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

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.

A new, low cost, locking plate for the long-term fixation of a critical size bone defect in the ratfemur: in vivo performance, biomechanical and finite element analysis.

BACKGROUND: The optimum fixation device for the critical size bone defect is not established yet. OBJECTIVE: A reliable, feasible and low-cost fixation device for the long-term maintenance of a critical bone defect. METHODS: A custom-made plate made of poly-methyl-methacrylate was used for the fixation of a critical defect of rats' femurs. The screws were securely fixing both on the plate and the bone. A three point bending test, aimed to resemble the in vivo loading pattern, a Finite Element Analysis and a 24-week in vivo monitoring of the integrity of the plate fixation were utilized. RESULTS: The plate has linear and reproducible behavior. It presents no discontinuities in the stress field of the fixation. Its properties are attributed to the material and the locking principle. It fails beyond the level of magnitude of the normal ambulatory loads. In vivo, 100% of the plates maintained the bone defect intact up to 12 weeks and 85% of them at 24 weeks. CONCLUSION: This novel locking plate shows optimal biomechanical performance and reliability with high long-term in vivo survival rate. It is fully implantable, inexpensive and easily manufactured. It can be qualified for long term critical defect fixation in bone regeneration studies.

Development of a new optical device and its feasibility in prostate cancer detection.

AIM: To develop a new optical device (prostate optical device, POD) for assessment of prostate tissue stiffness and evaluate its sensitivity and specificity in prostate cancer detection. PATIENTS AND METHODS: POD was tested in prostate phantoms and in patients with indications for prostate biopsy. Its sensitivity and specificity were compared to digital rectal examination (DRE) and transrectal ultrasonography (TRUS). RESULTS: POD was able to identify stiffness differences on each prostate phantom. 45 patients were included in the study. Sensitivity of TRUS (40%) was significantly lower to POD (85.7%) and DRE (74.3%) (p = 0.000 and p = 0.003, respectively). There was no statistical difference between POD and DRE (p = 0.221). The combination of POD and DRE showed the highest sensitivity (88.6%), positive predictive value (81.6%), and negative predictive value (42.9%) among all diagnostic tests. CONCLUSIONS: POD identified prostatic stiffness differences with the same sensitivity of DRE performed by an experienced urologist providing an objective indication for prostate biopsy and early prostate cancer detection.

Alteration in serum leptin correlates with alterations in serum N-telopeptide of collagen type I and serum osteocalcin during the progression of osteoporosis in ovariectomized rats.

The role of leptin during the progression of osteoporosis was investigated in ovariectomized rats by correlation of serum leptin levels with N-telopeptide of collagen type I (NTx) and osteocalcin levels before ovariectomy and 20, 40 and 60 days after the operation. Furthermore, peripheral quantitative computed tomography was used to confirm the development of severe osteoporosis in rats on day 60. The levels of NTx and osteocalcin were significantly increased on day 20 [61.9+/-5.4 nM BCE (bone collagen equivalents) and 215.6+/-53.3 ng/mL, respectively] in comparison to those before ovariectomy (41.3+/-1.7 nM BCE and 60.4+/-10.9 ng/mL). Accordingly, leptin was significantly elevated on day 20 (3033+/-661 vs. 606+/-346 pg/mL before ovariectomy). Bone markers and leptin levels remained constant up to day 40, while a slight, but not statistically significant, decrease was noted for osteocalcin and leptin on day 60. Although leptin and bone markers did not correlate before ovariectomy (r=0.09 for NTx and r=-0.05 for osteocalcin), strong correlation was observed at all time points after ovariectomy. The data obtained suggest that the alterations in serum leptin levels during the progression of osteoporosis in ovariectomized rats follow the alterations in bone markers.

Modal damping for monitoring bone integrity and osteoporosis.

We applied a noninvasive method to assess bone structural integrity. The method is based on the measurement of the dynamic characteristics of the bone (quality factor and modal damping factor) by applying vibration excitation in the range of acoustic frequencies, in the form of an acoustic sweep signal. Excised sheep femora were tested to detect changes in modal damping, density (kg/m3), bone mineral density (kg/m2) and bone mineral (hydroxyapatite) percentage. The changes were recorded after each time of chemical treatment of the bones performed to gradually cause mineral removal, thus simulating osteoporosis. It was shown that the change in quality factor and damping was in all cases on average equal or greater to the change in all other measured characteristics, thus strengthening the potential of the proposed method to become a valuable assessment tool for monitoring bone integrity and osteoporosis.