A possible energy-saving role for the major fascia of the thigh in running quadrupedal mammals

Experiments were performed to determine the mechanical importance of the fascia lata in stopping the hind limb during its rearward extension and reversing the direction of leg swing. Samples of fascia lata from a number of different mammals were subjected to tensile tests. Tangent Young's moduli reached about 0.5 GPa and stresses at failure about 50 MPa for fascia from each of the species examined. Energy losses incurred in a loading-unloading cycle were generally about 20%. The moment arms of the fascia lata, in combination with its muscle, about the hip and knee joints were determined and the extension of the fascia lata while its muscle is active was estimated. Calculations suggest that the fascia lata could help to reverse the backward swing of the hind limb by recoiling elastically shortly after the foot leaves the ground. Substantial savings of internal kilnetic energy could be made.     

Experimental study of the influence of senescence in the biomechanical properties of the temporal tendon and deep temporal fascia based on uniaxial tension tests

The present study focuses on the determination of human temporal tendons and deep temporal fascia biomechanical behavior. The tensile and shear loads generated by the temporal muscle are transmitted to the masticatory system by the temporal tendons and muscle fascia. Establishing these connective tissues' biomechanical properties will help to develop proper finite element-based simulations of the human masticatory system, which will allow better understanding of diseases affecting the temporomandibular joint. The tissues were harvested from 8 male fresh cadavers, who were subjected to uniaxial tension tests. Available literature states that different connective tissues undergo identical biochemical, cellular and mechanical changes during senescence. Several mechanical phenomena occur during maturation, resulting in stiffer, stronger and more stable connective tissues, although less flexible. Based on this evidence, the present study suggests that older temporal tendon and fascia samples are stiffer than younger ones. We also found significant higher secant moduli with increasing age.     

The late results of cardiac valve replacement using autologous fascia lata

Over an eight-month period beginning in November 1969, 53 patients received 63 fascia lata heart valves at the Toronto General Hospital. The late results of this form of valve substitution are reviewed. The fascia used to fashion the tricuspid valve underwent progressive thickening and contracture and this process caused failure of the prosthesis within months of insertion. The mitral fascial prosthesis failed in a similar manner although the process took longer. The aortic fascia lata valve, however, has not shown progressive thickening after 3½ years and it has so far retained its functional integrity. Indeed, we have been impressed by the excellent clinical results and absence of complications such as thromboembolism although anticoagulation has not been used. We therefore consider that fascia lata valves offer a suitable alternative to other forms of aortic valve substitution, but are unsatisfactory for tricuspid or mitral valve replacement.     

Knee muscle moment arms from MRI and from tendon travel.

We tested magnetic resonance imaging (MRI) as a means to collect geometric data for moment arm estimation. A knee specimen in five successive flexion postures was scanned by MRI, while simultaneously tendon positions of loaded muscles were measured (long head of biceps femoris, lateral and medial gastrocnemius, gracilis, rectus femoris, sartorius, semimembranosus, semitendinosus, and tensor fasciae latae). Discrete rotation centres were derived from MRI pictures. Moment arms were estimated as the distances from these centres to the tendons. The ratio of tendon travel over the increment of joint angulation was the alternative, more reliable estimate of the moment arm. An important principal shortcoming of MRI is the impossibility of accounting for force distribution in taut tissue. As a consequence, for some muscles, considerable inaccuracies in moment arm estimation are found in a relatively small range of joint angulation (up to about 30% for the rectus femoris and semimembranosus). For the tensor fasciae latae, the moment arm cannot be estimated by MRI, while the estimate by tendon travel is unreliable owing to the deformability and attachments of the fascia lata.     

