (mBSET), and performance-based measures, that is, the Timed Up and Go (TUG), Berg Balance Scale (BBS), and 10-m Walk Test (10mWT). Associations between trunk muscle metrics and performance were explored with regression modeling, while considering covariates known to impact performance postamputation (p ≤ 0.100). Average ultrasound-obtained, lumbar multifidi activity was 14% and 16% for transfemoral- and transtibial-level amputations, respectively, while extensor endurance was 37.34 and 12.61 s, respectively. For TUG, nonamputated-side multifidi activity and an interaction term (level x non-amputated-side multifidi activity) explained 9.4% and 6.2% of the total variance, respectively. For 10mWT, beyond covariates, non-amputated-side multifidi activity and the interaction term explained 6.1% and 5.8% of the total variance, respectively. For TUG, extensor endurance and an interaction term (level x mBSET) explained 11.9% and 8.3% of the total variance beyond covariates; for BBS and 10mWT, extensor endurance explained 11.2% and 17.2% of the total variance, respectively. Findings highlight deficits in lumbar multifidi activity and extensor muscle endurance among sedentary adults with a LLA; reduced muscle activity and endurance may be important factors to target during rehabilitation to enhance mobility-related outcomes.

Estimation of human spine orientation with inertial measurement units (IMU) at low sampling rate: How low can we go?

Studying people in their daily life is important for understanding conditions with multi-faceted aetiology such as chronic low back pain. Inertial measurement units can be used to reconstruct the posture and motion of the body outside of laboratories to enable this research. The battery life of these sensors strongly affects the usability of the system, since recharging them frequently is inconvenient and can lead to additional errors. A major determinant of the battery life for these sensors is sampling rate, but the relationship between sampling rate and accuracy in motion reconstruction is not well documented. We measured the spine of 12 participants using inertial measurement units across a variety of tasks such as sitting, standing, walking, and jogging. The orientation of the spine was reconstructed using several filters, including a novel filter developed specifically for high performance at low sampling frequencies. Benchmarking against optical motion capture, we developed a model showing that the error of all tested filters depends exponentially on the sampling frequency, with the optimal filter gains showing a similar exponential relationship. Using this model of error, we developed a criterion for recommending minimum sampling frequencies for accurate motion estimates for each task, finding frequencies ranging from about 13 to 35 Hz sufficient depending on the task. Although we only studied the spine, these models should provide insight into optimizing sampling rate and filter parameters for inertial measurements in general use.

Absent loading response knee flexion: The impact on gait kinetics and centre of mass motion in individuals with unilateral transfemoral amputation, and the effect of microprocessor controlled knee provision

BACKGROUND

Individuals with unilateral transfemoral amputation walk with increased levels of asymmetry, and this is associated with reduced gait efficiency, back pain and overuse of the intact limb. This study investigated the effect of walking with a unilateral absence of loading response knee flexion on the symmetry of anterior-posterior kinetics and centre of mass accelerations.

METHODS

A retrospective cohort study design was used, assessing three-dimensional gait data from individuals with unilateral transfemoral amputation (n = 56). The anterior-posterior gait variables analysed included; peak ground reaction forces, impulse, centre of mass acceleration, as well as rate of vertical ground reaction force increase in early stance. With respect to these variables, this study assessed the symmetry between intact and prosthetic limbs, compared intact limbs against a healthy unimpaired control group, and evaluated effect on symmetry of microprocessor controlled knee provision.

FINDINGS

Significant between-limb asymmetries were found between intact and prosthetic limbs across all variables (p < 0.0001). Intact limbs showed excessive loading when compared with control group limbs after speed normalisation across all variables (p < 0.0001). No improvement in kinetic symmetry following microprocessor controlled knee provision was found.

INTERPRETATION

The gait asymmetries for individuals with transfemoral amputation identified in this study suggest that more should be done by developers to address the resultant overloading of the intact limb, as this is thought to have negative long-term effects. The provision of microprocessor controlled knees did not appear to improve the asymmetries faced by individuals with transfemoral amputation, and clinicians should be aware of this when managing patient expectations.

Exercise Therapy in Nonspecific Low Back Pain among Individuals with Lower-Limb Amputation: A Systematic Review

Low back pain is very common condition that often becomes a long-lasting problem in prostheses users after lower limb amputation. The presented study aims to decide the potential benefits of exercise therapy on low back pain among lower limb amputees by using a systematic review. The PICO technique was used to answer the primary issue of this review: Does exercise treatment lessen the prevalence of low back pain in the population of lower limb amputees? Systematic review was conducted in the following databases: Medline-PubMed, EMBASE, Scopus, and Web of Science. Studies up to September 2010 published in English are included. Aim, target population, development and execution strategies, and treatment suggestions were among the data gathered. The primary outcomes of interest were exercise interventions as a therapy for low back pain but only two articles met including criteria. The search was broadened and 21 studies describing biomechanical changes in gait and pelvic-spine posture were analysed. This review indicates that movement therapy is a potential treatment strategy in low back pain among amputees. The major limitation of the study is the very heterogenous group of subjects in terms of amputation level, baseline activity level and comorbidities. We used a procedure that was registered in PROSPERO (CRD42022345556) to perform this systematic review of systematic reviews. There is a necessity of good quality research for concluding a consensus of exercise intervention.

Transtibial prosthetic alignment has small effects on whole-body angular momentum during functional tasks

Due to the loss of ankle function, many people with a transtibial amputation (TTA) have difficulty maintaining balance during functional tasks. Prosthetic alignment may affect how people with TTA maintain balance as it affects ground reaction forces (GRFs) and centers of pressure. We quantified the effect of prosthetic alignment on dynamic balance during several functional tasks. Ten people with TTA and 10 controls without TTA completed tasks including walking and transitioning from a chair. Participants with TTA completed all tasks with their prescribed alignment and six shifted alignments, including ±10 mm anterior/posterior, medial/lateral, and ±20 mm in the vertical direction. For each task, we quantified dynamic balance as the range of whole-body angular momentum (H→_WB) and quantified trunk range of motion (ROM) and peak GRFs. Compared to controls, participants with TTA using their prescribed alignment had a greater range of H→_WB in the sagittal plane during walking, in all planes during sit-to-stand, and in the transverse plane during stand-to-sit. These results were associated with GRF and trunk ROM differences between participant groups. Alignment only affected the range of H→_WB in the frontal plane during walking. The larger range for the tall alignment coincided with a greater difference in vertical GRF between intact and amputated legs compared to other alignments. Our findings suggest that people with TTA can adapt to small, translational, alignment changes to maintain similar levels of dynamic balance during chair transitions. Future work should investigate alignment changes during other tasks and in lower functioning individuals.

