Mean Stiffness Values Research Articles

In vitro mechanical analysis of X-shaped femoroplasty with polymethyl methacrylate boundary a fall on the greater trochanter,

To evaluate with mechanical testing (MT) using synthetic femurs, an X-shaped femoroplasty technique with polymethyl methacrylate (PMMA), analyzing the results applied to the prophylaxis of proximal femur (PF) fractures caused by low-energy trauma. MT was performed simulating a fall on the greater trochanter, using fifteen Sawbones™ models. They were divided into three experimental groups (n = 5): control (DP) group, drilled without augmentation (DWA) group, and X-shaped augmentation (DX) group. Maximum load, stiffness, absorbed energy and displacement were analyzed primarily in all groups; and secondarily then, morphology and fracture type were verified in all groups while PMMA volume, temperature and time polymerization were analyzed only in the DX group. The MT results obtained for synthetic models respectively in the DP, DWA, and DX groups were: mean maximum load (5562.0 ± 464.8) N, (4798.0 ± 121.2) N, and (7132.0 ± 206.9) N; mean stiffness values (673 ± 64.34) N/mm, (636 ± 8.7) N/mm, and (738 ± 17.13) N/mm, and mean absorbed energy values (36,203 ± 3819) N.mm, (27,617 ± 3011) N.mm, (44,762 ± 3219) N.mm; mean displacement values (13.6 ± 1.45) N, (11.1 ± 0.5) N, and (13.2 ± 0.69) N. The mean volume, temperature reached during filling in the DX group were 9.8 mL, 42.54ºC with 1ʹ 56ʺ of polymerization. The fracture types were similar between the DP and DWA groups, affecting the trochanteric region, as distinctly to those in the DX group, which were restricted to the femoral neck. The values obtained in MT showed statistical significance when analyzed by one-way ANOVA (5%) for maximum load, stiffness, and absorbed energy between groups. In conclusion, X-shaped PMMA augmentation presents a protective biomechanical characteristic against PF fractures generated in synthetic models by boundary a fall on the greater trochanter.

Liver and spleen volume and stiffness in patients post-Fontan procedure and patients with ARPKD compared to normal controls

PurposeBoth congestive (patients post-Fontan hepatopathy) and congenital (patients with ARPKD) disease can lead to hepatic fibrosis and portal hypertension with eventual development of splenomegaly. We investigated liver and spleen stiffness as measured by MRE between post-Fontan, ARPKD patients and controls independent of organ volume. MethodsOur study included 122 subjects (70 Fontan patients, 14 ARPKD patients, and 38 controls). The mean MRE liver and spleen stiffness values of Fontan patients and patients with ARPKD were compared to controls. Similarly, the liver and spleen volumes of the Fontan patients and patients with ARPKD were then compared to the volumes of controls. ResultsPost-Fontan and ARPKD patients, mean liver stiffness, mean liver volume as well as mean spleen stiffness and mean spleen volume were higher than mean liver stiffness, mean liver volume, mean spleen stiffness, and mean spleen volume of controls. While liver stiffness correlated to liver volume in controls, we found no correlation between stiffness and volume in either Fontan or ARPKD patients, which indicates MRE's ability to act as an independent biomarker. However, these findings are not true in the spleen, where there is significant association between volume and stiffness in patients with ARPKD, but not in Fontan patients or controls. ConclusionLiver and spleen stiffness and volumes are significantly different among Fontan patients, ARPKD patients, and controls. Our findings suggest that beyond diagnosing fibrosis, MRE cut-off values could be disease-specific since not only the severity but the underlying pathology causing organ congestion or fibrosis influences MRE results.

Testes Parenchymal Shear Wave Elastography Findings in Varicocele.

