Fine structural alterations of collagen fibers in degenerative tendinopathy

Achilles Tendon Rupture and Dysmetabolic Diseases: A Multicentric, Epidemiologic Study

Introduction: Achilles tendon ruptures are common. Metabolic disorders, such as diabetes mellitus, hypercholesterolemia, thyroid disorders, and obesity, impair tendons health, leading to Achilles tendinopathy and likely predisposing patients to Achilles tendon ruptures. Materials and methods: Patients who visited the Orthopedic Outpatient Clinics and the Accident and Emergency Departments of five different hospitals in Italy were recruited. Through telephone interviews, we administered a questionnaire to all the patients who had undergone surgical ATR repair, evaluating their past medical history, sport- and work-related activities, drug use, and post-operative rehabilitation outcomes. Results: “Return to work activities/sport” was negatively predicted by the presence of a metabolic disorder (β = −0.451; OR = 0.637) and ‘open’ surgery technique (β = −0.389; OR = 0.678). “Medical complications” were significantly predicted by metabolic disorders (β = 0.600 (0.198); OR = 1.822) and was negatively related to ‘mini-invasive’ surgery (i.e., not ‘open’ nor ‘percutaneous’) (β = −0.621; OR = 0.537). “Immediate weightbearing” and “immediate walking without assistance” were negatively predicted by ‘open’ technique (β = −0.691; OR = 0.501 and β = −0.359 (0.174; OR = 0.698)). Conclusions: Metabolic conditions can strongly affect post-operative outcomes following surgical repair of acute Achilles tendon tears.

Anatomical and Functional Considerations in Achilles Tendon Lesions

The pathologic conditions of the Achilles tendon are best understood in the context of its unique anatomy and functional demands. Some of these unique considerations include its high physiologic load demands, microscopic tissue composition, muscular origin spanning the knee joint, intimate insertional relationship with the plantar fascia, sensory innervation, and vascular supply with watershed areas. Risks of both acute rupture and chronic tendinopathy are affected by the tendon's anatomy and its functional demands. The tendon's functional anatomy changes with advancing age, notably in its collagen composition and vascular supply.

More histologic and ultrastructural degenerative signs in the subscapularis tendon and the joint capsule in male patients with shoulder impingement

PURPOSE

The purpose of the present study was to analyze biopsy samples from the subscapularis tendon and from the joint capsule from male patients with shoulder impingement syndrome (SAIS) and compare them with samples from male patients with post-traumatic recurrent shoulder instability. The hypothesis of the study was that patients with SAIS would have more histologic and ultrastructural degenerative changes in their subscapularis tendon and joint capsule than patients with post-traumatic recurrent shoulder instability.

METHODS

Male patients scheduled for surgery, with either subacromial decompression or Bankart reconstruction, were included. Four biopsies from each patient were obtained from the capsule and four from the subscapularis tendon during arthroscopic surgery. The histologic characteristics and the presence of glycosaminoglycans were assessed using the light microscope, and the ultrastructure was assessed using a transmission electron microscope.

RESULTS

Eight patients, median age 53 (45-74) years (p < 0.0001), were included in the impingement group, and 12 patients, median age 27 (22-48) years, were included in the instability group. The histologic assessment revealed significantly higher cellularity and total degeneration score in the capsule (p = 0.016 and p = 0.014 respectively) in patients with subacromial impingement compared with the instability patients. The corresponding finding was not made for the subscapularis tendon. The ultrastructural evaluation revealed that the instability patients had more fibrils with a large diameter (indicating less degeneration) in both the subscapularis tendon and the capsule compared with the impingement patients (p < 0.0001).

CONCLUSION

Male patients with subacromial impingement have more histologic and ultrastructural degenerative changes in their shoulder compared with patients with post-traumatic recurrent shoulder instability.

CLINICAL RELEVANCE

It appears that in patients with subacromial impingement, the whole shoulder joint is affected and not only the subacromial space. It is the opinion of the authors that intra-articular therapeutic injections could be tried more often in these patients.

LEVEL OF EVIDENCE

III.

Development of overuse tendinopathy: A new descriptive model for the initiation of tendon damage during cyclic loading

Tendinopathic tissue has long been characterized by changes to collagen microstructure. However, initial tendon damage from excessive mechanical loading-a hallmark of tendinopathy development-could occur at the nanoscale level of collagen fibrils. Indeed, it is on this scale that tenocytes interact directly with tendon matrix, and excessive collagen fibril damage not visible at the microscale could trigger a degenerative cascade. In this study, we explored whether initiation of tendon damage during cyclic loading occurs via a longitudinal compression-induced buckling mechanism of collagen fibrils leading to nanoscale kinkband development. Two groups of tendons were cyclically loaded to equivalent peak stresses. In each loading cycle, tendons in one group were unloaded to the zero displacement mark, while those in the other group were unloaded to a nominal level of tension, minimizing the potential for fibril buckling. Tendons that were unloaded to the zero displacement mark ruptured significantly sooner during cyclic loading (1,446 ± 737 vs. 4,069 ± 1,129 cycles), indicating that significant fatigue damage is accrued in the low stress, toe region of the load-deformation response. Ultrastructural analysis using scanning electron microscopy of tendons stopped after 1,000 cycles showed that maintaining a nominal tension slowed the accumulation of kinkbands, supporting a longitudinal compression-induced buckling mechanism as the basis for kinkband development. Based on our results, we present a new descriptive model for the initiation of tendon damage during cyclic loading. The so-called Compression of Unrecovered Elongation or CUE Model may provide useful insight into the development of tendinopathy. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:467-476, 2018.