Full body musculoskeletal model for simulations of gait in persons with transtibial amputation

This paper describes the development, properties, and evaluation of a musculoskeletal model that reflects the anatomical and prosthetic properties of a transtibial amputee using OpenSim. Average passive prosthesis properties were used to develop CAD models of a socket, pylon, and foot to replace the lower leg. Additional degrees of freedom (DOF) were included in each joint of the prosthesis for potential use in a range of research areas, such as socket torque and socket pistoning. The ankle has three DOFs to provide further generality to the model. Seven transtibial amputee subjects were recruited for this study. 3 D motion capture, ground reaction force, and electromyographic (EMG) data were collected while participants wore their prescribed prosthesis, and then a passive prototype prosthesis instrumented with a 6-DOF load cell in series with the pylon. The model's estimates of the ankle, knee, and hip kinematics comparable to previous studies. The load cell provided an independent experimental measure of ankle joint torque, which was compared to inverse dynamics results from the model and showed a 7.7% mean absolute error. EMG data and muscle outputs from OpenSim's Static Optimization tool were qualitatively compared and showed reasonable agreement. Further improvements to the muscle characteristics or prosthesis-specific foot models may be necessary to better characterize individual amputee gait. The model is open-source and available at (https://simtk.org/projects/biartprosthesis) for other researchers to use to advance our understanding and amputee gait and assist with the development of new lower limb prostheses.

Changes in frontal plane kinematics over 12-months in individuals with the Percutaneous Osseointegrated Prosthesis (POP)

BACKGROUND

A bone-anchored prosthesis (BAP) eliminates the need for a conventional socket by attaching a prosthesis directly to the user's skeleton. Currently, limited research addresses changes in gait mechanics post BAP implantation.

OBJECTIVE

Examine changes in frontal plane movement patterns after BAP implantation.

METHODS

Participants were individuals with unilateral transfemoral amputation (TFA) enrolled in the US Food and Drug Administration (FDA) Early Feasibility Study examining the Percutaneous Osseointegrated Prosthesis (POP). The participants completed overground gait assessments using their conventional socket and at 6-weeks, 12-weeks, 6-months, and 12-months following POP implantation. Statistical parameter mapping techniques were used in examining changes in frontal plane kinematics over the 12-months and differences with reference values for individuals without limb loss.

RESULTS

Statistically significant deviations were found pre-implantation compared to reference values for hip and trunk angles during prosthetic limb stance phase, and for pelvis and trunk relative to the pelvis angles during prosthetic limb swing. At 6-weeks post-implantation, only the trunk angle demonstrated a statistically significant reduction in the percent of gait cycle with deviations relative to reference values. At 12-months post-implantation, results revealed frontal plane movements were no longer statistically different across the gait cycle for the trunk angle compared to reference values, and less of the gait cycle was statistically different compared to reference values for all other frontal plane patterns analyzed. No statistically significant within-participant differences were found for frontal plane movement patterns between pre-implantation and 6-weeks or 12-months post-implantation.

CONCLUSIONS

Deviations from reference values displayed prior to device implantation were reduced or eliminated 12-months post-implantation in all frontal plane patterns analyzed, while within-participant changes over the 12-month period did not reach statistical significance. Overall, the results suggest the transition to a BAP aided in normalizing gait patterns in a sample of relatively high functioning individuals with TFA.

The Biomechanical Effects of Different Bag-Carrying Styles on Lumbar Spine and Paraspinal Muscles: A Combined Musculoskeletal and Finite Element Study

OBJECTIVES

Bags such as handbags, shoulder bags, and backpacks are commonly used. However, it is difficult to assess the biomechanical effects of bag-carrying styles on the lumbar spine and paraspinal muscles using traditional methods. This study aimed to evaluate the biomechanical effects of bag-carrying styles on the lumbar spine.

METHODS

We developed a hybrid model that combined a finite element (FE) model of the lumbar spine and musculoskeletal models of three bag-carrying styles. The image data was collected from a 26-years-old, 176 cm and 70 kg volunteer. OpenSim and ABAQUS were used to do the musculoskeletal analysis and finite analysis. Paraspinal muscle force, intervertebral compressive force (ICF), and intervertebral shear force (ISF) on L1 were calculated and loaded into the FE model to assess the stress distribution on the lumbar spine.

RESULTS

Different paraspinal muscle activation occurred in the three bag-carrying models. The increase in the ICF generated by all three bags was greater than the bags' weights. The handbag produced greater muscle force, ICF, ISF, and peak stress on the nucleus pulposus than the backpack and shoulder bag of the same weight. Peak stress on the intervertebral discs in the backpack model and the L1-L4 segments of the shoulder bag model increased linearly with bag weight, and increased exponentially with bag weight in the handbag model.

CONCLUSION

Unbalanced bag-carrying styles (shoulder bags and handbags) led to greater muscle force, which generated greater ICF, ISF, and peak stress on the lumbar spine. The backpack produced the least burden on the lumbar spine and paraspinal muscles. Heavy handbags should be used carefully in daily life.

Lower back kinetic demands during induced lower limb gait asymmetries

BACKGROUND

Gait asymmetries are common in many clinical populations (e.g., amputation, injury, or deformities) and are associated with a high incidence of lower back pain. Despite this high incidence, the impact of gait asymmetries on lower back kinetic demands are not well characterized due to experimental limitations in these clinical populations. Therefore, we artificially and safely induced gait asymmetry during walking in healthy able-bodied participants to examine lower back kinetic demands compared to their normal gait.

RESEARCH QUESTION

Are lower back kinetic demands different during artificially induced asymmetries than those during normal gait?

METHODS

L5/S1 vertebral joint kinetics and trunk muscle forces were estimated during gait in twelve healthy men and women with a musculoskeletal lower back model that uniquely incorporated participant-specific responses using an EMG optimization approach. Five walking conditions were conducted on a force-measuring treadmill, including normal unperturbed "symmetrical" gait, and asymmetrical gait induced by unilaterally altering leg mass, leg length, and ankle joint motion in various combinations. Gait symmetry index and lower back kinetics were compared with repeated-measures ANOVAs and post hoc tests (α = .05).

