Compressive properties of cd-HA-gelatin modified intrasynovial tendon allograft in canine model in vivo

Although we sometimes use the intrasynovial tendon allograft as a donor, the gliding ability of allograft prepared by lyophilization is significantly decreased. The gliding ability of the grafted tendon after tendon reconstruction is very important because the high gliding resistance causes more adhesion and leads to poor clinical results. We recently revealed that tendon surface treatment with a carbodiimide derivatized HA (cd-HA)-gelatin mixture for intrasynovial tendon allograft significantly improved its gliding ability. The purpose of this study was to investigate whether this cd-HA-gelatin treatment affects the tendon mechanical property or not. A total of 40 flexor digitorum profundus (FDP) tendons from canines were evaluated for compressive property by using indentation test. Indentation stiffness was measured for normal tendon, rehydrated tendon after lyophilization, rehydrated tendon after lyophilization that was implanted 6 weeks in vivo, and cd-HA treated rehydrated tendon after lyophilization that was implanted 6 weeks in vivo. The results for all groups showed no significant difference in the tendon compressive properties. The findings of these results demonstrate that cd-HA treatment for intrasynovial tendon allograft is an excellent method to improve the tendon gliding ability after lyophilization without changing the compressive property of donor tendon.     

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.     

Biomechanical and structural response of healing Achilles tendon to fatigue loading following acute injury

Achilles tendon injuries affect both athletes and the general population, and their incidence is rising. In particular, the Achilles tendon is subject to dynamic loading at or near failure loads during activity, and fatigue induced damage is likely a contributing factor to ultimate tendon failure. Unfortunately, little is known about how injured Achilles tendons respond mechanically and structurally to fatigue loading during healing. Knowledge of these properties remains critical to best evaluate tendon damage induction and the ability of the tendon to maintain mechanical properties with repeated loading. Thus, this study investigated the mechanical and structural changes in healing mouse Achilles tendons during fatigue loading. Twenty four mice received bilateral full thickness, partial width excisional injuries to their Achilles tendons (IACUC approved) and twelve tendons from six uninjured mice were used as controls. Tendons were fatigue loaded to assess mechanical and structural properties simultaneously after 0, 1, 3, and 6 weeks of healing using an integrated polarized light system. Results showed that the number of cycles to failure decreased dramatically (37-fold, p<0.005) due to injury, but increased throughout healing, ultimately recovering after 6 weeks. The tangent stiffness, hysteresis, and dynamic modulus did not improve with healing (p<0.005). Linear regression analysis was used to determine relationships between mechanical and structural properties. Of tendon structural properties, the apparent birefringence was able to best predict dynamic modulus (R²=0.88–0.92) throughout healing and fatigue life. This study reinforces the concept that fatigue loading is a sensitive metric to assess tendon healing and demonstrates potential structural metrics to predict mechanical properties.     

The Effect of Lubricin on the Gliding Resistance of Mouse Intrasynovial Tendon

The purpose of this study was to investigate the role of lubricin on the gliding resistance of intrasynovial tendons by comparing lubricin knockout, heterozygous, and wild type mice. A total of thirty-six deep digital flexor (DDF) tendons in the third digits of each hind paw from eighteen adult mice were used, including six lubricin knockout mice (Prg4 –/–), six heterozygous mice (Prg4 +/–), and six wild type mice (Prg4 +/+). The tendon gliding resistance was measured using a custom-made device. Tendon structural changes were evaluated by scanning electron and light microscopy. The gliding resistance of intrasynovial tendons from lubricin knockout mice was significantly higher than the gliding resistance of either wild type or heterozygous mice. The surface of the lubricin knockout tendons appeared to be rougher, compared to the wild type and heterozygous tendons. Synovial hyperplasia was found in the lubricin knockout mice. Cartilage-like tissue was found in the tendon and pulley of the lubricin knockout mice. Our findings confirm the importance of lubricin in intrasynovial tendon lubrication. This knockout model may be useful in determining the effect of lubricin on tendon healing and the response to injury.     

