Clinical investigation of the interface pressure in the trans-tibial socket with Dermo and Seal-In X5 liner during walking and their effect on patient satisfaction

BACKGROUND: The interface pressure between the residual limb and prosthetic socket has a significant effect on an amputee's satisfaction and comfort. Liners provide a comfortable interface by adding a soft cushion between the residual limb and the socket. The Dermo and the Seal-In X5 liner are two new interface systems and, due to their relative infancy, very little are known about their effect on patient satisfaction. The aim of this study was to compare the interface pressure with these two liners and their effect on patient satisfaction. METHODS: Nine unilateral transtibial amputees participated in the study. Two prostheses were fabricated for each amputee, one with the Seal-In liner and one with the Dermo liner. Interface pressure was measured at the anterior, posterior, medial and lateral regions during walking on the level ground. Each subject filled in a Prosthetic Evaluation Questionnaire (PEQ) regarding the satisfaction with the two liners. Findings The mean peak pressures with the Seal-In liner was 34.0% higher at the anterior, 24.0% higher at the posterior and 7.0% higher at the medial regions of the socket (P=0.008, P=0.046, P=0.025) than it was with the Dermo Liner. There were no significant differences in the mean peak pressures between the two liners at the lateral regions. In addition, significant difference was found between the two liners both for satisfaction and problems (P<0.05). Interpretation There was less interface pressure between the socket and the residual limb with the Dermo liner. The results indicated that the Dermo liner provides more comfort in the socket than the Seal-In liner.     

Clinical evaluation of two prosthetic suspension systems in a bilateral transtibial amputee

ABSTRACT: The effects of Seal-In X5 and Dermo liner (?ssur) on suspension and patient's comfort in lower limb amputees are unclear. In this report, we consider the case of a 51-yr-old woman with bilateral transtibial amputation whose lower limbs were amputated because of peripheral vascular disease. The subject had bony and painful residual limbs, especially at the distal ends. Two prostheses that used Seal-In X5 liners and a pair of prostheses with Dermo liners were fabricated, and the subject wore each for a period of 2 wks. Once the 2 wks had passed, the pistoning within the socket was assessed and the patient was questioned as to her satisfaction with both liners. This study revealed that Seal-In X5 liner decreased the residual limb pain experienced by the patient and that 1-2 mm less pistoning occurred within the socket compared with the Dermo liner. However, the patient needed to put in extra effort for donning and doffing the prosthesis. Despite this, it is clear that the Seal-In X5 liner offers a viable alternative for individuals with transtibial amputations who do not have enough soft tissue around the bone, especially at the end of the residual limb.     

膝下残肢界面应力准动态有限元模型研究

目的:为计算小腿截肢患者行走过程中残肢和接受腔之间的界面压力.方法:根据残肢、骨骼和假肢接受腔的真实几何形状建立了准动态有限元模型,采用了自动面面接触模型模拟皮肤和接受腔衬套之间的边界摩擦和滑动,并在考虑行走过程中外力和惯性载荷的同时,考虑了膝关节刚体位移和残肢弹性变形之间的耦合.结果:对一个步态周期内的残肢界面压力进行了仿真计算,结果表明界面压力主要分布在髌韧带区、腘窝区、胫骨内外侧.在站立相,除髌韧带区外,其他区域的压力具有与地面反力相似的变化规律.结论:本文所建立的准动态模型考虑了患者行走过程中膝关节位移,更接近于人体真实运动,能够用于假肢接受腔界面特性的预测和现代假肢的数字化设计.     

A quasi-dynamic nonlinear finite element model to investigate prosthetic interface stresses during walking for trans-tibial amputees

BACKGROUND: To predict the interface pressure between residual limb and prosthetic socket for trans-tibial amputees during walking. METHODS: A quasi-dynamic finite element model was built based on the actual geometry of residual limb, internal bones and socket liner. To simulate the friction/slip boundary conditions between the skin and liner, automated surface-to-surface contact was used. Besides variable external loads and material inertia, the coupling between the large rigid displacement of knee joint and small elastic deformation of residual limb and prosthetic components were also considered. RESULTS: Interface pressure distribution was found to have the same profile during walking. The high pressures fall over popliteal depression, middle patella tendon, lateral tibia and medial tibia regions. Interface pressure predicted by static or quasi-dynamic analysis had the similar double-peaked waveform shape in stance phase. INTERPRETATION: The consideration of inertial effects and motion of knee joint cause 210% average variation of the area between the pressure curve and the horizontal line of pressure threshold between two cases, even though there is only a small change in the peak pressure. The findings in this paper show that the coupling dynamic effects of inertial loads and knee flexion must be considered to study interface pressure between residual limb and prosthetic socket during walking.     

