Factors that influence long term instrumentation stability in patients with unstable thoracolumbar injuries

Pedicle screw fixation is frequently used to treat unstable thoracolumbar injuries; however, the rate of instrumentation failure remains considerable. The primary contributing factor leading to instrumentation failure is poor bone quality. On the other hand, some evidence suggests that surgical tactics can influence long-term instrumentation stability.

To assess factors that influence the stability of spinal instrumentation in patients with thoracolumbar injuries.

This study is a non-randomized single center ambispective evaluation of 204 consecutive patients (117 men; 87 women) with unstable thoracolumbar injuries. All patients underwent either stand-alone or combined with anterior column reconstruction instrumentation. In cases with spinal cord and nerve root injuries, either posterior or anterior decompression were performed. Patients with pedicle screw loosening were identified via computed tomography imaging. Out of those, cases with clinically significant instrumentation failure were registered.

The rate of pedicle screw loosening detected by computed tomography was inversely correlated with bone radiodensity figures and an increased association with the number of instrumented levels, residual kyphotic deformity, laminectomy, and lumbosacral fixation. Intermediate screws and anterior reconstruction were associated with a clinically relevant decreased risk of pedicle screw loosening development. Either complete or partial posterior fusion within instrumented levels was capable of decreasing instrumentation failure risk, while extensive decompression with laminectomy and at least one-level total facetectomy were associated with an increased risk of instrumentation failure. Anterior decompression does not have a negative impact on instrumentation stability.

Intermediate screws, anterior reconstruction and posterior tension band preservation are associated with decreased rates of instrumentation instability development. Posterior fusion is beneficial in terms of instrumentation failure prevention.