The Road to Comfort is Paved With Liners

Gerald Stark

Since the commercial introduction of Ossur's Iceross™ (Icelandic Roll-On Silicone Socket) more than 10 years ago, the race has been on for a better, more comfortable prosthetic fit. Particularly in the last three to five years, prosthetists and biomedical engineers have sought and experimented with the "perfect" materials, styles, and sizes for skin-socket interfaces. Their efforts have yielded a wealth of options for prosthetists and those with lower limb amputations or deficiencies worldwide.

Of special benefit to those with residual limb bony prominences, gel liners can offer greater comfort and enhanced suspension to most transtibial (below knee) amputees, as well as to a select number of people with transfemoral (above knee) amputations.

The graduation from prosthetic socks and sleeves to gel liners, of late termed "comfort products," began in Reykjavik, Iceland, where prosthetist and prosthesis wearer Ossur Kristinsson developed Iceross. This silicone, offthe- shelf liner offered revolutionary solutions to prosthetic suspension and comfort problems. Iceross, which is available in clear and two-color styles with 19 sizes, can also be used as a locking suspension socket. Incorporating the distal attachment plate and stabilizing matrix, the liner/socket offers wearers suspension security beyond folding the top edge of the liner over the socket.

Otto Bock, Siliconics, ALPS South Corp., Southern California Orthotics and Prosthetics (SCOPe), Fillauer, and Engineered Silicone Products also offer silicone liners. Otto Bock's new 6Y10 Silicone Liner offers a distal pneumatic air bladder that can be adjusted by the wearer with a pump located behind the knee. Fabricated with the shuttle locking mechanism, the liner is designed to accommodate those who experience distal residual limb problems.

Siliconics Custom Silicone Fabricators also offer tearresistant, customized silicone interfaces. The punctureresistant ALPS Clear-Pro SSA™ socket and liner are fabricated of transparent, 1.5mm or 3mm thick silicone.

SCOPe's Custom Silicone Protection replicates the thickness and function of the soft, strong skin in the calf area, and can be customized for extra cushioning over bony prominences. Fillauer's flesh-colored Silicone Suspension Liner is guaranteed to be tear-resistant for the first six months, and is also available for those with upper extremity limb differences. The Silicone Suspension Liner, available in 13 sizes, can be fabricated with the distal metal pin for a shuttle lock. Engineered Silicone Products' Aegis liner, which is distributed through Seattle Limb Systems, Pel Supply Co., and Knit-Rite, is tapered and pre-flexed at a 45-degree angle for true anatomical shape. Designed in three sizes and lengths specifically for transtibial amputees, the Aegis liner does not restrict patellar motion nor wrinkle behind the knee. Custom Silicone Protection, Silicone Suspension Liner, and Aegis are all fabricated of medicalgrade silicone.

Since some silicone interfaces require the use of powders, lotions, or ointments to be easily and comfortably donned and doffed, prosthetic innovators at Ohio Willow Wood Company (OWW), United States Manufacturing Company (USMC), and Ossur have developed textilecovered liners that facilitate use.

OWW's Alpha Cushion and Locking Liners are predecessors to both USMC's Luxury Liner and Ossur's Iceross Comfort. These silicone-free, thermoplastic elastomer gel liners covered in a slick, Spandex-like material are infused with skin-conditioning mineral oil. While some silicone or urethane liner wearers have complained of allergic reactions, OWW has not, to date, received any reports of residual limb skin irritation resulting from Alphas. Although Alphas are available in three sizes, three styles of gel distribution, and three gel thicknesses, they are also responsive to heat molding for a custom fit at at a off-the-shelf price. As with most other liners, Alphas can be ordered with a distal stabilizer for shuttle lock suspension.

Nearly identical to OWW's liners are the Luxury Liners from USMC. Available in 6 and 9mm gel thicknesses and three sizes, USMC's liner has both cushion and locking versions. Its locking liner is complemented by Master Lock componentry.

The new Iceross Comfort™, which boasts easier donning and doffing than the original Iceross, is manufactured with the same medical-grade, SenSil™ silicone gel and is also covered with highly-elastic, semitransparent fabric. While the Iceross Comfort ranges in thickness from 6mm distally to 2mm proximally, the Iceross Comfort Plus™ has a uniform 6mm thickness. As with the original Iceross, the Comfort and Comfort Plus are both available with the distal attachment, and neither require customization.

Caspers-Schneider Technologies, Inc., and Silipos offer a silicone-free interface option. For those seeking a fully-custom liner, Caspers- Schneider developed the Total Environment Control® (TEC®) Interface Systems. The TEC Original Custom Liner, fabricated of semi-transparent urethane, was designed to function like a human heel pad. The material absorbs and dissipates pressures associated with normal to high activity levels, and adjusts to residual limb volume fluctuation. Its nylon top edge protects the residual limb from socket forces and liner discoloration.

Noticing the attraction of off-the-shelf interfaces, Caspers-Schneider recently introduced the TEC Signature. Available in six standard sizes, the new transparent urethane liner features increased durability over its parent product while still adapting to limb volume changes.

Silipos' hypoallergenic Silosheath and Silosheath Active incorporate medical-grade mineral oil in their transparent nylon material. Available in eight sizes for those with regular to very active lifestyles, the Silosheath reduces skin breakdown and disperses shock and vibration. Variations of the Silosheath include the Double Cushion Silosheath, with an extra distal layer of gel, and the Extra Life Silosheath, which has a second sheath to extend the life of the product.

Single and Double Socket and Ultra Cushion Gel Liners are also available through Silipos. The Single and Double Socket Gel Liners are made with Du Pont's Coolmax® material, which wicks away moisture from the residual limb, thereby reducing potential for skin breakdown. The thicknesses correspond with a three-plus ply prosthetic sock for the Single, and four-plus for the Double. The Ultra Cushion Gel Liner for BKs is covered with a cotton/lycra fabric and has a reinforced nylon toe. Each of Silipos' gel liners is available in three sizes.

When considering the incorporation of a liner into a prosthetic system, both the prosthetist and the amputee should consider a few other factors as well. First, unless the flexible liner is compressible, the interface is still considered a hard socket and requires a sock for cushion. Second, since some liners tend to absorb bodily odors and perspiration, the wearer must keep the liner clean. Proper hygienic protocol can also reduce the chance of skin irritation. Finally, not all people with lower extremity amputations are candidates for prosthetic interfaces.

For some amputees, finding the proper liner has made a huge improvement in ability by diminishing limitations.

CP, FAAOP, Director of Product Development & Education