Significant Differences In Stiffness Research Articles

Does Sagittal Alignment Matter? A Biomechanical Look at Pinning Pediatric Supracondylar Humerus Fractures.

Closed manipulation and percutaneous pinning is standard of care for displaced supracondylar humerus fractures, yet the optimal pin configuration, particularly in the sagittal plane, is not well defined. This study evaluates how sagittal plane pin variations affect construct strength biomechanically. One hundred synthetic pediatric humerus models were used to emulate supracondylar humerus fracture. The models were pinned using 4 different configurations uniformly divergent in the coronal plane with variations in the sagittal plane: (1) 2 diverging pins with the lateral pin anterior (n = 25), (2) 2 diverging pins with the lateral pin posterior (n = 25), (3) 2 parallel pins (n = 25), and (4) 3 parallel pins (n = 25). The models were tested under bending (flexion, extension, and varus) and rotational (internal and external) forces, measuring stiffness and torque. Statistical analyses identified significant differences across configurations. The 2-pin parallel configuration (9.68N/mm in extension, 8.76N/mm in flexion, 0.14 N-m/deg in internal rotation, and 0.14 N-m/deg in external rotation) performed similarly to the 3-pin parallel setup (10.77N/mm in extension, 7.78N/mm in flexion, 0.16 N-m/deg in internal rotation, and 0.14 N-m/deg in external rotation), with no significant differences in stiffness. In contrast, both parallel configurations significantly outperformed the 2-pin anterior (5.22N/mm in extension, 5.7N/mm in flexion, 0.11 N-m/deg in internal rotation and 0.10 N-m/deg in external rotation) and posterior (9.86N/mm in extension, 8.31N/mm in flexion, 0.12N-m/deg in internal rotation, and 0.11 N-m/deg in external rotation) configurations in resisting deformation. No notable disparities were observed in varus loading among any configurations. This study illuminates the sagittal plane's role in construct stability. It suggests that, when utilizing 2-pins, parallel configurations in the sagittal plane improve biomechanical stability. In addition, it suggests avoiding the lateral anterior pin configuration due to its biomechanical inferiority. Further research should assess ultimate strength and compare various 3-pin configurations to better delineate differences between 2-pin and 3-pin configurations regarding sagittal plane alignment. Level III-biomechanical study.

Native anterior talo-fibular ligament tensile characteristics compared to allograft, suture tape, and copolymer augmentation elements: A biomechanical study

Surgical augmentation methods have been introduced to the Modified Broström (MB) technique to support native anterior talo-fibular ligament (ATFL) healing and function. This study aimed to investigate the isolated biomechanical performance of common MB augmentation elements, including allograft, suture tape, and copolymer, compared to native ATFL.Six cadaveric feet were dissected, isolating the ATFL from all surrounding soft tissue. The fibula and talus were clamped on the testing frame so that the ligament was in line with the load cell. Six samples per augment group were fixed on a test frame with a gauge length of 20 mm to replicate ATFL length. All samples were pulled to failure at 305 mm/min. Biomechanical outcomes included stiffness, elongation, and ultimate load.Mean ± standard deviation was reported. Stiffness was highest for suture tape (246.4 ± 52.1N/mm), followed by allograft (114.2 ± 26.2 N/mm), native ATFL (78.6 ± 31.8 N/mm), and copolymer (9.4 ± 2.9 N/mm). Significant differences in stiffness were observed between all groups except when comparing ATFL stiffness to allograft (P = 0.086). Copolymer resulted in significantly larger elongation at ultimate load compared to native ATFL, suture tape, and allograft (P < 0.001). Elongation at ultimate failure was highest for copolymer (30.0 ± 8.7 mm) and significantly greater than all other groups (P < 0.001). Ultimate load was highest for suture tape (544.1 ± 59.7 N), followed by native ATFL (338.5 ± 63.7 N), allograft (308.3 ± 98.5 N) and copolymer (146.7 ± 8.9 N). Suture tape ultimate load was significantly greater than copolymer (P < 0.001).Isolated biomechanical data of augment materials can be utilized by foot and ankle surgeons when considering appropriate ligament augmentation options.Level of clinical evidence 5, controlled laboratory study

Transverse seismic analysis method of underground interchange prefabricated utility tunnel

