441 - Biomechanical Analysis of Spinal Pelvic Reconstruction after Total Sac...

#441 Biomechanical Analysis of Spinal Pelvic Reconstruction after Total Sacrectomy: Comparison of Three Techniques

General Session: Infections/Tumor

Presented by: A. Clark

Author(s):

A.J. Clark (1)
J.A. Tang (2)
J.M. Leasure (2)
M.E. Ivan (1)
J.M. Buckley (2)
V. Deviren (3)
C.P. Ames (1)

(1) UCSF, Neurosurgery, San Francisco, CA, USA
(2) Taylor Collaboration Laboratories, San Francisco, CA, USA
(3) UCSF, Orthopaedic Surgery, San Francisco, CA, USA

Abstract

Object: Reconstruction after total sacrectomy is a critical component of malignant sacral tumor resection. However, early mobilization, implant loosening and breakage remain major problems. Traditional techniques employed inter-iliac femoral allograft but more modern methods have employed fibular or cage struts from ilium to L5 endplate or sacral body replacement with transiliac bars anchored to expandable cages to L5 endplate. This study compares the biomechanical stability of the three current methods.

Methods: Total sacrectomy was performed and reconstruction was completed using three different constructs in conjunction with posterior spinal screw rod instrumentation from L3-pelvis; inter-iliac femur strut (FS, Figure 1A,B), L5-iliac cage struts (CS, Figure 1C,D), and S1 body replacement expandable cage (EC, Figure 1E,F) transiliac bar-L5.

Intact lumbar specimens (L3-sacrum) were tested for flexion-extention range of motion (FE-ROM), axial rotation ROM (AX-ROM), and lateral bending ROM (LB-ROM). Each instrumented specimen was compared its matched intact specimen to generate a ROM ratio. Differences in ROM ratios were compared by ANOVA. Tukey's HSD was used for post-hoc analyses.

Results: The intact specimen demonstrated 8.69+/-3.90 degrees of FE-ROM, 3.69+/-1.94 degrees of AX-ROM, 5.72+/-2.24 degrees of LB-ROM. FSA FE-ROM ratio was 1.05+/-0.54. CS FE-ROM ratio was significantly lower (Figure 2; 0.36+/-0.12, p< 0.001) and EC was lower still (0.29+/-0.15, p< 0.001). The difference between CS and EC in FE-ROM ratio was not significant (p=0.91). There were no differences in AX-ROM or LB-ROM ratios (p=0.85, 0.62, respectively).

Conclusions: CS and EC appear to be significantly more stable constructs compared to FS with FE-ROM. The three constructs appear equal with AX-ROM and LB-ROM. Reconstruction of the load transfer mechanism to the pelvis via the L5 endplate appears to be important in total sacrectomy reconstruction.

Figure 1

Figure 2