Stability Within the Socket Creates Stable World

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By Robert Gailey, PhD, PT

Illustrations by Frank Angulo
Illustrations reproduced with permission from Advanced Rehabilitation Therapy Inc., Miami, Florida

Much has been written and discussed about establishing stability in the socket by means of surgery with either myoplasty or myodesis procedures, in which the muscles are stabilized by suturing muscle to muscle or muscle to bone. In addition to creating stability anatomically, prosthetic socket designs have been focused on maintaining bony alignment and placing the residual muscle in a functionally optimal position to facilitate a maximal contraction to aid the amputee with everyday activities and prosthetic control.

While the actual benefits of surgical procedures and socket designs are frequently debated, most authorities concede that a sound surgery and well-constructed socket will be of some advantage to the amputee. However, both surgery and socket design are passive measures. Regardless of the proficiency of the surgeon and prosthetist, unless the amputee learns to effectively utilize the muscle within the socket dynamically, benefits from surgery and socket design will be of little avail.

Stability within the socket is essential to quality performance. Stability requires not only strength, but also the ability to control movement in all directions and at varying speeds. Achieving the capability to utilize the remaining muscles within the socket to control forces placed on the prosthetic limb from any direction will assist tremendously in activities requiring speed, power, and agility. A training program designed to improve stability within the socket should focus on joint proprioception, in which the speed of contraction--not the maximal force of the contraction--becomes the emphasis of the exercises.

The following selected exercises, with instructions for the amputee, are designed to build both strength and power in multiple directions in a low-impact fashion, thus reducing the stress to the residual limb and the chance of injury. When these exercises are incorporated into a training program, amputees of any functional level will realize benefits in their overall ability. Moreover, multidirectional exercises allow the amputee to derive maximal benefits from the surgical procedure and socket design.

Side Walking

Side walking is performed to help learn the movement strategies necessary for walking in different directions. Simply move sideways for a predetermined distance, picking up speed as the movement becomes easier. The use of walking aids, such as canes, crutches, and walkers, is acceptable.

Crossing one leg in front of the other also helps in learning movement strategies in multiple directions. Additionally, these patterns of movement can assist in fall prevention as you learn to quickly move one leg in front of the other and return to the starting position. Moving one leg behind the other is more difficult, but has the same benefits of the previous exercises. Care must be given not to bump the prosthetic knee with the sound limb, which will cause it to collapse. Maintaining a backward force within the socket with hip musculature will help to maintain stability. Once each individual movement is learned, braiding or placing one leg in front of the other and then behind the leg during the subsequent step, may be practiced. Becoming comfortable with this skill will allow for movements in any direction with confidence.

To improve balance and assist with improved trunk rotation during straightforward walking, perform braiding with trunk rotation, in which the trunk moves in opposition to the pelvic motion. Repeat this pattern several times and then walk in a straight line. You will notice that trunk rotation during walking is now easier. As coordination and skill begin to improve, increase your speed during the braiding exercises. This sequence will assist tremendously in improving your prosthetic control in multiple directions and on different terrains.

Cup Walking Introduction

Cup walking exercises have been extremely beneficial in helping amputees learn to control their prosthesis. Cup walking is one of the more challenging--yet worthwhile--exercises that can be performed.

Place five to ten plastic cups approximately 12 to 18 inches apart. Starting at one end of the row of cups, slowly raise the leg when stepping forward so that the knee is waist high, or so that a 90-degree angle is formed at the hip, and then slowly return the foot to the floor as you step over the cup. Paper cups are also a good choice to use instead of plastic, since they crush more easily if stepped on.

There are three key elements to focus on when balancing over the prosthetic limb as you advance the sound limb. First, contract the muscles within the socket by tightening the buttocks and thigh muscles on the prosthetic side only. Second, exert a downward force through the socket. In other words, imagine that you are pushing your prosthetic foot down through the floor. Third, feel the weight of your body pass over your prosthetic foot, attempting to maintain weight over the great toe of the prosthetic foot.

One of the major benefits of this exercise is the heightened awareness of the prosthetic foot. Feeling the bodyweight over the foot and learning how to control your balance over the foot will enhance your prosthetic control in a variety of activities. Don't get frustrated. This can be a difficult exercise.

As stated earlier, multidirectional movements are extremely important when attempting to strengthen all the muscles around the hip. Performing each of the Cup Walking activities promotes different movement strategies while concentrating on other groups of muscles. To achieve success with the prosthetic single-limb balance necessary for this exercise, you must focus on the three key elements: muscle contractions within the socket, weight down through the socket, and feeling the weight progress over the prosthetic foot. Taking your time and slowly advancing through the cups will produce the greatest benefits from this exercise.

Backward walking is another skill that will assist in developing prosthetic control. Focus on the same key elements, contracting the muscles, exerting a downward and backward force within the socket. Additionally, limiting any unnecessary movement from the trunk will help.

There are a number of variations that can be introduced into the cup walking exercises. For instance, walking on a compliant or foam surface increases the need for stability within the socket in order to execute the exercise exactly the same way as it is performed on a solid floor. The foam creates the need to maintain knee stability in all directions and therefore, requires the muscles of the knee and hip to react faster in order to maintain balance.

To further challenge the prosthetic limb musculature and to improve balance, sideways walking will facilitate the use of different muscle groups. With side walking, it is important to contract the muscles about the buttocks as well as the thigh muscles.

The Functional Training Series for Transfemoral and Transtibial Amputees video and book series can assist clinicians and amputees in learning more about these exercises and many others.

Robert Gailey, PhD, PT, has specialized in the rehabilitation of lower-extremity amputees for about 20 years. He has done extensive research, writing, and lecturing. In addition to teaching at the University of Miami, Florida, he also operates Advanced Rehabilitation Clinical Services and Seminars in Miami (www.advancedrehabtherapy.com).

University of Miami School of Medicine Department of Orthopaedics Division of Physical Therapy