Behaviour of ChronOS™ Inject in metaphyseal bone defects of distal radius fractures: Tissue reaction after 6–15 months

Abstract

Biodegradable calcium phosphate cements are frequently used in human patients but data regarding resorption characteristic of ChronOS™ Inject in metaphyseal bone defects are lacking.Six patients (range 62–81 years) with a dorsally displaced distal radius fracture were treated with volar locking plate systems and ChronOS™ Inject application into the metaphyseal bone defect. During implant removal (time in situ 6–15 months, average 11 months) a 2mm diameter biopsy was obtained from the region of the previous cement injection. In all specimens’ area of bone, osteoid and remaining tissue were histomorphometrically determined and presence of cement particles, bone marrow fibrosis and signs of inflammation were recorded.Vital bone tissue, osteoid formation, mast cell occurrence and marrow fibrosis were detected in most specimens. Varying but small amounts of granular material identified as remainder of the cement were detected in all specimens. Agglomerations of granular material were often surrounded by bone tissue and islets of newly formed osteoid in direct contact with the remaining cement also occurred. Bone density (i.e. area per region of interest) ranged between 6.9% and 36.2% and osteoid density between 0.5% and 7.8%. Bone osteoid ratio was higher in patients who received no osteoporosis medication and lower in patients who received osteoporosis medication (range 6.0–32.1). The present study shows that small amounts of ChronOS™ Inject are still detectable in human patients 15 months after implantation into a distal radius bone defect. During tissue remodelling ChronOS™ Inject is integrated into the newly formed trabecular bone meshwork.