The Effect of Alignment Changes on Unilateral Transtibial Amputee's Gait: A Systematic Review

A systematic review of methods used to assist transtibial prosthetic alignment decision-making

Prosthetic alignment is a highly subjective process that is still based on clinical judgments. Thus, researchers have aimed their effort to quantify prosthetic alignment by providing an objective method that can assist and guide prosthetists in achieving transtibial (TT) prosthetic alignment. This systematic review aimed to examine the current literature on TT prosthetic alignment to scope the qualitative and quantitative methods designed to guide prosthetists throughout the TT prosthetic alignment process as well as evaluate the reported instruments and devices that are used to align TT prostheses and their clinical feasibility. A literature search, completed in June 2022, was performed using the following databases: Web of Science (Clarivate), SCOPUS (Elsevier), and Pub Med (Medline) with searching terms focusing on TT, prosthesis, prosthetist, prosthetic alignment, and questionnaires, resulting in 2790 studies being screened. Twenty-four studies have used quantitative methodologies, where sensor technologies were found to be the most frequently proposed technology combined with gait analysis tools and/or subjective assessments. A qualitative method that assists prosthetists throughout the alignment process was not found. In this systematic review, we presented diverse methods for guiding and assisting clinical decision-making regarding TT prosthetic alignment. However, most of these methods considered varied parameters, and there is a need for elaboration toward standardized methods, which would improve the prosthetic alignment clinical outcome.

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.

A proper sequence of dynamic alignment in transtibial prosthesis: insight through socket reaction moments

Dynamic alignment in prosthetic fitting is important because it affects the user's stability, kinematics, and kinetics such as socket reaction moments. It is performed by tuning the spatial relationship between the transtibial prosthetic socket and the foot following sequential observational gait analysis in the three anatomical planes. However, the order of planes in which the adjustment should be performed is still unclear. To investigate the appropriate sequence of dynamic alignment adjustment, ten participants with transtibial amputation were asked to walk in different alignment conditions (flexion, extension, adduction, abduction; lateral, medial, anterior, and posterior translation of the socket, and plantarflexion, dorsiflexion, inversion, and eversion of the foot) to measure socket reaction moments in the out-of-planes (e.g., the effect of sagittal alignment on the coronal moment). A significant difference was found only among socket posterior translation, socket flexion, and baseline alignment in the coronal moment (P = 0.02). The results of the current and previous studies suggest that moments in the coronal plane are affected by alignment changes in all three planes, whereas moments in the sagittal plane are affected only by sagittal alignment changes. It is suggested that the procedure of alignment adjustments should be finalized in the coronal plane.

Angulation vs translation of transtibial prosthetic socket: their difference analyzed by socket reaction moments

BACKGROUND

Previous studies investigated the effects of alignment changes in transtibial prostheses on socket reaction moments. However, the effects of angular and translational alignment changes with equal displacement between the foot and the socket were not directly compared.

RESEARCH QUESTIONS

What are the different effects of angular and translational alignment changes in transtibial prostheses?

METHODS

Ten individuals with transtibial prostheses participated in the measurement of temporo-spatial parameters, socket reaction moments, and their timings under nine alignment conditions (3° flexion/extension, anterior/posterior translation, 6° adduction/abduction, medial/lateral translation, and baseline). The displacement of the prosthetic feet was set to be equal between the angular and translational changes.

RESULTS

No significant changes in walking speed were found. Similar effects were observed in the magnitudes, but not in timing, of the moments under angular and translational changes in the sagittal plane (p < 0.01 for the differences in peak extension moment among anterior translation, baseline, and extension conditions, and in peak flexion moment among anterior translation, baseline, and extension conditions). In the coronal plane, similar effects were found in the magnitudes of the moments in the early stance (p < 0.01 at 5 %, 20 %, and 75 % stance). A significant difference in magnitude was observed in the late stance (p < 0.01 between adduction and medial translation conditions).

SIGNIFICANCE

The timing of the socket reaction moment may be different in the sagittal plane, while the magnitudes of the socket reaction moment in the late stance may be different in the coronal plane between the angular and translational alignment changes.

