Acute Effects of Local High-Frequency Percussive Massage on Deep Fascial and Muscular Stiffness and Joint Range of Motion in Young Adult Men.

BACKGROUND: Local high-frequency percussive (HFP) massage has recently found widespread application in physical therapy. Although HFP massage reportedly improves range of motion (ROM), the mechanism underlying its action has not yet been proven. This study aimed to clarify whether a 5-minute percussive massage regimen affects muscular or connective tissues, such as the deep fascia and deep intermuscular fascia and the change in joint ROM. METHOD: The study sample was calculated using G*Power analysis program, and this study enrolled 15 healthy men who underwent 5-minute HFP massage to the medial gastrocnemius muscle. Shear-wave elastography was used to measure tissue stiffness in the deep fascia, muscle, and deep intermuscular fascia through shear-wave velocity as well as the ROM of the volunteers' ankle joint dorsiflexion before and after the HFP massage. A value of P < .05 was used to declare statistical significance, and post hoc was used to calculate the effect size using G*Power. RESULTS: Shear-wave velocity revealed a significant change in the deep fascia (P = .003; shear-wave velocity: -0.7 m/s) and significant increase in ROM of ankle dorsiflexion (P = .002; increase in ROM: 3.0°) after 5 minutes of HFP massage. However, the muscle and deep intermuscular fascia did not exhibit any significant changes. CONCLUSIONS: HFP massage for 5 minutes modified the stiffness of the deep fascia and concurrently improved the ankle joint-dorsiflexion ROM. This method can be used as an intervention to decrease stiffness of the deep fascia and increase the ROM efficiently.

Morphological and mechanical characteristics of the intrinsic and extrinsic foot muscles under loading in individuals with flat feet.

BACKGROUND: The intrinsic and extrinsic foot softtissue structures that apply force and support the medial longitudinal arch (MLA) have been implicated in the development of flat feet. However, the relationship between the changes in MLA height under increasing load and the morphological and mechanical properties of individual intrinsic and extrinsic foot soft tissue structures is not fully understood. RESEARCH QUESTION: To examine the morphological and mechanical characteristics of the foot soft tissue structures in flat feet when subjected to loading. METHODS: This study consisted of two studies focusing on the extrinsic foot muscles (10 normal feet/11 flat feet) and intrinsic foot muscles (14 normal feet/13 flat feet). Images of the extrinsic and intrinsic foot muscles and plantar fascia (PF) under 10%, 50%, and 90% body weight conditions were obtained using ultrasound-based shear-wave elastography. RESULTS: The cross-sectional area (CSA) of the peroneus brevis was larger in the flat-foot group than in the normal-foot group under all loading conditions. The CSAs of the intrinsic foot muscles (abductor hallucis, flexor digitorum brevis, and quadratus plantae) and thickness of the PF in the flat-foot group decreased significantly with increasing load. As for mechanical characteristics, the stiffness of the flexor digitorum longus and abductor hallucis was higher in the flat-foot group than in the normal group under high loading conditions. In addition, flat feet with greater flexibility tended to exhibit a greater decrease in PF thickness and smaller increase in stiffness. SIGNIFICANCE: Excessive stretching of the intrinsic foot muscles and PF occurs in flat feet, and excessive contraction of the flexor digitorum longus may counteract the excessive lowering of the foot arch. Therefore, it is necessary to promote the contraction of the intrinsic foot musculature in feet with greater flexibility of the MLA during loading.

Compartments of the crural fascia: clinically relevant ultrasound, anatomical and histological findings.

