Comparison of four reconstruction methods after total sacrectomy: a finite element study.
BACKGROUND
After total sacrectomy, it is mandatory to reconstruct the continuity between the lumbar spine and the pelvis. Only few biomechanical analyses exist which compare different reconstructions. Therefore, the aim of this study was to compare the lumbo-pelvic motion and the relative risk of implant breakage for four different reconstructions after total sacrectomy.


METHODS
Finite element analyses were performed for four general different reconstructions after total sacrectomy: sacral-rod reconstruction, four-rod reconstruction, bilateral fibular flaps reconstruction, and improved compound reconstruction. The rotations between L5 vertebra and ilium, the L5 shift-down displacement, and the maximum von Mises stress in the implants were calculated and evaluated for flexion, extension, lateral bending and axial rotation.


RESULTS
The decreasing order of the rotations between L5 vertebra and ilium as well as of the L5 shift-down displacement for the studied reconstruction methods was four-rod reconstruction>sacral-rod reconstruction>bilateral fibular flaps reconstruction>improved compound reconstruction. The decreasing order of the maximum von Mises stress in the implants was sacral-rod reconstruction>four-rod reconstruction>bilateral fibular flaps reconstruction>improved compound reconstruction.


CONCLUSIONS
From the mechanical point of view, improved compound reconstruction is superior to the other methods studied here as it shows the highest stability and the lowest maximum von Mises stress. However, clinical aspects must also be regarded when choosing a reconstruction method for a specific patient.
Department of Spine Surgery, Tongji Hospital, Tongji University School of Medicine, 389 Xincun Road, 200065 Shanghai, PR China.
Rui
R
Zhu
Li-ming
LM
Cheng
Yan
Y
Yu
Thomas
T
Zander
Bo
B
Chen
Antonius
A
Rohlmann
D001696:Biomechanical Phenomena; D001863:Bone Screws; D055119:Elastic Modulus; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D009038:Motion; D019637:Orthopedic Procedures / Q000379:methods*; D010388:Pelvis / Q000033:anatomy & histology / Q000601:surgery; D016059:Range of Motion, Articular; D019651:Plastic Surgery Procedures / Q000379:methods*; D015203:Reproducibility of Results; D012399:Rotation; D012447:Sacrum / Q000601:surgery*; D013131:Spine / Q000601:surgery*