Proximal metatarsal osteotomies are inherently unstable and difficult to fix. The purpose of this study was to compare the mechanical stiffness in sawbone models of medially versus dorsally placed plates and then to compare semilocked versus nonlocked plates in different osteotomy configurations. Thirty sawbone models were constructed, fixed either with titanium self-locking or steel mini-fragment plates. They were divided in groups and their stiffness was measured. The stiffness of any model fixed with medial titanium or steel plates was on average 158% and 228% greater, respectively, compared to dorsal plates. Adding a dorsal shelf of bone to a proximal closing wedge osteotomy increases its stiffness. Using locked plates increased the mechanical stiffness in only one configuration. The article suggests that models fixed with medial plates have greater resistance to failure than models fixed with dorsal plates. Using locked plates does not increase the mechanical stiffness of the construct.