PURPOSE: Compartment syndrome is a surgical emergency that can occur in any part of the body and can cause cell necrosis when maintained over time. The resulting defects can affect the nerves, muscle cells, bone tissue, and other connective tissues inside the compartment, and fasciotomy has to be performed. The anatomical and histological characteristics of the leg make acute, chronic, and exertional compartment syndrome more likely in this limb. For these reasons, knowledge of the ultrasound, anatomical, and histological features of the crural fascia can help in the treatment of leg compartment syndrome. METHODS: Twenty-one cryopreserved lower limbs from adult cadavers and from one 29-week-old fetus were obtained from the dissection room. They were examined by ultrasound and a subsequent anatomical dissection and microscopy to study the crural fascia and its relationship with the different muscles. Anthropometric measurements were taken of the distances from the head of the fibula and lateral malleolus to the origin of the tibialis anterior muscle in the crural fascia, the exit of the superficial fibular nerve, and the fascia covering the deep posterior muscles of the leg. RESULTS: The crural fascia has very important clinical relationships, which can be identified by ultrasound, as the origin of the tibialis anterior muscle at 16.25 cm from the head of the fibula and the exit of the superficial fibular nerve that crosses this fascia at 21.25 cm from the head of the fibula. Furthermore, the presence of a septum that fixes the deep posterior muscles of the leg and the vessels and nerve can be seen by ultrasound and can explain the possible development of a posterior compartmental syndrome of the leg. Awareness of these features will help to keep these structures safe during the surgical treatment of compartment syndrome. CONCLUSION: The ultrasound study allows identification of anatomical structures in the leg and, thus, avoids damage to them during surgery for compartmental syndromes.

A New Player in the Mechanobiology of Deep Fascia: Yes-Associated Protein (YAP).

Recent studies have demonstrated that fascial fibroblasts are susceptible to mechanical stimuli, leading to the remodeling of the extracellular matrix (ECM). Moreover, the extensive literature on Yes-associated protein (YAP) has shown its role in cell mechanics, linking cell properties, such as shape, adhesion, and size, to the expression of specific genes. The aim of this study was to investigate the presence of YAP in deep fascia and its activation after a mechanical stimulus was induced via a focal extracorporeal shockwave (fESW) treatment. Thoracolumbar fascia (TLF) samples were collected from eight patients (age: 30-70 years; four males and four females) who had undergone spine elective surgical procedures at the Orthopedic Clinic of University of Padova. YAP was measured in both tissue and TLF-derived fibroblasts through immunoblotting. COL1A1 and HABP2 gene expression were also evaluated in fibroblasts 2, 24, and 48 h after the fESW treatment. YAP was expressed in all the examined tissues. The ratio between the active/inactive forms (YAP/p-YAP) of the protein significantly increased in fascial fibroblasts after mechanical stimulation compared to untreated cells (p = 0.0022). Furthermore, COL1A1 and HABP2 gene expression levels were increased upon treatment. These findings demonstrate that YAP is expressed in the deep fascia of the thoracolumbar region, suggesting its involvement in fascial mechanotransduction processes, remodeling, regeneration, and fibrogenesis. This study indicates, for the first time, that YAP is a "new player" in the mechanobiology of deep fascia.

Injecting hyaluronan in the thoracolumbar fascia: A model study.

Hyaluronan (HA) has been recently identified as a key component of the densification of thoracolumbar fascia (TLF), a potential contributor to non-specific lower back pain (LBP) currently treated with manual therapy and systemic or local delivery of anti-inflammatory drugs. The aim of this study was to establish a novel animal model suitable for studying ultrasound-guided intrafascial injection prepared from HA with low and high Mw. Effects of these preparations on the profibrotic switch and mechanical properties of TLF were measured by qPCR and rheology, respectively, while their lubricating properties were evaluated by tribology. Rabbit proved to be a suitable model of TLF physiology due to its manageable size enabling both TLF extraction and in situ intrafascial injection. Surprisingly, the tribology showed that low Mw HA was a better lubricant than the high Mw HA. It was also better suited for intrafascial injection due to its lower injection force and ability to freely spread between TLF layers. No profibrotic effects of either HA preparation in the TLF were observed. The intrafascial application of HA with lower MW into the TLF appears to be a promising way how to increase the gliding of the fascial layers and target the myofascial LBP.

Thoracolumbar fascia mobility and chronic low back pain: Phase 1 of a pilot and feasibility study assessing repeated measures and the influence of paraspinal muscle contraction.