Structural and Ultrastructural Characteristics of Bone-Tendon Junction of the Calcaneal Tendon of Adult and Elderly Wistar Rats

Tendons are transition tissues that transfer the contractile forces generated by the muscles to the bones, allowing movement. The region where the tendon attaches to the bone is called bone-tendon junction or enthesis and may be classified as fibrous or fibrocartilaginous. This study aims to analyze the collagen fibers and the cells present in the bone-tendon junction using light microscopy and ultrastructural techniques as scanning electron microscopy and transmission electron microscopy. Forty male Wistar rats were used in the experiment, being 20 adult rats at 4 months-old and 20 elderly rats at 20 months-old. The hind limbs of the rats were removed, dissected and prepared to light microscopy, transmission electron microscopy and scanning electron microscopy. The aging process showed changes in the collagen fibrils, with a predominance of type III fibers in the elderly group, in addition to a decrease in the amount of the fibrocartilage cells, fewer and shorter cytoplasmic processes and a decreased synthetic capacity due to degradation of the organelles involved in synthesis.

Percutaneous ultrasonic debridement of tendinopathy-a pilot Achilles rabbit model

Background

Tendinopathy is a common clinical pathology, with mixed treatment results, especially when chronic. In this study, we examine the effects of an ultrasonic debridement modality in a rabbit tendinopathy model.

We asked four questions: 1) Was it possible to create and visualize with ultrasound a tendinopathy lesion in a rabbit Achilles tendon? 2) Was it possible to guide a 19-gauge ultrasonic probe into the tendinopathy lesion? 3) Following ultrasonic treatment, was tendinopathy debris histologically present? and 4) Was the collagen profile qualitatively and quantitatively normalized following treatment?

Methods

Skeletally mature female New Zealand white rabbits (n = 12) were injected with, ultrasonography localization, 0.150 ml of collagenase into the Achilles tendon. The collagenase-induced Achilles tendinopathy (3 weeks) was treated with percutaneous ultrasonic debridement. The tendons were harvested, at 3 weeks after treatment, and were subjected to histological assessment (modified Movin score) and biochemical analysis (collagen isoform content).

Results

Histopathological examination revealed that all tendons injected with collagenase showed areas of hypercellularity and focal areas of tendon disorganization and degeneration. The treated tendons had lower (improved) histopathological scores than injured tendons (P < 0.001). Western blot analysis showed that ultrasonic therapy restored, within statistical limits, collagen type I, III, and X expressions in a treated tendon, to qualitative and semi-quantitative levels of a normal tendon.

Conclusions

We were successfully able to create a collagenase-injected tendinopathy lesion in a rabbit Achilles tendon and visualize the lesion with an ultrasound probe. A 19-gauge ultrasonic probe was inserted into the tendinopathic lesion under direct ultrasound guidance, and minimal tendinopathic debris remained after treatment. The treated tendon demonstrated a normalized qualitative and semi-quantitative collagen profile and improved histological appearance in the short term. This technique demonstrates scientific merit with respect to the minimally invasive treatment of tendinopathy and warrants further studies.

Clinical relevance

Recalcitrant tendinopathy has evaded consistent non-operative treatment since the tendinopathic debris remains in situ, to some extent, with non-operative approaches. This percutaneous emulsification/evacuation approach, under direct ultrasound visualization, has the potential to cure recalcitrant tendinopathies without open surgery, which would benefit the patient and result in significant healthcare cost reductions.

Experimental model of Achilles tendon injury in rats

PURPOSE

To describe an effective experimental model to study the Achilles tendon healing.

METHODS

Forty male Rattus norvegicus albinus, Wistar lineage adult male weighing 250 to 300g were used for this experiment and thirty were surgically submitted to bilateral partial transverse section of the Achilles tendon. The right tendon was treated with radio waves (RF) whereas the left tendon served as control. On the third postoperative day, the rats were divided into four experimental groups consisting of ten rats each which were treated with monopolar RF adjusted to 650 kHz and 2w, for two minutes twice a week and a group of normal animals without any intervention, until they were sacrificed on the 7th, 14th and 28th days, respectively. Tendons were weighed and collagen quantification was evaluated by hydroxyprolin content.

RESULTS

Significant reduction in collagen content on day 7, 14 and 28 was related to control experiment to normal tendon (7 days, p<0.01; 14 e 28 days, p<0.05).

CONCLUSION

The experimental model has been effective and available to be used to study Achilles tendon healing.

Gene expression of tendon collagens and tenocyte markers in long-term monolayer and high-density cultures of rat tenocytes

As a result of repeated movement, tendons are functionally open to traumas. According to this situation, tenocytes have already been used for tissue engineering therapies. It has been reported that long-term monolayer (ML) culture of tenocytes may lead to a phenotypic drift within passages. Depending on our previously published work, it is clearly demonstrated that high-density (HD) culture improves cell growth and differentiation of tenocytes. However, it is not yet established if HD favors the differentiated state during long-term culture. Therefore, we compared the differences in gene expression of tendon collagens and tendon markers of tenocytes from long-term ML and HD culture conditions by quantitative, real-time polymerase chain reaction (QRT-PCR) for over a period of 3 weeks. COLI, COLIII, COLV, Scx, and Tnmd were target genes as the major matrix constituents of tendons as well as being involved in matrix integrity and tenocyte phenotype. According to our results, tenocytes in HD culture synthesized less amounts of COLIII, COLV, and Tnmd, and dependent on the investigation time point, higher amounts of Scx. We consider that tenocytes produced in HD culture system may not provide sufficient efficiency during tissue engineering approaches. By the fact that most molecules showed significantly higher expression profiles in ML culture condition, it is suggested that culture and passage in ML should be taken into consideration for further tissue engineering approaches to maintain a phenotype with less amount of drift.

