Three-dimensional finite element analysis of the treatment of Kienbock's disease by use of the shift pisiform bone

Objective: The aim of this study was to determine the optimal position of the pisiform bone in "Saffar's Procedure" and to evaluate the necessity of combined carpal fusion. Method: A three-dimensional (3D) finite element model of the wrist was established, and we verified its effectiveness using Mimics 16.0 software. Three kinds of shift pisiform bone position models and two kinds of carpal fusion models were established by reassembling the wrist 3D model. The stress analysis of each model was analyzed and compared using Pro/Engineer5.0 and ANSYS14.0 software. 12 patients with Kienbock's disease were treated according to the results of the finite element analysis. Result: The 3D finite element model of the wrist was successfully established and validated. The best substitute position of the pisiform bone was to rotate its pisiform-triangular articular surface to articulate with the radial. And combined STT or scaphoid-capitate carpal fusion was also suggested. The follow-up periods were 12-82 months with an average of 43 months. Pain was relieved in 12 patients, and the VAS score was 1.5 +/- 1.8. The wrist grip power was 80.8% of the contralateral hand. The excellent and good rate of the Cooney score was 83.3%. The incidence of osteoarthritis was 16.7%. Conclusion: The optimal replacement position of the pisiform bone and the necessity of combined carpal fusion were determined through the 3D finite element analysis, and we verified it by clinical follow-up. It may optimize the surgical procedure and improve patient prognosis, and it may especially reduce the risk of osteoarthritis or even necrosis of the shift pisiform bone.