Knee adduction moment peak and impulse do not change during the first six months of walking with a prosthesis

BACKGROUND

Individuals with unilateral lower limb loss are at increased risk for developing knee osteoarthritis in their contralateral limb. The mechanisms underlying this phenomenon are unknown, but large or unusual loads on the limb are thought to contribute to osteoarthritis development. Yet, to our knowledge, there have been no longitudinal assessments of knee joint kinetics to assist with identifying the origin or progression of such loads.

RESEARCH QUESTION

This study aimed to examine knee joint kinetics of individuals with lower limb loss as a function of time from independent ambulation.

METHODS

Eight male Service Members with unilateral lower limb loss (3 transfemoral/5 transtibial) completed gait analyses, walking at self-selected speed and cadence, at 0, 2, and 6 months following initial independent ambulation.

RESULTS

Although there was a significant time effect on stride length (p = 0.047), there were no pairwise differences (all p ≥ 0.152). Additionally, there was not a significant effect of time on the peak (p = 0.666), loading rate (p = 0.336), or impulse (p = 0.992) of knee adduction moment (KAM), peak knee flexion moment (KFM) (p = 0.128), or the peak (p = 0.485) or loading rate (p = 0.130) of vertical ground reaction force (VGRF).

SIGNIFICANCE

The results of the current study demonstrate that major features of knee joint loading do not change over the first 6 months of independently walking with a prosthesis. The magnitude of these loads are similar to loads observed in individuals with lower limb loss further from injury/initial ambulation, but the present results do not imply that no changes occur after 6 months.

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.

The Center for Rehabilitation Sciences Research: Advancing the Rehabilitative Care for Service Members With Complex Trauma

The Center for Rehabilitation Sciences Research (CRSR) was established to advance the rehabilitative care for service members with combat-related injuries, particularly those with orthopedic, cognitive, and neurological complications. The center supports comprehensive research projects to optimize treatment strategies and promote the successful return to duty and community reintegration of injured service members. The center also provides a unique platform for fostering innovative research and incorporating clinical/technical advances in the rehabilitative care for service members. CRSR is composed of four research focus areas: (1) identifying barriers to successful rehabilitation and reintegration, (2) improving pain management strategies to promote full participation in rehabilitation programs, (3) applying novel technologies to advance rehabilitation methods and enhance outcome assessments, and (4) transferring new technology to improve functional capacity, independence, and quality of life. Each of these research focus areas works synergistically to influence the quality of life for injured service members. The purpose of this overview is to highlight the clinical research efforts of CRSR, namely how this organization engages a broad group of interdisciplinary investigators from medicine, biology, engineering, anthropology, and physiology to help solve clinically relevant problems for our service members, veterans, and their families.

Impact of Traumatic Lower Extremity Injuries Beyond Acute Care: Movement-Based Considerations for Resultant Longer Term Secondary Health Conditions

Significance: Advances in field-based trauma care, surgical techniques, and protective equipment have collectively facilitated the survival of a historically large number of service members (SMs) following combat trauma, although many sustained significant composite tissue injuries to the extremities, including limb loss (LL) and limb salvage (LS). Beyond the acute surgical and rehabilitative efforts that focus primarily on wound care and restoring mobility, traumatic LL and LS are associated with several debilitating longer term secondary health conditions (e.g., low back pain [LBP], osteoarthritis [OA], and cardiovascular disease [CVD]) that can adversely impact physical function and quality of life. Recent Advances: Despite recent advancements in prosthetic and orthotic devices, altered movement and mechanical loading patterns have been identified among persons with LL and salvage, which are purported risk factors for the development of longer term secondary musculoskeletal conditions and may limit functional outcomes and/or concomitantly impact cardiovascular health. Critical Issues: The increased prevalence of and risk for LBP, OA, and CVD among the relatively young cohort of SMs with LL and LS significantly impact physiological and psychological well-being, particularly over the next several decades of their lives. Future Directions: Longitudinal studies are needed to characterize the onset, progression, and recurrence of health conditions secondary to LL and salvage. While not a focus of the current review, detailed characterization of physiological biomarkers throughout the rehabilitation process may provide additional insight into the current understanding of disease processes of the musculoskeletal and cardiovascular systems.