The effect of aging on migration, proliferation, and collagen expression of tenocytes in response to ciprofloxacin

Quinolone-induced tendinopathy or tendon rupture tends to be age-related. However, the synergistic effects of quinolone and aging on tenocytes remained to be explored. Tenocytes intrinsic to rat Achilles tendon from two age groups (young: 2 months; and near senescent (old): 24 months) were treated with ciprofloxacin. Tenocyte migration and proliferation were assessed by transwell filter migration assay and MTT (3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay, respectively. Messenger RNA and protein expressions of types I and III collagen were determined by reverse transcription-polymerase chain reaction (RT/PCR) and Western blot analysis, respectively. Transwell filter migration assay revealed that ciprofloxacin inhibited tenocytes migration, which became more significant in old tenocytes (p < 0.05). The results of MTT assay revealed that tenocytes proliferation decreased after ciprofloxacin treatment (p < 0.05), which also became more significant in old tenocytes. The results of RT-PCR and Western blot analysis revealed that mRNA and protein expressions of type I collagen remained unchanged in either young or old tenocytes with ciprofloxacin treatment, whereas the expressions of type III collagen were down-regulated by ciprofloxacin, which was more significant in old tenocytes. In conclusion, aging potentiated the ciprofloxacin-mediated inhibition of migration, proliferation, and expression of type III collagen of tenocytes.

Accelerated healing of the rat Achilles tendon in response to autologous conditioned serum

BACKGROUND

Despite advances in the treatment of ruptured Achilles tendon, imperfections of endogenous repair often leave patients symptomatic. Local administration of autologous conditioned serum (ACS) in patients with inflammatory, degenerative conditions has shown beneficial effects.

PURPOSE

Because ACS also contains growth factors that should accelerate tendon healing, we studied the effect of ACS on the healing of transected rat Achilles tendon.

STUDY DESIGN

Controlled laboratory study.

METHODS

In preliminary in vitro experiments, rat tendons were incubated with ACS and the effect on the expression of Col1A1 and Col3A1 was assessed by real-time quantitative polymerase chain reaction. To test its effect in vivo, the Achilles tendons of 80 Sprague Dawley rats were transected and sutured back together. Ten rats from each group (ACS group, n = 40; control group, n = 40) were euthanized at 1, 2, 4, and 8 weeks postoperatively for biomechanical (n = 7) and histologic (n = 3) testing. Lysyl oxidase activity was assayed by a flurometric assay. The organization of repair tissue was assessed histologically with hematoxylin and eosin- and with Sirius red-stained sections, and with immunohistochemistry.

RESULTS

Tendons exposed to ACS in vitro showed a greatly enhanced expression of the Col1A1 gene. The ACS-treated tendons were thicker, had more type I collagen, and an accelerated recovery of tendon stiffness and histologic maturity of the repair tissue. However, there were no differences in the maximum load to failure between groups up to week 8, perhaps because lysyl oxidase activities were unchanged.

CONCLUSION AND CLINICAL RELEVANCE

Overall, our study demonstrates that treatment with ACS has the potential to improve Achilles tendon healing and should be considered as a treatment modality in man. However, as strength was not shown to be increased within the parameters of this study, the clinical importance of the observed changes in humans still needs to be defined.

The patellar tendinopathy in athletes: a sonographic grading correlated to prognosis and therapy

The purpose of this study is to determine in the athletes a sonographic grading of the patellar tendinopathy correlated to prognosis and therapy. The 298 patellar overuse tendinopathies were divided in four grades according to the extension of the injured area of the tendon in the axial sonograms. Grades 1, 2, and 3 were managed with medical and physical therapy. A surgical treatment was performed in grade 4 and in grades 1, 2, and 3 tendinopathies not responding to our conservative therapy. There were 21.8% injuries in grade 1 (100% responding; prognosis 20 days), 61.2% injuries in grade 2 (94.5% responding; prognosis 40 days), 16.4% injuries in grade 3 (85.7% responding; prognosis 90 days), and 0.6% injuries in grade 4. The sonographic study is fundamental to characterize adequately the patellar tendinopathy. The conservative therapy is the first option for grades 1, 2, and 3 as it determines a complete healing in most of cases.

Histological analysis of achilles tendons in an overuse rat model

The purpose of this study was to design an animal model that induces histological changes in Achilles tendons consistent with those cited in the literature for human Achilles tendon disease. Sprague-Dawley rats were subjected to 10 degrees uphill treadmill running on a custom-designed rodent treadmill and at a speed of 17 meters per minute for 1 h, five times per week, over a 12-week treatment period. Subsequent histological analysis revealed alterations in the rat Achilles tendon that were generally consistent with those described in the literature for diseased human tendon tissues. These features include: decreased collagen fiber organization, more intense collagen staining, and increased cell nuclei numbers. Interestingly, though, immunohistochemical cell typing suggests that the observed increased cellularity does not include a significant inflammatory component but is secondary to increased numbers of endothelial cells (i.e., vascularization) and fibroblasts. These histological features likely represent a biological repair/remodeling response resulting from overuse running.

Region specific patellar tendon hypertrophy in humans following resistance training

AIM

To examine if cross-sectional area (CSA) differs along the length of the human patellar tendon (PT), and if there is PT hypertrophy in response to resistance training.

METHODS

Twelve healthy young men underwent baseline and post-training assessments. Maximal isometric knee extension strength (MVC) was determined unilaterally in both legs. PT CSA was measured at the proximal-, mid- and distal PT level and quadriceps muscle CSA was measured at mid-thigh level using magnetic resonance imaging. Mechanical properties of the patellar tendons were determined using ultrasonography. Subsequently, subjects performed 12 weeks of heavy resistance knee extension training with one leg (Heavy-leg), and light resistance knee extension training with the other leg (Light-leg).

