Healthy Tendon Research Articles

Validation of grayscale-based quantitative ultrasound in manual wheelchair users: relationship to established clinical measures of shoulder pathology.

The primary aim of this study is to establish the validity of grayscale-based quantitative ultrasound (QUS) measures of the biceps and supraspinatus tendons. Nine QUS measures of the biceps and supraspinatus tendons were computed from ultrasound images collected from 67 manual wheelchair users. Shoulder pathology was measured using questionnaires, physical examination maneuvers, and a clinical ultrasound grading scale. Increased age, duration of wheelchair use, and body mass correlated with a darker and more homogenous tendon appearance. Subjects with pain during physical examination tests for biceps tenderness and acromioclavicular joint tenderness exhibited significantly different supraspinatus QUS values. Even when controlling for tendon depth, QUS measures of the biceps tendon differed significantly between subjects with healthy tendons, mild tendinosis, and severe tendinosis. Clinical grading of supraspinatus tendon health was correlated with QUS measures of the supraspinatus tendon. QUS is valid method to quantify tendinopathy and may allow for early detection of tendinosis. Manual wheelchair users are at a high risk for developing shoulder tendon pathology and may benefit from QUS-based research that focuses on identifying interventions designed to reduce this risk.

Variant of the extensor pollicis tertius: a case report on a unique extensor muscle to the thumb

Variations on muscular and tendinous connections of the hand occur frequently in the human population and are often discovered during routine surgical procedures and cadaveric dissections. A knowledge of such anomalies is important to the physician in order to avoid unintentional damage to healthy tendons during surgical procedures. In addition, accessory tendons have the potential to be used in the repair or replacement of damaged tendons through surgical transfer or transplantation. Here we describe a unique variant of the extensor pollicis tertius muscle that has its origin at the proximal end of the extensor indicis muscle and inserts on the tendon of the extensor pollicis longus at the proximal shaft of the proximal phalanx of the thumb.

Sustained expression of proteoglycans and collagen type III/type I ratio in a calcified tendinopathy model

Alteration in the composition of extracellular matrix has been suggested as the major factor for the development of tendinopathy and calcified tendinopathy, which has poorer clinical manifestation. This study investigated the changes of major proteoglycans and collagens in a calcified tendinopathy model and correlated the expression with the acquisition of chondrocyte phenotype, ectopic ossification and loss of matrix organization in the same model. Thirty-six rats were used. Collagenase or saline was injected into the patellar tendons of each rat. At Weeks 2, 4 and 12, samples were used for immunohistochemistry of major proteoglycans and collagens and mRNA quantification. An increase in collagen type III and I expression was observed after injury at Week 2. Although their levels diminished with time, the ratio of collagen type III to collagen type I remained higher than that in healthy tendon at Week 12. The expression of biglycan, fibromodulin and aggrecan increased with time, whereas the expression of decorin was sustained from Week 2 to Week 12. The expression of major proteoglycans and collagens was observed in the tendon cells and matrix at Week 2 and became localized at the chondrocyte-like cells around the calcific deposits at Week 12. Sustained expression of proteoglycans and a high collagen type III/collagen type I ratio might account for poor matrix organization in calcified tendinopathy. The localization of major proteoglycans around chondro-osseous region might indicate interference of collagen assembly, which favours ectopic chondrogenesis, ossification and predisposition to tendon rupture.

The Use of a Dermal Substitute (Integra) to Preserve Maximal Foot Length in a Diabetic Foot Wound With Bone and Tendon Exposure Following Urgent Surgical Debridement for an Acute Infection

In this report, the authors present the case of a 62-year-old female patient who was admitted to our hospital with an acute deep foot infection. The patient was taken immediately to the operating room where she underwent surgical debridement to completely remove all infected tissues; at the end of this first surgical step, all 5 metatarsal bones remained exposed dorsally. Once eradication of infection was completed, we had to decide whether to perform a transmetatarsal amputation at proximal levels, which would have allowed healing by first intention but would have left the patient with a smaller foot stump, or amputation at more distal levels followed by coverage of healthy tendon and bone tissues with a dermal regeneration template (Integra, Integra Life Sciences Corporation, Plainsboro, NJ), which would have preserved the foot stump length and allowed better walking. We opted for the second choice, and the use of a dermal template actually enabled our patient to maintain a considerable foot stump length, much longer than would have resulted from an amputation with immediate primary closure.

