Katheryn J. Allyn

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.

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.

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.

Self-reported prosthetic sock use among persons with transtibial amputation.

Background: Daily changes in the shape and size of the residual limb affect prosthetic socket fit. Prosthetic socks are often added or removed to manage changes in limb volume. Little has been published about how persons with transtibial amputations use socks to manage diurnal changes in volume and comfort. Objectives: To investigate prosthetic sock use with a customized, self-report questionnaire. Study design: Cross-sectional survey. Methods: Persons with transtibial amputation reported number, thickness, and timing of socks used over a 14-day period. Results: Data from 23 subjects (16 males and 7 females) were included. On average, socks were changed less than once per day (0.6/day) and ply increased over the day (4.8–5.5 ply). Subjects wore prostheses significantly longer (15.0–14.1 h, p = 0.02) and changed socks significantly more often (0.6/day–0.4/day, p = 0.03) on weekdays compared to weekends. Participants were also divided into two subgroups: those who used socks to manage limb volume and those who used socks for socket comfort. Sock use did not differ (p > 0.05) between subgroups. Conclusions: Sock changes are infrequent among persons with lower limb loss. Initial, verbal reports of sock use were often inconsistent with data measured by logs. Tools (e.g. sock logs or objective instruments) to better understand sock-use habits among persons with limb loss are needed. Clinical relevance Knowledge of prosthetic patients’ sock use may help practitioners enhance volume management strategies or troubleshoot fitting issues. Results showed that subjects generally added socks to account for volume loss, and end-of-day sock thickness frequently exceeded 5 ply. Use of sock logs in clinical practice may facilitate improved residual limb health.

Device to monitor sock use in people using prosthetic limbs: technical report.

A device using radio frequency identification (RFID) technology was developed to continuously monitor sock use in people who use prosthetic limbs. RFID tags were placed on prosthetic socks worn by subjects with transtibial limb loss, and a high-frequency RFID reader and antenna were placed in a portable unit mounted to the outside of the prosthetic socket. Bench testing showed the device to have a maximum read range between 5.6 cm and 12.7 cm, depending on the RFID tag used. Testing in a laboratory setting on three participants with transtibial amputation showed that the device correctly monitored sock presence during sitting, standing, and walking activity when one or two socks were worn but was less reliable when more socks were used. Accurate detection was sensitive to orientation of the tag relative to the reader, presence of carbon fiber in the prosthetic socket, pistoning of the limb in the socket, and overlap among the tags. Use of ultra-high-frequency RFID may overcome these limitations. With improvements, the technology may prove useful to practitioners prescribing volume accommodation strategies for patients by providing information about sock use between clinical visits, including timing and consistency of daily sock-ply changes.

Elastomeric liners for people with transtibial amputation: Survey of prosthetists’ clinical practices:

Background: A diverse range of elastomeric liner products are available to people with transtibial amputation. However, little information is available about how prosthetists select the product best suited to each patient. Objectives: To determine how prosthetists obtain information about liners, which features are most relevant to the selection process, and which products are used most for patients with transtibial amputation. Study design: Cross-sectional survey. Methods: A custom online survey was developed to solicit information about prosthetists’ liner selection practices. Prosthetists with experience managing transtibial patients were recruited via advertisements posted in magazines, at conferences, and on a listserv. Responses were analyzed to characterize prosthetists’ liner selection practices. Results: Data from 106 experienced prosthetists (mean age: 44.4 years, mean experience: 15.7 years) were included. Most prosthetists (94%) obtained liner information from manufacturer representatives, websites, or literature. On average, respondents factored nine different liner characteristics into their selection processes. Prosthetists reported experience with 16 unique liner products with their transtibial patients, but routinely used fewer than 3. Conclusion: Although many different prosthetic liners are available, prosthetists regularly use only a few select liner products. Tools or strategies to objectively compare prosthetic liners across manufacturers are likely needed to facilitate more diverse prescription practices. Clinical relevance Knowledge of prosthetists’ prosthetic liner selection practices may guide development of evidence-based resources or tools to facilitate matching patients with appropriate liners. Results of this study may also inform researchers and manufacturers about desirable liner characteristics and direct development of novel liner products to address prosthetists’ clinical needs.