Transtibial prosthetic socket pistoning: static evaluation of Seal-In(®) X5 and Dermo(®) Liner using motion analysis system

Background

The method of attachment of prosthesis to the residual limb (suspension) and socket fitting is a critical issue in the process of providing an amputee with prosthesis. Different suspension methods try to minimize the pistoning movement inside the socket. The Seal-In^® X5 and Dermo^® Liner by Ossur are new suspension liners that intend to reduce pistoning between the socket and liner. Since the effects of these new liners on suspension are unclear, the objective of this study was to compare the pistoning effect of Seal-In^® X5 and Dermo^® Liner by using Vicon Motion System.

Methods

Six transtibial amputees, using both the Iceross Seal-In^® X5 and the Iceross Dermo^® Liner, participated in the study. The vertical displacement (pistoning) was measured between the liner and socket in single limb support on the prosthetic limb (full-weight bearing), double limb support (semi-weight bearing), and non-weight bearing on the prosthetic limb, and also under three static vertical loading conditions (30 N, 60 N, and 90 N).

Findings

The results demonstrated that the pistoning within the socket when Seal-In^® X5 was used, decreased by 71% in comparison to the Iceross Dermo^® Liner. In addition, a significant difference between the two liners under different static conditions was found (p < 0.05).

Interpretation

Participants needed to put in extra effort for donning and doffing the prosthesis with Seal-In^® X5; however, this type of liner provided less pistoning. The new approach that uses the motion analysis system in this study might be an alternative for measuring the pistoning effect in the prosthetic socket.     

Evolution in prostheses for sprinters with lower-limb amputation]

For about 15 years, technical advances in prosthetic treatment have been the main factor in the increased performance of athletes with lower-limb amputation. For trans-tibial amputation, the prosthesis for sprinting is composed of a gel liner and a socket joined by a locking or virtual vacuum liner. Because of these dynamic properties, the carbon prosthetic foot equipped with tacks ensures outstanding performance. For trans-femoral amputation, a hydraulic swing and a stance control unit are added to the same prosthesis. In comparison with the able-bodied runner, athletes with amputation have smaller loading times in the prosthetic limb and larger ones in the sound limb. The length of the energy-storing prosthetic foot is determined by the "up-on-the-toes" running gait. The sprinting gait with trans-tibial amputation is almost symmetrical. The hip extensor effort is the main compensation of propulsion reduction with lower-limb amputation. With trans-femoral amputation, the lack of knee increases the asymmetry. The total prosthetic knee extension (early in late-swing phase and lasting during total stance phase) compensates with extension of both hips, especially the opposite one. The amputation and sound limb load transfer with lumbar hyperlordosis concern the pelvis, trunk and shoulders. Because of athletes with amputation, research in prosthetic treatment has progressed. The development of orthotics and prostheses for such athletes has benefited non-athletes with amputation.     

Gait characteristics of persons with bilateral transtibial amputations

The gait characteristics of persons with unilateral transtibial amputations are fairly well documented in the literature. However, much less is known about the gait of persons with bilateral transtibial amputations. This study used quantitative gait analysis to investigate the gait characteristics of 19 persons with bilateral transtibial amputations. To reduce variability between subjects, we fitted all subjects with Seattle Lightfoot II feet 2 weeks before their gait analyses. The data indicated that subjects walked with symmetrical temporospatial, kinematic, and kinetic parameters. Compared with nondisabled controls, the subjects with amputations walked with slower speeds and lower cadences, had shorter step lengths and wider step widths, and displayed hip hiking during swing phase. Additionally, compared with the nondisabled controls walking at comparable speeds, the subjects with amputations demonstrated reduced ankle dorsiflexion and knee flexion in stance phase, reduced peak ankle plantar flexor moment, reduced positive ankle power (i.e., energy return) in late stance, and increased positive and negative hip power. These results demonstrate the deficiencies in current prosthetic componentry and suggest that further research is needed to enhance prosthesis function and improve gait in persons with amputations.     