RESULTS

The perturbations were successful in producing different degrees of step length and stance time gait asymmetries (p < .01). However, lower back kinetic demands associated with asymmetrical gait were similar to, or only moderately different from normal walking for most conditions despite the observed asymmetries.

SIGNIFICANCE

Our findings indicate that the high incidence of lower back pain often associated with gait asymmetries may not be a direct effect of increased lower back demands. If biomechanical demands are responsible for the high incidence of lower back pain in such populations, daily tasks besides walking may be responsible and warrant further investigation.

Immediate effect of stair exercise on stiffness, tone, and pressure pain threshold of thoracolumbar fascia in individuals with lower limb amputation: a preliminary report

BACKGROUND

Adaptations to the use of prosthesis in individuals with a lower limb amputation may cause changes in lumbopelvic region structures during daily life activities.

OBJECTIVE

To investigate the effect of stair exercise on the stiffness, tone, and pressure pain threshold (PPT) of the thoracolumbar fascia (TLF) in individuals with unilateral lower limb amputation.

DESIGN

This is a prospective preliminary study.

METHODS

The study was conducted in Prosthetic Orthotic Centers in Istanbul. Syrian individuals with unilateral transtibial (n = 17) and transfemoral (n = 15) amputation who received prosthesis and rehabilitation services at the centers between February 2020 and December 2020 were included in the study. The subjects were instructed to ascend and descend a nine-step stair one at a time at their maximum possible speed. Measurements were made before and immediately after the stair exercise. Tone and stiffness of TLF was measured using myometer. PPT was measured using algometer. Low back pain was evaluated using numerical pain rating scale.

RESULTS

In the transfemoral amputation group, PPT measurements taken immediately after stair exercise were significantly decreased in both the amputated ( P = 0.001) and intact ( P = 0.021) sides, whereas significant reduction in stiffness when compared with the prestair levels was observed only at the intact side ( P = 0.019). The change in PPT values on the amputated side was significantly higher in individuals with transfemoral amputation than those in individuals with transtibial amputation ( P = 0.011).

CONCLUSION

The decrease in PPT values of TLF in the transfemoral amputation group was considered as a precursor sign for low back pain development. Thus, exercises and preventive rehabilitation programs targeting TLF may be needed, especially in this group.

Effects of Knee Flexion Angles on the Joint Force and Muscle Force during Bridging Exercise: A Musculoskeletal Model Simulation

Bridging exercise is commonly used to increase the strength of the hip extensor and trunk muscles in physical therapy practice. However, the effect of lower limb positioning on the joint and muscle forces during the bridging exercise has not been analyzed. The purpose of this study was to use a musculoskeletal model simulation to examine joint and muscle forces during bridging at three different knee joint angle positions. Fifteen healthy young males (average age: 23.5 ± 2.2 years) participated in this study. Muscle and joint forces of the lumbar spine and hip joint during the bridging exercise were estimated at knee flexion angles of 60°, 90°, and 120° utilizing motion capture data. The lumbar joint force and erector spinae muscle force decreased significantly as the angle of the knee joint increased. The resultant joint forces were 200.0 ± 23.2% of body weight (%BW), 174.6 ± 18.6% BW, and 150.5 ± 15.8% BW at 60°, 90°, and 120° knee flexion angles, respectively. On the other hand, the hip joint force, muscle force of the gluteus maxims, and adductor magnus tended to increase as the angle of the knee joint increased. The resultant joint forces were 274.4 ± 63.7% BW, 303.9 ± 85.8% BW, and 341.1 ± 85.7% BW at a knee flexion angle of 60°, 90°, and 120°, respectively. The muscle force of the biceps femoris decreased significantly with increased knee flexion during the bridging exercise. In conclusion, the knee flexion position during bridging exercise has different effects on the joint and muscle forces around the hip joint and lumbar spine. These findings would help clinicians prescribe an effective bridging exercise that includes optimal lower limb positioning for patients who require training of back and hip extensor muscles.

Are lower back demands reduced by improving gait symmetry in unilateral transtibial amputees?

BACKGROUND

Gait asymmetry and a high incidence of lower back pain are typical for people with unilateral lower limb amputation. A common therapeutic objective is to improve gait symmetry; however, it is unknown whether better gait symmetry reduces lower back pain risk. To begin investigating this important clinical question, we examined a preexisting dataset to explore whether L5/S1 vertebral joint forces in people with unilateral lower limb amputation can be improved with better symmetry.

METHODS

L5/S1 compression and resultant shear forces were estimated in each participant with unilateral lower limb amputation (n = 5) with an OpenSim musculoskeletal model during different levels of guided gait asymmetry. The amount of gait asymmetry was defined by bilateral stance times and guided via real-time feedback. A theoretical lowest L5/S1 force was determined from the minimum of a best-fit quadratic curves of L5/S1 forces at levels of guided asymmetry ranging from -10 to +15%. The forces found at the theoretical lowest force and during the 0% asymmetry level were compared to forces at preferred levels of asymmetry and to those from an able-bodied group (n = 5).

FINDINGS

Results indicated that the forces for the people with unilateral lower limb amputation group at the preferred level of asymmetry were not different then at their 0% asymmetry condition, theoretical lowest L5/S1 forces, or the able-bodied group (all p-values > .23).

INTERPRETATION

These preliminary results challenge the premise that restoring symmetric gait in people with unilateral lower limb amputation will reduce risk of lower back pain.

Free-Living User Perspectives on Musculoskeletal Pain and Patient-Reported Mobility With Passive and Powered Prosthetic Ankle-Foot Components: A Pragmatic, Exploratory Cross-Sectional Study

Introduction

Studies with a powered prosthetic ankle-foot (PwrAF) found a reduction in sound knee loading compared to passive feet. Therefore, the aim of the present study was to determine whether anecdotal reports on reduced musculoskeletal pain and improved patient-reported mobility were isolated occurrences or reflect a common experience in PwrAF users.

Methods

Two hundred and fifty individuals with transtibial amputation (TTA) who had been fitted a PwrAF in the past were invited to an online survey on average sound knee, amputated side knee, and low-back pain assessed with numerical pain rating scales (NPRS), the PROMIS Pain Interference scale, and the PLUS-M for patient-reported mobility in the free-living environment. Subjects rated their current foot and recalled the ratings for their previous foot. Recalled scores were adjusted for recall bias by clinically meaningful amounts following published recommendations. Statistical comparisons were performed using Wilcoxon's signed rank test.

