RESUMEN
INTRODUCTION: The abductor pollicis longus (APL) presents two muscle bellies and multiple accessory tendons available for transfer, amongst these an accessory tendon inserting on the thenar aponeurosis (APLTh). Edgerton described an opponensplasty using the whole APL tendon, but its results were limited due to the short size of the donor tendon. HYPOTHESIS: The purpose of this study is to assess the feasibility of transferring the APLTh for thumb opposition. MATERIAL AND METHODS: Eleven cadaver upper limbs were dissected to assess the presence of the two heads of the APL as well as their main and accessory tendon insertions. The accessory tendon of the APL inserting on the thenar aponeurosis (APLTh) was harvested with a slip of the thenar aponeurosis. The length of the transplant, the number of tendon slips and their location, as well as pre and postoperative radial and palmar abduction provided by the APL were assessed. RESULTS: The APL was present in all cadavers whereas its insertion on the thenar aponeurosis was absent in 18% of the cases. When the APLTh was present and could be used for opponensplasty, the mean gain in palmar abduction was 16 degrees, and the mean loss in radial abduction was 21 degrees. DISCUSSION: Although the experiments revealed a variability in APL anatomy, when present, the APLTh represents a suitable donor for the restoration of thumb opposition. In some cases of high median nerve palsies, thumb opposition can't be restored using median innervated muscles. In these cases, when the APLTh is present, it can be used to restore thumb opposition without functional loss. LEVEL OF EVIDENCE: IV; anatomical feasibility study.