BACKGROUND: Differential movement, or shear strain (SS), between layers of thoracolumbar fascia is reduced with chronic low back pain. To provide a foundation for clinical research involving SS, this study assessed temporal stability and the effect of paraspinal muscle contraction on SS in persons with chronic low back pain. METHODS: We used ultrasound imaging to measure SS in adults self-reporting low back pain ≥1 year. Images were obtained by placing a transducer 2-3 cm lateral to L2-3 with participants lying prone and relaxed on a table moving the lower extremities downward 15°, for 5 cycles at 0.5 Hz. To assess paraspinal muscle contraction effects, participants raised the head slightly from the table. SS was calculated using 2 computational methods. Method 1 averaged the maximum SS from each side during the third cycle. Method 2 used the maximum SS from any cycle (2-4) on each side, prior to averaging. SS was also assessed after a 4-week no manual therapy period. RESULTS: Of 30 participants (n = 14 female), mean age was 40 years; mean BMI 30.1. Mean (SE) SS in females with paraspinal muscle contraction was 66% (7.4) (method 1) and 78% (7.8) (method 2); 54% (6.9) (method 1) and 67% (7.3) (method 2) in males. With muscles relaxed, mean SS in females was 77% (7.6) (method 1) or 87% (6.8) (method 2); 63% (7.1) (method 1) and 78% (6.4) (method 2) in males. Mean SS decreased 8-13% in females and 7-13% in males after 4-weeks CONCLUSION: Mean SS in females was higher than males at each timepoint. Paraspinal muscle contraction temporarily reduced SS. Over a 4-week no-treatment period, mean SS (with paraspinal muscles relaxed) decreased. Methods less likely to induce muscle guarding and enabling assessment with broader populations are needed.

The biomechanical consequence of posterior interventions at the thoracolumbar spine on the passively stabilized flexed posture.

In the flexed end-of-range position (e.g., during slumped sitting), the trunk is passively stabilized. Little is known about the biomechanical consequence of posterior approaches on passive stabilization. The aim of this study is to investigate the effect of posterior surgical interventions on local and distant spinal regions. While being fixed at the pelvis, five human torsos were passively flexed. The change in spinal angulation at Th4, Th12, L4 and S1 was measured after level-wise longitudinal incisions of the thoracolumbar fascia, the paraspinal muscles, horizontal incisions of the inter- & supraspinous ligaments (ISL/SSL) and horizontal incision of the thoracolumbar fascia and the paraspinal muscles. Lumbar angulation (Th12-S1) was increased by 0.3° for fascia, 0.5° for muscle and 0.8° for ISL/SSL-incisions per lumbar level. The effect of level-wise incisions at the lumbar spine was 1.4, 3.5 and 2.6 times greater compared to thoracic interventions for fascia, muscle and ISL/SSL respectively. The combined midline interventions at the lumbar spine were associated with 2.2° extension of the thoracic spine. Horizontal incision of the fascia increased spinal angulation by 0.3°, while horizontal muscle incision resulted in a collapse of 4/5 specimens. The thoracolumbar fascia, the paraspinal muscle and the ISL/SSL are important passive stabilizers for the trunk in the flexed end-of-range position. Lumbar interventions needed for approaches to the spine have a larger effect on spinal posture than thoracic interventions and the increase of spinal angulation at the level of the intervention is partially compensated at the neighboring spinal regions.

Three-dimensional fine structures in deep fascia revealed by combined use of cryo-fixed histochemistry and low-vacuum scanning microscopy.

Recent physiological studies have shown that the deep fascia has received much attention concerning clinical medicine; however, histological examination of the deep fascia has not been well established. In this study, we aimed to clarify and visualize the structure of the deep fascia by taking advantage of cryofixation techniques and low-vacuum scanning electron microscopy. As a result, the ultrastructural observations revealed three-dimensional stratification of the deep fascia composed of three layers: the first superficial layer consisting of collagen fibers extending in various directions with blood vessels and peripheral nerves; the second intermediate layer formed by single straight and thick collagen fibers with flexibility; and the third deepest layer, consisting of relatively straight and thin collagen fibers. We explored the use of two hooks to hold a piece of deep fascia in place through the course of cryo-fixation. A comparative observation with or without the hook-holding procedure would indicate the morphological adaptation to physiological stretch and contraction of the deep fascia. The present morphological approach paves the way to visualize three-dimensional ultrastructures for future biomedical studies including clinical pathophysiology.