Interface pressures during ambulation using suction and vacuum-assisted prosthetic sockets

Interface pressures were measured during ambulation with a normal total-surface weight-bearing suction socket and a vacuum-assisted socket. The vacuum-assisted socket has been shown to eliminate daily volume loss. Urethane liners were instrumented with five force-sensing resistors to measure positive pressures and one air pressure sensor at the distal end of the liner to document negative pressures. Nine unilateral transtibial amputees participated in the study. The vacuum-assisted socket created significantly lower positive-pressure impulse (42.8, 39.6 kPa x s) and peak pressures (83.5, 80.0 kPa) during the stance phase. The pressure impulse (-10.5, -13.3 kPa x s), average (-21.2, -26.5 kPa), and peak (-28.5, -36.3 kPa) negative pressures during swing phase were significantly greater in magnitude with the vacuum-assisted socket. We believe that lower positive pressures seen during stance using the vacuum-assisted socket reduces the fluid forced out and greater negative pressures seen during swing increases the amount of fluid drawn into the limb, thereby preventing volume loss.     

Biomechanical risk factors for knee osteoarthritis when using passive and powered ankle–foot prostheses

BackgroundGait compensations following transtibial amputation negatively affect sound limb loading and increase the risk of knee osteoarthritis. Push-off assistance provided by new powered prostheses may decrease the demands on the sound limb. However, their effects in a young population in the early stages of prosthetic use are still unknown. The purpose of this study was to compare limb loading between 1. passive and powered ankle–foot prostheses, 2. sound and amputated limbs, and 3. individuals with amputations in the relatively early stages of prosthetic use and controls.MethodsTen young, active individuals with unilateral transtibial amputation and 10 controls underwent biomechanical gait analysis at three speeds. The peak external knee flexor and adductor moments, adductor moment's angular impulse, peak vertical ground reaction force and loading rate were calculated. Repeated measures ANOVAs compared between limbs, prostheses, and groups.FindingsThe powered prosthesis did not decrease the sound limb's peak adduction moment or its impulse, but did decrease the external flexor moment, peak vertical force and loading rate as speed increased. The powered prosthesis decreased the loading rate from controls. The sound limb did not display a significantly greater risk for knee osteoarthritis than the intact limb or than controls in either device.InterpretationIn the early stages of prosthetic use, young individuals with transtibial amputation display few biomechanical risk factors for knee osteoarthritis development. However, a powered ankle–foot prosthesis still offers some benefits and may be used prophylactically to mitigate potential increases of these variables with continued prosthetic use over time.     

Case study: survey of patient satisfaction with prosthesis quality and design among below-knee prosthetic leg socket users

The aim of this case study was to explore patient satisfaction with the quality of prosthetic leg sockets intended for persons with lower limb amputations. A qualitative study based on in-depth interviews, preceded by a questionnaire session, was carried out with patients from the Rehabilitation Center and Hospital in Malaysia. Twelve out-patient and in-patient amputees with lower limb amputations, specifically below-knee amputations, were chosen randomly. The analysis of patients’ narratives aimed to identify the functional and esthetic characteristics of currently used prosthetic leg sockets and any problems related to them. The obtained results indicated that out of the 12 participants, 41.7% and 25% were satisfied and somewhat satisfied with their current prosthetic sockets. Durability and comfort were rated by the participants as the most important characteristics of prosthetic sockets, with 83.3%. As regards the esthetic appearance of the socket, 66.7% of the respondents considered that the most important feature was the material from which the socket was fabricated. Thus, we conclude that current satisfaction levels with the quality of prosthetic sockets among amputees in Malaysia are suitable, prosthesis being preferred by many amputees. The results can be used to direct future research on cosmesis and functionality of prosthetic socket design.

• Implications for Rehabilitation

• Case study will help participants to get cost effective prosthetic leg socket.

• Develop prosthetic leg socket comfortable as comparative to existing one.

• Help Malaysian government to make policy to develop local prosthetic leg socket at affordable price.