To investigate the testicular parenchymal changes in patients with varicocele using shear wave elastography (SWE). Cross-sectional study. Department of Radiology, Hatay Mustafa Kemal, School of Medicine, Hatay, Turkey, between June and August 2021. The study was conducted on 124 testes of 62 patients who had undergone scrotal ultrasonography. Using the SWE technique, the mean velocity and stiffness values of each testis were measured and recorded, and varicocele volume was calculated by measuring testis volume and the Pampiniform plexus (pp) vein diameter on Doppler examination. After the exclusion criteria, 55 (44.3%) testes with varicocele and 69 (55.6%) testes without varicocele were examined. The relationship between the SWE values of testis volume and the presence and volume of varicocele was evaluated statistically. The mean velocity value was 0.76 ± 0.08 m/s in the varicocele group and 0.85 ± 0.13 m/s in the without varicocele group; the mean stiffness value was 1.76 ± 0.37 KPa in the varicocele group and 2.25 ± 0.54 KPa in the without varicocele group. The SWE values were found to be significantly lower in testes with varicocele than in those without (p<0.001). The mean testis volume was 13.5 ± 4.6 in the varicocele group and 13.8 ± 4.4 in the without varicocele group. No statistically significant relationship was determined between the presence of varicocele and testis volume (p=0.670). A significant negative correlation was found between plexus pampiniform diameter and velocity (rs=-0.405, p=0.002) and stiffness (rs =-0.399, p=0.003) values. SWE findings can provide information about testicular damage associated with varicocele. Furthermore comprehensive studies may be of importance in varicocele treatment. Shearwave elastography (SWE), Testis, Varicocele, Parenchymal stiffness.

The effect of onlay cortical fibula strut grafts on biomechanical features of Vancouver type B1 periprosthetic femoral fractures.

This study aimed to investigate biomechanically the effects of onlay fibula grafts on Vancouver Type B1 Periprosthetic Femoral Fractures (PPFs). Vancouver Type B1 PFF models were created in 25 fourth-generation synthetic femurs and fixed with locking plates using bicortical, unicortical screws, and cables. While no graft was used in group 1, onlay fibula grafts were placed anteriorly in group 2 and medially in group 3. In group 4, the cortical strut allograft was placed on the medial femoral cortex, and a locking compression plate (LCP) was applied to the lateral femoral cortex. In group 5, the strut allograft was placed over the anterior cortex of the femur and fixed with the same technique as in group 4. All models were then subjected to rotational and axial cyclical stiffness tests and load to failure to measure and compare the mechanical strengths of the constructs. The mean stiffness values of group 4 with medial allograft, before and after cyclical loading, were higher than all other groups, under both rotational and axial forces. The mean stiffness values of fibula autografts (groups 2 and 3) were similar to that of anterior allografts (group 5) in each test except that the mean initial axial stiffness of group 5 was higher than group 2. Failure loads were also not different between the groups. Although the rigidity of Vancouver type B1 periprosthetic femur fractures is highest if allografts are placed medially, fibula autografts can also provide similar fixation strengths to allografts if locking plates with unicortical and bicortical screws and cables are used.

Deep neural networks for magnetic resonance elastography acceleration in thermal-ablation monitoring.

To develop a deep neural network for accelerating magnetic resonance elastography (MRE) acquisition, to validate the ability to generate reliable MRE results with the down-sampled k-space data, and to demonstrate the feasibility of the proposed method in monitoring the stiffness changes during thermal ablation in a phantom study. MRE scans were performed with 60Hz excitation on porcine ex-vivo liver gel phantoms in a 0.36T MRI scanner to generate the training dataset. The acquisition protocol was based on a spin-echo MRE pulse sequence with tailored motion-sensitive gradients to reduce echo time (TE). A U-Net based deep neural network was developed and trained to interpolate the missing data from down-sampled k-space. We calculated the errors of 80 sets magnitude/phase images reconstructed from the zero-filled, compressive sensing (CS) and deep learning (DL) method for comparison. The peak signal-to-noise rate (PSNR) and structural similarity index (SSIM) of the magnitude/phase images were also calculated for comparison. The stiffness changes were recorded before, during, and after ablation. The mean stiffness values over the region of interest (ROI) were compared between the elastograms reconstructed from the fully sampled k-space and interpolated k-space after thermal ablation. The mean absolute error (MAE), PSNR, and SSIM of the proposed DL approach were significantly better than the results from the zero-filled method (p<0.0001) and CS (p<0.0001). The stiffness changes before and after thermal ablation assessed by the proposed approach (before: 7.7±1.1kPa, after: 11.9±4.0kPa, 4.2-kPa increase) gave close agreement with the values calculated from the fully sampled data (before: 8.0±1.0kPa, after: 12.6±4.2kPa, 4.6-kPa increase). In contrast, the stiffness changes computed from the zero-filled method (before: 4.9±1.4kPa, after: 5.6±2.8kPa, 0.7-kPa increase) were substantially underestimated. This study demonstrated the capability of the proposed DL method for rapid MRE acquisition and provided a promising solution for monitoring the MRI-guided thermal ablation.