Human patellar tendon stiffness is restored following graft harvest for anterior cruciate ligament surgery

Minimising post-operative donor site morbidity is an important consideration when selecting a graft for surgical reconstruction of the torn anterior cruciate ligament (ACL). One of the most common procedures, the bone-patellar tendon-bone (BPTB) graft involves removal of the central third from the tendon. However, it is unknown whether the mechanical properties of the donor site (patellar tendon) recover. The present study investigated the mechanical properties of the human patellar tendon in 12 males (mean±S.D. age: 37±14 years) who had undergone surgical reconstruction of the ACL using a BPTB graft between 1 and 10 years before the study (operated knee; OP). The uninjured contralateral knee served as a control (CTRL). Patellar tendon mechanical properties were assessed in vivo combining dynamometry with ultrasound imaging. Patellar tendon stiffness was calculated from the gradient of the tendon's force–elongation curve. Tendon stiffness was normalised to the tendon's dimensions to obtain the tendon's Young's modulus. Cross-sectional area (CSA) of OP patellar tendons was larger by 21% than CTRL tendons (P<0.01). Patellar tendon stiffness was not significantly different between OP and CTRL tendons, but the Young's modulus was lower by 24% in OP tendons (P<0.01). A compensatory enlargement of the patellar tendon CSA, presumably due to scar tissue formation, enabled a recovery of tendon stiffness in the OP tendons. The newly formed tendon tissue had inferior properties as indicated by the reduced tendon Young's modulus, but it increased to a level that enabled recovery of tendon stiffness.     

Enhancing the Viability of Lactobacillus plantarum Inoculum by Immobilizing the Cells in Calcium-Alginate Beads Incorporating Cryoprotectants

Many literature reports have cited the importance of the rehydration conditions of lyophilized cultures in determining viability. The rate of rehydration and the volume of fluid used have been identified as two important factors. One possible means of controlling these is by immobilizing the cells before lyophilization within a gel matrix in which the subsequent rehydration rate and fluid volume would be controlled by the properties of the gel. In this study Lactobacillus plantarum was immobilized and lyophilized in Ca-alginate beads in which 1 M glycerol or 0.75 M adonitol with skim milk were incorporated as a cryoprotectant. The properties of these Ca-alginate beads were examined before and after lyophilization and rehydration. The beads incorporating glycerol were smaller and stronger than those with adonitol. After lyophilization, size decreased and strength increased but to a greater extent in the beads with glycerol, indicating that the microenvironment within the two bead types was probably different. The protective effect of the bead microenvironment on immobilized L. plantarum was also examined. Lyophilization and rehydration within the alginate beads with either polyol yielded higher survival rates than that attained with free cell cultures during rehydration in optimal or suboptimal conditions. During rehydration under suboptimal conditions, the immobilized cell survival was greatest when 0.75 M adonitol was the incorporated cryoprotectant.     

Tensile properties and fiber alignment of human supraspinatus tendon in the transverse direction demonstrate inhomogeneity,nonlinearity, and regional isotropy

A recent study (Lake et al., 2009); reported the properties of human supraspinatus tendon (SST) tested along the predominant fiber direction. The SST was found to have a relatively disperse distribution of collagen fibers, which may represent an adaptation to multiaxial loads imposed by the complex loading environment of the rotator cuff. However, the multiaxial mechanical properties of human SST remain unknown. The objective of this study, therefore, was to evaluate the mechanical properties, fiber alignment, change in alignment with applied load, and structure–function relationships of SST in transverse testing. Samples from six SST locations were tested in uniaxial tension with samples oriented transverse to the tendon long-axis. Polarized light imaging was used to quantify collagen fiber alignment and change in alignment under applied load. The mechanical properties of samples taken near the tendon–bone insertion were much greater on the bursal surface compared to the joint surface (e.g., bursal moduli 15–30 times greater than joint; p<0.001). In fact, the transverse moduli values of the bursal samples were very similar to values obtained from samples tested along the tendon long-axis (Lake et al., 2009). This key and unexpected finding suggests planar mechanical isotropy for bursal surface samples near the insertion, which may be due to complex in vivo loading. Organizationally, fiber distributions became less aligned along the tendon long-axis in the toe-region of the stress–strain response. Alignment changes occurred to a slightly lesser degree in the linear-region, suggesting that movement of collagen fibers may play a role in mechanical nonlinearity. Transverse mechanical properties were significantly correlated with fiber alignment (e.g., for linear-region modulus r_s=0.74, p<0.0001), demonstrating strong structure–function relationships. These results greatly enhance current understanding of the properties of human SST and provide clinicians and scientists with vital information in attempting to treat or replace this complex tissue.     

