The strain at bone-implant interface determines the effect of spinopelvic reconstruction following total sacrectomy: a strain gauge analysis in various spinopelvic constructs.
OBJECTIVE
There is still some controversy regarding the optimal biomechanical concept for spinopelvic stabilization following total sacrectomy for malignancy. Strains at specific anatomical sites at pelvis/sacrum and implants interfaces have been poorly investigated. Herein, we compared and analyzed the strains applied at key points at the bone-implant interface in four different spinopelvic constructs following total sacrectomy; consequently, we defined a balanced architecture for spinopelvic fusion in that situation.


METHODS
Six human cadaveric specimens, from second lumbar vertebra to proximal femur, were used to compare the partial strains at specific sites in a total sacrectomy model. Test constructs included: (1) intact pelvis (control), (2) sacral-rod reconstruction (SRR), (3) bilateral fibular flap reconstruction (BFFR), (4) four-rods reconstruction (FRR), and (5) improved compound reconstruction (ICR). Strains were measured by bonded strain gauges onto the surface of three specific sites (pubic rami, arcuate lines, and posterior spinal rods) under a 500 N axial load.


RESULTS
ICR caused lower strains at specific sites and, moreover, on stress distribution and symmetry, compared to the other three constructs. Strains at pubic rami and arcuate lines following BFFR were lower than those following SRR, but higher at the posterior spinal rod construct. The different modes of strain distribution reflected different patient's parameter-related conditions. FRR model showed the highest strains at all sites because of the lack of an anterior bracing frame.


CONCLUSIONS
The findings of this investigation suggest that both anterior bracing frame and the four-rods load dispersion provide significant load sharing. Additionally, these two constructs decrease the peak strains at bone-implant interface, thus determining the theoretical surgical technique to achieve optimal stress dispersion and balance for spinopelvic reconstruction in early postoperative period following total sacrectomy.
Department of Spine Surgery, Tongji Hospital, Tongji University School of Medicine, Shanghai, China.
Yan
Y
Yu
Department of Spine Surgery, Tongji Hospital, Tongji University School of Medicine, Shanghai, China ; Julius Wolff Institut, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Rui
R
Zhu
Department of Spine Surgery, Tongji Hospital, Tongji University School of Medicine, Shanghai, China.
Zhi-Li
ZL
Zeng
Department of Spine Surgery, Tongji Hospital, Tongji University School of Medicine, Shanghai, China.
Yong-Wei
YW
Jia
Department of Spine Surgery, Tongji Hospital, Tongji University School of Medicine, Shanghai, China.
Zhou-Rui
ZR
Wu
Department of Spine Surgery, Tongji Hospital, Tongji University School of Medicine, Shanghai, China.
Yi-Long
YL
Ren
School of Life Science and Technology, Tongji University, Shanghai, China ; Institute of Orthopaedics and Traumatology, Shanghai, China.
Bo
B
Chen
School of Life Science and Technology, Tongji University, Shanghai, China.
Zu-Quan
ZQ
Ding
Department of Spine Surgery, Tongji Hospital, Tongji University School of Medicine, Shanghai, China.
Li-Ming
LM
Cheng
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D010384:Pelvic Bones / Q000601:surgery*; D019736:Prostheses and Implants; D019651:Plastic Surgery Procedures / Q000009:adverse effects*; D012447:Sacrum / Q000601:surgery*; D013123:Spinal Fusion / Q000009:adverse effects*; D013314:Stress, Mechanical