Locomotor adaptability in persons with unilateral transtibial amputation

Background

Locomotor adaptation enables walkers to modify strategies when faced with challenging walking conditions. While a variety of neurological injuries can impair locomotor adaptability, the effect of a lower extremity amputation on adaptability is poorly understood.

Objective

Determine if locomotor adaptability is impaired in persons with unilateral transtibial amputation (TTA).

Methods

The locomotor adaptability of 10 persons with a TTA and 8 persons without an amputation was tested while walking on a split-belt treadmill with the parallel belts running at the same (tied) or different (split) speeds. In the split condition, participants walked for 15 minutes with the respective belts moving at 0.5 m/s and 1.5 m/s. Temporal spatial symmetry measures were used to evaluate reactive accommodations to the perturbation, and the adaptive/de-adaptive response.

Results

Persons with TTA and the reference group of persons without amputation both demonstrated highly symmetric walking at baseline. During the split adaptation and tied post-adaptation walking both groups responded with the expected reactive accommodations. Likewise, adaptive and de-adaptive responses were observed. The magnitude and rate of change in the adaptive and de-adaptive responses were similar for persons with TTA and those without an amputation. Furthermore, adaptability was no different based on belt assignment for the prosthetic limb during split adaptation walking.

Conclusions

Reactive changes and locomotor adaptation in response to a challenging and novel walking condition were similar in persons with TTA to those without an amputation. Results suggest persons with TTA have the capacity to modify locomotor strategies to meet the demands of most walking conditions despite challenges imposed by an amputation and use of a prosthetic limb.

A computational algorithm for classifying step and spin turns using pelvic center of mass trajectory and foot position

Transient changes in direction during ambulation are typically performed using a step (outside) or spin (inside) turning strategy, often identified through subjective and time-consuming visual rating. Here, we present a computational, marker-based classification method utilizing pelvic center of mass (pCOM) trajectory and time-distance parameters to quantitatively identify turning strategy. Relative to visual evaluation by three independent raters, sensitivity, specificity, and overall accuracy of the pCOM-based classification method were evaluated for 90-degree turns performed by 3 separate populations (5 uninjured controls, 5 persons with transtibial amputation, and 5 persons with transfemoral amputation); each completed turns using two distinct cueing paradigms (i.e., laser-guided "freeform" and verbally-guided "forced" turns). Secondarily, we compared the pCOM-based turn classification method to adapted versions of two existing computational turn classifiers which utilize trunk and shank angular velocities (AV). Among 366 (of 486 total) turns with unanimous intra- and inter-rater agreement, the pCOM-based classification algorithm was 94.5% accurate, with 96.6% sensitivity (accuracy of spin turn classification), and 93.5% specificity (accuracy of step turn classification). The pCOM-based algorithm (vs. both AV-based methods) was more accurate (94.5% vs. 81.1-80.6%; P<0.001) overall, as well as specifically in freeform (92.9 vs. 80.4-76.8%; P<0.003) and forced (96.0 vs. 83.8-81.8%; P<0.001) cueing, and among individuals with (92.4 vs. 80.2-78.8%; P<0.001) and without (99.1 vs. 86.2-80.8%; P<0.001) amputation. The pCOM-based algorithm provides an efficient and objective method to accurately classify 90-degree turning strategies using optical motion capture in a laboratory setting, and may be extended to various cueing paradigms and/or populations with altered gait.

A comparison of kinematic-based gait event detection methods in a self-paced treadmill application

Kinematic-based algorithms for detecting gait events are efficient and useful in the absence of (reliable) kinetic data. However, the validity of these kinematic-based algorithms for self-paced treadmill walking is unknown, particularly given the influence of walking speed on such data. We quantified offsets in event detection of four foot kinematics-based algorithms (horizontal position, horizontal velocity, vertical velocity, and sagittal resultant velocity) relative to events determined by a threshold in vertical ground reaction force among seven uninjured individuals - and nine with unilateral transtibial amputation - walking on a self-paced treadmill. Across walking speeds from 0.48-1.64m/s (0.5-31.7% CV), offsets ranged from -7 to +3 frames (≈83.3ms) in heel strike, and -3 to +5 frames (≈66.6 ms) in toe off. Regardless of method, offsets in heel strike were not influenced (-0.01<r<0.01, all P>0.61) by variability in walking speed. However, offsets in toe-off were positively correlated with variability in walking speed for the horizontal position (r=0.539; P<0.001) and velocity (r=0.463; P<0.001) algorithms, and negatively correlated (r=-0.317; P<0.001) for the vertical velocity algorithm; offsets from the sagittal resultant velocity algorithm, with thresholds adjusted for walking speed, were not strongly associated (r=0.126; P=0.27). Although relatively minimal offsets support the applicability of these algorithms to self-paced walking, for individuals with asymptomatic and pathological gait patterns, sagittal resultant velocity of the foot produces the most consistent event detection over the widest range of (and variability in) walking speeds.

