A review of through-knee amputation.

OBJECTIVES: Through-knee amputation is an umbrella term for several different surgical techniques, which may affect clinical and functional outcomes. This makes it hard to evaluate the benefits and need for a through-knee amputation approach. This article seeks to (1) determine the number of through-knee amputation performed compared with other major lower limb amputations in England over the past decade; (2) identify the theoretical concepts behind through-knee amputation surgical approaches and their potential effect on functional and clinical outcomes and (3) provide a platform for discussion and research on through-knee amputation and surgical outcomes. METHODS: National Health Service Hospital Episodes Statistics were used to obtain recent numbers of major lower limb amputations in England. EMBASE and MEDLINE were searched using a systematic approach with predefined criteria for relevant literature on through-knee amputation surgery. RESULTS: In the past decade, 4.6% of major lower limb amputations in England were through-knee amputations. Twenty-six articles presenting through-knee amputation surgical techniques met our criteria. These articles detailed three through-knee amputation surgical techniques: the classical approach, which keeps the femur intact and retains the patella; the Mazet technique, which shaves the femoral condyles into a box shape and the Gritti-Stokes technique, which divides the femur proximal to the level of the condyles and attaches the patella at the distal cut femur. CONCLUSIONS: Through-knee amputation has persisted as a surgical approach over the past decade, with three core approaches identified. Studies reporting clinical, functional and biomechanical outcomes of through-knee amputation frequently fail to distinguish between the three distinct and differing approaches, making direct comparisons difficult. Future studies that compare through-knee amputation approaches to one another and to other amputation levels are needed.

Hip Joint Contact Loading and Muscle Forces During Running With a Transtibial Amputation.

People with unilateral transtibial amputations (TTA) have greater risks of bilateral hip osteoarthritis, related to asymmetric biomechanics compared to people without TTA. Running is beneficial for physical health and is gaining popularity. However, people with TTA may not have access to running-specific prostheses (RSPs), which are designed for running, and may instead run using their daily-use prosthesis (DUP). Differences in joint loading may result from prosthesis choice; thus, it is important to characterize changes in peak and impulsive hip joint contact loading during running. Six people with and without TTA ran at 3.5 m/s while ground reaction forces, kinematics, and electromyography were collected. People with TTA ran using their own RSP and DUP. Musculoskeletal models incorporating prosthesis type of each individual were used to quantify individual muscle forces and hip joint contact forces (HJCFs) during running. People using RSPs had smaller bilateral peak hip joint contact forces compared to when wearing DUPs during stance and swing, and a smaller impulse over the entire gait cycle. Greater amputated leg peak hip joint contact forces for people wearing DUPs compared to RSPs occurred with greater forces from the ipsilateral gluteus maximus during stance. People with TTA also had greater bilateral peak hip joint contact forces during swing compared to people without TTA, which occurred with greater peak gluteus medius forces. Running with more compliant RSPs may be beneficial for long-term joint health by reducing peak and impulsive hip loading compared to DUPs.

A Gesture-Controlled Rehabilitation Robot to Improve Engagement and Quantify Movement Performance.

Rehabilitation requires repetitive and coordinated movements for effective treatment, which are contingent on patient compliance and motivation. However, the monotony, intensity, and expense of most therapy routines do not promote engagement. Gesture-controlled rehabilitation has the potential to quantify performance and provide engaging, cost-effective treatment, leading to better compliance and mobility. We present the design and testing of a gesture-controlled rehabilitation robot (GC-Rebot) to assess its potential for monitoring user performance and providing entertainment while conducting physical therapy. Healthy participants (n = 11) completed a maze with GC-Rebot for six trials. User performance was evaluated through quantitative metrics of movement quality and quantity, and participants rated the system usability with a validated survey. For participants with self-reported video-game experience (n = 10), wrist active range of motion across trials (mean ± standard deviation) was 41.6 ± 13° and 76.8 ± 16° for pitch and roll, respectively. In the course of conducting a single trial with a time duration of 68.3 ± 19 s, these participants performed 27 ± 8 full wrist motion repetitions (i.e., flexion/extension), with a dose-rate of 24.2 ± 5 reps/min. These participants also rated system usability as excellent (score: 86.3 ± 12). Gesture-controlled therapy using the GC-Rebot demonstrated the potential to be an evidence-based rehabilitation tool based on excellent user ratings and the ability to monitor at-home compliance and performance.

