The Effect of Axial Length Elongation on Corneal Biomechanical Property

Background: To investigate the correlation between the corneal biomechanical parameter stress-strain index (SSI) and axial length (AL) in moderately elongated eye (MEE) and severely elongated eye (SEE).Methods: This study included 117 eyes from 117 participants. Among them, 59 (50.4%) had MEE (AL<26 mm) and 58 (49.6%) had SEE (AL≥26 mm). AL was measured using Lenstar LS-900, and central corneal thickness (CCT) and anterior chamber volume (ACV) were measured using Pentacam. SSI was measured via corneal visualisation Scheimpflug technology (Corvis ST). Kolmogorov-Smirnov test, Student’s t-test, and Pearson and partial correlation analyses were used for statistical analyses.Results: The mean (±SD) SSI was 1.08 ± 0.15 in the MEE group and 0.92 ± 0.13 in the SEE group (p < 0.01). SSI was positively correlated with age (MEE: r = 0.326, p < 0.05; SEE: r = 0.298, p < 0.05) in both groups; it was negatively correlated with AL (r = −0.476, p < 0.001) in the MEE group but not in the SEE group (p > 0.05). CCT was negatively correlated with AL (r = −0.289, p < 0.05) and ACV positively correlated with AL (r = 0.444, p < 0.001) in the MEE group. Neither CCT nor ACV was correlated with AL (p > 0.05) in the SEE group.Conclusion: Corneal biomechanical parameter SSI, which represents the stiffness of corneal tissue, was lower in the SEE group than in the MEE group. When analyzed separately, SSI was negatively correlated with AL in the MEE group, but not in the SEE group, which may provide insight into different ocular growth patterns between lower myopia and higher myopia.

A STUDY TO DETERMINE THE FUNCTIONAL OUTCOME IN THE MANAGEMENT OF STABLE PER TROCHANTERIC HIP FRACTURES WITH DYNAMIC HIP SCREW.

BACKGROUND: The use of a dynamic hip screw (DHS) for stable as well as unstable intertrochanteric hip fracture xation has been successfully applied in fracture healing for more than 25years. DHS xation on unstable trochanteric fractures still has a more failure rate compared to stable fractures, mostly due to osteoporosis in patients. Thus, this study is aimed to investigate the biomechanical property of the DHS system to provide the stable xation in intertrochanteric A1 and A2 fractures1. MATERIAL AND METHODS: This is a retrospective study of 54 patients with trochanteric fractures of the femur that were treated with DHS (Dynamic hip screw) during the period of two years from April 2019 to March 2021 in a tertiary care hospital. All surgeries were performed under spinal and epidural anaesthesia. Surgery done was an internal xation with DHS plate. Results: Among 54 cases, 55.5% were A1, and 44.4% were A2 pertrochanter fractures. The clinical and functional outcomes of the procedure were excellent in 25 patients (46.29%), good in 19 patients (35.18%), fair in 8 patients (14.81%), and 2 (3.7%) of the patients had poor results. CONCLUSIONS: Intertrochanteric fractures are essentially fractures of the elderly, which demand prompt treatment and early ambulation. The dynamic hip screw is the operative treatment of choice for stable trochanteric fractures

Evaluation of biomechanical properties on partial and complete epitendinous suture in human cadaver flexor tendon repair

