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Management of socket fit is challenging for people using lower-limb prostheses because of residual limb volume fluctuation throughout the day. Releasing socket pressures during sitting (partial doffing) may help users increase their limb volume after they have undergone volume loss earlier in the day. The purpose of this research was to develop and evaluate a system to allow for quick and easy locking pin and socket panel release during sitting and relock upon standing. The system was to allow the partial doff tether length to be custom set for each user, accomplish release and relock in less than 2.0 s each, require only one hand, and require a finger push force comparable to a push button on a phone. A motor-driven release/relock system (240 g build weight) housed within the socket adjusts locking pin tether length, and an instrumented ratcheting dial adjusts socket panel position. Three participants with a trans-tibial amputation operated the system properly using one hand. For a partial doff, users preferred a tether length between 5 and 6 cm. All users executed release within 1.5 s and relock within 1.5 s.

Strategies to maintain prosthesis users' daily limb volume are needed.Test how intermittent incremental socket volume adjustments affect limb fluid volume and limb-socket distance.Repeated measures.People with transtibial limb loss walked on an outdoor trail wearing a motor-driven adjustable socket that they adjusted a small amount, approximately 0.3% socket volume, every 2 min using a mobile phone app. Limb fluid volume and sensed distance between the socket and a target in their elastomeric liner were monitored. A gradual socket enlargement phase was followed by a gradual socket reduction phase.An incremental socket enlargement significantly increased limb fluid volume (Participants' residual limb fluid volume increases during ambulation compensated for incremental socket volume increases. For incremental socket volume decreases, residual limb fluid volume decreases did not compensate and the socket fit became tighter.Results support the hypothesis that for people without co-morbidities, intermittent incremental socket volume enlargements are an effective accommodation strategy to increase limb fluid volume while maintaining socket fit. Intermittent incremental socket volume reductions decreased limb fluid volume but also made the socket fit tighter.

BACKGROUND: Loss of residual limb volume degrades socket fit and may require accommodation. OBJECTIVES: To examine if either of two accommodation strategies executed during resting, socket release with full socket size return and socket release with partial socket size return, enhanced limb fluid volume retention during subsequent activity. STUDY DESIGN: Two repeated-measures experiments were conducted to assess the effects of socket release on limb fluid volume retention. METHODS: Limb fluid volume was monitored while participants wore a socket with a single adjustable panel. Participants performed eight activity cycles that each included 10 minutes of sitting and 2 minutes of walking. The socket’s posterior panel and pin lock were released during the 5(th) cycle while participants were sitting. In one experiment (Full Return), the socket was returned to its pre-release size; in a second experiment (Partial Return), it was returned to 102% of its pre-release size. Short-term and long-term limb fluid volume retention were calculated and compared to a projected, No Intervention condition. RESULTS: Partial Return and Full Return short-term retentions and Partial Return long-term retention were greater than those projected under the control condition (p

Background Small intermittent adjustments of socket size using adjustable sockets may be a means for people with transtibial amputation to better maintain residual limb fluid volume and limb position while using a prosthesis. Methods Socket size, limb fluid volume, and distance from the limb to the socket, termed “sensed distance,” were recorded while participants with transtibial amputation walked on a treadmill wearing a motor-driven, cabled-panel, adjustable socket. Researchers made frequent socket size adjustments using a mobile phone app to identify participants' acceptable socket size range. Limb fluid volume and sensed distance were then monitored as incremental adjustments were made to the socket. Findings Prosthesis users in this study (n = 10) accepted socket sizes between −5% and +5% of their neutral socket volume. There was a rapid increase in limb fluid volume and sensed distance upon socket enlargement, and a rapid decrease upon reduction. Subsequently, there were gradual changes in fluid volume and sensed distance. While visually monitoring limb fluid volume data in real time, researchers were able to adjust socket size to maintain consistent limb fluid volume within a −0.7% to +0.9% volume change for 24 min. Interpretation Participant residual limbs compensated to socket size adjustment. Using socket-mounted sensors to monitor limb-socket mechanics, an automatic adjustable socket that maintains limb fluid volume may be possible and may improve socket fit in instances where fit deteriorates during use.

Objective: The purpose was to design, implement, and test a control system for a motor-actuated, cable-panel prosthetic socket that automatically maintains socket fit by continuous adjustment of the socket size. Methods: Sockets with motor-driven adjustable panels were fabricated for participants with transtibial amputation. A proportional-integral control system was implemented to adjust socket size based on Socket Fit Metric (SFM) data collected by an inductive sensor embedded within the socket wall. The sensed distance was representative of limb-to-socket distance. Testing was conducted with participants walking on a treadmill to characterize the system's capability to maintain a set point and to respond to a change in the set point. Results: Test results from 10 participants with transtibial amputation showed that the Integral of Absolute Error (IAE) to maintain a set point ranged from 0.001 to 0.046 mm with a median of 0.003 mm. When the set point was changed, IAE errors ranged from 0.001 to 0.005 mm, with a median of 0.003 mm. An IAE of 0.003 mm corresponded to approximately a 0.08% socket volume error, which was considered clinically acceptable. Conclusion: The capability of the control system to maintain and respond to a change in set point indicates that it is ready for evaluation outside of the laboratory. Significance: Integration of the developed control system into everyday prostheses may improve quality of life of prosthesis users by relieving them of the burden of continually adjusting socket size to maintain fit.