Corticosteroid injections, eccentric decline squat training and heavy slow resistance training in patellar tendinopathy

A randomized-controlled single-blind trial was conducted to investigate the clinical, structural and functional effects of peritendinous corticosteroid injections (CORT), eccentric decline squat training (ECC) and heavy slow resistance training (HSR) in patellar tendinopathy. Thirty-nine male patients were randomized to CORT, ECC or HSR for 12 weeks. We assessed function and symptoms (VISA-p questionnaire), tendon pain during activity (VAS), treatment satisfaction, tendon swelling, tendon vascularization, tendon mechanical properties and collagen crosslink properties. Assessments were made at 0 weeks, 12 weeks and at follow-up (half-year). All groups improved in VISA-p and VAS from 0 to 12 weeks (P<0.05). VISA-p and VAS improvements were maintained at follow-up in ECC and HSR but deteriorated in CORT (P<0.05). In CORT and HSR, tendon swelling decreased (-13+/-9% and -12+/-13%, P<0.05) and so did vascularization (-52+/-49% and -45+/-23%, P<0.01) at 12 weeks. Tendon mechanical properties were similar in healthy and injured tendons and were unaffected by treatment. HSR yielded an elevated collagen network turnover. At the half-year follow-up, treatment satisfaction differed between groups, with HSR being most satisfied. Conclusively, CORT has good short-term but poor long-term clinical effects, in patellar tendinopathy. HSR has good short- and long-term clinical effects accompanied by pathology improvement and increased collagen turnover.

Microcirculatory effects of topical glyceryl trinitrate on the Achilles tendon microcirculation in patients with previous Achilles tendon rupture

Topical glyceryl trinitrate treatment has demonstrated short- to mid-term efficacy in chronic noninsertional Achilles tendinopathy. However, the underlying mechanisms are far from being understood. We hypothetized that Achilles tendon capillary blood flow changes immediately after topical glyceryl trinitrate treatment. Fifteen patients (55 + or - 15 years, VAS 5.8 + or - 2.3) with current mid-portion Achilles tendon pain 36 months after open surgical Achilles tendon repair for tendon rupture were included. On the Achilles mid-portion, 1.2 mg topical glyceryl trinitrate was sprayed. Microcirculatory monitoring included capillary blood flow, tendon oxygen saturation and postcapillary venous filling pressures at the insertion and 2, 4 and 6 cm above the insertion using a combined laser Doppler and spectrophotometry system. Baseline capillary blood-flows of the painful versus the uninjured tendon were increased [108 + or - 46 vs. 81 + or - 20 (2 cm above the insertion), 104 + or - 40 vs. 76 + or - 20 (4 cm above the insertion), 111 + or - 53 vs. 90 + or - 21 (6 cm above the insertion, P < 0.05)]. However, topical glyceryl trinitrate did not change capillary blood-flow at 2 and 8-mm tissue depths at the painful Achilles tendon or the healthy tendon. Tendon oxygenation was not changed at the painful or the healthy Achilles tendon. Postcapillary venous filling pressure was reduced at 8 mm at the mid-portion in the painful Achilles tendon only (113 + or - 37 vs. 95 + or - 31, P = 0.030). Acute topical glyceryl trinitrate facilitates capillary venous outflow in painful Achilles tendons. However, capillary blood-flow and tendon oxygenation remain unchanged following acute topical glyceryl trinitrate application. Elevated capillary blood-flow at the entire mid-portion is encountered at baseline in previously ruptured painful Achilles tendons even 3 years after surgical repair of the Achilles tendon indicating an altered microcirculatory flow pattern.

