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Technical Brief

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

[+] Author and Article Information
Matthew J. Major

Jesse Brown VA Medical Center,
Northwestern University Prosthetics-Orthotics Center,
680 North Lake Shore Drive, Suite 1100,
Chicago, IL 60611
e-mail: matthew-major@northwestern.edu

Ryan Caldwell

Scheck and Siress Orthotics and Prosthetics,
Northwestern University Prosthetics-Orthotics Center,
680 North Lake Shore Drive, Suite 1100,
Chicago, IL 60611
e-mail: ryan.caldwell@northwestern.edu

Stefania Fatone

Northwestern University Prosthetics-Orthotics Center,
680 North Lake Shore Drive, Suite 1100,
Chicago, IL 60611
e-mail: s-fatone@northwestern.edu

Manuscript received January 13, 2015; final manuscript received April 3, 2015; published online August 6, 2015. Assoc. Editor: Carl Nelson.

J. Med. Devices 9(4), 044504 (Aug 06, 2015) (4 pages) Paper No: MED-15-1003; doi: 10.1115/1.4030507 History: Received January 13, 2015

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.

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References

Figures

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Fig. 1

Schematic of the hybrid pump design. Constituent parts include: (a) proximal female pyramid adapter, (b) distal male pyramid adapter, (c) proximal housing plate, (d) distal housing plate, (e) bladder pump (mechanical system), (f) electric pump (electric system), and (g) threaded posts (×4). The threaded posts act as guide rails during cyclical compression and extension of the bladder. The solid arrows indicate air flow from the socket volume during operation.

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Fig. 2

Walking simulator boots. Prosthetic components attach distal to the foot plate and mimic transtibial prosthesis use.

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Fig. 3

Location of the hybrid vacuum pump for use within a transfemoral prosthesis. Pyramid adaptors fixed to proximal and distal ends of the pump housing were used for installation of the pump between the socket and knee joint, respectively.

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Fig. 4

Results from (a) bench testing, (b) in vivo walking with simulator boots (the first and second dashed vertical lines represent the initiation of the electric system and walking, respectively), and (c) in vivo walking of a transfemoral prosthesis user with a commercial electric pump (Ohio WillowWood LimbLogic) and the hybrid pump

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