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Suitable for outdoor use
Activity Level (2) 3 (4)

Optimal socket connection is critical to an amputee’s comfort, security and stability. By pairing Biomimetic Hydraulic Technology with an elevated vacuum system, the design of EchelonVAC works to create a secure and comfortable socket connection.

By harnessing natural ankle motion, EchelonVAC quietly creates elevated vacuum, helping to maintain an optimally fitting socket throughout the day.

Key Features

  • Biomimetic Hydraulic Technology with integrated elevated vacuum
  • Walking motion generates a natural vacuum
  • No power required, quiet gentle operation
  • Lightweight, compact design
  • Low build height
  • E-carbon springs for efficient energy return
  • Split toe design for ground compliance on uneven terrain
  • Sandal Toe Foot Shell

How does EchelonVAC work?

With every step, the wearer presses their weight into the prosthesis, initially expelling air through a one-way valve. Simultaneously the ankle plantarflexes, actively drawing air out of the socket. This air is held in the vacuum chamber and expelled through a secondary one way valve as the tibia progresses and the ankle dorsiflexes.

The result is greater residual limb volume control and an improved connection between the residual limb and the socket. For the user, this reduces relative movement, improving proprioception and control of the prosthesis for greater comfort and safety every day.

EchelonVAC - How it works

Innovative Design

The innovative design of EchelonVAC is lightweight and has a low build height as no external power source is required.

With no batteries or pump to worry about, EchelonVAC is quiet and easy to fit.

When used in conjunction with a Silcare Breathe liner, the vacuum is applied directly to the residual limb to further enhance the connection between the limb and the socket.

The Evidence

Active vacuum systems help to stabilise residual limb volume to improve socket stability and proprioception. Scientific studies have shown that elevated vacuum systems help to:

  • Reduce volume fluctuation
  • Reduce interface pressures
  • Improve wound healing
  • Reduce pistoning
  • Improve gait symmetry, balance and reduce risk of falls
  • Greater comfort and improved overall satisfaction


Real Life Stories

Charlie’s Story

Dennis’s Story

Unique & Proven Echelon Technology

The Echelon range sits at the heart of our pioneering prosthetic philosophy which makes our products so popular with users around the world. Created with a sharp focus on replicating a natural and safe walking experience, each product in the Echelon Range has a characteristic to suit different users and their requirements, providing confidence in every step.


This not only provides excellent energy storing and release properties but also works in harmony with the range of movement in the ankle to provide a natural and comfortable walking experience. 


When walking up slopes, the additional range allows the body to move forward over the foot, reducing energy requirements by making rollover easier. When walking down slopes, the foot complies with the slope without forcing the leg forward, allowing for a more controlled descent.

Hydraulic damping and foot springs produce a visco-elastic response that simulates the behaviour of muscles by storing and releasing energy. When compared to non-hydraulic ankles*, this technology is clinically proven to provide comfort, safety, natural walking, balanced limb loading and overall greater patient satisfaction.

*Clinical studies, latest research papers and full references available on our website.

Clinical Compendium


Clinical Compendium

Blatchford Biomimetic Hydraulic Technology mimics the dynamic and adaptive qualities of muscle actuation to encourage more natural gait. Multiple independent scientific studies, comparing Blatchford hydraulic ankle-feet to non-hydraulic feet, have shown:

  • Greater comfort, reduced socket pressures
  • Improved safety, reduced risk of trips and falls
  • Smoother, easier and more natural gait
  • More evenly balanced inter-limb loading
  • Greater satisfaction

Download PDF

Download the AvalonK2 Whitepaper

Clinical Evidence

Over a decade after challenging conventional wisdom, new scientific evidence continues to be published on the medical advantages of hydraulic ankles. Discover our White Paper ‘A Study of Hydraulic Ankles’. 

Download PDF

*Clinical studies, latest research papers and full references available on our website.