     

A comparative study of conventional and energy-storing prosthetic feet in high-functioning transfemoral amputees

OBJECTIVE: To compare the results of gait analysis, timed walking tests, and socket comfort for transfemoral amputees wearing initially a Multiflex conventional prosthetic foot and then a Vari-Flex energy-storing prosthetic foot. DESIGN: Experimental crossover trial. SETTING: A regional prosthetic and amputee rehabilitation tertiary referral center in a teaching hospital. PARTICIPANTS: Six established unilateral transfemoral prosthetic users. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Gait analysis, a timed walking test, and a Prosthetic Socket Fit Comfort Score for each amputee wearing the Multiflex foot and then repeated wearing the Vari-Flex foot. RESULTS: Wearing the Vari-Flex foot, our subjects walked faster in the gait lab (1.38 +/- 0.13 m/s, P < .001) and took more equal step lengths at fast speed (1.063 +/- 0.05, P < .05). They also had greater peak ankle dorsiflexion at push-off on the prosthetic side (18.3 degrees +/-4.73 degrees, P<.001) and 3 times as much power from the prosthetic ankle at push-off (1.13 +/- 0.22 W/kg, P < .001). There were no significant changes in temporal symmetry or loading of the prosthetic limb, in the timed walking test with each foot, or in the comfort score. CONCLUSIONS: A transfemoral amputee who wears an energy-storing foot can have a more symmetric gait with regard to some measures of spatial symmetry, kinetics, and kinematics than one who wears a conventional foot. However, in this study important aspects such as more symmetric loading and comfort did not differ significantly between the 2 foot types.     

残肢与接受腔的三维建模及力学分析

目的：对残肢与接受腔进行三维重建及力学分析，寻求残肢与接受腔间生物力学交互作用，为假肢接受腔的设计提供科学依据。方法：利用CT扫描、图像处理和反求技术重构骨骼、皮肤及接受腔三维模型建立残肢与接受腔的有限元模型．进行有限元受力分析。结果：残肢的主要受力部位是膑韧带、后肌群、胫骨内凸、胫骨远端、腓骨头及腓骨远端；骨骼对力的传递作用显著。结论：残肢受力由穿戴受腔引起，通过骨骼从接受腔传递给软组织，通过改变接受腔形状可以改变残肢的受力分布，残肢与接受腔力学分析是假肢接受腔制定的前提和基础。     

The effect of a shock-absorbing pylon on the gait of persons with unilateral transtibial amputation

Shock-absorbing pylons (SAPs) are components that increase prosthetic compliance and provide shock absorption during walking, running, and other high-impact activities in persons with leg amputations. This study investigated the effect of SAPs on the gaits of persons who walk with transtibial prostheses. Two gait analyses were performed on 10 subjects walking with and without an Endolite TT (Telescopic-Torsion) Pylon. Comparison of kinematic and kinetic gait parameters indicated that few quantitative changes were found in the way people walked with and without the SAPs. The most consistent change among subjects was a reduction in the magnitude of an isolated-force transient that occurred during the prosthetic loading response phase, an effect that was more evident at higher speeds. Results from a questionnaire that was administered to subjects indicated they generally preferred walking with the SAP for reasons related to comfort. We conclude that SAPs may provide significant benefit for persons with transtibial amputations who are able to routinely walk at speeds above approximately 1.3 m/s.     

Comparison of transhumeral socket designs utilizing patient assessment and in vivo skeletal and socket motion tracking: a case study

Purpose: This case study compares the impact of two prosthetic socket designs, a “traditional” transhumeral (TH) socket design and a Compression Released Stabilized (CRS) socket. Methods: A CRS socket was compared to the existing socket of two persons with transhumeral amputation. Comparisons included assessments of patient comfort and satisfaction with fit, as well as dynamic kinematic assessment using a novel high-speed, high-resolution, bi-plane video radiography system (XROMM, for X-ray Reconstruction of Moving Morphology). Results: Subjects were more satisfied with the comfort of the traditional sockets, although they had positive impressions about aspects of the fit and style of the CRS socket, and thought that it provided better control. Dynamic kinematic assessment revealed that the CRS socket provided better control of the residual limb within the socket, and had less slippage as compared to a traditional TH socket design. Conclusions: The TH CRS socket provided better control of the residual limb within the socket, and had less slippage. However, participants were less satisfied with the comfort and overall utility of the CRS socket, and stated that additional fitting visits/modifications to the CRS socket were needed. It is possible that satisfaction with the CRS socket may have improved with prosthetic adjustment and more acclimation time.