Tissue stiffness in BPH patients from magnetic resonance elastography

BackgroundBPH is commonly found in older men which can lead to lower urinary tract symptoms. Magnetic resonance elastography (MRE) is an innovative, noninvasive imaging technique used to evaluate tissue stiffness. There has not been any study, however, that assessed the tissue stiffness in patients with BPH. A prospective descriptive study was performed to demonstrated MRI and MRE techniques of the prostate gland in ten patients with BPH to assess tissue stiffness, features of BPH on MRI and components of BPH in the area of increased stiffness.ResultsMRI and MRE examinations in all patients were successful without any complications. The mean tissue stiffness of the whole prostate gland was 4.40 ± 0.71 kPa with good reproducibility (ICC 0.82). Stromal components and mixed glandular-stromal components tended to be associated with the areas of increased stiffness on stiffness images, 50.6% for stromal components and 37.9% for mixed glandular-stromal components. Some MRI findings were seen on the patients with high mean stiffness values such as prostatic calcification, type-5 BPH pattern and large prostate volumes.ConclusionsProstate MRE is a useful noninvasive reproducible diagnostic tool for evaluating prostate tissue stiffness by both qualitative and quantitative assessments. The mean prostate tissue stiffness from MRE in patients with BPH in this study was 4.40 ± 0.71 kPa. Some MRI features might be associated with increased tissue stiffness.Trial registration: PID 229. Registered 4 October 2019. http://md.redcap.kku.ac.th

Shear-wave elastography evaluation of adrenal glands in healthy newborns: a preliminary study.

Establishing standard shear-wave elastography (SWE) values for healthy newborns can help distinguish normal conditions of the adrenal gland (AG) from pathological conditions. We aimed to establish a reference data set for AG stiffness values using SWE in healthy newborns. The quantitative stiffness of the AG was measured in the coronal plane in kilopascal (kPa). The quantitative descriptive statistics were presented as mean with standard deviation and median with range. The relationship between the quantitative variables was calculated using "Spearman's rank correlation coefficient test." The intraclass correlation coefficient (ICC) test was used to analyze intraobserver reliability. A p-value <0.05 was considered statistically significant. A total of 120 AGs of 60 healthy newborns (30 females and 30 males) was examined. The mean stiffness values of the right AG for the first and second visits were 7.51±2.45 and 7.54±2.49 kPa, respectively, and those of the left AG for the first and second visits were 7.60±2.03 and 7.42±1.97 kPa, respectively. There was no statistically significant difference between the mean values of adrenal stiffness and the length and width of AG and weight, height, and age (p>0.05). The ICC values for mean stiffness values of each AG were >0.80-0.90, indicating good intraobserver agreement. This study is the first SWE study to evaluate the AG in healthy newborns. Our study's data can be used as a reference for future research.

Measuring stiffness of normal medial collateral ligament in healthy volunteers via shear wave elastography.

We aim to determine a reference data set for normal medial collateral ligament (MCL) stiffness values using shear wave elastography (SWE). Quantitative stiffness of the MCL was measured at three levels: the proximal (MCL area from the level of the medial meniscus to the level of the femoralattachment), the middle (MCL area at the level of the medial meniscus), and the distal (MCL area from the level of the medial meniscus to the level of the tibialattachment) segments of the MCL at a knee position of 0°. A total of 60 MCL of 30 healthy volunteers (15 female, 15 male) were examined. The mean stiffness values of the proximal, middle, and distal MCL for observer 1 were 32.25 ± 6.44, 34.25 ± 6.84, and 35.47 ± 6.98, respectively. The mean stiffness values of the proximal, middle, and distal MCL for observer 2 were 33.56 ± 6.76, 35.44 ± 6.91, and 36.32 ± 7.04, respectively. SWE has a strong potential to be a method of choice for evaluating MCL stiffness. Our study participants were healthy volunteers and the data can be used as reference data for future studies.

Quantitative assessment of temporomandibular disc and masseter muscle with shear wave elastography.