From Muscle to the Myofascial Unit: Current Evidence and Future Perspectives.

The "motor unit" or the "muscle" has long been considered the quantal element in the control of movement. However, in recent years new research has proved the strong interaction between muscle fibers and intramuscular connective tissue, and between muscles and fasciae, suggesting that the muscles can no longer be considered the only elements that organize movement. In addition, innervation and vascularization of muscle is strongly connected with intramuscular connective tissue. This awareness induced Luigi Stecco, in 2002, to create a new term, the "myofascial unit", to describe the bilateral dependent relationship, both anatomical and functional, that occurs between fascia, muscle and accessory elements. The aim of this narrative review is to understand the scientific support for this new term, and whether it is actually correct to consider the myofascial unit the physiological basic element for peripheral motor control.

Association of the intrinsic foot muscles and plantar fascia with repetitive rebound jumping and jump landing in adolescent athletes: An ultrasound-based study.

BACKGROUND: The characteristics of foot structure in adolescents and adults are different, affecting sports performance and leading to the progression of foot and lower extremity disorders. RESEARCH QUESTION: This study aimed to investigate the relationship between the intrinsic foot muscles (IFM) and plantar fascia morphology and the repetitive rebound jumping and jump landing ability in adolescent athletes. METHODS: A total of 60 adolescent athletes (35 boys and 25 girls) participated in this study. B-mode ultrasonography was used to obtain images of the IFM and plantar fascia morphology [thickness and cross-sectional area (CSA) of the abductor hallucis (AbH), flexor hallucis brevis (FHB), flexor digitorum brevis (FDB), and thickness of the plantar fascia]. The repetitive rebound jump performance was evaluated using the Optojump™ system. Participants were instructed to jump five times continuously with one leg, jumping as high as possible with minimal ground contact time. The jump landing was assessed by measuring the dynamic posture stability index (DPSI) using forward one-legged jump landings. RESULTS: The thickness and CSA of the AbH and FDB were positively correlated with the jump height and reactive jump index. The DPSI score was significantly correlated with the thickness of the AbH, but not with other IFMs or plantar fascia. In the multiple regression analysis, only the thickness of the FDB was associated with the jump height and reactive jump index, indicating that FDB thickness might facilitate adolescent athletes to jump higher with minimal contact time in repetitive rebounding movements. SIGNIFICANCE: The IFM (especially FDB) should be focused on when examining sports performance in adolescent athletes.

Pericapsular nerve group block versus fascia iliaca block for perioperative analgesia in hip fracture surgery: a prospective randomized trial.

The aim of our study was to evaluate the efficacy of the pericapsular nerve group block (PENG) versus the supra-inguinal fascia iliaca compartment block (SI-FICB) to improve analgesia during positioning for spinal anesthesia (SA) for hip fracture surgery. We conducted a prospective randomized clinical trial involving patients who will undergo hip fracture surgery under SA and randomized into two groups: the PENG group: patients who received PENG block with 10 ml of 0.25% bupivacaine and 10 ml of 2% lidocaine and the SI-FICB group: patients who received SI-FICB block with the same solution. Our primary outcome was the Visual Analogue Scale (VAS) score at positioning for SA. Secondary outcomes were VAS after the block, the ease of spinal positioning (EOSP), the time to perform the block, the postoperative morphine consumption, and the VAS score at the 3rd, 6th, 12th, and 24th postoperative hours. Eighty-nine patients were enrolled and randomized into two groups: 44 in the PENG group and 45 in the SI-FICB group. The time of block performance was comparable in both groups (p = 0.195). There was a significant decrease in pain scores in the 2 groups, 20 min after the blocks at rest and while positioning for SA. PENG block provided better analgesia than SI-FICB block at positioning (P=0.046) with no significant difference in the ease of positioning (p=0.328). The morphine consumption was comparable in the 2 groups (p = 0.842). There was no significant difference in VAS scores at the 3rd, 6th, 12th, and 24th postoperative hours with p respectively 0.061, 0.767, 0.198, and 0.130. Both PENG and SI-FICB blocks provided adequate perioperative analgesia with the superiority of the PENG block in the sitting position for SA.

