Experiences in the Use of a Pneumatic Stump Shrinker
J. B. REDFORD, M.D. - University of Alberta Hospital Edmonton, Alberta, Canada
After amputation surgery edema of the stump is a universal problem. The sooner it can be eliminated the better, as prosthetic fit depends on close contact between the socket and the functioning muscle tissue remaining in the stump, and close contouring in the weight-bearing areas. Stump edema also contributes to postoperative pain. Observations in cases where a rigid dressing is applied immediately after amputation show that when edema and the associated inflammatory exudate is controlled, pain is minimal.
In spite of the importance of eliminating edema in amputation stumps, very little has been written concerning the quickest and best means of doing so. Wrapping the stump with elasticized bandages has been routinely done in most centers. These bandages are effective when used properly. However, their use presents difficulties; especially if the patient is expected to wrap his own stump or if the nurse or others applying the bandages are poorly trained.
The purpose of this paper is to describe the methods at our center to reduce stump edema, particularly through the application of the Jobst intermittent compression unit (Jobst Institute, Inc., Box 653, Toledo, OH 43601).
Mechanisms of Edema
A basic cause of edema is a change in the capillary filtration pressure, i.e., edema occurs when factors controlling the equilibrium between intra- and extravascular fluids are disturbed. The main factors involved in this equilibrium are blood pressure, osmotic pressure and hydrostatic pressures in the capillary bed.
Fig. 1 illustrates pressures at the atrial level in the recumbency. Pressure at the arterial end of the capillary loop is 30 mm Hg which decreases to 15 or 16 mm Hg at the venous end as blood flows through the loop. This intravascular pressure is opposed by osmotic and hydrostatic pressures which are the same at both ends of the capillary loop. However, at the arterial end the blood pressure exceeds the combined osmotic and hydrostatic fluid pressure so fluid leaves the capillary. At the venous end the reverse is true and fluid enters the capillary. Fluid not absorbed in this manner becomes lymph and is returned to the circulation through the lymph channels3.
Increasing Venous Return
Normal systemic arterial pressure must be more than doubled (300 mm Hg or more) to increase the normal passage of filtrate through the vessel wall at the arterial end of the capillary loop. In contrast to this, an increased pressure of only 2 to 3 mm Hg at the venous end of the capillary loop will interfere with the normal reabsorption of the filtrate and cause local edema. The extravascular hydrostatic pressure produced by tension exerted in the adjacent tissues limits the extent of this extravasation. External support is a means of maintaining this tension. Therefore, to reduce edema it is logical to wrap extremities with elastic bandages or to apply devices that increase the hydrostatic pressure in tissues.
The importance of the contracting muscle or "muscle pump" in increasing the venous return from the limb varies according to the anatomy of the region. Only in those muscles with rigid vascular compartments such as the anterior leg muscles does the contraction of the muscle per se appear very important in increasing venous return. The important factor promoting venous return is the relative rigidity of the tissue. When the fascia surrounding the muscle is rigid, this rigidity increases tissue tension and venous return6. This latter observation suggests that the more rigid the material surrounding an edematous limb the better the trussing and, thus, the better the venous return. This view is also supported by a principle of physics stating that any deformation of a cylinder with a nonexpandable pliable wall will result in some loss of volume. Thus, in an amputation stump covered with a nonstretchable mold, any deformation from muscle contraction will reduce stump volume and edema4.
These principles have been applied in the successful control of postoperative stump edema using rigid plaster dressings2. It would appear that the best method of reducing stump edema yet developed is the correct application of plaster dressings with careful attention to changing them as the stump shrinks. Unfortunately, rigid plaster molds do have some drawbacks. The special technical help needed to apply them may not be generally available. The mold does not contract with stump shrinkage and must be reapplied to take up the slack. Moreover, when the mold is left on, the stump cannot be examined readily. The problem of handling drainage from the stump of fluid exudate that may serve as a medium for bacterial growth and infection is another negative factor.
Ideally, for stump wrapping, we need a porous, nonsensitizing, nonstretchable mold, preferably transparent and adjustable, that can be applied by the patient and be generally acceptable as to cost. In the absence of such an ideal material we are using a number of approaches to control stump edema, including:
- Rigid plaster dressings and walking with hard temporary sockets as soon as possible after amputation.
- Wrapping with elastic bandages and elevation of the stumps.
- Intermittent mechanical compression of the stump using Jobst pneumatic pump apparatus1.
- Custom-made stump stockings of elastic material.
Intermittent Pressure Devices
As rigid dressings, temporary prostheses and elastic-bandage wraps are familiar to everyone working in the field of prosthetics. Only the use of intermittent compression devices and custom-made elastic stump stockings will be described here.
The Jobst intermittent compression unit consists of pneumatic sleeves of various shapes and sizes that can be applied around limbs or over amputation stumps, and an air-compressor pump which is used to inflate these sleeves. The pneumatic cuffs can be inflated and deflated in a timed cycle. Pressures in the cuffs vary from 0 to 300 mm Hg (Fig. 2 ).
We have used this pump on amputees whose stumps are well healed and show no signs of skin infection. It has been applied mainly to reduce edema just prior to casting the amputation stump for a temporary or a permanent socket. Other uses have been in cases of persistent edema where stump wrapping appears ineffective or where a rigid cast cannot be tolerated because of skin condition or some other problem.
The degree of pressure and its duration of application to the stump vary with the individual's tolerance. Studies have shown that a pneumatic cuff encircling a human limb applying 20 to 35 mm Hg pressure will increase the velocity of venous flow by decreasing the total cross-sectional area of the venous bed5. Increasing the external pressure above 35 mm Hg did not further increase the velocity of flow. Therefore, it seems unnecessary from the physiological standpoint to raise the pressure much above 35 mm Hg, although we have generally used values ranging up to 50 or 60 mm Hg. If pressures much above this level are used, we have noted an increase rather than a decrease in the circumference of the stump after treatment.
