Injectable, brushite-forming calcium phosphate cements (CPC) show potential for bone replacement, but they exhibit low mechanical strength and fracture toughness. One approach to overcome these limitations is the modification of the CPC with reinforcing fibers. The aim of this study was to test the in vivo biocompatibility of PLGA fiber-reinforced, brushite-forming CPC in a sheep large animal model for lumbar ventrolateral vertebroplasty.
Bone defects (diameter 5 mm) were placed in aged, osteopenic female sheep and left empty (L2) or injected with pure CPC (L3) or PLGA-fiber-reinforced CPC (L4; fiber diameter 25 µm; length 1 mm; 10% (w/w)). Three and 9 months post-operation (n = 20 each), structural and functional CPC effects on bone regeneration were documented ex vivo by osteodensitometry, histomorphometry, micro-CT, and biomechanical testing.
Addition of PLGA fibers enhanced CPC osteoconductivity and augmented bone formation. This was demonstrated by: i) significantly enhanced structural (bone volume/total volume; shown by micro-CT and histomorphometry; 3 and/or 9 months) and bone formation parameters (osteoid volume, osteoid surface; 9 months); ii) numerically enhanced bone mineral density (3 and 9 months) and biomechanical compression strength (9 months); and iii) numerically decreased bone erosion (eroded surface; 3 and 9 months).
PLGA-fiber-reinforced brushite-forming CPC is highly biocompatible and its PLGA-fiber component enhanced bone formation. Also, PLGA fibers improve the mechanical properties of brittle CPC, with potential applicability in load-bearing areas.