Short segment transpedicular Cotrel-Dubousset instrumentation: a porcine corpectomy model

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Spinal Fusion

Background:

• Cotrel-Dubousset instrumentation is used for spinal stabilization.
• Laminar hooks are sometimes added to enhance fixation.
• The effect of laminar hooks on construct stiffness, especially after corpectomy, requires further biomechanical evaluation.

Purpose of the Study:

• To evaluate the changes in stiffness of a three-level spinal construct with transpedicular Cotrel-Dubousset instrumentation.
• To assess the impact of adding offset laminar hooks to the instrumentation.
• To determine the biomechanical effects in both intact and corpectomy models.

Main Methods:

• Porcine lumbar spines (L-1 to L-5) were tested in three configurations: intact, instrumented, and instrumented after L-3 corpectomy.
• Instrumentation included transpedicular Cotrel-Dubousset screws and rods, with and without offset laminar hooks.
• Constructs were subjected to axial compression and torsion testing using a materials testing machine.

Main Results:

• Fully instrumented intact spines showed a significant increase in stiffness (28.0% torsion, 23.1% axial compression).
• Adding laminar hooks to instrumented intact spines did not significantly alter stiffness.
• In the corpectomy model, adding laminar hooks significantly increased stiffness (26.9% axial compression, 28.1% torsion).

Conclusions:

• Transpedicular Cotrel-Dubousset instrumentation significantly increases spinal construct stiffness.
• Offset laminar hooks provide a significant stiffness increase in a corpectomy model, but not in an intact spine model.
• The enhanced stiffness from laminar hooks in corpectomy models may help mitigate postoperative kyphosis in treating lumbar burst fractures.