Biomechanical consequences of cervical spondylectomy versus corpectomy.

Objective: To evaluate the differences in spinal stability and stabilizing potential of instrumentation after cervical corpectomy and spondylectomy.

Methods: Seven human cadaveric specimens were tested: 1) intact; 2) after grafted C5 corpectomy and anterior C4-C6 plate; 3) after adding posterior C4-C6 screws/rods; 4) after extending posteriorly to C3-C7; 5) after grafted C5 spondylectomy, anterior C4-C6 plate, and posterior C4-C6 screws/rods; and 6) after extending posteriorly to C3-C7. Pure moments induced flexion, extension, lateral bending, and axial rotation; angular motion was recorded optically.

Results: After corpectomy, anterior plating alone reduced the angular range of motion to a mean of 30% of normal, whereas added posterior short- or long-segment hardware reduced range of motion significantly more (P < 0.003), to less than 5% of normal. Constructs with posterior rods spanning C3-C7 were stiffer than constructs with posterior rods spanning C4-C6 during flexion, extension, and lateral bending (P < 0.05), but not during axial rotation (P > 0.07). Combined anterior and C4-C6 posterior fixation exhibited greater stiffness after corpectomy than after spondylectomy during lateral bending (P = 0.019) and axial rotation (P = 0.001). Combined anterior and C3-C7 posterior fixation exhibited greater stiffness after corpectomy than after spondylectomy during extension (P = 0.030) and axial rotation (P = 0.0001).

Conclusion: Circumferential fixation provides more stability than anterior instrumentation alone after cervical corpectomy. After corpectomy or spondylectomy, long circumferential instrumentation provides better stability than short circumferential fixation except during axial rotation. Circumferential fixation more effectively prevents axial rotation after corpectomy than after spondylectomy.