One-year CT evaluation of fusion in adult spinal deformity using supplemental anterior lumbar interbody fusion.

PURPOSE

The purpose of this study was to report the one-year posterior fusion rate in patients with adult spinal deformity (ASD) undergoing posterior spinal fusion (PSF) with supplemental lumbar interbody fusion (LIF).

METHODS

Patients with ASD who underwent PSF with supplemental ALIF and/or XLIF between October 2021 and December 2023 were prospectively enrolled. Fusion was assessed using fine-cut CT scans with Metal Artifact Reduction (MAR) and multi-planar reconstruction (MPR) one year after surgery, and each level was graded for interbody and posterolateral fusion (Glassman Classification). Interbody and posterolateral fusion were reported as individual fusion grades (1-4) and dichotomized as; Fusion (1-2) and non-fusion (3-4).

RESULTS

Of 57 enrolled patients, 50 had CT scans performed with 53 ALIF and 48 XLIF-treated levels. The mean age was 63.5 ± 11.6 years and 36 (72%) were female. Solid fusion of the interbody and/or posterolateral fusion assessed at the level of the LIF was obtained in 48 (96%) of the patients. Solid interbody fusion was significantly more frequent with ALIF; 49 (93%) compared to XLIF; 26 (54%) (p < 0.001). Additionally, the fusion score was significantly different with ALIF; median 1 [IQR 1-1] compared to XLIF median 2 [IQR 1-3] (p < 0.001). The posterolateral fusion rates did not differ significantly between ALIF (92%) and XLIF (88%) levels/segments (p = 0.470). Additionally, median Glassman scores for posterolateral fusion were similar: ALIF 1 [1, 1] vs. XLIF 1 [1, 2] (p = 0.370). Mechanical failure was observed in 9 patients (Displacement of the cage: 3, sacral screw loosening: 3, screw loosening: 1, rod breakage: 2) four of which were at the level of the LIF. Three patients underwent revision surgery at the level of the LIF.

CONCLUSION

Patients undergoing posterior instrumented fusion for ASD with supplemental anterior interbody fusion obtained high fusion rates assessed with CT. Higher rates of interbody fusion were observed in ALIF than in XLIF-treated levels. Despite differences in interbody fusion, similar posterolateral fusion was seen one year after surgery.