A new approach for the pistoning measurement in transtibial prosthesis

A Pneumatically Controlled Prosthetic Socket for Transfemoral Amputees

Amputees typically experience changes in residual limb volume in their daily lives. It causes an uncomfortable fit of the socket by applying high pressure on the sensitive area of the residual limb or by loosening the socket. In this study, we developed a transfemoral prosthetic socket for above-the-knee amputees that ensures a good socket fit by maintaining uniform and constant contact pressure despite volume changes in the residual limb. The socket has two air bladders in the posterior femoral region, and the pneumatic controller is located on the tibia of the prosthesis. The pneumatic system aims to minimize unstable fitting of the socket and improve walking performance by inflating or deflating the air bladder. The developed socket autonomously maintains the air pressure inside the prosthetic socket at a steady-state error of 3 mmHg or less by adjusting the amount of air in the air bladder via closed-loop control. In the clinical trial, amputee participants walked on flat and inclined surfaces. The displacement between the residual limb and socket during the gait cycle was reduced by up to 33.4% after air injection into the socket. The inflatable bladder increased the knee flexion angle on the affected side, resulting in increased stride length and gait velocity. The pneumatic socket provides a stable and comfortable walking experience not only when walking on flat ground but also on slopes.

3D Motion Analysis for the Assessment of Dynamic Coupling in Transtibial Prosthetics: A Proof of Concept

Assessment of coupling between transtibial sockets and users is historically based on clinicians' observations and experience, but can be inaccurate and unreliable. Therefore, we present a proof of concept, for five out of six possible degrees of freedom coupling metric system for a socket, using motion analysis calibrated on a 3D printed limb substitute. The method is compatible with any socket suspension method and does not require prior modifications to the socket. Calibration trials were used to locate the axis of rotation of the knee joint referenced against a marker cluster on the thigh; this allowed for the identification of the limb during test trials despite the entire residuum being obscured from view by the socket. The error in the technique was found to be within 0.7 mm in displacement and 0.7 degrees in rotation, based on the control data. Dynamic testing showed the Inter Quartile Range (IQR) of inter time step variance was <0.5 mm/deg for all metrics. The method can form a basis for objective socket evaluation, improve clinical practice and the quality of life for amputees.

An Instrumented Printed Insert for Continuous Monitoring of Distal Limb Motion in Suction and Elevated Vacuum Sockets

A suction or elevated vacuum prosthetic socket that loses vacuum pressure may cause excessive limb motion, putting the user at risk of skin irritation, gait instability and injury. The purpose of this research was to develop a method to monitor distal limb motion and then test a small group of participants wearing suction sockets to identify variables that strongly influenced motion. A thin plastic insert holding two inductive sensor antennae was designed and printed. Inserts were placed in suction sockets made for four participants who regularly used suction or elevated vacuum suspension. Participants wore a liner with a trace amount of iron powder in the elastomer that served as a distance target for the sensors. In-lab testing demonstrated that the sensed distance increased when participants added socks and decreased when they removed socks, demonstrating proper sensor performance. Results from take-home testing (3–5 days) suggest that research investigation into cyclic limb motion for sock presence v. absence should be pursued, as should the influence of bodily position between bouts of walking. These variables may have an important influence on suspension. Long-term monitoring may provide clinical insight to improve fit and to enhance suction and elevated vacuum technology.

A simulation-based analysis of the effects of variable prosthesis stiffness on interface dynamics between the prosthetic socket and residual limb

Introduction: Loading of a residual limb within a prosthetic socket can cause tissue damage such as ulceration. Computational simulations may be useful tools for estimating tissue loading within the socket, and thus provide insights into how prosthesis designs affect residual limb-socket interface dynamics. The purpose of this study was to model and simulate residual limb-socket interface dynamics and evaluate the effects of varied prosthesis stiffness on interface dynamics during gait.

Methods: A spatial contact model of a residual limb-socket interface was developed and integrated into a gait model with a below-knee amputation. Gait trials were simulated for four subjects walking with low, medium, and high prosthesis stiffness settings. The effects of prosthesis stiffness on interface kinematics, normal pressure, and shear stresses were evaluated.

Results: Model-predicted values were similar to those reported previously in sensor-based experiments; increased stiffness resulted in greater average normal pressure and shear stress (p < 0.05).

