Daniel S. Harrison

Effects of elevated vacuum on in-socket residual limb fluid volume

Bioimpedance analysis was used to measure the residual limb fluid volume of seven transtibial ampu- tee subjects using elevated vacuum sockets and nonele- vated vacuum sockets. Fluid volume changes were assessed during sessions with the subjects sitting, stand- ing, and walking. In general, fluid volume losses during 3 or 5 min walks and losses over the course of the 30 min test session were less for elevated vacuum than for suc- tion. Numerous variables, including the time of day that data were collected, soft tissue consistency, socket-to- limb size and shape differences, and subject health, may have affected the results and had an equivalent or greater effect on limb fluid volume compared with elevated vac- uum. Researchers should well consider these variables in the study design of future investigations on the effects of elevated vacuum on residual limb volume.

Clinical Utility of In-Socket Residual Limb Volume Change Measurement: Case Study Results

Bioimpedance analysis was used to measure conductive tissue extracellular fluid (ECF) volume changes in the residual limbs of four unilateral transtibial amputee subjects during standing and walking conditions. Results showed that all residual limbs experienced ECF volume decreases during 5 min standing intervals. During 5 min of walking immediately after a standing interval, the residual limbs of healthy subjects increased in ECF volume while those of diseased subjects, one with peripheral vascular disease and another with cardiovascular insufficiency and a high-salt intake, decreased. One subject demonstrated less absolute value ECF volume change during standing and walking at 12 months post-surgical revision compared with at six months. Presentation of bioimpedance data to patients improved compliance to practitioner recommendations and patient understanding. Results were useful towards clinical assessment, patient education, and decision-making about treatment.

Amputee socks: how does sock ply relate to sock thickness?

Background: The term ‘sock ply’ may be a source of confusion in prosthetics practice because there may not be a consistent relationship between sock ply and sock thickness. Objectives: The purpose of this study was to characterize how sock ply related to sock thickness for different sock materials commonly used in limb prosthetics. We also evaluated how sock thickness changed under loading conditions experienced while wearing a lower limb prosthesis compared with unstressed conditions. Study Design: Experimental. Mechanical assessment. Methods: Seven sock materials of varying ply and sheaths were tested using a custom instrument. Sock thickness under eight different compressive stress conditions and two different biaxial in-plane tensile strain conditions were measured. Results: For socks woven from a single material, thickness under walking stance phase conditions averaged 0.7, 1.2 and 1.5 mm for 1, 3 and 5-ply, respectively. For socks woven from several materials, the corresponding results were 0.4, 0.7 and 0.8 mm, respectively. Sock ply did not sum, e.g. a 3-ply sock was not three times the thickness of a 1-ply sock. Conclusions: Sock thickness and compressive stiffness are strongly dependent upon sock material, interface pressure, and in-plane biaxial strain. Clinical relevance Data may be useful towards selecting socks during fitting and towards understanding volume changes induced by adding socks. An alternative nomenclature for thickness based on sheath equivalence may be more intuitive to practitioners and to the industry.

Preliminary investigation of residual-limb fluid volume changes within one day

The purpose of this research was to investigate rates of residual-limb fluid volume change within one day for people with transtibial limb loss. Rates of fluid volume change during 30 min test sessions of sitting, standing, and walking activities were measured twice a day, once in the morning and once in the afternoon, on 12 regular prosthesis users with the use of bioimpedance analysis. Between test sessions, all subjects consumed food and drink, and subject activity ranged from low to high. The rate of fluid volume change within sessions ranged from -8.5 to 5.9 %/h (median: -2.2%/h). The rate of fluid volume change between sessions ranged from -2.7 to 0.9 %/h (median: -1.0%/h). The between-session rate of fluid volume change correlated highly with afternoon within-session rates of change (r = 0.9) but was not well correlated with morning within-session rates of change (r = 0.8). Subjects with peripheral arterial complications showed greater fluid volume loss rates during test sessions than between sessions. Rate of fluid volume change may be affected by sitting, standing, and walking activities; presence of peripheral arterial complications; being female; time since amputation; and wearing the socket without doffing for extended periods.

