Article
A simple fusion score for dorsal spinal instrumentation
Ein einfacher Score zur Beurteilung der Fusion nach dorsaler spinaler Instrumentation
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Authors
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Christoph Bettag
- Universitätsmedizin Göttingen, Neurochirurgie, Göttingen, Deutschland
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Christian von der Brelie
- Universitätsmedizin Göttingen, Neurochirurgie, Göttingen, Deutschland
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Veit Rohde
- Universitätsmedizin Göttingen, Neurochirurgie, Göttingen, Deutschland
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Bawarjan Schatlo
- Universitätsmedizin Göttingen, Neurochirurgie, Göttingen, Deutschland
| Published: | June 4, 2021 |
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Outline
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Objective: The assessment criteria for successful fusion after spine surgery vary widely. While some authors content themselves with a lack of implant loosening, others request imaging evidence of bone bridge formation, e.g. on radiographs or even on computed tomography.
The aim of this study was to assess imaging after posterior lumbar instrumentation in order to devise a simple and reproducible system to report successful or absent fusion.
Methods: We performed a retrospective chart and imaging review of patients who underwent lumbar spinal instrumentation for degenerative disease. The analysis was based on demographic and radiographic parameters including age, sex, indication for surgery, number of operated segments. On postoperative CT scans with a mean follow-up of 30±25 months, we assessed three criteria pertaining to anterior column fusion (interbody fusion according to the Brantigan Fraser score, points 0-2), dorsolateral fusion (facet joint and laminar bridging according to the Lenke score, points 0-2) and implant stability (absent signs of loosening 2 points, halo sign < 2mm 1 point, large halo sign or implant dislocation 0 points) resulting in a composite fusion score (CFS) from 0-6 points. A higher score represents a more solid fusion, a lower score reflects lack thereof. We evaluated the predictive power of this score for implant failure requiring a second surgery.
Results: 145 patients (86 female, 59%) with a mean age of 59.8±13 years undergoing posterior lumbar instrumentation in 170 segments were analyzed. Implant loosening was predicted by low bone density and absent interbody and posterolateral fusion (CFS ≤ 4 points, p≤ 0.001). Low bone density predicted absent interbody and posterolateral fusion (p≤ 0.001). Revision surgery at follow-up was lower in the group with more favorable fusion scores (OR 0.30; CI95% 0.14-0.64; p=0.002).
Conclusion: Among all studied parameters, only a high fusion score reliably predicted good (revision-free) outcome at an average of 30 months after lumbar instrumentation for degenerative disease. Based on this work, we propose an objective scoring tool to report fusion outcomes in lumbar spine surgery.