Results

Forty-six subjects, all male, with unilateral TTA provided data suitable for analysis. Eighteen individuals (39%) were current PwrAF users, whereas 28 subjects (61%) had reverted to a passive foot. After adjustment for recall bias, current PwrAF users reported significantly less sound knee pain than they recalled for use of a passive foot (−0.5 NPRS, p = 0.036). Current PwrAF users who recalled sound knee pain ≥4 NPRS with a passive foot reported significant and clinically meaningful improvements in sound knee pain (−2.5 NPRS, p = 0.038) and amputated side knee pain (−3 NPRS, p = 0.042). Current PwrAF users also reported significant and clinically meaningful improvements in patient-reported mobility (+4.6 points PLUS-M, p = 0.016). Individuals who had abandoned the PwrAF did not recall any differences between the feet.

Discussion

Current PwrAF users reported significant and clinically meaningful improvements in patient-reported prosthetic mobility as well as sound knee and amputated side knee pain compared to recalled mobility and pain with passive feet used previously. However, a substantial proportion of individuals who had been fitted such a foot in the past did not recall improvements and had reverted to passive feet. The identification of individuals with unilateral TTA who are likely to benefit from a PwrAF remains a clinical challenge and requires further research.

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.

A block randomised controlled trial investigating changes in postural control following a personalised 12-week exercise programme for individuals with lower limb amputation

BACKGROUND

Individuals with a lower limb amputation (LLA) have an increased risk of falls and often report lower balance confidence. They must compensate for altered mechanics and prosthetic limitations in order to execute appropriate motor responses to postural perturbations. Personalised exercise could be an effective strategy to enhance balance and reduce falls.

RESEARCH QUESTION

In this study, we investigated whether a personalised exercise programme could improve postural control and self-reported balance confidence in individuals with an LLA.

METHODS

Participants were block randomised into two groups (exercise, n = 7; control, n = 7) based on age and level of amputation. The exercise group completed a 12-week personalised exercise programme, including home-based exercise sessions, consisting of balance, endurance, strength, and flexibility training. The control group continued with their normal daily activities. All participants performed the Sensory Organization Test (SOT) and Motor Control Test (MCT) on the NeuroCom SMART Equitest, and completed the Activities-specific Balance Confidence-UK (ABC) self-report questionnaire, at baseline and post-intervention.

RESULTS AND SIGNIFICANCE

Exercise group equilibrium scores improved significantly when standing on an unstable support surface with no visual input and inaccurate somatosensory feedback (SOT condition 5, P < 0.012, d = 1.45). There were significant group*time interactions for medium (P = 0.029) and large (P = 0.048) support surface forward translations, which were associated with a trend towards increased weight-bearing on the intact limb in the control group (medium: P = 0.055; large: P = 0.087). No significant changes in ABC score were observed. These results indicate reduced reliance on visual input, and/or enhanced interpretation of somatosensory input, following an exercise programme. However, objective improvements in aspects of postural control were not associated with subjective improvements in self-reported balance confidence. More weight-bearing asymmetry in the control group suggests that a lack of targeted exercise training may have detrimental effects, with potential adverse long-term musculoskeletal consequences, that were quantifiable within a short timeframe.

A backpack load sharing model to evaluate lumbar and hip joint contact forces during shoulder borne and hip belt assisted load carriage

Musculoskeletal injuries of the lumbar spine occur frequently among military service members and are associated with heavy backpack loads. Musculoskeletal modeling and simulation facilitate biomechanical evaluation to compare different backpack designs. We developed a backpack attachment model that can be tuned to represent various load distributions between the torso and pelvis. We generated walking simulations to estimate muscle and joint contact forces of unloaded walking and while carrying 38 kg using shoulder-borne backpacks and hip belt-assisted backpacks for six U.S. Marines. Three-dimensional peak and average lumbar (L4-L5) and hip joint contact forces over the stance phase were compared between each load condition. Axial L4-L5 and axial and anterior hip joint contact forces were greater during both backpack conditions compared to the unloaded condition. Joint contact forces were similar between backpack conditions. Future studies incorporating additional participants, walking conditions, and backpack load distributions are suggested for further model development and backpack design evaluation.

Development of a multiscale model of the human lumbar spine for investigation of tissue loads in people with and without a transtibial amputation during sit-to-stand

Quantification of lumbar spine load transfer is important for understanding low back pain, especially among persons with a lower limb amputation. Computational modeling provides a helpful solution for obtaining estimates of in vivo loads. A multiscale model was constructed by combining musculoskeletal and finite element (FE) models of the lumbar spine to determine tissue loading during daily activities. Three-dimensional kinematic and ground reaction force data were collected from participants with ([Formula: see text]) and without ([Formula: see text]) a unilateral transtibial amputation (TTA) during 5 sit-to-stand trials. We estimated tissue-level load transfer from the multiscale model by controlling the FE model with intervertebral kinematics and muscle forces predicted by the musculoskeletal model. Annulus fibrosis stress, intradiscal pressure (IDP), and facet contact forces were calculated using the FE model. Differences in whole-body kinematics, muscle forces, and tissue-level loads were found between participant groups. Notably, participants with TTA had greater axial rotation toward their intact limb ([Formula: see text]), greater abdominal muscle activity ([Formula: see text]), and greater overall tissue loading throughout sit-to-stand ([Formula: see text]) compared to able-bodied participants. Both normalized (to upright standing) and absolute estimates of L4-L5 IDP were close to in vivo values reported in the literature. The multiscale model can be used to estimate the distribution of loads within different lumbar spine tissue structures and can be adapted for use with different activities, populations, and spinal geometries.

Biomechanical responses of young adults with unilateral transfemoral amputation using two types of mechanical stance control prosthetic knee joints

BACKGROUND

Prosthetic knee joint function is important in the rehabilitation of individuals with transfemoral amputation.

OBJECTIVES

The objective of this study was to assess the gait patterns associated with two types of mechanical stance control prosthetic knee joints-weight-activated braking knee and automatic stance-phase lock knee. It was hypothesized that biomechanical differences exist between the two knee types, including a prolonged swing-phase duration and exaggerated pelvic movements for the weight-activated braking knee during gait.

STUDY DESIGN

Prospective crossover study.

METHODS

Spatiotemporal, kinematic, and kinetic parameters were obtained via instrumented gait analysis for 10 young adults with a unilateral transfemoral amputation. Discrete gait parameters were extracted based on their magnitudes and timing.

