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PubMed2005

Stress deprivation simultaneously induces over-expression of interleukin-1beta, tumor necrosis factor-alpha, and transforming growth factor-beta in fibroblasts and mechanical deterioration of the tissue in the patellar tendon.

To test the hypothesis that stress deprivation induces over-expression of cytokines in the patellar tendon, 40 rats were divided into the following two groups. In the stress-shielded group, we slackened the patellar tendon in the right knee by drawing the patella toward the tibial tubercle with flexible wires. In the control group, we performed a sham operation on the right knee. Animals were killed at 2 or 6 weeks for immunohistological evaluation and biomechanical examination. For IL-1beta, TNF-alpha and TGF-beta, the ratio of positively stained specimens to total specimens was significantly higher in the stress-shielded tendons than in the control tendons. The elastic modulus of the stress-shielded tendon was significantly lower than that of the control tendon, while the cross-sectional area of the stress-shielded tendon was significantly greater than that of the control tendon. Therefore, the present study indicated that stress shielding induced the over-expression of IL-1beta, TNF-alpha and TGF-beta in patellar tendon fibroblasts with mechanical deterioration of the tendon. Regarding clinical relevance, the present study suggests a possible application of an anti-IL-1beta or anti-TNF-alpha strategy for reducing the mechanical deterioration of tendons and ligaments in response to stress deprivation, although this study did not directly show that over-expression of IL-1beta or TNF-alpha in response to stress deprivation was the causation of mechanical deterioration of tendons.

Animals↗
PubMed2005

Inhomogeneous mechanical behavior of the human supraspinatus tendon under uniaxial loading.

Disorders of the rotator cuff, particularly tears of the rotator cuff tendons, cause significant shoulder disability. Among numerous factors thought to be responsible for the initiation and progression of supraspinatus tears are those related to the tendon's biomechanical properties. We hypothesized that in supraspinatus tendons subjected to tensile loading a strain gradient (difference) exists between the articular and bursal tendon surfaces, that regional strain differences exist on each of these two tendon surfaces, and that tendon surface strains vary with glenohumeral abduction. To test these hypotheses, the intrinsic inhomogeneous deformational characteristics of the articular and bursal surfaces of eight intact human cadaveric supraspinatus tendons were studied at three glenohumeral abduction angles using a novel multiple strain measuring system which simultaneously recorded surface marker displacements on two opposing soft tissue surfaces. Under applied tensile loads, the articular surface exhibited greater strain at 22 degrees (7.4+/-2.6% vs. 1.3+/-0.7%, p=0.0002) and 63 degrees (6.4+/-1.6% vs. 2.7+/-1.2%, p=0.0001) whereas the bursal surface exhibited greater strain at 90 degrees (7.6+/-2.8% vs. 4.9+/-0.4%, p=0.013). At all abduction angles, insertion strains were higher than those of the mid-tendon and tendon-muscle junction regions. The existence of inhomogeneous surface strains in the intact supraspinatus tendon demonstrates that intratendinous shear occurs within the tendon. The higher strain on the articular side of the tendon, especially at the insertion region, suggests a propensity for tears to initiate in the articular tendinous zone.

Adult↗
PubMed2000

The bursal and articular sides of the supraspinatus tendon have a different compressive stiffness.

OBJECTIVE: To measure the compressive stiffness of the supraspinatus tendon and to determine whether regional difference exists in the bursal and articular side of the tendon. DESIGN: Indentation testing was performed on both the bursal and articular sides of the supraspinatus tendon, focused on the 'critical area', where rotator cuff tears often occur. BACKGROUND: When the supraspinatus tendon wraps around the humeral head or is under impingement condition, compressive force on the tendon surface is expected. Therefore, compressive stress has been recently considered to be one of the important factors associated with the cuff tear. The mechanical properties would be essential for analytic modeling of stress distribution. METHODS: Indentation tests were performed at 15 locations on the bursal and articular surfaces of the supraspinatus tendon. A mathematical model with exponential relationship was used to describe the measured force-deformation relationship and to calculate the compressive stiffness of the supraspinatus tendon. RESULTS: The over-all initial stiffness on the bursal and articular sides of the tendon was significantly different. On the bursal side, the anterior third had a significantly higher initial stiffness than the other thirds on average. On the articular side, initial stiffness at location 10 mm proximal to the greater tuberosity was significantly higher than the rest on average. CONCLUSIONS: The compressive stiffness of the supraspinatus tendon was found to be non-homogenous throughout the structure.RelevanceNon-homogenous compressive stiffness of the supraspinatus tendon would affect the load transmission within the tendon, which might be associated with the potential mechanism of tear. Such characteristics needs to be considered when performing finite element modeling of stress fields in the tendon.

