An Above-Elbow Suction Socket
J. A. Pentland, C.P.O.
Albert Wasilieff, C.P.O.
The suction socket described in this report for above-elbow amputees (Fig. 1 ) was first brought to the attention of the senior author in the early 1950's by Ray Trautman and Sons. Since then we have used this type of fitting in our area with very satisfactory results. From 1956 through May 1972, suction sockets for 45 above-elbow amputees were fitted by our facility. To check the long-term efficacy of the suction-socket fittings, 25 of these patients, selected at random, were surveyed in mid-1972. Sixteen of the 25, or 64 percent, were full-time wearers. Six of those who were not using their prosthesis had worn them for many years; two for 6 years, one for 12 years, one for 13 years, and two for 16 years.
We find that the suction-socket above-elbow arm can be handled with greater ease and dexterity because the intimate fit and negative pressure provides sensory information that resuits in an immediate response by the humerus. For the very-short, above-elbow stump the provision of negative pressure is essential if we expect to achieve any success in use of the prosthesis.
The principle of the prosthesis we are about to describe is, of course, not new. It simply involves taking the concept of negative pressure as we know it in the fitting of above-knee suction sockets and applying this principle to above-elbow prostheses.
Measurements of the stump are taken in the usual manner as .to length, and circumferences at 2-in. intervals from axilla to distal end. The anteroposterior and mediolateral diameters of the stump just above the level of the axilla are also recorded (Fig. 2 & Fig. 3 ). When the stump is fleshy, the tissue is compressed to provide firm resistance between the thumb and the other fingers when the calipers are applied to obtain these measurements.
When taking the cast of the stump, the plaster-wrap is extended well above the shoulder and beyond the acromion to include the anterior and posterior areas at the level of the axilla (Fig. 4 ).
In preparing the master mold after the wrap cast is filled with plaster, the circumferences of soft-tissue areas on the cast are reduced in much the same manner as would be done in modifying the cast for an above-knee suction socket, e.g.:
The anteroposterior diameter of the cast above the axilla line is also reduced to the measurement taken with the flesh under compression to insure intimate fit in this area. A posterior extension, or scapula wing, is provided to control external rotation of the prosthesis (Fig. 5 ).
After the cast has been modified, a plaster-wrap check socket is made. A balloon is pulled over the master mold before the wrap is applied so that the test socket will have a glass-smooth inner surface for trial fitting (Fig. 6 ).
Application Of The Check Socket
The check socket is removed from the cast by blowing it off with an air gun, and it is then dried in an oven. After the very distal end has been cut off, the check socket is applied to the stump by using a 2-in. diameter stockinette or tubular gauze (Fig. 7 ). On longer stumps the sock should not extend all the way up to the axilla, because to do so will result in excessive elongation of the stump musculature with consequent jamming of tissue at the distal end of the socket and interfere with removal of the pull sock.
To test the accuracy of the fit with the check socket, the patient should be asked to contract his stump muscles. If the fit is correct, it should not be possible to pull the socket off during contraction (Fig. 8 ), but it should be possible to remove it with relative ease when the stump muscles are relaxed.
When a comfortable, intimately fitting test socket has been achieved, a definitive total-contact plastic laminate suction socket is made in the usual manner. We typically use three layers of 1/2-oz. dacron felt and two layers of stockinette, and impregnate them with a mixture of 70 percent rigid-30 percent flexible polyester resin.
The suction-socket valve2 (Fig. 9 ) used is 1-1/8 in. (approx. 2.86 cm) in diameter, a size which permits easy application of a pull sock. The valve is installed in an anteromedial location at the distal end of the socket (Fig. 10 ) for convenience of the wearer. With long above-elbow stumps, care must be exercised to avoid placing the valve in any manner that would cause interference with full forearm flexion.
A minimal figure-8-dual-control harness (Fig. 11 ) is used because little or no suspension is required of the harness, it being used almost solely for operation of the elbow and terminal device. We typically use a 1-in. wide nylon elastic lateral support strap to provide additional socket control, but this is probably not essential for medium and long stumps.
The prosthesis has had excellent amputee acceptance. Few fitted this way will consider reverting to a conventional prosthesis.
The advantages of the suction-socket above-elbow prosthesis seem to be:
- Suspension is vastly improved, making the appliance feel lighter as well as making it easier to control.
- The intimate stump-socket fit provides improved proprioception and greater functional efficiency with less expenditure of energy. The amputee has a feeling that the prosthesis is more a part of him than is the case in a conventional fitting.
- Less harness is required, thus allowing more freedom for normal arm and shoulder motions.
- The biceps and triceps muscles are used actively, thus stimulating circulation and leading ultimately to a healthier and less painful stump.
- Elongation of the stump musculature reduces tension in the distal tissues, thus providing relief for humeral bone spurs and adherent scar tissue.
The suction-socket above-elbow prosthesis has relatively few disadvantages, but it cannot be used for:
- Bilateral amputees who are unable to pull their stumps into the sockets.
- Nerve-damaged stumps with little or no control.
- Edematous, bulbous, or pear-shaped stumps.
- Cases with excessive retraction of the biceps muscle.
2 We originally bought these valves from Ray Trautman and Sons, but, since they discontinued making them some years ago, we have been making our own.