Conclusions: These methods may be useful to aid experimental studies by providing insights into the effects of varied prosthesis design parameters or gait conditions on residual limb-socket interface dynamics. The current results suggest that these effects may be subject-specific.

Digital healthcare technologies: Modern tools to transform prosthetic care

INTRODUCTION

Digital healthcare technologies are transforming the face of prosthetic care. Millions of people with limb loss around the world do not have access to any form of rehabilitative healthcare. However, digital technologies provide a promising solution to augment the range and efficiency of prosthetists.

AREAS COVERED

The goal of this review is to introduce the digital technologies that have the potential to change clinical methods in prosthetic healthcare. Our target audience are researchers who are unfamiliar with the field of prostheses in general, especially with the newest technological developments. This review addresses technologies for: scanning of amputated limbs, limb-to-socket rectification, additive manufacturing of prosthetic sockets, and quantifying patient response to wearing sockets. This review does not address biomechatronic prostheses or biomechanical design practices.

EXPERT OPINION

Digital technologies will enable affordable prostheses to be built on a scale larger than with today's clinical practices. Large technological gaps need to be overcome to enable the mass production and distribution of prostheses digitally. However, recent advances in computational methods and CAD/CAM technologies are bridging this gap faster than ever before. We foresee that these technologies will return mobility and economic opportunity to amputees on a global scale in the near future.

The comprehensive lower limb amputee socket survey: Reliability and validity of the persian version

BACKGROUND

The Comprehensive Lower limb Amputee Socket Survey (CLASS) is a self-reported measure developed to assess prosthetic socket fit in individuals with lower limb amputation.

OBJECTIVE

To assess the reliability and validity of the Persian version of the CLASS.

STUDY DESIGN

Cross-sectional and repeated-measures.

METHODS

We evaluated the translation and back translation of the CLASS and made the required changes according to expert committee feedback. Then, we recruited 124 participants with unilateral lower limb amputation (89.5% men). Internal consistency was analyzed with Cronbach's alpha and test-retest reliability using intra-class correlation coefficients. Convergent construct validity was assessed by comparing the CLASS scores with the Persian version of the Trinity Amputation and Prosthesis Experience Scales (TAPES) scores. In addition, known groups construct validity was assessed by comparing CLASS scores between groups with different causes and levels of amputation.

RESULTS

Cronbach's alpha coefficient represented a very good internal consistency for all domains of the Persian CLASS (ranged from 0.86 to 0.92). The intra-class correlation coefficient for test-retest reliability for the Persian CLASS was good to excellent (ranged from 0.73 to 0.97). There was a significant correlation between the subscales of the Persian CLASS and satisfaction subscales of the Persian TAPES (p < 0.001). There was significant difference between comfort subscale of the Persian CLASS scores by level of amputation.

CONCLUSION

The Persian CLASS is a reliable and valid measure for evaluating prosthetic socket fit.

A Prosthetic Socket with Active Volume Compensation for Amputated Lower Limb

Typically, the actual volume of the residual limb changes over time. This causes the prosthesis to not fit, and then pain and skin disease. In this study, a prosthetic socket was developed to compensate for the volume change of the residual limb. Using an inflatable air bladder, the proposed socket monitors the pressure in the socket and keeps the pressure distribution uniform and constant while walking. The socket has three air bladders on anterior and posterior tibia areas, a latching type 3-way pneumatic valve and a portable control device. In the paper, the mechanical properties of the air bladder were investigated, and the electromagnetic analysis was performed to design the pneumatic valve. The controller is based on a hysteresis control algorithm with a closed loop, which keeps the pressure in the socket close to the initial set point over a long period of time. In experiments, the proposed prosthesis was tested through the gait simulator that can imitate a human’s gait cycle. The active volume compensation of the socket was successfully verified during repetitive gait cycle using the weight loads of 50, 70, and 90 kg and the residual limb model with a variety of volumes. It was confirmed that the pressure of the residual limb recovered to the initial state through the active control. The pressure inside the socket had a steady state error of less than 0.75% even if the volume of the residual limb was changed from −7% to +7%.

Silicone soft socket system for the treatment of geriatric transtibial amputees

Background

Outfitting geriatric amputees with a suitable prosthesis is a demanding task. The aim of this study was to determine the effect of prostheses outfitted with a silicone suspension interface system on a large group of transtibial amputees regarding walking distance, satisfaction of use and duration of daily use.

