The association of radial deficiency with thumb hypoplasia

Congenital longitudinal deficiencies of the radius and thumb are known to be associated with one another; however, the details of their relationship are unknown. The purpose of this study was to determine whether increased severity of radial deficiencies is associated with increased severity of thumb deficiencies and to review the relationship between radial deficiency and reconstructibility of a hypoplastic thumb.

Radiographs and charts of 227 affected upper extremities of 139 patients with radial longitudinal deficiency were reviewed. The associated thumb deficiency was classified according to a modification of the Blauth and Schneider-Sickert scheme and the radial deficiency was classified according to a modification of the Bayne and Klug criteria for 191 extremities of 119 patients.

The severity of the thumb deficiency was directly proportional to the severity of the radial deficiency (p < 0.0001). Half of the extremities had either a thumb deficiency or thumb and carpal deficiencies without radial deficiency. Two-thirds (sixty-three) of the ninety-five limbs with a normal radius had a thumb that could be surgically reconstructed. Seventy-one (91%) of seventy-eight extremities with a thumb amenable to surgical reconstruction had a radius that did not require surgical reconstruction. All extremities with a radial and/or carpal deficiency had a thumb deficiency. Forty-eight (94%) of fifty-one extremities with complete absence of the radius had a thumb that was not reconstructible.

This study supports the growing body of evidence that the components of radial longitudinal deficiency represent a progressive spectrum of upper extremity abnormalities, and a distal progression of severity, with distal structures likely to be more involved than proximal structures.