Functionally distinct tendons have different biomechanical,biochemical and histological responses to in vitro unloading

Tendons with different in vivo functions are known to have different baseline biomechanics, biochemistry and ultrastructure, and these can be affected by changes in loading. However it is not know whether different tendon types respond in the same, or different ways, to changes in loading.This study performed in vitro un-loading (stress deprivation) in culture on ovine medial extensor tendons (MET, a positional tendon), and superficial and deep digital flexor tendons (SDFTs and DDFTs, with energy-storing and intermediate functions respectively), for 21 days (n = 14 each). Tensile strength and elastic modulus were then measured, followed by biochemical assays for sulphated glycosaminoglycan (sGAG) and hydroxyproline content. Histological inspection for cell morphology, cell density and collagen alignment was also performed.The positional tendon (MET) had a significant reduction (∼50%) in modulus and strength (P < 0.001) after in vitro stress-deprivation, however there were no significant effects on the energy-storing tendons (SDFT and DDFT). In contrast, sGAG was not affected in the MET, but was reduced in the SDFT and DDFT (P < 0.001). All tendons lost compactness and collagen organisation, and had reduced cell density, but these were more rapid in the MET than the SDFT and DDFT.These results suggest that different tendon types respond to identical stimuli in different ways, thus; (i) the results from an experiment in one tendon type may not be as applicable to other tendon types as previously thought, (ii) positional tendons may be particularly vulnerable to clinical stress-deprivation, and (iii) graft tendon source may affect the biological response to loading in ligament and tendon reconstruction.     

Shear Elastic Modulus on Patellar Tendon Captured from Supersonic Shear Imaging: Correlation with Tangent Traction Modulus Computed from Material Testing System and Test–Retest Reliability

Characterization of the elastic properties of a tendon could enhance the diagnosis and treatment of tendon injuries. The purpose of this study was to examine the correlation between the shear elastic modulus on the patellar tendon captured from a Supersonic Shear Imaging (SSI) and the tangent traction modulus computed from a Material testing system (MTS) on 8 fresh patellar pig tendons (Experiment I). Test–retest reliability of the shear elastic modulus captured from the SSI was established in Experiment II on 22 patellar tendons of 11 healthy human subjects using the SSI. Spearman Correlation coefficients for the shear elastic modulus and tangent traction modulus ranged from 0.82 to 1.00 (all p<0.05) on the 8 tendons. The intra and inter-operator reliabilities were 0.98 (95% CI: 0.93–0.99) and 0.97 (95% CI: 0.93–0.98) respectively. The results from this study demonstrate that the shear elastic modulus of the patellar tendon measured by the SSI is related to the tangent traction modulus quantified by the MTS. The SSI shows good intra and inter-operator repeatability. Therefore, the present study shows that SSI can be used to assess elastic properties of a tendon.     

Base plate mechanics of the barnacle Balanus amphitrite (=Amphibalanus amphitrite)

The mechanical properties of barnacle base plates were measured using a punch test apparatus, with the purpose of examining the effect that the base plate flexural rigidity may have on adhesion mechanics. Base plate compliance was measured for 43 Balanus amphitrite (=Amphibalanus amphitrite) barnacles. Compliance measurements were used to determine flexural rigidity (assuming a fixed-edge circular plate approximation) and composite modulus of the base plates. The barnacles were categorized by age and cement type (hard or gummy) for statistical analyses. Barnacles that were 'hard' (> or =70% of the base plate thin, rigid cement) and 'gummy' (>30% of the base plate covered in compliant, tacky cement) showed statistically different composite moduli but did not show a difference in base plate flexural rigidity. The average flexural rigidity for all barnacles was 0.0020 Nm (SEM +/- 0.0003). Flexural rigidity and composite modulus did not differ significantly between 3-month and 14-month-old barnacles. The relatively low flexural rigidity measured for barnacles suggests that a rigid punch approximation is not sufficient to account for the contributions to adhesion mechanics due to flexing of real barnacles during release.     

