Vacuum-assisted Suspension Research Articles

Exploring the effects of increased socket-residual limb coupling integrity via vacuum assisted suspension on prosthetic control: a preliminary study in transtibial prosthesis users.

The prosthetic socket provides the critical interface between prosthesis and residuum. The purpose of this pilot study was to explore the effect of altering socket-residuum coupling integrity on limb and body control, through the use of vacuum-assisted suspension. A secondary purpose was to explore the potential use of two measurement tools designed to assess mobility in a clinical context. Individuals with unilateral transtibial amputation performed intentional sway (n = 7) and treadmill walking (n = 6) tasks at three vacuum levels. Sway deviation from a straight-line path to peripheral targets was measured using an instrumented balance platform. Step width variability and targeting accuracy were measured using an augmented reality treadmill. There was a significant difference in intentional sway performance toward the target on the anterior diagonal toward the prosthetic side (p = 0.036); higher vacuum levels tended toward less deviation from a straight-line path. We found no group differences between total intentional sway deviation, step width variability or stepping accuracy across vacuum levels. Improved socket-residuum coupling integrity via vacuum may have measurable effects on functional control that warrant further investigation. We highlight limitations of the clinical testing paradigms to inform future work.Implications for rehabilitationThe fit of the socket is a critical factor in the success of lower limb prosthesis use.Vacuum-assisted suspension modifies the coupling between the residuum and socket.Changes in socket-residuum coupling may lead to measurable differences in control; however, these may be activity and person-specific.Clinically intended instrumented tests of movement function derived for an intact anatomy should be used with caution when assessing prosthesis users.

Socket-residuum coupling integrity affects perception of external stimuli: Effects of altering the transtibial interface using vacuum-assisted suspension.

Relative movement between the socket and residual limb can impair function in prosthesis users. It is plausible that, in addition to its mechanical effect, the integrity of the socket-residuum interface influences the ability of an individual to sense tactile cues through the prosthesis. Vacuum-assisted suspension (VAS) has been shown to reduce relative movement at this interface, providing a means to test this premise. The purpose of this pilot study was to assess the effects of altering socket-residuum interface integrity through the VAS pressure level on the thresholds of perception of an externally applied vibration stimulus. Seven unilateral transtibial prosthesis users participated. Socket-residual limb integrity was altered using the VAS subatmospheric (vacuum) pressure level. Vibration perception tests were conducted at low, mid, and high vacuum levels, targeting 0, 8, and 19 in Hg respectively, and performed in partially loaded and fully loaded conditions. Vibration intensity was increased using a dial until participants delivered a verbal signal indicating it was perceptible, and the nominal intensity was recorded. Intensity thresholds decreased (ie, sensitivity increased) from low to high vacuum settings when fully loaded ( P = 0.008). Differences when partially loaded were nonsignificant and variable across participants. This study provides preliminary evidence that altering the integrity between the socket and residual limb by modifying the vacuum level affects sensation related to the external environment experienced through the prosthesis, although translation of these findings to real-world stimuli remains to be tested.

Daily socket comfort in transtibial amputee with a vacuum-assisted suspension system: study protocol of a randomized, multicenter, double-blind multiple N-of-1 trial

BackgroundThe main aim of this paper is to present the feasibility of rigorously designed multiple N-of-1 design in prosthetics research. While research of adequate power and high quality is often lacking in rehabilitation, N-of-1 trials can offer a feasible alternative to randomized controlled group trials, both increasing design power at group level and allowing a rigorous, statistically confirmed evaluation of effectiveness at a single patient level. The paper presents a multiple N-of-1 trial protocol, which aim is to evaluate the effectiveness of Unity, a prosthetic add-on suspension system for amputees, on patient-reported comfort during daily activities (main outcome measure), prosthesis wearing time, perception of limb-prosthesis fitting and stump volume and functional walking parameters.MethodsMulticenter, randomized, prospective, double-blind multiple N-of-1 trial using an introduction/withdrawal design alternating Unity connected/disconnected phases of randomized length on twenty patients with unilateral transtibial amputation. The primary outcome measure is the Prosthetic Socket Comfort Score (SCS), a validated measure of comfort, administered daily by an phone app designed for the study. Secondary outcomes measures will be collected during the 50 days period of the N-of-1 trial: (1) by the same app, daily for patient-reported limb-prosthesis fitting, stump volume variation, and daily wearing time of the prosthesis; (2) by a pedometer for the number of steps per day; (3) by blind assessors in the rehabilitation center during adjustment visits for functional walking parameter (L-Test, 6-minute walk test), and by the patient for the QUEST, and ABC-S. Effectiveness of the Unity system regarding SCS and daily secondary outcome measures will be tested by randomization test. The secondary outcome measures assessed during visits in the rehabilitation center will be analyzed by Non Overlap of All pairs. An estimate of the effect on the amputee population will be generated by aggregating each individual clinical trial (N-of-1 trial) by Hierarchical Bayesian methods.DiscussionThis study protocol was designed to answer the question “which device is best for THIS patient" and to conclude at a group level on the effectiveness of a new devic, using a Multiple N-of-1 trial, which is promising but underused in prosthetics research so far.Trial registrationN° ID-RCB 2020-A01309-30 Clintrial.gov : NCT04804150 - Retrospectively registered March 20th 2021.

