This retrospective study analyses long-term outcomes of reconstruction for congenital thumb hypoplasia Grades 2 and 3 A. In 22 thumbs (mean follow-up 9 years), instability of the metacarpophalangeal joint was found in 20 thumbs regardless of the method of reconstruction, double breasting of local tissue with or without adductor pollicis advancement or use of a slip of flexor digitorum superficialis to supplement local tissue. There was a trend towards a greater global strength, higher Kapandji score and better subjective function score when the abductor digiti minimi was used as an opposition transfer as compared with the flexor digitorum superficialis. Results for motion and subjective parameters were consistent with comparable studies though these comparisons are compromised by different methods of classification and assessment. Consistent application of an expanded Blauth grading system and a formal hypoplastic thumb score will improve the ability to compare pre- and postoperative status, different techniques and results from different centres. Level of evidence: IV
