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Objectives: To compare the biomechanical properties of a new nitinol intramedullary (IM) scaffold implant with those of volar plates for the treatment of dorsally comminuted extra-articular distal radius fractures using an established model., Methods: A dorsal wedge osteotomy was performed on a bone model to simulate a dorsally comminuted extra-articular distal radius fracture. This model was used to compare stiffness of 3 different distal radius fixation devices--an IM scaffold implant, a commercially available titanium volar locking plate, and a stainless steel non-locking T-plate. Six constructs were tested per group. Tolerance for physiological loading was assessed by applying 10,000 cycles of axial loading up to 100 N applied at 2 Hz. Axial and eccentric load stiffness were assessed before cyclic loading and axial stiffness again after cyclic loading. Groups were compared using analysis of variance., Results: Initial axial stiffness (in Newton per millimeter) was significantly (P = 0.011) different only between the volar locking plate (427 ± 43) and non-locking T-plate (235 ± 69). After cyclic loading, axial stiffness was not significantly different between the volar locking plate (392 ± 67) and IM scaffold implant (405 ± 108), but both were significantly (P < 0.001) stiffer than the non-locking T-plate (187 ± 53). Eccentric loading stiffness was not significantly different between the IM scaffold implant (67 ± 140) and volar locking plate (63 ± 5), but both were significantly (P < 0.001) stiffer than the non-locking T-plate (25 ± 4)., Conclusions: Stiffness of the IM scaffold implant and volar locking plate fracture model constructs was equivalent. Biomechanical testing suggests that this novel IM scaffold provides sufficient stability for clinical use, and further testing is warranted. more...