To assess the normal stiffness values of temporomandibular joint disc (TMJ) and masseter muscle by shear wave elastography (SWE) in a healthy adult population. This may be helpful in diagnosing and understanding the mechanism of temporomandibular disorders (TMD). This prospective study evaluated a total of 160 healthy adult volunteers (77 males, 83 females). The stiffness values of anterior, intermediate and posterior parts of the TMJ disc and masseter muscle were measured. Study cohort was classified into four groups based on age. Additionally, we investigated the changes in mean shear wave elasticity (kPa) and shear wave velocity(m/s) values of disc parts and masseter muscle in closed and open mouth positions, and the correlation of these SWE values with age and gender. Mean stiffness values of the disc were 37.02 ± 23.75kPa and 3.28 ± 1.09m/s in the anterior part, 30.47 ± 18.89kPa and 2.97 ± 1.04m/s in the intermediate part, 22.61 ± 13.97kPa and 2.55 ± 0.88m/s in the posterior part. Stiffness values showed significant decrease in the posterior part compared to the rest of the disc both in males and females. No significant differences in mean stiffness values of masseter muscle related to mouth position, age or gender. This study provides the normative quantitative elasticity values of disc and masseter muscle which could be a reference point for upcoming studies. Disc elasticity values are higher in women than men. Maybe this is one of the reason why TMD is more common in women. TMJ disc stiffness was significantly lower in the posterior part. SWE is a useful imaging method that can be used with routine ultrasonography in evaluation of the TMJ disc and masticatory muscles .

Virtual magnetic resonance elastography has the feasibility to evaluate preoperative pituitary adenoma consistency

PurposeTo evaluate the use of preoperative virtual Magnetic Resonance Elastography (vMRE) for patients undergoing transsphenoidal resection of pituitary adenomas (PA).MethodsTen patients (60.2 ± 19.6 years; 8 males) were prospectively examined with the vMRE-method prior to transsphenoidal surgery. vMRE-images, reflecting tissue stiffness were reconstructed. From these images, histograms as well as the mean stiffness values over the tumor body were extracted. Finally, vMRE-data was compared with the PA consistency at surgery blinded to vMRE.ResultsIn all patients, successful vMRE-examination was performed enabling evaluation of even small PAs. For tumors with homogenous tissue, the mean stiffness value increased with surgical consistency grading. For heterogenous tumors, however, the mean stiffness value did not consistently reflect the grading at surgery. On the other hand, the vMRE-images and histograms were found to be able to characterize the tumor heterogeneity and display focal regions of high stiffness that were found to affect the surgery outcome in these PAs. The vMRE-images and histograms showed great promise in characterizing the consistency at surgery for these PAs.ConclusionEvaluation of PA consistency in preparation for surgery seems to be feasible using the vMRE-method. Our findings also address the need for high resolution diagnostic methods that can non-invasively display focal regions of increased stiffness, as such regions may increase the difficulty of transsphenoidal PA-resection.

Reliability of Human Achilles Tendon Stiffness Measures Using Freehand 3-D Ultrasound

Achilles tendon (AT) stiffness is an important property of both human locomotor performance and injury mechanics. Freehand 3-D ultrasound (3-DUS) is a promising method for measuring stiffness of the Achilles tendon, particularly the free AT (2–6 cm proximal to calcaneus), which is commonly injured. The aim of this study was to investigate the test–retest reliability of freehand 3-DUS in measuring free AT stiffness in humans. The free Achilles tendon length of healthy participants (n = 10) was scanned on the same day on two consecutive occasions (1 h apart) during rest and isometric plantar flexion contractions at 20%, 40% and 60% of maximum force. The slope of the force–elongation curve over these force levels represented individual stiffness (N/mm). Relative reliability was assessed using the intra-class correlation coefficient (ICC), and absolute reliability was estimated with the standard error of measurement (SEM) and smallest detectable change. Systematic bias in stiffness measures was explored by comparing test and retest distributions and Bland–Altman plots. The test–retest reliability of free AT stiffness measured using freehand 3-DUS was excellent [ICC = 0.994, 95% confidence interval [CI]: 0.978–0.999)]. The mean stiffness values at test (361.83 N/mm [170.77]) and retest (364.98 N/mm [168.57]) did not significantly differ (p = 0.72), and the smallest detectable change was 52.14 N/mm. The Bland–Altman plot indicated the absence of systematic bias (95% CI: –22.18 to 15.88). Freehand 3-DUS provides reliable and precise measures of tendon stiffness and can be used to detect small changes in free AT stiffness in response to load or tendon pathology.