Corticosteroid administration alters the mechanical properties of isolated collagen fascicles in rat‐tail tendon

Overload tendon injuries are frequent in recreational and elite sports. The optimal treatment strategy remains unknown, but local administration of corticosteroids is one common treatment option. The direct effects of the corticosteroid administration on the tissue are not fully understood. The present study examined the biomechanical effects of intratendinous corticosteroid injections on healthy rat-tail tendon collagen fascicles. A total of 24 Wistar male rats were divided into (A) a corticosteroid group where the animals were injected in the tail tendon with methylprednisolone acetate, 1.0 mL of 40 mg/mL mixed with 1.0 mL 9% saline (n=12), and (B) a control group that was injected with 9% saline (n=12). Three days after the injections, the animals were sacrificed and single individual collagen fascicles were collected and underwent displacement to failure. Corticosteroid administration significantly reduced tensile fascicle yield strength by 16% and Young's modulus by 14% compared with sham treatment (10.5+/-0.8 vs 12.4+/-0.5 MPa, P< or =0.05, and 537+/-27 vs 641+/-30 MPa, P<0.05, respectively), while the strain properties were unaffected. Peak stress was similar between the two groups. There was no difference in fascicle diameter between the two groups.

Real-Time Sonoelastography of Lateral Epicondylitis: Comparison of Findings Between Patients and Healthy Volunteers

The purpose of this study was to evaluate real-time sonoelastography in the assessment of the origins the common extensor tendon in healthy volunteers and in patients with symptoms of lateral epicondylitis. The findings were compared with those obtained at clinical examination, ultrasonography, and power Doppler sonography. Thirty-eight elbows of 32 consecutively registered patients with symptoms of lateral epicondylitis and 44 asymptomatic elbows of 28 healthy volunteers were assessed with ultrasound and real-time sonoelastography. A clinical examination was performed, and pain was classified with a visual analog scale. In healthy volunteers, real-time sonoelastographic images showed hard tendon structures in 96% of tendon thirds and mild alterations in 4%. Real-time sonoelastography of patients showed hard structures in 33% of tendon thirds but softening of different grades in 67%, a statistically significant difference in relation to the findings in healthy volunteers (p < 0.001). Lateral collateral ligament involvement and overlying fascial involvement were more commonly detected with real-time sonoelastography. The sensitivity of real-time sonoelastography was 100%, the specificity 89%, and the accuracy 94% with clinical examination as the reference standard. Good correlation with ultrasound findings was found (r > or = 0.900). No correlation was observed between ultrasound or real-time sonoelastographic findings and power Doppler sonographic findings, but power Doppler sonographic findings had a strong correlation with the visual analog scale score. Real-time sonoelastography is valuable in the detection of the intratendinous and peritendinous alterations of lateral epicondylitis and facilitates differentiation between healthy and symptomatic extensor tendon origins with excellent sensitivity and excellent correlation with ultrasound findings.

Organization of collagen bundles during tendon healing in rats treated with L-NAME

The Achilles tendon can support high tension forces and may experience lesions. The damaged tissue does not regenerate completely, with the organization and mechanical properties of the repaired tendon being inferior to those of a healthy tendon. Nitric oxide (NO) plays an important role in wound repair. We have examined the structural reorganization and repair in Achilles tendon after injury in rats treated with the NO synthase inhibitor L-NAME. The right Achilles tendon of male Wistar rats was partially transected. One group of rats was treated with L-NAME (~300 mg/kg per day, given in drinking water) for 4 days prior to tendon sectioning and throughout the post-operative period. Control rats received water without L-NAME. The tendons were excised at 7, 14, and 21 days post-injury and used to quantify hydroxyproline and for mechanical tests. Tendons were also processed for histomorphological analysis by polarized light microscopy, which showed that the collagen fibers were disorganized by day 7 in non-treated and L-NAME-treated rats. In non-treated rats, the organization of the extracellular matrix was more homogeneous by days 14 and 21 compared with day 7, although this homogeneity was less than that in normal tendon. In contrast, in injured tendons from L-NAME-treated rats, the collagen fibers were still disorganized on day 21. Tendons from treated rats had more hydroxyproline but lower mechanical properties compared with those from non-treated rats. Thus, NO modulates tendon healing, with a reduction in NO biosynthesis delaying reorganization of the extracellular matrix, especially collagen.

