Understanding lower limb muscle volume adaptations to amputation

A Review of Natural Fiber-Reinforced Composites for Lower-Limb Prosthetic Designs

This paper presents a comprehensive review of natural fiber-reinforced composites (NFRCs) for lower-limb prosthetic designs. It covers the characteristics, types, and properties of natural fiber-reinforced composites as well as their advantages and drawbacks in prosthetic designs. This review also discusses successful prosthetic designs that incorporate NFRCs and the factors that make them effective. Additionally, this study explores the use of computational biomechanical models to evaluate the effectiveness of prosthetic devices and the key factors that are considered. Overall, this document provides a valuable resource for anyone interested in using NFRCs for lower-limb prosthetic designs.

Successful Powerlifting in a Unilateral, Transtibial Amputee: A Descriptive Case Series

ABSTRACT

Beausejour, JP, Guinto, G, Artrip, C, Corvalan, A, Mesa, MF, Lebron, MA, and Stock, MS. Successful powerlifting in a unilateral, transtibial amputee: A descriptive case series. J Strength Cond Res 38(5): e243-e252, 2024-There are no reports in the literature of powerlifting success after amputation. We had the unique opportunity to characterize functional outcomes, strength, muscle contractility and size, and corticospinal excitability in an accomplished, competitive powerlifter (best competition squat = 205.0 kg, deadlift = 262.7 kg) with a unilateral, transtibial amputation relative to amputee controls. Four men (age range = 23-49 years) with unilateral, lower-limb amputation (3 transtibial, 1 transfemoral) participated in 1 laboratory visit. We assessed 10-m gait speed, the timed up and go (TUG) test, 5-time sit-to-stand performance (5TSTS), contractile properties of the vastus lateralis (VL) and medial gastrocnemius by tensiomyography, and VL cross-sectional area (CSA) by ultrasonography. Unilateral assessments for the intact limb included isokinetic knee extension and flexion torque and power and transcranial magnetic stimulation derived corticospinal excitability. An interview with the powerlifter provided contextual perspective. Compared with the control subjects, the powerlifter performed the 5TSTS faster (6.8%), exhibited faster VL contraction times (intact limb = 12.2%; residual limb = 23.9%), and showed larger VL CSA for the intact limb (46.7%). The powerlifter exhibited greater knee extension and flexion peak torque and mean power, particularly at 180°·s -1 , as well as greater corticospinal excitability for the intact VL (65.6%) and tibialis anterior (79.6%). By contrast, the control subjects were faster in the TUG (18.3%) and comfortable (13.0%) and fast (21.4%) in the 10-m walk test. The major themes of our interview included needing to modify lifting mechanics, persistence, and remarkable pain tolerance. Our findings highlight the impressive neuromuscular adaptations that are attainable after lower-limb amputation.

The Amputated Limb Gluteus Medius is Biomechanically Disadvantaged in Patients with Unilateral Transfemoral Amputation

Patients with transfemoral amputation (TFA) are at an increased risk of secondary musculoskeleteal comorbidities, primarily due to asymmetric joint loading. Amputated limb muscle weakness is also prevalent in the TFA population, yet all factors that contribute to muscle strength and thus joint loading are not well understood. Our objective was to bilaterally compare gluteus medius (GMED) muscle factors (volume, fatty infiltration, moment arm) that all contribute to joint loading in patients with TFA. Quantitative magnetic resonance (MR) images of the hip were collected from eight participants with unilateral TFA (2M/6F; age: 47.3 ± 14.7 y/o; BMI: 25.4 ± 5.3 kg/m2; time since amputation: 20.6 ± 15.0 years) and used to calculate normalized GMED muscle volume and fatty infiltration. Six participants participated in an instrumented gait analysis session that collected whole-body kinematics during overground walking. Subject-specific musculoskeletal models were used to calculate bilateral GMED (anterior, middle, posterior) moment arms and frontal plane hip joint angles across three gait cycles. Differences in volume, fatty infiltration, hip adduction-abduction angle, and peak moment arms were compared between limbs using paired Cohen's d effect sizes. Volume was smaller by 36.3 ± 18.8% (d = 1.7) and fatty infiltration was greater by 6.4 ± 7.8% (d = 0.8) in the amputated limb GMED compared to the intact limb. The amputated limb GMED abduction moment arms were smaller compared to the intact limb for both overground walking (anterior: d = 0.9; middle: d = 0.1.2) and during normal range of motion (anterior: d = 0.8; middle: d = 0.8) while bilateral hip adduction-abduction angles were similar during overground walking (d = 0.5). These results indicate that in patients with TFA, the amputated limb GMED is biomechanically disadvantaged compared to the intact limb, which may contribute to the etiology of secondary comorbidities. This population might benefit from movement retraining to lengthen the amputated limb GMED abduction moment arm during gait.

