Stability of fixation methods in large mandibular advancements after sagittal split ramus osteotomy: An in vitro biomechanical study

Abstract Sagittal split ramus osteotomy (SSRO) with large mandibular advancements is a common surgical procedure and could be indicated for patients with sleep apnoea. As a large variety of fixation methods is used for the stabilization of SSRO, a biomechanical test model was used to analyze which fixation technique is most stable. For this in vitro study, 80 polyurethane hemimandibles with a prefabricated SSRO were used as substrate. Loads in Newtons were recorded at displacements of the mandibular incisive edge at 1 mm, 3 mm and 5 mm. The samples were divided into two groups: mandibular advancement of (1) 10 mm and (2) 15 mm. In both groups, four fixation techniques were used: (A) one 4-hole miniplate; (B) two 4-hole miniplates; (C) one 4-hole miniplate plus one bicortical screw; and (D) three bicortical screws in an inverted-L arrangement. In group 1, three bicortical screws resulted in the best stability. In group 2, two miniplates resulted in the best stability. The use of two miniplates did not show significant differences between both groups. Other fixation methods showed more stability with 10 mm advancement. This study therefore suggests that in advancements exceeding 10 mm, the use of two miniplates is the optimal means for providing rigid fixation for large mandibular advancements in SSRO.