Micro-CT observation of angiogenesis in bone regeneration.

OBJECTIVES: Restoration of an adequate blood supply is essential for the bone healing process and is key to the success of bone augmentation procedures. In this study, we evaluated angiogenesis in rat calvarial flat bone defects using in vivo microfocus computed tomography (micro-CT). MATERIALS AND METHODS: Twenty rats were used. The calvarium was exposed and calvarial bone defects of critical (5-mm diameter) and non-critical (2.7-mm diameter) sizes were prepared. Bone regeneration and angiogenesis were evaluated by image analysis using micro-CT and histological examination. RESULTS: Critical- and non-critical-sized calvarial bone defects showed bone regeneration and angiogenesis around the midsagittal suture. Critical-sized calvarial bone defects showed approximately 1.2% reossification of the original surgical defect, whereas the non-critical-sized defects showed approximately 43.3% reossification at day 28. Furthermore, angiogenesis was observed later in the critical-sized calvarial bone defects (about 38.2%), whereas angiogenesis was observed early in the non-critical-sized calvarial bone defects (about 75.5%) at day 28. New blood vessel networks were observed around defects of both sizes. CONCLUSIONS: Angiogenesis preceded bone regeneration around critical- and non-critical-sized calvarial bone defects. Angiogenesis led to full bone formation in non-critical-sized defects.

Autogenous bone with or without hydroxyapatite bone substitute augmentation in rat calvarium within a plastic cap.

OBJECTIVES: We evaluated the effect of autogenous bone (AB) and hydroxyapatite bone (HA) for the assessment of bone augmentation beyond the skeletal envelope in the rat calvarium. STUDY DESIGN: The calvaria of 12 rats were exposed and 2 plastic caps were placed with AB and HA or AB alone in the calvarium. Images of bone augmentation within the plastic caps were taken using micro-CT (R_mCT). Histologic sections were cut along the same plane as those used for the R_mCT images at 12 weeks. Bone volume (BV) was calculated using BV-measuring software. RESULTS: BV increased at both the experimental and control sites. The newly generated tissue did not significantly differ between the experimental and control sites; however, the mineralized tissue was significantly higher at control sites compared with experimental sites. CONCLUSIONS: The results indicate that the combination of HA and AB was biocompatible and allowed osteoconduction.

In vivo bone regenerative effect of low-intensity pulsed ultrasound in rat calvarial defects.

OBJECTIVES: Low-intensity pulsed ultrasound (LIPUS) is a biophysical intervention in a bone repair process. However, neither the healing events of the flat bones of the skull using LIPUS nor the optimal stimulation settings are fully understood. The aim of this study was to evaluate the bone regenerative effect of LIPUS in rat calvarial flat bone defects by using in vivo microfocus computerized tomography (micro-CT). STUDY DESIGN: The calvarium was exposed, and noncritical-sized 2.7-mm defects were prepared. LIPUS (1.6 MHz, repeating 1.0-kHz pulsation, and 30-mW/cm(2) intensity) was applied for 20 minutes daily. Bone regeneration was evaluated by image analysis using micro-CT and histologic examination. RESULTS: Within 2 weeks, LIPUS-treated rats demonstrated 7.0% reossification of the original surgical defect, whereas control rats demonstrated 3.6%. At 3 and 4 weeks, a significant difference in the reossification ratio was observed (12.0% vs. 5.8% and 18.1% vs. 9.8%, respectively; P < .05). CONCLUSIONS: LIPUS accelerated bone regeneration of noncritical rat calvarial defects as confirmed by micro-CT.