The biomechanics of long versus short fixation for thoracolumbar spine fractures.

STUDY
DESIGN: Literature review.
OBJECTIVE: Provide an overview of biomechanical strengths and weaknesses of long and short fixation constructs applied in thoracolumbar fractures, along with a discussion of specific indications for selecting an instrumentation construct for a given fracture. SUMMARY OF BACKGROUND DATA: Previous clinical and biomechanical studies have shown that segmental spinal instrumentation provides superior torsional, axial, and sagittal stability relative to nonsegmental systems. Multilevel fixation (long constructs) has proven reliable and effective in treating thoracic injuries, with or without anterior reconstruction. Short-segment pedicle instrumentation (short constructs) have proven effective in stabilizing thoracolumbar and lumbar fractures while limiting the disruption of lower lumbar motion segments. Loss of anterior column integrity leads to fixation failure when short constructs are not supplemented with further fixation or an anterior reconstruction.
METHODS: Review of the applicable clinical and biomechanical literature.
CONCLUSIONS: Long constructs serve well in thoracic and thoracolumbar fractures, while short-segment fixation offers advantages in selected thoracolumbar and lumbar fractures. Anterior column integrity determines the risk of sagittal collapse and kyphosis at the thoracolumbar junction. Recognition of fundamental biomechanical principles is necessary to make either construct work reliably.