RESULTS

A 1.01% ± 1.14% longer swing-phase was found for the weight-activated braking knee (p < 0.05). The prosthetic ankle push-off also occurred earlier in the gait cycle for the weight-activated braking knee. Anterior pelvic tilt was 3.3 ± 3.0 degrees greater for the weight-activated braking knee. This range of motion was also higher (p < 0.05) and associated with greater hip flexion angles.

CONCLUSIONS

Stance control affects biomechanics primarily in the early and late stance associated with prosthetic limb loading and unloading. The prolonged swing-phase time for the weight-activated braking knee may be associated with the need for knee unloading to initiate knee flexion during gait. The differences in pelvic tilt may be related to knee stability and possibly the different knee joint stance control mechanisms.

CLINICAL RELEVANCE

Understanding the influence of knee function on gait biomechanics is important in selecting and improving treatments and outcomes for individuals with lower-limb amputations. Weight-activated knee joints may result in undesired gait deviations associated with stability in early stance-phase, and swing-phase initiation in the late stance-phase of gait.

The feasibility and validity of a wearable sensor system to assess the stability of high-functioning lower-limb prosthesis users

Introduction

Lower-limb prosthesis users (LLPUs) experience increased fall risk due to gait and balance impairments. Clinical outcome measures are useful for measuring balance impairment and fall risk screening but suffer from limited resolution and ceiling effects. Recent advances in wearable sensors that can measure different components of gait stability may address these limitations. This study assessed feasibility and construct validity of a wearable sensor system (APDM Mobility Lab) to measure postural control and gait stability.

Materials and Methods

Lower-limb prosthesis users (n=22) and able-bodied controls (n=24) completed an Instrumented Stand-and-Walk Test (ISAW) while wearing the wearable sensors. Known-groups analysis (prosthesis versus controls) and convergence analysis (Prosthetic Limb Users Survey of Mobility [PLUS-M] and Activity-specific Balance Confidence [ABC] Scale) were performed on 20 stability-related measures.

Results

The system was applied without complications; however missing anticipatory postural adjustment data points for nine subjects affected the analysis. Of the 20 analyzed measures output by the sensors, only three significantly differed (p≤.05) between cohorts, and two demonstrated statistically significant correlations with the self-report measures.

Conclusions

The results of this study suggest the clinical feasibility but only partial construct validity of the wearable sensor system in conjunction with the ISAW test to measure LLPU stability and balance. The sample consisted of high-functioning LLPUs, so further research should evaluate a more representative sample with additional outcome measures and tasks.

[Observational gait scale for persons with lower extremity amputation. Design and content validity]

INTRODUCTION

Gait pattern is altered in persons with lower extremity amputation. To assess gait pattern, it is important to use observational gait scales with a good content validity.

OBJECTIVES

To design an observational gait scale and to analyze its content validity.

MATERIAL AND METHODS

An expert committee was formed to obtain a version of the scale. The same committee was responsible for evaluating the scale. The content validity index (CVI) was calculated, both for each item and for the global scale.

RESULTS

The main kinematic and spatiotemporal alterations were selected to design the items. The scale consists of 2sections and 25 items, with a maximum score of 35 points. An overall CVI score of 0.90 was obtained, and an index of validity for most items with values higher than 0.78.

CONCLUSION

The Observational gait scale for persons with amputation of the lower extremity showed excellent content validity according to the CVI obtained. Future studies should evaluate its reliability and construct validity.

Foot hyperpronation alters lumbopelvic muscle function during the stance phase of gait

BACKGROUND

Although altered muscular control of the lumbopelvic region is one of the main risk factors for the development of low back pain and dysfunction, the influence of abnormal foot posture on lumbopelvic muscular function has not been investigated.

RESEARCH QUESTION

To determine possible functional changes due to hyperpronation in the main muscles that control the lumbopelvic segment.

METHODS

Kinematic and kinetic data were collected from 15 persons with hyperpronated feet and compared to a control group of 15 persons with normally aligned feet during the stance phase of gait. A generic OpenSim musculoskeletal model was scaled for each participant. A computed muscle control approach was used to produce a forward dynamic simulation of walking to determine muscle function.

RESULTS

In the hyperpronation group significantly greater peak forces were observed in the erector spinae, iliopsoas and abdominals compared to controls. The former group showed peak latencies for abdominal muscles during early stance, and for erector spinae muscles during both early and late stance. No significant between-group differences were found in gluteus maximus muscle activation in the stance phase of gait.

SIGNIFICANCE

Abnormal foot pronation can change the timing and intensity of lumbopelvic muscle activation. These changes may predispose people to develop secondary dysfunctions.

Lower Extremity Joint Contributions to Trunk Control During Walking in Persons with Transtibial Amputation

Controlled trunk motion is crucial for balance and stability during walking. Persons with lower extremity amputation often exhibit abnormal trunk motion, yet underlying mechanisms are not well understood nor have optimal clinical interventions been established. The aim of this work was to characterize associations between altered lower extremity joint moments and altered trunk dynamics in persons with unilateral, transtibial amputation (TTA). Full-body gait data were collected from 10 persons with TTA and 10 uninjured persons walking overground (~1.4 m/s). Experimentally-measured trunk angular accelerations were decomposed into constituent accelerations caused by net joint moments throughout the body using an induced acceleration analysis. Results showed persons with TTA had similar ankle moment magnitude relative to uninjured persons (P > 0.05), but greater trunk angular acceleration induced by the prosthetic ankle which acted to lean the trunk ipsilaterally (P = 0.003). Additionally, persons with TTA had a reduced knee extensor moment relative to uninjured persons (P < 0.001), resulting in lesser sagittal and frontal induced trunk angular accelerations (P < 0.001). These data indicate kinetic compensations at joints other than the lumbar and hip contribute to altered trunk dynamics in persons with a unilateral TTA. Findings may inform development of new clinical strategies to modify problematic trunk motion.

Spinopelvic sagittal alignment of patients with transfemoral amputation

PURPOSE

This study aims to describe the spinopelvic sagittal alignment in transfemoral amputees (TFAs) from a radiologic study of the spine with a postural approach to better understand the high prevalence of low back pain (LBP) in this population.

METHODS

TFAs underwent X-rays with 3-D reconstructions of the full spine and pelvis. Sagittal parameters were analyzed and compared to the literature. Differences between TFAs with and without LBP were also observed.