Emulating the Effective Ankle Stiffness of Commercial Prosthetic Feet Using a Robotic Prosthetic Foot Emulator

Prosthetic foot selection for individuals with lower limb amputation relies primarily on clinician judgment. The prosthesis user rarely has an opportunity to provide experiential input into the decision by trying different feet. A prosthetic foot emulator (PFE) is a robotic prosthetic foot that could facilitate prosthesis users' ability to trial feet with different mechanical characteristics. Here, we introduce a procedure by which a robotic PFE is configured to emulate the sagittal plane effective ankle stiffness of a range of commercial prosthetic forefeet. Mechanical testing was used to collect data on five types of commercial prosthetic feet across a range of foot sizes and intended user body weights. Emulated forefoot profiles were parameterized using Bezier curve fitting on ankle torque-angle data. Mechanical testing was repeated with the PFE, across a subset of emulated foot conditions, to assess the accuracy of the emulation. Linear mixed-effects regression and Bland-Altman Limits of Agreement analyses were used to compare emulated and commercial ankle torque-angle data. Effective ankle stiffness of the emulated feet was significantly associated with the corresponding commercial prosthetic feet (p<.001). On average, the emulated forefeet reproduced the effective ankle stiffness of corresponding commercial feet within 1%. Furthermore, differences were independent of prosthetic foot type, foot size, or user body weight. These findings suggest a PFE could be an effective tool for emulating commercial prosthetic feet, enabling prosthesis users to quickly trial different feet and provide experiential input as part of a prosthetic foot prescription.

The effects of small variations in shoe heel height on gait in people with a transtibial amputation

BACKGROUND

Shoe heel height is considered to influence prosthetic alignment, walking comfort, and gait symmetry in people with a transtibial amputation (TTA). However, research on the effect of heel height is scarce, and no evidence is available on the effects of variations smaller than 20 mm. These small heel height variations between store-bought shoes are often overlooked by people with an amputation and may cause secondary musculoskeletal problems in the long term.

OBJECTIVE

To examine the effects of small increases in heel height on gait symmetry in people with a TTA and healthy individuals.

STUDY DESIGN

Experimental repeated measures study.

METHODS

Fourteen participants with a TTA and 15 healthy controls were included. Pressure data, spatiotemporal data, and experienced walking comfort were measured during walking with four heel height conditions: original height and increased heights of 3, 5, and 8 mm. Symmetry in center of pressure velocity (VCOP), gait parameters, and experienced walking comfort were compared between the heel heights and between healthy controls and prosthetic walkers.

RESULTS

Increased heel height resulted in a significant decrease in VCOP symmetry (P = 0.001) and experienced walking comfort (P < 0.001). The VCOP trajectory of the prosthetic leg mainly differed within the first 14.5% of the stance phase. Healthy individuals showed better VCOP symmetry in all conditions (P < 0.001).

CONCLUSIONS

Healthcare professionals should advice their clients to be alert of small heel height differences between store-bought shoes, especially those larger than 5 mm. A prosthetic alignment adjustment should be considered when purchasing new shoes.

Design of lower limb prosthetic sockets: a review

INTRODUCTION

The prosthetic socket is the connecting part between the stump and the prosthesis, which is the important basis for the function of the prosthesis. The current prosthetic socket is difficult in meeting the needs of amputees current, which is the main reason for amputees abandoning their prostheses. This paper reviews the design and use of prosthetic sockets for lower limb.

AREAS COVERED

The contribution of this publication is to review the skin problem, interface stress and volume fluctuations for prosthetic sockets, which are proposed as the key factors affecting the use of prosthetic sockets. Moreover, the lower limb prosthetic sockets are classified into the full-contact and the frame-type sockets according to the different contact type between stump and prosthetic socket, and their advantages and disadvantages are analyzed from different perspectives.

EXPERT OPINION

Aim to design the prosthetic socket with function transfer, suspension stability and comfort of socket, a design concept for prosthetic socket with self-adapt in real-time is proposed. It can be achieved by the smart materials with special mechanical properties.