Hip joint and muscle loading for persons with bilateral transfemoral/through-knee amputations: biomechanical differences between full-length articulated and foreshortened non-articulated prostheses

BACKGROUND

Currently, there is little available in-depth analysis of the biomechanical effect of different prostheses on the musculoskeletal system function and residual limb internal loading for persons with bilateral transfemoral/through-knee amputations (BTF). Commercially available prostheses for BTF include full-length articulated prostheses (microprocessor-controlled prosthetic knees with dynamic response prosthetic feet) and foreshortened non-articulated stubby prostheses. This study aims to assess and compare the BTF musculoskeletal function and loading during gait with these two types of prostheses.

METHODS

Gait data were collected from four male traumatic military BTF and four able-bodied (AB) matched controls using a 10-camera motion capture system with two force plates. BTF completed level-ground walking trials with full-length articulated and foreshortened non-articulated stubby prostheses. Inverse kinematics, inverse dynamics and musculoskeletal modelling simulations were conducted.

RESULTS

Full-length articulated prostheses introduced larger stride length (by 0.5 m) and walking speed (by 0.3 m/s) than stubbies. BTF with articulated prostheses showed larger peak hip extension angles (by 10.1°), flexion moment (by 1.0 Nm/kg) and second peak hip contact force (by 3.8 bodyweight) than stubbies. There was no difference in the hip joint loading profile between BTF with stubbies and AB for one gait cycle. Full-length articulated prostheses introduced higher hip flexor muscle force impulse than stubbies.

CONCLUSIONS

Compared to stubbies, BTF with full-length articulated prostheses can achieve similar activity levels to persons without limb loss, but this may introduce detrimental muscle and hip joint loading, which may lead to reduced muscular endurance and joint degeneration. This study provides beneficial guidance in making informed decisions for prosthesis choice.

Assessment of isokinetic hip muscle strength and predictors in patients with lower limb amputation: A cross-sectional study

Objectives

The purpose of the study was to determine isokinetic features and analyze significant predictors related to activity level of patients with lower limb amputation.

Patients and methods

Forty-three male patients (mean age: 32.9±8.8 years; range, 21 to 50 years) with lower limb amputation were recruited consecutively for this cross-sectional study between March 1, 2022, and June 30, 2022. The hip flexor and extensor peak torques and total work were evaluated by an isokinetic dynamometer. The secondary outcome measure was the Amputee Mobility Predictor. A linear regression analysis was used to determine factors independently affecting Amputee Mobility Predictor scores.

Results

All data of patients with unilateral amputation, except for flexor (p=0.285) and extensor (p=0.247) peak torques on the dominant side, were higher than those of patients with amputation. Dominant side extensor peak torque was statistically higher than nondominant side extensor peak torque (59.4±30.7 vs. 43.4±32.0) in patients with bilateral amputation. No difference was detected between amputated and intact sides of patients with unilateral amputation. Both flexor and extensor total work on the amputated side of the patients with below-knee amputation were higher than the patients with above-knee amputations (63.5±21.1 vs. 94.1±34.3 and 67.1±34.0 vs. 113.0±51.5, respectively). Unilateral amputation (odds ratio: 7.442) and nondominant side extensor total work (odds ratio: 0.615) were found to be significant predictors related with amputee mobility predictor scale.

Conclusion

It is possible to have an idea about the possible activity level of the patients with lower limb amputation with the help of the predictors obtained in the current study.

Unilateral transfemoral osseointegrated prostheses improve joint loading during walking

People with unilateral transfemoral amputation using socket prostheses are at increased risk for developing osteoarthritis in both the residual hip and intact lower-limb joints. Osseointegrated prostheses are a surgical alternative to socket prostheses that directly attach to the residual femur via a bone-anchored implant, however their multi-joint loading effect is largely unknown. Our objective was to establish how osseointegrated prostheses influence joint loading during walking. Motion capture data (kinematics, ground reaction forces) were collected from 12 participants at baseline, with socket prostheses, and 12-months after prosthesis osseointegration during overground walking at self-selected speeds. Subject-specific musculoskeletal models were developed at each timepoint relative to osseointegration. Internal joint moments were calculated using inverse dynamics, muscle and joint reaction forces (JRFs) were estimated with static optimization. Changes in internal joint moments, JRFs, and joint loading-symmetry were compared using statistical parametric mapping (p≤ 0.05) before and after osseointegration. Amputated limb hip flexion moments and anterior JRFs decreased during terminal stance (p = 0.002, <0.001; respectively), while amputated limb hip abduction moments increased during mid-stance (p < 0.001), amputated hip rotation moment changed from internal to external throughout early stance (p < 0.001). Intact limb hip extension and knee flexion moments (p = 0.028, 0.032; respectively), superior and resultant knee JRFs (p = 0.046, 0.049; respectively) decreased during the loading response following prosthesis osseointegration. These results may indicate that the direct loading transmission of these novel prostheses create a more typical mechanical environment in bilateral joints, which is comparable with loading observed in able-bodied individuals and could decrease the risk of development or progression of osteoarthritis.

