A Vacuum Donning Procedure for Transfemoral Suction Suspension Prostheses
Harry Layton, CPO
ABSTRACT
This article presents an alternative method of donning for transfemoral amputees who use or wish to use suction as their primary form of suspension. The author investigated the possibility of combining wet donning (lotion) with electromechanical reduction of air pressure (vacuum) within the prosthetic interface to develop a possible donning technique. The author hypothesized this method would allow a transfemoral amputee with additional physical impairments the possibility to consistently use suction as a form of suspension. Results showed positive results, indicating it is possible to provide total contact with a combination of residual-limb lubrication and electromechanical reduction of air pressure within the interface.
Key Words: Vacuum Donning; Suction Suspension.
Introduction
While suction is a preferable method of suction for most transfemoral amputees, not every transfemoral amputee can successfully use this type of suction (1). Some individuals have additional physical impairments that make it difficult to don a prosthesis.
The three most prevalent donning methodologies currently in use are 1) the original pull-sock "dry donning," method, 2) the lotion, lubricated "wet donning" method and the more recently developed silicone (gel) roll-on pin-lock interface system. Successful suction with all three of these methods can only be accomplished if the individual is standing; sufficient strength must be present in the individual's contralateral limb to stand and maintain balance. Sufficient hand dexterity and strength also are required to enable the patient to either pull on a sock (bandage) or roll on a silicone (gel) sleeve (liner). Wet donning requires the same contralateral limb strength to stand and balance while donning, with the added difficulty that any redundant tissue present can prevent total contact from occurring. Many amputees cannot tolerate the associated tissue stress that is generated by the shear forces exerted on the skin as a result of wet donning. Thus, amputees who also experience inferior contralateral limb strength/function, balance problems or inferior hand strength/agility/function sometimes cannot use suction suspension or reap the benefits of that type of suspension. To alleviate these restrictions, the author attempted to develop a method of suspension involving a combination of vacuum and lotion lubrication of the residual limb as an alternative donning method for transfemoral amputees using suction suspension.
Method
An individual in case study #1 was told postsurgery that she was not a prosthetic candidate and that she should allow herself time to get accustomed to a wheelchair. The individual was 75 years old, arthritic (both hands and contralateral knee) and legally blind. She was overweight with a pendulous abdomen and presented herself nine months postsurgery with a well-healed distal third transfemoral amputation. She also had significant redundant tissue with an ischial-level circumference smaller than midlevel circumferences.
Initially, this case was handled with routine impression and modification procedures. Static and dynamic transparent test sockets were donned with a bandage wrap. Having recently witnessed a young amputee wet don a knee-disarticulation prosthesis, the premise of using lubrication in conjunction with the application of vacuum seemed to be a logical prospect to consider. A prosthetic lamination pump was chosen because of availability, flexibility (since it is equipped with an adjustable bleed-off valve), and capacity (near 30 inches of pressure drop available).
A green-dot valve was useda. The insert center (green dot) was removed, and an adequately sized brass fitting was fit in its place to attach the valve insert to the surgical tubing connected to the vacuum intake line of the pump. When the patient's lotion-lubricated residual limb was positioned into the prosthetic interface (so that any free air flow was prevented), the patient stood up. At this point the prosthesis was held in place with the knee joint flexed. The vacuum pump was turned on, resulting in and two events occurring simultaneously.
The prosthesis began to move as it was beginning to pull up onto the patient's limb, and the patient began to giggle nervously in response to the sensation of negative pressure. She expressed increasing discomfort until the pump was turned off. The process of donning was begun with the bleed-off valve set at fifteen inches of negative pressure. The valve was quickly opened completely to achieve minimum negative pressure. The lowest pressure this pump would pull (approximately 9 lbs) was still uncomfortable for the patient. The pump was cycled off and on until donning was achieved. Donning occurred quickly, with total contact achieved in approximately 45 seconds. The modified valve was removed, and a conventional valve was installed for ambulating.
Reason dictated that further reduction of the pressure would be more likely to produce an acceptable sensory level for the amputee. In the search to find an alternative vacuum source, the author explored the various air pumpsb at a local department store. While there, the author noticed the aquariums in the pet section; in particular, the constant flow of air bubbles was noticed. Two pumps were chosenc,d: a single diaphragm and a double diaphragm pump. Both of these pumps were taken apart to evaluate their modification potential. Modified first was the single pump by simply sealing the air intake port and drilling a new intake port that was tapped to allow threading in a male barbed nipple fitting that would attach to a 1/8-inch flexible pvc tubinge,f. Next, the center of a green-dot valve insert was removed. This center was drilled with a size 21 drill bit and also tapped for the same size barbed fittinge . Then the valve insert was reassembled with this modified center (see Figure 1)
. The modified pump was attached to the modified valve, and a testing system was devised.
The test system was comprised of an existing transparent test socket and a piece of thin plastic film large enough to overlap the trimline of the socket.