Effect of Lower Limb Muscle Fatigue on Fall Risk for Transfemoral Amputee: A Pilot Study

Muscle fatigue is a decline in muscle maximum force during contraction and can influence the fall risk among people. This study is aimed at identifying the effect of fatigue on prospective fall risk in transfemoral amputees (TFA). Fourteen subjects were involved in this study with TFA (34.7 ± 8.1 yrs, n = 7) and normal subjects (31.1 ± 7.4 yrs, n = 7). Fatigue of lower limb muscles was induced with the fatigue protocol. Subjects were tested prefatigue and postfatigue using the standardized fall risk assessment. All results were calculated and compared between pre- and postfatigue to identify fatigue's effect on both groups of subjects. The results showed that the fall risk increased significantly during pre- and postfatigue for TFA (p = 0.018), while there were no significant differences in normal subjects (p = 0.149). Meanwhile, the fall risk between TFA and normal subjects for prefatigue (p = 0.082) and postfatigue (p = 0.084) also showed no significant differences. The percentage (%) of increased fall risk for TFA was 19.2% compared to normal subjects only 16.7%. However, 61.4% increased of % fall risk in TFA after fatigue by using the baseline of the normal subject as the normalized % of fall risk. The increasing fall risks for TFA after fatigue are three times higher than the potential fall risk in normal subjects. The result indicates that they need to perform more precautions while prolonging lower limb activities. These results showed the implications of fatigue that can increase the fall risk due to muscle fatigue from repetitive and prolonged activities. Therefore, rehabilitation programs can be done very safely and precisely so that therapists can pursue fitness without aggravating existing injuries.

Influence of coronal and sagittal prosthetic foot alignment on socket reaction moments in transtibial prostheses during walking

BACKGROUND

The socket reaction moment (SRM) has been reported to change because of alignment changes in transtibial prosthetic sockets. However, the influence of prosthetic foot alignment on SRM remains unclear.

RESEARCH QUESTION

Are SRMs predictable from alignment changes of prosthetic feet?

METHODS

Ten users of transtibial prostheses participated in this study. Under five alignment conditions (3 ° plantarflexion and dorsiflexion, 6 ° inversion and eversion, and baseline alignment), temporal-spatial parameters and sagittal and coronal SRMs were measured during walking. Cadence, walking speed, step time, single support time, and step length were compared. The maximum/minimum SRM, % stance (timing) of the maximum/minimum SRM, Zero-cross, and SRMs at 5 %, 20 %, and 75 % stance were extracted and compared. Repeated measures analysis of variance or Friedman tests, and linear regression analyses were conducted for statistical analyses (i.e., alignment conditions as independent variables and SRM parameters as dependent variables).

RESULTS

The SRMs at 5%, 20 %, and 75 % stance showed significant differences under coronal angular changes. The minimum SRM, % stance of the minimum/maximum SRM, and Zero-cross showed significant differences under sagittal alignment changes. In linear regression analysis, the minimum SRM, % stance of the minimum/maximum SRM, SRM at 20 % stance, and Zero-cross were significant dependent variables in the sagittal plane. The maximum/minimum SRM, SRM at 20 % and 75 % stance, and % stance of the minimum SRM were significant dependent variables in the coronal plane.

SIGNIFICANCE

The results indicated that the changes in prosthetic feet angles may predict the magnitude of SRM (maximum/minimum SRM, SRM at 20 % and 75 % stance) in the coronal plane, and the timing of SRM (Zero-cross, % stance of the maximum/minimum SRM) in the sagittal plane. These findings suggest that the SRM may be useful for evaluating foot alignment in transtibial prostheses.

A Biomimetic Adapter for Passive Self-alignment of Prosthetic Feet

INTRODUCTION

Dynamic alignment of lower limb prostheses is subjective and time-consuming. Compensatory gait strategies caused by prosthesis misalignment can negatively affect lower limb amputees who cannot access a certified prosthetist for alignment adjustments. The objective of this study is to evaluate a novel six-degrees-of-freedom passive transtibial prosthetic adapter that self-aligns during various phases of gait. This self-aligning adapter may benefit service members and veterans stationed or living far from a clinical facility.

METHODS

Four transtibial amputee subjects, aged 47 to 62 (mean: 55.75) years with mean weight of 163.6 lbs and mean K-level of 3.25, walked at self-selected speeds on a 10-m level walkway. Subjects walked with the self-aligning and a size- or weight-matched control adapter, assembled to a commercially available energy-storing-and-returning foot and their own socket, with 22-mm alignment perturbations in the anterior, posterior, medial, or lateral directions. Subjects were blinded to both adapter type and misalignment. Socket moments, spatiotemporal gait parameters, and subjective socket comfort were recorded.

