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.

Cortical and trabecular osteopenia after immobilization. A quantitative histological study of the rat knee

The aim of this investigation was to examine the effect of short-term immobilization on subchondral cortical and trabecular bone tissue in the rat tibia and to determine whether there was any difference when the knee was immobilized in extension or flexion. Thirty-six male rats were used in this study, and in 18 the knee was fixed in extension and in 18 in flexion. The time of immobilization was for 1, 2 and 3 weeks, with 12 animals in each group and 6 knees in extension and 6 in flexion. The following parameters were measured: (1) the mean thickness of subchondral and both periosteal cortices; (2) cortical porosity; (3) trabecular bone volume; (4) relative osteoid volume, and (5) relative osteoid surface. The mean cortical thickness decreased during the period of immobilization and the cortical porosity significantly increased. The trabecular bone volume was unaltered in the first week, but after 3 weeks it had decreased. The relative osteoid volume decreased significantly during the three weeks, and the relative osteoid surface moderately increased. No relationship was found between the quantitative osteopenic alteration of subchondral bone and the position of immobilization.

The effect of tenotomy and immobilization on muscle spindles and tendon organs of the rat calf muscles. A histochemical and morphometrical study

The morphological and histochemical alterations in the muscle spindles and Golgi tendon organs of tenotomized or immobilized calf muscles of rats (m. soleus, m. gastrocnemius) were studied in 54 animals. The intact contralateral feet served as controls. There was no change in the number of mechanoreceptors in either the tenotomized or the immobilized muscles. The diameter of the intrafusal fibers was increased somewhat after 1 week, but decreased by 14% to 40% in 3 weeks. The periaxial space of muscle spindle had diminished or disappeared by 2 weeks from the beginning of the procedures. The thickness of the outer capsule of the spindles had markedly increased, especially in the polar region. In the Golgi tendon organs the capsule had also thickened significantly and the internal space diminished. The alterations were similar following tenotomy or immobilization, but more marked after tenotomy than after immobilization.

Macromolecular composition of the sarcolemma and endomysium in the rat

The macromolecular composition of sarcolemma and endomysium was studied by classical staining methods for glycosaminoglycans and using immunological techniques for proteins. Both proteoglycans and glycosaminoglycans (heparan sulphate, dermatan sulphate, chondroitin sulphate) could be detected in the sarcolemma. Type IV and type V collagen and laminin were found exclusively in the sarcolemma and endomysium. Type I and type III collagen as well as fibronectin were detected both in the endomysium and perimysium.

Immunopathological study on palmar aponeurosis in Dupuytren's disease

The authors examined the immunological and immunohistochemical alterations of palmar aponeurosis in Dupuytren's contracture. In the IgG-content no difference were found between the intact and diseased aponeurosis. The mean of IgA content was 2 fold, the IgM content 3 fold higher in Dupuytren's aponeurosis than in normal ones. The immunoglobulin containing cells localised around the Dupuytren's nodules and in fibrotic, but not nodular parts of aponeurosis. Extracellular immunoglobulin deposits were not found.

Regeneration of human tendons after homologous tendon-graft transplantation. A morphological study of 25 cases

The authors examined the regeneration and incorporation of homologous tendon grafts in 25 patients from 10 days to 20 years after tendon grafting. Newly formed collagen fibers in the place of graft are first observed 3 months after transplantation. The reorganization of tendon grafts begins at the end of the first postoperative year and is accomplished within the second year.