Aged↗
PubMed2003

Sonographic evaluation of the size of Achilles tendon: the effect of exercise and dominance of the ankle.

This study was undertaken to measure and compare the thickness and cross-sectional area of the Achilles tendon between frequent- and infrequent-exercise subjects, and between the dominant and nondominant ankles in an asymptomatic Chinese population. Interobserver variability in the measurement of the size of Achilles tendon was also evaluated. High-resolution ultrasound (US) examination of Achilles tendons was performed in 40 healthy subjects (20 who frequently exercised, had exercise at least 3 days per week and at least 2 h per session; and 20 who infrequently exercised); their age range was 19 to 25 years. The thickness and cross-sectional area of the Achilles tendons were measured in a transverse scan at the level of medial malleolus. For each subject, the Achilles tendons were measured by five operators to evaluate the interobserver variability in the measurements. The mean thickness and cross-sectional areas of the Achilles tendon in a healthy Chinese population are 5.23 mm(2) and 56.91 mm(2)(2), respectively. The mean thickness of the Achilles tendon of frequent-exercise subjects (dominant ankle 5.43 mm, nondominant ankle 5.38 mm) was significantly greater than that of infrequent-exercise subjects (dominant ankle 5.08 mm, nondominant ankle 5.04 mm) (p < 0.05). The cross-sectional area of the tendons was also larger in frequent-exercise subjects but, whereas a significant result was found in dominant ankles (frequent-exercise subjects 60.46 mm(2)(2), infrequent-exercise subjects 54.71 mm(2)(2)) (p < 0.05), this was not the case for the nondominant ankles (frequent-exercise subjects 57.09 mm(2)(2), infrequent-exercise subjects 55.4 mm(2)(2)) (p > 0.05). In both frequent- and infrequent-exercise subjects, there was no significant difference in the mean thickness and cross-sectional area of Achilles tendon between dominant and nondominant ankles (p > 0.05). There was a high reproducibility in the sonographic measurement of the thickness (68%) and cross-sectional area (81%) of Achilles tendons. Results suggested that exercise would cause increase in the thickness and cross-sectional area of Achilles tendon. Interobserver variability is not significant in the sonographic measurement of Achilles tendons.

Achilles Tendon↗
PubMed2003

Mechanical factors influence the expression of endostatin--an inhibitor of angiogenesis--in tendons.

Avascular zones of tendons are predisposed for degenerative changes and spontaneous rupture. Therefore, we analyzed the expression of the endogenous angiogenesis inhibiting factor endostatin in human fetal and adult tendons by immunohistochemical and biochemical methods. Moreover, to elucidate factors involved in the regulation of vascularity, we exposed primary cultures of rat tendon cells to intermittent hydrostatic pressure (0.2 MPa, 0.1 Hz for 24 h), and measured the endostatin content by ELISA and the effect of the conditioned medium to the proliferation of human umbilical vein endothelial cells (HUVEC). In fetal tendons high endostatin levels could be quantified by ELISA whereas low levels were found in adult tissue. In fetal tendons endostatin could also be immunostained in endothelial cells but mainly in fibroblasts. In adult Achilles tendons endostatin immunostaining was restricted to endothelial cells. In the tibialis posterior tendon--as an example for "wrap around"--endostatin immunostaining remained positive in the fibrocartilage adjacent to the medial malleolus. Fibrochondrocytes of the type II collagen positive fibrocartilage were intensively stained with the endostatin antibody. Factor VIII immunostaining showed that this region was largely avascular. Monolayer cultures of tendon cells released measurable amounts of endostatin into their culture supernatants. Application of intermittent hydrostatic pressure increased endostatin expression significantly. The conditioned media of tendon fibroblasts cultivated under intermittent hydrostatic pressure inhibited the proliferation of HUVEC in a dose dependent way. The spatial expression of endostatin in adult gliding tendons suggests that mechanical factors are involved in the regulation of this anti-angiogenic factor. In accordance, tendon cells exposed to intermittent hydrostatic pressure inhibit endothelial cell proliferation via humoral factors and produce endostatin. These findings support the view that the development and maintenance of avascular zones in tendons might be caused by a mechanically induced upregulation of anti-angiogenic factors.