RESULTS

Preliminary results showed improvements in mean peak socket moments and step length differential with the self-aligning adapter across all alignments. Walking speed and prosthesis-side base of support showed little change in all configurations. Prosthesis-side stance duration and Functional Ambulation Profile Score increased with the self-aligning adapter in some alignments. Patient-reported socket comfort increased slightly with the self-aligning adapter across all misalignments.

CONCLUSION

Subjects maintained similar walking speeds and experienced greater gait symmetry and reduced sagittal plane peak moments with the self-aligning adapter when exposed to misalignments. These trends suggest a benefit to transtibial amputees from a reduction in secondary gait effects from prosthesis misalignments. Additionally, a wider range of acceptable prosthesis alignments may be possible with the self-aligning adapter. Subsequent trials are underway to evaluate the self-aligning adapter in real-world environments like walking on uneven terrains, stairs, ramps, and abrupt turns.

Patient-Preferred Prosthetic Ankle-Foot Alignment for Ramps and Level-Ground Walking

Patient preference of lower limb prosthesis behavior informally guides clinical decision making, and may become increasingly important for tuning new robotic prostheses. However, the processes for quantifying preference are still being developed, and the strengths and weaknesses of preference are not adequately understood. The present study sought to characterize the reliability (consistency) of patient preference of alignment during level-ground walking, and determine the patient-preferred ankle angle for ascent and descent of a 10° ramp, with implications for the design and control of robotic prostheses. Seven subjects with transtibial amputation walked over level ground, and ascended and descended a 10° ramp on a semi-active prosthetic ankle capable of unweighted repositioning in dorsiflexion and plantarflexion. Preferred ankle angle was measured with an adaptive forced-choice psychophysics paradigm, in which subjects walked on a randomized static ankle angle and reported whether they would prefer the ankle to be dorsiflexed or plantarflexed. Subjects had reliable preferences for alignment during level-ground walking, with deviations of 1.5° from preference resulting in an 84% response rate preferring changes toward the preference. Relative to level walking, subjects preferred 7.8° (SD: 4.8°) of dorsiflexion during ramp ascent, and 5.3° (SD: 3.8°) plantarflexion during ramp descent. As the ankle angle better matched the ramp angle, socket pressures and tibial progression (shank pitch) both more closely mirrored those during level walking. These findings provide baseline behaviors for prosthetic ankles capable of adapting to slopes based on patient preference, and provide strong evidence that people with transtibial amputation can finely perceive ankle alignment.

Movement asymmetry during low and high demand mobility tasks after dysvascular transtibial amputation

BACKGROUND

Movement asymmetries between lower limbs are commonly exhibited by adults after transtibial amputation. However, the degree of movement asymmetry between low- and high-demand functional tasks remains unknown.

METHODS

Kinematic and kinetic data were collected during overground walking (low-demand) and step ascent (high-demand) tasks for two groups: 1) persons with transtibial amputation and 2) healthy matched peers. Analysis of covariance was used to compare sagittal-plane peak knee moment and joint angle (primary) and hip and ankle moments and joint angles, vertical ground reaction force and impulse (secondary).

FINDINGS

Within transtibial amputation group comparisons showed significantly greater between-limb asymmetry in peak knee moment (p < .01), vertical impulse (p < .01), peak vertical ground reaction force (p = .05), peak ankle angle (p < .01) and peak ankle moment (p < .01) with the step ascent task compared to overground walking. The transtibial amputation group had greater between-limb asymmetry during step ascent in peak knee moment (p < .01), vertical impulse (p < .01), peak vertical ground reaction force (p = .04) and peak ankle angle (p < .01) than healthy matched peers. During overground walking, the transtibial amputation group had greater between-limb asymmetry in peak vertical impulse (p = .05) and peak ankle moment (p < .01) than healthy matched peers.

INTERPRETATION

Movement asymmetry is increased during step ascent compared to overground walking for adults with transtibial amputation. While the restoration of overground walking is the focus of post-amputation rehabilitation and prosthetic design, higher demand tasks should also be considered to maximize mobility for adults with transtibial amputation.

