Preparation of a Hydroxyapatite Ceramic with Comblike Tubules Structure and its Permeablity

The objectives of this study are to prepare a porous hydroxyapatite ceramic which has dentin tubule-like structure and determine its permeability. Slurry of hydroxyapatite powder, deionized water and a binder was poured into a ring which was placed on a freezing plate.The hydroxyapatite slurry was freezed in a certain rate (by controlling the temperature of the freeze plate at −15°C, −30°C and −45°C) for a certain period of time, then the freezed sample was freezing dried to remove the frozen vehicle, followed by being sintered at 1250 °C for 2 h. After that，the morphology of the cross section and longitudinal section of the sintered porous hydroxyapatite ceramic was observed by SEM and the hydraulic conductance of cross section discs of the sintered porous hydroxyapatite were determined using a self-made micro-flowing permeability tester. Results showed that the prepared hydroxyapatite ceramics having bottom-up unidirectional comblike tubule structure and the tubule diameters associated with the temperature of freezing plate.The ceramic discs prepared on the freezing plate of −45°C exhibited similarity to nature dentin tubule, with a diameter of 9.72±3.41mm and a hydraulic conductance of 0.16±0.09 ml×min-1×cm-2×cm×H2O-1.

Use of autologous bone grafting from the calcaneus and interconnected porous hydroxyapatite ceramic for bone transplantation in rheumatoid foot surgery

Cancellous bone grafts from the calcaneus have been used for the foot and ankle as well as iliac bone graft; however, there is a sparse report for calcaneal bone transplantation in the field of rheumatoid foot surgery. In this study, safety and usefulness of calcaneal bone grafts, and combination with interconnected porous hydroxyapatite ceramic, was evaluated in rheumatoid arthritis foot surgeries. Of six rheumatoid arthritis cases, three (talo-navicular joint fusion) used a calcaneal bone graft alone, and the remaining three cases (subtalar joint and talo-navicular joint fusion) used a combination of calcaneal bone graft and interconnected porous hydroxyapatite ceramic augmented with dense calcium hydroxyapatite for subtalar bony defect (1.5–2.0 cm) after the correction. Pre- and postoperative Japanese Society for Surgery of the Foot rheumatoid arthritis foot ankle scale scores were obtained for the clinical assessment. As radiographic assessment, tibio-calcaneal angle, calcaneal pitch, talo-1st metatarsal angle, and pronated foot index were also evaluated. After starting weight-bearing or walking, there was no pain and skin trouble at the fusion and harvesting sites. All cases achieved bony fusion within 6–10 weeks. Japanese Society for Surgery of the Foot rheumatoid arthritis foot ankle score was improved in all six cases. Furthermore, tibio-calcaneal angle, talo-1st metatarsal angle, and pronated foot index were also improved at latest follow-up in all cases. In conclusion, autologous bone grafting from the calcaneus was safe and convenient even in rheumatoid foot surgeries. For larger bony defects (1.5–2.0 cm), combination use with interconnected porous hydroxyapatite ceramic augmented with dense calcium hydroxyapatite was also useful.