Achilles Tendon↗
PubMed1998

Humeral attachment of the supraspinatus and infraspinatus tendons: an anatomic study.

We investigated the anatomic relationship of the supraspinatus (SSP) and infraspinatus (ISP) tendons to the three facets of the greater tuberosity. After removing the superficial layer of the cuff to expose the tendon fibers in 10 embalmed shoulders, the cuff tendon attachment to the facets was examined, and the location of attachment was measured in reference to (1) the anterior margin of the greater tuberosity and (2) the superior margin of the sulcus (anatomic neck without cartilage). The SSP tendon attached to the superior facet and the superior half of the middle facet. The ISP tendon attached to the entire middle facet, covering a portion of the SSP tendon. Thus, the anterior half of the superior cuff tendon (12.6 +/- 1.1 mm) was composed of only the SSP tendon, whereas the posterior half (9.8 +/- 3.2 mm) was composed of both the SSP and ISP tendons. The sulcus was located not at the SSP-ISP interval but slightly posterior to the posterior margin of the SSP tendon (4.3 +/- 2.4 mm). We conclude that (1) there is an overlap between the SSP and ISP tendons identifiable by the facets or the distance from the anterior greater tuberosity and (2) the sulcus is located slightly posterior to the posterior margin of the SSP tendon.

Aged↗
PubMed2002

Structure and function of tuna tail tendons.

The caudal tendons in tunas and other scombrid fish link myotomal muscle directly to the caudal fin rays, and thus serve to transfer muscle power to the hydrofoil-like tail during swimming. These robust collagenous tendons have structural and mechanical similarity to tendons found in other vertebrates, notably the leg tendons of terrestrial mammals. Biochemical studies indicate that tuna tendon collagen is composed of the (alpha1)(2),alpha2 heterotrimer that is typical of vertebrate Type I collagen, while tuna skin collagen has the unusual alpha1,alpha2,alpha3 trimer previously described in the skin of some other teleost species. Tuna collagen, like that of other fish, has high solubility due to the presence of an acid-labile intermolecular cross-link. Unlike collagen in mammalian tendons, no differences related to cross-link maturation were detected among tendons in tuna ranging from 0.05 to 72 kg (approx. 0.25-6 years). Tendons excised post-mortem were subjected to load cycling to determine the modulus of elasticity and resilience (mean of 1.3 GPa and 90%, respectively). These material properties compare closely to those of leg tendons from adult mammals that can function as effective biological springs in terrestrial locomotion, but the breaking strength is substantially lower. Peak tendon forces recorded during steady swimming appear to impose strains of much less than 1% of tendon length, and no more than 1.5% during bursts. Thus, the caudal tendons in tunas do not appear to function as elastic storage elements, even at maximal swimming effort.

Aging↗
PubMed2000

The role of mineral in the storage of elastic energy in turkey tendons.