Noninvasive 64Cu-ATSM and PET/CT Assessment of Hypoxia in Rat Skeletal Muscles and Tendons During Muscle Contractions

The purpose of the present study was to investigate exercise-related changes in oxygenation in rat skeletal muscles and tendons noninvasively with PET/CT and the hypoxia-selective tracer (64)Cu-diacetyl bis(N(4)-methylthiosemicarbazone) (ATSM) and to quantitatively study concomitant changes in gene expression of 2 hypoxia-related genes, hypoxia-inducible factor 1alpha (HIF1alpha) and carbonic anhydrase III (CAIII). Two groups of Wistar rats performed 1-leg contractions of the calf muscle by electrostimulation of the sciatic nerve. After 10 min of muscle contractions, (64)Cu-ATSM was injected and contractions were continued for 20 min. PET/CT of both hind limbs was performed immediately and 1 h after the contractions. The exercise group (n = 8) performed only muscle contractions as described, whereas the other group, exercise plus cuff (n = 8), in addition underwent cuff-induced hypoxia during the first PET/CT scan. Standardized uptake values (SUVs) were calculated for the Achilles tendons and triceps surae muscles and were correlated to gene expression of HIF1alpha and CAIII using real-time polymerase chain reaction. Immediately after the contractions, uptake of (64)Cu-ATSM was significantly increased, by approximately 1.5-fold in muscles and 1.3-fold in tendons, compared with resting conditions. The significant increase was maintained in late PET scans in stimulated muscles and tendons independently of cuff application. In muscles, SUV correlated significantly with gene expression of HIF1alpha and CAIII, whereas this coherence was not found in tendons. We found enhanced uptake of (64)Cu-ATSM in both early and late PET scans, thereby supporting the possibility that (64)Cu-ATSM registers exercise-induced transient hypoxia in both skeletal muscles and force-transmitting tendons. The fact that skeletal muscles but not tendons showed upregulation of HIF1alpha and CAIII could indicate that healthy tendons are less responsive than skeletal muscles to low levels of oxygen.

Fibril Morphology And Tendon Mechanical Properties In Patellar Tendinopathy - Effects Of Heavy Slow Resistance Training.

Patellar tendinopathy (PT) is a prevalent and disabling overload injury that is associated with cellular and extracellular matrix changes. However, how the specific structural and functional properties of the tensile bearing components of tendons are affected by tendinopathy remain elusive. We recently showed that heavy slow resistance training (HSR) is effective in the management of PT, but the underlying mechanisms remain to be established. PURPOSE: To investigate the effect of HSR on patellar tendon fibril morphology and whole tendon mechanical properties in persons with PT. METHODS: Eight male PT patients completed 12 wks of HSR. Healthy patellar tendons from nine matched subjects served as controls. Subjects were examined at 0 and 12 wks. PT patients assessed symptoms and function (VISA-p questionnaire) and indicated maximal tendon pain during activity (VAS). Patellar tendon biopsies were obtained and subsequently analyzed for fibril density, volume-fraction and fibril mean-area using stereological techniques of digitized electron microscopy biopsy cross-sections. Patellar tendon mechanical properties were assessed using simultaneous force and ultrasonography samplings. RESULTS: PT patients improved both in VISA-p (wk 0: 57+3, wk 12: 72+7), and VAS (wk 0: 59+6, wk 12: 23+5), p<0.05. There were no differences in tendon mechanical properties between control and tendinopathy tendons at baseline. Tendon mechanical properties (stiffness and modulus) remained unaffected in control tendons, but declined in tendinopathy tendons with HRS (-9+6 & and -13+8%, p<0.05). At baseline, fibril volume fraction was equal, the fibril density smaller (p<0.05) and the fibril mean-area tended to be higher (p=0.07) in tendinopathy compared to control tendons. Fibril morphology parameters remained unchanged in control tendons but fibril density increased (70+18%, p<0.01) and fibril mean-area decreased (-26+21%, p<0.05) in tendinopathy tendons following HSR. CONCLUSION: Whole tendon mechanical properties are unaffected by tendinopathy but fibril morphology differ in healthy vs. tendinopathy tendons. Clinical improvements in PT following HSR were associated with changes in fibril morphology possibly related to increased turnover of the collagen matrix.