Effects of different temperatures, velocities and loads on the gliding resistance of flexor digitorum profundus tendons in a human cadaver model

The purpose of this study was to investigate the effects of temperature, velocity and load on the gliding resistance (GR) of flexor digitorum profundus (FDP) tendons in a human cadaver model. A total of 40 FDP tendons from the index through small digits of ten human cadavers were tested to assess the effect of temperature (4, 23 or 36 °C), velocity (2, 4, 6, 8, 10 or 12 mm/s) and load (250, 500, 750, 1000, 1250 and 1500 g) on GR. The mean GR at 4 °C was significantly higher than the mean GR at 36 °C (p<0.0066). There was no significant difference in the mean GR of the tested velocities. The mean GR was proportional to load, with each successive load having significantly higher GR than the loads before it (all p<0.001). There was no significant difference in the mean GR by digit. In this in vitro model, we have demonstrated that tendon gliding resistance is proportional to load, independent of velocity and somewhat affected by temperature. We conclude that it is important to specify these conditions when reporting gliding resistance, especially load and temperature.     

Effects of supercritical fluid CO<Subscript>2</Subscript> and 25 kGy gamma irradiation on the initial mechanical properties and histological appearance of tendon allograft

Tendon allografts, when autograft options are limited or when obtaining an autograft is not aligned with the patients’ best interest, play an important role in tendon and ligament reconstruction. To minimize the risk of infectious disease transmission tissue banks perform screening tests and the allografts cleaned are sterilized. The current study examines and compares the initial mechanical properties and histological appearance of supercritical CO₂ (SCCO₂)-treated and gamma-irradiated porcine extensor tendons. Thirty intact porcine forelimb extensor tendons randomized equally into three groups: control group, gamma-irradiation group, and SCCO₂-treated group. Once treated, histological assessment and histomorphologic measurements were made on the histological sections obtained from each tendon while stiffness and ultimate failure loads were evaluated from tensile testing. Histological evaluation of gamma-irradiated tendons showed significant disruption to the hierarchical morphology of the fascicle bundles, which was not evident in SCCO₂-treated specimens. Histomorphologic measurements showed a significant increase for measured dead space (void) between tendon fibrils of the gamma-irradiated group comparing to both control and SCCO₂ treated groups (p?<?0.01). There was a significant reduction in the ultimate failure load for tendons treated by gamma-irradiation compared to the control group (p?<?0.05). No statistically significant difference was detected between control and SCCO₂-treated tendons in the ultimate failure load. Stiffness values were not significantly different between three-study groups. This study suggests that while gamma-irradiation has a deleterious effect on mechanical properties of tendon tissue, SCCO₂ does not alter the biomechanical properties and the histological structure of porcine extensor tendons.     

Biomechanical properties of bovine tendon xenografts treated with a modern processing method

Xenograft tendons have been used in few human studies, with variable results. With the advent of novel tissue processing techniques, which may mitigate against an immune-mediated rejection response without adversely affecting mechanical properties, there may now be a clinical role for xenograft tendons, particularly in knee ligament reconstruction. We hypothesize that ‘BioCleanse®’ processed bovine extensor digitorum medialis (EDM) tendons exhibit favorable time-zero pre-implantation biomechanical characteristics when compared to both unprocessed bovine EDM tendons and BioCleanse® processed human cadaveric allograft tibialis anterior tendons.In this in vitro case controlled laboratory study, three groups of tendons underwent a 5-stage static loading test protocol: 15 BioCleanse^® bovine (BCB), 15 fresh frozen unprocessed bovine (FFB), and 12 BioCleanse^® human allograft (BCA) tendons. Cross-sectional area of the grafts was measured using an alginate molding technique, and tendons were mounted within an Instron^® 5565 Materials Testing System using cryogenic clamps.BCB tendons displayed a higher ultimate tensile stress (p<0.05), with equivalent ultimate failure load, creep, and modulus of elasticity when compared to the FFB tendons (p>0.05). BCB tendons had an equivalent cross-sectional area to the BCA tendons (p>0.05) whilst exhibiting a greater failure load, ultimate tensile stress, less creep and a higher modulus of elasticity (p<0.05).The BioCleanse^® process did not adversely affect the time-zero biomechanical properties of bovine xenograft EDM tendons. BioCleanse^® processed bovine xenograft EDM tendons exhibited superior biomechanical characteristics when compared with BioCleanse^® processed allograft tibialis anterior tendons. These findings support further investigation of xenograft tendons in orthopedic soft tissue reconstructive surgery.     

