Failure of Formation of Parts: Transverse Arrest (Continued)

If a prosthesis is used, the length of the stump and the patient’s age determine the type of prosthesis. The infant with a very short below-elbow stump is fitted with a preflexed arm. As the skeleton matures, the child can wear a preflexed socket with rigid elbow hinges. Children younger than age 10 months are fitted with a passive mitten (smooth, stuffed plastic prosthesis) or, preferably, with a hook that is not connected to a cable system. The hook is activated when the child is ready for training, which is usually near 24 months. Newer, myoelectric prosthesis can be fitted and used as the patient ages.

Elbow Disarticulation Type. The epiphysis of the distal humerus is present, but there are no bony elements distal to it. A standard elbow disarticulation prosthesis is prescribed for this type of defect. The dual-control prosthesis has a prehensile hook and an elbow lock that allows variable positioning of the forearm.

Above-Elbow Amputation Type. In this type of defect, the epiphysis of the distal humerus is absent and the standard above-elbow prosthesis is usually appropriate (see Plate 4-42). A turntable above the elbow lock allows manual rotation of the forearm piece, providing optimal function.

Shoulder Disarticulation Type. Total absence of an upper limb deprives patients of half of their prehensile power. Children with bilateral deficits present with a formidable rehabilitation challenge (see Plate 4-43). These children usually develop compensatory skills at a very early age and they frequently become very adept at using their feet for prehension (see Plate 4-38). Most patients request prostheses for the upper limbs to broaden their prehensile skills and provide a more acceptable appearance. Because motors are necessary to control the prosthetic shoulder, elbow, and terminal device, fitting these patients is extremely difficult. Fitting prostheses for lower-level amputations is much simpler.

Children with a unilateral shoulder defect should begin wearing a body-powered shoulder disarticulation prosthesis during the third or fourth year. In bilateral amputations, the complexity of the harness and body movements necessary to accomplish simple tasks make the shoulder disarticulation prosthesis impractical. Therefore, patients with bilateral defects are ideal candidates for electrically powered prostheses. The prosthesis can be programmed with a feeding pattern that even a 4-year-old child can learn to use. The prosthesis on one side is programmed for use in the head and neck area and one on the other side for use at a greater distance, such as in toilet care. However, even children who have been fitted with these devices continue to use their feet for most activities.

Ankle Disarticulation Type. This is a sporadic, nonhereditary, and usually unilateral deficit. The stump is similar to a Syme amputation. The epiphyses of the distal tibia and fibula are present and the limb is weight bearing, but because the talus and calcaneus are absent, it is shorter than the normal one. Use of a standard below-knee socket with a solid ankle-cushioned heel (SACH) foot compensates for the difference in length.

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Jul 3, 2016 | Posted by in MUSCULOSKELETAL MEDICINE | Comments Off on Failure of Formation of Parts: Transverse Arrest (Continued)

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