Porous tantalum cage for interbody fusion of the cervical spine: assessment of fusion in a long term study. Preliminary results

Introduction/Aim Porous tantalum cages (PTC) have been satisfactorily used for about 15 years for both anterior discectomy and fusion (ACDF), and corpectomy. However, assessment of fusion with PTC may be difficult due to total radio-opacity, with concern about radiolucency at the bone-cage interface, which might anticipate non-union. We assessed the long-term fusion rate with PTC cervical cages, and analysed the significance of lucency in predicting non-fusion. Materials and methods The authors retrospectively analyzed a consecutive series of 78 patients who underwent ADCF or corpectomy and fusion with PTCs from 2005 to 2014 for degenerative or traumatic disorders. There were 43 males and 35 females from 22 to 80 years of age (average 50.9). Patients underwent 1-, 2-, or 3-level ACDF with TM-100 or TM-S cages, or 1 or 2 corpectomies and fusion with VBR-11 cages (Zimmer Spine, Minneapolis, MN). Outcome was evaluated with Odom’s scale, and X-rays were obtained a few days to 2 years after surgery.Most patients were recalled for long-term follow-up up to 9 years after surgery. X-rays were evaluated for segmental lordosis, cage subsidence, bone-cage interface lucency, bony bridges, and residual motion at fused levels. Fusion was defined as bony bridging, and/or <3° variation of Cobb’s angle on functional X-rays, and/or absence of radiolucent line exceeding 50% of bone-cage interface. Results Clinical results were satisfactory overall. Long term fusion rate was 98%. Although radiolucency was seen in some cases in the first few weeks or months, it disappeared in most cases and it was not predictive of nonunion. There were no reoperations nor infections. Discussion A radiolucent rim around PTCs does not appear to predict nonunion. When present, it resolved with time and was not associated with patient discomfort or pseudoarthrosis. Although fusion may not be seen in the early stage after PTC implantation, almost all patients eventually show patent fusion with bony bridging and remodelling. Conclusion Although fusion is difficult to assess in some cases, PTCs are safe and effective in achieving interbody fusion of the cervical spine.