Indications of musculoskeletal health in deceased male individuals with lower-limb amputations: comparison to non-amputee and diabetic controls

Individuals with lower-limb amputations, many of whom have type 2 diabetes, experience impaired musculoskeletal health. This study: (1) compared residual and intact limbs of diabetic and non-diabetic post-mortem individuals with amputation to identify structures vulnerable to injury, and (2) compared findings to diabetic and healthy control groups to differentiate influences of amputation and diabetes on musculoskeletal health. Postmortem CT scans of three groups, ten individuals each, were included: (1) individuals with transtibial or transfemoral amputations, half with diabetes (2) diabetic controls, and (3) healthy controls. Hip and knee joint spaces, cross-sectional thigh muscle and fat areas, and cross-sectional bone properties (e.g. area, thickness, geometry) were measured. Wilcoxon Signed-Rank and Kruskal-Wallis tests assessed statistical significance. Asymmetry percentages between limbs assessed clinical significance. Residual limbs of individuals with amputation, particularly those with diabetes, had significantly less thigh muscle area and thinner distal femoral cortical bone compared to intact limbs. Compared to control groups, individuals with amputation had significantly narrower joint spaces, less thigh muscle area bilaterally, and thinner proximal femoral cortical bone in the residual limb. Diabetic individuals with amputation had the most clinically significant asymmetry. Findings tended to align with those of living individuals. However, lack of available medical information and small sample sizes reduced the anticipated clinical utility. Larger sample sizes of living individuals are needed to assess generalizability of findings. Quantifying musculoskeletal properties and differentiating influences of amputation and diabetes could eventually help direct rehabilitation techniques.

The effect of muscle atrophy in people with unilateral transtibial amputation for three activities: Gait alone does not tell the whole story

Amputation imposes significant challenges in locomotion to millions of people with limb loss worldwide. The decline in the use of the residual limb results in muscle atrophy that affects musculoskeletal dynamics in daily activities. The aim of this study was to quantify the lower limb muscle volume discrepancy based on magnetic resonance (MR) imaging and to combine this with motion analysis and musculoskeletal modelling to quantify the effects in the dynamics of key activities of daily living. Eight male participants with traumatic unilateral transtibial amputation were recruited who were at least six months after receiving their definitive prostheses. The muscle volume discrepancies were found to be largest at the knee extensors (35 %, p = 0.008), followed by the hip abductors (17 %, p = 0.008). Daily activities (level walking, standing up from a chair and ascending one step) were measured in a motion analysis laboratory and muscle and joint forces quantified using a detailed musculoskeletal model for people with unilateral transtibial amputation which was calibrated in terms of the muscle volume discrepancies post-amputation at a subject-specific level. Knee extensor muscle forces were lower at the residual limb than the intact limb for all activities (p ≤ 0.008); residual limb muscle forces of the hip abductors (p ≤ 0.031) and adductors (p ≤ 0.031) were lower for standing-up and ascending one step. While the reduced knee extensor force has been reported by other studies, our results suggest a new biomechanically-based mitigation strategy to improve functional mobility, which could be achieved through strengthening of the hip abd/adductor muscles.

Characterization of muscle recruitment during gait of bilateral transfemoral and through-knee persons with limb loss

Introduction: Due to loss in musculoskeletal capacity, there is an increased burden on the residual limbs of bilateral transfemoral and through-knee persons with limb loss. This reduced capacity is associated with an increased cost of walking that is detrimental to functionality. Compensatory gait strategies are adopted by this population. However, how these strategies relate to specific muscle recruitment is not known. The primary aim of this study is to characterize muscle recruitment during gait of this population. The secondary aim is to assess whether the measured kinematics can be actuated when the endurance of specific muscles is reduced and if this is the case, which alternative muscles facilitate this. Methods: 3D gait data and high-resolution magnetic resonance images were acquired from six bilateral transfemoral and through-knee persons with limb loss. Subject-specific anatomical muscle models were developed for each participant, and a validated musculoskeletal model was used to quantify muscle forces in two conditions: during normal gait (baseline) and when muscles, which were identified as functioning above a "healthy" level at baseline, have a reduced magnitude of maximum force capacity (reduced endurance simulation). To test the hypothesis that there are differences in muscle forces between the baseline trials and the simulations with reduced muscular endurance, a Bonferroni corrected two-way ANOVA with repeated measures was completed between the two states. Results: The baseline analysis showed that the hip flexors experience relatively high muscle activations during gait. The reduced endurance simulation found two scenarios. First, for 5 out of the 12 simulations, the baseline kinematics could not be reproduced with the reduced muscular capacity. Second, for 7 out of 12 cases where the baseline kinematics were achieved, this was possible with compensatory increased activation of some muscles with similar functions (p ≤ 0.003). Discussion: Evidently, due to the loss of the ankle plantar flexors, gait imposes a high demand on the flexor muscle group of the residual limb. This study highlights how the elevated cost of gait in this population manifests in muscle recruitment. To enhance functionality, it is critical to consider the mechanical demand on the hip flexors and to develop rehabilitation interventions accordingly.