Comparison of five percutaneous pinning methods for unstable extra-articular distal radius fractures: A mechanical study using sawbones.

Objectives This study aims to mechanically compare five different extra-focal bi-cortical pin configurations (using two and three pins) employed for fixation of a simulated unstable extra-articular distal radius fracture with dorsal comminution using a sawbone model.Materials and methods This in vitro mechanical study was conducted between June 2019 and July 2019. A standard fracture model (Arbeitsgemeinschaft für Osteosynthesefragen [AO] type 23-A3.3) was created using a fourth generation composite artificial radius bone. Five groups with two- and three-pin configurations were tested under axial, volar, and dorsal loading with a universal test device. Mean stiffness values were compared statistically.Results Comparison of stiffness values from axial and volar loading tests between groups in paired comparison showed no statistically significant difference (p=0.194 and p=0.086, respectively). Dorsal loading tests showed statistically significant difference between the groups in pairwise comparison (p=0.002). Three-pin groups (Groups 3, 4, and 5) had higher stiffness values compared to two-pin groups (Groups 1 and 2) in dorsal loading tests (p=0.001). Three-pin configuration test groups with two divergent or convergent pins from the radial styloid performed better compared to both two-pin groups (p=0.01, p=0.002) in dorsal loading tests.Conclusion Our data demonstrated that the three-pin configuration with two divergent or convergent Kirschner wires from the styloid and a third wire from the dorsal/ulnar cortex had higher stiffness values compared to two-pin configurations in dorsal loading tests. When indicated, we suggest the use of a three-pin construct. Particularly in cases with a risk of volar angulation, we recommend a three-pin configuration with two divergent or convergent bi-cortical Kirschner wires.

Shear wave elastography of temporomandibular joint disc and masseter muscle stiffness in healthy children and adolescents: a preliminary study.

Shear wave elastography (SWE) are promising techniques in diagnosing temporomandibular joint (TMJ) disc and masseter muscle disorders. To investigate normative stiffness values of the TMJ disc and masseter muscle by SWE in children and adolescents. This prospective study evaluated 123 TMJ discs and masseter muscles in 123 subjects. The stiffnesses of anterior, middle, and posterior parts of the disc and the masseter muscle were measured. This study investigated differences in mean elasticity [kilopascal (kPa)] and velocity [metre/second (m/s)] values of the different disc parts and the masseter muscle in closed and open mouth positions, and the correlations of these SWE values with age, body mass index (BMI), height, and weight of the subjects. The median stiffness disc values of all participants were 28.7kPa (elasticity) and 3.07m/s (velocity) for the anterior, 29.10kPa and 3.07m/s for the middle, and 23.2kPa and 2.77m/s for the posterior parts. Posterior stiffness was significantly lower than other body regions in all subjects and across all age groups. The mean stiffness values of the muscle were 16.96 ± 9.01kPa and 2.33 ± 1.2m/s for the closed mouth, and 28.7 ± 10.2kPa and 3.23 ± 1.32m/s for the open mouth. The stiffness of the TMJ disc was significantly lower in the posterior part than in the anterior or middle parts. The mean stiffness was significantly higher in the open mouth than in the closed mouth position. Neither elasticity nor velocity were associated with age, height, weight, or BMI.

Shear Wave Elastography Evaluation of Meniscus Degeneration with Magnetic Resonance Imaging Correlation