Evidence of in-vivo myofascial force transfer in humans- a systematic scoping review.

BACKGROUND: The fascial system not only enables the body to operate in an integrated manner but modifies its tension in response to the stress on it. Recent animal, cadaveric and in-vitro trials have shown that "myofascial force transmission" (MFT) can play a major role in homeostasis, musculoskeletal function and pain. Human evidence for the in-vivo existence of MFT is scarce. OBJECTIVE: This scoping review attempts to gather and interpret the available evidence of the in-vivo existence of MFT in humans, its role in homeostasis, and musculoskeletal function. METHOD: A search of major databases using the keywords 'myofascial force transmission' and 'epimuscular force transmission' yielded 247 articles as of November 2021. For the final analysis, only original in-vivo human studies were considered. In-vitro human studies, cadaveric or animal studies, reviews, and similar studies were excluded. A qualitative analysis of the studies was conducted after rating it with the Oxford's Center for Evidence -based Medicine (CEBM) scale. RESULT: Twenty studies ranging from randomized controlled trials (RCTs) to case studies covering 405 patients have been included in this review. The analysed trials were highly heterogeneous and of lower methodological quality meddling with the quantitative analysis. The majority of the appraised studies demonstrated a higher probability of MFT existence, while two studies revealed a lower probability. CONCLUSION: Our search for proof of the in vivo existence of MFT in humans has led us to support such an existence, albeit prudently. Previous research on animals and human cadavers reinforces our finding. We are optimistic that the forthcoming studies on the topic will pave the way for the unraveling of several musculoskeletal riddles that are currently unknown or less well-known.

Reliability of shear wave elastography for the assessment of gastrocnemius fascia elasticity in healthy individual.

The mechanical properties of the deep fascia, particularly their stiffness, strongly affect the development of muscle pathologies (such as compartment syndrome) and the action of the muscles. However, the mechanical characteristics of the deep muscular fascia are still not clearly understood. The present study focuses on examining the reliability of ultrasonic shear wave elastography (USWE) devices in quantifying the shear modulus of the gastrocnemius fascia in healthy individuals, particularly their ability to measure the shear modulus of the deep fascia of the gastrocnemius during ankle dorsiflexion. Twenty-one healthy males (age: 21.48 ± 1.17 years) participated in the study. Using USWE, the shear moduli of the medial gastrocnemius fascia (MGF) and lateral gastrocnemius fascia (LGF) were quantified at different angles during passive lengthening. The two operators took turns measuring each subject's MGF and LGF over a 1-h period, and operator B took an additional measurement 2 h later. For the intra-operator test, the same subjects were measured again at the same time of day 5 days later. Both the intrarater [intraclass correlation coefficient (ICC) = 0.846-0.965)] and interrater (ICC = 0.877-0.961) reliability values for measuring the shear moduli of the MGF and LGF were rated as excellent; the standard error of the mean (SEM) was 3.49 kPa, and the minimal detectable change (MDC) was 9.68 kPa. Regardless of the ankle angle, the shear moduli of the LGF were significantly greater than that of the MGF (p < 0.001). Significant increases in the shear moduli of both the MGF and the LGF were observed in the neutral position compared to the relaxed position. These results indicate that USWE is a reliable technique to assess the shear modulus of the gastrocnemius fascia and detect its dynamic changes during ankle dorsiflexion. USWE can be used for biomechanical studies and intervention experiments concerning the deep fascia.

Effects of plyometric training on muscle-tendon mechanical properties and behavior of fascicles during jumping.