The following is a method that we are using for our application of pneumatic cuffs to the lower-limb amputee:
- The stump is elevated by having the patient lie on a table one end of which is raised 14 in. The patient should be in a comfortable position with his head on a pillow: simply elevating the stump on a pillow is neither effective nor comfortable.
- We apply a stockinette over the stump; then the pneumatic appliance. The unit is then turned on to operate continuously, with the timer set to the desired pressure cycle.
- Standard starting pressures and times: with below-elbow, above-elbow and below-knee amputees, 40 mm Hg at a 1 to 2 cycle ratio; that is, 20 seconds off and 40 seconds on. This sequential compression and release is applied for one hour in the morning and one hour in the afternoon. Almost all stumps, two weeks after surgery, are able to tolerate pressures of 35 mm Hg at the same time ratio. In some patients pressure is increased as tolerated up to 60 or 70 mm Hg especially with flabby above-knee stumps. The circumference at three or four levels of the amputation stump is measured before and after treatment every day or every other day. After the pressure application, the stumps are immediately wrapped in tensor bandages using a 4-in. width for the below-knee and 6 in. for the above-knee. Stumps are kept wrapped continuously when the patient is not using the Jobst unit.
The patients who have been fitted with an immediate postsurgical prosthesis are able to tolerate much more pressure with better results in shaping the stump than those who have not been so fitted. In some cases prior to casting for a permanent prosthesis, pressure in the Jobst unit is held at a constant level between 60 to 80 mm Hg for 30 minutes. This procedure gives the limb fitter a well-shaped stump to cast. Later, if there is any difficulty in applying the new prosthesis, the Jobst unit can be used in the same way to reduce stump size, thus avoiding skin damage and discomfort to the patient.
For the above-knee stump, the pneumatic appliances that are commercially available at present do not have a good method of suspension or the proper shape, and tend to slide off the stump. This is because the top is not quadrilateral in shape and pressure cannot be applied in the adductor area or proximally over the lateral side of the stump where optimal shrinkage is needed. Recently we have been using a new experimental design with a quadrilateral shape and a shoulder strap with Velcro suspension to overcome these problems (Fig. 3 ). Early experience suggests that this will be a much better pneumatic stump-shrinking cuff for the above-knee amputee.
Elastic Stump Shrinkers
We have tried various types of commercially made supports as substitute for the tensor bandages. However, unless these commercial items are custom-fitted, they are not very effective. Furthermore, as the stump often shrinks rapidly, new custom-fitted stump shrinkers may be required every week or two. We have designed a simple stump shrinker using the synthetic fabric "Lycra" as a less expensive substitute for the elastic materials in commercial stump shrinkers (Fig. 4 ). A tracing of the stump shape is made directly on the material. The edges are then sewn and can be taken in and resewn every day or every other day if the need arises as the stump shrinks. The Lycra shrinker can be held on by a garter belt. These shrinkers can be used directly on the stump or in some cases, particularly when the stump shrinks rapidly, we apply them over the top of the elastic plaster bandage wrap to increase external pressure. In addition to these supports, we have successfully used Tubigrip in appropriate lengths with one end sewn to hold the distal stump (Tubgrip: Seton Products Ltd., Oldham, Lancashire, England. Also available in the United States at SPS, 947 Juniper St., N.E. Atlanta, GA 30309, and Orthopedic Equipment Co., Bourbon, IN 46504.).
The ways of reducing edema discussed above pertain to mechanical methods; we also occasionally use diuretics such as hydrochlorothiazide to reduce persistent edema, especially if the patient is known to have a heart condition. As infection contributes to stump edema, one should always search for and treat it appropriately. Some stumps may appear to have no signs of infection but, in probing along the suture line, one may find a small infected area, or an x-ray or sinogram may show that some type of subclinical infection exists. Only when such infection is cleared up will the edema be reduced.
Methods used routinely in our amputee clinic to reduce edema have been described. The ideal type of wrapping has not yet been developed, but we are very satisfied with rigid-plaster dressings supplemented by intermittent compression devices. We also use tensor bandage wrapping and custom-made stump socks of Lycra and Tubigrip. As cases have great individual variations, meaningful statistics concerning the effectiveness of these various methods cannot be given. In cases where no complications develop, we are able to reduce the edema following immediate postoperative fitting so that the patient can be fitted with a permanent prosthesis in 40 to 60 days.
- Brush, B. E., J. H. Wylie, and T, Beninson, Some devices for the management of lymphedema of the extremities Surg. Clin N. Amer., 30:6:1493-1498, December 1959.
- Burgess, E.M., R.L. Romano, and J.H. Zettl, The Management of Lower-Extremity Amputations. Prosthetic and Sensory Aids Service, Dept. of Medicine and Surgery, Veterans Administration, TR 10-6, August 1969.
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- Lippman, H.I., and J.P. Briere, Physical basis of externam supports in chronic venous insufficiency. Arch. Phys. Med. & Rehab., 52:12:555-559, December 1971.
- Stanton, J.R., E.D. Freis, and J. Wilkins, Acceleration of linear flow in deep veins of the lower extremity in man by compression. J. Clin. Invest., 28:553-558, May 1949.
- Wells, H.S., J.B. Youmans, and C. Miller, Tissue pressure as related to venous pressure, capillary, filtration and other factors. J. Clin. Invest., 17:489-499, July 1938.