Impact of Bone Grafting and Graft Type on Fusion and Patient-Reported Outcomes Following Subtalar Arthrodesis: A Multicenter Retrospective Cohort Study.

Abstract

Background: The role of bone grafting in subtalar joint arthrodesis (SJA) remains controversial. This study aimed to compare clinical and radiographic outcomes of SJA performed with and without bone graft and to evaluate the influence of different graft types on fusion and functional results.

Methods: A multicenter retrospective observational study was conducted including 66 patients who underwent isolated SJA between 2023 and 2025. Patients were divided into graft (n = 51) and no graft (n = 15) groups. A subgroup analysis compared autologous, fresh frozen allogeneic, and commercial allogeneic grafts. Outcomes included osseous union, time to union, complications, and functional scores (AOFAS, FAAM-ADL, and FAAM-Sports). Multivariable regression and ROC analyses were performed to identify independent predictors of nonunion and delayed union.

Results: Overall, the union rate was 90.9%. Union was achieved in 92.2% of grafted patients and 86.7% of nongrafted patients (p = 0.612). Bone graft use was not independently associated with union, complications, or time to union in the adjusted exploratory analyses. Increasing age and BMI were independently associated with a prolonged time to union. ROC analysis identified age ≥ 60 years as a predictor of nonunion (AUC 0.782) and age ≥ 59 years and BMI ≥ 25.9 kg/m² as predictors of delayed union. Both groups showed significant postoperative improvements in all functional scores (all p < 0.001). Autologous graft was associated with higher postoperative functional scores, although this finding should be interpreted cautiously given potential baseline differences and selection bias.

Conclusions: In isolated SJA performed in a well-aligned hindfoot, high union rates and significant functional improvement were achieved regardless of bone graft use. However, due to the retrospective, nonrandomized design and limited number of nonunion events, no definitive conclusions can be drawn regarding the routine necessity or superiority of bone grafting. Though, bone graft use appeared to be associated with improved functional outcomes in selected higher risk patients, although these findings should be interpreted cautiously given the exploratory nature of the analysis. All subgroup and threshold analyses should be interpreted as exploratory.