A Comparison of the Effects of Pin and Vacuum-Assisted Suspension Systems in Individuals With Transtibial Amputation

ABSTRACT Introduction Suspension systems are essential components for a lower-limb prosthesis, as they provide sufficient prosthetic fit. Although various adverse and positive effects have been reported for suspension systems, it is important to determine the effects on the prosthesis users in detail. Objective The aim of this study was to compare the pin suspension system (PSS) with the vacuum-assisted suspension system (VASS) in terms of parameters including walking capacity, functional mobility, weight bearing on the operated side, prosthesis satisfaction, and body image perception. Study Design This is an original research report. Methods Nine individuals with transtibial amputation were evaluated. Both suspension systems were applied consecutively. Initially, participants used the PSS for 3 months after fabrication and adjustment of the prosthesis and a prosthetic training period. They then used the VASS for 3 months after a similar training period. After both prosthetic systems had been adjusted, L.A.S.A.R. Posture was used to determine weight bearing on the prosthetic side. The 6-minute walk test was applied for walking capacity, the timed up-and-go test was used to determine functional mobility, the Prosthetic Satisfaction Index was used for prosthetic satisfaction, and the Amputee Body Image Scale was used for body image perception. Results Significant differences were observed between PSS and VASS in terms of prosthetic side weight-bearing ratios, walking capacity, functional mobility, and prosthetic satisfaction (P < 0.05), all in favor of VASS. No significant difference was determined in terms of body image scores (P > 0.05). Conclusion In terms of function and prosthetic satisfaction in individuals with transtibial amputation, VASS was determined to be superior. The available evidence suggests that if there is no contraindication for the use of VASS, it may contribute to the individual with amputation functionally and increase the satisfaction with the prosthesis. Clinical Relevance Vacuum systems can make a positive contribution to reaching the goals for prosthesis users who are targeted to have high physical activity levels. This positive contribution includes increased weight transfer to the prosthetic side, an increase in mobility determinants, and increased prosthesis satisfaction, which has many dimensions.

Quality of life, body image, and mobility in lower-limb amputees using high-tech prostheses: A pragmatic trial.

High-tech prostheses are supposed to achieve better functional recovery over mechanical-controlled prostheses in lower-limb amputees. However, quantitative data are insufficient. We aimed to evaluate changes in quality of life, life satisfaction, perception of body image, and functional performance of lower-limb amputees when using a mechanical-controlled prosthesis versus a microprocessor-controlled knee (MPK) or transtibial vacuum-assisted suspension system (VASS) prosthesis. In this pragmatic study, 57 lower-limb amputees were assessed with the Satisfaction with the Prosthesis Questionnaire (SATPRO), revised Amputee Body Image Scale (ABIS-R), Trinity Amputation and Prosthesis Experience Scales (TAPES), Medical Outcomes Study Short Form-36 (SF-36) and 6-min walk test (6MWT). All assessments were performed under 2 conditions (i.e., using a mechanical-controlled prosthesis vs. an MPK/VASS prosthesis. Amputees who used an MPK/VASS prosthesis showed significant increases in all SF-36 subscale scores and all subscale scores of TAPES except adjustment to limitation (P=0.156). The amputees showed clinically relevant improvements in 6MWT (P<0.001) and in SATPRO and ABIS-R scores (P<0.001). Lower-limb amputees using an MPK/VASS prosthesis had better life satisfaction, quality of life and functional performance than those using a mechanical-controlled prosthesis.