In Vitro Model to Study Chondrogenic Differentiation in Tendinopathy

Background Treatment of midportion Achilles tendinopathy is hampered by limited knowledge of the pathophysiology. Hypothesis Chondrogenic differentiation of tendon cells might take place in midportion Achilles tendinopathy and could be used as a target for drug treatment. An in vitro model for chondrogenic differentiation would be useful to evaluate existing and future treatment opportunities. Study Design Descriptive and controlled laboratory study. Methods Perioperatively harvested tissue from human midportion Achilles tendinotic lesions and healthy Achilles tendons was analyzed by microscopy and real-time reverse transcription polymerase chain reaction. In vitro chondrogenic differentiation of tendon explants was induced using transforming-growth-factor beta. This model was modulated by removing the chondrogenic stimulus or adding triamcinolone or platelet-rich plasma. Results Midportion Achilles tendinotic lesions had increased glycosaminoglycan staining and more rounded cell nuclei. Chondrogenic markers (sex-determining region Y)–box9, aggrecan, collagen 2, and RUNT-related transcription factor 2 were upregulated, but collagen 10 was not. Nondegenerative tendon explants cultured on chondrogenic medium had higher expression of aggrecan, collagen 2, and collagen 10 but not (sex-determining region Y)–box9 and RUNT-related transcription factor 2. Removing the chondrogenic stimulus decreased expression of aggrecan, collagen 2, and collagen 10. Both triamcinolone and platelet-rich plasma influenced the chondrogenic gene expression pattern in the in vitro model. Conclusion Chondrogenic differentiation is present in midportion Achilles tendinopathy. An in vitro model to study this chondrogenic differentiation was developed. Clinical Relevance This model can be used to investigate chondrogenic differentiation as a possible target for drug treatment, contributing to the development of more successful mechanism-based treatment opportunities.

Tendon degeneration is not mediated by regulation of Toll‐like receptors 2 and 4 in human tenocytes

We hypothesized that expression of Toll-like receptors (TLRs) 2 and 4 by tenocytes is involved in the catabolic processes of tendon degeneration. We investigated TLR2 and TLR4 expression by tenocytes in healthy and tendinotic Achilles tendons. We also investigated whether TLR2 and TLR4 could be upregulated in tendon explants using proinflammatory cytokines interleukin (IL)-1beta and tumor necrosis factor alphpa (TNFalpha). Peroperatively harvested healthy (n = 5) and tendinotic (n = 13) Achilles tendon samples were examined by real-time RT-PCR and immunohistochemical staining for TLR2 and TLR4. In addition, the catabolic process in tendinopathy was analyzed by real-time RT-PCR for matrix metalloproteinases MMP1, MMP3, MMP9, and MMP13. Furthermore, healthy tendon explants were cultured in the presence of 20 ng/ml IL-1beta (n = 10) or 10 ng/mL TNFalpha (n = 8) for 4, 24, 48, and 72 h before analysis of TLR and MMP expression levels. Although mRNA levels for both TLR2 and TLR4 were detected in healthy and tendinotic Achilles tendons, we could not confirm expression of these receptors by immunohistochemical staining in either healthy or tendinotic tendon samples. Both receptors did not show significant transcriptional regulation in tendinopathy, although MMP3 was downregulated and MMP9 was upregulated in tendinopathy. In tendon explant cultures TLR2 mRNA was upregulated by TNFalpha (p < 0.05) and IL-1beta (not significant). TLR4 gene expression was not altered by addition of IL-1beta or TNFalpha. Tendon tissue can be stimulated to increase TLR2 gene expression by addition of catabolic factors TNFalpha or IL-1beta. However, the catabolic processes in Achilles tendinopathy cannot be attributed to regulation of TLR2 and TLR4 by tenocytes.

