Compressive loading of the spine may affect the spinal canal encroachment of burst fractures

Spinal canal encroachment of burst fractures under different compressive loading.

To assess whether the application of different compressive loads affect the spinal canal encroachment (SCE) of thoracolumbar burst fractures and to relate any significant encroachment differences to the fracture morphology.

The SCE is an important part of the evaluation process of thoracolumbar burst fractures. It is, however, not well understood how a variation in spinal internal loads resulting from a change in patient posture may affect the SCE after a burst fracture. The application of a compressive load on fractured vertebrae may displace bony fragments further into the canal and increase the encroachment.

Ten thoracolumbar functional spinal units harvested from mature minipigs and compressed to create burst fractures were imaged by computed tomography under 3 loading conditions: without compressive force and with 2 compressive forces analogous to the load expected in vivo. SCE were measured for all loading cases and compared with each other to identify whether they systematically changed between loading cases and to discriminate which specimens were affected by an increase in the loading.

The application of a compressive loading did not systematically increase the SCE. However, specimens with a large bony fragment originating from the superior and posterior aspect of the vertebral body with a centrifugal orientation had a significant increase of SCE when loaded.

An increase in spinal internal loads resulting from a change in the patient posture may increase the SCE of burst fracture. Measurement of the SCE should take into account the bony fragment distribution of burst fracture.