The rapid development of underground utility tunnels has led to the formation of a large number of interchange utility tunnels. Due to significant differences in the lateral resisting stiffness in orthogonal directions, coupled with the close relationship between soil deformation and the depth of the utility tunnel, the seismic response mechanism of the interchange utility tunnel is complex. This paper proposes a method for transverse seismic analysis of the underground interchange utility tunnel based on the response displacement method. A load-structure analysis model of a certain underground cross-type interchange utility tunnel is first established. Then, the different conditions corresponding to maximum relative deformation between layers of the interchange node are discussed, and the proposed method is validated via the time-history analysis method. Based on the proposed analysis method in this paper, seismic response analysis is performed on the interchange utility tunnel considering the condition of vertical incidence of three different input seismic waves. Discussions are conducted in terms of internal forces, inter-story displacement angles, and damage responses under seismic excitations in different principal axis directions. The results show that under major earthquakes, the maximum inter-story displacement angle of the interchange node exceeds the standard limit by up to approximately 184 %, while the tensile damage can reach up to 0.985, significantly surpassing the tensile damage limit. Accordingly, the interchange node is the weakest part of the interchange utility tunnel. There exists deformation inconsistency between the interchange node and standard segments due to significant stiffness differences, with the influence range of the interchange node on internal forces, inter-story displacement angles, joint deformations and damage of the utility tunnel is approximately 7, 6, 8, and 6 prefabricated standard segments, respectively. Since the maximum relative deformation between layers of the interchange node does not occur simultaneously, for double-layered and multi-layered interchange utility tunnels, it is necessary to comprehensively consider the maximum inter-story displacement angle between each layer to determine their most unfavorable condition. The analytical method and related research conclusions presented in this paper can provide references for the transverse seismic design of interchange utility tunnels.

Shear Wave Elastography of the Skin following Radial Forearm Free Flap Surgery in Transgender Patients: Observational Study.

Background: Ultrasound shear wave elastography (SWE) noninvasively measures the stiffness of tissue by producing and measuring tissue deformation. Scar formation, a crucial aspect of wound healing, can lead to functional and aesthetic complications when pathological. While SWE has shown promise in dermatological evaluations, its role in surgical scar assessment remains underestimated. Our study aims to investigate SWE in evaluating surgical scars at the donor site after forearm free flap surgery in transgender patients. Methods: After radial forearm free flap harvesting, the donor site was grafted with a split-thickness skin graft with or without interposition of Matriderm. Eleven patients were evaluated more than one year after surgery, using SWE alongside scar characteristics, sensory outcomes, and patient satisfaction surveys. Results: Our study revealed no significant difference in stiffness (p > 0.15), pigmentation (p = 0.32), or erythema (p = 0.06) between operated and non-operated sides. The interposition of Matriderm did not influence the stiffness. Patients significantly (p < 0.0001) reported a loss of discrimination. Patients' subjective scar evaluation appeared in line with our quantitative and objective results. Conclusions: This study contributes to the evolving understanding of SWE's role in scar assessment, highlighting its feasibility in evaluating surgical scars. However, continued research efforts are necessary to establish SWE as a reliable and objective method for surgical scar evaluation and management.

Biomechanical analysis of four different meniscus suturing techniques for posterior meniscal root pull-out repair: A human cadaveric study.

Tocompare the biomechanical properties of the slip-knot technique with three other transtibial pullout suture repair constructs for meniscal root tears. Thirty-two fresh-frozen cadaveric menisci were randomly allocated to four meniscus-suture fixation constructs: Two simple-sutures (TSS), two slip-knot (TSK) sutures, two cinch-loop (TCL) sutures, and two modified Mason-Allen (TMMA) sutures. Cyclic loading from 5 to 20 N was conducted for 1000 cycles at 0.5 Hz, and then loaded to failure at 0.5 mm/s. Parametric data (displacement during cyclic loading, ultimate load, yield load, and displacement at failure) were analysed using a one-way analysis of variance (ANOVA), whereas nonparametric data (stiffness) were analysed using the Kruskal-Wallis test. After 1000 cycles, the TCL construct significantly displaced the most (mean ± SD, 6.78 ± 1.32 mm; p < 0.001), followed by the TMMA (2.83 ± 0.90 mm), TSK (2.33 ± 0.57 mm), and TSS (2.03 ± 0.62 mm) groups. On ultimate failure load, there was no significant difference between the TSK group (123.48 ± 27.24 N, p > 0.05) and the other three groups (TSS, 94.65 ± 25.33 N; TMMA, 168.38 ± 23.24 N; TCL, 170.54 ± 57.32 N); however, it exhibited the least displacement (5.53 ± 1.25 mm) which was significantly shorter than those of the TCL (11.82 ± 4.25 mm, p < 0.001) and TMMA (9.53 ± 2.18 mm, p = 0.03) constructs. No significant difference in stiffness was observed among the four meniscus-suture constructs. The slip-knot technique has proven to be a simple, yet robust and stable meniscal root fixation option; moreover, it exhibited superiority over the more complex modified Mason-Allen suture construct in resisting displacement at the ultimate failure load. Not applicable.

Tissue-Specific Quantification of Radiation-Induced Cervical Fibrosis and Correlation with Cervical Range of Motion.

