In vitro radiographic characteristics and biomechanical properties of the canine lumbar vertebral motion unit after lateral corpectomy, mini-hemilaminectomy and hemilaminectomy

Summary

Objective: The purpose of this study was to assess the effect of three surgical procedures (left lateral corpectomy [LC], LC plus mini-hemilaminectomy [LC-MH], and LC plus hemilaminectomy [LC-H]) on the biomechanics and intervertebral collapse of a lumbar vertebral motor unit (VMU).

Methods: Six canine cadaveric first and second lumbar vertebrae (L1-L2) VMU were retrieved. Range-of-motion (ROM) was measured while a custom-built mechanical simulator applied 3 Nm torque in lateral bending, flexion and extension to the intact VMU and following the three surgical procedures (LC, LC-MH, LC-H) performed sequentially. Radiographs were taken with and without 3 kg axial compression at each step.

Results: Left lateral corpectomy and LC-MH significantly increased the ROM in left lateral bending and total lateral bending. A LC-H significantly increased the ventral, left, right, total lateral, and total dorsoventral ROM. Significant intervertebral collapse was observed after LC-H with and without axial compression, and after LC and LC-MH, but only with axial compression.

Clinical significance: A LC induces significantly increased ROM in lateral bending to the side of the surgery and in total lateral ROM. Extending the LC to a LC-MH does not change the spinal column stability compared to LC alone, while it provides better access to the spinal canal. The LC-H further destabilizes the VMU. The finding of intervertebral collapse following these surgical procedures confirms the importance of the intervertebral disc and articular facet in the maintenance of spatial integrity.

Keywords

Corpectomy - mini-hemilaminectomy - hemilaminectomy - biomechanical.

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