RESULTS

Twelve subjects have been prospectively included (TFA-LBP group (n = 5) and TFA-NoP group (n = 7)). Four of the five subjects of the TFA-LBP group and two of the seven in TFAs-NoP group had an imbalanced sagittal posture, especially regarding the T9-tilt, significantly higher in the TFA-LBP group than in the TFA-NoP (p = 0.046). Eight subjects (6 TFA-NoP and 2 TFA-LBP) had abnormal low value of thoracic kyphosis (TK). Moreover, the mean angle of TK in the TFA-NoP group was lower than in the TFA-LBP group (p = 0.0511).

CONCLUSION

In the considered sample, TFAs often present a sagittal imbalance. A low TK angle seems to be associated with the absence of LBP. It can be hypothesized that this compensatory mechanism of the sagittal imbalance is the most accessible in this population. This study emphasizes the importance of considering the sagittal balance of the pelvis and the spine in patients with a TFA to better understand the high prevalence of LBP in this population. It should be completed by the analysis of the spinopelvic balance and the lower limbs in 3D. These slides can be retrieved under Electronic Supplementary Material.

Reproducibility and discriminant validity of two clinically feasible measurement methods to obtain coronal plane gait kinematics in participants with a lower extremity amputation

Introduction

Measuring coronal plane gait kinematics of the pelvis and trunk during rehabilitation of participants with a lower extremity amputation is important to detect asymmetries in gait which are hypothesised as associated with secondary complaints. The aim of this study was to test the reproducibility and discriminant validity of a three-dimensional (3-D; inertial measurement units) and a two-dimensional (2-D; video-based) system.

Methods

We tested the test-retest and inter-rater reproducibility of both systems and the 2-D system, respectively, in participants with a lower extremity amputation (group 1) and healthy subjects (group 2). The discriminant validity was determined with a within-group comparison for the 3-D system and with a between-group comparison for both systems.

Results

Both system showed to be test-retest reliable, both in group 1 (2-D system: ICC3.1_agreement 0.52–0.83; 3-D system: ICC3.1_agreement 0.81–0.95) and in group 2 (3-D system: ICC3.1_agreement 0.33–0.92; 2-D system: ICC3.1_agreement 0.54–0.95). The 2-D system was also inter-rater reliable (group 1: ICC2.1_agreement 0.80–0.92; group 2: ICC2.1_agreement 0.39–0.90). The within-group comparison of the 3-D system revealed a statistically significant asymmetry of 0.4°-0.5° in group 1 and no statistically significant asymmetry in group 2. The between-group comparison revealed that the maximum amplitude towards the residual limb (MARL) in the low back (3-D system) and the (residual) limb—trunk angle (2-D system) were significantly larger with a mean difference of 1.2° and 6.4°, respectively, than the maximum amplitude of healthy subjects. However, these average differences were smaller than the smallest detectable change (SDC) of group 1 for both the MARL (SDC_agreement: 1.5°) and the residual limb—trunk angle (SDC_agreement: 6.7°-7.6°).

Conclusion

The 3-D and 2-D systems tested in this study were not sensitive enough to detect real differences within and between participants with a lower extremity amputation and healthy subjects although promising reproducibility parameters for some of the outcome measures.

Low back pain in persons with lower extremity amputation: a systematic review of the literature

BACKGROUND CONTEXT

Lower extremity amputation (LEA) is associated with an elevated risk for development and progression of secondary health conditions. Low back pain (LBP) is one such condition adversely affecting function, independence, and quality of life.

PURPOSE

The purpose of this study was to systematically review the literature to determine the strength of evidence relating the presence and severity of LBP secondary to LEA, thereby supporting the formulation of empirical evidence statements (EESs) to guide practice and future research.

STUDY DESIGN/SETTING

Systematic review of the literature.

METHODS

A systematic review of five databases was conducted followed by evaluation of evidence and synthesis of EESs.

RESULTS

Seventeen manuscripts were included. From these, eight EESs were synthesized within the following categories: epidemiology, amputation level, function, disability, leg length, posture, spinal kinematics, and osseointegrated prostheses. Only the EES on epidemiology was supported by evidence at the moderate confidence level given support by eight moderate quality studies. The four EESs for amputation level, leg length, posture, and spinal kinematics were supported by evidence at the low confidence level given that each of these statements had some evidence not supporting the statement but ultimately more evidence (and of higher quality) currently supporting the statement. The remaining three EESs that addressed function, disability and osseointegrated prosthetic use were all supported by single studies or had comparable evidence that disagreed with study findings rendering insufficient evidence to support the respective EES.

CONCLUSIONS

Based on the state of the current evidence, appropriate preventative and, particularly, treatment strategies to manage LBP in persons with LEA remain a knowledge gap and an area of future study.

Trunk muscle forces and spinal loads in persons with unilateral transfemoral amputation during sit-to-stand and stand-to-sit activities

BACKGROUND

Alterations and asymmetries in trunk motions during activities of daily living, involving lower extremities, are suggested to cause higher spinal loads in persons with unilateral lower limb amputation. Given the repetitive nature of most activities of daily living, knowledge of the amount of increase in spinal loads is important for designing interventions aimed at prevention of secondary low back pain due to potential fatigue failure of spinal tissues. The objective of this study was to determine differences in trunk muscle forces and spinal loads between persons with and without lower limb amputation when performing sit-to-stand and stand-to-sit tasks.

METHODS

Kinematics of the pelvis and thorax, obtained from ten males with unilateral transfemoral lower limb amputation and 10 male uninjured controls when performing sit-to-stand and stand-to-sit activities, were used within a non-linear finite element model of the spine to estimate trunk muscle forces and resultant spinal loads.

FINDINGS

The peak compression force, medio-lateral (only during stand-to-sit), and antero-posterior shear forces were respectively 348 N, 269 N, and 217 N larger in person with vs. without amputation. Persons with amputation also experienced on average 171 N and 53 N larger mean compression force and medio-lateral shear force, respectively.

INTERPRETATION

While spinal loads were larger in persons with amputation, these loads were generally smaller than the reported threshold for spinal tissue injury. However, a rather small increase in spinal loads during common activities of daily living like walking, sit-to-stand, and stand-to-sit may nevertheless impose a significant risk of fatigue failure for spinal tissues due to the repetitive nature of these activities.

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.

Reference values for gait temporal and loading symmetry of lower-limb amputees can help in refocusing rehabilitation targets

Background

The literature suggests that optimal levels of gait symmetry might exist for lower-limb amputees. Not only these optimal values are unknown, but we also don’t know typical symmetry ratios or which measures of symmetry are essential. Focusing on the symmetries of stance, step, first peak and impulse of the ground reaction force, the aim of this work was to answer to three methodological and three clinical questions. The methodological questions wanted to establish a minimum set of symmetry indexes to study and if there are limitations in their calculations. The clinical questions wanted to establish if typical levels of temporal and loading symmetry exist, and change with the level of amputation and prosthetic components.

