Children with this deformity are fitted with a below-knee prosthesis that has a plastic socket, condylar cuff, and SACH foot. In some patients, use of rigid knee joints and a leather thigh corset is necessary. The below-knee prosthesis requires little training and allows excellent function, including participation in sports.
Knee Disarticulation Type. In this deficit, the stump is symmetric without distal tapering. The entire femur, including its condyles and lower epiphysis, is present. Toddlers with unilateral defects are fitted with the simplest prosthesis so that they can learn to walk with it. The prosthesis consists of a plastic socket with two aluminum uprights that taper to a crutch tip; a SACH foot is substituted later. Initially, there is no articulated knee hinge. An over-the-shoulder harness helps to hold the prosthesis in place.
When the child is older, a knee disarticulation prosthesis is used. The knee joint is locked with an anterior strap until the child learns to stand independently in the prosthesis. When the child begins to learn thigh lifting and knee swinging, the locking strap is disengaged and later discarded. Some children can be fitted with a suction socket prosthesis as early as 5 years of age.
Above-Knee Amputation Type. In this defect, the epiphysis of the distal femur is absent (see Plate 4-44). Treatment is the same as for a knee disarticulation–type defect.
Hip Disarticulation Type. The femur is totally absent, and there is no acetabular development (see Plate 4-45). In patients with bilateral defects, pelvic contour is wide because fat accumulates over the pelvis. These patients are initially fitted with a pelvic bucket mounted on a board with casters and later with a bilateral hip disarticulation prosthesis with Canadian hip joints. Locking knee straps are used until the patient can stand alone and disengaged when training for ambulation using parallel bars begins. The upper limbs must have sufficient muscle power for these patients to lift themselves for a swing-to type of progression. Ultimately, they learn to ambulate with crutches or remain wheelchair bound.
In unilateral cases, toddlers are first fitted with the simple crutch tip prosthesis, which is later replaced with a hip disarticulation prosthesis. The prosthesis is lengthened as needed.
I. Failure of Formation of Parts: Longitudinal Arrest
All failures of formation of the limbs other than the transverse arrest type, are arbitrarily classified as longitudinal arrests. The deficiencies in this group reflect the separation of the preaxial (radial or tibial) and postaxial (ulnar or fibular) divisions in the limbs and include longitudinal failure of formation of all limb segments (phocomelia) or failure of either the radial, ulnar, or central components.
Radial Deficiency. Preaxial deformities in the upper limb may involve the radius and thumb, radius only, or thumb only. Malformations include deficient thenar muscles; short, floating thumb; deficient carpals, metacarpals, and radius; and classic radial clubhand. Radial deficiencies are often associated with other congenital anomalies and a number of syndromes such as Holt-Oram syndrome, congenital aplastic anemia (Fanconi anemia), and thrombocytopenia-absent radius (TAR). It has also been associated with maternal use of valproic acid, thalidomide, and phenobarbital and with fetal alcohol syndrome.
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