RESULTS

The MVC increased for heavy-leg (15 +/- 4%, P < 0.05), but not for light-leg (6 +/- 4%). Quadriceps CSA increased in heavy-legs (6 +/- 1%, P < 0.05) while unchanged in light-legs. Proximal PT CSA (104 +/- 4 mm(2)) was smaller than the mid-tendon CSA (118 +/- 3 mm(2)), which again was smaller than distal tendon CSA (127 +/- 2 mm(2), P < 0.05). Light-leg PT CSA increased by 7 +/- 3% (P < 0.05) at the proximal tendon level, but was otherwise unchanged. Heavy-leg PT CSA increased at the proximal and distal tendon levels by 6 +/- 3% and 4 +/- 2% respectively (P < 0.05), but was unchanged at the mid tendon level. PT stiffness increased in heavy-legs (P < 0.05) but was unchanged in light-legs. Modulus remained unchanged in both legs.

CONCLUSIONS

To our knowledge, this study is the first to report tendon hypertrophy following resistance training. Further, the data show that the human PT CSA varies along the length of the tendon.

Ultrastructural collagen fibril alterations in the patellar tendon 6 years after harvesting its central third

BACKGROUND

Clinically, donor site problems are common, even in the long term after anterior cruciate ligament reconstruction using patellar tendon autograft. However, there is a lack of knowledge in terms of the mid- and long-term ultrastructural appearance of the previously harvested tendon in humans.

HYPOTHESIS

The patellar tendon does not regain normal ultrastructure 6 years after harvesting its central third and leaving the defect open.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Thirteen patients were included in the study. Biopsy specimens were obtained from the central and lateral thirds of the patellar tendon under ultrasound guidance 71 months (range, 68-73 months) after the reconstruction. Ten biopsy specimens from other subjects with asymptomatic patellar tendons served as controls. The sections were evaluated using transmission electron microscopy. Longitudinal sections were used for morphological evaluation, and the fibril diameter was measured on the transverse sections and grouped into 5 diameter classes.

RESULTS

All control specimens were found to have a compact extracellular matrix with regularly oriented collagen fibrils. Specimens from the lateral part of the harvested tendons displayed a more heterogeneous extracellular matrix. In 3 specimens, the extracellular matrix was different from that of the control specimens. Specimens from the central part of the harvested tendons displayed an even more heterogeneous extracellular matrix, with 8 specimens judged as heterogeneous. The fibril diameter in control specimens displayed the most heterogeneous pattern, and all 5 fibril classes were present. All fibril classes were found in the lateral biopsy specimens from the previously harvested tendons, but the 2 smallest fibril classes (0-30 and 31-60 nm) were significantly more dominant compared with control specimens (P < .0001). In the central specimens from the previously harvested tendons, only the 3 smallest size classes were found (P < .0001 vs controls).

CONCLUSION

Six years after harvesting its central third and leaving the defect open, the patellar tendon revealed a "more heterogeneous matrix" with changes in ultrastructural morphology and relative fibril diameter distribution compared with normal control tendon.

The effect of corticosteroid on collagen expression in injured rotator cuff tendon

BACKGROUND

Subacromial corticosteroid injections are commonly used in the nonoperative management of rotator cuff disease. The effects of corticosteroid injection on injured rotator cuff tendons have not been studied. Our aims were to characterize the acute response of rotator cuff tendons to injury through the analysis of the type-III to type-I collagen expression ratio, a tendon injury marker, and to examine the effects of corticosteroid on this response.

METHODS

Sixty Sprague-Dawley rats were randomly assigned to four groups: control, tendon injury, steroid treatment, and tendon injury and steroid treatment. Six rats served as sham controls. Unilateral tendon injuries were created with full-thickness defects across 50% of the total width of the infraspinatus tendon, 5 mm from its humeral insertion. Steroid treatment with a single dose of methylprednisolone (0.6 mg/kg), equivalent to that given to humans, was injected into the subacromial space under direct visualization. Steroid treatment followed the creation of an injury in the rats in the injury and steroid treatment group. At one, three, and five weeks after the injury, the total RNA isolated from tendons was quantified with real-time polymerase chain reaction with use of primers for type-I and type-III collagen and ribosomal 18s RNA.

RESULTS

The type-III to type-I collagen expression ratio remained at baseline at all time-points in the control and sham groups. At one week, the type-III to type-I collagen expression ratio increased more than fourfold above the control level in the tendon injury group (p = 0.017) and the tendon injury and steroid treatment group (p = 0.003). The ratio remained greater than twofold above the control at three weeks in both groups (p = 0.003 and p = 0.037) and returned to baseline at five weeks. Interestingly, the group that had steroid treatment only showed an increase of >4.5-fold (p = 0.001) in the type-III to type-I collagen expression ratio, without structural injury to the tendon. This ratio returned to baseline levels by three weeks.

CONCLUSIONS

A single dose of corticosteroid does not alter the acute phase response of an injured rotator cuff tendon in the rat. However, the same steroid dose in uninjured tendons initiates a short-term response equivalent to that of structural injury.

