Hip Disarticulation Prosthesis for Infants: Case Report


In 1987, a 9-month-old boy with a total amelia of the lower right limb was presented at the British Columbia's Children's Hospital in Vancouver, British Columbia, Canada. At the time, he was "pulling to stand", and it was decided that this would be the appropriate time to fit him with a prosthesis so he could stand bipedally and eventually ambulate with a prosthesis.

The parents were extremely concerned about the appearance of the artificial limb. They requested movable hip and knee joints to allow natural appearance when the child sat and walked. Design criteria were:

  1. Cosmetic acceptability
  2. Easy application and removal
  3. Little maintenance
  4. Easy adjustability for growth
  5. Inexpensive to repair, if necessary
  6. Stable hip and knee joints.

Nothing is available commercially for such a small child. After a plaster cast model was made a conventional hip disarticulation socket was fabricated. Acrylic resin with Perlon and glass reinforcements was used. The socket was made to accommodate diapers for hygienic reasons. Modular-System Technique was applied, using parapodium tubing purchased from the Variety Ability Systems, Inc., Scarborough, Ontario. The hip joint was made from an ordinary strap-hinge from a hardware store. The knee joint was manufactured from a modified parapodium joint. On the lower part, the anterior side was flattened. A leaf spring was attached to the upper part of the joint with two 4.59 mm (6/32") machine screws. The screws press the leaf spring against the flattened surface, and in turn lock the knee. (Fig. 1 ) The lower screw allows for tension adjustment, and therefore the amount of stability in the knee can be controlled. The knee has to be unlocked manually by bending, and will lock automatically in full extension. A foot adaptor from United States Manufacturing Company was the connecting component for the IS30 Otto Bock SACH foot. All parts were fabricated from aluminum with the exception of the hip joint, which was steel. The final product is light weight, but sufficiently strong to support the boy's weight.

Alignment of the prosthesis is such that the weight of the patient is aligned over the middle of the foot, to balance him in a natural standing posture (Fig. 2 ). The system is held with hose clamps allowing for easy adjustment for length and rotation.

Range of hip motion from extension to maximum flexion is 120 degrees. The knee joint moves from full extension to maximum flexion of 110 degrees.

Cosmetic finishing was done in the conventional fashion, utilizing the Otto Bock 15K2 finishing kit for the modular arm system, allowing for a natural shape and feel (Fig. 3 ). Appearance was excellent, the parents were satisfied, and the child was very happy with his new "mobility". The soft finishing technique proved very cosmetic as well as saving on clothing wear and tear of clothing (Fig. 4 ).

The patient was able to:

  • balance immediately without assistance;
  • walk with some one-handed assistance;
  • sit;
  • crawl and kneel without the prosthesis being cumbersome.

Ford Laboratories, 106-11400 Bridgeport Road, Richmond, British Columbia V6X 1T2 Canada