Transition from a Voluntary Opening to a Voluntary Closing Terminal Device: Case Report
SHARON L. GREENBERG, MOT, OTR, BRIAN J. DUDGEON, MS, OTR, ARLENE K. LIBBY, OTRAND KENNETH M. JAFFE, MD
Voluntary opening and voluntary closing terminal devices offer distinct prosthetic options for limb-deficient children. This case report describes a boy with a transverse mid-carpal deficiency who switched from a voluntary opening to a voluntary closing terminal device (TD). He had been a full-time CAPP TD4 user, but his parents became concerned by his lack of spontaneous prehension and his difficulty with grip force.
A 7-year-old boy has a unilateral congenital limb deficiency associated with Poland's syndrome.1 His left forearm is hypoplastic; effectively it has terminal transverse midcarpal deficiency. He has no forearm rotation or wrist motion. The proximal row of carpal bones is present as is a non-functional, hypoplastic thumb. He has absence of the lower costal portion of the left pectoralis muscle and abnormal insertion of its sternal portion. This results in axillary webbing and shoulder abduction limited to 100 degrees passive range.
He was seen initially for prosthetic management at 6 months of age. Various prosthetic options were considered but, because his forearm length was adequate for stabilizing objects, no prosthesis was prescribed at that time. Specific methods to promote the use of his residual limb were suggested. At 18 months of age, a prosthesis was prescribed. It had a wrist-disarticulation socket, figure-8 harness, and a cable activated, voluntary opening CAPP TD. The parents preferred the CAPP TD because of its appearance and large grasping surface. The child received occupational therapy immediately after prosthetic fitting to encourage and increase wearing tolerance, learn control motions for cable activation, and promote prosthetic use in bilateral activities. Because the family lived far from the medical center, periodic telephone contact complemented annual return clinic visits. Both parents demonstrated interest, motivation, and creativity in prosthetic training.
At 2 1/2 years of age, he was a full-time wearer, using the prosthesis spontaneously in gross motor tasks and to assist fine activities. At the next yearly visit, the family expressed concern over his lack of spontaneous prehensile use of the prosthesis. Weak closing force of the TD was identified as a factor contributing to infrequent and ineffective prehension. The CAPP TD was fitted with a heavy-duty spring and additional activities which required bilateral prehension were suggested in hopes of improving spontaneous prehension. Other prosthetic options were suggested, but the parents were not ready to change.
By age 5 1/2 years it was very apparent that the boy needed increased grip force to use the TD for many functional activities. He and his parents were interested in investigating other prosthetic alternatives. A myoelectric TD was deemed inappropriate because of cost, the family's distance from technical support, and the long length of the child's residual limb.3,4 Although the voluntary opening hook4,8 offers grip force proportional to the number of rubber bands applied, the family disliked its appearance. They preferred the ADEPT5,6 which provides voluntary closing grip force proportional to body force applied. Members of the clinic team feared that switching from voluntary opening to voluntary closing TD control would be difficult. The manufacturer provided a free trial of the ADEPT TD which did not require any socket or control cable changes.
Within 24 hours of ADEPT fitting, the boy demonstrated graded closure and proficiency in a variety of bimanual fine motor tasks. He had no difficulties learning and adjusting to the voluntary closing concept. An immediate increase in spontaneous prehension and sustained holding was noted by the parents and the clinic team. Palmar grip strength, measured with a dynamometer, was within normal limits' at 11.8 kg on the right and 13.6 kg with the ADEPT. He used the prosthesis in a confident manner, easily grasping, holding, and releasing various sized objects.
Communication with the family in the subsequent weeks confirmed that the child had become more spontaneous in his prehensile function. When grasping an object with his terminal device, a more secure grip force seemed to reinforce his willingness to use his TD in purposeful holding. Some activities were now easier, including steering a bicycle, manipulating a wheelbarrow, crosscountry skiing, and pulling a rope hand-over-hand.
After one year of use, grip strength was 17.3 kg on the right and 29.6 kg with the ADEPT. He had 4.6 kg of palmar pinch on the right compared to 11.4 kg distal closing force with the ADEPT. The UNB Test of Prosthetics Function' was administered at the one year follow-up visit. The boy scored 34 points for spontaneity and 35 for skill of a maximum of 40 points in each category. He demonstrated an automatic tendency to use the grasp function of his TD with most tasks.
The child has used the voluntary closing ADEPT TD for over two years. Both he and his family are pleased with the functional changes. The only other TD he uses is a nonprehensile sport mitt for specific recreational activities.
The clinic team, family, and child all noted that increased prehensile force was needed for this boy to use his prosthesis more effectively. He quickly and spontaneously incorporated prosthetic prehension into self-care and play activities after changing TDs. TD grip strength also increased. The change also might have occurred with other TDs if they had provided greater grip force. Hosmer6 is now supplying stronger springs for the CAPP TD and, by adding additional rubber bands, pinch strength also can be increased with the voluntary opening hook. One advantage of a voluntary closing system is that the user does not need to overcome opening resistance prior to grasping. Another feature is that the ADEPT gives the wearer control over the amount of prehensile force exerted. The child could apply force in proportion to his prehensile requirements. This seems to provide enhanced sensory feedback, a desirable feature. Further clinical experience and study will help define the ADEPT's place in pediatric clinical practice relative to voluntary opening TDs.
Department of Rehabilitation Medicine, University of Washington and Children's Hospital and Medical Center, Post Office Box C 5371, Seattle, WA 98105.
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