Evaluating the Effects of Ankle-Foot Orthosis Mechanical Property Assumptions on Gait Simulation Muscle Force Results.

Musculoskeletal modeling and simulation techniques have been used to gain insights into movement disabilities for many populations, such as ambulatory children with cerebral palsy (CP). The individuals who can benefit from these techniques are often limited to those who can walk without assistive devices, due to challenges in accurately modeling these devices. Specifically, many children with CP require the use of ankle-foot orthoses (AFOs) to improve their walking ability, and modeling these devices is important to understand their role in walking mechanics. The purpose of this study was to quantify the effects of AFO mechanical property assumptions, including rotational stiffness, damping, and equilibrium angle of the ankle and subtalar joints, on the estimation of lower-limb muscle forces during stance for children with CP. We analyzed two walking gait cycles for two children with CP while they were wearing their own prescribed AFOs. We generated 1000-trial Monte Carlo simulations for each of the walking gait cycles, resulting in a total of 4000 walking simulations. We found that AFO mechanical property assumptions influenced the force estimates for all the muscles in the model, with the ankle muscles having the largest resulting variability. Muscle forces were most sensitive to assumptions of AFO ankle and subtalar stiffness, which should therefore be measured when possible. Muscle force estimates were less sensitive to estimates of damping and equilibrium angle. When stiffness measurements are not available, limitations on the accuracy of muscle force estimates for all the muscles in the model, especially the ankle muscles, should be acknowledged.

The Functional Roles of Muscles, Passive Prostheses, and Powered Prostheses During Sloped Walking in People With a Transtibial Amputation.

Sloped walking is challenging for individuals with transtibial amputation (TTA) due to the functional loss of the ankle plantarflexors. Prostheses that actively generate ankle power may help to restore this lost function. The purpose of this study was to use musculoskeletal modeling and simulation to quantify the mechanical power delivered to body segments by passive and powered prostheses and the remaining muscles in the amputated and intact legs during sloped walking. We generated walking simulations from experimental kinematic and kinetic data on slopes of 0, ±3 deg and ±6 deg in eight people with a TTA using powered and passive prostheses and eight nonamputees. Consistent with our hypothesis, the amputated leg hamstrings generated more power to both legs on uphill slopes in comparison with nonamputees, which may have implications for fatigue or overuse injuries. The amputated leg knee extensors delivered less power to the trunk on downhill slopes (effect size (ES) ≥ 1.35, p ≤ 0.02), which may be due to muscle weakness or socket instability. The power delivered to the trunk from the powered and passive prostheses was not significantly different (p > 0.05), However, using the powered prosthesis on uphill slopes reduced the contributions from the amputated leg hamstrings in all segments (ES ≥ 0.46, p ≤ 0.003), suggesting that added ankle power reduces the need for the hamstrings to compensate for lost ankle muscle function. Neither prosthesis replaced gastrocnemius function to absorb power from the trunk and deliver it to the leg on all slopes.

Changes in Mobility and Muscle Function of Children with Cerebral Palsy after Gait Training: A Pilot Study.

The goal of this pilot study was to characterize the effects of gait training on the capacity of muscles to produce body accelerations and relate these changes to mobility improvements seen in children with cerebral palsy (CP). Five children (14 years ± 3 y; GMFCS I-II) with spastic diplegic CP participated in a 6-week gait training program. Changes in 10-m fast-as-possible walking speed and 6-minute walking endurance were used to assess changes in mobility. In addition, musculoskeletal modeling was used to determine the potential of lower-limb muscles to accelerate the body's center of mass vertically and forward during stance. The mobility changes after the training were mixed, with some children demonstrating vast improvements, while others appeared to be minimal. However, the musculoskeletal results revealed unique responses for each child. The most common changes occurred in the capacity for the hip and knee extensors to produce body support and the hip flexors to produce body propulsion. These results cannot yet be generalized to the broad population of children with CP, but demonstrate that therapy protocols may be enhanced by modeling analyses. The pilot study results provide motivation for gait training emphasizing upright leg posture, mediolateral balance, and ankle push-off.

Does use of a powered ankle-foot prosthesis restore whole-body angular momentum during walking at different speeds?