An accumulation of proteoglycans in scarred fascia

A little is known about proteoglycan (PG) changes, occuring in the course of scarring of tissues another than skin. The aim of present study was biochemical characterization of glycosaminoglycans (GAGs) and proteoglycans (PGs) of normal and scarred fascia. Samples of normal fascia lata were taken at autopsy from 23 individuals and samples of scarred fascia lata were removed from 23 patients at reoperations for femoral fracture. The obtained tissues were divided into two samples: first of them was submitted to GAG isolation and the second one to PG isolation.GAGs were extracted by extensive papain digestion followed by the fractionation using cetylpyridinium chloride. In order to qualitative and quantitative characterization GAGs were submitted to electrophoresis on cellulose acetate before and after treatment with enzymes, specifically depolymerizing some kinds of GAGs. PGs were extracted using 4 M guanidine HCl followed by purification by forming complexes with Alcian blue. PGs were submitted to gel permeation chromatography on Sepharose 4B. In order to obtain core proteins PGs were depolymerized with chondroitinase ABC. The purified PGs and their core proteins were separated with sodium dodecyl sulphate/polyacrylamide gel electrophoresis (SDS/PAGE). It was found that total GAGs content was significantly elevated in scarred fascia. Both types of fascia contained chondroitin-, dermatan- and heparan sulphates and hyaluronic acid. Dermatan sulphates (DS) were the predominant GAGs of normal and scarred fascia. The contents of all GAG types were increased in scarred fascia. Both types of fascia contained two kinds of dermatan sulphate proteoglycans (DSPGs); first being similar to biglycan and the second one similar to decorin, as it was judged by molecular weight of their native molecules and core proteins as well as type of GAG components. Densitometric analysis showed that decorin is a predominant DSPG in both fascia types, but in scarred tissue the ratio of biglycan to decorin is considerably higher. Moreover, in scarred fascia a large chondroitin sulphate proteoglycan (CSPG) was also observed. The obtained results have shown that the scar formation is accompanied by quantitative and qualitative alterations in GAGs/PGs resembling those observed in hypertrophic skin scars. The biochemical modification of the scarred fascia lata may partly explain the clinically manifested damage to biomechanical properties of this tissue.     

Electron microscopy of human fascia lata: focus on telocytes

From the histological point of view, fascia lata is a dense connective tissue. Although extracellular matrix is certainly the most predominant fascia's feature, there are also several cell populations encountered within this structure. The aim of this study was to describe the existence and characteristics of fascia lata cell populations viewed through a transmission electron microscope. Special emphasis was placed on telocytes as a particular interstitial cell type, recently discovered in a wide variety of tissues and organs such as the heart, skeletal muscles, skin, gastrointestinal tract, uterus and urinary system. The conducted study confirmed the existence of a telocyte population in fascia lata samples. Those cells fulfil main morphological criteria of telocytes, namely, the presence of very long, thin cell processes (telopodes) extending from a relatively small cell body. Aside from telocytes, we have found fibroblasts, mast cells and cells with features of myofibroblastic differentiation. This is the first time it has been shown that telocytes exist in human fascia. Currently, the exact role of those cells within the fascia is unknown and definitely deserves further attention. One can speculate that fascia lata telocytes likewise telocytes in other organs may be involved in regeneration, homeostasis and intracellular signalling.     

Location-dependent variations in the material properties of the anterior cruciate ligament.

Our recent anterior drawer studies in human cadaveric knees [Guan and Butler, Adv. Bioengng 17, 5 (1990); Guan et al., Trans. orthop. Res. Soc. 16, 589 (1991)] have suggested that anterior bundles of the anterior cruciate ligament (ACL) develop higher load-related material properties than posterior bundles. This was confirmed when we reevaluated the axial failure data for these bundle-bone specimens from an earlier study [Butler et al., J. Biomechanics 19, 425-432 (1986)]. The purpose of this study was to determine, in a larger data set, if anteromedial and anterolateral bundles of the anterior cruciate ligament exhibit significantly larger load-related material properties than the posterior ligament bundles. Seven ACL-bone units from seven donors (the three tissues from the original study plus four new ones) were subdivided into three subunits, preserving the bone insertions. The subunits were failed in tension at a constant strain rate (100% s-1) and four material properties were compared within and between donors. The anterior bundles developed significantly larger moduli, maximum stresses, and strain energy densities to maximum stress than the posterior subunits. Moduli for the anterior vs posterior subunits averaged 284 MPa vs 155 MPa, maximum stresses averaged 38 MPa vs 15 MPa, and strain energy densities averaged 2.7 N m cc-1 vs 1.1 N m cc-1, respectively. No significant differences were found, however, among strains to maximum stress or between any of the other properties for the two anterior subunits. These results are important to the design of ligament replacements and suggest new experiments designed to distinguish in vivo force levels in these ACL bands, a possible reason for the material differences.     