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.

Persons with unilateral transfemoral amputation have altered lumbosacral kinetics during sitting and standing movements

Increases in spinal loading have been related to altered movements of the lower back during gait among persons with lower limb amputation, movements which are self-perceived by these individuals as contributing factors in the development of low back pain. However, the relationships between altered trunk kinematics and associated changes in lumbosacral kinetics during sit-to-stand and stand-to-sit movements in this population have not yet been assessed. Three-dimensional lumbosacral kinetics (joint moments and powers) were compared between 9 persons with unilateral transfemoral amputation (wearing both a powered and passive knee device), and 9 uninjured controls, performing five consecutive sit-to-stand and stand-to-sit movements. During sit-to-stand movements, lumbosacral joint moments and powers were significantly larger among persons with transfemoral amputation relative to uninjured controls. During stand-to-sit movements, lumbosacral joint moments and powers were also significantly larger among persons with transfemoral amputation relative to uninjured controls, with the exception of sagittal joint powers. Minimal differences in kinetic measures were noted between the powered and passive knee devices among persons with transfemoral amputation across all conditions. Altered lumbosacral kinetics during sitting and standing movements, important activities of daily living, may play a biomechanical role in the onset and/or recurrence of low back pain or injury among persons with lower-limb amputation.

Does intact limb loading differ in servicemembers with traumatic lower limb loss?

BACKGROUND

The initiation and progression of knee and hip arthritis have been related to limb loading during ambulation. Although altered gait mechanics with unilateral lower limb loss often result in larger and more prolonged forces through the intact limb, how these forces differ with traumatic limb loss and duration of ambulation have not been well described.

QUESTIONS/PURPOSES

The purpose of this study was to determine whether biomechanical variables of joint and limb loading (external adduction moments, vertical ground reaction force loading rates, and impulses) are larger in the intact limb of servicemembers with versus without unilateral lower limb loss and whether intact limb loading differs between shorter (≤ 6 months) versus longer (≥ 2 years) durations of ambulation with a prosthesis.

METHODS

A retrospective review was conducted of all clinical and research gait evaluations performed in the biomechanics laboratory at Walter Reed Army Medical Center and Walter Reed National Military Medical Center between January 2008 and December 2012. Biomechanical data meeting all inclusion and exclusion criteria were obtained for 32 individuals with unilateral transtibial limb loss, 49 with unilateral transfemoral limb loss, and 28 without limb loss. Individuals with unilateral lower limb loss were separated by their experience ambulating with a prosthesis at the time of the gait collection, ≤ 6 months or ≥ 2 years, to determine the effect of duration of ambulation with a prosthesis.

