Comparing Socket Suspensions

Prosthetic suspension systems are the method used to hold a prosthetic limb securely onto the body. The three most common types are pin locking systems, suction suspension, and elevated vacuum. Each system affects comfort, skin health, stability, and overall control of the prosthesis, making suspension one of the most important parts of prosthetic fit.

Types of Prosthetic Suspension Systems

• Pin Locking Suspension

• Suction Suspension

• Elevated Vacuum Suspension

I. 🚀 Introduction: Why Suspension Matters

Have you used a prosthetic and dealt with skin irritations, or a fit that didn’t quite feel secure? Even after getting the perfect foot, and a well fitting socket the suspension can completely make/break the fit of a prosthesis.

There are three main suspension systems—Pin/Locking, Suction, and Elevated Vacuum. These are the foundational elements determining comfort and control of a prosthesis. This post will break down the pros and cons of each to help readers advocate for the best fit with their prosthetist.

I have personally tried all 3! I have also tried a thigh corset (which isn’t commonly used for below knee amputees). I have always gone back to pin & lock, but that is just what has worked best for me. I highly recommend trying any that your prosthetist thinks will work for you and then you can truly decide which one feels the most secure and provides you with the best control of your prosthesis.

II. 🔒 The Pin/Locking System

Here are the basics of this suspension system: pin is attached to the liner, which locks into a shuttle mechanism (lock) at the bottom of the socket., often with audible clicks for confirmation. A button on the lock mechanism is pressed to release the pin, allowing the prosthesis to be removed. 

• Pros:

  • Ease of Donning: Quick and simple to put on, especially for new users or those with limited dexterity.

  • Security: Provides a clear, audible, and tactile "lock" sensation, which offers psychological security.

  • Minimal Knee Interference: Less bulk around the knee, allowing for better bending compared to some other systems. 

    • This has been my biggest complaint with other suspension systems. I have limited range of motion in my knee so I don’t like anything making that more difficult.

  • Cost/Maintenance: Often the simplest and most robust system.

• Cons:

  • Piston Effect: Susceptible to movement (pistoning) inside the socket, which can cause skin issues or discomfort.

    • This is the most common complaint i hear from patients.

  • Distal Loading: Puts pressure on the very end (distal) of the residual limb.

• Best Suited For: New amputees, users with fluctuating limb volume, lower activity levels, and those who prioritize ease of use.

III. 💨 Traditional Suction Suspension (Skin-to-Socket Contact)

This system relies on a sleeve (or seal) or skin contact to create a vacuum seal between the residual limb and the socket wall. When putting the prosthesis on, air is pushed out through a valve at the bottom of the socket. As you move, the limb and socket naturally separate slightly, which increases the negative pressure (suction) inside, pulling the limb and socket together and holding it firmly. 

• Pros:

  • Less Pistoning: Offers better limb stability inside the socket than a locking pin system.

    • I absolutely loved this firm fit feel. I have never felt something more secure!

  • Better Proprioception: Many users report a more "natural" feeling and better awareness of the prosthetic foot's position.

  • Limb Volume: Better for limbs with relatively stable volume, though liners can adapt. 

• Cons:

  • Donning Difficulty: Requires skill and technique (sometimes requiring a donning sock/aid) to ensure all air is removed and the seal is properly formed.

  • Fit is Crucial: The seal can be easily lost if the limb shrinks or swells throughout the day. A poor fit or damaged sleeve can break the seal.

    • I always got holes in my sealing sleeve which would immediately break the seal making my leg feel completely disconnected.

  • Hygiene/Moisture: Requires clean skin and socket for an effective seal; can trap sweat/moisture.

• Best Suited For: Experienced users, those who desire a high degree of control, and consistent limb volume.

IV. 🔬 Elevated Vacuum (Active/Pumped Suspension)

This is a system where an external pump (electronic or mechanical/passive) actively pulls air out of the socket to maintain a near-perfect negative pressure environment. It ensures total surface contact, distributing pressure evenly and preventing movement (pistoning). 

• Pros:

  • The Gold Standard: Virtually eliminates pistoning, offering the most secure and controlled fit.

  • Limb Health: The negative pressure can actively draw fluid away, potentially improving blood flow and reducing skin problems.

  • Optimal for High Activity: Ideal for running, sports, and highly dynamic activities.

• Cons:

  • Complexity & Cost: More components mean a higher initial cost and potential for more maintenance/repair.

  • Noise/Weight: Pumps can add slight noise or weight (though tech is rapidly improving).

    • I tried one of these when in high school. i was mortified by the noise of my prosthesis “going off” during quiet moments in the classroom.

• Best Suited For: Active users, high-demand lifestyles, and those who struggle with persistent skin/comfort issues in other systems.

V. ⚖️ The Takeaway: Finding Your Perfect Match

I really encourage you to discuss your daily activities and goals with your prosthetist, there is no one "best" system—only the best system for You!