BACKGROUND: Whole-body angular momentum (H) influences fall risk, is tightly regulated during walking, and is primarily controlled by muscle force generation. People with transtibial amputations using passive-elastic prostheses typically have greater H compared with nonamputees. QUESTIONS/PURPOSES: (1) Do people with unilateral transtibial amputations using passive-elastic prostheses have greater sagittal and frontal plane H ranges of motion during walking compared with nonamputees and compared with using powered prostheses? (2) Does use of powered ankle-foot prostheses result in equivalent H ranges in all planes of motion compared with nonamputees during walking as a result of normative prosthetic ankle power generation? METHODS: Eight patients with a unilateral transtibial amputation and eight nonamputees walked 0.75, 1.00, 1.25, 1.50, and 1.75 m/s while we measured kinematics and ground reaction forces. We calculated H for participants using their passive-elastic prosthesis and a powered ankle-foot prosthesis and for nonamputees at each speed. RESULTS: Patients using passive-elastic prostheses had 32% to 59% greater sagittal H ranges during the affected leg stance phase compared with nonamputees at 1.00 to 1.75 m/s (p < 0.05). Patients using passive-elastic prostheses had 5% and 9% greater sagittal H ranges compared with using powered prostheses at 1.25 and 1.50 m/s, respectively (p < 0.05). Participants using passive-elastic prostheses had 29% and 17% greater frontal H ranges at 0.75 and 1.50 m/s, respectively, compared with nonamputees (p < 0.05). Surprisingly, patients using powered prostheses had 26% to 50% greater sagittal H ranges during the affected leg stance phase compared with nonamputees at 1.00 to 1.75 m/s (p < 0.05). Patients using powered prostheses also had 26% greater frontal H range compared with nonamputees at 0.75 m/s (p < 0.05). CONCLUSIONS: People with a transtibial amputation may more effectively regulate H at two specific walking speeds when using powered compared with passive-elastic prostheses. CLINICAL RELEVANCE: Our results support the hypothesis that an ankle-foot prosthesis capable of providing net positive work during the stance phase of walking reduces sagittal plane H; future studies are needed to validate our biomechanical findings with larger numbers of patients and should determine whether powered prostheses can decrease the risk of falls in patients with a transtibial amputation.

Psoas force recruitment in full-body musculoskeletal movement simulations is restored with a geometrically informed cost function weighting.

Simulations of musculoskeletal models are useful for estimating internal muscle and joint forces. However, predicted forces rely on optimization and modeling formulations. Geometric detail is important to predict muscle forces, and greater geometric complexity is required for muscles that have broad attachments or span many joints, as in the torso. However, the extent to which optimized muscle force recruitment is sensitive to these geometry choices is unclear. We developed level, uphill and downhill sloped walking simulations using a standard (uniformly weighted, "fatigue-like") cost function with lower limb and full-body musculoskeletal models to evaluate hip muscle recruitment with different geometric representations of the psoas muscle under walking conditions with varying hip moment demands. We also tested a novel cost function formulation where muscle activations were weighted according to the modeled geometric detail in the full-body model. Total psoas force was less and iliacus, rectus femoris, and other hip flexors' force was greater when psoas was modeled with greater geometric detail compared to other hip muscles for all slopes. The proposed weighting scheme restored hip muscle force recruitment without sacrificing detailed psoas geometry. In addition, we found that lumbar, but not hip, joint contact forces were influenced by psoas force recruitment. Our results demonstrate that static optimization dependent simulations using models comprised of muscles with different amounts of geometric detail bias force recruitment toward muscles with less geometric detail. Muscle activation weighting that accounts for differences in geometric complexity across muscles corrects for this recruitment bias.

Age and initial position affect movement biomechanics in sit to walk transitions: Whole body balance and trunk control.

Maintaining dynamic balance during transitional movements like sit-to-walk (STW) can be challenging for older adults. Age-related neuromuscular decline can alter movement in STW, such as rising with greater trunk flexion, narrowing the feet, or using arms to push off. Initial foot and arm position can affect subsequent movement biomechanics, with different ground reaction forces (GRFs) that stabilize and advance the body center of mass (COM). The purpose of this study was to quantify whole-body biomechanics and trunk control of STW transitions. Fifteen younger adults (18-35 years) and fifteen older adults (50-79 years) performed STW from four initial foot positions and two arm positions. Three-dimensional (3D) GRFs, 3D body COM displacement, and integrated electromyography values from the lumbar paraspinals and gluteus medius were evaluated. Younger adults generated greater mediolateral GRF ranges while rising, whereas older adults generated greater mediolateral GRF ranges when stepping forward suggesting different strategies to laterally control the body COM. Initial foot position affected the STW movement, with narrow foot positions having smaller body COM displacement than wide foot positions, associated with smaller medial GRFs to move the body COM toward the stance limb. Rising with arm support required less lumbar paraspinal excitation, which was further reduced when with a posteriorly offset foot. Gluteus medius activity was greater for older adults compared to younger adults in STW. Completing STW with arm support can reduce the muscle activity required to stabilize the torso when rising, which likely has implications for balance control and low back loading.

