Background: In contrast to longitudinal deficiencies, phocomelia is
considered a transverse, intercalated segmental dysplasia. Most patients
demonstrate severe, but not otherwise classifiable, upper-extremity
deformities, which usually cannot be placed into one of three previously
described phocomelia groups. Additionally, these phocomelic extremities do not
demonstrate true segmental deficits; the limb is also abnormal proximal and
distal to the segmental defect. The purpose of this investigation was to
present evidence that upper-extremity abnormalities in patients previously
diagnosed as having phocomelia in fact represent a proximal continuum of
radial or ulnar longitudinal dysplasia.
Methods: The charts and radiographs of forty-one patients (sixty
extremities) diagnosed as having upper-extremity phocomelia were reviewed
retrospectively. On the basis of the findings on the radiographs, the
disorders were categorized into three groups: (1) proximal radial longitudinal
dysplasia, which was characterized by an absent proximal part of the humerus,
a nearly normal distal part of the humerus, a completely absent radius, and a
radial-sided hand dysplasia; (2) proximal ulnar longitudinal dysplasia,
characterized by a short one-bone upper extremity that bifurcated distally and
by severe hand abnormalities compatible with ulnar dysplasia; and (3) severe
combined dysplasia, with type A characterized by an absence of the forearm
segment (i.e., the radius and ulna) and type B characterized by absence of the
arm and forearm (i.e., the hand attached to the thorax).
Results: Twenty-nine limbs in sixteen patients could be classified
as having proximal radial longitudinal dysplasia. Systemic medical conditions
such as thrombocytopenia-absent radius syndrome were common in those patients,
but additional musculoskeletal conditions were rare. Twenty limbs in seventeen
patients could be classified as having proximal ulnar longitudinal dysplasia.
Associated musculoskeletal abnormalities, such as proximal femoral focal
deficiency, were common in those patients. Eleven limbs in ten patients were
identified as having severe combined dysplasia, which was type A in seven of
them and type B in four. Four patients with severe combined dysplasia had
congenital cardiac anomalies, and four had associated musculoskeletal
abnormalities. Three of the four patients with the type-B disorder had a
contralateral ulnar longitudinal dysplasia.
Conclusions: We propose that cases previously classified as
upper-extremity phocomelia represent a spectrum of severe longitudinal
dysplasia, as none of the sixty extremities that we studied demonstrated a
true intercalary deficiency. These findings have both developmental and
Level of Evidence: Diagnostic Level II. See Instructions
to Authors for a complete description of levels of evidence.