Methods

Sixty traumatic, K3-K4 amputees were involved in the study: 12 transfemoral mechanical knee users (TFM), 25 C-leg knee users (TFC), and 23 transtibial amputees (TT). Ninety-two percent used the Ossur Variflex foot. Ten healthy subjects were also included. Ground reaction force from both feet were collected with the Novel Pedar-X. Symmetry indexes were calculated and statistically compared with regression analyses and non-parametric analysis of variance among subjects.

Results

Stance symmetry can be reported instead of step, but it cannot substitute impulse and first peak symmetry. The first peak cannot always be detected on all amputees. Statistically significant differences exist for stance symmetry among all groups, for impulse symmetry between TFM and TFC/TT, for first peak symmetry between transfemoral amputees altogether and TT. Regarding impulse symmetry, 25% of TFC and 43% of TT had a higher impulse on the prosthetic side. Regarding first peak symmetry, 59% of TF and 30% of TT loaded more the prosthetic side.

Conclusions

Typical levels of symmetry for stance, impulse and first peak change with the level of amputation and componentry. Indications exist that C-leg and energy-storage-and-return feet can improve symmetry. Results are suggestive of two mechanisms related to sound side knee osteoarthritis: increased impulse for TF and increased first peak for TT. These results can be useful in clinics to set rehabilitation targets, understand the advancements of a patient during gait retraining, compare and chose components and possibly rehabilitation programs.

Impact of Powered Knee-Ankle Prosthesis on Low Back Muscle Mechanics in Transfemoral Amputees: A Case Series

Regular use of prostheses is critical for individuals with lower limb amputations to achieve everyday mobility, maintain physical and physiological health, and achieve a better quality of life. Use of prostheses is influenced by numerous factors, with prosthetic design playing a critical role in facilitating mobility for an amputee. Thus, prostheses design can either promote biomechanically efficient or inefficient gait behavior. In addition to increased energy expenditure, inefficient gait behavior can expose prosthetic user to an increased risk of secondary musculoskeletal injuries and may eventually lead to rejection of the prosthesis. Consequently, researchers have utilized the technological advancements in various fields to improve prosthetic devices and customize them for user specific needs. One evolving technology is powered prosthetic components. Presently, an active area in lower limb prosthetic research is the design of novel controllers and components in order to enable the users of such powered devices to be able to reproduce gait biomechanics that are similar in behavior to a healthy limb. In this case series, we studied the impact of using a powered knee-ankle prostheses (PKA) on two transfemoral amputees who currently use advanced microprocessor controlled knee prostheses (MPK). We utilized outcomes pertaining to kinematics, kinetics, metabolics, and functional activities of daily living to compare the efficacy between the MPK and PKA devices. Our results suggests that the PKA allows the participants to walk with gait kinematics similar to normal gait patterns observed in a healthy limb. Additionally, it was observed that use of the PKA reduced the level of asymmetry in terms of mechanical loading and muscle activation, specifically in the low back spinae regions and lower extremity muscles. Further, the PKA allowed the participants to achieve a greater range of cadence than their predicate MPK, thus allowing them to safely ambulate in variable environments and dynamically control speed changes. Based on the results of this case series, it appears that there is considerable potential for powered prosthetic components to provide safe and efficient gait for individuals with above the knee amputation.

Walking speed differentially alters spinal loads in persons with traumatic lower limb amputation

Persons with lower limb amputation (LLA) perceive altered motions of the trunk/pelvis during activities of daily living as contributing factors for low back pain. When walking (at a singular speed), larger trunk motions among persons with vs. without LLA are associated with larger spinal loads; however, modulating walking speed is necessary in daily life and thus understanding the influences of walking speed on spinal loads in persons with LLA is of particular interest here. Three-dimensional trunk-pelvic kinematics, collected during level-ground walking at self-selected (SSW) and two controlled speeds (∼1.0 and ∼1.4 m/s), were obtained for seventy-eight participants: 26 with transfemoral and 26 with transtibial amputation, and 26 uninjured controls (CTR). Using a kinematics-driven, non-linear finite element model of the lower back, the resultant compressive and mediolateral/anteroposterior shear loads at the L5/S1 spinal level were estimated. Peak values were extracted and compiled. Despite walking slower at SSW speeds (∼0.21 m/s), spinal loads were 8-14% larger among persons with transfemoral amputation vs. CTR. Across all participants, peak compressive, mediolateral, and anteroposterior shear loads increased with increasing walking speed. At the fastest (vs. slowest) controlled speed, these increases were respectively 24-84% and 29-77% larger among persons with LLA relative to CTR. Over time, repeated exposures to these increased spinal loads, particularly at faster walking speeds, may contribute to the elevated risk for low back pain among persons with LLA. Future work should more completely characterize relative risk in daily life between persons with vs. without LLA by analyzing additional activities and tissue-level responses.

Aprovechamiento de energía, cinemática y estabilidad en la marcha de un paciente con amputación transfemoral sin abordaje de rehabilitación

Introducción. Los pacientes con amputación de miembros inferiores presentan marcadas asimetrías en la marcha, las cuales pueden aumentar cuando no se cumple con un adecuado proceso de rehabilitación, comprometiendo los objetivos fundamentales de la marcha e incrementando factores de riesgo.Objetivo. Analizar el grado de aprovechamiento de energía mecánica, la estabilidad dinámica y las variables cinemáticas de interés clínico en la marcha de un paciente con amputación transfemoral que no realizó el proceso de rehabilitación.Materiales y métodos. Con base en una reconstrucción 3D, se cuantificaron valores angulares para cadera, rodilla y tobillo y se estimó el intercambio de energía mecánica y la estabilidad dinámica en tres velocidades de marcha diferentes.Resultados. Se observaron variaciones en los parámetros espaciotemporales con el cambio de la velocidad que no son consistentes con los encontrados en otros estudios de amputados. Los valores angulares, principalmente a nivel de rodilla y tobillo, presentan asimetrías que se pueden asociar con una disminución en el aprovechamiento de energía mecánica mientras aumenta la estabilidad en diferentes velocidades.Conclusión. El uso de prótesis en las condiciones en las que fue realizada la evaluación compromete la recuperación de energía mecánica en la marcha del paciente.

