Comparison of fusion mass thickness, BMD, and screw length in 6 adult spinal deformity patients treated with FMS fixation during revision spine surgery.
| Case | Level | Fusion Mass Thickness (mm) | Fusion Mass BMD (HU) | Screw Length (mm) | Complications Related to FMS Placement | FMS Loosening, Breakage, or Pseudarthrosis at Latest Follow-Up |
| 1 | T12 | 23.7 | 315 | 40 | None | None |
| 1 | L2 | 24.4 | 475 | 35 | None | None |
| 2 | T8 | 15.8 | 628 | 40 | None | None |
| 2 | T10 | 13.3 | 544 | 40 | None | None |
| 3 | T9 | 8.6 | 574 | 40 | None | None |
| 3 | T10 | 10.4 | 496 | 35 | None | None |
| 3 | T11 | 12.8 | 378 | 40 | None | None |
| 4 | T12 | 18.7 | 500 | 35 | Spinal canal breach | None |
| 4 | L1 | 19.4 | 378 | 35 | None | None |
| 5 | L2 | 11.1 | 455 | 40 | None | None |
| 5 | L5 | 13.9 | 372 | 40 | None | None |
| 6 | T9 | 10.7 | 156 | 30 | None | None |
| 6 | T10 | 14.3 | 284 | 30 | None | None |
| 6 | T11 | 19.6 | 215 | 25 | None | None |
| 6 | T12 | 16.5 | 188 | 25 | None | None |
| Mean ± SD | _ | 15.5 ± 4.8 | 397 ± 144 | 35 ± 5.5 | _ | _ |
Abbreviations: BMD, bone mineral density; CT, computed tomography; FMS, fusion mass screw; HU, Hounsfield units.
Note: There was no evidence of FMS loosening, breakage, or pseudarthrosis on CT at an mean of 2.2 years of follow-up (range: 1.4 to 3.1 years). On postoperative CT, 1 out of 15 screws had a low-grade breach (<2 mm) into the canal (Case 4 at T12). There were otherwise no complications related to FMS placement.