The effect of tendon loading on in-vitro carpal kinematics of the wrist joint

Measurements of in-vitro carpal kinematics of the wrist provide valuable biomechanical data. Tendon loading is often applied during cadaver experiments to simulate natural stabilizing joint compression in the wrist joint. The purpose of this study was to investigate the effect of tendon loading on carpal kinematics in-vitro.A cyclic movement was imposed on 7 cadaveric forearms while the carpal kinematics were acquired by a 4-dimensional rotational X-ray imaging system. The extensor- and flexor tendons were loaded with constant force springs of 50 N, respectively. The measurements were repeated without a load on the tendons. The effect of loading on the kinematics was tested statistically by using a linear mixed model.During flexion and extension, the proximal carpal bones were more extended with tendon loading. The lunate was on the average 2.0° (p=0.012) more extended. With tendon loading the distal carpal bones were more ulnary deviated at each angle of wrist motion. The capitate was on the average 2.4° (p=0.004) more ulnary deviated.During radioulnar deviation, the proximal carpal bones were more radially deviated with the lunate 0.7° more into radial deviation with tendon loading (p<0.001). Conversely, the bones of distal row were more flexed and supinated with the capitate 1.5° more into flexion (p=0.025) and 1.0° more into supination (p=0.011).In conclusion, the application of a constant load onto the flexor and extensor tendons in cadaver experiments has a small but statistically significant effect on the carpal kinematics during flexion–extension and radioulnar deviation.     

The role of tenascin-C in adaptation of tendons to compressive loading

Although most tendon regions are subjected primarily to high tensile loads, selected regions, primarily those that directly contact bones that change the direction of the tendon, must withstand high compressive loads as well. Compressed tendon regions differ from regions subjected to primarily tensile loads: they have a fibrocartilaginous structure with spherical cells surrounded by a matrix containing aggrecan and collagen types I and II, in contrast regions not exposed to compression have a fibrous structure with spindle shaped fibroblasts surrounded by a matrix of dense, longitudinally oriented type I collagen fibrils. The spherical shape of cells in fibrocartilagenous regions indicates these cells are more loosely attached to the matrix than their spindle-shaped counterparts in fibrous regions, a feature that may help to minimize cell deformation during tendon compression. We hypothesized that expression of tenascin-C, an anti-adhesive protein, is part of the adaptation of tendon cells to compression that helps establish and maintain fibrocartilaginous regions. To test this hypothesis we compared tenascin-C content and expression in compressed (distal) versus uncompressed (proximal) segments of bovine flexor tendons. Immunohistochemistry and immunoblot analyses showed that tenascin-C content was increased in the distal tendon where it co-distributed with type II collagen and aggrecan. Tendon cells from the distal segments expressed more tenascin-C than did cells from the proximal segments for up to four days in cell culture, indicating that increased tenascin-C expression is a relatively stable feature of the distal cells. These observations support the hypothesis that tenascin-C expression is a cellular adaptation to compression that helps establish and maintain fibrocartilagenous regions of tendons.     

Resistance training minimizes the biomechanical effects of aging in three different rat tendons

Aging process is characterized by a decline in the organism functionality, especially in the decrease of muscle function, which also affects tendons. On the other hand, the resistance training (RT) has been used as an important tool to increase muscle and tendineous function during aging. Thus, this study aim has been to verify the effects of RT on the biomechanical properties of three different aged rat tendons. For this purpose, 20 wistar rats have been divided into four groups (5 rats per group): young sedentary (YS), trained (YT), old sedentary (OS) and old trained (OT). The RT has been performed through climb protocol for 12 weeks. After RT, the calcaneal tendon (CT), superficial flexor tendon (SFT) and deep flexor tendon (DFT) have been used for analysis. The results indicate that the RT in aged rats can prevent tendon function decrease (p<0.05). Although RT has prompted significant biomechanical changes in trained aged rats, there has been no increase in cross-section area or tendon stiffness reduction. Thus, the OT group showed better biomechanical responses when compared with OS (p<0.05). Therefore, RT can be used as an excellent strategy for increasing in tendon capacity during aging.     