The Effect of Lumbar Disc Herniation on Musculoskeletal Loadings in the Spinal Region During Level Walking and Stair Climbing

Background

People with low back pain (LBP) alter their motion patterns during level walking and stair climbing due to pain or fear. However, the alternations of load sharing during the two activities are largely unknown. The objective of this study was to investigate the effect of LBP caused by lumbar disc herniation (LDH) on the muscle activities of 17 main trunk muscle groups and the intradiscal forces acting on the five lumbar discs.

Material/Methods

Twenty-six healthy adults and seven LDH patients were recruited to perform level walking and stair climbing in the Gait Analysis Laboratory. Eight optical markers were placed on the bony landmarks of the spinous process and pelvis, and the coordinates of these markers were captured during the two activities using motion capture system. The coordinates of the captured markers were applied to developed musculoskeletal model to calculate the kinetic variables.

Results

LDH patients demonstrated higher muscle activities in most trunk muscle groups during both level walking and stair climbing. There were decreases in anteroposterior shear forces on the discs in the pathological region and increases in the compressive forces on all the lumbar discs during level walking. The symmetry of mediolateral shear forces was worse in LDH patients than healthy adults during stair climbing.

Conclusions

LDH patients exhibited different kinetic alternations during level walking and stair climbing. However, both adaptive strategies added extra burdens to the trunk system and further increased the risk for development of LDH.

Long-term outcomes following lower extremity press-fit bone-anchored prosthesis surgery: a 5-year longitudinal study protocol

BACKGROUND

Patients with lower extremity amputation frequently suffer from socket-related problems. This seriously limits prosthesis use, level of activity and health-related quality of life (HRQoL). An additional problem in patients with lower extremity amputation are asymmetries in gait kinematics possibly accounting for back pain. Bone-anchored prostheses (BAPs) are a possible solution for socket-related problems. Knowledge concerning the level of function, activity and HRQoL after surgery is limited. The aims of this ongoing study are to: a) describe changes in the level of function, activity, HRQoL and satisfaction over time compared to baseline before surgery; b) examine potential predictors for changes in kinematics, prosthetic use, walking ability, HRQoL, prosthesis comfort over time and level of stump pain at follow-up; c) examine potential mechanisms for change of back pain over time by identifying determinants, moderators and mediators.

METHODS/DESIGN

A prospective 5-year longitudinal study with multiple follow-ups. All adults, between May 2014 and May 2018, with lower extremity amputation receiving a press-fit BAP are enrolled consecutively. Patients with socket-related problems and trauma, tumour resection or stable vascular disease as cause of primary amputation will be included. Exclusion criteria are severe cognitive or psychiatric disorders. Follow-ups are planned at six-months, one-, two- and five-years after BAP surgery. The main study outcomes follow, in part, the ICF classification: a) level of function defined as kinematics in coronal plane, hip abductor strength, prosthetic use, back pain and stump pain; b) level of activity defined as mobility level and walking ability; c) HRQoL; d) satisfaction defined as prosthesis comfort and global perceived effect. Changes over time for the continuous outcomes and the dichotomized outcome (back pain) will be analysed using generalised estimating equations (GEE). Multivariate GEE will be used to identify potential predictors for change of coronal plane kinematics, prosthetic use, walking ability, HRQoL, prosthesis comfort and for the level of post-operative stump pain. Finally, potential mechanisms for change in back pain frequency will be explored using coronal plane kinematics as a potential determinant, stump pain as moderator and hip abductor strength as mediator.

DISCUSSION

This study may identify predictors for clinically relevant outcome measures.

TRIAL REGISTRATION

NTR5776 . Registered 11 March 2016, retrospectively registered.

Evaluation of Direct Collocation Optimal Control Problem Formulations for Solving the Muscle Redundancy Problem

Estimation of muscle forces during motion involves solving an indeterminate problem (more unknown muscle forces than joint moment constraints), frequently via optimization methods. When the dynamics of muscle activation and contraction are modeled for consistency with muscle physiology, the resulting optimization problem is dynamic and challenging to solve. This study sought to identify a robust and computationally efficient formulation for solving these dynamic optimization problems using direct collocation optimal control methods. Four problem formulations were investigated for walking based on both a two and three dimensional model. Formulations differed in the use of either an explicit or implicit representation of contraction dynamics with either muscle length or tendon force as a state variable. The implicit representations introduced additional controls defined as the time derivatives of the states, allowing the nonlinear equations describing contraction dynamics to be imposed as algebraic path constraints, simplifying their evaluation. Problem formulation affected computational speed and robustness to the initial guess. The formulation that used explicit contraction dynamics with muscle length as a state failed to converge in most cases. In contrast, the two formulations that used implicit contraction dynamics converged to an optimal solution in all cases for all initial guesses, with tendon force as a state generally being the fastest. Future work should focus on comparing the present approach to other approaches for computing muscle forces. The present approach lacks some of the major limitations of established methods such as static optimization and computed muscle control while remaining computationally efficient.

Persons with unilateral transfemoral amputation experience larger spinal loads during level-ground walking compared to able-bodied individuals

BACKGROUND

Persons with lower limb amputation walk with increased and asymmetric trunk motion; a characteristic that is likely to impose distinct demands on trunk muscles to maintain equilibrium and stability of the spine. However, trunk muscle responses to such changes in net mechanical demands, and the resultant effects on spinal loads, have yet to be determined in this population.

METHODS

Building on a prior study, trunk and pelvic kinematics collected during level-ground walking from 40 males (20 with unilateral transfemoral amputation and 20 matched controls) were used as inputs to a kinematics-driven, nonlinear finite element model of the lower back to estimate forces in 10 global (attached to thorax) and 46 local (attached to lumbar vertebrae) trunk muscles, as well as compression, lateral, and antero-posterior shear forces at all spinal levels.

FINDINGS

Trunk muscle force and spinal load maxima corresponded with heel strike and toe off events, and among persons with amputation, were respectively 10-40% and 17-95% larger during intact vs. prosthetic stance, as well as 6-80% and 26-60% larger during intact stance relative to controls.

INTERPRETATION

During gait, larger spinal loads with transfemoral amputation appear to be the result of a complex pattern of trunk muscle recruitment, particularly involving co-activation of antagonistic muscles during intact limb stance; a period when these individuals are confident and likely to use the trunk to assist with forward progression. Given the repetitive nature of walking, repeated exposure to such elevated loading likely increases the risk for low back pain in this population.