Site specificity of mechanical and structural properties of human fascia lata and their gender differences: A cadaveric study

The whole thigh muscles are covered with the fascia lata, which could have morphological and mechanical features that match the underlying muscles’ functions. In this study, we investigated the morphological and elastic properties of the human fascia lata taken from four (anterior, medial, lateral, and posterior) sites on the thigh of 17 legs of 12 cadavers (6 males and 6 females, 75–92 years). The thickness of the fascia lata was determined with a caliper. The interwoven collagen fiber’s directions were measured and classified into longitudinal, transverse, and diagonal in two opposing directions, relative to the thigh. Tensile strength test along the longitudinal and transverse directions was performed, and the stiffness, Young’s modulus, and hysteresis were determined. Fascia lata at the lateral site (0.8 ± 0.2 mm) was significantly thicker compared to other sites (0.2–0.3 mm). Fiber’s directions showed substantial variability among sites, and longitudinally directed fibers were higher in proportion (28–32%) than those in other directions (20–27%) at all sites except for the posterior site. The stiffness and Young’s modulus in the longitudinal direction (20–283 N/mm; 71.6–275.9 MPa, highest at the lateral site) were significantly higher than in the transverse direction (3–16 N/mm; 3.2–41.9 MPa, lowest at the lateral site). At the medial site, the proportion of the transversely directed fibers was higher in females than males, with higher stiffness and Young’s modulus thereof. The present study shows that the fascia lata possesses site- and gender-dependence of the morphological characteristics and elastic properties.     

Relaxation incision and fascia lata grafting in the surgical correction of penile curvature in Peyronie's disease

The purpose of this study was to evaluate the effects of treatment of curvature in Peyronie's disease with a relaxation incision and fascia lata grafting. Between 2000 and 2002, this technique was used for 12 patients with a 1-year history of plaque and curvature of more than 35 degrees. Penile degloving was performed with a circumferential incision. The tunica defect was closed with fascia lata grafting after a relaxation incision. For all patients, penile curvature was corrected and normal erections were achieved. No complication was observed in 9 to 24 months (mean, 10 months) of follow-up monitoring. The initial results suggested that tunica albuginea incision and fascia lata grafting could represent an alternative for the treatment of curvature in Peyronie's disease. Further studies are warranted.     

Mechanical compression-induced pressure sores in rat hindlimb: muscle stiffness, histology, and computational models.

Pressure sores affecting muscles are severe injuries associated with ischemia, impaired metabolic activity, excessive tissue deformation, and insufficient lymph drainage caused by prolonged and intensive mechanical loads. We hypothesize that mechanical properties of muscle tissue change as a result of exposure to prolonged and intensive loads. Such changes may affect the distribution of stresses in soft tissues under bony prominences and potentially expose additional uninjured regions of muscle tissue to intensified stresses. In this study, we characterized changes in tangent elastic moduli and strain energy densities of rat gracilis muscles exposed to pressure in vivo (11.5, 35, or 70 kPa for 2, 4, or 6 h) and incorporated the abnormal properties that were measured in finite element models of the head, shoulders, pelvis, and heels of a recumbent patient. Using in vitro uniaxial tension testing, we found that tangent elastic moduli of muscles exposed to 35 and 70 kPa were 1.6-fold those of controls (P < 0.05, for strains /=5%). Histological (phosphotungstic acid hematoxylin) evaluation showed that this stiffening accompanied extensive necrotic damage. Incorporating these effects into the finite element models, we were able to show that the increased muscle stiffness in widening regions results in elevated tissue stresses that exacerbate the potential for tissue necrosis. Interfacial pressures could not predict deep muscle (e.g., longissimus or gluteus) stresses and injuring conditions. We conclude that information on internal muscle stresses is required to establish new criteria for pressure sore prevention.     