Objective This study was designed to compare the ultimate tensile strength and force to 2 mm gap formation among 50% partial, 75% partial, and complete circumferential epitendinous suture with a combination of 4-strand core suture in human cadaver flexor tendon. Materials and methods Forty-five flexor tendons from four soft human cadavers were used to evaluate the biomechanical property among 50% partial, 75% partial, and complete circumferential epitendinous suture with a combination of 4-strand core suture. Results The force to 2 mm gap of complete epitendinous was significantly greater than partial epitendinous suture (P < 0.05); however, there was no difference between 50% partial and 75% partial epitendinous suture (P > 0.05). For the ultimate strength, there was no significant difference between partial and complete epitendinous suture (P > 0.05). The partial epitendinous was approximately 60% of the complete epitendinous suture in force to 2 mm gap and also 70% of complete epitendinous suture in ultimate tensile strength with a combination of core sutures. Conclusions The complete epitendinous suture showed better ultimate tensile strength and force to 2 mm gap compared with a partial 50% and 75% epitendinous suture. However, in some clinical scenario which the complete epitendinous suture is not possible to perform, the authors suggested only partial epitendinous suture with 50% circumference is recommended as the additional epitendinous repair up 75% circumference cannot provide any mechanical benefit to the repaired site.

Preparation and Properties of Antibacterial Polydopamine and Nano-Hydroxyapatite Modified Polyethylene Terephthalate Artificial Ligament

Due to its great biomechanical property, the polyethylene terephthalate (PET) artificial ligament has become one of the most promising allografts for anterior cruciate ligament (ACL) reconstruction. However, because of its chemical and biological inertness, PET is not a favored scaffold material for osteoblast growth, which promotes the ligament-bone healing. Meanwhile, in consideration of prevention of potential infection, the prophylactic injection of antibiotic was used as a post-operative standard procedure but also has the increasing risk of bacterial resistance. To face these two contradictions, in this article we coated a polydopamine (PDA) nano-layer on the PET ligament and used the coating as the adhesion interlayer to introduce nano-hydroxyapatite (nHA) and silver atoms to the surface of PET ligament. Because of the mild self-polymerization reaction of dopamine, the thermogravity analysis (TGA), Raman spectrum, and tensile test results show that the modification procedure have no negative effects on the chemical stability and mechanical properties of the PET. The results of NIH3T3 cell culture show that the PDA and nHA could effectively improve the biocompatibility of PET artificial ligament for fibroblast growth, and staphylococcus aureus antibacterial test results show that the Ag atom provided an antibacterial effect for PET ligament. As shown in this paper, the nano-PDA coating modification procedure could not only preserve the advantages of PET but also introduce new performance characteristics to PET, which opens the door for further functionalization of PET artificial ligament for its advanced development and application.

Assessment of myofascial stiffness of flexor digitorum superficialis muscles in rock climbers

Purpose: Myofascial stiffness is the biomechanical property that can be considered as a modifiable risk factor injury of athletes. Moreover, the level of muscle stiffness can be crucial to assessment muscle adaptation to exercise. However, stiffness of flexor muscles in rock climbers has never been investigated. The purpose of this study was to evaluate the myofascial stiffness of the flexor digitorum superficialis (FDS) in the rock climbers. Methods: The group of rock climbers (n = 16) has been compared to the non-climbers group (n = 16), matched in terms of anthropometric measures and an average level of physical fitness. Moreover, the impact of the one-time rock climbing training on FDS stiffness was assessed in the rock climbers group. The measurement of myotonometric myofascial stiffness of FDS muscles was performed, when the elbow was flexed and fully extended. In both positions, the measurements were taken with the hand open and closed. Results: It has been shown that rock climber’s FDS muscle stiffness before training was significantly higher (from 15 to 20%) compared to non-climbers group. Moreover, after climbing myofascial stiffness of FDS muscles increased significantly from 25 to 40%. Conclusions: Rock climbers have significantly higher stiffness of FDS muscles after rock climbing training. Moreover, the increased stiffness in the FDS differentiates rock climbers from the active and healthy control group. Results may indicate that decrease of muscle stiffness of FDS can be an important factor for the improvement of the climbing effectiveness and prevention of overload in the forearm flexor muscles and their recovery.