Concentric and eccentric hip musculotendon work depends on backpack loads and walking slopes.

Hip muscle weakness is associated with low back and leg injuries. In addition, hiking with heavy loads is linked to high incidence of overuse injuries. Walking with heavy loads on slopes alters hip biomechanics compared to unloaded walking, but individual muscle mechanical work in these challenging conditions is unknown. Using movement simulations, we quantified hip muscle concentric and eccentric work during walking on 0° and ±10° slopes with, and without 40% bodyweight added loads, and with and without a hip belt. For gluteus maximus, psoas, iliacus, gluteus medius, and biceps femoris long head, both concentric and eccentric work were greatest during uphill walking. For rectus femoris and semimembranosus, concentric work was greatest during uphill and eccentric work was greatest during downhill walking. Loaded walking had greater concentric and eccentric work from rectus femoris, biceps femoris long head, and gluteus maximus. Psoas concentric work was greatest while carrying loads regardless of hip belt usage, but eccentric work was only greater than unloaded walking when using a hip belt. Loaded and uphill walking had high concentric work from gluteus maximus, and high eccentric work from gluteus medius and biceps femoris long head. Carrying heavy loads uphill may lead to excessive hip muscle fatigue and heightened injury risk. Effects of the greater eccentric work from hip flexors when wearing a hip belt on lumbar spine forces and pelvic stability should be investigated. Military and other occupational groups who carry heavy backpacks with hip belts should maintain eccentric strength of hip flexors and hamstrings.

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.

Age-specific biomechanical challenges and engagement in dynamic balance training with robotic or virtual real-time visual feedback.

Challenging balance training that targets age-related neuromuscular and motor coordination deficits is needed for effective fall prevention therapy. Goal-directed training can provide intrinsically motivating balance activities but may not equally challenge balance for all age groups. Therefore, the purpose of this research was to quantify age-specific effects of dynamic balance training with real-time visual feedback. Kinematics, muscle activity, and user perceptions were collected for forty healthy adults (20 younger, 18-39 years; 20 older, 58-74 years), who performed a single balance training session with or without real-time visual feedback. Feedback involved controlling either a physical mobile robot or screen-based virtual ball through a course with standing tilt motions from an instrumented wobble board. Dynamic balance training was more challenging for older compared to younger adults, as measured by significantly higher dorsiflexor and knee extensor muscle activity and ankle co-contractions (50%-80%, p<0.05). Older participants also performed more motion while training without feedback compared to younger adults (22%-65%, p<0.05). Robotic and virtual real-time visual feedback elicited similar biomechanical adaptations in older adults, reducing motions to similar levels as younger adults and increasing ankle co-contractions (p<0.05). Despite higher muscular demand, perceived physical exertion and high enjoyment levels (Intrinsic Motivation Inventory >0.80) were consistent across groups. However, robotic visual feedback may be more challenging than virtual feedback based on more frequent balance corrections, lower perceived competence, and lower game scores for older compared to younger adults. These findings collectively support the feedback system's potential to provide engaging and challenging at-home balance training across the lifespan.

Healthy aging reduces dynamic balance control as measured by the simplified Star Excursion Balance Test.