Designing a surgical device for harvesting autologous fascia lata grafts as a minimal invasive procedure]

AIMS: Fascia lata is used in different shapes and sizes as a graft material in surgical procedures. The conventional method of harvesting a fascia lata graft is through a long skin incision on the lateral aspect of the thigh. Minimal invasive procedures have been established to reduce the disadvantages of an extensive surgical approach for obtaining the autotransplant. However, they do not facilitate to suture the remaining fascia after harvesting the transplant and therefore bear the risk of a symptomatic herniation of the muscle belly. The aim of this study was to design a surgical device to harvest a fascia lata graft and close the resulting fascia defect as a minimal invasive procedure. MATERIALS AND METHODS: The prototype was tested in 11 human cadaver specimens. It was introduced subcutanously via two small skin incisions. The device contained a special fixation- and working mechanism which enabled the fascial closure using a continuous suture. After the harvest procedure, both the transplant and the sutured fascia lata were examined. RESULTS: The experiments demonstrated the suitability of this method for minimal invasive harvesting of fascia lata. The removed transplants complied in all experiments with the expected dimensions. The continuous suture of the femoral fascia ran with accurate gaps between the sutures and constant tension without dehiscence. Neither the transplant nor the tissue in the region of harvest have shown unduly macroscopic damage due to the use of the device. CONCLUSION: The designed prototype can be used for harvesting a fascia lata graft and repairing the resulting defect minimal invasively. Clinical implementation seems possible. However, improvements could be made mainly concerning the handling of the device.     

A probabilistic rule of mixtures for elastic moduli

A novel approach is developed for mathematically modeling the variability observed in experimentally determined elastic moduli of longitudinally oriented fibrous tissues such as ligaments and tendons. The elastic modulus of these tissues is modeled with a rule of mixtures (ROM) where each parameter (fibril and matrix moduli and fibril volume fraction) is assumed to be an independent random variable. A joint density function formed from the independent densities results in a probabilistic ROM (pROM). This pROM is used to generate a distribution of moduli which agrees well with moduli determined from tests of rabbit medial collateral ligaments (Woo and Ohland, 1994, Unpublished experimental data as gift). Minimizing the error between the pROM and experimental distributions resulted in an integrated error of 9% for a constrained set of independent distribution parameters derived from the literature. This pROM thus incorporates microstructural observations (fibril and matrix moduli and fibril volume fraction) to partially explain the experimentally observed variability in a macroscopic property (tissue modulus).     

Enhanced vascular biocompatibility of decellularized xeno-/allogeneic matrices in a rodent model

Glutaraldehyde preservation is the gold standard for cardiovascular biological prosthesis. However, secondary calcifications and the absence of tissue growth remain major limitations. Our study assessed in vitro and in vivo the biocompatibility of human (fascia lata, pericardium) and porcine tissues (pericardium, peritoneum) treated with a physicochemical procedure for decellularization and non-conventional pathogens inactivation. Biopsies were performed before and after treatment to assess decellularization (HE/Dapi staining/DNA quantification/MHC I/alpha gal immunostaining) and mechanical integrity. Forty-five rats received an abdominal aortic patch of native cryopreserved tissues (n = 20), treated tissues (n = 20) or glutaraldehyde-preserved bovine pericardium (GBP, control, n = 5). Grafts were explanted at 4 weeks and processed for HE/von Kossa staining and immunohistochemistries for lymphocytes (CD3)/macrophages (CD68) histomorphometry. 95% of decellularization was obtained for all tissues except for fascia lata (75%). Mechanical properties were slightly altered. In the in vivo model, a significant increase of CD3 and CD68 infiltrations was found in native and control implants in comparison with decellularized tissues (p < 0.05). Calcifications were found in 3 controls. Decellularized tissues were recolonized. GBP showed the most inflammatory response. This physicochemical treatment improves the biocompatibility of selected xeno/allogeneic tissues in comparison with their respective native cryopreserved tissues and with GBP. Incomplete decellularization is associated with a significantly higher inflammatory response. Our treatment is a promising tool in the field of tissue decellularization and tissue banking.     

