Purpose: To assess the effect of radial longitudinal deficiency on the function of pollicized digits as determined by the Thumb Grasp and Pinch (T-GAP) assessment.
Methods: We retrospectively evaluated 25 hands with thumb hypoplasia that underwent index finger pollicization. Patients were followed for an average of 10.4 years. Hands were divided by severity into two groups: no or mild radial longitudinal deficiency (RLD) (Group 1 = 16) and moderate to severe RLD (Group 2 = 9). We collected demographic information and completed physical examination measures, including hand strength, elbow, wrist, and hand range of motion, the Kapandji opposition score, active grasp span, and T-GAP total score.
Results: Patients with moderate to severe forms of RLD had stiffer long fingers, lower Kapandji opposition scores, and limited active and passive range of motion for elbow flexion, wrist ulnar deviation, and pollicized thumb interphalangeal flexion. They had shorter forearms, decreased active grasp span, and fewer thumb creases at the interphalangeal thumb joint. In addition, the T-GAP total score was significantly lower when comparing the two groups. Children with mild dysplasia were able to achieve 32% of age-matched normal grasp strength. Patients with more severe radial dysplasia averaged 17% less grasp strength compared with children with mild dysplasia. Patients with moderate to severe RLD also had lower T-GAP total scores and strength measurements if they had limited wrist ulnar deviation.
Conclusions: Individuals with moderate to severe RLD have unique anatomical factors that affect outcomes after pollicization. These individuals use their thumbs for fewer activities, have weaker grasp, and retain more primitive grasp patterns compared with those who have milder forms of RLD.
Type of study/level of evidence: Prognostic IV.
Keywords: Pollicization; radial longitudinal deficiency; thumb hypoplasia; thumb use.
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