Methods

The study included 75 mostly geriatric transtibial amputees fitted with a rigid total contact socket with a silicone interface system called an Icelandic roll-on silicone socket (ICEROSS, Ossur, Reykjavik, Iceland). At follow-up 54 patients remained for assessment. Ambulatory performance was measured by first categorizing the patients into four subgroups regarding their walking capacity: 0–50 m, 50–100 m, 100–500 m and >500 m. The alteration in patient mobility was measured at admission, discharge and follow-up. Satisfaction and duration of daily use as well as use of walking aids were collated with a standard questionnaire.

Results

Between admission and discharge, patients showed significant improvement (p = <0.001) in walking distances. The walking distance diminished again between time of discharge and follow-up (p = <0.001). The parameters satisfaction with device and duration of daily use showed no significant differences and the same applied to male and female subjects.

Conclusions

Geriatric transtibial amputees fitted with prostheses attached via a silicone suction socket system showed significant improvements in walking distances and a high rate of satisfaction with the device. There were no statistically significant gender-specific differences among users of the ICEROSS system.

A Practical Approach for Evaluation of Socket Pistoning for Lower Limb Amputees

Although fit of the socket-suspension system is critical to lower limb amputees, monitoring of the fit is largely based on user feedback, which is subjective and often unreliable. Pistoning, defined as the relative displacement between the socket and the residual limb, is a well-accepted indicator of the fit of the socket-suspension system. However, opacity and rigidity of everyday prosthetic sockets make measurement of pistoning a challenging task. In this paper, we describe the development of a pistoning evaluation procedure that relies on two motion capture systems: a magnetic motion capture system used to measure the motion of the residual limb and an optical motion capture system used to measure the motion of the socket. Through synchronization of the two motion capture systems, the motion of the residual limb relative to the socket can be determined to derive the amplitude of pistoning. Here, we evaluated the performance of our approach through repeated calibration and a treadmill walking task with an amputee. Results demonstrate that this procedure, which does not rely on radiography unlike some existing methods, can be used to evaluate the fit of amputees' everyday sockets.

A Sensor Array for the Measurement of Relative Motion in Lower Limb Prosthetic Sockets

The relative motion between residual limb and prosthetic socket could be a relevant factor in quantifying socket fit. The measurement of these movements, particularly in dynamic gait situations, poses a challenging task. This paper presents the realization of a measurement concept based on multiple optical 2D-motion sensors. The performance of the system was evaluated on a test rig considering accuracy and precision as well as accomplished measurement frequency and reliability of the system. Additionally, results of a pilot study measuring the relative motion between residual limb and prosthetic socket at seven specific locations of one individual with transtibial amputation during straight level walking are presented. The sensor functionality of the array was confirmed and the test rig experiments were comparable to the previously tested functional model ( e r r rel = 0.52 ± 1.87 %). With a sampling frequency of 1.3 kHz to be distributed among the number of sensor units, the developed system is suitable for investigating the relative movement between residual limb and prosthetic socket in dynamic gait situations. Results of the pilot study show the majority of relative motion occurring during the second half of the gait cycle. The measured relative motions show the residual limb sinking deeper into the socket, extending in the Sagittal plane and rotating internally in the Transverse plane during stance phase. Data captured during swing phase indicate a lower limb extension in the Sagittal plane as well as an external rotation in the Transverse plane.

Systematic Experimental Assessment of a 2D-Motion Sensor to Detect Relative Movement between Residual Limb and Prosthetic Socket

A sensor system for measuring the relative movement between prosthetic socket and residual limb based on a 2D-motion sensor is introduced and thoroughly tested experimentally. The quantitative analysis of test rig evaluation is used to identify advantageous sensor settings and liner configurations. Considering these favorable settings, sensor functionality is quantified to errrel=0.52±1.78%. Advancing to convex measurement surfaces, the sensor shows absolute errors of errabs≤1 mm in an observable measurement scenario. The feasibility of measuring gait-induced relative movement with the proposed 2D-motion sensor is shown via a biomechanical plausibility study. Overall, the findings suggest that the proposed sensor system is suitable for investigating the relative movement between residual limb and prosthetic socket in dynamic gait situations.

Prosthesis donning and doffing questionnaire: Development and validation

OBJECTIVES

To develop a questionnaire that specifically evaluates the ability of trans-tibial amputees to don and doff a prosthesis and to investigate the psychometric properties of the newly developed questionnaire.