The purpose of this research was to create a thin ferrous polymer composite to be used as a target for inductive sensing in limb prosthetics. Inductive sensors are used to monitor limb-to-socket distance in prosthetic sockets, which reflects socket fit. A styrene&ndash, ethylene&ndash, ethylene/propylene&ndash, styrene (SEEPS) polymer was mixed with iron powder at three concentrations (75, 77, 85 wt%), and thin disk-shaped samples were fabricated (0.50, 0,75, 1.00 mm thickness). For 85 wt% samples of 0.50 mm thickness, which proved the best combination of high signal strength and low target volume, inductive sensor sensitivity ranged from 3.2E5 counts/mm at 0.00&ndash, 1.00 mm distances to 7.2E4 counts/mm at 4.00&ndash, 5.00 mm distances. The application of compressive stress (up to 425 kPa) introduced an absolute measurement error of less than 3.3 &mu, m. Tensile elasticity was 282 kPa, which is comparable to that of commercial elastomeric liners. Durability testing in the shoe of an able-bodied participant demonstrated a change in calibration coefficient of less than 3.8% over two weeks of wear. The ferrous polymer composite may facilitate the development of automatically adjusting sockets that use limb-to-socket distance measurement for feedback control.

BACKGROUND Management of fluid in the limbs is a challenge faced by people with disabilities. In prosthetics, a means for transtibial prosthesis users to stabilize their residual limb fluid volume during the day may improve socket fit. OBJECTIVE To determine if releasing the panels and locking pin of a cabled-panel adjustable socket during socket release significantly improved limb fluid volume recovery and retention over releasing the panels alone. DESIGN Repeated-measures experiment to assess the effects on limb fluid volume retention. SETTING Participants were tested in a laboratory setting while walking on a treadmill. INTERVENTION Release of a locking pin tether during sitting as a limb volume accommodation strategy. MAIN OUTCOME MEASURE Percent limb fluid volume retention for panel and pin release compared with panel release alone at 2 minutes (short term) and 50 minutes (long term) after subsequent activity. Limb fluid volume was monitored using bioimpedance analysis. RESULTS Median percent limb fluid volume retention for the panel and pin release was significantly greater than panel release alone for both anterior and posterior regions for the long term (P = .0499 and .0096, respectively) but not the short term (P = .0712 and .1580, respectively). CONCLUSION Augmenting panel release with pin release may be an effective accommodation strategy for prosthesis users with transtibial amputation to better retain limb fluid volume.

The objective of this research was to use computer-aided design software and a tabletop 3-D additive manufacturing system to design and fabricate custom plastic inserts for trans-tibial prosthesis users. Shape quality of inserts was tested right after they were inserted into participant’s test sockets and again after four weeks of wear. Inserts remained properly positioned and intact throughout testing. Right after insertion the inserts caused the socket to be slightly under-sized, by a mean of 0.11 mm, approximately 55% of the thickness of a nylon sheath. After four weeks of wear the under-sizing was less, averaging 0.03 mm, approximately 15% of the thickness of a nylon sheath. Thus the inserts settled into the sockets over time. If existing prosthetic design software packages were enhanced to conduct insert design and to automatically generate fabrication files for manufacturing, then computer manufactured inserts may offer advantages over traditional methods in terms of speed of fabrication, ease of design, modification, and record keeping.

Liner-to-socket distance measurement using inductive sensing may be an effective means to continuously monitor socket fit in people using trans-tibial prostheses. A practical limitation, however, is a means to incorporate a thin uniform-thickness layer of conductive or magnetically permeable target material into the wide range of prosthetic liner products that people with limb amputation commonly use. In this paper, a method is presented whereby a 0.50-mm thickness ferrous polymer made from a SEEPS polymer and iron powder that is formed adjacent to a 0.25-mm thick non-ferrous layer of SEEPS polymer is assembled between two sheets of elastic fabric material. Bench testing showed that the fabrication procedure achieved a root-mean-square error in the thickness of this construct of 58 &mu, m, helping to create a consistent calibration result over the entire surface. The original fabric backing of an off-the-shelf prosthetic liner was removed and replaced with the developed construct. When worn in the shoe of an able-bodied participant for 7.5 h per day for 28 days, the sensor well maintained the shape of its calibration curve at the start of wear, but a distance offset (shifting of the y-intercept) was introduced that increased during the initial approximately 12 days of wear. When the distance offset was corrected, for the primary distance range of clinical interest for this application (0.00&ndash, 5.00 mm), the sensor maintained its calibration within 4.4%. Before being used in clinical application for liner-to-socket distance monitoring, new ferrous liners may need to be pre-worn so as to achieve a consistent distance reference.

The objective of this research was to assess the performance of an embedded sensing system designed to measure the distance between a prosthetic socket wall and residual limb. Low-profile inductive sensors were laminated into prosthetic sockets and flexible ferromagnetic targets were created from elastomeric liners with embedded iron particles for four participants with transtibial amputation. Using insights from sensor performance testing, a novel calibration procedure was developed to quickly and accurately calibrate the multiple embedded sensors. The sensing system was evaluated through laboratory tests in which participants wore sock combinations with three distinct thicknesses and conducted a series of activities including standing, walking, and sitting. When a thicker sock was worn, the limb typically moved further away from the socket and peak-to-peak displacements decreased. However, sensors did not measure equivalent distances or displacements for a given sock combination, which provided information regarding the fit of the socket and how a sock change intervention influenced socket fit. Monitoring of limb&ndash, socket displacements may serve as a valuable tool for researchers and clinicians to quantitatively assess socket fit.