Help & Support


EchelonVAC Clinical Evidence Reference

Improvements in Clinical Outcomes using Echelon compared to ESR feet

  • Reduced risk of tripping and falls
    • Increased minimum toe clearance during swing phase1,2
  • Improving standing balance on a slope
    • 24-25% reduction in mean inter-limb centre-of-pressure root mean square (COP RMS)3
  • Reduced energy expenditure during walking
    • Mean 11.8% reduction in energy use on level ground, across all walking speeds4
    • Mean 20.2% reduction in energy use on slopes, across all gradients4
    • Mean 8.3% faster walking speed for the same amount of effort4
  • Improved gait performance
    • Faster self-selected walking speed2,5-7
    • Higher PLUS-M scores than FlexFoot and FlexWalk style feet8
  • Improved ground compliance when walking on slopes
    • Increased plantarflexion peak during level walking, fast level walking and cambered walking9
    • Increased dorsiflexion peak during level walking, fast level walking and cambered walking9
  • Less of a prosthetic “dead spot” during gait
    • Reduced aggregate negative COP displacement5
    • Centre-of-pressure passes anterior to the shank statistically significantly earlier in stance5
    • Increased minimum instantaneous COM velocity during prosthetic-limb single support phase5
    • Reduced peak negative COP velocity7
    • Reduced COP posterior travel distance7
  • Improved ground compliance when walking on slopes
    • Increased plantarflexion range during slope descent10
    • Increased dorsiflexion range during slope ascent10
  • Helps protect vulnerable residual limb tissue, reducing likelihood of damage
    • Reduced peak stresses on residual limb11
    • Reduced stress RMS on residual limb11
    • Reduced loading rates on residual limb11
  • Greater contribution of prosthetic limb to support during walking
    • Increased residual knee negative work6
  • Reduced reliance on sound limb for support during walking
    • Reduced intact limb peak hip flexion moment6
    • Reduced intact limb peak dorsiflexion moment6
    • Reduced intact ankle negative work and total work6
    • Reduced intact limb total joint work6
  • Better symmetry of loading between prosthetic and sound limbs during standing on a slope
    • Degree of asymmetry closer to zero for 5/5 amputees3
  • Reduced residual and sound joint moments during standing of a slope
    • Significant reductions in both prosthetic and sound support moments12
  • Less pressure on the sole of the contralateral foot
    • Peak plantar-pressure13
  • Improved gait symmetry
    • Reduced stance phase timing asymmetry14
  • Patient reported outcome measures indicate improvements
    • Mean improvement across all Prosthesis Evaluation Questionnaire domains15
    • Bilateral patients showed highest mean improvement in satisfaction15
  • Subjective user preference for hydraulic ankle
    • 13/13 participants preferred hydraulic ankle13

Improvements in Clinical Outcomes using EVS compared to other suspension types

  • Fewer falls and less chance of multiple falls
    • No trans-tibial EVS users reported multiple falls, while 75% of the non-EV users did16
  • Better balance in functional clinical tests
    • Significant improvements in the Berg Balance Scale (BBS), the Four Square Step Test (FSST) and the Timed-Up-and-Go (TUG) test17
  • Better balance reported in patient-reported outcome measures
    • Improvements in the Activity Balance Confidence (ABC) scale questionnaire18
  • Fewer gait compensations19-21
  • Knee contact forces not significantly different to those of able-bodied controls22
  • Decreased pistoning
    • Reductions of over 69% and 83%, compared to suction21,23 and pin-lock24 suspensions, respectively, with other researchers and practitioners reporting similar observations18,19,25,26
  • Maintain residual limb volume
    • Suction suspension = mean 6.5% loss in volume; EVS = mean 3.7% increase in volume (N.B. it is possible that the increase may have been due to the fact that these individuals attended the clinic wearing their regular prostheses before using the EVS system)21
    • Other studies have since confirmed the observation that residuum volume loss is prevented by EVS19,27-30
  • Healthier residual limb tissue and skin
    • Higher trans-cutaneous oxygen measurement after activity31
    • Decreased trans-epidermal water loss after activity31
    • Decreased attenuated reactive hyperemia31
  • Reduced interface pressures
    • Pressures reduced by a mean of 4% compared to suction suspension32
    • Pressure impulses reduced by a mean of 7.5% compared to suction suspension32
  • Improved wound management
    • Continued prosthesis use while the wounds healed33-35
    • Wounds heal more quickly with EVS than other suspension methods36
  • Less painful than other suspension methods
    • Expert opinion19 and clinical case studies37 agree that EVS is less painful and more comfortable than other suspension methods.
    • Improved Socket Comfort Score compared to other suspension methods38
  • Patients are more satisfied wearing their prosthesis18,19,26,34,37-38.

