Effect of Posterior Element Removal in Thoracic and Lumbar Spine Segments With and Without Compromised Vertebral...

Technical constraints often require biomechanical testing of spine segments after removal of the vertebral posterior elements, potentially introducing bias in the biomechanical outcomes. This study aimed to evaluate the effects of posterior elements removal on the biomechanics of thoracic and lumbar spine segments when axially compressed and to investigate whether these effects differ between control vertebrae (without CT evidence of pathological alterations) and vertebrae with compromised microstructure due to metastatic lesions.

Fourteen thoracolumbar spine segments harvested from donors with spinal metastases were tested under axial compression within the elastic regime. Each specimen was tested before and after posterior elements removal, up to a specimen-specific reference force corresponding to a compressive strains of 2000 microstrain. Surface strain fields were quantified using three-dimensional digital image correlation. Reference force, stiffness and strain heterogeneity were evaluated.

Posterior element removal did not significantly affect the reference force or stiffness in thoracic specimens. By contrast, lumbar specimens required a lower reference force (- 43%) to reach the same strain and exhibited reduced stiffness (- 20%) following posterior elements removal. Strain heterogeneity increased only in lumbar specimens. Control vertebrae were minimally affected, whereas metastatic vertebrae exhibited a tendency towards heterogeneous strain pattern following posterior element removal.

Posterior element removal introduces mechanical artefacts in lumbar spine testing under axial compression, while having minimal impact on thoracic segments. Therefore, caution is warranted when comparing biomechanical data obtained from intact and posterior-element-removed lumbar specimens, particularly in the presence of compromised bone microstructure due to metastatic lesions.