BACKGROUND: Detecting and classifying factors that contribute to age-related balance decline are essential for targeted interventions. Dynamic postural tests that challenge neuromuscular balance control are important to detect subtle deficits that affect functional balance in healthy aging. RESEARCH QUESTION: How does healthy aging affect specific components of dynamic postural control as measured by the simplified Star Excursion Balance Test (SEBT)? METHODS: Twenty healthy younger (18-39 years) and twenty healthy older (58-74 years) adults performed the standardized simplified SEBT, which involved standing on one leg and reaching the contralateral leg as far as possible in the anterior, posteromedial, and posterolateral directions. Optical motion capture was used to quantify the maximum reach distance normalized by body height (%H) for three repeated trials in each direction per leg. Linear mixed effects models and pairwise comparisons of estimated marginal means were used to assess differences (p < 0.05) in normalized maximum reach distance by age group, reach direction, and leg dominance. Intersubject and intrasubject variability were also assessed by age group using coefficients of variation (CV). RESULTS: Healthy older adults had less dynamic postural control compared to younger adults, with shorter reach distances in the anterior (7.9 %), posteromedial (15.8 %), and posterolateral (30.0 %) directions (p < 0.05). Leg dominance and sex did not significantly affect SEBT score for either age group (p > 0.05). Low intrasubject variability (CV<0.25 %) was found for repeated trials in both the older and younger participants. Therefore, the comparatively higher intersubject variability (Range CV=8-25 %) was mostly attributed to differences in SEBT performance across participants. SIGNIFICANCE: Quantifying dynamic postural control in healthy older adults in a clinical setting is important for early detection of balance decline and guiding targeted and effective treatment. These results support that the simplified SEBT is more challenging for healthy older adults, who may benefit from dynamic postural training to mitigate age-related decline.

Walking slope and heavy backpack loads affect torso muscle activity and kinematics.

The independent effects of sloped walking or carrying a heavy backpack on posture and torso muscle activations have been reported. While the combined effects of sloped walking and backpack loads are known to be physically demanding, how back and abdominal muscles adapt to walking on slopes with heavy load is unclear. This study quantified three-dimensional pelvis and torso kinematics and muscle activity from longissimus, iliocostalis, rectus abdominis, and external oblique during walking on 0° and ± 10° degree slopes with and without backpack loads using two different backpack configurations (hip-belt assisted and shoulder-borne). Iliocostalis activity was greater during downhill and uphill compared to level walking, but longissimus was only greater during uphill. Rectus abdominis activity was greater during downhill and uphill compared to level, while external oblique activity decreased as slopes progressed from down to up. Longissimus, but not iliocostalis, activity was reduced during both backpack configurations compared to walking with no pack. Hip-belt assisted load carriage required less rectus abdominis activity compared to using shoulder-borne only backpacks; however, external oblique was not influenced by backpack condition. Our results revealed different responses between iliocostalis and longissimus, and between rectus abdominis and external obliques, suggesting different motor control strategies between anatomical planes.

Automated optimization of residual reduction algorithm parameters in OpenSim.

The residual reduction algorithm (RRA) in OpenSim is designed to improve dynamic consistency of kinematics and ground reaction forces in movement simulations of musculoskeletal models. RRA requires the user to select numerous tracking weights for the joint kinematics to reduce residual errors. Selection is often performed manually, which can be time-consuming and is unlikely to yield optimal tracking weights. A multi-heuristic optimization algorithm was used to expedite tracking weight decision making to reduce residual errors. This method produced more rigorous results than manual iterations and although the total computation time was not significantly reduced, this method does not require the user to monitor the algorithm's progress to find a solution, thereby reducing manual tuning. Supporting documentation and code to implement this optimization is freely provided to assist the community with developing movement simulations.

Changes in dynamic balance control in adults with obesity across walking speeds.

Adults with obesity have gait instability, leading to increased fall risks and decreased physical activity. Whole-body angular momentum (WBAM) is regulated over a gait cycle, essential to avoid a fall. However, how obese adults regulate WBAM during walking is unknown. The current study investigated changes in WBAM about the body's center of mass (COM) during walking in obese and non-obese adults across different walking speeds. Twenty-eight young adults with obesity and normal weight walked barefoot at a fixed walking speed (FWS, 1.25 m/s) and at five different speeds based on their preferred walking speed (PWS): 50, 75, 100, 125, and 150 % of PWS. Adults with obesity walked slower with shorter step length, wider step width, and longer double support time (p < 0.01). The ranges of frontal- and transverse-plane WBAM were greater in obese adults (p < 0.01). We also found that the range of frontal-plane WBAM did not significantly change with walking speed (p > 0.05), while the range of transverse-plane WBAM increased with walking speed (p < 0.01). The ranges of frontal- and transverse-plane WBAM increased with the mediolateral ground reaction force and mediolateral moment arm (p < 0.01), which may be most affected by lateral foot placement relative to the body's COM. Our findings suggest that controlling mediolateral stability during walking is more challenging in obese adults, independent of their slow walking speed. Understanding whole-body rotational dynamics observed in obese walking provides an insight into the biomechanical link between obesity and gait instability, which may help find a way to reduce fall risks and increase physical activity.

