Effects of calcitonin on the osseointegration of porous hydroxyapatite implant in osteoporosis model

Abstract

BACKGROUND: Calcitonin can increase bone quantity and quality and reduce bone fracture occurrence. OBJECTIVE: To evaluate effects of calcitonin on the osseointegration of the porous hydroxyapatite implants and further on promoting the biological fixation of the implants in osteoporosis model. DESIGN, TIME AND SETTING: A randomized controlled experiment was performed at the Animal Experimental Center of Sun Yat-sun University and Histomorphometry Laboratory of Hong Kong University from September to December 2007 and from March to May 2008, respectively. MATERIALS: A total of 30 female SD rats of SPF grade and aging 5 months were randomly divided into three groups: sham operation + hydroxyapatite, ovariectomy (OVX) + hydroxyapatite, and OVX + calcitonin + hydroxyapatite groups, with 10 rats per group. METHODS: Postmenopausal osteoporosis models were established in the OVX + hydroxyapatite and OVX + calcitonin + hydroxyapatite groups using OVX method. While, rats in the sham operation + hydroxyapatite group were considered as the controls. The porous hydroxyapatite prostheses were inserted into the tibial plateum of the left tibia in each group, followed by a subcutaneous injection of calcitonin [5 U/(kg·d)] for twelve weeks in the OVX + calcitonin + hydroxyapatite group. MAIN OUTCOME MEASURES: Tibia carrying with implant was sectioned into sections. Skeletal density changes of lumbar vertebra were detected using bone histomorphometry and double energy ray bone density apparatus, bone quantity surrounding prosthesis was observed, and osseointegration rate of prosthesis was measured. RESULTS: Bone density of lumbar vertebra was gradually improved in the OVX + calcitonin + hydroxyapatite group. After calcitonin injection, osseointegration area rate increased 22.0%, which was nearly twice compared with the OVX + hydroxyapatite group (t=9.665, P < 0.05). CONCLUSION: In osteoporosis conditions, calcitonin can increase bone mass surrounding the implants and promote osseointegration by subcutaneous injection.