Application of Scheimpflug-Based Biomechanical Analyzer and Tomography in Early Detecting of Subclinical Keratoconus in Chinese Patients

PurposeTo evaluate the value of Scheimpflug-based biomechanical analyzer combined with tomography in detecting early keratoconus by distinguishing normal eyes from frank keratoconus (KC) and forme frusta keratoconus (FFKC) eyes in Chinese patients. MethodsThis study included 31 bilateral frank keratoconus patients, 27 unilateral clinical manifest keratoconus patients with very asymmetric eyes, and 79 control subjects with normal corneas. Corneal morphological and biomechanical parameters were measured using the Pentacam HR and Corvis ST (OCULUS, Wetzlar, Germany). The diagnostic capacity of computed parameters reflecting corneal biomechanical and morphological traits [including Belin-Ambrósio deviation index (BAD_D), Corvis biomechanical index (CBI) and tomographic and biomechanical index (TBI)] was determined using receiver operating characteristic (ROC) curves and compared by DeLong test. Additionally, the area under the curve (AUC), the best cutoff values, and Youden index for each parameter were reported. The novel corneal stiffness parameter (Stress-Strain Index or SSI) was also compared between KC, FFKC and normal eyes.ResultsEvery morphological and biomechanical index analyzed in this study was significantly different between KC, FFKC and normal eyes (p=0.000). TBI was most valuable for detecting subclinical keratoconus (FFKC eyes) with an AUC of 0.928 (P=0.000), and any forms of corneal ectasia (FFKC and frank KC eyes) with an AUC of 0.966 (P=0.000). The sensitivity and specificity of TBI for detecting FFKC was 97.5% and 77.8%, for detecting any KC was 97.5% and 89.7%, with a cut-off value of 0.375. Morphological index BAD_D and biomechanical index CBI were also very useful in distinguishing any KC eyes from normal eyes with an AUC of 0.965 and 0.934, respectively. SSI was significantly different between KC, FFKC and normal eyes (P=0.000), indicating an independent decrease in corneal stiffness in KC eyes.Conclusion Combination of Scheimpflug-based biomechanical analyzer and tomography could increase the accuracy of detecting early keratoconus in Chinese patients. TBI was the most valuable index for detecting subclinical keratoconus with high sensitivity and specificity. Evaluation of corneal biomechanical property in refractive surgery candidates is helpful to recognize potential keratoconic eyes and increase surgical safety.

INCUBATION OF PLATELET-RICH FIBRIN MATRIX WITH MESENCHYMAL STEM CELLS IMPROVES MATRIX STIFFNESS

Objective: The platelet-rich fibrin matrix (PRFM) is condensed platelet-rich plasma (PRP) and should possess a comparable biomechanical property to the transplanted sites, for them to be physiologically functional. The aim of this study was to investigate the effect of human bone marrow mesenchymal stem cells (hBM-MSC) or human umbilical cord mesenchymal stem cells (hUC-MSC) on the biomechanical properties of PRFM. Methods: PRFM was prepared by the gelation of PRP using 25 mmol CaCl2. The resulting coin-shaped PRFM pellets, 5 cm in diameter and 300 μm thick, were directly seeded with hUC-MSC or hBM-MSC at 2,000 cells cm-2, followed by 24 h incubation at 37 °C in 5% (v/v) CO2 in air. The samples were then observed by scanning electron microscopy to determine the morphology of the matrix surface. The PRFM biomechanical properties were determined at a 10 mm. min-1failure rate using an MCT 2150 universal testing machine (AandD Co. LTD). Results: SEM imaging of the surface of the PRFM seeded with hBM-MSC and hUC-MSC showed a cloudy layer that thickened over time. The elastin slope of the PRFM was significantly improved after seeding with hBM-MSC and hUC-MSC when compared with unseeded PRFM (p<0.002, R2=0.983). Both cell types elicited similar biomechanical effects (p=0.99). Conclusion: PRFM seeded with hBM-MSC or hUC-MSC showed significantly increased elasticity.

Will the Strength of the Clavicle Plate be Increased by Inserting Small Screws into the Empty Holes above the Fracture Site?

