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In mechanical engineering, the stability of systems under various forces is critical for designing durable and efficient structures. One fundamental way to explore these concepts is by analyzing systems like two rods connected at a pivot point, O, with a torsional spring of spring constant k at the pivot point. This system is similar in appearance to a scissor jack used to change tires on a car. In this case, the arms of the linkage (equivalent to the rods in this system) are entirely vertical,...
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Mechanical Evaluation Of Unity Elevated Vacuum Suspension System.

H Gholizadeh1, E D Lemaire1,2, R Salekrostam3

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Summary
This summary is machine-generated.

The Össur Unity active vacuum system significantly reduced prosthetic limb-socket movement compared to other suspension methods. This active vacuum technology demonstrated superior control over pistoning and higher load tolerance during testing.

Keywords:
AmputationElevated vacuumProsthesisProsthetic limbProsthetic suspension systemRehabilitationsociodemographics

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Area of Science:

  • Prosthetics and Orthotics
  • Biomechanical Engineering
  • Materials Science

Background:

  • Residual limb-socket displacement is a key indicator of prosthetic suspension quality.
  • Active vacuum systems offer improved control over vertical movement compared to non-active suction systems.
  • This study investigates the mechanical performance of the Össur Unity active vacuum system.

Purpose of the Study:

  • To mechanically evaluate limb-socket displacement using the Össur Unity active vacuum system.
  • To compare the performance of active vacuum suspension against inactive vacuum and no suction conditions.
  • To assess the load-bearing capacity and failure points of different prosthetic socket configurations.

Main Methods:

  • Evaluated 48 conditions involving various socket materials (polypropylene, PETG, acrylic, Thermolyn), liner types (standard, high profile), and vacuum states (active, inactive, no suction).
  • Utilized an Instron 4428 test machine to apply linear ramped tensile loads (0-100N) to prosthetic molds.
  • Recorded displacement between the mold and socket, and measured the load before failure (10 mm displacement).

Main Results:

  • Active vacuum suspension showed minimal average displacement (0.30±0.16mm), outperforming inactive vacuum (0.32±0.16mm) and no suction (0.39±0.22mm).
  • Active vacuum systems supported significantly higher loads before failure (812±221N) compared to inactive vacuum (727±213N) and no suction (401±184N).
  • The highest load before failure was recorded with a cylindrical polypropylene socket and a high-profile liner (1142±53N).

Conclusions:

  • The Unity active vacuum system effectively controlled pistoning during regular activity and withstood high traction loads.
  • All tested suspension conditions were viable for loads under 100N.
  • Socket fabrication materials did not significantly impact the overall performance of the suspension systems.