Cervical fibrosis (CF) as a late consequence in patients after radiotherapy significantly impacts the long-term symptoms, functionality, and quality of life of these cancer patients due to a hardening process of different histological tissues. Modern Shear Wave Ultrasound Elastography now enables a differentiated analysis of the changes in various tissue types. In this study, tissue-specific changes in CF induced by radiation therapy in head and neck (ENT) cancer patients were quantified and correlated with cervical range of motion (CROM). 16 patients after radiation of the cervical lymphatic drainage were selected as the observation group (OG). Further, 16 people without radiation in the head and neck region were matched by gender, age, and BMI as the control group (CG). Stiffness measurements in kilopascal (kPa; 1 Pa = 1 N m-2) were performed using shear wave elastography (SWE) to assess the elasticity of muscle, fascia, and subcutaneous tissue within and surrounding the sternocleidomastoid muscle (SCM). Specific parameters of the OG were compared to the CG and correlated with functional parameters and quality of life (QoL). The OG exhibited significantly higher stiffness values (Emean, Emax, Emin) across all tissue types than the CG, suggesting a tangible effect of radiation therapy on tissue stiffness. Muscle compartment analysis revealed the most significant stiffness differences. Thickness measurements indicated changes in the muscle and skin but not in the subcutaneous tissue. CROM measurements within the OG fell within normal ranges, suggesting a possible homogenizing effect of radiation treatment on CROM variability. Strong correlations were observed between age and specific stiffness measures, particularly in the OG group, indicating a broader impact of aging or radiation therapy on physiological measures. Significant correlations between tissue stiffness and CROM were found. CF after radiotherapy occurs primarily in the muscle tissue and its fascia, with the hardening being about twice as pronounced as in the average population and becoming more pronounced with increasing age and correlates with CROM.

Collagen fibers within skeletal muscle extracellular matrix dynamically change their alignment in a stretch-dependent fashion

Collagen fiber architecture within the skeletal muscle extracellular matrix (ECM) contributes to muscle passive mechanical properties. There is evidence that collagen fibers change their alignment during muscle lengthening (stretching). Thus, the goal of this study was to characterize the dynamic changes of collagen fiber alignment in the muscle ECM during muscle stretching, and to assess the relationship between dynamic collagen re-alignment and muscle passive mechanics. We hypothesized that collagen fibers increase their alignment as the muscle is stretched, and that increased collagen alignment in stretched muscle is correlated to higher elastic stiffness. Extensor digitorum longus (EDL), soleus, and diaphragm muscles were collected from wildtype (WT) and D2.mdx (MDX) mice of 48-52 weeks of age. Muscles underwent a series of twitches to determine the optimum length (Lo) for isometric contraction, and then were decellularized to isolate the muscle ECM. Decellularized muscles (DCMs) were then mechanically tested using a series of stress-relaxation tests at 5% increments from 85% to 115% length relative to Lo. Elastic stiffness was measured as the slope of the tangent line on the stress-strain curve following stress-relaxation. Following mechanical testing, DCMs were imaged using second harmonic generation microscopy to visualize collagen alignment across the range of lengths used in mechanical testing. Collagen alignment was reported as an alignment index on a scale of 0 (perfect unalignment) to 1 (perfect alignment). We found that MDX diaphragm DCMs were less stiff than WT (WT: 910.2±586.7, MDX: 238±168.7, p=0.0041), but there were no significant differences in stiffness between WT and MDX EDL and soleus DCMs. We also observed a significant effect of stretch on collagen alignment in all DCMs tested (Diaphragm: p=0.0071, EDL: p=0.0004, soleus: p&lt;0.0001). Interestingly, the collagen fibers of the epimysium, the outermost layer of the muscle ECM, were more aligned in WT diaphragm DCMs than in MDX (WT 85%: 0.672±.14, MDX 85%: 0.344±0.16, p=0.0027; WT 115%: 0.783±0.04, MDX 115%: 0.480±0.19, p=0.0036). Finally, we found a significant positive correlation between the alignment and elastic stiffness at 110% Lo across all DCMs (p=0.0038, R2=0.1713). These data indicate that collagen fibers dynamically re-align as muscle is stretched. Additionally, increased collagen fiber alignment is associated with higher passive stiffness in the decellularized muscle ECM. Overall, we find that dynamic architectural changes in the muscle ECM contribute to passive mechanical behavior during a muscle stretch. This work was supported by a grant from the NIH NIAMS (R01-AR079545). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Regional variations and sex-related differences of stiffness in human tracheal ligaments.

