A biomechanical analysis of the orbitozygomatic complex in human cadavers:Examination of load sharing and failure patterns following fixation with titanium and bioresorbable plating systems

The orbitozygomatic complex (OZC) and zygomatic arch act as key buttresses in the restoration of midfacial projection and width in the treatment of pa nfacial fractures, yet little is known about the biomechanical and deformat ional forces placed on this region under applied load conditions. The aims of this project were (1) to study the stress-force relationships and load s haring of the intact human OZC under subfailure loads, (2) to assess load s haring and breaking strength of the OZC when intact and after four-point mi niplate fixation with either titanium (1.2 and 1.7 mm) or bioresorbable (1. 5 and 2.0 mm) systems, and (3) to analyze failure patterns. Using the MTS m achine, fresh frozen human skulls stripped of soft tissue underwent loading with subfailure and failure forces directed in a standard fashion. Electri cal resistance gauges applied directly to local and remote bony buttresses demonstrated temporary deformation at local (zygomatic arch, lateral and in ferior orbital rim) and remote (supraorbital rim) buttresses under subfailu re loading conditions. Breaking strength of the OZC (N = 10) measured befor e and after four-point application of 1.2- or 1.7-mm titanium or 1.5- or 2. 0-mm bioresorbable miniplates demonstrated a significant (p < 0.05) decreas e compared with intact controls. Surprisingly, the 2.0-mm bioresorbable min iplate construct provided only 13% of the intact breaking strength of the O ZC compared with 39% for the 1.7-mm titanium system (p < 0.05). Plate bendi ng or breakage was responsible for failure of the OZC following rigid fixat ion. Biomechanical testing of the OZC demonstrates (1) load sharing at regi onal and remote bony buttresses, (2) significant decreases in breaking stre ngth following miniplate fixation, and (3) deformation of miniplates as a p rimary cause of failure under load conditions. Data generated from this pro ject may be useful with regard to optimizing fixation of the OZC in the con text and treatment of panfacial fractures.