The objective of the study was to assess the diagnostic efficiency of shear wave elastography in the grading of meniscal degeneration compared to magnetic resonance imaging (MRI) as a reference standard. Fifty patients were included in the study (who had bilateral knee MRI). Tissue elasticity was measured in the coronal plane from the meniscus body in kilopascal. Nonparametric testing (Mann-Whitney U) was utilized to assess the differences between mean elasticity of the meniscus tissue, gender. The inter-intraobserver agreement was determined by the intraclass correlation coefficient. The correlations between the mean elasticity of the meniscus versus age, height, and body mass index were calculated via the "Pearson Correlation Coefficient Test." The relationship between MRI meniscal degeneration grading and elastography elasticity module was determined via the "Spearman Correlation Test." A p value less than 0.05 was considered statistically significant. İnter-intraobserver intraclass correlation coefficient of the lateral and medial meniscus mean stiffness values were good or excellent (>0.8). A statistically significant increase in stiffness of meniscus tissue was observed with an increase in age (p = 0.003 for medial menisci, 0.006 for lateral menisci). Tissue stiffness was higher in the medial meniscus than the lateral meniscus (p < 0.001). A positive correlation was observed between the MRI meniscal degeneration grade and tissue stiffness (p < 0.05). Additionally, mean stiffness values from lateral and medial menisci were higher in the group with degeneration (p < 0.0001). Meniscus stiffness is increased with aging. There was a statistically significant positive correlation between meniscal stiffness and degeneration grading in MRI.

Biomechanical Effects of Δ9-Tetrahydrocannabinol (THC) and Cannabidiol (CBD), the Major Constituents of Cannabis, in a Sprague Dawley Rat Achilles Tendon Surgical Repair Model

Category:Sports; HindfootIntroduction/Purpose:Use of Cannabis is common amongst athletes and the U.S. population at large. Use of Cannabinoid Oil is being increasingly utilized for a number of different pathologies, injuries, and ailments due to anecdotal evidence of its efficacy. Due to the current United States Opioid crisis, Δ9-Tetrahydrocannabinol (THC) and Cannabidiol (CBD), the two major constituents of cannabis, are currently being evaluated as potential safer alternatives to narcotic pain medicines. The effects of recreational and/or therapeutic THC and CBD on musculoskeletal injury and healing however remain largely unknown. Our purpose was to evaluate the biomechanical effects of THC and CBD on tendon to tendon healing in a Sprague Dawley Achilles Tendon injury and surgical repair model.Methods:33 Sprague Dawley rats were randomly assigned into control (1 ml/kg/day of vehicle containing 5% Cremaphor, 5% ethanol, and 0.9% saline n=12), THC (3 mg/kg/day n = 12), or CBD (3 mg/kg/day n=9) treatment groups. Surgical transection and repair of the Achilles tendon was performed and all rats began subcutaneous administration of their respective drug treatment the day of surgery and for 4 subsequent days, followed by sacrifice. Load to failure and stiffness were calculated from load displacement data during tensile load testing on a MTS machine. One-way ANOVA with heterogeneous variance was utilized for evaluation. Means and 95% confidence intervals were also determined.Results:The CBD group demonstrated the highest mean load to failure of 17.5 N (15.1-19.8 N), with the THC group having the second highest mean load to failure at 17.3 N (15.3-19.2 N), and the control group reporting the lowest at 15.2 N (12.1-18.3 N). No statistical difference was observed between CBD/control (p = 0.25), THC/control (p = 0.29), or CBD/THC groups (p = 0.92, Figure 1A). The THC group reported the highest mean stiffness of 3.9 N/mm (2.7-5.1 N/mm). The CBD and control groups demonstrated mean stiffness values of 3.5 N/mm (2.9-4.1 N/mm) and 3.5 N (2.7-4.3 N/mm), respectively. No statistically significant differences were observed between THC/control (p = 0.51), THC/CBD (p = 0.50), or CBD/control groups (p = 0.96) for stiffness (Figure 1B).Conclusion:Our investigation demonstrates that subcutaneous administration of CBD resulted in the highest mean load to failure, while THC administration resulted in the highest mean stiffness of the three groups. This did not result however in a statistically significant difference between groups. In our small animal tendon-to-tendon repair model, use of THC or CBD did not result in decreased biomechanical characteristics, and there was a trend toward improved ultimate strength and stiffness as compared to control. Further evaluation with larger numbers of animals, and evaluating the potential synergistic effects of THC and CBD administered together are warranted.

Fusing acceleration and saturation techniques with wave amplitude labeling of time-shifted zeniths MR elastography.