Mammals elastically store energy in leg and foot tendons during locomotion. In the turkey, much of the force generated by the gastrocnemius muscle is stored as elastic energy during tendon deformation and not within the muscle. During growth, avian tendons mineralize in the portions distal to the muscle and show increased tensile strength and modulus as a result. The purpose of this study was to evaluate the viscoelastic behavior of turkey tendons and self-assembled collagen fiber models to determine the molecular basis for tendon deformation. The stress-strain behavior of tendons and self-assembled collagen fibers was broken into elastic and viscous components. The elastic component was found to be to a first approximation independent of source of the collagen and to depend only on the extent of cross-linking. In the absence of cross-links the elastic component of the stress was found to be negligible for self-assembled type I collagen fibers. In the presence of cross-links the behavior approached that found for mineralized turkey tendons. The elastic constant for turkey tendon was shown to be between 5 and 7.75 GPa while it was about 6.43 GPa for self-assembled collagen fibers aged for 6 months at 22 degrees C. The viscous component for mineralized turkey tendons was about the same as that of self-assembled collagen fibers aged for 6 months, a result suggesting that addition of mineral does not alter the viscous properties of tendon. It is concluded that elastic energy storage in tendons involves direct stretching of the collagen triple-helix, nonhelical ends, and cross-links between the molecules and is unaffected by mineralization. Furthermore, it is hypothesized that mineralization of turkey tendons is an efficient means of preserving elastic energy storage while providing for increased load-bearing ability required for locomotion of adult birds.

Animals↗
PubMed2002

A preliminary study on the effect of ultrasound therapy on the healing of surgically severed achilles tendons in five dogs.

This study was conducted on the left Achilles tendon in five clinically normal dogs. The Achilles tendon was surgically exposed and severed 3-4 cm proximal to the point of its insertion. Tenorrhaphy was undertaken by the application of three sutures on the various tendon units of the Achilles tendon using single locking-loop sutures with polyamide no. 1-0. The superficial digital flexor tendon was sutured with catgut using two horizontal mattress sutures. No ultrasound therapy was used in the animals of group I (control). Ultrasound therapy was given to the animals of group II (treated) starting from the third day post-operatively at 0.5 W/cm2 for 10 min daily for 10 days. A cortical screw was used for immobilization of the tibiotarsal joint which was removed 4 weeks after tenorrhaphy. Post-operatively, healing of the Achilles tendon was monitored using clinical observations, ultrasonography, gross and histomorphological observations at various intervals up to 120 days in both groups. Clinically, the dogs showed significant lameness for the first 4-5 days, which disappeared earlier in the ultrasound-treated (group II) animals than the controls (group I). Extension and flexion of the hock joint were found to be near normal at 6 weeks after the repair of the Achilles tendon. Ultrasonography showed anechoic to hypo-echoic echo-texture on days 3 and 7 after repair. By day 40, the echo-texture started to improve to hypo-echoic in group II, but in group I anechoic areas were still observed. However, the tendon showed near normal mottled hypo- to hyper-echoic texture in both groups by day 120. Gross observations suggested that the Achilles tendon in group II showed comparatively fewer adhesions than in group I animals. Histologically, in group II (treated), on day 40, the union was comparatively better without any inflammatory reaction. Bundle formation had begun in the ultrasound-treated animals which was not observed in the control animals. By day 90, more compact parallel bundle formation had taken place with minimum cellularity. Bundle formation was in its advanced stage in the treated animals. By day 120, the tendon tissue was comparatively acellular and looking like a normal tendon. The use of the cortical screw provided good immobilization and ultrasound therapy at 0.5 W/cm2 enhanced the Achilles tendon healing in dogs.

Achilles Tendon↗
PubMed2001

Achilles tendon injuries.

The Achilles tendon is the strongest tendon in the human body. Because most Achilles tendon injuries take place in sports and there has been an common upsurge in sporting activities, the number and incidence of the Achilles tendon overuse injuries and complete ruptures have increased in the industrialized countries during the last decades. The most common clinical diagnosis of Achilles overuse injuries is tendinopathy, which is characterized by a combination of pain and swelling in the Achilles tendon accompanied by impaired ability to perform strenuous activities. Most patients with Achilles tendon injury respond favorably to conservative treatment and only those who fail to respond to carefully followed nonoperative treatment should undergo surgery for repair. A complete rupture of the Achilles tendon usually occurs in sports that require jumping, running, and quick turns. Although histopathologic studies have shown that ruptured Achilles tendons include clear degenerative changes before the rupture, many of the Achilles tendon ruptures occur suddenly without any preceding signs or symptoms. Neither conservative nor operative treatment is a treatment of choice for the ruptured Achilles tendon. It is generally accepted that surgery should be performed on ruptured Achilles tendons in young, physically active patients and in those patients for whom the diagnosis or the treatment of the rupture has been delayed, whereas the results of conservative treatment are an acceptable outcome in older patients with sedentary lifestyles. Many important issues still remain unanswered concerning the cause, pathogenesis, diagnosis, and management of the Achilles tendon disorders. Only when these issues have been solved by well-controlled studies can tailored treatment protocols be created.

