Vascularized pisiform graft for the treatment of scaphoid nonunion: An anatomical study

Scaphoid fracture can evolve into scaphoid nonunion leading to wrist arthritis. Vascularized bone flaps used to treat scaphoid nonunion are supplied by delicate, small, or short arteries that are not always reliable. The pisiform bone has never been considered as a possible treatment of scaphoid nonunion since the traditionally harvested pedicle is too short. This study aimed to characterize the vascularization of the pisiform with the goal of developing a method of harvesting it with a longer pedicle that can be used as a graft to treat scaphoid nonunion. A cadaver study on 30 upper limbs was done in two parts: firstly, we dissected 20 cadaver specimens and documented the pisiform's vascularization (size, length, and articular surface) as well as anatomical characteristics of the dorsal ulnar artery; secondly, we used 10 cadaver specimens to study an experimental surgical procedure in which a vascularized pisiform graft is used to treat an artificially created nonunion and confirm its feasibility. The pisiform artery originated from the dorsal ulnar artery in all 20 dissections. Its average length of 4.036cm could be increased by 11% by ligating the upstream collateral branches from the dorsal ulnar artery. The pedicled vascularized pisiform flap was grafted to the scaphoid in 10 experimental procedures performed on fresh cadavers. The vascularized pisiform graft consists of a reliable vascular pedicle and well vascularized multi-cortical bone with a cartilaginous surface. However, more studies are needed to confirm the feasibility of this flap as an alternative for treating unstable scaphoid nonunion.