The purpose of this study was to investigate the effects of plyometric training on the muscle-tendon mechanical properties and behavior of fascicles during jumping in order to elucidate the mechanisms of improved jump performance due to plyometric training. Eleven subjects completed a 12-week unilateral training program for plantar flexors. Active muscle stiffness with (100°·s-1 ) and without (250°·s-1 ) stretch reflex were calculated according to changes in muscle force and fascicle length during fast stretching after submaximal isometric contractions. Stiffness and hysteresis of tendon were measured using ultrasonography during ramp and ballistic contractions. Three kinds of unilateral jump heights using only ankle joint (no counter-movement jump: no-CMJ; counter-movement jump: CMJ; drop jump: DJ) on sledge apparatus were measured. During jumping, electromyographic activities (mEMG) of plantar flexors and fascicle length of the medial gastrocnemius muscle were measured. Active muscle stiffness at 250 and 100°·s-1 and maximal tendon elongation during ballistic contraction significantly increased after training. Tendon hysteresis during ballistic contraction significantly decreased after training, whereas that during ramp contraction did not. The heights of three jump tests, the ratio of mEMG during eccentric to that during concentric phases for CMJ, and the amount of fascicle shortening and shortening velocity during eccentric phase of DJ significantly increased after training. These results suggest that an increase in CMJ height was associated with changes in the muscle-tendon mechanical properties and muscle activation strategy, whereas an increase in DJ height could be explained by changes in the muscle-tendon mechanical properties, but not muscle activation strategy.

Is "Delayed Onset Muscle Soreness" a False Friend? The Potential Implication of the Fascial Connective Tissue in Post-Exercise Discomfort.

Strenuous and unaccustomed exercise frequently lead to what has been coined "delayed onset muscle soreness" (DOMS). As implied by this term, it has been proposed that the associated pain and stiffness stem from micro-lesions, inflammation, or metabolite accumulation within the skeletal muscle. However, recent research points towards a strong involvement of the connective tissue. First, according to anatomical studies, the deep fascia displays an intimate structural relationship with the underlying skeletal muscle and may therefore be damaged during excessive loading. Second, histological and experimental studies suggest a rich supply of algogenic nociceptors whose stimulation evokes stronger pain responses than muscle irritation. Taken together, the findings support the hypothesis that DOMS originates in the muscle-associated connective tissue rather than in the muscle itself. Sports and fitness professionals designing exercise programs should hence consider fascia-oriented methods and techniques (e.g., foam rolling, collagen supplementation) when aiming to treat or prevent DOMS.

Attachment of the levator ani muscle extends to the superior ramus of the pubic bone through electrophysiological and anatomical examinations.

Myofascial pelvic pain (MFPP) of pelvic floor muscles is a common cause of chronic pelvic pain (CPP). The pathological mechanisms and treatments of MFPP are complex and still unclear until now. The levator ani muscle (LAM) is the major pelvic floor muscle. The purpose of this study was to examine the fascia and attachment of LAM through the electromyogram (EMG) and cadaver dissection. Electrophysiological stimulation of the obturator fascia above the arcus tendinous levator ani (ATLA) could trigger contraction and electrophysiological changes in LAM insertion. The LAM of embalmed adult cadavers was examined especially in the area above the ATLA. Some skeletal muscle fibers were found above the ATLA within the obturator fascia and were confirmed by Masson's trichrome section staining. Our electromyography (EMG) and anatomical data implied that the attachment of LAM aponeurosis extended beyond ATLA to the inferior border of the superior ramus of the pubic bone. The new discovered attachment of LAM could provide a reference position for clinical diagnosis and treatment of MFPP or CPP.

On the morphological relations of the Achilles tendon and plantar fascia via the calcaneus: a cadaveric study.

Current treatments of plantar fasciitis are based on the premise that the Achilles tendon (AT) and plantar fascia (PF) are mechanically directly linked, which is an area of debate. The aim of this study was to assess the morphological relationship between the AT and PF. Nineteen cadaveric feet were x-ray imaged, serially sectioned and plastinated for digital image analyses. Measurements of the AT and PF thicknesses and cross-sectional areas (CSA) were performed at their calcaneal insertion. The fiber continuity was histologically assessed in representative subsamples. Strong correlations exist between the CSA of the AT and PF at calcaneal insertion and the CSA of PF's insertional length (r = 0.80), and between the CSAs of AT's and PF's insertional lengths. Further correlations were observed between AT and PF thicknesses (r = 0.62). This close morphological relationship could, however, not be confirmed through x-ray nor complete fiber continuity in histology. This study provides evidence for a morphometric relationship between the AT and PF, which suggests the presence of a functional relationship between these two structures following the biological key idea that the structure determines the function. The observed morphological correlations substantiate the existing mechanical link between the AT and PF via the posterior calcaneus and might explain why calf stretches are a successful treatment option for plantar heel pain.

