Regional and temporal changes in the acoustic properties of fracture callus in secondary bone healing

Abstract

Controlled fractures were created in the right femora of 17 male Sprague-Dawley rats. The fractured limbs were harvested at 2, 4, 6, and 8 weeks after fracture, fixed, and embedded in polymethylmethacrylate. Midsagittal sections from each animal were evaluated with a scanning acoustic microscope, a device that generates an acoustic impedance map of the scanned material. The impedance of the fracture callus was measured in six regions on each specimen. These regions were chosen in an effort to distinguish between the impedance of the callus formed through intramembranous or endochondral ossification, and we found that the time course of increasing impedance differed for the fracture callus formed through the two pathways. Additionally, we found a significant difference in the mean impedance of the callus at each time period (p < or = 0.0013 for all comparisons), which resulted in an extremely linear relationship (r2 = 0.999) between mean callus impedance and healing time. This experimental model has become a popular choice for the investigation of fracture healing. As such, an accurate determination of the mechanical properties of the fracture callus is often sought. We propose that the implementation of scanning acoustic microscopy in the study of fracture healing may determine the changes in the material properties more accurately than conventional testing methods.

Role of local insulin augmentation upon allograft incorporation in a rat femoral defect model

“…After sacrifice, the right femur was extracted from each animal at 6 weeks ( n = 15) and at 4 weeks ( n = 14). The extracted femurs were then processed for histology using standard calcified histological techniques, and stained with Stevenel blue and Van Gieson picrofuschin as previously described 19, 21, 22…”

“…Additionally, quantitative histomorphometry was performed on the aforementioned samples, taking seven distinct measurements as previously described in the literature 19, 21, 22. By measuring these seven different areas, total periosteal bone (1), total endosteal bone (2), and total gap defect (3) was calculated (Fig.…”

Validation of speed of sound for the assessment of cortical bone maturity

“…SOS measurements at the calcaneus in children show age dependency and a correlation with increasing bone density (Jaworski et al, 1995). However, SOS measurements at locations of mainly cortical bone produce more consistent results, even detecting sex differences (Harten et al, 1997). Changes in SOS in the thumb and patella increase with age after puberty and peak at 20-25 years of age (Schönau et al, 1994).…”

Callus mineralization following distraction osteogenesis of the mandible monitored by scanning acoustic microscopy (SAM)

“…Harten et al (1997) published their results of using SAM measurements of acoustic impedance (Z) to monitor fracture healing in embedded (PMMA) specimens of rats. Z of femoral fracture sites was investigated after different consolidation periods using a SAM working at 50 MHz with a resolution of 80 mm.…”