Other Evidence

Vacuum levels generated:

When sensory control of the lower limb joints is lost, it is essential that the replacement behaves predictably. Consistency of performance is vital in providing prosthetic confidence. In terms of socket suspension method, this means providing the same good connection throughout a gait cycle, from one step to the next, and day-to-day, over the lifetime of the socket.

The difference between the vacuum levels generated by suction suspension, and that generated when using EVS, can be demonstrated by using a negative pressure gauge30. Figure 1 illustrates these measurements. Commonly, when the user bears weight on their prosthesis during stance phase, with suction suspension, the magnitude of the vacuum is low. When the leg is lifted into swing phase, the vacuum increases in magnitude, holding the socket to the residual limb. Comparatively, EVS retains a high level during stance phase – higher, in fact, than the peak swing phase vacuum with suction. Additionally, the difference between stance and swing phase is less pronounced, so that the vacuum level is more consistent throughout the gait cycle. For the amputee illustrated in the graph30, EVS gave an approximate 85% increase in peak vacuum magnitude and an approximate 67% reduction in the ‘amplitude’ of the vacuum measurement signal.

Figure 1: Negative pressure within the socket when walking using a one-way valve suction suspension (grey) and an elevated vacuum (EV) suspension. N.B. Data recorded with Echelon Vac system.

The difference in vacuum generated by the AvalonVAC, compared to that generated by the Echelon Vac, is shown in Figure 2. Despite differences in the method used (keel vs springs, different socket, different pressure gauge), when the same patient was asked to walk at ‘K2 walking speed’ (~2km/h, short steps), the trend of vacuum level to number of steps taken was comparable to when measured at ‘K3 walking speed’ (4-5km/h) with Echelon Vac.

Figure 2: Comparison of the EchelonVAC and AvalonVAC vacuum generation by number of steps (regardless of walking speed).


