Design and comparative numerical analysis of designs of intramedular telescopic systems for the rehabilitation of patients with osteogenesis imperfecta (OI) type III

The Fassier-Duval^® telescopic intramedullary (IM) system is the most used in the treatment of Osteogenesis Imperfecta (OI) to provide support and stiffness in long bones. Researchers have documented several complications that reduce the percentage of success in rehabilitations between 50 and 60%, this is because of the loss of fixation on the threaded ends with the epiphyses, the rotation and the mechanical failure of the male implant become apparent when exceeding 1/3 of length outside of the female implant causing the need of multiple post-operations on the patient. Therefore, this work proposes innovative designs with different mechanical and geometrical changes, to fight these complications, increasing the percentage of patients with a successful rehabilitation. The ASTM-1264 standard mention that the IM systems must be analyze in 4-points bending and torsion, so numerical analysis of this test were carried out to compare the stresses and strains behavior to conclude which design has the best mechanical characteristics against the actual telescopic system and thus avoid more complications. Likewise, the authors propose a change in the threads on both ends of the system. These modifications are analyzed to improve the grip between the bone and the IM system preventing injuries to the bone.