A large rubber band was stretched over the trimline of the socket in a fashion to act as a retainer to keep the thin plastic pulled taut over the interface opening similar to a drum head. With the plastic membrane in place the modified valve insert was threaded into the valve housing. The pump was turned on and the plastic began to depress in the center as the air was evacuated from the interface. The plastic depressed but seemed to stall the pump's air flow. Attention was turned to the double diaphragm pump. With that pump's air intakes rearranged it then had two air lines (see Figure 2)
. Those two lines were joined with a "T" style barbed fitting that was then attached to the valve insertg. When this pump was attached to the same test arrangement and turned on, the plastic membrane depressed and continued to pull into the interface. This pump produces a negative pressure of six inches of mercury drop. This measurement was done using an automotive type vacuum gaugeh . The gauge was attached directly to the flexible tubing of the pump. When the vacuum gauge was attached to the prosthetic interface through a remote line to determine pressure experienced at the residual limb when exposed to the vacuum generated by the pump, the needle of the gauge almost reached the lowest pressure mark on the gauge face. That lowest mark was at two inches of vacuum. The calculated volume of air transfer that this pump was capable of producing at six inches of negative pressure is 126 cubic inches per minute. This appeared enough to try a patient test.
Results
The patient test was a success. The pump worked and the patient found the negative pressure to be more tolerable. Delivery of the prosthesis and the donning system was made (see Figure 3)
.
Case 2 was a previous suction suspension user who had advancing upper-limb arthritic involvement that was creating increasing difficulties in donning her prosthesis. Her redundant tissue made wet donning impossible. She also has contralateral limb involvement that creates difficulty in dry donning. With this vacuum-donning method and a couple of weeks of use, she developed the ability to don her prosthesis while sitting down.
Case 3 was a knee-disarticulation patient who had not been able to tolerate a suction fit due to many complicating factors. He is obese and has considerable scarring distally as a result of the trauma that led to his amputation. Dry donning was intolerable to him. He had ruled out the use of suction suspension and opted for a selisian band and prosthetic socks. Vacuum donning also has worked for him.
Case 4 was a younger amputee who was having difficulty using the pull-sock donning technique. He would get so tense and hyper while trying to use a pull sock that he would generally either have the sock removed when his limb still lacked two inches of making distal contact or he would achieve total contact with a full circumference of wrap still around his residual limb. He has been successful with this method and prefers it to the pull-sock procedure. This method has been used with success in fitting nine amputees (see Table A)
. Of the nine, one has passed away; one sustained a debilitating stroke and has since quit prosthetic use; one has migrated to wet donning without the pump; and the remaining six are still using the vacuum-donning system.
There has been no incidence of skin damage associated with the negative pressure developed by this donning system. One patient had mistakenly left her pump turned on (repeatedly) for five minutes at a time while donning to ensure total contact had been achieved. Even in her case she felt no ill effects. Nor were any signs visible in conjunction with that length of exposure. Any discomfort that has been felt by the amputees in relation to the negative pressure has been expressed as tingling.
Three of the nine did not feel anything; the other six felt the tingling. Three of the six felt enough tingling to prefer to intermittently stop the pump. Over a three- to four-week time period those sensations reduced to the point that turning the pump off while donning was no longer necessary. The other three who felt tingling seemed to see no need to stop the sensation. In their case the sensory input they felt also decreased in intensity over several weeks.
There is no clear definition of the type of sensation any individual experiences. Some amputees have described the feeling as similar to a leg "waking up" after having sat in one position too long. One patient described the sensation as bumping into his "funny-bone." It is obvious each individual will have unique sensory perceptions when exposed to this technique. The amputee should be informed of the possible sensations to be experienced.
Discussion
Vacuum-donning has proven to be a successful method of obtaining a total contact suction fitting. The amputee who initially used this procedure was classified as a nonprosthetic candidate by her rehabilitation physician. Her effort in conjunction with a suction suspension prosthesis she could don herself allowed this individual to be reclassified from a category "0" activity level to a category "2" activity level on the HCPCS medicare scale.
Practitioner use in transparent diagnostic socket fittings reduces amputee discomfort and residual limb stress due to repeated donning with pull socks. It also simplifies the donning process for other allied health care providers such as prosthetic assistants, physical therapists, nurses or home care providers. More amputees are able to experience greater independence. This increased independence, however, comes at the expense of increased problems for the amputee. For example, losing suction in a crowd can be embarrassing as well as dangerous for an amputee and repeated excessive use of lotion as a lubricant for donning requires additional prosthetic cleansing.
Further research of this technique is warranted in continued use with transfemoral prosthetic applications. Studies could also delve into such matters as remote valve locations for suction suspension, redesigned valves, a portable vacuum-donning device and vacuum-donning for suction suspension transhumeral prostheses.
Conclusion
It is possible for a lotion-lubricated transfemoral residual limb to achieve total contact within a suction suspension interface by utilizing a vacuum-donning procedure. The ease and simplicity of a vacuum-donning method will enable a larger percentage of amputees to experience the benefits associated with suction suspension. As a tool for the prosthetist, vacuum-donning brings objectivity and repeatability to the donning process. As a tool for the amputee, vacuum-donning allowsmore widespread use of suction-suspension fittings. This will assist the prosthetist in her/his practice and ultimately the amputees in their rehabilitation.
References:
- Schuch CM. Chapter 20B, Prosthetic management atlas of limb prosthetics: surgical, prosthetic and rehabilitation principles. In: 1992 Mosby Year Book. American Academy of Orthopaedic Surgeons, 529.
- Eberhart HD, McKennon JC. Chapter 20, Human limbs and their substitutes. In: Suction-socket suspension of the above-knee prosthesis. New York: McGraw-Hill, 1954, 653.
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