Supracondylar Suspension and a Single-Loop Harness for Below-Elbow Amputees

Robin Cooper, L.B.I.S.T. D. W. Lamb, F.R.C.S. J. Noble, F.R.C.S. Helen J. Scott, S.R.O.T.


A Rare Occasion

In the 12 years of its existence, the Inter-Clinic Information Bulletin has frequently carried individual articles by overseas authors. However, only once or twice before has virtually an entire issue been devoted to clinical material contributed from outside North America. The occurrence of this unusual event in the current issue, which includes articles from Scotland, Poland, China, and France, is worthy of notice.

-Editor

 

In many Western countries it has been standard practice to fit the prosthesis for a below-elbow amputee with a figure-eight webbing harness. A section of this harness, the control attachment strap (CAS), runs inferolaterally to operate a terminal device which may be either a hook or a hand. Although it provides a firm and stable fitting, this method of harnessing has the disadvantage of being cumbersome and restrictive, especially under warm conditions. Also, it is quite a complicated piece of apparatus for a child to don correctly and easily. Alternatives such as sockets of the Münster type which do not require suspension, or corset- (leather cuff) suspension systems have similar drawbacks. Moreover, maintaining a close-fitting (i.e., total-contact) socket of any type is a continuing problem in growing children. If sockets are fitted too loosely pistoning may occur, and corsets may have to be uncomfortably tight to prevent slipping. To surmount some of these difficulties, an arm-band suspension system with a single loop harness has been developed at this Centre (Fig. 1 ). Its construction is described and its clinical use in 40 patients is discussed.

The Cuff-Suspension, Single-Loop Harness

The arm band is of elastic webbing to one end of which a metal loop is stitched. Velcro attached to the other end forms an arm band when fastened through the metal loop (Fig. 2 ). Most patients prefer this fastening to be on the posterolateral aspect, thereby avoiding the biceps tendon. This band should fit fairly snugly around the supracondylar region. The side suspension straps which are also of elastic webbing connect the arm band to the socket. They are located to pass over the medial and lateral condyles. The critical lengths of these straps are determined by donning the arm band with the elbow flexed at 90 deg. The links are then fastened to the medial and lateral anchor points (chapes) on the socket with just enough tension so that, when the elbow is extended, tension is increased thus holding the prosthesis firmly in contact with the stump. Pistoning or slipping is thereby avoided when traction is applied to the prosthesis. In essence, tension on the arm band is increased in proportion to the applied load.

As shown in Fig. 1 , the shoulder loop is quite small and is attached to a harness ring located at the inferomedial aspect of the opposite scapula. A single section of webbing runs from the ring on a line one to three inches below the inferior angle of the other scapula. It connects to a cable which continues to the terminal device via a guide loop or tunnel on the medial socket wall. This cable may be disconnected so that the arm can be worn without the operating loop if desired. In the experience of this Centre the lower position of the CAS and cable (as compared to a figure-eight harness) has not presented any problems.

The Patients

The patients fitted were not specifically chosen but were merely offered this suspension apparatus as an alternative type of fitting when they attended the Amputee Clinic. The 40 patients for whom this method of suspension has now been used are indicated in Table 1 .

Patients over ten but under eighteen years of age were classified as juveniles. Over the last three years, 31 of these suspension systems have been issued to 17 children. During the past year, a majority of the pre-school-age children with a unilateral congenital below-elbow absence attending this hospital have been so fitted.

Causes of amputation in the patients fitted are shown in Table 2 .

The age at which this suspension apparatus was fitted is shown in Fig. 3 . Only two children were provided with this type of harness as a primary prosthetic fitting. All other patients had been fitted with some other suspension system previously.