Ultrasound stimulation of types I and III collagen expression of tendon cell and upregulation of transforming growth factor beta

Traumatic tendon injuries are commonly treated with ultrasound. However, previous research has not examined the molecular mechanism of this therapeutic effect on collagen synthesis of tendon cells. This study was designed to determine the effect of ultrasound on the expression of type I and type III collagen of tendon cells intrinsic to rat Achilles tendon. Whether a correlation exits between this effect and the expression of transforming growth factor beta (TGF-beta), which enhances collagen synthesis, was also investigated. Tendon cells after ultrasound treatment and protein expression of types I and III collagen were determined by immunocytochemistry. The mRNA expressions of alpha1(I) procollagen, alpha1(III) procollagen, and TGF-beta were determined by reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, the concentration of TGF-beta in conditioned medium was evaluated by enzyme-linked immunosorbent assay (ELISA). Immunocytochemical staining revealed that ultrasound-treated tendon cells were stained more strongly for types I and III collagen than were control cells. Upregulation of procollagen alpha1(I) gene, procollagen alpha1(III) gene, and TGF-beta at the mRNA level was confirmed by RT-PCR. A dose-dependent increase in the concentration of TGF-beta in conditioned medium obtained from cells treated with ultrasound was demonstrated by ELISA assay (p = 0.043). In conclusion, ultrasound stimulates the expression of type I and type III collagen in a process that is likely mediated by the upregulation of TGF-beta.

Similar histopathological picture in males with Achilles and patellar tendinopathy

PURPOSE

To ascertain whether there are differences in the histopathological appearance of tendinopathic Achilles and patellar tendons.

METHODS

In males, we studied biopsies from tendinopathic Achilles (N = 28; average age 34.1 yr) and patellar tendons (N = 28; average age 32.1), Achilles tendons (N = 21; average age 61.8 yr) from deceased patients with no known tendon pathology, and patellar tendons (N = 15; average age 28.3) from patients undergoing anterior cruciate ligament reconstruction. Hematoxylineosin stained slides were interpreted using a semiquantitative grading scale (0: normal to 3: maximally abnormal) for fiber structure, fiber arrangement, rounding of the nuclei, regional variations in cellularity, increased vascularity, decreased collagen stainability, and hyalinization. All slides were assessed blindly twice, the agreement between two readings ranging from 0.170 to 0.750 (kappa statistics).

RESULTS

The highest mean score of tendinopathic Achilles tendons was not significantly different from that of tendinopathic patellar tendons (11.6 +/- 5 and 10.4 +/- 3, respectively). The ability to differentiate between an Achilles tendon and a patellar tendon was low.

CONCLUSIONS

Tendinopathic Achilles and patellar tendons show a similar histological picture. It was not possible to identify whether a specimen had been harvested from an Achilles or a patellar tendon on the basis of histological examination. The general pattern of degeneration was common to both tendinopathic Achilles and patellar tendons. A common, as yet unidentified, etiopathological mechanism may have acted on both these tendon populations.

Ankle joint proprioception and passive mechanical properties of the calf muscles after an Achilles tendon rupture: a comparison with matched controls

OBJECTIVE

To examine if ankle joint proprioception, passive stiffness, and torque relaxation responses of the involved and uninvolved limbs of persons with a previous history of an Achilles tendon rupture were different from matched controls.

DESIGN

Quasi-experimental mixed design.

BACKGROUND

The influence of an Achilles tendon rupture on the proprioceptive and kinetic performance of the involved and uninvolved ankle is not known.

METHODS

Twenty persons (mean age, 44.8 years) with a unilateral rupture and 20 matched controls (mean age, 44.2 years) volunteered. Proprioception was tested with a position-matching protocol from which absolute errors were quantified. A dynamometer was used to measure ankle joint angle and passive torque from which stiffness and torque relaxation were calculated.

RESULTS AND CONCLUSIONS

Proprioception absolute errors for the involved and uninvolved limbs of the experimental group were 27% and 31% greater respectively, than values for the control group. Torque relaxation values were greater in the involved limb versus the uninvolved limb or the control group (P=0.003-0.04). In conclusion, participants with a previous history of an Achilles tendon rupture display proprioception deficits in both limbs and greater torque relaxation in the involved limb in comparison to matched controls.

RELEVANCE

Bilateral deficits in ankle joint proprioception, as reported in this study, suggest the uninvolved limb may not serve as an effective control and because proprioception deficits influence some functional tests, Achilles tendon rupture patients may benefit from proprioception training.

In situ gene transfer into animal tendons by injection of naked DNA and electrotransfer

BACKGROUND

Degenerative or traumatic tendon injuries are extremely common but often heal poorly, not restoring the normal function of the injured tissues. Gene transfer could improve the repair process, by permitting local production of therapeutic substances, e.g. growth factors.

METHODS AND RESULTS

Injection of a plasmid carrying the lacZ marker gene was performed into the Achilles tendons of rat and mouse, and the patellar tendons of rabbit. At 48 h, transduced cells were found in the injected zones of the tendons but represented a minority of the tendon cells. A kinetics study in rats permitted observation of a gradual decrease with time in the beta-gal-expressing cell number; at day 42 no more gene expression was detected. Noteworthy, no inflammatory reaction was observed. We then investigated whether electrotransfer could improve gene transfer efficacy in rat tendon by delivering in situ electric pulses after DNA injection. Gene transfer was improved at best by approximately 50% under certain electrical conditions (200 V for 10 ms or 1200 V for 100 micro s). Finally, multiple injections of plasmid permitted an increase in the number of transduced cells by approximately 400%.

CONCLUSIONS

In situ injection of naked DNA into tendons is a very simple technique that permits delivery of genes with a duration of expression sufficient for clinical application aimed at modulating healing or restoration of a degenerative tendon. Despite a low transfer efficiency, this method should be compatible with clinical applications aimed at delivering therapeutic substances acting at low concentration.

Computerized ultrasonographic tissue characterization of equine superficial digital flexor tendons by means of stability quantification of echo patterns in contiguous transverse ultrasonographic images

OBJECTIVE

To describe a method of computerized ultrasonographic tissue characterization that includes structures below the size limits of resolution in equine superficial digital flexor tendons.

