A Chest Strap Harness For The Below-Elbow Child Amputee
Barbara O'Shea, O.T. Reg.
Harness design and adjustment are among the most critical factors in the fitting of an efficient and functional upper-extremity prosthesis.
The two basic functions of a harness are:
To provide adequate suspension of the prosthesis, so that the socket is held firmly to the stump.
To provide control of the prosthesis by transmitting the power produced by body motions to the activated components.
However, when designing a harness it is not enough to be concerned only with function. Also of prime importance is comfort. Discomfort on activation of the prosthesis leads to decreased use of the controls, and if the problem is not alleviated, may cause rejection of the prosthesis.
In dealing with below-elbow juvenile amputees, we found that while the figure-eight or ring harness was efficient in providing suspension and control, children frequently complained of discomfort, primarily in the axilla of the sound side. This experience led us to experiment with various harnessing patterns in the hope of finding one that would enhance comfort without sacrificing efficiency. We believe that the design to be described fulfills these requirements.
This harness was developed by the occupational therapists at the Ontario Crippled Children's Centre, in conjunction with the Prosthetic Research and Training Unit. It is an adaptation of a heavy-duty harness sometimes used for adult below-elbow amputees. The design of the harness and the materials used were adapted for application to juvenile amputees from infancy to maturity.
In all applications of this harness to date, we have found 3/4-inch cotton webbing edged with nylon to be the most comfortable. Although its life span is not as great as dacron webbing, it usually will last until a child has outgrown the harness. The nylon edge seems to be effective in preventing stretching and fraying.
A shoulder saddle of 3/4-inch cotton webbing, which lies in the hollow of the shoulder on the amputated side and runs from below the inferior edge of the clavicle to below the spine of the scapula. This saddle must fit snugly to give adequate suspension.
A chest strap to which the shoulder saddle is fastened at both ends. It has a front opening with Velcro and ring closure. This strap can be a continuation of the shoulder saddle, with a 90-degree fold at either end where they join.
A ring of nylon parachute cord, which runs through a loop attached to the cuff and is fastened to both ends of the shoulder saddle. The cut ends of the parachute cord should be sealed with a flame to prevent fraying and then stitched securely to the webbing.
A loop of 1/2-inch dacron webbing riveted to the medial side of the triceps cuff, with the top of the loop located below the superior edge of the cuff. This loop must be large enough to allow the parachute cord to run freely through it.
A control attachment strap anchored on the back of the chest strap at the position where it offers the most efficient control. This usually tends to be around the midline or slightly toward the unamputated side. The strap is fitted with a buckle to allow adjustment as the child grows. Although changes in strap length would probably be unnecessary between clinic visits, the parents should be taught how to make this adjustment.
This harness has been in use in our clinic since October 1965. At present approximately 25 below-elbow amputees, ranging in age from five months to nine years, are wearing it.
The primary advantage seems to be the improvement in comfort achieved. The design of the harness is such that the prosthesis is suspended by the shoulder saddle and the parachute cord. The pull of the control strap is taken around the chest wall rather than upward into the soft tissues of the axilla. In all cases fitted, pressure and irritation in the axilla of the unamputated side have been relieved.
After several children had been fitted, other advantages became evident. Because the parachute cord slips freely through the dacron loop on the triceps cuff, no functional limitation of humeral flexion or extension is evident. This characteristic allows greater freedom of shoulder movement.
The stability of the harness also adds to the functional use of the prosthesis. The straps remain in position throughout the range of shoulder movements. Even with the arms over the head, limited use of the terminal device is possible. These are significant advantages, particularly with young children, who need a prosthesis which will accommodate the gross motor activity that comprises a large part of their normal play.
In the fitting of this harness, a wide variety of control attachment positions are possible. During the child's prosthetic training, the therapist can vary the position, using a Yates clamp, until the most functional and efficient placement is determined.
In our experience with harnesses of this design, we have found that children can put them on independently just as easily as those of the conventional types. The ring on the front opening must be large enough to allow easy threading of the Velcro strap.
Older children who have been changed from a figure-eight or ring-type harness have found that the shoulder on the nonamputated side can no longer be used to activate the terminal device. This lack is significant only in situations where the child has positioned his prosthetic arm for an activity and wants to grasp or release an object without altering the position of the prosthesis.
The new harness has now become the standard below-elbow harness used in the Prosthetic Clinic at the Ontario Crippled Children's Centre. We are not aware of any serious disadvantages in this design and believe that its advantages of comfort, freedom of movement, and adjustability enhance the wearing tolerance and the functional use of a prosthesis.
The design of the harness presented in this article is essentially the same as that described in "A Harness for the Unitized Arm," Eleventh Annual Report: 1965, Child Amputee Prosthetics Project, University of California, Los Angeles, pp 6-7. However, the Ontario Crippled Children's Centre harness involves the addition of a cable control system so that it may be used by a child to activate a terminal device.
The author wishes to acknowledge the assistance of Miss Nancy McKeown, 0.T. Reg., and Mr. Colin McLaurin, B.A. Sc., P. Eng., Director Prosthetic Research and Training Unit, in the development of this harness. Appreciation is also expressed to Dr. R.R. Mutrie, Medical Director, Dr. John E. Hall, Clinic Chief, and the staff of the Prosthetic Clinic for their guidance and support. I am grateful to Mr. James Grice for the illustrations and to Mr. Peter Sandiford for the photographs.
Barbara O'Shea, O.T. Reg. is associated with the Ontario Crippled Children's Centre Toronto, Ontario