Evaluation of Femoral Bone Fracture Healing in Rats by the Modal Damping Factor and Its Correlation With Peripheral Quantitative Computed Tomography

Abstract

Introduction Monitoring the progress of fracture healing is essential in order to establish the appropriate timing that ensures adequate bone strength for weight-bearing. In the present experimental study on a rat model of femoral fracture healing, the measurement of bone density and strength by peripheral quantitative computerized tomography (pQCT) was correlated with the modal damping factor (MDF) method. Methods Four groups of 12 male six-month-old Wistar rats each were anesthetized and submitted to baseline femoral pQCT and MDF scanning, followed by aseptic midshaft osteotomy of the right femur which was fixed by a locking intramedullary nail technique. The animals were left to recover and re-scanned following euthanasia of each group after six, eight, 10, and 12 weeks, respectively. The parameters measured by the pQCT method were total bone mineral density (BMD) and polar strength strain index (SSIp). Results Fracture healing progressed over time and at 12 weeks post-osteotomy there was no statistically significant difference between the osteotomized right and the control left femurs regarding MDF, BMD, and SSIp measurements. The highest correlations for the osteotomized femurs were observed between MDF and BMD (r =-0.647, P = 0.043), and between MDF and SSIp (r =-0.350, P = 0.321), at 10 weeks postoperatively. The high to moderate correlations between MDF and BMD, and between MDF and SSIp respectively, support the validity of MDF in assessing fracture healing. Conclusions Based on our findings in this fracture healing animal model, the results from the MDF method are reliable and correlate highly with the total BMD and moderately with the SSI polar values obtained by the pQCT method of bone quality measurement. Further studies are needed which may additionally support that the MDF method can be an attractive portable alternative to monitor fracture healing in the community.

Degradation and Bone-Contact Biocompatibility of Two Drillable Magnesium Phosphate Bone Cements in an In Vivo Rabbit Bone Defect Model

“…The bone mineral density in four different regions of the distal femoral bone was measured using a pQCT (Stratec XCT 2000, Stratec Medizintechnik GmbH, Pforzheim, Germany) in cooperation with the department of nuclear medicine. The measurements were performed directly after euthanization with the complete soft tissue around the femoral bone [ 23 ]. In a scout view of every bone, the four regions of interest (1: bone substitute, 2: spongiosa, 3: transition area between bone substitute and spongiosa, 4: corticalis of the diaphysis) were determined ( Figure 1 ).…”

Assessment of Bone Healing

“…A few clinical cases were reported by Mattei et al, who used vibration analysis to assess fracture healing in patients with external fixators and showed promising results [13][14][15] . However, it is important to note that both the presence of soft tissue and osteosynthesis implants alter the frequency, thereby limiting vibration analysis for assessing bone healing 12,16 .…”

“…The stiffness of an object directly correlates with its natural frequency 11 . Based on this concept, resonant frequency analysis and the modal damping factor have been used in vibration analysis to evaluate bone healing 11,12 . A few clinical cases were reported by Mattei et al, who used vibration analysis to assess fracture healing in patients with external fixators and showed promising results [13][14][15] .…”