SAMPLE POPULATION

2 damaged and 2 structurally normal superficial digital flexor tendons.

PROCEDURE

Transverse ultrasonographic images were collected along the tendon long axis. Stability of echo pattern was quantified by means of variation in gray levels of each pixel in contiguous images and expressed as correlation, entropy, and waviness ratios.

RESULTS

Normal young and normal old tissues were characterized by high correlation and low entropy and waviness ratios. In necrotic tissue, collapsed intratendinous septa resulted in high correlation, moderate entropy, and high waviness ratios. In early granulation tissue, complete lack of bundle formation resulted in values of zero for correlation and waviness ratios; loose connective tissue matrix resulted in a high entropy ratio. In late granulation tissue, formation of new bundles resulted in a high correlation ratio; swollen intratendinous septa and incomplete organization of connective tissue matrix were reflected in high entropy and waviness ratios. In early fibrotic tissue, rearrangement of tendon bundles resulted in a correlation ratio within reference range and a slight increase in the waviness ratio; an increase in cellularity and lack of fibrillar arrangement led to an increase in the entropy ratio. In late fibrotic and scar tissues, inferior quality of repair with almost complete lack of organization was reflected in low to moderate correlation, low waviness, and high entropy ratios.

CONCLUSIONS AND CLINICAL RELEVANCE

Stability of echo patterns accurately reflects homogeneity of tendons in horses.

Ruptured Achilles tendons are significantly more degenerated than tendinopathic tendons

OBJECTIVE

To ascertain whether there is an association between tendinopathic and ruptured Achilles tendons, hypothesizing that the histopathological aspects of tendinosis in tendinopathic tendons are less advanced than those found in ruptured Achilles tendons.

METHODS

This was a comparative cohort study at a university teaching hospital. Histological examination was performed using hematoxylin and eosin and alcian blue/periodic acid-Schiff stained slides. The slides were interpreted using a semiquantitative grading scale assessing fiber structure, fiber arrangement, rounding of the nuclei, regional variations in cellularity, increased vascularity, decreased collagen stainability, hyalinization, and glycosaminoglycan. We calculated a pathology score giving up to three marks for each of the above variables, with 0 being normal and 3 being maximally abnormal. All the histology slides were assessed twice in a blinded manner, the agreement between two readings ranging from 0.170 to 0.750 (kappa statistics).

RESULTS

We studied biopsy samples from the Achilles tendon of patients undergoing open repair for a subcutaneous rupture of their Achilles tendon (N = 35; average age (+/- SD), 48.4 +/- 16.9 yr; range, 26-80), biopsy specimens from the Achilles tendon of patients undergoing exploration for Achilles tendinopathy (N = 13; average age, 35.7 +/- 12.9 yr; range, 18-67) and specimens of Achilles tendons from individuals with no known tendon pathology (N = 16; average age, 65 +/- 19.1 yr; range, 46-82). The highest mean score of ruptured tendons was significantly greater than that of tendinopathic tendons (17.4 +/- 4.9 vs 10.5 +/- 6.1, P < 0.001), and highest mean score of tendinopathic tendons was greater that that of control tendons (10.5 +/- 6.1 vs 5.9 +/- 7.3) (P < 0.001).

CONCLUSION

Ruptured and tendinopathic tendons are histologically significantly more degenerated than control tendons. The general pattern of degeneration was common to the ruptured and tendinopathic tendons, but there was a statistically significant greater degree of degeneration in the ruptured tendons. It is therefore possible that there is a common, as yet unidentified, pathological mechanism that has acted on both of these tendon populations.

Tenocytes from ruptured and tendinopathic achilles tendons produce greater quantities of type III collagen than tenocytes from normal achilles tendons. An in vitro model of human tendon healing

Type I collagen is the main collagen in tendons; type III collagen is present in small amounts. Ruptured Achilles tendons contain a significantly greater proportion of type Ill collagen, which predisposes them to rupture. We used an in vitro model to determine whether tenocytes from Achilles tendons that were ruptured (N = 22), nonruptured (N = 7), tendinopathic (N = 12), and fetal (N = 8) show different behavior. Samples of Achilles tendon were digested with collagenase and the released tenocytes were collected. Primary tenocyte cultures were established and subsequently cultured onto glass coverslips. Once a confluent monolayer was obtained, the cell populations were "wounded" by scraping a pipette tip along the surface. The cultures were further incubated for either 1, 4, 8, 12, 16, or 24 hours, and production of types I and II collagen was assessed by immunostaining. In cultures from ruptured and tendinopathic tendons, there was increased production of type Ill collagen. Athletic participation places excess stress on the Achilles tendon, which could potentially lead to areas of microtrauma within the tendon. These areas may heal by the production of type III collagen, which is an abnormal healing response. Accumulation of such episodes of microtrauma could resuit in a critical point where the resistance of the tissue to tensile forces is compromised and tendon rupture occurs.

Macroscopic 'degeneration' of equine superficial digital flexor tendon is accompanied by a change in extracellular matrix composition

Injuries to the superficial digital flexor tendon are common in horses required to gallop and jump at speed. Partial rupture of this tendon usually occurs in the central core of the midmetacarpal region and may be preceded by localised degenerative changes. Post mortem examination of apparently normal equine flexor tendons has revealed an abnormal macroscopic appearance in the central core, characterised by a reddish discolouration. We have previously shown that there is also physical damage to the collagen fibres. In the present study we tested the hypothesis that the abnormal appearance is accompanied by changes in the composition of the extracellular matrix of the tendon. Biochemical analysis of the extracellular matrix demonstrated an increase in total sulphated glycosaminoglycan content, increase in the proportion of type III collagen and decrease in collagen linked fluorescence in the central core of 'degenerated' tendons relative to tissue from the peripheral region of the same tendon. Dry matter content and total collagen content were not significantly different between tendon zones or normal and 'degenerated' tendons. These changes suggest a change in cell metabolism and matrix turnover in the central core of the tendon and are likely to contribute to a decrease in mechanical properties in this part of the tendon, predisposing to the characteristic partial rupture of the tendon.

