A 24-month retrospective update: follow-up hospitalization charges and readmissions in US lumbar fusion surgeries using a cellular bone allograft (CBA) versus recombinant human bone morphogenetic protein-2 (rhBMP-2)

BACKGROUND: The objectives of this study were to build upon previously-reported 12-month findings by retrospectively comparing 24-month follow-up hospitalization charges and potentially-relevant readmissions in US lumbar fusion surgeries that employed either recombinant human bone morphogenetic protein-2 (rhBMP-2) or a cellular bone allograft comprised of viable lineage-committed bone cells (V-CBA) via a nationwide healthcare system database. METHODS: A total of 16,172 patients underwent lumbar fusion surgery using V-CBA or rhBMP-2 in the original study, of whom 3,792 patients (23.4%) were identified in the current study with all-cause readmissions during the 24-month follow-up period. Confounding baseline patient, procedure, and hospital characteristics found in the original study were used to adjust multivariate regression models comparing differences in 24-month follow-up hospitalization charges (in 2020 US dollars) and lengths of stay (LOS; in days) between the groups. Differences in potentially-relevant follow-up readmissions were also compared, and all analyses were repeated in the subset of patients who only received treatment at a single level of the spine. RESULTS: The adjusted cumulative mean 24-month follow-up hospitalization charges in the full cohort were significantly lower in the V-CBA group ($99,087) versus the rhBMP-2 group ($124,389; P < 0.0001), and this pattern remained in the single-level cohort (V-CBA = $104,906 vs rhBMP-2 = $125,311; P = 0.0006). There were no differences between groups in adjusted cumulative mean LOS in either cohort. Differences in the rates of follow-up readmissions aligned with baseline comorbidities originally reported for the initial procedure. Subsequent lumbar fusion rates were significantly lower for V-CBA patients in the full cohort (10.12% vs 12.00%; P = 0.0002) and similar between groups in the single-level cohort, in spite of V-CBA patients having significantly higher rates of baseline comorbidities that could negatively impact clinical outcomes, including bony fusion. CONCLUSIONS: The results of this study suggest that use of V-CBA for lumbar fusion surgeries performed in the US is associated with substantially lower 24-month follow-up hospitalization charges versus rhBMP-2, with both exhibiting similar rates of subsequent lumbar fusion procedures and potentially-relevant readmissions.