Biomechanical comparison of menisci from different species and artificial constructs

Background: Loss of meniscal tissue is correlated with early osteoarthritis but few data exist regarding detailed biomechanical properties (e. g. viscoelastic behavior) of menisci in different species commonly used as animal models. The purpose of the current study was to biomechanically characterize bovine, ovine, and porcine menisci (each n = 6, midpart of the medial meniscus) and compare their properties to that of normal and degenerated human menisci (n = 6) and two commercially available artificial scaffolds (each n = 3). Methods: Samples were tested in a cyclic, minimally constraint compression-relaxation test with a universal testing machine allowing the characterization of the viscoelastic properties including stiffness, residual force and relative sample compression. T-tests were used to compare the biomechanical parameters of all samples. Significance level was set at p < 0.05. Results: Throughout cyclic testing stiffness, residual force and relative sample compression increased significantly (p < 0.05) in all tested meniscus samples. From the tested animal meniscus samples the ovine menisci showed the highest biomechanical similarity to human menisci in terms of stiffness (human: 8.54 N/mm +/- 1.87, cycle 1; ovine: 11.24 N/mm +/- 2.36, cycle 1, p = 0.0528), residual force (human: 2.99 N +/- 0.63, cycle 1 vs. ovine 3.24 N +/- 0.13, cycle 1, p = 0.364) and relative sample compression (human 19.92\% +/- 0.63, cycle 1 vs. 18.72\% +/- 1.84 in ovine samples at cycle 1, p = 0.162). The artificial constructs - as hypothesized- revealed statistically significant inferior biomechanical properties. Conclusions: For future research the use of ovine meniscus would be desirable showing the highest biomechanical similarities to human meniscus tissue. The significantly different biomechanical properties of the artificial scaffolds highlight the necessity of cellular ingrowth and formation of extracellular matrix to gain viscoelastic properties. As a consequence, a period of unloading (at least partial weight bearing) is necessary, until the remodeling process in the scaffold is sufficient to withstand forces during weight bearing

New method for detection of complex 3D fracture motion - Verification of an optical motion analysis system for biomechanical studies

<p>Abstract</p> <p>Background</p> <p>Fracture-healing depends on interfragmentary motion. For improved osteosynthesis and fracture-healing, the micromotion between fracture fragments is undergoing intensive research. The detection of 3D micromotions at the fracture gap still presents a challenge for conventional tactile measurement systems. Optical measurement systems may be easier to use than conventional systems, but, as yet, cannot guarantee accuracy. The purpose of this study was to validate the optical measurement system PONTOS 5M for use in biomechanical research, including measurement of micromotion.</p> <p>Methods</p> <p>A standardized transverse fracture model was created to detect interfragmentary motions under axial loadings of up to 200 N. Measurements were performed using the optical measurement system and compared with a conventional high-accuracy tactile system consisting of 3 standard digital dial indicators (1 μm resolution; 5 μm error limit).</p> <p>Results</p> <p>We found that the deviation in the mean average motion detection between the systems was at most 5.3 μm, indicating that detection of micromotion was possible with the optical measurement system. Furthermore, we could show two considerable advantages while using the optical measurement system. Only with the optical system interfragmentary motion could be analyzed directly at the fracture gap. Furthermore, the calibration of the optical system could be performed faster, safer and easier than that of the tactile system.</p> <p>Conclusion</p> <p>The PONTOS 5 M optical measurement system appears to be a favorable alternative to previously used tactile measurement systems for biomechanical applications. Easy handling, combined with a high accuracy for 3D detection of micromotions (≤ 5 μm), suggests the likelihood of high user acceptance. This study was performed in the context of the deployment of a new implant (dynamic locking screw; Synthes, Oberdorf, Switzerland).</p

Symphyseal fixation in open book injuries cannot fully compensate anterior SI joint injury—A biomechanical study in a two-leg alternating load model - Table 1

<p>Symphyseal fixation in open book injuries cannot fully compensate anterior SI joint injury—A biomechanical study in a two-leg alternating load model</p> - Table

Axial view of a pelvic specimen with five marker sets attached on its sacrum, iliac and pubic bones for motion tracking.

<p>The specimen is mounted on the testing frame with a jig holding the sacrum. The pubic symphysis is fixed with a modular implant device.</p

Test setup with a pelvic specimen mounted horizontally in the machine frame for biomechanical testing (posterolateral view).

<p>Both distal femoral ends are attached to sliding posts and alternately loaded in the direction of their mechanical axes (as indicated with the two straight double arrows) via converted torsional movement of the machine actuator with the load cell (as indicated with a curved double arrow). The sacrum is attached to the testing frame via a jig allowing free movement in the sagittal plane.</p