Physical Properties and Antimicrobial Release Ability of Gentamicin-Loaded Apatite Cement/α-TCP Composites: An In Vitro Study

Apatite cement (AC), which has excellent osteoconductive ability, and alpha-tricalcium phosphate (α-TCP), which can be used for bone replacement, are useful bone substitute materials. The objective of this study was to clarify the physical properties and antimicrobial release ability of antibiotic-loaded AC/α-TCP composites in vitro. Gentamicin-loaded, rapid setting AC/α-TCP composites were prepared in 2 mixing ratios (10:3 and 10:6). The cement paste of AC/α-TCP composites was prepared in a plastic mold and dried in a thermostatic chamber at 37 °C and 100% relative humidity for 24 h. A diametral tensile strength test, powder X-ray diffraction analysis, and gentamicin release test were performed. The diametral tensile strengths of the AC/α-TCP composites were significantly less than that of AC alone. Powder X-ray diffraction patterns exhibited the characteristic peaks of hydroxyapatite in the AC/α-TCP composites and gentamicin-loaded AC/α-TCP composites. The concentration of the released gentamicin was maintained above the minimum inhibitory concentration of Staphylococcus aureus until Day 30 in both the gentamicin-loaded AC/α-TCP composites (10:3 and 10:6). Our results suggest that a gentamicin-loaded AC/α-TCP composite has potential as a drug delivery system. Further study is essential to investigate the antimicrobial activity and safety of the gentamicin-loaded AC/α-TCP composites in animal models.

Packing with alpha-tricalcium phosphate followed by curettage and phenol-ethanol ablation for appendicular giant cell tumor of bone

Giant cell tumor of bone (GCTB) is an intermediate and locally aggressive bone tumor. Alpha-tricalcium phosphate (alpha-TCP) is an adjustable bone substitute used to fill various sizes of bone cavities after curettage for GCTB. This study aimed to evaluate the surgical outcome of packing with alpha-TCP followed by curettage and phenol-ethanol ablation. We retrospectively reviewed data of 16 patients with GCTB who underwent primary surgery in our institute between January 2009 and April 2021. Data of Campanacci grading system; number of local recurrences and distant metastases; local recurrence-free survival rate using the Kaplan-Meier method; oncological outcomes; and complications after surgery (secondary osteoarthritis and postoperative fracture) were evaluated in this study. Regarding the Campanacci grading system, 2 patients were classified as grade I, 14 as grade II, and none as grade III. The 5-year local recurrence-free survival rate was 77.8% in all cases. Lung metastasis was not detected in this study. Oncological outcomes were: continuous disease free, 13 patients; alive with disease, 3 patients; and no evidence of disease or death of disease, none of the patients. Secondary osteoarthritis after surgery was not detected in the present study. Packing with alpha-TCP followed by curettage and phenol-ethanol ablation for appendicular GCTB may be safe and effective in suppressing the risk of secondary osteoarthritis.

Porous Alpha-Tricalcium Phosphate with Immobilized Basic Fibroblast Growth Factor Enhances Bone Regeneration in a Canine Mandibular Bone Defect Model

The effect of porous alpha-tricalcium phosphate (α-TCP) with immobilized basic fibroblast growth factor (bFGF) on bone regeneration was evaluated in a canine mandibular bone defect model. Identical bone defects were made in the canine mandible; six defects in each animal were filled with porous α-TCP with bFGF bound via heparin (bFGF group), whereas the other was filled with unmodified porous α-TCP (control group). Micro-computed tomography and histological evaluation were performed two, four and eight weeks after implantation. The bone mineral density of the bFGF group was higher than that of the control group at each time point (p < 0.05), and the bone mineral content of the bFGF group was higher than that of the control group at four and eight weeks (p < 0.05). Histological evaluation two weeks after implantation revealed that the porous α-TCP had degraded and bone had formed on the surface of α-TCP particles in the bFGF group. At eight weeks, continuous cortical bone with a Haversian structure covered the top of bone defects in the bFGF group. These findings demonstrate that porous α-TCP with immobilized bFGF can promote bone regeneration.