We report two cases of metacarpal arch disruption after Motec® total wrist arthroplasty, with hyperextension of the third metacarpal and dorsal protrusion of the head. Correction osteotomies of the adjacent metacarpals using preoperative 3D surgical planning were successful. This report seeks to shed light on the origin of this deformation and to recommend some operative precautions. It is important that surgeons should be aware of the existence of this complication, as disruption of the transverse metacarpal arch affects both grasp and hand esthetics. LEVEL OF EVIDENCE: IV.