Reported physical activity and quality of life in people with lower limb amputation using two types of prosthetic suspension systems

Vacuum-assisted suspension systems provide better suspension than non-vacuum systems, but data are limited on whether they improve physical activity levels and quality of life for people with amputation. To compare the physical activity and quality of life levels of people with transtibial amputation using PIN/LOCK suspension system or vacuum-assisted suspension systems with those of able-bodied controls and to investigate parameters associated with physical activity levels. A cross-sectional observational study. Fifty-one people with amputation and 51 controls participated. The International Physical Activity Questionnaire Short Form and Short Form 36 were used to measure the physical activity and quality of life, respectively. The total physical activity and Short Form 36 scores were significantly lower in the participants with amputation than the controls. There were no significant differences between the two types of suspension systems in terms of physical activity levels and quality of life. The vacuum-assisted suspension system users reported significantly more bodily pain on the Short Form 36 questionnaire than the controls (p = 0.003). The only parameter that correlated significantly with the total physical activity was the Short Form 36 physical functioning subscale (r = 0.302, p = 0.031). Contrary to our expectations, vacuum-assisted suspension system users compared to PIN/LOCK users did not report greater levels of physical activity or improved quality of life or levels closer to comparable controls. A better understanding of the effects of different prosthetic suspension systems on physical activity and quality of life may help clinicians when prescribing prostheses, as well as setting appropriate prosthetic expectations. This study suggests that vacuum-assisted suspension systems and PIN/LOCK suspension systems provide equal benefit to users with regards to physical activity and quality of life.

Transtibial Socket Design, Interface, and Suspension: A Clinical Practice Guideline

ABSTRACT Materials N/A Methods The guideline is based upon the best available evidence as it relates to socket design, interface, and suspension of definitive transtibial prostheses. Where possible, recommendations are drawn from systematic review and meta-analysis. Where this standard is unavailable, alternate academic literature has been used to support individual recommendations. Results Recommendation 1: The static and dynamic pressure distribution of the residual limb within the socket are essential considerations in patient comfort, function and well-being. Recommendation 2: Total surface bearing sockets are indicated to decrease fitting times and enable higher activity levels. Recommendation 3: Compared to traditional foam-based interfaces, viscoelastic interface liners are indicated to decrease dependence on walking aides, improve suspension, improve load distribution, decrease pain and increase comfort. Recommendation 4: Among modern suspension options, vacuum assisted suspension (VAS) sockets permits the least amount of pistoning within the socket, followed by suction suspension and then pin-lock suspension. The traditional suspension options of supracondylar, cuff and sleeve suspension provide comparatively compromised suspension. Recommendation 5: VAS sockets are indicated to decrease daily limb volume changes of the limb in the socket while facilitating more favorable pressure distribution during gait. Recommendation 6: VAS sockets require both awareness and compliance on the part of the end user and are not universally indicated. Conclusions These clinical practice guidelines summarize the available evidence related to the socket design, interface, and suspension of definitive transitibial prostheses. The noted clinical practice guidelines are meant to serve on as “guides.” They may not apply to all patients and clinical situations.

Evaluation of a Prototype Hybrid Vacuum Pump to Provide Vacuum-Assisted Suspension for Above-Knee Prostheses.

Vacuum-assisted suspension (VAS) of prosthetic sockets utilizes a pump to evacuate air from between the prosthetic liner and socket, and are available as mechanical or electric systems. This technical note describes a hybrid pump that benefits from the advantages of mechanical and electric systems, and evaluates a prototype as proof-of-concept. Cyclical bench testing of the hybrid pump mechanical system was performed using a materials testing system to assess the relationship between compression cycles and vacuum pressure. Phase 1 in vivo testing of the hybrid pump was performed by an able-bodied individual using prosthesis simulator boots walking on a treadmill, and phase 2 involved an above-knee prosthesis user walking with the hybrid pump and a commercial electric pump for comparison. Bench testing of 300 compression cycles produced a maximum vacuum of 24 in-Hg. In vivo testing demonstrated that the hybrid pump continued to pull vacuum during walking, and as opposed to the commercial electric pump, did not require reactivation of the electric system during phase 2 testing. The novelty of the hybrid pump is that while the electric system provides rapid, initial vacuum suspension, the mechanical system provides continuous air evacuation while walking to maintain suspension without reactivation of the electric system, thereby allowing battery power to be reserved for monitoring vacuum levels.

