Failure of Formation of Parts: Transverse Arrest (Continued)

Ulnar Deficiency. Longitudinal deformities of the ulnar ray (see Plate 4-47) are sporadic and nonhereditary and are among the rarest congenital anomalies of the upper limb. Ulnar ray defects are frequently associated with malformations of the radial ray (most common) or of the central rays as well. Associated deformities in the shoulder girdle, proximal humerus, or both, may also be present. (Involvement of a part proximal to the principal deformity occurs only in ulnar deficiencies, phocomelia, and Poland syndrome.) Malformations at the level of the elbow, wrist, hand, and digits vary greatly in type and severity. They include radiohumeral dislocation or synostosis, hypoplasia, partial or total absence of the ulna, curvature of the radius, ulnar deviation of the hand, fusion of carpal bones, congenital amputation at the wrist, and oligodactyly with or without syndactyly. In addition, there is a high incidence of associated anomalies in the opposite hand, lower limb, and other parts of the musculoskeletal system.

Management of ulnar ray defects is complex. Functional testing of limb position, power, and stability helps to determine the best treatment. In general, surgical treatment is reserved for the hand anomalies associated with ulnar deficiencies. Function can be improved with surgical release of syndactyly, web deepening, and thumb reconstruction or pollicization. Wrist and forearm operations are less successful. Occasionally, in partial ulnar defects with significant instability of the elbow, the ulnar remnant can be fused to the radius to provide stability.

Fibular Deficiency. Total fibular deficiency is one of the most common long bone deficiencies and is bilateral in about 25% of patients. In patients with unilateral defects, the limb-length discrepancy is considerable. The lower part of the leg bows anteriorly, with a depressed dimple at its apex. The foot is in valgus position, because there is no ankle mortise. There are usually only three or four toes, and the distal tibial epiphysis is absent or minimal. Treatment consists of an ankle disarticulation amputation and use of an end-bearing ankle prosthesis.

Partial fibular deficiencies are quite rare. The tibia is only minimally shortened and the fibula is either shortened or its distal portion appears normal. Treatment is with a shoe lift, but surgical epiphyseal stapling to arrest growth may be necessary.

Central Ray Deficiency. Deficiencies also occur in the second, third, or fourth ray of the hand—the so-called central rays—which do not differentiate at the same time as the radial and ulnar rays.

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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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