[Piso-triquetral osteoarthritis. Thirteen case reports and review of the literature].

Piso-triquetral osteoarthritis (OA) is an infrequent cause of ulnar wrist compartment pain. Specific clinical manoeuvres may help for diagnosis. If this aetiology is suspected, a 30 degrees oblique wrist X-ray in supination and sometimes a CT scan with transverse cuts should be performed demonstrating a joint narrowing and osteophytes formation. The FCU-pisiform biomechanical unit transfers the wrist flexion forces. A series of 13 cases of piso-triquetral OA is presented in 12 patients (six females and six men) treated between 1990 and 1997. Mean age was 52.7 y. Pain at resisted motion in flexion and ulnar deviation and strength decrease was always present at clinical examination. Subperiosteal pisiform excision has been constantly performed. Continuity of FCU insertions and its distal ligamentous extensions has been preserved. Mean F-up was 18.1 months (3-57). Pain has disappeared in seven cases and significantly decreased in five. NSD was present in one case. Range of motion and strength was normal in all cases. Ulnar nerve paresthesias has always disappeared. The pisiform bone is not a sesamoid: a true joint with the triquetrum exists. From the phylogenetic point of view, three theories have been proposed: (a) in some species, pisiform is fused with adjacent bones or metacarpals; (b) pisiform is a remnant of a polydactyly hand; (c) pisiform is a remnant of the carpal central row.