The Impact of Age and Graft Type on Foot and Ankle Arthrodesis Fusion Success

Abstract

Category: Ankle; Ankle Arthritis; Basic Sciences/Biologics; Hindfoot Introduction/Purpose: A recent survey of 100 international foot and ankle orthopaedic surgeons revealed that patient age greater than 60 years is not considered to be a significant risk factor for nonunion following foot and ankle arthrodesis. This finding was surprising as published basic science research shows that autologous bone graft used during fusion surgery may be less effective when harvested from older patients due to both diminished osteogenic potential and migration capacity of mesenchymal stem cells. The purpose of this study was to evaluate the impact of patient age and graft type on fusion rates following hindfoot and ankle arthrodesis. Methods: A Level 1 clinical trial was performed comparing fusion success in 397 hindfoot or ankle arthrodesis subjects (597 joints) supplemented with either autograft or an osteoinductive recombinant human protein derived growth factor (rhPDGF- BB/β-TCP) bone graft substitute. Fusion status was determined using computed tomography, with fusion defined as evidence of at least 50% osseous bridging. In this secondary analysis of that dataset, the odds of fusion success were compared for joints in autograft subjects older or younger than the following age thresholds: 55, 60, 65, 70 and 75 years. This analysis was then repeated for joints in rhPDGF-BB/β-TCP subjects. Finally, odds of fusion success were also compared for the autograft and rhPDGF-BB/β- TCP groups for subjects older than each threshold age. Results: Joints in autograft subjects younger than 60 and 65 years exhibited over two times the odds of fusion as those in older subjects (60 years: OR 2.24, p=0.003; 65 years: OR 2.74, p<0.001). There was no significant difference for other intervals (55 years: OR 1.45, p=0.106; 70 years: 1.64, p=0.096; 75 years: OR 1.28, p=0.335). Interestingly, there was no significant difference for the rhPDGF-BB/β-TCP group at any threshold (55 years: OR 0.86, p=747; 60 years: OR 0.86, p=0.739; 65 years: 1.08, p=0.367; 70 years: 0.94, p=0.588; 75 years: OR 0.70, p=0.809). When odds of fusion were compared for the two groups in subjects older than each age threshold, rhPDGF-BB/β-TCP had approximately two times the odds of fusion success for all except 55 years (Figure 1). Conclusion: This study indicates that age is an identifiable and potentially concerning risk for nonunion following hindfoot or ankle arthrodesis. These findings are in contrast to the wider perception of the surgeon community, as documented in the published survey. Notably, patients over the age of 60 years who are supplemented with autograft have statistically lower odds of fusion compared to those younger, a difference not seen with the use of recombinant technology. This analysis suggests that use of rhPDGF-BB/β-TCP as an alternative bone healing adjunct may help mitigate the risk of nonunion when these procedures are performed in the elderly population.