1. Riveras M, Ravera E, Ewins D, Shaheen AF, Catalfamo-Formento P. Minimum toe clearance and tripping probability in people with unilateral transtibial amputation walking on ramps with different prosthetic designs. Gait & Posture. 2020 Sep 1;81:41-8.
2. Johnson L, De Asha AR, Munjal R, et al. Toe clearance when walking in people with unilateral transtibial amputation: effects of passive hydraulic ankle. J Rehabil Res Dev 2014; 51: 429. Download
3. McGrath M, Laszczak P, Zahedi S, et al. Microprocessor knees with “standing support” and articulating, hydraulic ankles improve balance control and inter-limb loading during quiet standing. J Rehabil Assist Technol Eng 2018; 5: 2055668318795396. Download
4. Askew GN, McFarlane LA, Minetti AE, et al. Energy cost of ambulation in trans-tibial amputees using a dynamic-response foot with hydraulic versus rigid ‘ankle’: insights from body centre of mass dynamics. J NeuroEngineering Rehabil 2019; 16: 39. Download
5. De Asha AR, Munjal R, Kulkarni J, et al. Impact on the biomechanics of overground gait of using an ‘Echelon’ hydraulic ankle–foot device in unilateral trans-tibial and trans-femoral amputees. Clin Biomech 2014; 29: 728–734. Download
6. De Asha AR, Munjal R, Kulkarni J, et al. Walking speed related joint kinetic alterations in trans-tibial amputees: impact of hydraulic ’ankle’ damping. J Neuroengineering Rehabil 2013; 10: 1. Download
7. De Asha AR, Johnson L, Munjal R, et al. Attenuation of centre-of-pressure trajectory fluctuations under the prosthetic foot when using an articulating hydraulic ankle attachment compared to fixed attachment. Clin Biomech 2013; 28: 218–224. Download
8. Wurdeman SR, Stevens PM, Campbell JH. Mobility analysis of AmpuTees (MAAT 5): Impact of five common prosthetic ankle-foot categories for individuals with diabetic/dysvascular amputation. J Rehabil Assist Technol Eng 2019; 6: 2055668318820784. Download
9. Bai X, Ewins D, Crocombe AD, et al. Kinematic and biomimetic assessment of a hydraulic ankle/foot in level ground and camber walking. PLOS ONE 2017; 12: e0180836. Download
10. Bai X, Ewins D, Crocombe AD, et al. A biomechanical assessment of hydraulic ankle-foot devices with and without micro-processor control during slope ambulation in trans-femoral amputees. PLOS ONE 2018; 13: e0205093. Download
11. Portnoy S, Kristal A, Gefen A, et al. Outdoor dynamic subject-specific evaluation of internal stresses in the residual limb: hydraulic energy-stored prosthetic foot compared to conventional energy-stored prosthetic feet. Gait Posture 2012; 35: 121–125. Download
12. McGrath M, Davies KC, Laszczak P, et al. The influence of hydraulic ankles and microprocessor-control on the biomechanics of trans-tibial amputees during quiet standing on a 5° slope. Can Prosthet Orthot J; 2.
13. Moore R. Effect of a Prosthetic Foot with a Hydraulic Ankle Unit on the Contralateral Foot Peak Plantar Pressures in Individuals with Unilateral Amputation. JPO J Prosthet Orthot 2018; 30: 165–70. Download
14. Moore R. Effect on Stance Phase Timing Asymmetry in Individuals with Amputation Using Hydraulic Ankle Units. JPO J Prosthet Orthot 2016; 28: 44–48. Download
15. Sedki I, Moore R. Patient evaluation of the Echelon foot using the Seattle Prosthesis Evaluation Questionnaire. Prosthet Orthot Int 2013; 37: 250–254. Download
16. Rosenblatt NJ, Ehrhardt T. The effect of vacuum assisted socket suspension on prospective, community-based falls by users of lower limb prostheses. Gait Posture, (2017, accessed 2 May 2017).
17. Samitier CB, Guirao L, Costea M, et al. The benefits of using a vacuum-assisted socket system to improve balance and gait in elderly transtibial amputees. Prosthet Orthot Int 2016; 40: 83–88.
18. Ferraro C. Outcomes study of transtibial amputees using elevated vacuum suspension in comparison with pin suspension. JPO J Prosthet Orthot 2011; 23: 78–81.
19. Gholizadeh H, Lemaire ED, Eshraghi A. The evidence-base for elevated vacuum in lower limb prosthetics: Literature review and professional feedback. Clin Biomech 2016; 37: 108–116.
20. Xu H, Greenland K, Bloswick D, et al. Vacuum level effects on gait characteristics for unilateral transtibial amputees with elevated vacuum suspension. Clin Biomech Bristol Avon 2017; 43: 95–101.
21. Board WJ, Street GM, Caspers C. A comparison of trans-tibial amputee suction and vacuum socket conditions. Prosthet Orthot Int 2001; 25: 202–209.
22. Xu H, Greenland K, Bloswick D, et al. Vacuum level effects on knee contact force for unilateral transtibial amputees with elevated vacuum suspension. J Biomech 2017; 57: 110–116.
