Background: Pseudo-Madelung deformity is accepted as one of the causes of carpal instability, and lunotriquetral fusion is used in the treatment of carpal instabilities. Case Report: We report a case with paradoxical features, i.e. bilateral lunotriquetral synostosis is associated with scaphotrapeziotrapezoidal instability on the right side, which is prevented by pseudo-Madelung deformity on the left side. Conclusions: The paradoxical features of the present case indicate the necessity for reevaluation of the carpal instability concept.

Keywords: lunotriquetral synostosis, Pseudo-Madelung deformity, scaphotrapeziotrapezoidal instability