A biomechanical study of the effect of pins number on stability of Persian fixation technique for distal humerus fractures

Distal humerus fractures are common in people with osteoporosis and remain one of the challenges in orthopedic surgery. Persian fixation method was introduced as a novel technique to treat distal humerus fractures. In general, the Persian fixation surgery is performed in two ways, L and Delta, in which some pins and a plate are used to fix the fragments. This study aimed to investigate the effect of the number of pins used in surgery on the stiffness of the fixation. In the Delta method simulation, according to surgeon's suggestions, 1 to 3 number of the pin were considered. In most surgeries, they use these number of pins unless the patient has a large fragment that has enough space to use more pins. The diameter of each pin was 2 mm, and the height of the plate fixation ranged from 4.5 to 6.5 cm. Three CAD models with a variable number of pins and Delta structure were prepared. Finally, for these three models, simulations were performed by applying anterior bending force to the humerus bone to evaluate the stability of the Persian fixation with varying number of pins. According to obtained results, increasing the number of pins used in the Persian fixation method with Delta structure helped increase the stability and reduce the displacement of fragments.