Background: Ulnar head fractures are increasingly higher with the growing proportion of the elderly in the population. Failure to achieve stable anatomic reduction of ulna head fracture may lead to the DRUJ dysfunction and nonunion of distal radius. Due to the lack of the postoperative reporting outcomes and the biomechanical studies, it has not been well established about the optimal management of the comminuted distal ulna head fracture. This study aimed to explain the advantages and

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... ages of the ulnar-side locking plate fixation, compared with the dorsal-side one, and its screws arrangement in the treatment of the ulnar head fracture by using finite element analysis. Methods: FE models of the ulnar head fracture and the models of ulnar-side locking plate and dorsal-side plate with two or three distal screws was constructed. In order to simulate forces acting on the ulnar and the osteosynthesis material during daily-life activity in subjects who underwent reconstructive surgery, we applied three loading conditions to each model, viz. axial compression 20N, 50N, and torsion moments 1Nm. Under these conditions, values of the von Mises Stress (VMS) distribution of the implant, peak VMS, and model displacement were investigated. Results: Both the stress values and model displacement of ulnar-side plate were lower than those of dorsal-side plate. When adding a screw in the middle hole of the ulnar head, the values of model displacement and the peak stress in fixation system are lower, but it may evidently concentrate the stress on the middle screw. Conclusions: In conclusion, our study indicated that plating locking plate on ulnar side had lower stress distribution on the plate and better stability than on dorsal side in ulnar head fracture fixation. Adding the additional screw on the ulnar head could reduce the displacement of the fixation system and increase the stability of the fixation system. This study requires clinical confirmation as to its practicality in the treatment of ulnar head fracture.