There have been numerous studies focused on the stiffness of tracheal cartilage. However, no research has been conducted specifically on the annular ligament, nor have any regional differences in the annular ligament been identified. The purpose of this study was to investigate the stiffness of the ligaments present between the thyroid, cricoid and tracheal cartilages. The ligaments were identified in the cervical region of living subjects with ultrasonography. The stiffness of the ligaments was measured from the body surface using a digital palpation device (MyotonPRO). Since it is impossible to measure the entire trachea in a living subject, an additional measurement was performed on human cadavers. Both in vivo and cadaveric investigations found that the stiffness of annular ligaments decreased gradually from the superior to inferior parts. There was no difference in the stiffness between males and females in the superior part of the trachea. However, the stiffness of the middle and inferior parts was predominantly higher in females than in males. Furthermore, males showed significant differences in stiffness between the superior and middle parts, while females showed no significant differences. These results reveal that there are regional and sex-related differences in the stiffness of human tracheal ligaments.

Quantifying Plantar Flexor Muscles Stiffness During Passive and Active Force Generation Using Shear Wave Elastography in Individuals With Chronic Stroke

ObjectivesThis study aims to investigate the mechanical properties of paretic and healthy plantar flexor muscles and assesses the spatial distribution of stiffness between the gastrocnemius medialis (GM) and lateralis (GL) during active force generation. MethodsShear wave elastography measurements were conducted on a control group (CNT, n=14; age= 59.9 ± 10.6 years; BMI= 24.5 ± 2.5 kg/m2) and a stroke survivor group (SSG, n = 14; age = 63.2 ± 9.6 years; BMI = 23.2 ± 2.8 kg/m2). Shear modulus within the GM and GL was obtained during passive ankle mobilization at various angles of dorsiflexion (P0= 0°; P1= 10°; P2= 20°; P3= -20° and P4= -30°) and during different levels of maximal voluntary contraction (MVC) (100%, 30%, 50%, 70%). Muscle activation of GM, GL, and tibialis anterior was also evaluated. ResultsThe results revealed a significant increase in passive stiffness within the paretic plantar flexor muscles under high tension during passive mobilization (p<0.05). Yet, during submaximal and maximal MVC, the paretic plantar flexors exhibited decreased active stiffness levels (p<0.05). A notable discrepancy was found between the stiffness of the GM and GL muscles, with the GM demonstrating greater stiffness from 0° of dorsiflexion in the SSG (p<0.05), and from 10° of dorsiflexion in the CNT (p<0.05). No significant difference in stiffness was observed between the GM and GL muscles during active conditions. ConclusionStroke affects the mechanical properties differently depending on the state of muscle activation. Notably, the distribution of stiffness among synergistic plantar flexor muscles varied in passive condition, while remaining consistent in active condition.

Is just one screw really enough? Single- versus double-screw in the medial malleolus in supination-external rotation ankle fractures: A comparative biomechanical study using partially threaded cancellous screws

ObjectiveThe aim of this study is to investigate stiffness and the maximum load to failure values of single- and double-screw fixation of oblique medial malleolus fractures using partially threaded cancellous screws. Our hypothesis is that single-screw fixation of medial malleolus fractures after SER injuries provides similar stiffness when compared with double-screw fixation. DesignBiomechanical study. MethodsTwelve composite polyurethane synthetic right distal tibiae were used in the experiment. Oblique fractures of the medial malleolus were created with a band saw using a custom-made osteotomy guide to standardize the cuts in all models. Bone models were randomly separated into two groups and fixed with one (n = 6) or two (n = 6) 4.0 mm partially threaded cancellous screws placed perpendicular to the fracture line. These were tested by applying an offset axial tension at 10 mm/minute up to maximum load displacement, defined as subsidence of the medial malleolus fragment. Maximum load to failure was determined for the groups at the point where the curve ceased to be linear and suffered an inflection. Force versus displacement curves were obtained and recorded. The student's t-test for independent samples was used to compare stiffness (N / mm) and maximum load (N) between experimental groups, with a p value of < 0.05. ResultsThere were no significant differences in stiffness (p = 0.290) and maximum load (p = 0.191) among the two fixation constructs. Mean stiffness was 62.26 (±SD 21.11) N/mm for double-screw fixation group and 48.24 (±SD 22.40) N/mm for single-screw fixation group. Mean maximum load was 387.83 (±SD 115.78) N for double-screw fixation group and 306.64 (±SD 81.97) N for single-screw fixation group. ConclusionFixation with one 4.0 mm partially threaded cancellous screw was not shown to be biomechanically inferior to fixation with two 4.0 mm partially threaded cancellous screws in an oblique fracture of the medial malleolus, supporting previous clinical studies that have shown that one screw is sufficient for fractures of the medial malleolus.

Dynamic Quantitative Imaging of the Masseter Muscles in Bruxism Patients with Myofascial Pain: Could It Be an Objective Biomarker?