Background: Open reduction and plate fixation is the standard surgery for displaced midshaft clavicle fractures because of biomechanical stability. Implant failure like plate breakage or deformation is the most serious complication of plate fixation. Several plate designs for midshaft clavicle fractures have been introduced, but traditional superior plate has been mostly used.Methods: We generated the clavicle 3D image using the computed tomography (CT) of the left normal clavicle of a 54-year-old female, and then made the comminuted midshaft clavicle fracture model with 10-mm fracture site gap. The fracture model was fixed with 7-hole superior locking compression plate. Finite element analysis (FEA) was performed between the presence (model B) and absence (model A) of screws above the fracture site.Results: The average peak stress from the cantilever bending force was much greater than the peak stress from the axial compression and axial torsion force. This means that the cantilever loading force is the main force which could cause plate breakage or deformation. The maximal stress of the model B was lower than the one of the model A. Therefore, model B showed superior biomechanical property than model A under all loading conditions, especially cantilever bending force.Conclusions: The peak stress of the superior clavicle plate could be decreased just by inserting a small screw into the screw hole above the fracture site.

Rapid preparation of decellularized trachea as a 3D scaffold for organ engineering

Objective: To shorten the preparation time of rabbit decellularized tracheal matrix through a modified detergent-enzymatic method with higher concentration of DNase (50 kU/mL), providing an experimental and theoretical basis for clinical decellularization technology. Methods: The control group was a natural trachea, and the experimental group was a tracheal matrix subjected to two and four decellularization cycles. The performance of each group of samples was evaluated by histology and immunohistochemical staining, scanning electron microscopy, biomechanical property testing, inoculation and cytotoxicity tests, and allograft experiments. Results: The results showed that the nuclei of the nonchondral areas of the tracheal stroma were essentially completely removed and MHC-I and MHC-II antigens were removed after two decellularization cycles. Histological staining and scanning electron microscopy showed that the extracellular matrix was retained and the basement membrane was intact. Cell inoculation and proliferation tests confirmed that the acellular tracheal matrix had good biocompatibility, and the proliferation capacity of bone mesenchymal stem cells on the matrix was increased in the experimental group compared with the control group ( p < 0.05). Histological staining and CD68 molecular marker analysis after the allograft experiment showed that the inflammatory response of the acellular tracheal matrix was weak and the infiltration of surrounding macrophages was reduced. Conclusion: A modified detergent-enzymatic method with an increased DNase (50 kU/mL) concentration requires only two cycles (4 days) to obtain a decellularized rabbit tracheal matrix with a short preparation time, good biocompatibility, suitable mechanical properties, and reduced preparation cost.

Correlation of ocular rigidity with intraocular pressure spike after intravitreal injection of bevacizumab in exudative retinal disease

Background/aimsTo evaluate the non-invasive measurement of ocular rigidity (OR), an important biomechanical property of the eye, as a predictor of intraocular pressure (IOP) elevation after anti-vascular endothelial growth factor (anti-VEGF) intravitreal injection (IVI).MethodsSubjects requiring IVI of anti-VEGF for a pre-existing retinal condition were enrolled in this prospective cross-sectional study. OR was assessed in 18 eyes of 18 participants by measurement of pulsatile choroidal volume change using video-rate optical coherence tomography, and pulsatile IOP change using dynamic contour tonometry. IOP was measured using Tono-Pen XL before and immediately following the injection and was correlated with OR.ResultsThe average increase in IOP following IVI was 19±9 mm Hg, with a range of 7–33 mm Hg. The Spearman correlation coefficient between OR and IOP elevation following IVI was 0.796 (p<0.001), showing higher IOP elevation in more rigid eyes. A regression line was also calculated to predict the IOP spike based on the OR coefficient, such that IOP spike=664.17 mm Hg·µL×OR + 4.59 mm Hg.ConclusionThis study shows a strong positive correlation between OR and acute IOP elevation following IVI. These findings indicate that the non-invasive measurement of OR could be an effective tool in identifying patients at risk of IOP spikes following IVI.