• Implications for Rehabilitation

• A comfortable, good fitting prosthetic socket is the key factor in determining how long (or if) an upper limb amputee can tolerate wearing a prosthesis.

• This case series was a comparison of two socket designs, a 'traditional' socket design and a Compression Released Stabilized (CRS) socket design in persons with transhumeral amputation.

• The CRS socket provided better control of the residual limb within the socket, and had less slippage. However, its tightness made it more difficult to don.

• Both subjects were less satisfied with the comfort and overall utility of the CRS socket. However, satisfaction might have been improved with additional fitting visits and more acclimation time.

     

Comparative biomechanical analysis of energy-storing prosthetic feet.

Gait analysis was performed on eight men who had unilateral traumatic below-knee amputation and on nine control subjects. Each subject was given two prostheses--the Seattle Foot and the Flex Foot--which differed only in the energy-storing foot component. Analysis of subjects consisted of clinical gait observation, forceplate analysis of the ground reaction force (GRF) while using each prosthesis during level walking at the natural cadence, and evaluation of subject preference between the two prosthetic feet. In the control subjects, there was no significant asymmetry in any averaged GRF patterns or parameters. In the subjects with amputations, the amputated limb had a weaker propulsion and the nonamputated limb had a stronger propulsion than controls. This was true for both prostheses. During ambulation with the Flex Foot, there was a pattern of larger late vertical forces but smaller late anteroposterior and mediolateral forces. This is consistent with a medial heel whip, and it was observed when the Flex Foot was used. Three months after the biomechanical studies, four subjects used the Flex Foot exclusively, two used the Seattle Foot exclusively, and two used both, ie, the Flex Foot for sports and the Seattle Foot for work. Application of these results to the choice of prosthetic components is discussed.     

Use and satisfaction with prosthetic devices among persons with trauma-related amputations: a long-term outcome study

OBJECTIVE: To document and examine the use, satisfaction, and problems with prosthetic devices among persons who suffered a trauma-related lower limb amputation. DESIGN: Abstracted medical records and follow-up interview data were collected for a retrospective cohort of persons with a lower limb trauma-related amputation who received their acute care at the University of Maryland R. Adams Cowley Shock Trauma Center, Baltimore, MD, between 1984 and 1994. Patients with spinal cord injury, traumatic brain injury, or only toe amputations were excluded. RESULTS: There were 146 patients identified. Of those, 9% died during the acute admission and 3.5% died after discharge. Seventy-eight amputees were available for interview (68% response rate). The majority of those interviewed were male (87%), and two-thirds had undergone amputation before age 40 yr. Nearly 95% had a prosthesis and wore it an average of 80 hr (SD = 33) per week. Despite high use, only 43% reported being satisfied with the comfort of their prosthesis. About one-quarter of all users reported problems with wounds, skin irritation, or pain. Traumatic amputees used an average of four prostheses since injury, about one new prosthesis every 2 yr. Statistical analyses revealed that males reported higher prosthetic use (P < 0.01). Higher Injury Severity Score negatively impacted on prosthetic use (P < 0.01). Phantom pain negatively influenced reported satisfaction with the prosthesis (P < 0.03) CONCLUSIONS: Although almost all persons living with trauma-related amputations use prosthetic devices, the majority are not satisfied with prosthetic comfort. Phantom pain and residual limb skin problems are also common afflictions in this population.     

Mechanical properties of prosthetic limbs: adapting to the patient.

Lower-limb amputees have identified comfort and mobility as the two most important characteristics of a prosthesis. While these in turn depend on a multitude of factors, they are strongly influenced by the biomechanical performance of the prosthesis and the loading it imparts to the residual limb. Recent years have seen improvements in several prosthetic components that are designed to improve patient comfort and mobility. In this paper, we discuss two of these: VSAP and prosthetic foot-ankle systems; specifically, their mechanical properties and impact on amputee gait are presented.     