A Closer Look at the Cellular and Molecular Components of the Deep/Muscular Fasciae.

The fascia can be defined as a dynamic highly complex connective tissue network composed of different types of cells embedded in the extracellular matrix and nervous fibers: each component plays a specific role in the fascial system changing and responding to stimuli in different ways. This review intends to discuss the various components of the fascia and their specific roles; this will be carried out in the effort to shed light on the mechanisms by which they affect the entire network and all body systems. A clear understanding of fascial anatomy from a microscopic viewpoint can further elucidate its physiological and pathological characteristics and facilitate the identification of appropriate treatment strategies.

Biomechanical characterization of human temporal muscle fascia in uniaxial tensile tests for graft purposes in duraplasty.

The human temporal muscle fascia (TMF) is used frequently as a graft material for duraplasty. Encompassing biomechanical analyses of TMF are lacking, impeding a well-grounded biomechanical comparison of the TMF to other graft materials used for duraplasty, including the dura mater itself. In this study, we investigated the biomechanical properties of 74 human TMF samples in comparison to an age-matched group of dura mater samples. The TMF showed an elastic modulus of 36 ± 19 MPa, an ultimate tensile strength of 3.6 ± 1.7 MPa, a maximum force of 16 ± 8 N, a maximum strain of 13 ± 4% and a strain at failure of 17 ± 6%. Post-mortem interval correlated weakly with elastic modulus (r = 0.255, p = 0.048) and the strain at failure (r = - 0.306, p = 0.022) for TMF. The age of the donors did not reveal significant correlations to the TMF mechanical parameters. Compared to the dura mater, the here investigated TMF showed a significantly lower elastic modulus and ultimate tensile strength, but a larger strain at failure. The human TMF with a post-mortem interval of up to 146 h may be considered a mechanically suitable graft material for duraplasty when stored at a temperature of 4 °C.

Imaging of muscle activity-induced morphometric changes in fibril network of myofascia by two-photon microscopy.

Myofascia, deep fascia enveloping skeletal muscles, consists of abundant collagen and elastin fibres that play a key role in the transmission of muscular forces. However, understanding of biomechanical dynamics in myofascia remains very limited due to less quantitative and relevant approaches for in vivo examination. The purpose of this study was to evaluate the myofascial fibril structure by means of a quantitative approach using two-photon microscopy (TPM) imaging in combination with intravital staining of Evans blue dye (EBD), a far-red fluorescence dye, which potentially labels elastin. With focus on myofascia of the tibial anterior (TA) muscle, the fibril structure intravitally stained with EBD was observed at the depth level of collagen fibrous membrane above the muscle belly. The EBD-labelled fibril structure and orientation in myofascia indicated biomechanical responses to muscle activity and ageing. The orientation histograms of EBD-labelled fibrils were significantly modified depending upon the intensity of muscle activity and ageing. Moreover, the density of EBD-labelled fibrils in myofascia decreased with habitual exercise but increased with muscle immobilization or ageing. In particular, the diameter of EBD-labelled fibrils in aged mice was significantly higher. The orientation histograms of EBD-labelled fibrils after habitual exercise, muscle immobilization and ageing showed significant differences compared to control. Indeed, the histograms in bilateral TA myofascia of exercise mice made simple waveforms without multiple sharp peaks, whilst muscular immobilization or ageing significantly shifted a histogram with sustaining multiple sharp peaks. Therefore, the dynamics of fibre network with EBD fluorescence in response to the biomechanical environment possibly indicate functional tissue adaptation in myofascia. Furthermore, on the basis of the knowledge that neutrophil recruitment occurs locally in working muscles, we suggested the unique reconstruction mechanism involving neutrophilic elastase in the myofascial fibril structure. In addition to the elastolytic susceptibility of EBD-labelled fibrils, distinct immunoreactivities and activities of neutrophil elastase in the myofascia were observed after electric pulse stimulation-induced muscle contraction for 15 min. Our findings of EBD-labelled fibril dynamics in myofascia through quantitative approach using TPM imaging and intravital fluorescence labelling potentially brings new insights to examine muscle physiology and pathology.