Nothing is more important to an amputee wearing a prosthetic leg than keeping the prosthesis firmly anchored to the residual limb. The more the residuum moves around inside the socket, the less effective the ambulation, the greater the stress on limb tissues, and the higher the chance the limb will come off entirely, often precipitating a fall.
With conventional suspension methods (atmospheric suction, pin, anatomic, belt, etc.), prosthesis wearers typically experience 6-12 percent residual limb volume loss during the day, caused by alternating weight-bearing pressure during stance and gravity pulling during swing phase. As a result, an intimate socket fit at the beginning of the day deteriorates to a loose attachment in a few hours, either requiring bothersome addition of limb socks or resulting in increased pistoning with reduced proprioception and accelerating fatigue. A majority of lower-limb amputees who wear prosthetic limbs face this reality every day.
The 1999 introduction of a vacuum-assisted suspension system promised a better way. By removing air molecules from the sealed air space between a total surface weight-bearing socket and a prosthetic liner covering a residual limb, the vacuum holds the liner firmly against the socket wall, creating a vastly superior extraction force – the force required to create separation between the liner and socket – to any other current suspension method.
Testing with the system confirmed its effectiveness: For the average size limb (13 inches proximal circumference), an extraction force exceeding 150 pounds was required to separate liner from socket under vacuum. (For reference, extraction forces encountered in daily activities seldom exceed 20 pounds.) By comparison, less than one pound extraction force can cause separation with all other suspension methods. Not only does vacuum suspension create a secure bond between limb and socket at the beginning of the day, but by eliminating the pressure fluctuations within the socket normally encountered during ambulation, the system prevents daily residual limb volume loss altogether, thus maintaining the strong limb-socket bond morning to night.
Vacuum Suspension Benefits
• Superior linkage to prosthesis
• Reduced pressure on load-bearing areas
• Minimal residual limb volume fluctuations
• Improved proprioception
• Enhanced residual limb health
The intimate socket fit produced by vacuum assist also enhances the wearer’s spatial awareness (proprioception) and control of the prosthesis. The leg responds immediately to residual limb movement and feels lighter, thereby reducing energy expenditure and improving endurance.
Electronic Vacuum Innovations Foretell Better Sockets For Above-knee Amputees
Yet another benefit of vacuum suspension is substantially better limb health. By subjecting residual limb tissues to abusive pistoning with resulting excessive pressure and shear forces, other suspension methods frequently produce pressure sores and skin breakdown. Conversely, a vacuum socket environment is so limb-friendly that open sores have been observed to heal while the patient continues daily prosthesis use.
The substantial advantages of vacuum suspension can be achieved only with careful design and fabrication of a total surface weight-bearing socket that closely matches residual limb shape, a carefully selected roll-on gel liner, and for a transtibial socket an airtight flexible knee sleeve.
Since the introduction of the breakthrough Harmony Vacuum-Assisted Socket System a decade ago, various new innovations have expanded vacuum opportunities for amputees.
• Harmony – The original Harmony system has been enhanced with the introduction of two improved vacuum pump models. The Harmony is a mechanical in-line pump actuated by alternating weight-bearing pressure and swing- phase relief during ambulation to maintain negative pressure within the socket while cushioning each step. A plastic tube connects the pump to a valve on the back of the socket.
The Harmony mechanical system also features an integrated torsion adapter, which effectively replaces the normal ankle rotation of the human leg during ambulation. The Harmony mechanical units are appropriate only for transtibial applications and cannot be used with a long residuum.
• The LimbLogic™VS is a battery-powered system that can be mounted either in-line directly below the socket or external to the shaft for long residual limbs. The controller unit weighs less than a half pound and requires no external tubing.
Perhaps the most noteworthy advantage of the LimbLogic system is that it opens the door to vacuum suspension for above-knee amputees. As a result transfemoral sockets can be designed with lower trimlines, leading to significant improvements in range of motion and comfort, both standing and sitting.
Once set by the prosthetist, LimbLogic continually monitors and maintains the desired vacuum pressure within preset limits; the wearer can adjust the pressure within those limits using a small wireless remote unit. Both the controller and remote are water-resistant.
• The Harmony e-pulse adds the benefits of an externally mounted, battery-powered vacuum unit to the original Harmony system, replacing the in-line mechanical pump. Like the LimbLogic, the e-pulse can work with any residual limb length and thus can be used for both above-knee and below-knee patients.
The e-pulse offers four preset vacuum levels, easily selected by the wearer. The e-pulse is small, lightweight, quiet, and provides audio and visual feedback.
Will Insurance Cover My Prosthetic?
As with most O&P breakthrough technology, widespread insurance coverage for advanced vacuum suspension systems is not yet a reality…it will take time. When the now immensely popular C-Leg® microprocessor knee system was introduced a decade ago, the inevitable patient question “Is it covered by my insurance?” was almost always answered in the negative.
Today, C-Legs are frequently covered by insurance, including Medicare, with proper authorization and documentation. As the performance and comfort benefits of vacuum suspension become more widely appreciated, we may expect that this technology will likewise qualify for reimbursement.
Please visit one of our locations today. We see many patients from all over Southeast Texas and many parts of Louisiana. Our offices are located in Beaumont, Nederland/Port Arthur, and Jasper, Texas. Your initial consultation is complimentary.