Classification of ulnar deficiency according to the thumb and first web.

Fifty-five ulnar-deficient upper extremities in 45 patients treated at the St. Louis Shriner's Hospital were reviewed in order to evaluate the hand abnormalities. Thumb and first-web abnormalities were noted in 73% of hands. The majority of operations (28 of 53) were recommended to improve functional deficits associated with abnormalities of the thumb and first web. A classification of the ulnar-deficient hand based upon the characteristics of the thumb and first web is presented. When used in combination with any of the six current forearm/elbow classification schemes, this classification more completely describes ulnar deficiency of the upper extremity. Four classification types are proposed based upon progressive involvement of the thumb and first web. In type A, the thumb and first web are normal; in type B, the first web space has mild deficiency and the thumb has mild involvement. Extrinsic tendon function is intact and opposition function is present. In type C, the thumb has varying degrees of involvement. The first web has moderate to severe deficiency, including thumb-index syndactyly, and is often associated with malrotation of the thumb into the plane of the other digits, loss of opposition, and dysfunction of the extrinsic tendons. In type D, the thumb is absent. Previous classifications of ulnar deficiency neglect the radial hand anomalies that have been noted by several authors in a high percentage of affected extremities. Our premise for this classification is that the thumb and first-web abnormalities are related to the complexity of the hand problem and that the frequently noted radial hand abnormalities require the majority of surgical procedures. Such a classification based on the thumb and first-web deformities will focus the surgeon's attention on those deficiencies that are most important for the restoration of function. It is proposed that ulnar deficiency be classified by one of the classification schemes that describes the anatomy of the forearm and/or elbow supplemented by the hand classification type.