We aimed to investigate whether the collaboration of shear wave elastosonography (SWE) and B-mode ultrasonography (US) could be offered as diagnostic tools to assess the presence, severity, and progress of bruxism, as well as a biomarker for the effectiveness of treatment in daily clinical practice. The study was designed as a quantitative evaluation of the masseter muscles (MMs) of the clinically diagnosed bruxism patients suffering from myofascial pain and MMs of the healthy individuals. Clinical examinations were made according to the diagnostic criteria for temporomandibular disorders (DC/TMD), and pain was assessed using a visual analog scale (VAS). Painful MMs with VAS scores ≥ 4 were assigned to Group A, and healthy MMs were assigned to Group B. Also, the MMs of the painful bruxers were analyzed based on wearing occlusal splints. Group A was divided into two subgroups as splint users (Group AI) and non-users (Group AII). All the participants were scanned with dynamic US and SWE to quantify the size and stiffness of the MMs. Measurements of each muscle pair while the jaw is in a resting position (relaxation) and clenching position (contraction) were recorded. The significant differences in stiffness and thickness became visible in the relaxation state. Bruxism patients with myofascial pain had significantly harder and thinner MMs than healthy individuals. During the relaxation, the mean thickness and elasticity values were 9.17 ± 0.40 mm and 39.13 ± 4.52 kPa for Group A and 10.38 ± 0.27 and 27.73 ± 1.92 for Group B, respectively. Also, stiffer MMs were measured in Group AII (38.16 ± 3.61 kPa) than in Group AI (26.91 ± 2.13 kPa). In conclusion, the combination of SWE and US using a dynamic examination technique has the potential to be a valuable tool for the management of bruxism patients suffering from myofascial pain.

Biomechanical Comparison of 3 Adjustable-Loop Suspensory Devices for All-Inside ACL Reconstruction: A Time-Zero Full-Construct Model.

Little is known about the stability of adjustable-loop devices (ALDs) for anterior cruciate ligament (ACL) reconstruction (ACLR). To evaluate the stabilization behavior of 3 different types of ALDs for all-inside ACLR in a full-construct surgical technique-based manner. Controlled laboratory study. The femoral and tibial devices of Ultrabutton (Smith & Nephew), Infinity (Conmed), and TightRope II (Arthrex) were applied to quadrupled bovine tendon grafts (n = 8 each) with tibial-sided traction applied (350 N) for graft tensioning in a simulated fully extended knee. Knotless femoral graft fixation was based on either a suture-locking device (SLD; Ultrabutton), button-locking device (BLD; Infinity), or dual-locking device (DLD; TightRope II). All constructs were progressively loaded (50 N/500 cycles) from 50 to 300 N for 3000 cycles (0.75 Hz), including complete unloading situations and pull to failure (50 mm/min). Construct elongation, stiffness, and ultimate load were analyzed. BLD showed significantly greater initial elongation (-2.69 ± 0.15 mm) than DLD (-3.19 ± 0.21 mm; P < .001) but behaved similarly to SLD (-2.93 ± 0.23 mm). While DLD and SLD had the smallest initial elongation at the same significance level, they behaved opposite to each other with gradually increasing peak loading. At the end of testing, DLD had the lowest (-0.64 ± 0.32 mm) and SLD the highest (3.41 ± 1.01 mm) total elongation (P < .003 for both). SLD displayed significantly higher dynamic elongation (6.34 ± 0.23 mm) than BLD (3.21 ± 0.61 mm) and DLD (2.56 ± 0.31 mm) (P < .001 for both). The failure load of BLD (865.0 ± 183.8 N) was significantly lower (P < .026) compared with SLD and DLD (>1000 N). The predominant failure mode was suture rupture and tibial bone breakage with button subsidence (SLD, n = 4). No significant difference in stiffness between constructs was found. While DLD successfully restricted critical construct elongation, BLD partially and SLD completely exceeded the clinical failure threshold (>3 mm) of plastic elongation with loop lengthening during increasing cyclic peak loading with complete unloading. Higher failure loads of SLD and DLD implants (>1000 N) were achieved at similar construct stiffness to BLD. A detailed biomechanical understanding of the stabilization potential is pertinent to the continued evolution of ALDs to improve clinical outcomes.

Biomechanical characteristics of a new looping stitch versus the classic Krackow stitch for distal biceps fixation