Lower eyelid reconstruction with a cheek flap supported by fascia lata.

The use of a cheek rotation flap is a well-known method for reconstruction of a large defect of the lower eyelid. In this technique, a separate lining tissue supporting the cheek flap is required for full-thickness reconstruction. Previously, a chondromucosal graft or conchal cartilage has been used to support this flap. Recently, we have used a homologous or autologous fascia lata as support for the cheek flap instead of rigid tissues like cartilages. A fascia lata strip is fixed with tolerable tension to the medial canthal tendon and lateral orbital rim. The inner surface of the fascia and the cheek flap is lined with a buccal mucosa graft to decrease irritation of the conjunctiva and cornea. We present here seven patients in whom this procedure was used for lower eyelid reconstruction following resection of a malignant skin tumor. Based on follow-ups of 7 to 22 months, the functional and aesthetic results have been good in all cases. This procedure may be applicable for total or subtotal reconstruction of the lower eyelid.     

A cryo-jaw designed for in vitro tensile testing of the healing Achilles tendons in rats

We present a simple but very secure non-compressive clamping device for in vitro tensile testing of the Achilles tendon in rats. Biomechanical studies were performed on 178 native and injured specimens without any registration of slippage out of the clamp. The average tensile strength of the native rat Achilles tendon was determined to be 48 N (+/-11 N) and its displacement to failure averaged 0.8 mm (+/-0.2 mm). The mean values for tensile strength within the injured tendons increased with time and were above the native tendon values from week 2 and later. Correspondingly, the displacement to failure decreased with time.     

Effect of low dose and moderate dose gamma irradiation on the mechanical properties of bone and soft tissue allografts

The increased use of allograft tissue for musculoskeletal repair has brought more focus to the safety of allogenic tissue and the efficacy of various sterilization techniques. Gamma irradiation is an effective method for providing terminal sterilization to biological tissue, but it is also reported to have deleterious effects on tissue mechanics in a dose-dependent manner. At irradiation ranges up to 25 kGy, a clear relationship between mechanical strength and dose has yet to be established. The aim of this study was to investigate the mechanical properties of bone and soft tissue allografts, irradiated on dry ice at a low absorbed dose (18.3–21.8 kGy) and a moderate absorbed dose (24.0–28.5 kGy), using conventional compressive and tensile testing, respectively. Bone grafts consisted of Cloward dowels and iliac crest wedges, while soft tissue grafts consisted of patellar tendons, anterior tibialis tendons, semitendinosus tendons, and fascia lata. There were no statistical differences in mechanical strength or modulus of elasticity for any graft irradiated at a low absorbed dose, compared to control groups. Also, bone allografts and two soft tissue allografts (anterior tibialis and semitendinosus tendon) that were irradiated at a moderate dose demonstrated similar strength and modulus of elasticity values to control groups. The results of this study support the use of low dose and moderate dose gamma irradiation of bone grafts. For soft tissue grafts, the results support the use of low dose irradiation.     

Mechanical and structural changes in rat tail tendon induced by alloxan diabetes and aging

The structure and mechanical properties of tail tendons from rats made diabetic by alloxan monohydrate injection were studied. Several differences are revealed upon comparison with normal tendons from control rats of identical age. In diabetic tendon an increase in the apparent failure region moduli, decreased stress relaxation rate, alterations of the crimp structure and a tendency toward larger collagen fibril diameters are observed. Some of these changes resemble aging acceleration while others must be ascribed to other hypothetical causes.     