BACKGROUND

Prosthesis should be donned and doffed few times during the day and night; thus, it is important to measure ease of donning and doffing.

STUDY DESIGN

A cross-sectional study.

METHODS

The questionnaire was designed and evaluated by a group of experts. The final questionnaire was administered to 50 individuals with trans-tibial amputation. A test-retest study was also conducted on 20 amputees to assess the repeatability of questionnaire items.

RESULTS

The prosthesis donning and doffing questionnaire was developed and tested through a pilot study. Based on Kappa index, the questionnaire items showed correlation coefficients greater than 0.7, which indicate good reliability and repeatability. The majority of the participants had good hand dexterity (80%) and could perform all types of grasps. The mean satisfaction scores with donning and doffing were 69.9 and 81.4, respectively. Most of the respondents needed to don and doff the prosthesis 3.44 times per day. Based on a 7-point score, the total scores ranged between 3 and 7.

CONCLUSION

The prosthesis donning and doffing questionnaire items showed good psychometric properties. A scoring method was suggested based on the pilot sample, which requires further evaluation to be able to differentiate between more suspension types. A larger international multicenter evaluation is required in the future to measure the responsiveness of the scales. This questionnaire will be useful in the evaluation of the ability of amputees to don and doff a trans-tibial limb prosthesis. Clinical relevance Donning and doffing of prostheses are challenging tasks for many lower limb amputees. The prosthesis donning and doffing questionnaire, on its own or combined with other prosthetic evaluation questionnaires, has the potential to help manufacturers, clinicians, and researchers gain knowledge and improve the donning and doffing qualities of prostheses.

Clinical evaluation of a prosthetic suspension system: Looped silicone liner

OBJECTIVES

This study aimed to evaluate and compare a newly designed suspension system with a common suspension in the market.

STUDY DESIGN

Prospective study.

METHODS

Looped liners with hook fastener and Iceross Dermo Liner with pin/lock system were mechanically tested using a tensile testing machine in terms of system safety. A total of 10 transtibial amputees participated in this study and were asked to use these two different suspension systems. The pistoning was measured between the liner and socket through a photographic method. Three static axial loading conditions were implemented, namely, 30, 60, and 90 N. Furthermore, subjective feedback was obtained.

RESULTS

Tensile test results showed that both systems could safely tolerate the load applied to the prosthesis during ambulation. Clinical evaluation confirmed extremely low pistoning in both systems (i.e. less than 0.4 cm after adding 90 N traction load to the prosthesis). Subjective feedback also showed satisfaction with both systems. However, less traction at the end of the residual limb was reported while looped liner was used.

CONCLUSION

The looped liner with hook fastener is safe and a good alternative for individuals with transtibial amputation as this system could solve some problems with the current systems. Clinical relevance The looped liner and hook fastener were shown to be good alternative suspension for people with lower limb amputation especially those who have difficulty to use and align the pin/lock systems. This system could safely tolerate centrifugal forces applied to the prosthesis during normal and fast walking.

Development of an air pneumatic suspension system for transtibial prostheses

The suspension system and socket fitting of artificial limbs have major roles and vital effects on the comfort, mobility, and satisfaction of amputees. This paper introduces a new pneumatic suspension system that overcomes the drawbacks of current suspension systems in donning and doffing, change in volume during daily activities, and pressure distribution in the socket-stump interface. An air pneumatic suspension system (APSS) for total-contact sockets was designed and developed. Pistoning and pressure distribution in the socket-stump interface were tested for the new APSS. More than 95% of the area between each prosthetic socket and liner was measured using a Tekscan F-Scan pressure measurement which has developed matrix-based pressure sensing systems. The variance in pressure around the stump was 8.76 kPa. APSS exhibits less pressure concentration around the stump, improved pressure distribution, easy donning and doffing, adjustability to remain fitted to the socket during daily activities, and more adaptability to the changes in stump volume. The volume changes were adjusted by utility of air pressure sensor. The vertical displacement point and reliability of suspension were assessed using a photographic method. The optimum pressure in every level of loading weight was 55 kPa, and the maximum displacement was 6 mm when 90 N of weight was loaded.

