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The Use of Opposition Posts in Children with Transmetacarpal Deficiencies

A study was performed to evaluate the response of the child to the device and its overall functional use. Physical examination results and responses to an interview concerning comfort, cosmesis, function, fit, adjustability, and acceptance or rejection of the device were evaluated.

Rejection rate of the opposition posts was very high. For optimum function, four of the patients preferred no orthotic or prosthetic devices. One uses a below-elbow, body-powered prosthesis. The remaining three use the post to varying degrees. Fit, comfort, and stability of the devices were major reasons for rejection. Further studies on fabrication designs, training methods, and criteria for prescription are needed.

Introduction

At the Erie Unit Shriners Hospitals for Crippled Children, pediatric patients with transmetacarpal deficiencies have several choices of intervention; orthotic, prosthetic, or surgical (Figure 1 ). At a young age, they are evaluated for possible fitting of an opposition post to enhance function. In the past, the posts have been fabricated by either an occupational therapist, orthotist, or prosthetist. These devices usually consisted of a polypropylene shell with an opposition pad or post incorporated into the end of the shell. Opposition splints were often made of thermoplast with velcro straps over the extensor forearm to hold the volar splint in place. Splints were very similar to the orthoses made with a full shell in respect to the post itself, though splints did not fully encase the wrist and forearm as the orthoses did (Figures 2 and 3 ).1,2,3

In prescribing opposition posts at the Erie Unit, we attempted to increase the function of a child's deficient extremity, while maintaining its sensation. Conventional prostheses with a variety of terminal devices enhance function but deprive the wearer of sensation. Because of the diversity of patients seen at the Erie Unit, maintenance of sensation is a topic often discussed among medical staff and parents. We evaluated the effectiveness of opposition posts in children with transmetacarpal deficiencies.

Materials and Methods

From 1981 to 1991, eight patients (six boys and two girls) were evaluated. The average age was eight years (range, 11 months to 20 years). Six patients had complete congenital transverse deficiencies at the wrist, two had one or more partial phalanges present. Four patients fit with the posts had prior use of prosthetic devices (Table 1 ). At the time of prescription, the average age of the children was five years. Each child underwent training for use of the device. Parents were educated in the overall program. The children were then followed in our outpatient clinic to monitor problems or the need for a new or revised device. The patients were brought back to the Shriner's hospital for an interview and physical examination shortly before the completion of this study.

Results

Three patients use opposition posts to varying degrees. Each has specific tasks that they use the opposition post for, but otherwise use another type of prosthesis or no prosthesis. One of these patients was subsequently fit with a myoelectric device that he uses intermittently with the post. (This patient worked in an auto parts store, which required him to pick up small auto parts.) Four have opted for no device on the extremity. One now used a below-elbow, body-powered, prosthesis with a voluntary closing adept terminal device. No correlation between age of original fitting or use of device was noted.

Discussion

Opposition posts have specific advantages; the patient retains sensation in the extremity and is able to utilize forearm musculature. Often, function of the extremity is enhanced and expanded. Before fitting with a post, a child will often attempt to grasp an object with the residual limb. However, to maintain the object in his grasp, he will require assistance from his sound hand or support against his body. A post allows for more two-handed activities and promotes better developmental progress. The post can be considered a true terminal device as it does not require suspension by cables or a harness. This has often been a major factor in rejection of other conventional body-powered prostheses. The function field of use or work envelope with opposition posts is greater than with conventional body-powered prostheses, allowing the post to be utilized in any position the extremity can be placed. Myoelectric devices also offer this advantage, but compromise with added weight, decreased durability, and loss of sensation to achieve this increased functional field.

Even with these advantages, posts prescribed at the Erie Unit were infrequently used. Many patients had adapted to their deficiency before post fitting and found little or no functional improvement with the device. Since close fit was necessary for stability, wearers frequently complained that posts were constrictive. Splints commonly lacked the necessary stability. Velcro straps were used unsuccessfully to secure splints in place. Often, with increased activity, migration of the post away from palmar opposing surface made utilization of the post impossible. Attempts to make the posts more stable included extending the socket proximally and utilizing a stump sock to apply the formfitting device. This, in turn, led to complaints of increased temperature and sweating of the extremity within the socket. There was some limitation of motion at the elbow joint, with loss of functional supination and pronation of the forearm. Often the child could supinate and pronate within the socket, but was unable to utilize the post, as it remained fixed. In addition to function considerations, there are psychosocial aspects to the use of a post. Some children that were already accepted by their family and peers believed the application of a post would direct more attention to their deformity. Parents felt this might be harmful, especially in the school setting. If the post did not offer significant functional improvement, it was not used. We noted very sporadic use of posts at a number of other facilities.

To improve their functional status, many patients were often presented with other alternatives. Some opted for bodypowered or myoelectric prostheses, whereas others chose no orthotic or prosthetic device. Toe transfers have also been utilized,' though we have no experience with this type of intervention. Comfort, fit, and stability of the post is presently being improved by addition of a supracondylar socket to house the opposition post. This is currently being tested on some patients originally fit with a splint.

Summary

Though a few of our patients did use the form-fitting posts, the majority found the disadvantages outweighed the advantages. Although our numbers are limited, we found opposition posts to be used as task-specific devices. In three of our patients who had used or are currently using an opposition post, specific tasks such as bike riding, weight lifting, and holding small auto parts were more readily accomplished with the post. In very young children who had no specific functional need for a post, there was little or no use. Further studies of fabrication designs, training methods, and criteria for prescription are needed.

Hamot Medical Center, 201 State Street, Erie, PA 16550 814-877-6000

References:

  1. Atlas of Limb Prosthetics. American Academy of Orthopaedic Surgeons. The C. V. Mosby Company, St. Louis, 1981, pages 560-561 and 569-570.
  2. Comprehensive Management of the Upper-Limb Amputee, D. J. Atkins and R. W. Meier II Editors, Springer-Verlag, New York, 1989, page 31.
  3. Prosthetics for the Child Amputee, Steven M. Wenna, Rehabilitation of the Hand, Hunter and Schneider, 3rd Edition, C. V. Mosby Company, St. Louis, 1990, pages 1085-1088.
  4. Operative Hands Surgery. 2nd edition. David P. Green, Churchill Livingstone, 1988, pp.1296-1309.