23. Gerschutz MJ, Hayne ML, Colvin JM, et al. Dynamic Effectiveness Evaluation of Elevated Vacuum Suspension. JPO J Prosthet Orthot 2015; 27: 161–165.
24. Klute GK, Berge JS, Biggs W, et al. Vacuum-assisted socket suspension compared with pin suspension for lower extremity amputees: effect on fit, activity, and limb volume. Arch Phys Med Rehabil 2011; 92: 1570–1575.
25. Darter BJ, Sinitski K, Wilken JM. Axial bone-socket displacement for persons with a traumatic transtibial amputation: The effect of elevated vacuum suspension at progressive body-weight loads. Prosthet Orthot Int 2016; 40: 552–557.
26. Scott H, Hughes J. Investigating The Use Of Elevated Vacuum Suspension On The Adult PFFD Patient: A Case Study. ACPOC 2013; 19: 7–12.
27. Youngblood RT, Brzostowski JT, Hafner BJ, et al. Effectiveness of elevated vacuum and suction prosthetic suspension systems in managing daily residual limb fluid volume change in people with transtibial amputation. Prosthet Orthot Int 2020; 0309364620909044.
28. Sanders JE, Harrison DS, Myers TR, et al. Effects of elevated vacuum on in-socket residual limb fluid volume: Case study results using bioimpedance analysis. J Rehabil Res Dev 2011; 48: 1231.
29. Street G. Vacuum and its effects on the limb. Orthopadie Tech 2006; 4: 1–7. Goswami J, Lynn R, Street G, et al. Walking in a vacuum-assisted socket shifts the stump fluid balance. Prosthet Orthot Int 2003; 27: 107–113.
30. 30. Goswami J, Lynn R, Street G, et al. Walking in a vacuum-assisted socket shifts the stump fluid balance. Prosthet Orthot Int 2003; 27: 107–113.
31. Rink C, Wernke MM, Powell HM, et al. Elevated vacuum suspension preserves residual-limb skin health in people with lower-limb amputation: Randomized clinical trial. J Rehabil Res Dev 2016; 53: 1121–1132.
32. Beil TL, Street GM, Covey SJ. Interface pressures during ambulation using suction and vacuum-assisted prosthetic sockets. J Rehabil Res Dev 2002; 39: 693.
33. Hoskins RD, Sutton EE, Kinor D, et al. Using vacuum-assisted suspension to manage residual limb wounds in persons with transtibial amputation: a case series. Prosthet Orthot Int 2014; 38: 68–74.
34. Traballesi M, Delussu AS, Fusco A, et al. Residual limb wounds or ulcers heal in transtibial amputees using an active suction socket system. A randomized controlled study. Eur J Phys Rehabil Med 2012; 48: 613–23.
35. Traballesi M, Averna T, Delussu AS, et al. Trans-tibial prosthesization in large area of residual limb wound: Is it possible? A case report. Disabil Rehabil Assist Technol 2009; 4: 373–375.
36. Brunelli S, Averna T, Delusso M, et al. Vacuum assisted socket system in transtibial amputees: Clinical report. Orthop-Tech Q Engl Ed; 2.
37. Arndt B, Caldwell R, Fatone S. Use of a partial foot prosthesis with vacuum-assisted suspension: A case study. JPO J Prosthet Orthot 2011; 23: 82–88.
38. Rosenblatt NJ, Ehrhardt T, Fergus R, et al. Effects of Vacuum-Assisted Socket Suspension on Energetic Costs of Walking, Functional Mobility, and Prosthesis-Related Quality of Life. JPO J Prosthet Orthot 2017; 29: 65–72.
39. Carvalho JA, Mongon MD, Belangero WD, et al. A case series featuring extremely short below-knee stumps. Prosthet Orthot Int 2012; 36: 236–238.
40. Sutton E, Hoskins R, Fosnight T. Using elevated vacuum to improve functional outcomes: A case report. JPO J Prosthet Orthot 2011; 23: 184–189.
41. McGrath M, Laszczak P, McCarthy J, et al. The biomechanical effects on gait of elevated vacuum suspension compared to suction suspension. Cape Town, South Africa, 2017.

See all the Clinical Evidence for every Blatchford product in our Clinical Evidence Finder Tool.

EchelonVAC Technical Data

Max. User Weight:


Activity Level:

2 3 4*

Size Range:


Component Weight:


Build Height:

121mm sizes 22-24
126mm sizes 25-26
131mm sizes 27-30

Maximum Vacuum:


*Maximum user weight 100 kg and always use one higher spring rate category than shown in Spring selection table
†Component weight shown is for a size 26cm without foot shell.

Selection Guide

Click the image for full size version.


Foot Shell Width Guide

Click on the table below to help choose the correct width when ordering the new Sandal Toe Foot Shell. For sizes 25, 26 and 27 you can now choose between Narrow (N) and Wide (W) fittings.


Alignment Wedge 940093
4mm Adjuster Key 940236
Socket Connection Kit 409663
Check Valve Service Kit 409863



EVAC 25 L N 3 S
 Product Code Size Side Width* Spring set Sandal Toe

*Narrow (N) and Wide (W) available for sizes 25-27 only.
For dark tone add suffix D. 
Example: foot size 25, left, narrow, spring rating 3, sandal toe