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A rhPDGF-BB/bovine type I collagen/?-TCP mixture for the treatment of critically sized non-union tibial defects: An in vivo study in rabbits
Vasudev Vivekanand Nayak, MSci, PhD
1; Joseph P. Costello II, BS
1; Quinn T. Ehlen, BS
1; Blaire V. Slavin, BS
1; Nicholas Mirsky, BS
1; Sophie Kelly, BS
2; Camila Suarez, BS(c)
3; Sylvia Daunert, PharmD, MS, PhD
1; Lukasz Witek, MSci, PhD
4; Paulo G. Coelho, MD, DDS, PhD, MBA
11University of Miami, Miami, FL; 2Florida Atlantic University, Boca Raton, FL; 3Duke University, Durham, NC; 4New York University, New York, NY
Non-union during healing of bone fractures affects up to ~5% of patients worldwide. Given the success of recombinant human Platelet Derived Growth Factor-B chain homodimer (rhPDGF-BB) in promoting angiogenesis and bone fusion in the hindfoot and ankle, rhPDGF-BB combined with bovine type I collagen/?-TCP matrix (AIBG) could serve as a viable alternative to autografts in the treatment of non-unions. Defects (~2 mm gaps) were surgically induced in tibiae of skeletally mature New Zealand white rabbits. Animals were allocated to one of 4 groups – negative control (empty defect, healing for 8 weeks - Neg CTRL), acute treatment with AIBG (healing for 4- or 8- weeks - AcuSho and AcuLng, respectively), and chronic treatment with AIBG (injection 4 weeks post defect creation and then healing for 8 weeks - ChrLng). Bone formation was analyzed qualitatively and semi-quantitatively through histology. Samples were imaged using dual-energy x-ray absorptiometry and computed tomography for defect visualization and volumetric reconstruction, respectively. Delayed healing or non-healing was observed in the Neg CTRL group, whereas defects treated with AIBG in an acute setting yielded bone formation as early as 4 weeks (AcuSho) with bone growth appearing discontinuous. At 8 weeks (acute setting - AcuLng), substantial remodeling was observed with higher degrees of bone organization characterized by appositional bone growth. The chronic healing experimental group (ChrLng) evidenced bone formation and remodeling, with no indication of non-union after treatment with AIBG. Furthermore, bone growth in the ChrLng group was accompanied by an increased presence of osteons, osteonal canals and interstitial lamellae. Qualitatively and semi-quantitatively, chronic application of AI facilitated complete bridging of the induced non-union defects, while untreated defects (Neg CTRL), or defects treated acutely with AIBG (AcuSho and AcuLng) demonstrated a lack of complete bridging.
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