In Vivo Histological Changes Occurring in Hydroxyapatite Cranial Reconstruction. Case Report.

Abstract

Histological changes were observed in a hydroxyapatite plate and hydroxyapatite granules used to repair a craniotomy defect and removed after 2 years and 9 months of use. The hydroxyapatite plates and granules had completely fused to the cranium, with new bone formation on the dural side extending in a three-dimensional matrix along the pores with the Haversian system in the center. New bone formation was less extensive under the artificial dura than under the normal dura. This finding suggests that the dura has the ability to promote bone formation. A new vessel was found along the interconnecting pores. The interconnecting pores allow osteoconduction in the hydroxyapatite plate, so new bone formation can progress. Hydroxyapatite has osteoconduction properties and is biocompatible, so gains strength in vivo through new bone formation, and is the ideal material for artificial bones. Factors important to achieving good bone formation after cranial reconstruction surgery include presence of the dura, and pore size approximate to the Haversian system (100-500 mm) and interconnecting pores in the hydroxyapatite plate.

A 12 month in vivo study on the response of bone to a hydroxyapatite–polymethylmethacrylate cranioplasty composite

“…Okii et al [13] reported on histological changes observed in HA plates and HA granules, which were removed from a patient after nearly 3 years in vivo. The HA plate had fused tightly to the cranium and could be excised only by using a diamond drill.…”

Bioactive glass and hybrid scaffolds prepared by sol–gel method for bone tissue engineering

“…11 The minimum pore diameter required for bone ingrowth and angiogenesis into a scaffold is generally considered to be 100 mm. 6,12 Bioactive glasses are amorphous silica based materials that are biocompatible, bioactive, osteoconductive and even osteoproductive. 10 Their bone bonding ability has been attributed to the formation of a hydroxycarbonate apatite (HCA) layer in the surface of the glass on contact with body fluid.…”

Bioactive sol‐gel foams for tissue repair

“…It is important to note that in order to repair large defects, 3‐D scaffolds are required to provide a template and support tissue growth rather than the usual powder or granular form in which bioactive glasses currently are commercially produced. Ideally the template must consist of (1) an interconnected network with large pores (greater than 100 μm) to enable tissue ingrowth and nutrient delivery to the center of the regenerated tissue;11 and (2) pores in the microporous (<2 nm) or mesoporous (2 nm < pore size < 50 nm) range to promote cell adhesion, adsorption of biologic metabolites,12 and resorbability at controlled rates to match that of tissue repair.…”