Pre-Operative Hemoglobin is a Predictor for Length of Stay, Disposition, and Reoperation in Long-Segment Posterior Spinal Fusion for Adult Spinal Deformity: an Adjusted Analysis

Introduction: Baseline pre-operative hemoglobin is an important factor in long-segment posterior spinal fusion (PSF) for adult spinal deformity (ASD). This study aimed to evaluate the association between baseline pre-operative hemoglobin levels and post-operative hospital and intensive care unit (ICU) length of stay (LOS), as well as overall outcomes in long-segment PSF for ASD.

Methods: The design and reporting of this study were supported by the STROBE and the TRIPOD+AI guidelines. Patients undergoing PSF were identified in our institutional deformity registry. Inclusion criteria were patients with PSF of 6 or more vertebrae, thoracolumbosacral region, and ASD. Patients with PSF of less than 6 levels, a cervical component in the fusion construct, and non-deformity indication were excluded. Demographics, baseline, pre-operative, surgical, and post-operative characteristics were extracted. Adjusted generalized linear models with cubic splines were performed to investigate relationships. Covariates included baseline characteristics, demographics, comorbidities and surgical details.

Results: 598 patients were included in the analysis. In our cohort mean pre-operative hemoglobin was 13.1 ± 1.9 g/dL, mean age was 59.9 ± 14.9 years, 389 (65.1%) were female, mean number of PSF levels was 10.7 ± 3.0, mean hospital LOS was 8.0 ± 6.8 days, and mean ICU LOS was 2.6 ± 3.7 days. The expected hospital LOS significantly decreased non-linearly as pre-operative hemoglobin increased until 13.5 g/dL adjusted while remaining relatively constant thereafter (p < 0.001). The expected ICU LOS significantly decreased non-linearly as pre-operative hemoglobin increased until 13.0 g/dL adjusted and remained relatively constant thereafter (p < 0.001). Patients with preoperative hemoglobin < 13 had significantly lower likelihood of discharge to home and higher reoperation rates.

Conclusion : Baseline pre-operative hemoglobin was a significant non-linear predictor for hospital and ICU LOS in long-segment PSF for ASD up to a threshold of 13.5 g/dL. Anemic preoperative hemoglobin also seems to portend worse disposition and greater likelihood of reoperation.