The purpose of this study was to quantify the biomechanical characteristics of a new looping stitch, developed with the concepts of a looping, locking stitch that decreases needle penetrations of the tendon, and compare it to a classic Krackow stitch for distal biceps suture-tendon fixation. The Krackow stitch with No. 2 braided suture and the looping stitch with a No. 2 braided suture loop attached to a 25-mm-length by 1.3-mm-width polyblend suture tape were compared. The Looping stitch was performed with single strand locking loops and wrapping suture around the tendon, resulting in half the needle penetrations through the graft compared to the Krackow stitch. Ten matched pairs of human distal biceps tendons were used. One side of each pair was randomly assigned to either the Krackow or the looping stitch, and the contralateral side was used for the other stitch. For biomechanical testing, each construct was preloaded to 5 N for 60 seconds, followed by cyclic loading to 20 N, 40 N, and 60 N for 10 cycles each, and then loaded to failure. The deformation of the suture-tendon construct, stiffness, yield load, and ultimate load were quantified. Comparisons between the Krackow and looping stitches were performed with a paired t-test using P<.05 as statistically significant. The Krackow stitch and looping stitch had no significant difference in stiffness, peak deformation, or nonrecoverable deformation after 10 cycles of loading to 20 N, 40 N, and 60 N. There was no difference between the Krackow stitch and looping stitch in load applied to displacement of 1 mm, 2 mm, and 3 mm. The ultimate load showed that the looping stitch was significantly stronger compared to the Krackow stitch (Krackow stitch: 223.7±50.3 N; looping stitch: 312.7±53.8 N) (P=.002). The failure modes were either suture breakage or tendon cut through. For the Krakow stitch, there was 1 suture breakage and 9 tendons cut through. For the looping stitch, there were five suture breakages, and five tendons cut through. With fewer needle penetrations, incorporation of 100% of the tendon diameter, and a higher ultimate load to failure compared to the Krackow stitch, the Looping stitch may be a viable option to reduce deformation, failure, and cut-out of the suture-tendon construct.

Biomechanical analysis of plating techniques for unstable lateral clavicle fractures with coracoclavicular ligament disruption (Neer typeIIB).

Neer type IIB lateral clavicle fractures are inherently unstable fractures with associated disruption of the coracoclavicular (CC) ligaments. Because of the high rate of nonunion and malunion, surgical fixation is recommended; however, no consensus has been reached regarding the optimal fixation method. A newplating technique using a superior lateral locking plate with anteroposterior (AP) locking screws, resulting in orthogonal fixation in the lateral fragment, has been designed to enhance stability and reduce implant failure. The purpose of this study was to biomechanically compare 3 different clavicle plating constructs within a fresh frozen human cadaveric shoulder model. Twenty-four fresh frozen cadaveric shoulders were randomized into 3 groups (n=8 specimens): group 1, lateral locking plate only (Medartis Aptus Superior Lateral Plate); group 2, lateral locking plate with CC stabilization (No. 2 FiberWire); and group 3, lateral locking plate with 2 AP locking screws stabilizing the lateral fragment. All specimens were subject to cyclic loading of 70 N for 500 cycles. Data were analyzed for gap formation after cyclic loading, construct stiffness, and ultimate load to failure, defined by a marked decrease in the load displacement curve. After 500 cycles, there was no statistically significant difference between the 3 groups in gap formation (P=.179). No specimen (0/24) failed during cyclic loading. Ultimate load to failure was significantly higher in group 3 compared to group 1 (286 N vs. 167 N; P=.022), but not to group 2 (286 N vs. 246 N; P=.604). There were no statistically significant differences in stiffness (group 1: 504 N/mm; group 2: 564 N/mm; group 3: 512 N/mm; P=.712). Peri-implant fracture was the primary mode of failure for all 3 groups, with group 3 demonstrating the lowest rate of peri-implant fractures (group 1: 6/8; group 2: 7/8; group 3: 4/8; P=.243). Biomechanical evaluation of the clavicle plating techniques showed effective fixation across all specimens at 500 cycles. The lateral locking plate with orthogonal AP locking screw fixation in the lateral fragment demonstrated the greatest ultimate failure load, followed by the lateral locking plate with CC stabilization. This new plating technique showed compatible stiffness and gap formation when compared to conventional lateral locking plates as well as plates with CC fixation. The use of orthogonal screw fixation in the distal fragment may negate against the need for CC stabilization in these types of fractures, thus minimizing surgical dissection around the coracoid and potential complications.

BIOMECHANICAL ANALYSIS OF PLATING TECHNIQUES FOR UNSTABLE LATERAL CLAVICLE FRACTURES WITH CORACOCLAVICULAR LIGAMENT DISTRUPTION (NEER TYPE-IIB)

Neer Type-IIB lateral clavicle fractures are inherently unstable fractures with associated disruption of the coracoclavicular (CC) ligaments. A novel plating technique using a superior lateral locking plate with antero-posterior (AP) locking screws, resulting in orthogonal fixation in the lateral fragment has been designed to enhance stability. The purpose of this study was to biomechanically compare three different clavicle plating constructs.24 fresh-frozen cadaveric shoulders were randomised into three groups (n=8 specimens). Group 1: lateral locking plate only (Medartis Aptus Superior Lateral Plate); Group 2: lateral locking plate with CC stabilisation (Nr. 2 FiberWire); and Group 3: lateral locking plate with two AP locking screws stabilising the lateral fragment. Data was analysed for gap formation after cyclic loading, construct stiffness and ultimate load to failure, defined by a marked decrease in the load displacement curve.After 500 cycles, there was no statistically significant difference between the three groups in gap-formation (p = 0.179). Ultimate load to failure was significantly higher in Group 3 compared to Group 1 (286N vs. 167N; p = 0.022), but not to Group 2 (286N vs. 246N; p = 0.604). There were no statistically significant differences in stiffness (Group 1: 504N/mm; Group 2: 564N/mm; Group 3: 512N/mm; p = 0.712). Peri-implant fracture was the primary mode of failure for all three groups, with Group 3 demonstrating the lowest rate of peri-implant fractures (Group 1: 6/8; Group 2: 7/8, Group 3: 4/8; p = 0.243).The lateral locking plate with orthogonal AP locking screw fixation in the lateral fragment demonstrated the greatest ultimate failure load, followed by the lateral locking plate with CC stabilization. The use of orthogonal screw fixation in the distal fragment may negate against the need for CC stabilization in these types of fractures, thus minimizing surgical dissection around the coracoid and potential complications.

