Radiographic Assessment of Anterior Titanium Mesh Cages

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Abstract
Carbon fiber and titanium cage implantation for anterior column support during spinal fusions is an alternative to the use of more traditional structural allografts and autografts. The authors report instrumentation and cage failure for patients who underwent spinal fusion with structural titanium mesh cages implanted into the anterior column a minimum of 2 years after surgery. They wanted to determine whether plain radiographic techniques can be used to critically assess disk space and corpectomy fusions after implantation of these radioopaque cages. Fifty patients having undergone spinal fusions using structural titanium mesh cages in the anterior column had 99 anterior levels fused with at least 1 (maximum of 2) titanium mesh cage, resulting in a total of 131 cages used. The cages were examined for evidence of settling, migration, or failure. The anterior and posterior instrumentation was assessed for evidence of failure, and the spine was examined for evidence of successful fusion. Radiographic cage settling (>2 mm) into the vertebral body end plates was observed, but cage migration or failure were not. An average lordotic correction of 10° was observed, with loss of correction into kyphosis from immediately after operation to final follow-up averaging 2°. As an average of all reviewers, using a strict radiographic fusion assessment, definite or probable anterior fusion was graded at 81% of the levels, probably not or no at 5% of the levels, and could not be assessed at 14% of the levels. Definite or probable posterior fusion as an average of all reviewers was graded at 44% of the posterior fusion levels, questionable at 4%, no at 5%, and could not be assessed at 47%. The use of anterior-only, posterior-only, or anterior and posterior instrumentation with structural titanium mesh cages in the anterior spine along with proper autogenous bone grafting techniques provided anterior column support with a low rate of radiographic complications. Acceptable anterior spinal fusion rates, as assessed by a consensus agreement of reviewers, were observed primarily by evaluation of the fusion mass around the cages (extracage fusion), because intracage fusion was difficult to assess.