Etiology, diagnosis, and treatment of tendonitis: an analysis of the literature

Tendonitis is a common diagnosis in sports medicine. The traditional view of tendonitis is a tendon injury resulting from repetitive mechanical load with a subsequent inflammatory response. The English literature from 1966 to the present on the etiology, diagnosis, and treatment of tendonitis was evaluated. There is some scientific support in the literature for the diagnosis of tenosynovitis and tendinosis as a pathologic entity. Actual inflammation of tendon tissue consistent with tendonitis has not been seen clearly in patho-anatomic studies. Conclusive evidence confirming that repetitive mechanical load is a major etiologic factor could not be found. Similarly, strength deficits, inflexibility, and improper equipment have not been studied in a controlled prospective manner. Other factors such as age and tendon vascularity have been consistently correlated with these injuries although their overall importance remains difficult to assess. There are no controlled studies on treatment through physical therapy aimed at flexibility and/or strengthening. Treatment with anti-inflammatory drugs has been studied extensively. However, only nine of 32 studies are prospective and placebo controlled. Some pain relief was found in five of the nine controlled studies, but healing of the tendon problem was not studied in these short follow-up studies. Twenty-three studies on steroid injections were found. Eight were prospective and placebo controlled studies, with three showing beneficial effects of the injection at follow-up. It was concluded that much of the pathology and etiology of tendonitis remains unclear. The possibility must be considered that current treatment methods may not significantly affect the natural history.

Histopathological findings in spontaneous tendon ruptures

A spontaneous rupture of a tendon may be defined as a rupture that occurs during movement and activity, that should not and usually does not damage the involved musculotendinous units (1). Spontaneous tendon ruptures were uncommon before the 1950s. Böhler found only 25 Achilles tendon ruptures in Wien between 1925 and 1948 (2). Mösender & Klatnek treated 20 Achilles tendon ruptures between 1953 and 1956, but 105 ruptures between 1964 and 1967 (3). Lawrence et al. found only 31 Achilles tendon ruptures in Boston during a period of 55 years (1900-1954) (4). During the recent decades tendon ruptures have, however, become relatively common in developed countries, especially in Europe and North America. A high incidence of tendon ruptures has been reported in Austria, Denmark, Finland, Germany. Hungary, Sweden, Switzerland and the USA; somewhat lower incidences have been reported in Canada, France, Great Britain and Spain. On the other hand, Greece, Japan, the Netherlands and Portugal have reported a clearly lower incidence. Interestingly, Achilles tendon ruptures are a rarity in developing countries, especially in Africa and East-Asia (5). In many developed countries, the increases in the rupture incidence have been dramatic. In the National Institute of Traumatology in Budapest, Hungary, the number of patients with an Achilles tendon rupture increased 285% in men and 500% in women between two successive 7-year periods, 1972-1978 and 1979-1985 (5).

Clinical and sonographic evaluation of the risk of rupture in the Achilles tendon

Chronic pain in the region of the Achilles tendon is a common problem and often a sign of progressive degeneration of the tendon which may lead to its rupture. We studied the clinical course and sonograms in 36 patients with achillodynia to find a prognostic parameter enabling us to estimate the risk of rupture. The patients were evaluated clinically for swelling and tenderness and by high-resolution real-time sonography. The sonograms were graded according to the tendon thickness as normal (< 6 mm), minimal (6-8 mm), moderate (8-10 mm) to high-grade (> 10 mm) in the sagittal diameter of the transverse section, and alterations of echotexture were described as diffuse, circumscribed, or inhomogenous. At the time of the primary investigation, we found thickening and alterations of the echotexture in 33 of 72 tendons. In 48 tendons we found pain and local or diffuse swelling in the Achilles tendon region (sensitivity 0.58, specificity 0.79). After a follow-up of 48 +/- 8 months, 7 tendons had ruptured spontaneously. Analysis of the sonograms of the patients taken prior to the rupture showed a high-grade thickening in 4 cases, moderate thickening in 2 cases, and a diameter between 6 and 8 nm in one patient. In no case did we find a rupture of a tendon primarily classified as normal. Patients without sonographic changes exhibited a significantly better clinical outcome following conservative treatment. Sonography was found to be a valuable tool for determination of the tendon's thickness and echotexture. In 28% of our patients with thickening, circumscribed lesions of the echotexture, and chronic pain, a spontaneous rupture occurred.

Structural and functional implications of age-related abnormal modifications in collagen II from intervertebral disc

Collagen II was isolated from annulus fibrosus of human donors, and the degree of enzymatic glycosylation and the extent of nonenzymatic modification was determined as a function of age. While enzymatic glycosylation did not alter with age, the fluorescence as a measure of nonenzymatic modification increased, in particular in those fractions containing highly cross-linked collagen molecules. The age-dependent increase of fluorescence was associated with a lower thermal stability of collagen II, being lowest (Tm = 36.9 degrees C instead of 42.1 degrees C) in a fraction of collagen II molecules isolated from tissue of a 69-year-old donor. In addition, collagen II from elderly donors showed an impaired propensity to form fibrils, using an in vitro assay, as evidenced by the facts that (1) more collagen molecules remained in solution and were not assembled into fibrils, and (2) the relative turbidity caused by the aggregates progressively decreased as the age of the donors increased. As seen on electron micrographs, these fibrillar aggregates were less densely packed and intermingled with precipitates such as unbanded filaments or discontinuous fibrils with split and frayed regions. It can be hypothesized that functional impairment of the intervertebral disc with aging may be caused in part by molecular alterations as are described here for collagen II obtained from aged donors.