Eighteen of the 25 children with congenital deficiencies had been wearing some type of prosthesis since they were less than one year of age. Of these children all but two are consistent full-time prosthesis wearers. No patient has requested a conversion back to the standard type of harness. Only three of the 18 adults are not now in gainful employment, and there have been no problems with those patients engaged in heavy work. Only one patient discarded this type of suspension and opted for a corset (cuff) type of limb. This patient underwent amputation following a burn to the left hand sustained under felonious circumstances and there have subsequently been severe psychological problems.

The duration of follow-up after the fitting of this type of suspension is shown in Table 3 .

This type of harness and suspension has proved satisfactory and effective even in those children with very short stumps, which has not been our experience or that of others1,2 with the Münster type of appliance. The older children in the preschool group now find it easier to put on their prostheses by themselves as there are fewer straps to confuse them. Previously all children in this age group required help in putting on their prostheses. Moreover, anyone not familiar with the prosthesis or harness should be able to deduce easily how to put this simple suspension onto a child. This consideration might be important when a child was away from home and could thus help preserve his normal wearing pattern.

Complications and Problems

  • Some patients experience difficulty with the change in operating cord angle although most find terminal-device operation easier. Twenty-nine patients use their terminal devices constantly. Eleven do not, and some of these never use them at all. However, it is encouraging to find that all but two of the children employ their terminal devices skillfully. These two children are both congenital amputees whose referral for primary prosthetic fitting was late.
  • The commonest problem, experienced with 15 cases, was excessive wear on the suspension link at its junction with the chape rings. Many of these arm bands are now reinforced with a thin leather strip at this point. We are also experimenting with procedures for fitting the suspension links directly into pockets in the sockets. To date this modification has been tried successfully in three patients.
  • Slight bruising anteriorly just above the elbow was in most cases resolved by trimming the socket edge and profiling the inferior edge of the arm band.
  • Two patients found that the shoulder loop was too loose and slipped off their shoulder. This problem may be overcome by simply tightening the loop or by attaching a safety pin to the clothing in the shoulder area with the strapping free to run within the loop of the pin. Alternatively a ribbon can be stitched into the clothing and looped around the strapping.
  • Only one patient experienced any discomfort from constriction by the arm band although in the early postfitting phase it is as well to review these patients at quite regular intervals to check up on this possibility.
  • This type of fitting is not of value for patients whose distal humerus has a poor supracondylar flare, or who have much adipose tissue in the elbow region.

Conclusions

  1. This method of suspension has proved less restrictive to elbow motion than the Münster or other types of fitting.
  2. Accuracy of socket fitting is not so critical with this type of suspension and thus it lends itself to use with children.
  3. The cuff is fitted under tension and stops pistoning. However, it does not need to be applied as tightly as a leather corset (cuff) because of the use of elastic materials. Constriction by the cuff has therefore been a rare problem.
  4. The avoidance of strapping both shoulders leads to greater freedom and comfort which is of advantage to the adult in hot weather, while its simplicity is of particular value for young children.
  5. There have been no special problems in teaching the children or their parents how to use this type of fitting and all children have quickly adapted to the harness and were able to operate and use their split hooks as well as before.
  6. This method of harnessing does not present any particular problem to the man whose work involves heavy lifting.
  7. Finally, we suggest that this harness offers definite advantages in the overall management of below-elbow amputees and should be given careful consideration in future harness prescriptions.

Acknowledgments

Thanks are expressed to Hugh Steeper Ltd. in whose workshop the work described in this paper was carried out. The assistance of the Medical Photography Department at the Princess Margaret Rose Hospital and of Mrs. A. McNeill at the Medical Illustration Department, University of Edinburgh, in the preparation of the illustrations is also gratefully acknowledged.

Princess Margaret Rose Orthopaedic Hospital Fairmilehead, Edinburgh, Scotland

References:
1. Friedmann, L., Should the Munster below-elbow prosthesis be prescribed for children? Inter-Clin. INform. Bull., 11:7:7-15, April 1972.
2. Gorton, Ann, The "Muenster-type" below-elbow prosthesis: A field study. Inter-Clin. Inform. Bull., 6:1:12-18, October 1966.