The 3-dimensional configuration of the typical foot and ankle in diastrophic dysplasia.

BACKGROUND: Surgical correction of the foot and ankle in patients with diastrophic dysplasia is extremely difficult secondary to the markedly distorted pathoanatomy. Several authors have described superficially some of the clinical and radiographic findings typical of the foot and ankle with diastrophic dysplasia; however, no description of the specific osseous deformities has been described in the literature. The purpose of this article was to provide such a model, detailing the nature of deformity of each of the bones and joints in the foot and ankle and their relationship to each other from a pathoanatomical standpoint.

METHODS: A 3-dimensional sculpted model and detailed drawings were developed based on radiographs, computed tomography reconstructions, and direct observation both in and out of surgery. Fifty-three patients representing 106 feet formed the basis of this analysis (age, 3 days to 32 years). An additional 12 feet of the senior author's cases provided further confirmation of these deformities.

RESULTS: Superficially, the apparent deformity most closely resembles a Z-type foot or serpentine foot. The overall deformity bears no true resemblance to the idiopathic clubfoot. Typically, the hindfoot is in severe equinus with the subtalar joint being deformed into valgus and moving more posteriorly. In contrast to the idiopathic clubfoot, the navicular was markedly angulated laterally on the talus. The medial cuneiform was deviated medially on the navicular articulation. The forefoot was foreshortened and in marked varus positioning with varus of the entire metatarsals. The second to fifth metatarsals bend and curve near their bases as they tilt toward the first metatarsal.

CONCLUSION: The disturbed pathoanatomy of the diastrophic dysplasia foot and ankle reflects the difficulties in achieving any substantial surgical correction without customization. Surgical management of the foot and ankle in diastrophic dysplasia must be individualized and based on a clear understanding of the unique segmental malalignment of the foot and ankle.