Transfemoral interfaces with vacuum assisted suspension comparison of gait, balance, and subjective analysis: Ischial containment versus brimless

ObjectiveInvestigate the effect of a brimless interface design compared with ischial ramus containment (IRC) of interfaces when using vacuum-assisted suspension (VAS) on transfemoral amputees (TFAs). DesignRandomized experimental crossover. SettingHousehold, community, and clinic. ParticipantsUnilateral TFAs (N=12 enrolled, N=10 analyzed). Mean age: 42.9 years. Mean residual limb length: 60.3% of the sound side femur length. Participants’ mean time as an amputee: 8.3 years and median AMP score: 43. Interventions(1) IRC VAS interface, and (2) brimless VAS interface. Average medial wall height for IRC interfaces was 0.7cm proximal to the distal-most aspect of the ischial tuberosity (IT). The medial wall on the brimless design was an average of 3.3cm distal to the distal-most aspect of the IT. Main outcome measuresSpatiotemporal gait parameters, limits of stability, four square step test, and subjective perception using the prosthetic evaluation questionnaire (PEQ). ResultsStep length was significantly improved towards the IRC (p=0.04), when calculating degree of asymmetry. Base of support was significantly narrowed toward the brimless (p=0.03). All subjective measures reached statistical significance in favor of improvement with the brimless design, compared to the IRC. ConclusionsThe brimless design was equivalent to IRC in most gait and balance outcome measures. However, step length was more symmetrical toward the IRC while base of support was narrowed toward the brimless demonstrating mixed inconsistent performance changes. Further, the PEQ demonstrated significant subjective improvements in prosthetic related function and quality of life when participants used the brimless design. Brimless interface design may be a clinically viable choice.

Using vacuum-assisted suspension to manage residual limb wounds in persons with transtibial amputation

Persons with amputation and residual limb wounds would benefit from the ability to continue wearing a prosthesis while healing. Sockets with vacuum-assisted suspension may reduce intra-socket motion and be less disruptive to wound healing. The purpose of this case series was to measure residual limb wound size over time in persons with transtibial amputation while using prostheses with vacuum-assisted suspension. Six subjects with residual limb wounds were fit with vacuum-assisted suspension sockets. Wound surface area was calculated using ImageJ software at the time of fit and each subsequent visit until closure. FINDINGS AND OUTCOME: Average wound surface area at initial measurement was 2.17 ± 0.65 cm(2). All subjects were instructed to continue their normal activity level while wounds healed, with a mean of 177.6 ± 113 days to wound closure. Results suggest that well-fitting sockets with vacuum-assisted suspension in compliant individuals did not preclude wound healing. Further research is required to substantiate these case-based observations. Residual limb wounds are typically treated by suspension of prosthetic use until healing occurs, increasing the risk of long-term prosthesis nonuse. Our results suggest that vacuum-assisted suspension sockets may be used while healing occurs.

Transfemoral sockets with vacuum-assisted suspension comparison of hip kinematics, socket position, contact pressure, and preference: Ischial containment versus brimless

The objective of this study was to investigate the effect of brimless compared with ischial ramus containment (IRC) prosthetic sockets when using vacuum-assisted suspension (VAS) on persons with a unilateral transfemoral amputation (TFA). A randomized crossover design with a 2 d accommodation was used. People with unilateral TFA (n = 9 analyzed) were enrolled. Interventions were IRC VAS and brimless VAS sockets. Main outcome measures included coronal hip angle and vertical and lateral socket movement as measured by X-ray, skin pressure measured by Tekscan, and preference measured subjectively. The brimless design was statistically equivalent to IRC in all measured coronal hip angles and vertical and lateral socket displacement. The peak/stance mean pressure in the medial proximal aspect of the socket was 322 mmHg in the IRC compared with 190 mmHg in the brimless condition. Except for medial proximal pressure, no other measures reached statistical significance. All subjects reported the brimless design to be more comfortable than the IRC in short-term preference. Brimless VAS socket design may be a clinically viable choice for people with TFA.

Methods for characterization of mechanical and electrical prosthetic vacuum pumps

Despite increasingly widespread adoption of vacuum-assisted suspension systems in prosthetic clinical practices, there remain gaps in the body of scientific knowledge guiding clinicians' choices of existing products. In this study, we identified important pump-performance metrics and developed techniques to objectively characterize the evacuation performance of prosthetic vacuum pumps. The sensitivity of the proposed techniques was assessed by characterizing the evacuation performance of two electrical (Harmony e-Pulse [Ottobock; Duderstadt, Germany] and LimbLogic VS [Ohio Willow Wood; Mt. Sterling, Ohio]) and three mechanical (Harmony P2, Harmony HD, and Harmony P3 [Ottobock]) prosthetic pumps in bench-top testing. Five fixed volume chambers ranging from 33 cm(3) (2 in.(3)) to 197 cm(3) (12 in.(3)) were used to represent different air volume spaces between a prosthetic socket and a liner-clad residual limb. All measurements were obtained at a vacuum gauge pressure of 57.6 kPa (17 inHg). The proposed techniques demonstrated sensitivity to the different electrical and mechanical pumps and, to a lesser degree, to the different setting adjustments of each pump. The sensitivity was less pronounced for the mechanical pumps, and future improvements for testing of mechanical vacuum pumps were proposed. Overall, this study successfully offers techniques feasible as standards for assessing the evacuation performance of prosthetic vacuum pump devices.