Morphological and mechanical alterations in articular cartilage and subchondral bone during spontaneous hip osteoarthritis in guinea pigs.

Objectives: This study aimed to investigate the morphological and mechanical changes in articular cartilage and subchondral bone during spontaneous hip osteoarthritis in guinea pigs. Materials and methods: Hip joints of guinea pigs were investigated at 1, 3, 6, and 9 months of age (hereafter denoted as 1M, 3M, 6M, and 9M, respectively; n = 7 in each group). Morphological and mechanical alterations during spontaneous hip osteoarthritis in guinea pigs were investigated. The alterations included the micromechanical properties of articular cartilage (stiffness and creep deformation), microstructure of the subchondral bone (bone mineral density, bone volume fraction, trabecular thickness, trabecular number, and trabecular separation), micromorphology of the articular cartilage, and surface nanostructure (grain size and roughness) of the articular cartilage and subchondral bone. Results: Micromechanical properties of articular cartilage in 1M showed the lowest stiffness and highest creep deformation with no significant differences in stiffness or creep deformation amongst 3M, 6M, and 9M. Articular cartilage thickness decreased with age. The earliest degeneration of articular cartilage occurred at 6 months of age, characterised by surface unevenness and evident chondrocytes reduction in micromorphology, as well as increased grain size and decreased roughness in nanostructure. No degeneration at micro- or nanostructure of subchondral bone was observed before 9 months. Conclusion: Morphological degeneration of cartilage occurred before degeneration of mechanical properties. Meanwhile, degeneration of cartilage occurred before degeneration of subchondral bone during hip osteoarthritis. The current study provided novel insights into the structural and micromechanical interaction of hip osteoarthritis, which can serve as a theoretical basis for understanding the formation and progression of osteoarthritis.

Prophylactic Femoral Neck Fixation in an Osteoporosis Femur Model: A Novel Surgical Technique with Biomechanical Study.

Intramedullary nailing (IMN) is a popular treatment for elderly patients with femoral shaft fractures. Recently, prophylactic neck fixation has been increasingly used to prevent proximal femoral fractures during IMN. Therefore, this study aimed to investigate the biomechanical strength of prophylactic neck fixation in osteoporotic femoral fractures. An osteoporotic femur model was created to simulate the union of femoral shaft fractures with IMN. Two study groups comprising six specimens each were created for IMN with two standard proximal locking screws (SN group) and IMN with two reconstruction proximal locking screws (RN group). Axial loading was conducted to measure the stiffness, load-to-failure, and failure modes. There were no statistically significant differences in stiffness between the two groups. However, the load-to-failure in the RN group was significantly higher than that in the SN group (p < 0.05). Femoral neck fractures occurred in all specimens in the SN group. Five constructs in the RN group showed subtrochanteric fractures without femoral neck fractures. However, one construct was observed in both subtrochanteric and femoral neck fractures. Therefore, prophylactic neck fixation may be considered an alternative biomechanical solution to prevent proximal femoral fractures when performing IMN for osteoporotic femoral fractures.

Differential effect of dementia etiology on cortical stiffness as assessed by MR elastography

