Presently, there are essentially three forms of prosthetic suspension utilized with above-knee (AK) amputation proximal to the femoral condyles: suction, silesian belt and hip joint with pelvic band. Suction may be used in combination with one of the other methods. (1)
Advantages of suction suspension include: greater freedom of movement, increased use of the remaining muscles, decreased pistoning, increased comfort due to elimination of belts and straps and better cosmesis. The classic suction socket is contraindicated in patients who have volume changes, poor balance, decreased manual dexterity and/or other systemic diseases that preclude the exertion needed to don the prosthesis, i.e., heart or lung disease (1). Therefore, the geriatric patient often is not a suitable candidate for this suspension system.
The silesian belt has the advantages of comfort with positive suspension, control of rotation and aid in adduction of the prosthesis. It is often used in combination with suction socket and can be hidden under clothing better than the hip joint with pelvic band. However, it is more cumbersome than the suction socket, allows for less prosthetic control and is less cosmetic than the suction socket (1). Because of the belt's placement, it is contraindicated in pregnancy and in patients who have had by-pass surgery or shunt placement in the remaining lower extremity (2).
The hip joint with pelvic band is useful for geriatric and obese patients because it gives positive suspension and better control of the prosthesis. The lever arm also helps absorb the lateral forces involved with short stumps (1). The drawbacks are the increased weight and cumbersome nature of the prosthesis that can lead to its decreased use.
In 1985, Ossurr Kristinsson described the ICEROSS, or Icelandic Roll-On Suction Socket, system. At that time, the second author began to experiment with silicone socks for suspension. As a result of the success of the Durr-Fillauer 3-S Suction Socket System introduced in 1988, he continued development of this idea for suspension of AK prostheses.
A silicone sock is fabricated using silicone gel and two or three nylon stockinettes laminated over an AK suction-type socket mold. A durable cloth strap with Velcro at the terminal end is laminated into the central portion of the distal end of the sock. This strap is pulled through the distal end of the socket and secured to the external surface of the prosthesis with a Velcro hook and pile system to aid in retention of the prosthesis (Figure 1) .
Another retention device utilized is a simple wooden wedge. Triangular wedges, 7 cm in length and 4 cm in width opposite the apex, are laminated into the silicone sock medially and laterally, parallel to one another at the approximate middle of the sock. The wedges then protrude through matching windows in the socket wall to provide suspension (Figure 2 and Figure 3 ). This mode of suspension is especially advantageous for geriatric patients due to the ease of donning and doffing. As the patient pushes the sock-covered stump into the socket, the wedges shape aid in alignment and lock into place for retention. The patient simply pushes in on the wedges to release the suspension and allow removal of the prosthesis.
The true incidence of lower extremity amputation in the U.S. is not known. It is estimated that 30,000-110,000 lower extremity amputations are performed per year (3,4,5). Thirty-three thousand AK amputations were performed in acute care, nonfederal hospitals in 1984, according to the U.S. Department of Health and Human Services (5). The ratio of below-knee (BK) amputations to AK amputations was reported as 10:7 in one reference (4) and 1:1 in another (5). Seventy-five percent of acquired lower extremity amputations are caused by disease states. Diabetes and peripheral vascular disease account for the majority, especially in the patient population of 60 years and older (5). It has also been stated that 85 percent of AK amputations are secondary to vascular disease (1).
Only about one-fourth of the geriatric amputee population are functional prosthetic users, with perhaps another fourth becoming functional users secondary to refinements (1). Across all age groups, two-thirds of BK amputees are functional ambulators with prostheses while only 20 percent of AK amputees will walk. The number of functional ambulators drops to one in 15 in the geriatric AK amputee population (3). There would appear to be a large population of geriatric patients that could benefit from this improved device. Given the prevalence of peripheral vascular disease and diabetes in this population, many amputees have had bypass grafts or shunts placed in the remaining lower extremity, thus precluding the use of currently available appliances. In addition, patients with heart and lung disease, causing decreased exertional ability, would benefit by an improved appliance.
We are presently testing several prototypes and are submitting a grant proposal through the VA Medical Center in Birmingham, Alabama, for long-term evaluation. Fourteen silicone sleeves have been fabricated for seven different AK amputees. Four of the amputees lost their limbs secondary to vascular insufficiency, and the other three were traumatic amputees. Two of the four elderly gentlemen who lost their legs from poor circulation have low activity levels, and two are fairly active. The three traumatic amputees remain very active.
No significant problems have been encountered with donning, even in patients with compromised heart and/or lung function. There have been no reports of slippage, regardless of temperature or perspiration. In fact, some of the patients reported decreased perspiration with the new suspension sock. Two patients who had used other suspension means, one a hip joint and the other a thoracic elastic belt, commented that the suction suspension was more comfortable and allowed increased activity.
The one disadvantage encountered thus far involves significant volume fluctuation of the stump, as evidenced by the number of sleeves (fourteen) fabricated for seven AK amputees. The movement of the limb in swing phase with this suspension apparently causes "milking" of the distal soft tissues. This results in stump shrinkage which may easily be remedied by the addition of a sock; however, if the volume reduction is great, it may necessitate the fabrication of a new, smaller silicone sock. It is, therefore, recommended that volume reduction be maximized before the silicone sock is fabricated.
No additional maintenance, beyond that needed for other AK prostheses, has been required. The patients have required minimal instruction on proper alignment of the prosthesis for donning. The usual gait training is the only other instruction necessary.
The AK suction sock suspension appears to provide a very functional, durable means of suspending an AK prosthesis with the advantages of suction, while negating the need for good manual dexterity and increased exertion. This should be of benefit to the geriatric population in particular. The lack of a strap or belt would benefit pregnant women and persons with AK amputations who have undergone by-pass surgery or shunt placement of the remaining lower extremity.
The authors would like to thank Mrs. Betty Barrett for her efforts in producing this manuscript.
Charles J. Dietzen, M.D., is a third year resident, Department of Rehabilitation Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294.
Jerald Harshberger, C.P., is president and owner of Harshberger Prosthetics, 903 21st Street South, Birmingham, Alabama 35205. Phone number (205) 328-5347.
Rama D. Pidikiti, M.D., is Chief of Rehabilitation Medicine Service, VA Medical Center, Birmingham, Alabama 35233, and assistant professor, Department of Rehabilitation Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294. Phone number (205) 9334390.