| Discussion: |
Macrodystrophia lipomatosa is a rare congenital form of localised gigantism characterised by a soft fusiform fibrofatty mass that infiltrates and replaces a large nerve and its branches. There is atrophy of the associated neural elements (unlike neuroma and neurofibroma) with bone and soft tissue overgrowth. Most cases involve the median nerve or plantar nerve. The lesion presents at birth or in infancy as a painless gradually enlarging mass with neuropathy. Growth ceases at puberty.
Plain films demonstrate soft tissue and bone overgrowth with macrodactyly. Lucent areas may be apparent in the soft tissues representing fat. There is an increased incidence of syndactyly and polydactyly. Degenerative changes occur in late childhood or adolescence. CT demonstrates bone hypertrophy, osteophyte formation and abundant adipose tissue. MRI shows a fatty mass with fibrous tissue strands and bone hypertrophy. Surgery is usually performed for cosmetic or mechanical reasons and varies from excision of the mass to amputation.
Overgrowth (macrodactyly) Differential
This condition should be differentiated from others in which an enlargement may occur (ie, vascular malformations, enchondromatoses, osteoid osteoma, fibrous dysplasia, lipomatoses). Macrodactyly is nevertheless a heterogenous group, with 4 of the common presentations as follows:
Macrodactyly associated with nerve-orientated lipofibromatosis: This is the most common form with no inheritance pattern. It alternately is described as nerve-territory orientated macrodactyly (NTOM). It most commonly occurs in the median nerve distribution. Two types of growth occur: static, in which the growth is proportional to that of the child; and progressive, in which it is more rapid. The outstanding feature is the fatty infiltration of neural tissue. Tsuge believes the overgrowth to be "nerve-driven" (nerve resection sometimes cures it).
Macrodactyly associated with neurofibromatosis: Gigantism of the upper or lower limbs is a well-known concomitant of neurofibromatosis. Diagnostic criteria are (1) 6 café au lait spots greater than 2.5 cm, (2) multiple neurofibromas along peripheral nerves, and (3) pedunculated cutaneous tumors termed molluscum fibrosum. It is similar to macrodactyly associated with nerve-orientated lipofibromatosis in presentation but also may involve osteocartilaginous outgrowths. Unlike in the lipofibromatosis-associated type, digital enlargement is seldom unilateral. No marked fatty infiltration of peripheral nerves is present, although the same degree of perineural fibrosis is present.
Macrodactyly associated with hyperostosis: In this form, no neural abnormality occurs. Osteochondral masses, but not enchondromata, are present.
Macrodactyly/gigantism and hemihypertrophy: This is rare.
The progressive type of macrodactyly is particularly debilitating, functionally and psychologically. Individualization of treatment is particularly important, perhaps more so than in other forms of congenital hand surgery. The objectives are to diminish length and bulk without compromising sensation or vascularity. Surgical options include the following:
Epiphysiodesis or total physeal resection
Staged debulking (can incorporate longitudinal bony resection and excision or osteochondral masses)
Nerve stripping or resection and end-to-end coaptation
Shortening procedures: In Tsuge's version, a dorsal dog-ear results; in the Barsky version, the dog-ear is on the ventral surface
Partial amputation or ray amputation