Functional Evaluation of the Operated Lumbar Spine with Axial Loaded Computed Tomography (AL-CT)

Abstract

This study evaluated Axial Loaded-CT (AL-CT) of an operated spine (with and without instrumentation) to assess the limits and possibilities of this diagnostic imaging procedure.

We considered 100 patients divided into two groups: Group 1: 89 patients, evaluated only post-operatively; Group 2: 15 patients who underwent AL-CT before and after lumbar spine instrumentation with different devices, for the purpose of correcting spinal instability. Some patients came at first observation after previous conventional surgery and were enrolled in both groups.

A satisfactory evaluation of the spine was attained in all the patients, even in the presence of beam-hardening artifacts associated with stainless steel posterior fixation.

The evaluation of the conventionally operated spine disclosed the residual stability of the studied segments and allowed a comparison of any abnormal intersegmental movement. The comparison between pre- and post-surgical scans in the instrumented spines enabled the evaluation of: the stability of the surgically stabilized segment; the “internal” stability of the implant; the relative stability of the adjacent spinal levels; the degree of correction of the presurgical instability/deformity.

AL-CT seems to be able to image the operated spine clearly, even when instrumented, showing even minimal residual abnormal movements at and adjacent to the operated level(s). The functional aspects of the examination (axial loading) allowed a good evaluation of the post-surgical load transmission patterns even in the presence of large stainless steel implants.