The effect of prosthetic alignment on hip and knee joint kinetics in individuals with transfemoral amputation

BACKGROUND

Prosthetic alignment directly affects the biomechanical loading in individuals with lower-limb amputation, and improper alignment may be contribute to the high incidence of hip and knee osteoarthritis (OA). The biomechanical changes caused by different alignments should be considered in prosthetic fitting. However, the quantitative effect of alignment on the kinetic features of individuals with transfemoral amputation remains unclear.

RESEARCH QUESTION

As important kinetics indexes, how are the hip and knee joint moments affected by prosthetic alignment in individuals with transfemoral amputation?

METHODS

Gait tests of ten individuals with transfemoral amputation and fifteen individuals without amputation (control group) were performed. Several prosthetic alignment conditions were used, including the so-called "initial" alignment and eight malalignments. The hip and knee joint moments of the individuals with amputation under various alignments were analysed and compared with those of the control group. Statistical analyses were performed by one-way ANOVA, repeated measure multivariate ANOVA, and paired t tests.

RESULTS

The peaks and impulses of the hip abductor and external rotator moments on the residual side were significantly smaller than those of the control group (P < 0.0056). The peaks of the hip extensor, adductor and external rotator moments on the intact side were significantly larger than those on the residual side (P < 0.05). Alignment significantly affected the intact hip and knee joint moments for each individual with amputation (P < 0.00625), but there was no consistent effect among individuals.

SIGNIFICANCE

The significantly larger hip joint moment on the intact side of individuals with transfemoral amputation may be associated with the higher incidence of hip OA on the intact side. Alignment significantly affects the hip and knee joint moments of each individual with transfemoral amputation, but the individual responses to alignment changes are different. This situation may imply that the method for optimizing alignment should be personalized.

Modeling and Design of the Automatic Stance Phase Lock (ASPL) Knee Joint Control Mechanism for Paediatric Users With Transfemoral Amputations

The 2-axes Automatic Stance Phase Lock (ASPL) stance control mechanism has been demonstrated to improve adult amputees' mobility but has yet to be developed for the paediatric population. The overall objective for this work was to characterize the ASPL control mechanism with biomechanical modelling and design a 2-axes ASPL prosthetic knee joint suitable for children between the ages of 6 and 12 years. Paediatric anthropometric data and ASPL control mechanism performance characteristics established from adult ASPL knee users were utilized to develop paediatric-appropriate configurations of the ASPL stance control mechanism. Additional predefined design criteria were also included in the detailed knee design. Developed prototypes of the knee joint, Children-ASPL (CASPL) knee, were clinically validated using a single-subject cross-over study design, to assess control mechanism and overall knee functions. Faster walking speed, longer step and stride length with the CASPL knee suggest potential improvements in overall walking performance. The participant also felt confident walking with the CASPL knee and perceived the locking mechanism to be stable. Stemming from the findings here, future design revisions are aimed to improve the performance of the current prototype, including reliability of knee lock disengagement and performance of the swing phase control mechanism.

The effect of coronal prosthetic alignment changes on socket reaction moments, spatiotemporal parameters, and perception of alignment during gait in individuals with transtibial amputation

Introduction

The alignment of a prosthesis is clinically determined based on observations by clinicians and the subjective perception of amputees during gait. However, this process has been reported to be unreliable. Socket reaction moment has been reported to be significantly impacted by alignment changes, but the impact of these alignment changes on other gait parameters is unclear. The aim of this study was to investigate the effects of coronal alignment changes of a transtibial prosthesis on socket reaction moment, spatiotemporal parameters, and perceptions of alignment during gait in amputees.

Methods

Nine individuals with transtibial amputation participated in this study. Socket reaction moment and spatiotemporal parameters (step time, step length, step width, single limb support time, cadence, and gait speed) were measured under nine coronal alignment conditions (angulation: ±3°, ±6°, translation: ±5 mm, ±10 mm, and baseline) using a three-dimensional motion capture system (Vicon) and an embedded load-cell system (Europa™). In addition, subjective perceptions of alignment were examined.

Results

Coronal alignment changes of the transtibial prostheses demonstrated significant changes in socket reaction moment; however, no significant changes were found with spatiotemporal parameters or the amputee’s perception.

Conclusion

Measurement of socket reaction moment, along with the embedded load-cell system, may be a better metric for tuning the coronal alignment of transtibial prostheses compared to spatiotemporal parameters and amputee’s perceptions.

