Bone fixation plates are used in tibial osteotomy and other procedures to secure two bone segments together. In a tibial osteotomy, for example, a curvilinear cut is made in the canine proximal tibia to separate the metaphysis from the proximal tibia. Next, the metaphysis is rotated to level the tibial plateau. Finally, the metaphysis is fixed to the proximal tibia by a fixation plate. See U.S. Pat. No. 5,304,180 incorporated herein by this reference. The fixation plate of this patent includes a broad triangular portion to be fixed to the metaphysis of the tibia and a narrower leg section to be fixed to diaphysis of the tibia. There are three bone screw holes in the triangular portion and three bone screw holes in the leg section.
The fixation plate produced in accordance with this patent, however, is cast from surgical grade stainless steel and thus is relatively thick (approximately 5 mm). Also, there have been reports of an increased tumor occurrences when these fixation plates are used. See “Metallurgical Evaluation of the Slocum TPLO Plate”, Boudrieau et al., paper presented at the 32nd Annual Conference of the Veterinary Orthopedic Society, Mar. 5-12, 2005.
U.S. Pat. Nos. 4,867,144 and 4,988,350 disclose other configurations for bone fixation plates. In many fixation plates, there is a fairly sharp transition between the wide and narrow sections of the fixation plate resulting in a possible weak stress zone subject to breakage.
USPTO Backgrounds
USPTO Backgrounds