Balance Therapy With Hands-Free Mobile Robotic Feedback for At-Home Training Across the Lifespan.

Providing aging adults with engaging, at-home balance therapy is essential to promote long-term adherence to unsupervised training and to foster independence. We developed a portable interactive balance training system that provides real-world visual cues on balance performance using wobble board tilt angles to control the speed of a robotic car platform in a three-dimensional environment. The goal of this study was to validate this mobile balance therapy system for home use across the lifespan. Twenty younger (18-39 years) and nineteen older (58-74 years) healthy adults performed balance training with and without visual feedback while standing on a wobble board instrumented with a consumer-grade inertial measurement unit (IMU) and optical motion tracking markers. Participants performed feedback trials based on either the robotic car's movements or a commercially-available virtual game. Wobble board tilt measurements were highly correlated between IMU and optical measurement systems ( [Formula: see text]), with high agreement in outcome metrics ( [Formula: see text]) and small bias ( [Formula: see text]). Both measurement systems identified similar aging, feedback, and stance type effects including (1) altered movement control when older adults performed tilting trials with either robotic or virtual feedback compared to without feedback, (2) two-fold greater wobble board oscillations in older vs. younger adults during steady standing, (3) no difference in board oscillations during steady standing in narrow vs. wide double support, and (4) greater wobble board oscillations for single compared to double support. These findings demonstrate the feasibility of implementing goal-directed robotic balance training with mobile tracking of balance performance in home environments.

The ins and outs of dynamic balance during 90-degree turns in people with a unilateral transtibial amputation.

The ability to maintain balance when turning is essential to functional and independent living. Due to the lack of neuromuscular ankle control on the prosthetic side in people with a transtibial amputation (TTA), turning is likely more challenging. The purpose of this study was to quantify how people with TTA maintain dynamic balance during 90-degree turns made with the prosthesis on the inside and outside of the turn compared to people without amputation. Eight participants with TTA and eight age-, height-, and sex- matched non-amputee controls performed left and right 90-degree step turns at a self-selected speed. The primary outcomes were range of whole-body angular momentum and positive and negative contributions of six segment groups (head/trunk, pelvis, arms, and legs) to whole-body angular momentum during the continuation stride. Participants with TTA had greater range of frontal- and sagittal-plane whole-body angular momentum when turning with the prosthesis on the inside compared controls. They also had a greater range of whole-body angular momentum in all planes of motion when turning with the prosthesis on the inside compared to outside of the turn. The contributions for the head/trunk and inside and outside legs differed between groups and turns, suggesting altered interactions between segment momenta to compensate for the reduced contribution of the amputated leg. This study provides insight into possible training paradigms to reduce the high incidence of turn related falls in people with TTA and, potentially, ways to alter prosthetic function to promote balance control.

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.

Compensation due to age-related decline in sit-to-stand and sit-to-walk.

Capacity is the physiological ability of the neuromusculoskeletal systems; this declines with age. This decline in capacity may result in the inability to stand up (sit-to-stand, sit-to-walk), which is an important movement for independent living. Compensation, as a result of functional redundancy, is key in understanding how much age-related decline can be tolerated before movement limitations arise. Yet, this topic has been underexposed in the biomechanics literature. The purpose of this systematic review was to approach the literature on sit-to-stand and sit-to-walk studies from the perspective of compensation and create an overview of our current understanding of compensation in standing up, identifying the limitations and providing future recommendations. A literature search was performed, using the keywords and their synonyms: strateg*(approach, technique, way)AND, sit-to-walk OR sit-to-stand OR rise (raise, arise, stand, stand-up) AND chair (seat). Inclusion criteria: full articles on biomechanics or motor control on sit-to-stand or sit-to-walk in healthy adults (<60y), healthy or frail elderly adults (>60y), and adults with osteoarthritis. The results show that the experimental set-ups and musculoskeletal models in STS and STW studies generally exclude compensation by using restricted protocols and simplifications. Moreover, factors are mostly analysed in isolation, excluding confounding causes within capacity and/or movement objectives which limits the generalization of the results. Future studies in the standing up task should consider to (1) determine the effect of varying arm push-off strategies, (2) focus on sit-to-walk, (3) determine the biomechanical implications of asymmetry, and (4)incorporate assessments of physical capacity as well as changes in psychological priorities.