Failure of Formation of Parts: Longitudinal Arrest (Continued)

Surgical treatment is very challenging and may include total or partial amputation or reduction in size. If the deformity is unsightly, amputation may be indicated. Although surgical reduction of an enlarged digit is possible, the procedure is difficult because of the need to preserve the neurovascular supply and joint function while reducing both the length and width of the digit. Reduction procedures can include epiphyseal arrest and progressive excision of bone and soft tissue.

V. Undergrowth

Undergrowth, or hypoplasia, denotes defective or incomplete development of the entire limb or its parts. In some classifications, the term hypoplasia was used to describe the condition of skeletal elements that persist after some failures of formation of parts (category I defects). However, because of their prevalence, hypoplastic defects are represented separately in the classification used here. Hypoplasia may occur in either the upper or the lower limb. In the upper limb, it may affect the arm, forearm, hand, or parts of the hand. Only the skin and nails may be involved, or the musculotendinous structures, the neurovascular structures, or both, may be affected as well.

Brachydactyly. Shortening of the digits is the most common hand malformation seen in association with syndromes and systemic disorders. It is usually transmitted as a part of an autosomal dominant phenotype with slight variation. The middle phalanges of the index through little fingers, and especially those of the index and little fingers, are most commonly affected because they develop later than the thumb. The metacarpals are involved less frequently and the deformity is rare in the distal phalanx of the thumb. Surgical lengthening of the shortened digits is usually not necessary, although osteotomy through the anomalous or proximal phalanx can sometimes correct a deviated finger.

Brachysyndactyly. Shortening of the digits plus syndactyly could be classified in category I (failure of formation of parts) or category II (failure of differentiation of parts) because some of its features are intersegmental failure of development as well as failure of separation of parts. However, the most obvious failure, hypoplasia, explains the reason for inclusion in this category.

VI. Congenital Constriction Band Syndrome

Constriction bands are the result of focal necrosis along the course of the limb during the fetal stage of development. An area of necrosis involving the superficial tissues heals as a circular scar, creating the band. Whether constriction bands are intrinsic or extrinsic defects has not yet been fully determined. Amniotic bands have been implicated as a mechanical cause but may actually be secondary to a healing limb injury. The malformation is probably caused by a focal tissue defect that allows hemorrhage within the limb, with resulting tissue necrosis. The defect can be expressed as a constriction band, congenital amputation, or acrosyndactyly (see Plate 4-50). When the constriction band is severe, intrauterine gangrene may develop and a true fetal amputation occurs.

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