The impact of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking in Thailand

Tissue banking started in Thailand in 1979. Five years after this, the Bangkok Biomaterial Centre (BBC) was established in the Faculty of Medicine, Siriraj Hospital, with the support of the IAEA program. The objective of the Centre was to provide sterile bones and tissues for clinical use. Through the passage of time, the Bangkok Biomaterial Centre has gained confidence from the end user and by 2007 has processed 33,872 allografts from 491 deceased donors and 4,035 live donors were used in medical treatment in 3,596 patients in more than 79 different hospitals. More than 305 surgeons from Thailand used the tissue produced in the BBC. At the beginning of its work the BBC concentrate its activities on the production of the following tissues: freeze dried bone, freeze dried dura mater and freeze dried fascia lata. All of these tissues were sterilised using ethylene oxide gas until the end of year 1984. Since 1985 the BBC sterilise tissue using ionising radiation. The BBC is now producing deep-frozen; bone tendon, cartilage, trachea and soft tissue; freeze-dried; bone, fascia lata, dura mater, amniotic membrane, bone hydroxyapatite, bone tablet and fresh preserved amniotic membrane Yongyudh Vajaradul is a Founder of Bangkok Biomaterial Centre and also a President of TATB, Bangkok, Thailand. Jorge Morales Pedraza is a former IAEA Interregional Project Manager, Vienna, Austria.     

The biomechanical effects of limb lengthening and botulinum toxin type A on rabbit tendon

Numerous studies have examined the effects of distraction osteogenesis (DO) on bone, but relatively fewer have explored muscle adaptation, and even less have addressed the concomitant alterations that occur in the tendon. The purpose herein was to characterize the biomechanical properties of normal and elongated rabbit (N=20) tendons with and without prophylactic botulinum toxin type A (BTX-A) treatment. Elastic and viscoelastic properties of Achilles and Tibialis anterior (TA) tendons were evaluated through pull to failure and stress relaxation tests.All TA tendons displayed nonlinear viscoelastic responses that were strain dependent. A power law formulation was used to model tendon viscoelastic responses and tendon elastic responses were fit with a microstructural model. Distraction-elongated tendons displayed increases in compliance and stress relaxation rates over undistracted tendons; BTX-A administration offset this result. The elastic moduli of distraction-lengthened TA tendons were diminished (p=0.010) when distraction was combined with gastrocnemius (GA) BTX-A administration, elastic moduli were further decreased (p=0.004) and distraction following TA BTX-A administration resulted in TA tendons with moduli not different from contralateral control (p>0.05). Compared to contralateral control, distraction and GA BTX-A administration displayed shortened toe regions, (p=0.031 and 0.038, respectively), while tendons receiving BTX-A in the TA had no differences in the toe region (p>0.05). Ultimate tensile stress was unaltered by DO, but stress at the transition from the toe to the linear region of the stress–stretch curve was diminished in all distraction-elongated TA tendons (p<0.05). The data suggest that prophylactic BTX-A treatment to the TA protects some tendon biomechanical properties.     

Mechanical properties of rat tail tendon in relation to proximal-distal sampling position and age

The mechanical properties of 3, 15 and 25 month-old rat tail tendons were investigated in relation to proximal-distal sampling location along the fibre length. For the 15 and 25 month-old tendons maximum load as well as collagen content per mm fibre length (unit collagen) increased markedly from the proximal to the distal location. A linear regression analysis of the collagen content and mechanical parameters (maximum load, maximum slope of the load-strain curve and energy absorption) showed that these parameters were linearly correlated to the collagen content. However, normalization of the mechanical parameters with regard to the collagen content did not cancel the dependency of the parameters on proximal-distal sampling location. Normalized load and energy values for the 3 month-old tendons and normalized slope values for the 15 and 25 month-old tendons were found to decrease from proximal to distal location. These findings showed that tail tendons are heterogeneous along their length in respect to mechanical strength. The regression analysis also indicated the existence of an inverse relationship between unit collagen and mechanical quality of the collagen. Alternatively, the mechanical properties of tendon fibres might be influenced by other components than collagen.