RESULTS

Intact limb mean and peak vertical ground reaction force loading rates (median [range; 95% confidence interval]) were larger for transtibial subjects with ≤ 6 months of experience ambulating with a prosthesis versus control subjects (mean: 12.13 body weight [BW]/s [4.45-16.79; 10.18-12.81] versus 9.03 BW/s [4.64-14.47; 8.26-9.74]; effect size [ES] = 0.40; p = 0.003; and peak: 17.23 BW/s [6.58-25.25; 15.46-19.01] versus 13.60 BW/s [9.82-19.51; 12.98-15.05]; ES = 0.43; p = 0.001), respectively. Intact limb mean and peak vertical ground reaction force loading rates were also larger in subjects with transfemoral limb loss with ≤ 6 months and ≥ 2 years of experience ambulating with a prosthesis versus control subjects (mean: 12.67 BW/s [5.88-18.15; 11.06-14.47] and 12.59 BW/s [8.08-17.39; 11.83-13.68] versus 9.03 BW/s [4.64-14.47; 8.26-9.74]; ES ≥ 0.53; p < 0.001; peak: 19.82 BW/s [11.93-29.43; 18.35-23.05] and 21.33 BW/s [16.68-36.69; 20.66-24.26] versus 13.60 BW/s [9.82-19.51; 12.98-15.05]; ES ≥ 0.68; p < 0.001, respectively). Similarly, intact limb vertical ground reaction force impulses (0.63 BW·s [0.53-0.81; 0.67-0.69] and 0.62 BW·s [0.55-0.74; 0.60-0.63] versus 0.57 BW·s [0.50-0.66; 0.55-0.58]; ES ≥ 0.53, p < 0.001) were also larger among both groups of transfemoral subjects versus control subjects, respectively. Limb loading variables were not statistically different between times ambulating with a prosthesis within groups with transtibial or transfemoral limb loss.

CONCLUSIONS

Larger intact limb loading in individuals with traumatic transtibial loss were only noted early in the rehabilitation process, but these variables were present early and late in the rehabilitation process for those with transfemoral limb loss. Such evidence suggests an increased risk for early onset and progression of arthritis in the intact limb, especially in those with transfemoral limb loss.

CLINICAL RELEVANCE

Interventions should focus on correcting modifiable gait mechanics associated with arthritis, particularly among individuals with transfemoral limb loss, to potentially mitigate the development and progression in this population.

Mediolateral joint powers at the low back among persons with unilateral transfemoral amputation

OBJECTIVE

To analyze mediolateral joint powers at the low back during gait among persons with and without unilateral transfemoral amputation to better understand the functional contributions of tissues in and around the low back to altered lateral trunk movements in this population.

DESIGN

Retrospective analysis of biomechanical gait data.

SETTING

Gait laboratory.

PARTICIPANTS

Twenty persons with unilateral transfemoral amputation and 20 uninjured controls (N=40).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Net joint powers, and total generation (+) and absorption (-) energies, at the low back (L5/S1 spinal level) were analyzed in the frontal plane using inverse dynamics analyses on over-ground gait data collected at self-selected walking speeds (∼1.3m/s).

RESULTS

Compared with uninjured controls, 4 distinctly larger positive phases of mediolateral joint power at L5/S1 were evident in persons with transfemoral amputation, occurring before and after each heel strike. Total generation energies throughout the gait cycle were also larger (P<.001) among persons with transfemoral amputation (4.8±1.4J) than among uninjured controls (1.3±0.7J).

CONCLUSIONS

Larger positive phases of joint power at L5/S1 in the frontal plane support previous suggestions that persons with transfemoral amputation use a more active mediolateral trunk movement strategy, although such an active trunk movement strategy with transfemoral amputation may contribute to higher metabolic energy expenditures and low back pain risk.

Three-dimensional joint reaction forces and moments at the low back during over-ground walking in persons with unilateral lower-extremity amputation

BACKGROUND

Abnormal mechanics of locomotion following lower-extremity amputation are associated with increases in trunk motion, which in turn may alter loads at the low back due to changes in inertial and gravitational demands on the spine and surrounding trunk musculature.

METHODS

Over-ground gait data were retrospectively compiled from two groups walking at similar self-selected speeds (~1.35m/s): 40 males with unilateral lower-extremity amputation (20 transtibial, 20 transfemoral) and 20 able-bodied male controls. Three-dimensional joint reaction forces and moments at the low back (L5/S1 spinal level) were calculated using top-down and bottom-up approaches. Peak values and the timings of these were determined and compared between and within (bilaterally) groups, and secondarily between approaches.

FINDINGS

Peak laterally-directed joint reaction forces and lateral bend moments increased with increasing level of amputation, and were respectively 83% and 41% larger in prosthetic vs. intact stance among persons with transfemoral amputation. Peak anteriorly-directed reaction forces and extension moments were 31% and 55% larger, respectively, among persons with transtibial amputation compared to controls. Peak vertical reaction forces and axial twist moments were similar between and within groups. Peak joint reaction forces and moments were larger (3-14%), and the respective timing of these sooner (11-62ms), from the bottom-up vs. top-down approach.