Effect of prosthetic alignment on gait and biomechanical loading in individuals with transfemoral amputation: A preliminary study

BACKGROUND

Inappropriate biomechanical loading usually leads to a high incidence of hip and knee osteoarthritis (OA) in individuals with lower-limb amputation, and prosthetic alignment may be an important influencing factor. The effect of alignment on the lower limb loading remains quantitatively unclear, and the relationship between malalignment and joint diseases is undefined.

RESEARCH QUESTION

How does alignment affect spatiotemporal gait parameters and ground reaction force (GRF) in individuals with transfemoral amputation?

METHODS

Gait tests of 10 individuals with transfemoral amputation were performed with recommended alignment and eight malalignments, including 10 mm socket translation (anterior, posterior, medial, and lateral) and 6° socket angular changes (flexion, extension, abduction, and adduction). Fifteen individuals without amputation were recruited as a control group. The differences in spatiotemporal and GRF parameters under different alignments were analyzed and compared with those of the control group. Statistical analyses were performed by one-way ANOVA, repeated measure multivariate ANOVA, and paired t tests.

RESULTS

The medial GRF peaks and impulse on both sides and load rate on the intact side are significantly higher than those of the control group (P < 0.0056). The propulsive and braking peaks, vertical impulse, and medial and vertical load rates of GRF on the intact side are higher than those on the residual side (P < 0.05). The alignment of socket adduction significantly increases medial GRF peak and impulse on both sides (P < 0.0056).

SIGNIFICANCE

Alignments exert remarkable and complicated effects on the biomechanical performance. The considerably higher GRF on the intact side of the individuals with transfemoral amputation may lead to internal stress changes of the intact joint, which may be an inducement for high incidence of joint diseases. Probably due to the increased lateral deviation of the center of gravity, the socket adduction alignment significantly increases medial GRF, which may lead to an increased risk of knee OA.

Dynamic alignment using external socket reaction moments in trans-tibial amputees

BACKGROUND

Prosthetic alignment is used to optimize prosthetic functioning and comfort. Spatio-temporal and kinematic gait parameters are generally observed to guide this process. However, they have been shown to be influenced by compensations, which reduces their sensitivity to changes in alignment. Alternatively, the use of moments working at the base of the prosthetic socket, external socket reaction moments (ESRM), has been proposed to quantify prosthetic alignment.

RESEARCH QUESTION

To investigate if a predetermined kinetic alignment criterion, 0Nm averaged over the stance phase, can be used to fine-tune prosthetic alignment.

METHODS

10 transtibial amputees were included in this intervention study. Firstly, their prostheses were aligned using conventional alignment procedures. Kinetic parameters and Socket Comfort Score (SCS) were measured in this initial alignment (IA) condition. Subsequently, the coronal plane ESRM during gait was presented to the prosthetist in real time using a Gait Real-time Analysis Interactive Lab. The prosthetist iteratively adapted the prosthetic alignment towards a predetermined average ESRM during the stance phase of 0 Nm. At the Final Alignment (FA), kinetic parameters and SCS were measured again and a paired sample t-test was performed to compare ESRMs and SCSs between alignments.

RESULTS

A significant (p < 0.001) change was found in the absolute coronal plane ESRM (mean ± SD) from IA (|0.104| ± 0.058 Nm/kg) to FA (|0.012| ± 0.015 Nm/kg). In addition a significant (p < 0.001) change of the external coronal adduction knee moments was observed from IA (-0,127 ± 0.079 Nm/kg) to FA (-0.055 ± 0.089 Nm/kg), however this change was more variable among participants. On average, no significant (p = 0.37) change in the SCS was observed.

SIGNIFICANCE

While this study shows the potential of quantifying and guiding alignment with the assistance of kinetic criteria, it also suggests that a sole reliance on the ESRM as a single alignment criterion might be too simple.

The effect of transverse prosthetic alignment changes on socket reaction moments during gait in individuals with transtibial amputation

BACKGROUND

Alignment affects gait of individuals with transtibial prostheses. Sagittal and coronal alignment changes of the transtibial prostheses were demonstrated to affect socket reaction moments. However, the effects of transverse alignment changes on the socket reaction moments are not known.

RESEARCH QUESTION

The aim of this study was to investigate the effects of transverse alignment changes on the socket reaction moments and temporal-spatial parameters of gait in transtibial prostheses.

