Repair of a rat calvaria defect with injectable strontium (Sr)-doped polyphosphate dicalcium phosphate dehydrate (P-DCPD) ceramic bone grafts.

The trace element strontium (Sr) enhances new bone formation. However, delivering Sr, like other materials, in a sustained manner from a ceramic bone graft substitute (BGS) is difficult. We developed a novel ceramic BGS, polyphosphate dicalcium phosphate dehydrate (P-DCPD), which delivers embedded drugs in a sustained pattern. This study assessed the in vitro and in vivo performance of Sr-doped P-DCPD. In vitro P-DCPD and 10%Sr-P-DCPD were nontoxic and eluents from 10%Sr-P-DCPD significantly enhanced osteoblastic MC3T3 cell differentiation. A sustained, zero-order Sr release was observed from 10%Sr-P-DCPD for up to 70 days. When using this BGS in a rat calvaria defect model, both P-DCPD and 10% Sr-P-DCPD were found to be biocompatible and biodegradable. Histologic data from decalcified and undecalcified tissue showed that 10%Sr-P-DCPD had more extensive new bone formation compared with P-DCPD 12-weeks after surgery and the 10%Sr-P-DCPD had more organized new bone and much less fibrous tissue at the defect margins. The new bone was formed on the surface of the degraded ceramic debris within the bone defect area. P-DCPD represented a promising drug-eluting BGS for repair of critical bone defects.

Mark Coventry Award: Efficacy of Saline Wash Plus Antibiotics Doped Polyvinyl Alcohol (PVA) Composite (PVA-VAN/TOB-P) in a Mouse Pouch Infection Model.

BACKGROUND: The efficacy of saline irrigation for treatment of periprosthetic infection (PJI) is limited by the presence of contaminated medical devices. This study evaluated treatment efficacy of locally placed polyvinyl alcohol (PVA)/bioceramic composite doped with vancomycin (PVA-VAN-P) or vancomycin and tobramycin (PVA-VAN/TOB-P) after saline irrigation in a mouse pouch infection model. METHODS: Sutures were implanted into air pouches of BALB/cJ mice, then inoculated with Staphylococcus aureus. Mice were randomized into 6 groups (n = 6 each): (1) no bacteria; (2) bacteria without saline wash; (3) saline wash only; (4) saline wash + PVA-P; (5) saline wash + PVA-VAN-P, and (6) saline wash + PVA-VAN/TOB-P. After 7 days, pouches were washed with saline alone or with additional injection of 0.2 mL of the composites. Sacrifice occurred 14 days after the washout. Histology was performed on the pouch tissues and bacteria cultures on the washout fluid. RESULTS: Bacterial culture (optical density) showed that infection persisted after saline irrigation (0.10 ± 0.14) but was effectively eradicated by the addition of PVA-VAN-P (0.05 ± 0.09) and PVA-VAN/TOB-P (0.002 ± 0.003, P < .05). These effects were confirmed by histology. Importantly, no residues of the PVA-P were detected in either the pouch washouts or pouch tissues. CONCLUSION: PJI is common and problematic, and few innovations have changed clinical practice and/or outcome. Our data confirmed that the effect of saline irrigation was very limited in the presence of contaminated sutures. PVA-VAN/TOB-P was biodegradable, biocompatible, and effective in eradicating bacterial retention after saline irrigation. Application of PVA-VAN/TOB-P after saline irrigation could be an option for treatment of PJI and should be evaluated in future PJI animal models.