Achilles tendon injuries in athletes

Two-thirds of Achilles tendon injuries in competitive athletes are paratenonitis and one-fifth are insertional complaints (bursitis and insertion tendinitis). The remaining afflictions consist of pain syndromes of the myotendineal junction and tendinopathies. The majority of Achilles tendon injuries from sport occur in males, mainly because of their higher rates of participation in sport, but also with tendinopathies a gender difference is probably indicated. Athletes in running sports have a high incidence of Achilles tendon overuse injuries. About 75% of total and the majority of partial tendon ruptures are related to sports activities usually involving abrupt repetitive jumping and sprinting movements. Mechanical factors and a sedentary lifestyle play a role in the pathology of these injuries. Achilles tendon overuse injuries occur at a higher rate in older athletes than most other typical overuse injuries. Recreational athletes with a complete Achilles tendon rupture are about 15 years younger than those with other spontaneous tendon ruptures. Following surgery, about 70 to 90% of athletes have a successful comeback after Achilles tendon injury. Surgery is required in about 25% of athletes with Achilles tendon overuse injuries and the frequency of surgery increases with patient age and duration of symptoms as well as occurrence of tendinopathic changes. However, about 20% of injured athletes require a re-operation for Achilles tendon overuse injuries, and about 3 to 5% are compelled to abandon their sports career because of these injuries. Myotendineal junction pain should be treated conservatively. Partial Achilles tendon ruptures are primarily treated conservatively, although the best treatment method of chronic partial rupture seems to be surgery. Complete Achilles tendon ruptures of athletes are treated surgically, because this increases the likelihood of athletes reaching preinjury activity levels and minimises the risk of re-ruptures. Marked forefoot varus is found in athletes with Achilles tendon overuse injuries, reflecting the predisposing role of ankle joint overpronation. Athletes with the major stress in lower extremities have often a limited range of motion in the passive dorsiflexion of the ankle joint and total subtalar joint mobility, which seems to be predisposing factor for these injuries. Various predisposing transient factors are found in about one-third of athletes with Achilles tendon overuse injuries; of these, traumatic factors (mostly minor injuries) predominate. The typical histological features of chronically inflamed paratendineal tissue of the Achilles tendon are profound proliferation of loose, immature connective tissue and marked obliterative and degenerative alterations in the blood vessels. These changes cause continuing leakage of plasma proteins, which may have an important role in the pathophysiology of these injuries. The chronically inflamed paratendineal tissues of the Achilles tendon do not seem to have enough capacity to form mature connective tissue.

Amianthoid fibres in ruptured human tendons

So-called amianthoid fibres were identified in 17 of 460 tendons (3.7%) after spontaneous rupture. These tendons belonged to 10 men and 7 women with an age-range from 18 to 67 years. In 445 postmortem control tendons taken of accidentally killed previously healthy persons amianthoid fibres were not found. Ultrastructurally the tendineal amianthoid fibres differ from normal tendon collagen fibrils in many respects. Their diameter (600-1400 nm) is many times larger than that of native collagen fibrils (20-120 nm). The fibre profile is often irregular and the cross-sectioned fibres have a homogeneous granular appearance. In longitudinal sections, the amianthoid fibres are frequently disintegrated and outspread, and some of the fibres have lost their periodicity. In addition, some of the fibres are angulated and show nonparallel organization. Occasionally the amianthoid fibres are calcified.

Pathological alterations in human tendons

The present authors analyzed the pathological alterations of 1966 tendons examined in the National Institute of Traumatology, Budapest, during the past 18 years. The majority of cases proved to be tendinopathies (hypoxic-degenerative tendinopathy or calcific tendinitis, tendolipomatosis and mucoid degeneration) leading to tendon rupture. The incidence of tendon tumors, foreign bodies, infectious tendon diseases, and other pathological conditions was clearly lower. The methods of tissue preparation and of examination of tendon specimens were also evaluated. Light microscopy was sufficient for the diagnosis of pyogenic tendinitis, tumors, xanthoma, gout, and gangrene. In degenerative tendinopathies and alterations due to hereditary disease, electron microscopy was necessary. Polarization microscopy had a key role in examination of collagen structure and architecture, and identification of foreign bodies in the tendons. Enzyme histochemical and immunohistochemical examination were reliable but not absolutely necessary in the diagnosis of tendon pathology.

Alterations in dry mass content of collagen fibers in degenerative tendinopathy and tendon-rupture

The dry mass concentration and collagen fiber morphology of intact, as well as of degenerated and ruptured human Achilles, biceps brachii, extensor pollicis longus and quadriceps tendons, were determined by using the interference microscopical technique. The variation in the collagen fiber thickness was demonstrated in different intact tendons, the fibers being largest in the Achilles and smallest in the extensor pollicis longus tendons. However, the intact tendons exhibited only thick collagen fibers. In the degenerative tendinopathies an increase of the dry mass content was observed, being especially marked in calcifying tendinopathy. In the degenerated tendons the average collagen fiber diameter had decreased, and two clearly distinct populations of thick and thin fibers were observed. The dry mass content of the thick fibers was significantly greater than that of the thin fibers. The present results demonstrate striking changes in the collagen and its dry mass content in degenerative tendinopathy, thus also increasing the susceptibility to ruptures.