Clinical StudyReliability and accuracy of fine-cut computed tomography scans to determine the status of anterior interbody fusions with metallic cages
Introduction
Anterior lumbar interbody fusion (ALIF) is a widely used technique for lumbar arthrodesis [1], [2], [3], [4]. Reported rates of fusion vary because of differences in surgical technique and criteria used to determine fusion [5], [6], [7], [8], [9], [10]. Computed tomography (CT) scanning has become the method of choice [11], [12], [13], [14], [15] because it provides osseous detail and allows reformatting to produce images in the sagittal and coronal planes. Studies have shown that CT is superior to plain radiographs in evaluating ALIF, particularly in the presence of metallic interbody devices [14], [16]. However, animal studies suggest that CT scans may overestimate the extent of fusion [14]. This study was done to assess the reliability and accuracy of fine-cut CT with coronal and sagittal reconstruction views in evaluating ALIF with metallic cages using surgical exploration as the reference standard.
Section snippets
Methods
Forty-nine consecutive patients who underwent revision surgery after an anterior interbody fusion with metallic cages and had a fine-cut CT scan before revision were included. Forty-two patients had a preoperative diagnosis of pseudoarthrosis and seven had adjacent level degeneration. Five experienced fellowship-trained spine surgeons who were not aware of the findings on surgical exploration evaluated the pre-revision CT scans and classified the levels as fused or not fused. Fine-cut axial
Results
There were 26 males and 23 females with a mean age of 43 years (range 21–65 years). There were 27 smokers. Average time from the first surgery to the revision surgery was 22 months (range 3–73 months). Thirty-nine of 69 levels were found to have a nonunion on exploration, giving a per-level prevalence of 56.5%. There were 33 single-level fusions, 13 two-level, and 3 three-level fusions. There were 8 previous fusions at L3–L4, 25 at L4–L5, and 36 at L5–S1. Three different cages were used: the
Discussion
Review of literature shows that there are no universally accepted radiological criteria for assessing interbody fusion [19], [20], [21] using either plain radiographs or CT scans. Metallic implants, which are radiopaque and can produce artifacts, add to the difficulty in adequately assessing imaging studies to determine the presence of fusion. McAfee [17] considers bone formation in front of the cage, across the anterior margin of the disc space as the most reliable indicator of a solid
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Cited by (0)
Research support received from the Lumbar Spine Study Group through Medtronic Sofamor Danek and from Norton Healthcare.
FDA device/drug status: not applicable.
Authors acknowledge a financial relationship (research support from Medtronic Sofamor Danek [SDG], consultants for Medtronic Sofamor Danek [BRS, JDS, and SDG], stockholder and board member of Pioneer K2 [MFG], other support from Medtronic Sofamor Danek [JDS and SDG] and other support from Stryker [MFG]), which may indirectly relate to the subject of this research.