Does temporary socket removal affect residual limb fluid volume of trans-tibial amputees?

Background: Lower-limb prosthesis users typically experience residual limb volume losses over the course of the day that can detrimentally affect socket fit. Objectives: To determine whether temporarily doffing the prosthesis encouraged residual limb fluid volume recovery and whether the recovered fluid was maintained. Study Design: Experimental design. Methods: Residual limb fluid volume was monitored on 16 participants in three test sessions each. Participants conducted six cycles of resting/standing/walking. Between the third and fourth cycles, participants sat for 30 min with the prosthesis and liner: donned (ON), the prosthesis doffed but the liner donned (LINER), or the prosthesis and liner doffed (OFF). Results: Percentage fluid volume gain and retention were greatest for the OFF condition followed by the LINER condition. Participants experienced fluid volume losses for the ON condition. Conclusion: Doffing the prosthesis or both the prosthesis and liner during rest improved residual limb fluid volume retention compared with leaving the prosthesis and liner donned. Clinical relevance Practitioners should advise patients who undergo high daily limb volume losses to consider temporarily doffing their prosthesis. Fluid volume retention during subsequent activity will be highest if both the prosthesis and liner are doffed.

Post-doffing residual limb fluid volume change in people with trans-tibial amputation.

Background: Residual limb volume may change after doffing, affecting the limb shape measured and used as a starting point for socket design. Objectives: The purpose of this study was to compare residual limb fluid volume changes after doffing for different test configurations. Study Design: The study was a repeated measures experimental design with three conditions (Sit, Liner, and Walk). Methods: Residual limb fluid volume on 30 people with trans-tibial amputation was measured using bioimpedance analysis. Three tests were conducted – Sit: sit for 10 minutes, remove the prosthesis, socks and liner, sit for 10 minutes; Liner: sit for 10 minutes, remove the prosthesis and socks but not the liner, sit for 10 minutes; Walk: conduct sit, stand and walk activities for 30 minutes, remove the prosthesis, socks and liner, sit for 10 minutes. Results: The percentage fluid volume increase after doffing was significantly higher for Walk (2.8%) than for Sit (1.8%) (p = 0.03). The time to achieve a maximum or stable fluid volume was shorter for Liner (4.3 min) than for Sit (6.6 min) (p = 0.03). Conclusions: Activity before doffing intensified the post-doffing limb fluid volume increase. Maintaining a liner after doffing caused limb fluid volume to stabilize faster than removing the liner. Clinical relevance To minimize residual limb volume increase before casting or imaging, practitioners should have patients sit with their prosthesis donned for 10 minutes. Leaving a liner on the residuum will not reduce the post-doffing volume increase, but it will help to more quickly achieve a consistent limb fluid volume.

How does adding and removing liquid from socket bladders affect residual-limb fluid volume?

Adding and removing liquid from socket bladders is a means for people with limb loss to accommodate residual-limb volume change. We fit 19 people with transtibial amputation using their regular prosthetic socket with fluid bladders on the inside socket surface to undergo cycles of bladder liquid addition and removal. In each cycle, subjects sat, stood, and walked for 90 s with bladder liquid added, and then sat, stood, and walked for 90 s again with the bladder liquid removed. The amount of bladder liquid added was increased in each cycle. We used bioimpedance analysis to measure residual-limb fluid volume. Results showed that the preferred bladder liquid volume was 16.8 +/- 8.4 mL (mean +/- standard deviation), corresponding with 1.7% +/- 0.8% of the average socket volume between the bioimpedance voltage-sensing electrodes. Residual-limb fluid volume driven out of the residual limb when bladder liquid was added was typically not recovered upon subsequent bladder liquid removal. Of the 19 subjects, 15 experienced a gradual residual-limb fluid volume loss over the test session. Care should be taken when implementing adjustable socket technologies in people with limb loss. Reducing socket volume may accentuate residual-limb fluid volume loss.