Vacuum-Assisted Socket Suspension Compared With Pin Suspension for Lower Extremity Amputees: Effect on Fit, Activity, and Limb Volume

Klute GK, Berge JS, Biggs W, Pongnumkul S, Popovic Z, Curless B. Vacuum-assisted socket suspension compared with pin suspension for lower extremity amputees: effect on fit, activity, and limb volume. Objective To investigate the effect of a vacuum-assisted socket suspension system as compared with pin suspension on lower extremity amputees. Design Randomized crossover with 3-week acclimation. Setting Household, community, and laboratory environments. Participants Unilateral, transtibial amputees (N=20 enrolled, N=5 completed). Interventions (1) Total surface–bearing socket with a vacuum-assisted suspension system (VASS), and (2) modified patellar tendon–bearing socket with a pin lock suspension system. Main Outcome Measures Activity level, residual limb volume before and after a 30-minute treadmill walk, residual limb pistoning, and Prosthesis Evaluation Questionnaire. Results Activity levels were significantly lower while wearing the vacuum-assisted socket suspension system than the pin suspension ( P=.0056; 38,000±9,000 steps per 2wk vs 73,000±18,000 steps per 2wk, respectively). Residual limb pistoning was significantly less while wearing the vacuum-assisted socket suspension system than the pin suspension ( P=.0021; 1±3mm vs 6±4mm, respectively). Treadmill walking had no effect on residual limb volume. In general, participants ranked their residual limb health higher, were less frustrated, and claimed it was easier to ambulate while wearing a pin suspension compared with the VASS. Conclusions The VASS resulted in a better fitting socket as measured by limb movement relative to the prosthetic socket (pistoning), although the clinical relevance of the small but statistically significant difference is difficult to discern. Treadmill walking had no effect, suggesting that a skilled prosthetist can control for daily limb volume fluctuations by using conventional, nonvacuum systems. Participants took approximately half as many steps while wearing the VASS which, when coupled with their subjective responses, suggests a preference for the pin suspension system.

Use of a Partial Foot Prosthesis With Vacuum-Assisted Suspension: A Case Study

In Brief Vacuum-assisted suspension uses the creation of a negative pressure differential to hold a gel liner securely to the walls of the prosthetic socket to reduce the migration of the residual limb within the prosthesis. The eliminated movement or pistoning of the residual limb within the socket is believed to contribute to increased comfort and function in persons with a transtibial amputation by reducing peak pressures during ambulation. A new socket system was developed with vacuum-assisted suspension for a person with partial foot amputation to take advantage of this better coupling. The purpose of this case study was to evaluate the use of a partial foot prosthesis with vacuum-assisted suspension in a 68-year-old man with a right transfemoral amputation and a left partial foot amputation, both of traumatic origin. A questionnaire was used to compare the subject's satisfaction and function between his previous and new prosthesis. Photographs of the residual limb were taken before initial fitting of the new prosthesis, 10 days after initial fitting, and at 2-month follow-up to document the appearance of the residual limb. The subject rated the prosthesis with vacuum-assisted suspension higher with regards to comfort during standing and walking (i.e., it was more comfortable) and lower for pain while wearing the prosthesis (i.e., it was less painful). Photographs at 2-month follow-up showed that the skin was healthier in overall appearance when compared with initial fitting. This case study suggests that the use of a prosthesis with vacuum-assisted suspension may be a viable design for improving comfort, function, and residual limb health for persons with partial foot amputation. This case study evaluated the use of a partial foot prosthesis with vacuum-assisted suspension in a 68-year-old male with a right transfemoral amputation and a left partial foot amputation. The subject rated the prosthesis with vacuum-assisted suspension higher in comfort and lower in pain than his previous prosthesis. Photographs at two-month follow-up showed that the skin was healthier in overall appearance when compared to initial fitting.