Regional stiffening with aging in tibialis anterior tendons of mice occurs independent of changes in collagen fibril morphology

The incidence of tendon degeneration and rupture increases with advancing age. The mechanisms underlying this increased risk remain unknown but may arise because of age-related changes in tendon mechanical properties and structure. Our purpose was to determine the effect of aging on tendon mechanical properties and collagen fibril morphology. Regional mechanical properties and collagen fibril characteristics were determined along the length of tibialis anterior (TA) tendons from adult (8- to 12-mo-old) and old (28- to 30-mo-old) mice. Tangent modulus of all regions along the tendons increased in old age, but the increase was substantially greater in the proximal region adjacent to the muscle than in the rest of the tendon. Overall end-to-end modulus increased with old age at maximum tendon strain (799 ± 157 vs. 1,419 ± 91 MPa) and at physiologically relevant strain (377 ± 137 vs. 798 ± 104 MPa). Despite the dramatic changes in tendon mechanical properties from adulthood to old age, collagen fibril morphology and packing fraction remained relatively constant in all tendon regions examined. Since tendon properties are influenced by their external loading environment, we also examined the effect of aging on TA muscle contractile properties. Maximum isometric force did not differ between the age groups. We conclude that TA tendons stiffen in a region-dependent manner throughout the life span, but the changes in mechanical properties are not accompanied by corresponding changes in collagen fibril morphology or force-generating capacity of the TA muscle.     

Comparison of elastic,viscoelastic and failure tensile material properties of knee ligaments and patellar tendon

The knee ligaments and patellar tendon function in concert with each other and other joint tissues, and are adapted to their specific physiological function via geometry and material properties. However, it is not well known how the viscoelastic and quasi-static material properties compare between the ligaments. The purpose of this study was to characterize and compare these material properties between the knee ligaments and patellar tendon.Dumbbell-shaped tensile test samples were cut from bovine knee ligaments (ACL, LCL, MCL, PCL) and patellar tendon (PT) and subjected to tensile testing (n = 10 per ligament type). A sinusoidal loading test was performed at 8% strain with 0.5% strain amplitude using 0.1, 0.5 and 1 Hz frequencies. Subsequently, an ultimate tensile test was performed to investigate the stress-strain characteristics.At 0.1 Hz, the phase difference between stress and strain was higher in LCL compared with ACL, PCL and PT (p < 0.05), and at 0.5 Hz that was higher in LCL compared with all other ligaments and PT (p < 0.05). PT had the longest toe-region strain (p < 0.05 compared with PCL and MCL) and MCL had the highest linear and strain-dependent modulus, and toughness (p < 0.05 compared with ACL, LCL and PT).The results indicate that LCL is more viscous than other ligaments at low-frequency loads. MCL was the stiffest and toughest, and its modulus increased most steeply at the toe-region, possibly implying a greater amount of collagen. This study improves the knowledge about elastic, viscoelastic and failure properties of the knee ligaments and PT.     

Identification of surgically-induced longitudinal lesions of the equine deep digital flexor tendon in the digital flexor tendon sheath using contrast-enhanced ultrasonography: an <Emphasis Type="Italic">ex-vivo</Emphasis> pilot study

Background

Longitudinal tears in the lateral aspect of the deep digital flexor tendon are the most common causes of pain localised to the equine digital flexor tendon sheath. However conventional ultrasonographic techniques provide limited information about acute lesions. Ultrasonographic contrast agents are newly developed materials that have contributed to advancement in human diagnostic imaging. They are currently approved for intravenous use in human and animal models. In this study we described intrathecal use in the horse. This study was undertaken to evaluate the reliability of standard and angle contrast-enhanced ultrasonography to detect and characterize surgically-induced longitudinal lesions in the deep digital flexor tendons.In this pilot study surgically-induced lesions were created in the lateral aspect of the deep digital flexor tendon within the digital flexor tendon sheath in 10 isolated equine limbs to generate a replicable model for naturally occurring lesions. Another 10 specimens were sham operated. All the limbs were examined ultrasonographically before and shortly after the intrasynovial injection of an ultrasound contrast agent containing stabilised microbubbles. The images were blindly evaluated to detect the ability to identify surgically-created lesions. The deep digital flexor tendons were dissected and a series of slices were obtained. The depth of longitudinal defects identified with contrast-enhanced ultrasound scans was compared to the real extent of the lesions measured in the corresponding gross tendon sections.

Results

Contrast-enhanced ultrasonography with both angle and standard approach provided a significant higher proportion of correct diagnoses compared to standard and angle contrast ultrasonography (p < 0.01). Contrast-enhanced ultrasonography reliably estimated the depth of surgically-induced longitudinal lesions in the deep digital flexor tendons.

Conclusion

Contrast-enhanced ultrasound of the digital flexor tendon sheath could be an effective tool to detect intrasynovial longitudinal tears of the deep digital flexor tendon, although an in vivo study is required to confirm these results for naturally occurring lesions.