INTERPRETATION

Increased and asymmetric peak reaction forces and moments at the low back among persons with unilateral lower-extremity amputation, particularly in the frontal plane, suggest potential mechanistic pathways through which repeated exposure to altered trunk motion and spinal loading may contribute to low-back injury risk among persons with lower-extremity amputation.

Kinematic analysis of males with transtibial amputation carrying military loads

The biomechanical responses to load carriage, a common task for dismounted troops, have been well studied in nondisabled individuals. However, with recent shifts in the rehabilitation and retention process of injured servicemembers, there remains a substantial need for understanding these responses in persons with lower-limb amputations. Temporal-spatial and kinematic gait parameters were analyzed among 10 male servicemembers with unilateral transtibial amputation (TTA) and 10 uninjured male controls. Participants completed six treadmill walking trials in all combinations of two speeds (1.34 and 1.52 m/s) and three loads (none, 21.8, and 32.7 kg). Persons with TTA exhibited biomechanical compensations to carried loads that are comparable to those observed in uninjured individuals. However, several distinct gait changes appear to be unique to those with TTA, notably, increased dorsiflexion (deformation) of the prosthetic foot/ankle, less stance knee flexion on the prosthetic limb, and altered trunk forward lean/excursion. Such evidence supports the need for future work to assess the risk for overuse injuries with carried loads in this population in addition to guiding the development of adaptive prosthetic feet/components to meet the needs of redeployed servicemembers or veterans/civilians in physically demanding occupations.

Altered flexion-relaxation responses exist during asymmetric trunk flexion movements among persons with unilateral lower-limb amputation

Repetitive exposures to altered gait and movement following lower-limb amputation (LLA) have been suggested to contribute to observed alterations in passive tissue properties and neuromuscular control in/surrounding the lumbar spine. These alterations, in turn, may affect the synergy between passive and active tissues during trunk movements. Eight males with unilateral LLA and eight non-amputation controls completed quasi-static trunk flexion-extension movements in seven distinct conditions of rotation in the transverse plane: 0° (sagittally-symmetric), ±15°, ±30°, and ±45° (sagittally-asymmetric). Electromyographic (EMG) activity of the bilateral lumbar erector spinae and lumbar kinematics were simultaneously recorded. Peak lumbar flexion and EMG-off angles were determined, along with the difference ("DIFF") between these two angles and the magnitude of peak normalized EMG activities. Persons with unilateral LLA exhibited altered and asymmetric synergies between active and passive trunk tissues during both sagittally-symmetric and -asymmetric trunk flexion movements. Specifically, decreased and asymmetric passive contributions to trunk movements were compensated with increases in the magnitude and duration of active trunk muscle responses. Such alterations in trunk passive and active neuromuscular responses may result from repetitive exposures to abnormal gait and movement subsequent to LLA, and may increase the risk for LBP in this population.

Persons with lower-limb amputation have impaired trunk postural control while maintaining seated balance

Abnormal mechanics of movement resulting from lower-limb amputation (LLA) may increase stability demands on the spinal column and/or alter existing postural control mechanisms and neuromuscular responses. A seated balance task was used to investigate the effects of LLA on trunk postural control and stability, among eight males with unilateral LLA (4 transtibial, 4 transfemoral), and eight healthy, non-amputation controls (matched by age, stature, and body mass). Traditional measures derived from center of pressure (COP) time series, and measures obtained from non-linear stabilogram diffusion analyses, were used to characterize trunk postural control. All traditional measures of postural control (95% ellipse area, RMS distance, and mean velocity) were significantly larger among participants with LLA. Non-linear stabilogram diffusion analyses also revealed significant differences in postural control among persons with LLA, but only in the antero-posterior direction. Normalized trunk muscle activity was also larger among participants with LLA. Larger COP-based sway measures among participants with LLA during seated balance suggest an association between LLA and reduced trunk postural control. Reductions in postural control and spinal stability may be a result of adaptations in functional tissue properties and/or neuromuscular responses, and may potentially be caused by repetitive exposure to abnormal gait and movement. Such alterations could then lead to an increased risk for spinal instability, intervertebral motions beyond physiological limits, and pain.