Testing of elastomeric liners used in limb prosthetics: classification of 15 products by mechanical performance

The mechanical properties of 15 elastomeric liner products used in limb prosthetics were evaluated under compressive, frictional, shear, and tensile loading conditions. All testing was conducted at load levels comparable to interface stress measurements reported on transtibial amputee subjects. For each test configuration, materials were classified into four groups based on the shapes of their response curves. For the 15 liners tested, there were 10 unique classification sets, indicating a wide range of unique materials. In general, silicone gel liners classified within the same groups thus were quite similar to each other. They were of lower compressive, shear, and tensile stiffness than the silicone elastomer products, consistent with their lightly cross-linked, high-fluid content structures. Silicone elastomer products better spanned the response groups than the gel liners, demonstrating a wide range of compressive, shear, and tensile stiffness values. Against a skin-like material, a urethane liner had the highest coefficient of friction of any liner tested, although coefficients of friction values for most of the materials were higher than interface shear:pressure ratios measured on amputee subjects using Pelite liners. The elastomeric liner material property data and response groupings provided here can potentially be useful to prosthetic fitting by providing quantitative information on similarities and differences among products.     

Sprint kinematics of athletes with lower-limb amputations.

OBJECTIVE: To determine and compare the kinematics of the sound and prosthetic limb in five of the world's best unilateral amputee sprinters. SUBJECTS: Five men, all unilateral lower-limb amputee (one transfemoral, four transtibial) athletes. The individual with transfemoral amputation used a Endolite Hi-activity prosthesis incorporating a CaTech hydraulic swing and stance control unit, a Flex-Foot Modular III, and an ischial containment total contact socket. Those with transtibial amputations used prostheses incorporating a Flex-Foot Modular III and patellar tendon-bearing socket, with silicone sheath liner (Iceross) and lanyard suspension. DESIGN: Case series. Subjects were videotaped sprinting through a performance area. Sagittal plane lower-limb kinematics derived from manual digitization (at 50 Hz) of the video were determined for three sprint trials of the prosthetic and sound limb. Hip, knee, and ankle kinematics of each subject's sound and prosthetic limb were compared to highlight kinematic alterations resulting from the use of individual prostheses. Comparisons were also made with mean data from five able-bodied men who had similar sprinting ability. RESULTS: Sound limb hip and knee kinematics in all subjects with amputation were comparable to those in able-bodied subjects. The prosthetic knee of the transfemoral amputee athlete fully extended early in swing and remained so through stance. In the transtibial amputee athletes, as in able-bodied subjects, a pattern of stance flexion-extension was evident for both limbs. During stance, prosthetic ankle angles of the transtibial amputee subjects were similar to those of the sound side and those of able-bodied subjects. CONCLUSION: Prosthetic limb kinematics in transtibial amputee subjects were similar to those for the sound limb, and individuals achieved an "up-on-the-toes" gait typical of able-bodied sprinting. Kinematics for the prosthetic limb of the transfemoral amputee subject were more typical of those seen for walking. This resulted in a sprinting gait with large kinematic asymmetries between contralateral limbs.     

Ground reaction forces and center of pressure patterns in the gait of children with amputation: preliminary report

Ground reaction forces and center of pressure (CP) were studied during gait in children with unilateral lower extremity amputations. Five children, three with knee disarticulations and two with above-knee amputations, walked at slow, normal, and fast speeds, while wearing a conventional SACH prosthetic foot and again, while wearing an experimental CAPP prosthetic foot. Fore-aft (F-A) and vertical force (VF) components and CP patterns were examined for a total of 90 trials. Walking speed had a significant effect on both F-A and VF amplitudes. No differences, however, were found between the force amplitudes of the SACH foot and CAPP foot. Significant asymmetries were found in the force and amplitudes of a child's natural limb versus the prosthetic limb; the retarding and propelling F-A forces in the prosthetic limb were significantly less than the corresponding forces in a child's natural limb. The CP patterns during stance phase were markedly different for a child's natural limb, prosthetic limb with the SACH foot, and prosthetic limb with the CAPP foot. With the CAPP foot, the CP remained in the forefoot region during stance. In contrast with the CAPP foot, the SACH foot had a potential for producing a flexor moment at the knee joint at the initiation of the foot-ground contact. Stability in the prosthetic knee was enhanced when the children wore a CAPP prosthetic foot.