Long-Term Follow-Up of Hindfoot and Ankle Arthrodesis Procedures Supplemented with an Autologous Bone Graft Alternative (rhPDGF)

Abstract

Category: Hindfoot; Ankle Introduction/Purpose: Recombinant human platelet-derived growth factor (rhPDGF) is commonly used in hindfoot and ankle arthrodesis as an alternative to autologous bone graft, the current gold standard grafting material. The largest randomized controlled trial ever conducted in foot and ankle arthrodesis showed that rhPDGF was associated with similar successful radiographic and clinical outcomes to those of autologous bone graft at 24 months. The objective of this study was to determine if outcomes remained similar for these two grafting materials at long-term follow-up. Methods: All 37 sites (414 subjects) from the previously conducted randomized controlled trial examining outcomes for hindfoot and ankle arthrodesis supplemented with either rhPDGF or autologous bone graft (randomized 2:1) were invited to return for a single visit occurring at a minimum follow-up of 60 months. All returning subjects who provided consent were evaluated with computed tomography (CT) scans, American Orthopaedic Foot & Ankle Society (AOFAS) Scores, Foot Pain and Disability (FFI) Scores, and visual analog scores (VAS) assessing fusion site, weight bearing, and graft harvest site pain. Because final fusion status was dependent upon the status exiting the original trial, maintenance or improvement of fusion status was the key focus of the study. The change in baseline from all other outcomes measures were also compared between the two groups. Results: A total of 169 subjects (109 rhPDGF, 60 autologous) from 26 sites completed a follow-up visit at a mean 9.1 years (7.7- 10.9).The rate of maintenance or improvement of CT fusion status was statistically noninferior for subjects in the rhPDGF group compared to the autologous bone graft group (92.7% vs. 95.0%,p=0.021), Total AOFAS Scores (74.9+16.7 vs. 77.2+13.9, p<0.001), FFI Scores (22.7+21.7 vs. 16.5+12.0, p<0.001), weight bearing pain change from baseline (-46.0+33.4 vs. -51.0+33.1, p=0.002), and fusion site pain change from baseline (-34.0+33.6 vs. -34.0+32.4, p<0.001). There were no differences in secondary surgical interventions with the most common reasons being hardware complications (7.3% vs. 8.3%) and non-union (4.6% vs. 1.7%). There were no significant differences in the rates of medically relevant adverse events. In the autologous bone graft group, 3 (5%) subjects continued to experience clinically relevant pain (VAS>20) at their graft harvest site. Conclusion: The outcomes of rhPDGF in hindfoot or ankle arthrodesis were statistically noninferior to those of autologous bone graft at a mean follow-up of 9.1 years. Over 92% of rhPDGF subjects maintained or improved their fusion status. Similarly, the baseline change for all VAS and functional outcomes were non-inferior for the two groups. The exception was clinically significant graft harvest site pain, which only existed in the autologous bone graft group. The results of this study demonstrate that rhPDGF used in hindfoot and ankle arthrodesis is associated with similar long-term radiographic, functional, and clinical outcomes as autologous bone.