To design a new 2D gradient recalled echo MR elastography (MRE) pulse sequence with inflow saturation for measuring liver stiffness in half the breath-hold time compared to standard of care (SC) 2D GRE MRE sequences. FASTWALTZ (fusing acceleration and saturation techniques with wave amplitude labeling of time-shifted zeniths) MRE employs an interleaved dual TR strategy with wave amplitude labeling and compressed SENSE undersampling to reduce breath-hold time while incorporating inflow saturation to suppress flow artifacts. The sequence was implemented and compared with SC MRE both in phantoms and in vivo in 5 asymptomatic volunteers. Stiffness values, region of interest size, and breath-hold times were compared between sequences. Stiffness values were comparable between FASTWALTZ and SC MRE for both phantoms and in-vivo data. In volunteers, the group mean stiffness values at 60Hz and region of interest size were 1.96 ± 0.30 kilopascals and 2279 ± 516 mm2 for SC MRE, and 1.95 ± 0.29 kilopascals and 2061 ± 464 mm2 for FASTWALTZ. Breath-hold duration for FASTWALTZ was 6.3 s compared to 13.3 s for SC MRE. FASTWALTZ provides comparable stiffness values in half the breath-hold time compared to SC MRE and may have clinical benefits in patients with limited breath-holding capacity.

Biomechanical Effects of Δ9-Tetrahydrocannabinol (THC) and Cannabidiol (CBD), the Major Constituents of Cannabis, on Tendon to Tendon Healing in a Sprague Dawley Rat Achilles Tendon Surgical Repair Model

Objectives:Use of Cannabis is common amongst athletes and the U.S. population at large. Use of Cannabinoid Oil is being increasingly utilized for a number of different pathologies, injuries, and ailments due to anecdotal evidence of its efficacy. Due to the current United States Opioid crisis, Δ9-Tetrahydrocannabinol (THC) and Cannabidiol (CBD), the two major constituents of cannabis, are currently being evaluated as potential safer alternatives to narcotic pain medicines. The effects of recreational and/or therapeutic THC and CBD on musculoskeletal injury and healing however remain largely unknown. Our purpose was to evaluate the biomechanical effects of THC and CBD on tendon to tendon healing in a Sprague Dawley Achilles Tendon injury and surgical repair model.Methods:33 Sprague Dawley rats were randomly assigned into control (1 ml/kg/day of vehicle containing 5% Cremaphor, 5% ethanol, and 0.9% saline n=12), THC (3 mg/kg/day n = 12), or CBD (3 mg/kg/day n=9) treatment groups. Surgical transection and repair of the Achilles tendon was performed and all rats began subcutaneous administration of their respective drug treatment the day of surgery and for 4 subsequent days, followed by sacrifice. Load to failure and stiffness were calculated from load displacement data during tensile load testing on a MTS machine. One-way ANOVA with heterogeneous variance was utilized for evaluation. Means and 95% confidence intervals were also determined.Results:The CBD group demonstrated the highest mean load to failure of 17.5 N (15.1-19.8 N), with the THC group having the second highest mean load to failure at 17.3 N (15.3-19.2 N), and the control group reporting the lowest at 15.2 N (12.1-18.3 N). No statistical difference was observed between CBD/control (p = 0.25), THC/control (p = 0.29), or CBD/THC groups (p = 0.92, Figure 1A). The THC group reported the highest mean stiffness of 3.9 N/mm (2.7-5.1 N/mm). The CBD and control groups demonstrated mean stiffness values of 3.5 N/mm (2.9-4.1 N/mm) and 3.5 N (2.7-4.3 N/mm), respectively. No statistically significant differences were observed between THC/control (p = 0.51), THC/CBD (p = 0.50), or CBD/control groups (p = 0.96) for stiffness (Figure 1B).Conclusion:Our investigation demonstrates that subcutaneous administration of CBD resulted in the highest mean load to failure while THC administration resulted in the highest mean stiffness of the three groups. This did not result however in a statistically significant difference between groups. In our small animal tendon-to-tendon repair model, use of THC or CBD did not result in decreased biomechanical characteristics, and there was a trend toward improved ultimate strength and stiffness as compared to control. Further evaluation with larger numbers of animals, and evaluating the potential synergistic effects of THC and CBD administered together are warranted.Figure 1.

Shear Wave Elastographic Study of the Myotendinous Junction of the Medial Gastrocnemius: Normal Patterns and Dynamic Evaluation.