Amputee socks: Sock thickness changes with normal use

Background: Prosthetic socks are expected to decrease in thickness and have reduced volume accommodation with normal use. It is unknown, however, to what degree they reduce in thickness over time. Objective: The goal of this study was to determine a correlation between the age of a prosthetic sock (defined as the out-of-package time) and the resulting change in thickness under standardized weight-bearing and non-weight-bearing conditions. Study design: Experimental, mechanical assessment. Methods: Used prosthetic socks were donated by donors with transtibial amputation. Sock thickness was measured on a custom instrument under conditions representative of normal use. Stress-thickness response was compared to that of equivalent new socks to quantify the effects of use on sock performance. Results: Sock thickness changed non-linearly over time. On average, socks were 75% ± 17% of their initial thickness after 1 month, while socks older than 1 month were 72% ± 18% of their initial thickness. The elasticity of socks did not change with age. Conclusion: The volume accommodation provided by used socks cannot be reliably predicted by ply or age. Direct measurement of total sock thickness may provide meaningful insight to quantify prosthetic users’ socket fit and guide volume accommodation recommendations. Clinical relevance The mean difference in thickness between 3-ply and 5-ply used socks was equal to the standard deviation of each ply group (0.3mm). Therefore, it is possible that a 3-ply sock worn for as a little as 1 month could have a greater thickness than a 5-ply sock worn for a month.

How do walking, standing, and resting influence transtibial amputee residual limb fluid volume?

The purpose of this research was to determine how fluid volume changes in the residual limbs of people with transtibial amputation were affected by activity during test sessions with equal durations of resting, standing, and walking. Residual limb extracellular fluid volume was measured using biompedance analysis in 24 participants. Results showed that all subjects lost fluid volume during standing with equal weight-bearing, averaging a loss rate of -0.4%/min and a mean loss over the 25 min test session of 2.6% (standard deviation [SD] 1.1). Sixteen subjects gained limb fluid volume during walking (mean gain of 1.0% [SD 2.5]), and fifteen gained fluid volume during rest (mean gain of 1.0% [SD 2.2]). Walking explained only 39.3% of the total session fluid volume change. There was a strong correlation between walk and rest fluid volume changes (-0.81). Subjects with peripheral arterial disease experienced relatively high fluid volume gains during sitting but minimal changes or losses during sit-to-stand and stand-to-sit transitioning. Healthy female subjects experienced high fluid volume changes during transitioning from sit-to-stand and stand-to-sit. The differences in fluid volume response among subjects suggest that volume accommodation technologies should be matched to the activity-dependent fluid transport characteristics of the individual prosthesis user.

Preliminary evaluation of a novel bladder-liner for facilitating residual limb fluid volume recovery without doffing

For people who wear a prosthetic limb, residual-limb fluid volume loss during the day may be problematic and detrimentally affect socket fit. The purpose of this research was to test the capability of a novel liner with adjustable bladders positioned within its wall to mitigate volume loss and facilitate limb fluid volume recovery and retention. Bioimpedance analysis was used to monitor fluid volume changes in the anterior and posterior residual limb of participants with transtibial amputation. Participants underwent six cycles of sitting for 90 s, standing for 90 s, and walking for 5 min with liquid within the bladder-liners. Between the third and fourth cycles, participants sat for 10 min with liquid left within the bladders (Liquid-In) or removed (Liquid-Out). Results showed that participants recovered more fluid volume during the 10 min of sitting with Liquid-Out than Liquid-In (p = 0.09 for anterior and p = 0.04 for posterior). However, those fluid volume recoveries were not well retained in the short term (after the fourth cycle) or the long term (after the sixth cycle). Physiologic differences between sessions, reflected in the rates of fluid volume change at the outset of the session, and excessive stiffness of the bladder-liners may have affected fluid volume retentions.