Structural stability of different reconstruction techniques following total sacrectomy: a biomechanical study.

Background: The biomechanical stability of spino-pelvis structure after varying reconstruction methods following total sacrectomy remains poorly defined. The objective of this study was to compare the structural stability of different reconstruction techniques.

Methods: Six fresh human cadavers (L2-pelvis-femora) were used to compare biomechanical stability after reconstruction using four different techniques: (1) sacral rod reconstruction; (2) bilateral fibular flap reconstruction; (3) four-rod reconstruction; and (4) improved compound reconstruction. After total sacrectomy, the construction was carried out using each method once in each cadaver. Structural stiffness was evaluated by linear and angular ranges of motion. L5 relative shift-down displacement, abduction angle on the coronal plane and rotation angle on the sagittal plane, were calculated based on displacement of the identification point under 500N axial loading. Overall stiffness was estimated using load displacement curve.

Findings: Improved compound reconstruction resulted in significantly higher stiffness than all three other techniques. The structural stability following bilateral fibular flap reconstruction was superior to that after sacral rod reconstruction. Four-rod reconstruction achieved worst stability due to the lack of anterior bracing applied in three other methods.

Interpretation: Improved compound reconstruction produces optimal structural stability after total sacrectomy. This finding suggests that both anterior bracing and alternation of screw trajectory are important in achieving optimal structural stability.