The myotendinous junction (MTJ) represents a specialized anatomic region through which the contractile strength is transmitted from the muscle to the tendon. The integrity of this region is essential to permit force transmission and to optimize energy expenditure during walking, running, and globally for human movement. We evaluated the MTJ with shear wave elastography to assess its elasticity variation during a functional test. Forty professional soccer players were enrolled in the study. Shear wave elastography was performed at the level of the medial gastrocnemius MTJ both in a resting position and during a standing calf rise position to assess functional contraction. All 40 participants were male, aged between 18 and 38 years (mean age, 25 years). The results of the elastographic study showed mean stiffness values ± SD of 4.19 ± 0.86 m/s for the right medial gastrocnemius and 4.20 ± 0.87 m/s for the left medial gastrocnemius with the muscle relaxed. During contraction, the stiffness values were 8.33 ± 0.5 m/s for the right medial gastrocnemius and 8.30 ± 0.48 m/s for the left medial gastrocnemius. Our study showed an increase of stiffness at the level of the MTJ during muscle contraction. This result is in line with the physiologic stiffening of the MTJ to resist the high level of force applied during muscle contraction. Shear wave elastography could be a useful method to assess the characteristics of the MTJ under both physiologic and pathologic conditions.

A novel technique for the assessment of mechanical properties of vascular tissue

Accurate estimation of mechanical properties of the different atherosclerotic plaque constituents is important in assessing plaque rupture risk. The aim of this study was to develop an experimental set-up to assess material properties of vascular tissue, while applying physiological loading and being able to capture heterogeneity. To do so, a ring-inflation experimental set-up was developed in which a transverse slice of an artery was loaded in the radial direction, while the displacement was estimated from images recorded by a high-speed video camera. The performance of the set-up was evaluated using seven rubber samples and validated with uniaxial tensile tests. For four healthy porcine carotid arteries, material properties were estimated using ultrasound strain imaging in whole-vessel-inflation experiments and compared to the properties estimated with the ring-inflation experiment. A 1D axisymmetric finite element model was used to estimate the material parameters from the measured pressures and diameters, using a neo-Hookean and Holzapfel–Gasser–Ogden material model for the rubber and porcine samples, respectively. Reproducible results were obtained with the ring-inflation experiment for both rubber and porcine samples. Similar mean stiffness values were found in the ring-inflation and tensile tests for the rubber samples as 202 kPa and 206 kPa, respectively. Comparable results were obtained in vessel-inflation experiments using ultrasound and the proposed ring-inflation experiment. This inflation set-up is suitable for the assessment of material properties of healthy vascular tissue in vitro. It could also be used as part of a method for the assessment of heterogeneous material properties, such as in atherosclerotic plaques.

Simultaneous multislice rapid magnetic resonance elastography of the liver.

To design and validate a rapid Simultaneous Multi‐slice (SMS) Magnetic Resonance Elastography technique (MRE), which combines SMS acquisition, in‐plane undersampling and an existing rapid Magnetic Resonance Elastography (MREr) scheme to allow accelerated data acquisition in healthy volunteers and comparison against MREr. SMS‐MREr sequence was developed by incorporating SMS acquisition scheme into an existing MREr sequence that accelerates MRE acquisition by acquiring data during opposite phases of mechanical vibrations. The MREr sequence accelerated MRE acquisition by acquiring data during opposite phases of mechanical vibrations. Liver MRE was performed on 23 healthy subjects using MREr and SMS‐MREr sequences, and mean stiffness values were obtained for manually drawn regions of interest. Linear correlation and agreement between MREr‐ and SMS‐MREr‐based stiffness values were investigated. SMS‐MREr reduced the scan time by half relative to MREr, and allowed acquisition of four‐slice MRE data in a single 17‐second breath‐hold. Visual comparison suggested agreement between MREr and SMS‐MREr elastograms. A Pearson's correlation of 0.93 was observed between stiffness values derived from MREr and SMS‐MREr. Bland–Altman analysis demonstrated good agreement, with −0.08 kPa mean bias and narrow limits of agreement (95% CI: 0.23 to −0.39 kPa) between stiffness values obtained using MREr and SMS‐MREr. SMS can be combined with other fast MRE approaches to achieve further acceleration. This pushes the limit on the acceleration that can be achieved in MRE acquisition, and makes it possible to conduct liver MRE exams in a single breath‐hold.