A finite element analysis of the pelvic reconstruction using fibular transplantation fixed with four different rod-screw systems after type I resection.
BACKGROUND
The pelvis often needs to be reconstructed after bone tumor resection. A major challenge here for the orthopedic surgeons is to choose a method that gives the best performance which depends upon its biomechanical properties. In this study, a 3-dimensional finite element analysis (FEA) was used to analyze the biomechanical properties of reconstructed pelvis using fibula transplant fixed by four commonly used rod-screw systems.


METHODS
A total pelvic finite-element model including the lumbar-sacral spine and proximal femur was constructed based on the geometry of CT image from a healthy volunteer. Three-dimensional finite element models of different implants including fibula, rod and screw were simulated using ways of solid modeling. Then various reconstructed finite element models were assembled with different finite element implant model and type I resected pelvic finite element model. The load of 500 N was imposed vertically onto the superior surface of L3 vertebral body, and the pelvis was fixed in bilateral leg standing positions. FEA was performed to account for the stress distribution on the bones and implants. The pelvis displacement of the different rod-screw fixation methods and the maximum equivalent stress (max EQV) on all nodes and element were figured out to evaluate the advantages and disadvantages of different reconstructive methods.


RESULTS
Stress concentration in the fibula transplant was extremely high in the reconstructed pelvis, but could be substantially decreased by internal fixation, which partially transferred the stress from the fibula to the rod-screw systems. High stress concentration was also found in the implants, especially in the connection sites between screw and rod. Among the four methods of fixation, a double rod system with L5-S1 pedicle and ilium screws (L5-S1 HR) produced the best performance: least stress concentrations and least total displacement.


CONCLUSIONS
According to the stability and stress concentration, the method of L5-S1 HR fixation combined with fibula transplantation is better than other fixation methods in pelvic reconstruction after type I resection.
Jia
Yong-wei
YW
Orthopedic Department, Tongji Hospital, Tongji University, Shanghai 200065, China.
Cheng
Li-ming
LM
Yu
Guang-rong
GR
DU
Cheng-fei
CF
Yang
Zhi-yong
ZY
Yu
Yan
Y
Ding
Zu-quan
ZQ
D000328:Adult; D001696:Biomechanical Phenomena; D001859:Bone Neoplasms / Q000601:surgery*; D001863:Bone Screws; D005272:Femur Neck / Q000601:surgery; D005360:Fibula / Q000637:transplantation*; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D010384:Pelvic Bones / Q000601:surgery*; D019651:Plastic Surgery Procedures / Q000379:methods*