Achilles Tendon↗
PubMed1997

Patellar tendon ultrasonography and jumper's knee in female basketball players: a longitudinal study.

OBJECTIVE: To compare patellar tendon sonographic findings at baseline and at follow-up in active female basketball players with and without symptoms of jumper's knee. We hypothesized that baseline sonographic morphology would not reliably predict prognosis and, in particular, that it would not predict the need for surgery. DESIGN: Prospective longitudinal study with 12-month minimum follow-up. SETTING: Institutional elite athlete study group in Australia (Victorian Institute of Sport Tendon Study Group). PATIENTS AND PARTICIPANTS: A total of 15 female elite basketball players with 23 sonographically abnormal tendons and 15 matched control basketball players with 23 sonographically normal tendons. MAIN OUTCOME MEASURES: Sonographic patellar tendon appearance and clinical assessment of symptoms of jumper's knee at baseline and follow-up. Dimensions of abnormal regions were measured. RESULTS: At baseline, the 23 subject tendons contained sonographic hypoechoic regions (six currently symptomatic, eight previously symptomatic only, and nine never symptomatic). At follow-up, the hypoechoic areas in seven tendons had resolved (and caused no symptoms), the hypoechoic areas in 11 tendons had remained essentially the same size (five were symptomatic), and the hypoechoic areas in five tendons had expanded (three symptomatic). At baseline, there were no differences between the mean +/- SD cross-sectional areas of the abnormalities in the tendons that subsequently resolved (15.9 +/- 10.1 mm2) and those that remained unchanged (39.3 +/- 25.8) or expanded (25.3 +/- 12.5). The presence of a baseline sonographic abnormality predicted symptoms of jumper's knee at follow-up (p < 0.05), but the presence of symptoms of jumper's knee at baseline also predicted symptoms at follow-up (p < 0.05). No subject or control missed any games or underwent surgical treatment. CONCLUSIONS: Patellar tendon sonographic hypoechoic areas can resolve, remain unchanged, or expand in active sports-women without predicting symptoms of jumper's knee. Thus, symptoms were not directly related to sonographic tendon morphology. Sonographic hypoechoic regions ought not to constitute per se an indication for surgery.

Analysis of Variance↗
PubMed2002

Long-term ultrasonographic features of the Achilles tendon after rupture.

PURPOSE: To assess the long-term ultrasonographic appearance of rupture of the Achilles tendon. SUBJECTS AND METHODS: We examined 70 patients at an average of 63 months (range 10-120 months) after rupture of the Achilles tendon. We assessed the patient's contralateral tendon and also performed ultrasonography on the Achilles tendon of 70 age- and sex-matched controls. We recorded the maximum transverse anteroposterior diameter, the presence of intratendinous alterations, and the presence of intratendinous calcification. RESULTS: The average maximum anteroposterior diameter of the ruptured tendon was 11.7 mm (SD = 2.10). The patients' normal tendons measured an average of 5.4 mm (SD = 0.9), and there was an average measure of 4.9 mm (SD = 0.5) (p = 0.0001) in the controls. There was no difference in the maximum anteroposterior diameter of the ruptured tendon depending on the method of treatment (conservative, open repair, percutaneous repair). Seventeen patients exhibited areas of hypoechogenicity in their ruptured tendon, two patients had areas of hypoechogenicity in their unruptured contralateral tendon, and 10 patients had calcification in their ruptured tendon. CONCLUSION: The anteroposterior diameter of the ruptured tendon was significantly greater than the nonruptured contralateral. However, when compared with a group of individually age- and sex-matched controls, the patients' contralateral tendons had significantly greater maximum anteroposterior diameter and had a greater prevalence of intratendinous alterations. This difference may represent a background of subclinical tendinopathy that may predispose to rupture.

Achilles Tendon↗
PubMed2005

Neglected tendon and nerve injuries of the hand.