METHODS

The effects of transverse prosthetic alignment changes (i.e. 10° and 5° of internal and external rotations: toe-in and toe-out of the foot relative to the socket from a baseline alignment) on the sagittal and coronal socket reaction moments and temporal-spatial parameters (gait speed, cadence and step width) while walking in 9 individuals with transtibial amputation were investigated using an instrumented prosthetic pyramid adaptor and a three-dimentional (3D) motion capture system.

RESULTS

The transverse alignment changes demonstrated significant effects on the socket reaction moments in the coronal plane at 5% (P =  0.04), 20% (P =  0.04) and 75% (P =  0.0001) of stance phase. No significant effects were found in the socket reaction moments in the sagittal plane and the temporal-spatial parameters. The internal and external rotations of the prosthetic feet may have opposite effect in early and mid- to late-stance potentially due to changes in the spatial position of the heel (rearfoot) and toe (forefoot) of the prosthetic foot relative to the socket.

SIGNIFICANCE

Transverse alignment of the transtibial prostheses should be tuned not only considering the symmetry in toe-out angles of the feet, but also considering the potential effects of transverse alignment changes that may affect the coronal socket reaction moments.

A systematic review of variables used to assess clinically acceptable alignment of unilateral transtibial amputees in the literature

Prosthetic alignment is a subjective concept which lacks reliability. The outcome responsiveness to prosthetic alignment quality could help to improve subjective and instrument assisted prosthetic alignment. This study was aimed to review variables used to assess clinically acceptable alignment in the literature. The search was done in some databases including: Google Scholar, PubMed, EBSCO, EMBASE, ISI Web of Knowledge and Scopus. The first selection criterion was based on abstracts and titles to address the research questions of interest. The American Academy of Orthotics and Prosthetics checklists were used for paper risk of bias assessment. A total of 25 studies were included in this study. Twenty-four studies revealed the critics of standing position or walking to locate clinically acceptable alignment, only one study measured outcomes in both situations. A total of 253 adults with transtibial amputations and mean age of 48.71 years participated in included studies. The confidence level of included studies was low to moderate, and before-after trial was the most common study design (n = 19). The joint angle, load line location with respect to joints and center of pressure-related parameters were reported as sensitive outcomes to prosthetic alignment quality in standing posture. The amount of forces at various parts of gait cycle and time of events were sensitive to prosthetic alignment quality during walking. Standing balance and posture and temporal parameters of walking could help to locate clinically acceptable alignment.

Maintenance of muscle strength retains a normal metabolic cost in simulated walking after transtibial limb loss

Recent studies on relatively young and fit individuals with limb loss suggest that maintaining muscle strength after limb loss may mitigate the high metabolic cost of walking typically seen in the larger general limb loss population. However, these data are cross-sectional and the muscle strength prior to limb loss is unknown, and it is therefore difficult to draw causal inferences on changes in strength and gait energetics. Here we used musculoskeletal modeling and optimal control simulations to perform a longitudinal study (25 virtual “subjects”) of the metabolic cost of walking pre- and post-limb loss (unilateral transtibial). Simulations of walking were first performed pre-limb loss on a model with two intact biological legs, then post-limb loss on a model with a unilateral transtibial prosthesis, with a cost function that minimized the weighted sum of gait deviations plus metabolic cost. Metabolic costs were compared pre- vs. post-limb loss, with systematic modifications to the muscle strength and prosthesis type (passive, powered) in the post-limb loss model. The metabolic cost prior to limb loss was 3.44±0.13 J/m/kg. After limb loss, with a passive prosthesis the metabolic cost did not increase above the pre-limb loss cost if pre-limb loss muscle strength was maintained (mean -0.6%, p = 0.17, d = 0.17). With 10% strength loss the metabolic cost with the passive prosthesis increased (mean +5.9%, p < 0.001, d = 1.61). With a powered prosthesis, the metabolic cost was at or below the pre-limb loss cost for all subjects with strength losses of 10% and 20%, but increased for all subjects with strength loss of 30% (mean +5.9%, p < 0.001, d = 1.59). The results suggest that maintaining muscle strength may prevent an increase in the metabolic cost of walking following unilateral transtibial limb loss, and that a gait with minimal deviations can be achieved when muscle strength is sufficiently high, even when using a passive prosthesis.