Neuronal pathways in tendon healing

The regulatory mechanisms involved in tendon homeostasis and repair are not fully understood. Accumulating data, however, demonstrate that the nervous system, in addition to afferent (sensory) functions, through efferent neuronal pathways plays an active role in regulating pain, inflammation, and tissue repair processes. Thus, in normal-, healing- and tendinopathic tendons three major neuronal signalling pathways consisting of autonomic, sensory and glutamatergic neuromediators have been established. In healthy tendons, these neural elements are found in the paratenon, whereas the proper tendon is practically devoid of nerves, reflecting that normally tendon homeostasis is regulated by pro- and anti-inflammatory mediators from the tendon surroundings. During tendon repair, however, there is extensive nerve ingrowth into the tendon proper and subsequent time-dependent appearance of sensory, autonomic and glutamatergic mediators, which amplify and fine-tune inflammation and tendon regeneration. In tendinopathy excessive and protracted sensory and glutamatergic signalling may be involved in inflammatory, painful and hypertrophic tissue reactions. In a future perspective, neuronal mediators may prove to be useful in targeted pharmacotherapy and tissue engineering in painful, degenerative and traumatic tendon disorders.

The effect of glucocorticoids on tendon cell viability in human tendon explants

Background and purpose Previous studies on the culture of human tenocytes have shown that dexamethasone and triamcino-lone reduce cell viability, suppress cell proliferation, and reduce collagen synthesis. However, such cell cultures lack the extracellular matrix and three-dimensional structure of normal tendons, which affects their response to stimuli. We established a human tendon explant culture system and tested the effects of dexamethasone and triamcinolone on cell viability.Methods Primary human tendon explant cultures were prepared from healthy hamstring tendons. Tendon strips were harvested from hamstring tendons and cultured in 24-well plates in Dulbecco’s modification of Eagle’s Medium (DMEM) supplemented with 2% fetal calf serum. The tendon explants were treated with 0 μM (control), 10 μM, or 100 μM dexamethasone sodium phosphate or 0 μM (control), 10 μM, or 100 μM triamcinolone acetonide in DMEM for 96 h. Cell viability was measured by Alamar blue assay before and after glucocorticoid treatment.Results Incubation with 10 μM and 100 μM dexamethasone reduced cell viability in human tendon explants by 35% and 45%, respectively, as compared to a 6% increase in the controls (p = 0.01, mixed-effects ANOVA). Triamcinolone at 10 μM and 100 μM reduced cell viability by 33% and 36%, respectively, as compared to a 9% increase in the controls (p = 0.07, mixed-effects ANOVA).Interpretation Human tendon explant cultures can be used to study the effects of glucocorticoids on human tendon. Dexamethasone and triamcinolone suppress the cell viability of human tendon in its natural 3-dimensional environment with matrix anchorage. Human tendon explant cultures provide a species-specific model for further investigation of the effects of glucocorticoids on the metabolism of the extracellular matrix of human tendon, and on its mechanical properties.

