Transfemoral (Above-knee) Suspension systems

Suspension that both prevents a vertical movement called "pistoning" and also controls rotation of the socket on the residual limb's soft tissue is difficult to obtain in the AK prosthesis.

Types of suspension, listed according to the frequency with prosthetists prescribe them:

1. Silesian bandage often used in the temporary prosthesis, because a new and rapidly changing limb cannot be fit with a suction suspension. The Silesian suspension is also useful for people with short RLs. The person must learn to tighten the belt sufficiently to prevent pistoning. However, excessive tightening, especially if it is done with inadequate weight-bearing through the prosthesis, can rotate the socket internally on the RL and produce uncomfortable groin or ASIS pressures. A permanent prosthesis can employ Silesian suspension by itself or in combination with suction to improve suspension and limit rotation.

2. TES (total elastic suspension) This suspension is similar in its function to the Silesian suspension, and can be more comfortable. The wide elastic belt wraps around the pelvis and closes with Velcro.

3. Suction People with transfemoral amputations perceive suction suspension to be subjectively lighter and easier to control than any other. Because suction can undermine the skin, it is appropriate only for those whose residual limbs are relatively long and unscarred. These limbs have large and regular surface areas over which suction forces can be distributed. Suction also requires a residual limb whose volume is stable. People whose limb volume changes due to problems like chronic renal disease or rapid weight change cannot use suction suspension.

   One dons a suction prosthesis while standing, by pulling the RL's soft tissue into the socket using a "pull sock." To do this, one must have good balance on the sound leg while flexing the trunk and hips, and possess good function and strength in both upper extremities. Thus, suction is inappropriate for people with poor UE function, or whose cardiac status might contraindicate strenuous UE activity while leaning over.

   To don the prosthesis, the wearer routes the pull sock through a valve hole located on the antero-medial wall of the socket's distal end. After pulling the soft tissue into the socket, the amputee maintains weight on the RL and replaces the valve.

   Patient education material on donning a suction socket, from Muilenburg, A.L., & Wilson, A.B. (1996). A Manual for Above-Knee Amputees: Donning the Suction Socket [On-line]. Available: http://www.oandp.com/manuals/ak12.htm

4. Pelvic belt The pelvic belt is very easy to don for people whose balance or UE function is poor. It is also appropriate for people with short residual limbs, because it controls rotation and provides excellent medial-lateral stability.

---

Last updated 5-19-01 Dave Thompson PT
return to prosthetic suspension systems