We retrospectively reviewed 445 patients with neglected tendon and nerve injuries treated between 1983 and 2003. Of these patients, 355 patients (447 tendons) had flexor tendon injuries, 62 patients (84 tendons) had extensor tendon injuries, and 28 patients had isolated nerve injuries. (In addition to these, 48 patients had nerve injuries associated with flexor tendon injuries; making a total of 76 patients with nerve injuries.) Most of the patients presented for treatment from 2 months to 2 years after the injury. The majority (73%) of patients with flexor tendon injuries were treated by free tendon grafting. Sixty-two patients required staged reconstruction using a silicon implant. The followup ranged from 12 to 83 months (mean, 45.8 months). In flexor tendon injuries, overall excellent results were seen in 83 of 447 tendons (18.5%) and good results were seen in 70.5%. In extensor tendon injuries, 23% had excellent results, 53% had good results, 34% had poor results. Seventy-six patients (114 nerves) of neglected nerve injuries of the hand were treated during the same period. In 48 (63%) patients the nerve injury was associated with tendon injury. End-to-end repair was possible in 89 nerves and the remainder was grafted. Because nerves in the hand have a predominant sensory component, sensory recovery was seen in the majority of patients.

Adolescent↗
PubMed2005

Dynamic changes appearing in collagen fibers during intrinsic tendon repair.

Intrinsic healing of severed tendons shows a delay in a gain in breaking strength and the tendon becomes translucent. The cause of tendon translucence was investigated in suture-repaired rat Achilles tendon. The repair site with adjacent translucent tendon were evaluated histologically on day 10 by immunofluorescence and transmission electron microscopy. The healing tendon translucent region by hematoxylin-eosin staining had few inflammatory cells, polarized light birefringence showed thinner collagen fibers, immunofluorescence showed few myofibroblasts, and transmission electron microscopy revealed frayed, irregular thin collagen fibers. During embryogenesis, tendon fibers grow by the addition of discreet collagen fibril segment structures. The speculation is that collagen fibril segment structures are released from collagen fibers within the translucent tendon region for reuse during the regeneration of tendon collagen fibers during intrinsic tendon repair. Healing tendon translucence is related to a decrease in the diameter of collagen fibers by the release of collagen fibril segments within tendon bundles/fascicles.

Achilles Tendon↗
PubMed2002

Change in length of relaxed muscle fascicles and tendons with knee and ankle movement in humans.

Ultrasonography was used to measure changes in length of muscle fascicles in relaxed human tibialis anterior and gastrocnemius during passively imposed changes in joint angle. Changes in the length of muscle fascicles were compared to changes in the length of the whole muscle-tendon units calculated from joint angles and anthropometric data. Relaxed muscle fascicles underwent much smaller changes in length than their muscle-tendon units. On average, muscle fascicles in tibialis anterior 'saw' 55 +/- 13 % (mean +/- S.D.) of the total change in muscle-tendon length. This indicates nearly half of the total change in muscle-tendon length was taken up by stretch of tendon. In gastrocnemius, which has relatively long tendons, only 27 +/- 9 % of the total change in muscle-tendon length was transmitted to muscle fascicles. Thus, the tendency for passive movement to be taken up by the tendon was greater for gastrocnemius than tibialis anterior (P = 0.002). For these muscles, the relatively large changes in tendon length across much of the physiological range of muscle-tendon lengths could not wholly be explained by tendon slackness, changes in fibre pennation, or stretch or contraction history of the muscle. Our data confirm that when joints are moved passively, length changes 'seen' by muscle fascicles can be much less than changes in the distance between muscle origin and insertion. This occurs because tendons undergo significant changes in length, even at very low forces.

Adult↗
PubMed2005

High strain mechanical loading rapidly induces tendon apoptosis: an ex vivo rat tibialis anterior model.