Peritendinous Corticosteroid Injections, Eccentric Decline Squat Training And Heavy Slow Resistance Training In Patellar Tendinopathy

Patellar tendinopathy (PT) is a very frequent, persistent and disabling overload injury among jumping athletes. Tendinopathy is associated with tendon degeneration. No treatment of choice has been established for PT and comparative studies are scares. The underlying mechanisms of treatments in PT are highly unidentified. PURPOSE: Investigate the clinical, structural and tendon mechanical effects of three conservative treatments in PT. METHODS: 39 male PT patients were randomly allocated to 12 wks treatment consisting of either: 1) Peritendinous corticosteroid injections (CORT), 2) Eccentric decline unilateral squat training (ECC) or 3) Heavy slow resistance training (HSR). Subjects were examined at 0 wks, 12 wks and at half-year follow-up. Subjects indicated maximal tendon pain during activity on a VAS-scale and assessed symptoms and function in a VISA-p questionnaire. Subjects reported treatment satisfaction as "satisfied" or "not satisfied". Tendon swelling and vascularisation was assessed by ultrasound and Colour Doppler. Structural properties were assessed by MRI. Patellar tendon mechanical properties were assessed using simultaneous force and ultrasonography samplings. RESULTS: No differences existed between groups at 0 wks. All groups improved equally in VISA-p and VAS from 0 to 12 wks (p < 0.05). The VISA-p and VAS improvements were maintained at half-year follow-up in ECC and HSR but deteriorated in CORT (p<0.05). Tendon swelling decreased in CORT and HSR (13 + 2 & 12 + 2%, p < 0.05) but was unchanged in ECC. Vascularisation decreased in CORT and HSR (52 + 14 & 45 + 6%, p < 0.01) but was unchanged in ECC. Quadriceps cross sectional area increased in ECC and HSR (7 + 2 & 7 + 1%, p < 0.01) but was unchanged in CORT. At half-year follow up HSR were more satisfied than CORT and ECC. Patellar tendon mechanical properties did not differ in healthy and injured tendons and remained unchanged in all three groups. CONCLUSIONS: CORT had excellent short term, but poor long-term, clinical effects. HSR seems to have somewhat superior short and long-term effects. The mechanical properties of the patellar tendon are not affected by tendinopathy and do not change with either treatments.

Tendinopathy Discrimination by Use of Spatial Frequency Parameters in Ultrasound B-Mode Images

The structural characteristics of a healthy tendon are related to the anisotropic speckle patterns observed in ultrasonic images. This speckle orientation is disrupted upon damage to the tendon structure as observed in patients with tendinopathy. Quantification of the structural appearance of tendon shows promise in creating a tool for diagnosing, prognosing, or measuring changes in tendon organization over time. The current work describes a first step taken towards this goal-classification of Achilles tendon images into tendinopathy and control categories. Eight spatial frequency parameters were extracted from regions of interest on tendon images, filtered and classified using linear discriminant analysis. Resulting algorithms had better than 80% accuracy in categorizing tendon image kernels as tendinopathy or control. Tendon images categorized wrongly provided for an interesting clinical association between incorrect classification of tendinopathy kernels as control and the symptom and clinical time history based inclusion criteria. To assess intersession reliability of image acquisition, the first 10 subjects were imaged twice during separate sessions. Test-retest of repeated measures was excellent (tau = 0.996, ICC = (2, 1) = 0.73 with one outlier) indicating a general consistency in imaging techniques.