Interface pressure in transtibial socket during ascent and descent on stairs and its effect on patient satisfaction

BACKGROUND

Transtibial amputees encounter stairs and steps during their daily activities. The excessive pressure between residual limb/socket may reduce the walking capability of transtibial prosthetic users during ascent and descent on stairs. The purposes of the research were to evaluate the interface pressure between Dermo (shuttle lock) and Seal-In X5 (prosthetic valve) interface systems during stair ascent and descent, and to determine their satisfaction effects on users.

METHODS

Ten amputees with unilateral transtibial amputation participated in the study. Interface pressure was recorded with F-socket transducer (9811E) during stair ascent and descent at self-selected speed. Each participant filled in a questionnaire about satisfaction and problems encountered with the use of the two interface systems.

FINDINGS

The resultant mean peak pressure (kPa) was significantly lower for the Dermo interface system compared to that of the Seal-In X5 interface system at the anterior, posterior and medial regions during stair ascent (63.14 vs. 80.14, 63.14 vs. 90.44, 49.21 vs. 66.04, respectively) and descent (67.11 vs. 80.41, 64.12 vs. 88.24, 47.33 vs. 65.11, respectively). Significant statistical difference existed between the two interface systems in terms of satisfaction and problems encountered (P<0.05).

INTERPRETATION

The Dermo interface system caused less pressure within the prosthetic socket compared to the Seal-In X5 interface system during stair negotiation. The qualitative survey also showed that the prosthesis users experienced fewer problems and increased satisfaction with the Dermo interface system.

Transtibial prosthesis suspension systems: systematic review of literature

BACKGROUND

Today a number of prosthetic suspension systems are available for transtibial amputees. Consideration of an appropriate suspension system can ensure that amputee's functional needs are satisfied. The higher the insight to suspension systems, the easier would be the selection for prosthetists. This review attempted to find scientific evidence pertaining to various transtibial suspension systems to provide selection criteria for clinicians.

METHODS

Databases of PubMed, Web of Science, and ScienceDirect were explored to find related articles. Search terms were as follows: "Transtibial prosthesis (32), prosthetic suspension (48), lower limb prosthesis (54), below-knee prosthesis (58), prosthetic liner (20), transtibial (193), and prosthetic socket (111)". Two reviewers separately examined the papers. Study design (case series of five or more subjects, retrospective or prospective), research instrument, sampling method, outcome measures and protocols were reviewed.

FINDINGS

Based on the selection criteria, 22 articles (15 prospective studies, and 7 surveys) remained. Sweat control was found to be a major concern with the available suspension liners. Donning and doffing procedures for soft liners are also problematic for some users, particularly those with upper limb weakness. Moreover, the total surface bearing (TSB) socket with pin/lock system is favored by the majority of amputees.

INTERPRETATION

In summary, no clinical evidence is available to suggest what kind of suspension system could have an influential effect as a "standard" system for all transtibial amputees. However, among various suspension systems for transtibial amputees, the Iceross system was favored by the majority of users in terms of function and comfort.

A comparison between the suction suspension system and the hypobaric Iceross Seal-In® X5 in transtibial amputees

BACKGROUND

The two passive vacuum suspension systems currently available in total surface-bearing sockets are the hypobaric Iceross Seal-In(®) and the suction suspension system.

OBJECTIVES

The purpose of this study was to compare the effect of the hypobaric Iceross Seal-In(®) liner with that of the suction suspension system for quality of life, pistoning, and prosthesis efficiency in unilateral transtibial amputees.

STUDY DESIGN

Single-group repeated measures.

METHODS

Ten amputees were enrolled. The pistoning test, used to compare vertical movement of the stump within the socket, and the energy cost of walking test were carried out when the amputees were wearing the suction suspension system and after 2, 5, and 7 weeks of Seal-In® X5 use. The Prosthesis Evaluation Questionnaire and the Houghton Scale Questionnaire of perceived mobility and quality of life with the prosthesis, and the Timed Up&Go Test and the Locomotor Capability Index for functional mobility were also administered at the beginning and end of the study.

RESULTS

The hypobaric Iceross Seal-In® X5 led to significant pistoning reduction and improvement on the Houghton Scale Questionnaire and 3 of 9 domains of the Prosthesis Evaluation Questionnaire. No statistical changes were observed in functional mobility or the energy cost of walking tests.

CONCLUSION

Replacing the suction suspension system with the hypobaric Iceross Seal-In® X5 improves quality of life in transtibial amputees.