Prospective, Randomized, Multi-Center Feasibility Trial of rhPDGF-BB versus Autologous Bone Graft in a Foot and Ankle Fusion Model

Abstract

The increased morbidity and surgical time associated with harvesting autologous bone graft (ABG) have encouraged surgeons to develop synthetic orthobiologic alternatives. The recombinant form of platelet-derived growth factor (rhPDGF-BB), an angiogenic, mitogenic, and chemotactic cytokine, has been shown to significantly enhance bone formation in human periodontal osseous defects when combined with a tricalcium phosphate carrier (β-TCP). The purpose of this prospective, controlled, randomized, multi-center feasibility clinical trial was to compare the safety and efficacy of this biosynthetic bone graft substitute (Augment™ Bone Graft) to ABG during ankle and hindfoot fusion. Twenty adult subjects requiring ankle or hindfoot fusion from three U.S. centers were enrolled and randomized in a 2:1 ratio to receive Augment™ or ABG, respectively. Surgical approach and fixation techniques were standardized, and minimum followup was 9 months. The primary endpoint was radiographic osseous union, evaluated by a blinded independent radiologist. Secondary endpoints included assessment of clinical success, union rate by serial computed tomography (CT) examination, time to full weightbearing, AOFAS Ankle-Hindfoot Score (AOFAS), Foot Function Index (FFI), Short Form-12 (SF-12), and Visual Analog pain assessment Scale (Pain VAS). At 36 weeks, 77% (10/13) of the Augment™ and 50% (3/6) of the ABG patients were fused based on radiographic criteria. There were two nonunions in the Augment™ group (9%, 2/14). Healing rates based on 12 week CT scanning (50% osseous bridging) were 69% (9/13) in the Augment™ and 60% (3/5) in the ABG groups, respectively. All functional outcome measures (FFI, AOFAS, SF-12), as well as the VAS pain scores, improved in both groups over time. Surgical procedure times lasted an average 26 minutes longer for the ABG as compared to the Augment™ populations. There were no device related serious adverse events in this study. Based on the available data, the rate of radiographic union, time to full weightbearing, and outcomes scores between the Augment™ and ABG subjects appear comparable. Augment™ may represent a safe and efficacious treatment alternative to ABG during foot and ankle arthrodesis.