Achilles Tendinosis

Background Understanding biochemical and structural changes of the extracellular matrix in Achilles tendinosis might be important for developing mechanism-based therapies. Hypothesis In Achilles tendinosis, changes occur in biochemical composition and collagen turnover rate. Study Design Descriptive laboratory study. Methods From 10 patients undergoing surgery for Achilles tendinopathy, 1 tendinosis biopsy specimen and 1 biopsy specimen of macroscopically healthy tendon tissue adjacent to the lesion were collected. Furthermore, biopsy samples were collected from 3 donors with asymptomatic Achilles tendons. Water content, collagen content, percentage of denatured collagen, amount of lysine hydroxylation, number of enzymatic and nonenzymatic crosslinks, matrix metalloproteinase activity, and matrix metalloproteinase and collagen gene-expression levels were analyzed. Results In tendinotic lesions, the water content was highest, and collagen content was subnormal with higher amounts of denatured/damaged collagen. Low pentosidine levels in tendinotic tissue indicated the presence of relatively young collagenous matrix. More hydroxylated lysine residues were present in tendinotic samples, but enzymatic crosslinks revealed no differences between tendinotic, adjacent, and healthy samples. In tendinotic specimens, matrix metalloproteinase activity was higher, matrix metalloproteinase gene-expression profile was altered, and collagen type I and III gene expression were upregulated. Conclusion In Achilles tendinosis, the collagen turnover rate is increased, and the natural biochemical composition of the collagenous matrix is compromised. Clinical Relevance Although tendon tissue directly adjacent to an Achilles tendinosis lesion looks macroscopically healthy, histological and biochemical degenerative changes in adjacent tissue are evident, which may have implications for surgical interventions.

Preventive effects of a turnover flexor tendon sheath flap on adhesion formation after flexor profundus tendon injury: an experimental study

This study aims to investigate the effects of a proximally-based turnover sheath flap obtained from the tendon sheath on the prevention of adhesion formation in the legs of the chickens whose tendons and sheaths have been injured. The chickens were categorised into 4 groups. Group 1 was chosen as the sham group. In Group 2, a defective area of 0.3 x0.5 cm was created across the sheath, without damaging the tendon. The healthy profundus tendons of the chickens in Group 3 were cut and repaired. Afterwards, a defective area of 0.3 x 0.5 cm was created across the tendon sheath. In Group 4, the healthy profundus tendons were cut and repaired. Then, a defective area of 0.3 x 0.5 cm was created over the reconstructed tendon. This defective area was finally covered with a proximally-based turnover sheath flap of the size 0.4 x 1 cm, which was raised from the distal part of the sheath. The toes were immobilised for 3 weeks before the chickens were sacrificed. Histopathological and biomechanical analyses showed adhesion in the repaired tendons in Group 3, in which movement restriction was shown by biomechanical analyses. The present study showed that covering the defective sheath that was created over the repaired tendon with a proximally-based turnover tendon sheath flap prevented peritendinous adhesion.

Tissue engineering of tendons and ligaments by human bone marrow stromal cells in a liquid fibrin matrix in immunodeficient rats: Results of a histologic study

The original complex structure and mechanical properties are not fully restored after ligament and tendon injuries. Due to their high proliferation rate and differentiation potential, Bone Marrow Stromal Cells (BMSC) are considered to be an ideal cell source for tissue engineering to optimize the healing process. Ideal matrices for tissue engineering of ligaments and tendons should allow for homogenous cell seeding and offer sufficient stability. A mixture of human BMSC and liquid fibrin glue was injected into a standardized full-thickness window defect of the patellar tendon of immunodeficient rats (BMSC group). The histology of the tissue was analysed 10 and 20 days postoperatively and compared to four control groups. These groups consisted of a cohort with a mixture of human fibroblasts and fibrin glue, fibrin glue without cells, a defect group without treatment, and a group with uninjured patellar tendon tissue. Tendon defects in the BMSC group revealed dense collagen fibres and spindle-shaped cells, which were mainly orientated along the loading axis. Histologic sections of the control groups, especially of untreated defects and of defects filled with fibrin glue only, showed irregular patterns of cell distribution, irregular formed cell nucleoli and less tissue maturation. Compared to healthy tendon tissue, higher numbers of cells and less intense matrix staining was observed in the BMSC group. No ectopic bone or cartilage formation was observed in any specimen. Injection of human BMSC in a fibrin glue matrix appears to lead to more mature tissue formation with more regular patterns of cell distribution. Advantages of this "in-vivo" tissue engineering approach are a homogenous cell-matrix mixture in a well-known and approved biological matrix, and simple, minimally-invasive application by injection.