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Biomechanical properties of a novel morselized bone graft cage
Background: Posterior lumbar interbody fusion (PLIF) is performed using various interbody spacers. Wang and colleagues (2014) created an interbody cage by compressing morselized corticocancellous bone chips. They concluded that the newly morselized bone interbody fusion (MBIF) cage can provide appropriate stiffness at the physiologic loads. The purposes of this study were to replicate Wang and colleagues study by creating the MBIF cage and in case of failure, to redesign the MBIF cage and assess its biomechanical properties in comparison with the PEEK cage. Methods: Lamina and spinous processes of fresh frozen spine segments were morselized and placed in a bullet-shaped mold and compressed with 8 kN force. When we redesigned the MBIF cage, the mold was lined with a thin layer of stainless-steel mesh acting as a scaffold. The redesigned MBIF (n = 6) and PEEK (n = 6) cages were place between 2 blocks of solid polyurethane foam, simulating healthy bone, and underwent axial compression while we recorded compressive force and displacement curve. The experiment was repeated with polyurethane foam simulating osteoporotic bone. Results: The MBIF cage collapsed under axial compression. In the healthy bone group, peak force at 3-mm displacement was significantly lower in the redesigned MBIF cage compared with the PEEK cage. At 5-mm displacement, peak force did not differ significantly between the 2 cages. At lower levels of displacement, the redesigned MBIF construct failed by loss of height of the cage, while the PEEK cage construct failed by destruction of polyurethane foam contact surface. In osteoporotic bone, peak forces at 3 and 5 mm were significantly higher in the redesigned MBIF cage than in the PEEK cage constructs. Conclusion: The results of Wang and colleagues (2014) were not reproducible in our study. The redesigned MBIF cage showed comparable biomechanical properties to those of the PEEK cage in healthy bone construct and outperformed the PEEK cage in osteoporotic bone construct. The redesigned MBIF can be a viable option instead of a synthetic cage in patients with poor bone quality.
Journal Article
Age-related variations in corneal stress-strain index in the Indian population
To report age-related variations in corneal stress-strain index (SSI) in healthy Indians. It was a retrospective study where healthy Indian individuals aged between 11 and 70 years who had undergone corneal biomechanics assessment using Corvis ST between January 2017 and December 2021 were enrolled. Composite corneal biomechanical parameters and corneal SSI were abstracted from Corvis ST and compared across different age groups using one-way analysis of variance (ANOVA). Also, Pearson's correlation was used to evaluate the association between age and SSI. Nine hundred and thirty-six eyes of 936 patients with ages between 11 and 77 years with mean ± SD intraocular pressure (IOP) and pachymetry of 16.52 ± 2.10 mmHg and 541.13 ± 26.39 μs, respectively. Composite corneal biomechanical parameters such as deformation amplitude ratio max at 1 mm (P < 0.001) and 2 mm (P < 0.001), biomechanically corrected IOP (P = 0.004), stiffness parameter at A1 (P < 0.001, Corvis biomechanical index (P < 0.018), and SSI (P < 0.001) were found to be significantly different as a function of age group. We noted a statistically significant positive association of SSI with age (P < 0.001), spherical equivalent refractive error (P < 0.001), and IOP (P < 0.001) and a significant negative association with anterior corneal astigmatism (P < 0.001) and Anterior chamber depth (ACD) (P < 0.001). Also, SSI was positively associated with SPA1 and bIOP, whereas negatively associated with integrated radius, max inverse radius, and Max Deformation amplitude (DA) ratio at 1 mm and 2 mm. We noted a positive association of corneal SSI with age in normal healthy Indian eyes. This information could be helpful for future corneal biomechanical research.
Journal Article
Continuous Vertical Inside-Out Versus Traditional Vertical Inside-Out Meniscal Repair: A Biomechanical Comparison
Objectives:
To evaluate the displacement, stiffness after cyclical loading, and load to failure for a continuous vertical inside-out meniscal suture compared to a traditional vertical inside-out meniscal suture in a porcine medial meniscus.
Methods:
Twenty-eight porcine knees were divided into 2 groups of 14 medial menisci each. A 2.0-cm longitudinal cut was made in the red-white zone of the medial meniscus in each knee. The continuous suture (CS) group received 4 vertical stitches using a continuous vertical suture technique, while the inside-out suture (IO) group received a traditional vertical suture with 4 stitches. The specimens underwent load-to-failure testing at 5 mm/s, and displacement, system stiffness, and maximum load to failure were compared between the groups.
Results:
Displacement after the cyclic test was 0.53 ± 0.12 mm for the CS group and 0.48 ± 0.07 mm for the IO group, with no significant difference (P = .2792). Stiffness at ultimate load testing was 36.3 ± 1.9 N/mm for the CS group and 35.3 ± 2.4 N/mm for the IO group (P = .2557). In the load-to-failure test, the ultimate load was 218.2 ± 63.9 N for the CS group and 238.3 ± 71.3 N for the IO group (P = .3062), showing no significant differences between the groups.
Conclusion:
The continuous vertical meniscal suture provided biomechanical results similar to the traditional vertical suture technique for the treatment of longitudinal meniscal lesions, offering a viable alternative for meniscal repair.
Journal Article