BACKGROUND: The role of apoptosis, or programmed cell death, has only recently been explored in tendon. OBJECTIVE: To investigate the development of apoptosis after high strain loading of rat tendon. METHODS: The right tibialis anterior tendons of three rats were prepared for mechanical loading, and left tendons were prepared identically as non-loaded controls. Tendon was loaded with 20% strain for six hours using a 1 Hz longitudinal sine wave signal. The following were used to assess apoptosis: (a) a monoclonal mouse antibody (F7-26) to label single stranded DNA breaks; (b) a rabbit polyclonal antibody that specifically recognises the cleaved form of caspase-3. RESULTS: Light microscopy confirmed that the high strain protocol induced a stretch overload injury. Control tendons showed little or no staining with the F7-26 antibody, but the loaded tendons displayed numerous apoptotic cells. The percentage of apoptotic cells (20%) in the loaded tendon was significantly greater than in the control tendon (1%) (p = 0.000). The labelled cells colocalised with abnormal nuclear morphology, including nuclear fragmentation. The staining against cleaved caspase-3 was positive in loaded tendons only, and localised both to nucleus and cytoplasm. CONCLUSION: This experiment extends knowledge of human tendon apoptosis by showing that apoptosis can occur in response to short term, high strain mechanical loading. This is the first report of mechanical loading of intact tendon causing excessive apoptosis.

Animals↗
PubMed2003

Achilles tendons: clinical relevance of neovascularization diagnosed with power Doppler US.

PURPOSE: To evaluate the clinical relevance of neovascularization diagnosed with power Doppler ultrasonography (US) in Achilles tendons in patients with chronic achillodynia. MATERIALS AND METHODS: Forty consecutive patients (mean age, 52 years; age range, 30-72 years) were examined. US was performed bilaterally and repeated after 3 months. Shape and echogenicity were assessed with gray-scale US and vascularization with power Doppler US. All patients were treated conservatively. Clinical assessment was performed after 0, 3, and 6 months by using visual analogue scale (VAS) scores (0, no pain; 100, unbearable pain). The VAS scores were compared with the initial US findings, and analysis of variance was used for repeated measurements. RESULTS: Neovascularization was present in 30 of 55 painful tendons and in one of 25 asymptomatic tendons. The mean VAS scores at 0, 3, and 6 months, respectively, for tendons with neovascularization were 52, 26, and 20; those for tendons without neovascularization were 39, 19, and 18 (P =.15). Forty-eight painful and nine asymptomatic tendons were spindle shaped. The mean VAS scores at 0, 3, and 6 months, respectively, for the spindle-shaped tendons were 48, 25, and 20; those for normally shaped tendons were 33, 10, and 16 (P =.17). Thirty-five painful and four asymptomatic tendons were inhomogeneous. The mean VAS scores at 0, 3, and 6 months, respectively, for symptomatic inhomogeneous tendons were 54, 29, and 25; those for symptomatic homogeneous tendons were 32, 12, and 9 (P <.001). CONCLUSION: Although neovascularization is a specific sign for pain, it does not indicate an unfavorable outcome. Conversely, tendon inhomogeneity seems to be associated with an unfavorable outcome.

Achilles Tendon↗
PubMed2006

Early voluntary exercise does not promote healing in a rat model of Achilles tendon injury.

Mechanical stress is an important modulator of connective tissue repair. However, the effects on tendon healing are very poorly defined, preventing optimal use of mechanical stress. We hypothesized that early voluntary exercise initially retards tendon repair but results in a faster recovery rate at longer term. Male Wistar rats were injured by a collagenase injection in the Achilles tendon, and exercise was voluntarily performed on a running wheel. We observed the persistent presence of neutrophils in injured tendons of rats that began exercise immediately after the trauma [injured + early exercise (Inj+EEx)]. Early exercise also increased the concentration of ED1(+) macrophages in injured tendons after 3 and 7 days compared with ambulatory injured rats (Inj). Similar results were obtained with the subset of ED2(+) macrophages in the tendon core 3 days after the collagenase injection. Furthermore, collagen content returned to normal values more rapidly in the Inj+EEx tendons than in the Inj group, but this was not associated with an increase in cell proliferation. Surprisingly, Inj+EEx tendons roughly displayed lower stiffness and force at rupture point relative to Inj tendons at day 28. Injured tendons of rats that began exercise only from day 7 had better mechanical properties than those of early-exercised rats 28 days postinjury. We speculate that the persistence of the inflammatory response and undue mechanical loading in the Inj+EEx tendons led to fibrosis and a loss of tendon function.

Animals↗