BackgroundAging and dementia involve the disruption of brain molecular pathways leading to the alterations in tissue composition and gross morphology of the brain. Phenotypic and biomarker overlap between various etiologies of dementia supports a need for new modes of information to more accurately distinguish these disorders. Brain mechanical properties, which can be measured noninvasively by MR elastography, represent one understudied feature that are sensitive to neurodegenerative processes. In this study, we used two stiffness estimation schemes to test the hypothesis that different etiologies of dementia are associated with unique patterns of mechanical alterations across the cerebral cortex. MethodsMR elastography data were acquired for six clinical groups including amyloid-negative cognitively unimpaired (CU), amyloid-positive cognitively unimpaired (A + CU), amyloid-positive participants with mild cognitive impairment (A + MCI), amyloid-positive participants with Alzheimer’s clinical syndrome (A + ACS), dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD). Stiffness maps were computed using two neural network inversions with the objective to at least partially separate the parenchyma-specific and morphological effects of neurodegeneration on mechanical property estimates. A tissue-confined inversion algorithm was designed to obtain the best estimate of stiffness in the brain parenchyma itself, while a regionally-aware inversion algorithm was used to measure the tissue stiffness along with the surroundings. Mean stiffness of 15 bilateral gray matter cortical regions were considered for statistical analysis. First, we tested the hypothesis that cortical stiffness changes in the aging brain. Next, we tested the overall study hypothesis by first comparing stiffness in each clinical group to the CU group, and then comparing the clinical groups against one another. Finally, we assessed the spatial and statistical overlap between atrophy and stiffness changes for both inversions. ResultsCortical brain regions become softer with age for both inversions with larger effects observed using regionally-aware stiffness. Stiffness decreases in the range 0.010–0.027 kPa per year were observed. Pairwise comparisons of each clinical group with cognitively unimpaired participants demonstrated 5 statistically significant differences in stiffness for tissue-confined measurements and 19 statistically different stiffness changes for the regionally-aware stiffness measurements. Pairwise comparisons between clinical groups further demonstrated unique patterns of stiffness differences. Analysis of the atrophy-versus-stiffness relationship showed that regionally-aware stiffness measurements exhibit higher sensitivity to neurodegeneration with findings that are not fully explained by partial volume effects or atrophy. ConclusionsBoth tissue-confined and regionally-aware stiffness estimates exhibited unique and complementary stiffness differences in various etiologies of dementia. Our results suggest that mechanical alterations measured by MRE reflect both tissue-specific differences as well as environmental effects. Multi-inversion schemes in MRE may provide new insights into the relationships between neuropathology and brain biomechanics.

Biomechanical comparison of pedicle screw fixation strength among three different screw trajectories using single vertebrae and one-level functional spinal unit.

Three key factors are responsible for the biomechanical performance of pedicle screw fixation: screw mechanical characteristics, bone quality and insertion techniques. To the best of the authors' knowledge, no study has directly compared the biomechanical performance among three trajectories, i.e., the traditional trajectory (TT), modified trajectory (MT) and cortical bone trajectory (CBT), in a porcine model. This study compared the pullout strength and insertion torque of three trajectory methods in single vertebrae, the pullout strength and fixation stiffness including flexion, extension, and lateral bending in a one-level instrumented functional spinal unit (FSU) that mimics the in vivo configuration were clarified. A total of 18 single vertebrae and 18 FSUs were randomly assigned into three screw insertion methods (n = 6 in each trajectory group). In the TT group, the screw converged from its entry point, passed completely inside the pedicle, was parallel to the superior endplate, was located in the superior third of the vertebral body and reached to at least the anterior third of the vertebral body. In the MT group, the convergent angle was similar to that of the TT method but directed caudally to the anterior inferior margin of the vertebral body. The results of insertion torque and pullout strength in single vertebrae were analyzed; in addition, the stiffness and pullout strength in the one-level FSU were also investigated. This study demonstrated that, in single vertebrae, the insertion torque was significantly higher in CBT groups than in TT and MT groups (p < 0.05). The maximal pullout strength was significantly higher in MT groups than in TT and CBT groups (p < 0.05). There was no significant difference in stiffness in the three motions among all groups. The maximal pullout strength in FSUs of MT and CBT groups were significantly higher than the TT groups (p < 0.05). We concluded that either MT or CBT provides better biomechanical performance than TT in single vertebrae or FSUs. The lack of significance of stiffness in FSUs among three methods suggested that MT or CBT could be a reasonable alternative to TT if the traditional trajectory was not feasible.

Investigation on the effect of cotton-tencel (50:50) siro yarn twist multipliers on fabric stiffness

The properties of fabrics are mainly affected by constituent fiber properties and yarn structures. The yarn structures are primarily dependent on the spinning technique. The twist multiplier is a leading factor influencing yarn structure which directly correlates with fabric stiffness and mechanical properties due to structural behavior. In this study, siro spun yarn has been prepared using different twist multipliers (3.6, 4, 4.4, and 5.0) by blending cotton and tencel fiber at the spinning stage to investigate the effect of twist multipliers on fabric stiffness and the flexural rigidity of woven fabrics. The 1/1 plain, 2/2 twill, and 8-end satin fabrics have been woven using prepared yarns in warp and weft directions. The fabric stiffness has been measured using the ASTM D1388-2018 method. The results reveal that fabric stiffness increased with the increasing twist multiplier. Furthermore, a comparative study on different weave structures shows significant differences in stiffness. Overall, the experimental results present a close relationship between twist multiplier, spinning triangle, float length, fabric stiffness, and rigidity, and also show the optimum twist level for cotton-tencel siro yarn to attain maximum stiffness and strength.