Fine structural changes in the articular cartilage of the rat's knee following short-term immobilisation in various positions: a scanning electron microscopical study

The knee joints of 36 rats were immobilised in a padded plaster cast (18 in the flexed and 18 in the extended position) for 1, 2 and 3 weeks. The femoral articular cartilage was then examined under the scanning electron microscope. After 1 week's immobilisation in the flexed position, the surface layer of the cartilage showed disruption and the superficial chondrocytes were necrotic. The sites of the necrotic chondrocytes were seen as pits on the cartilage surface. In the animals whose knees were immobilised in the extended position, the changes were not so great in severity or extent. After 2 weeks, more advanced changes could be detected in both groups, but they were more severe in the flexed group. After 3 weeks the changes in articular cartilage were diffuse in the flexed, but focal in the extended group. Diffuse necrosis of chondrocytes, with pit formation on the surface and disruption and disintegration of the collagen fibres, was seen to some extent in all the animals. In the flexed group the changes extended to the whole weightbearing surface of the articular cartilage of the femur, except the intercondylar sulcus. In the extended group, a superficial fibre network was found without the formation of closely packed collagen fibre bundles, and the changes in the chondrocytes were seen only in localised zones. The authors suggest that during immobilisation, especially in the flexed position, articular hypoxia occurs due to a decreased amount of synovial fluid, the increased compression of the cartilage surfaces and the increased intra-articular pressure. This causes degeneration and necrosis of the superficial chondrocytes and the superficial cartilage layer.

Chronic Achilles paratenonitis in athletes: a histological and histochemical study

Pathological alterations of chronic Achilles paratenonitis were studied histologically and histochemically in tissue samples obtained operatively from 16 athletes with this complaint and from 3 control patients. The activities of 11 different enzymes--lactate, succinate, malate, glucose-6-phosphate and glutamate dehydrogenases, lipoamide dehydrogenase and glutathione reductase (NADH2- and NADPH2-diaphorases), acid and alkaline phosphatases, phosphorylase and leucylaminopeptidase--were studied. Pathological findings were located diffusely around the tendon. A slight inflammatory cell reaction was found in all cases. The fatty areolar tissue was clearly thickened and edematous, and showed fibrinous exudations, widespread fat necrosis, considerable connective tissue proliferation and adhesion formation. The blood vessels showed profound degenerative and necrotizing changes. The thin membranes of the paratenon were clearly hypertrophied. Increased enzyme activities were mainly found in the fibroblasts, inflammatory cells and vascular walls. A moderate activity of lysosomal enzymes, an increased activity of enzymes of electron transport, anaerobic glycolysis, pentose phosphate shunt and decreased activity of those of aerobic energy metabolism were found. Simultaneously an increased amount of both neutral and acid mucopolysaccharides and a locally increased amount of elastic fibres were found in the inflamed paratenon. These results indicate that marked metabolic changes occur in paratenonitis, i.e. an increased catabolism and decreased oxygenation of the inflamed areas. The morphological alterations suggest that the gliding function of the paratenon may be impaired.

[Experimental reconstruction of flexor tendon injuries with a free transplant tendon-tendon sheath unit]

The authors, in their experiments on chickens, imitate human "no man's land" flexor tendon injuries of bad prognosis. For reconstruction of gliding surfaces they transplanted composite flexor tendon grafts containing flexor tendons with their sheath, pulleys, and vincula. Autologous grafts were compared with homologous composite tendon grafts preserved in beta-propiolacton. Summarizing the results of macroscopic and light microscopic examinations they state that the tendon sheath of the autologous composite tendon grafts revitalize in two weeks, and their tissue structure remains practically intact. The composite tendon allografts conserved in beta-propiolacton on the contrary rebuild much more slowly, on the average over three months. Regeneration is accompanied by round-cell infiltration. In the case of the autogenous graft generally smaller, and in the case of homologous composite flexor tendon graft more multitudinous adhesions occurred between flexor tendon and tendon sheath. The authors conclude from the literature and their own results that the reconstruction of flexor tendons with autologous composite flexor tendon grafts is a proper method for the restoration of severe flexor tendon injuries. Before clinical use, homologous composite flexor tendon grafts require more experimental investigation.

Fine structural alterations in chronic Achilles paratenonitis in athletes

The fine structural alterations in chronic Achilles paratenonitis were studied in tissue samples obtained from 14 athletes, who were operated on for this complaint and from 3 patients without any history of this disease. In the chronically inflamed paratendineal tissue mainly two types of cells were identified: classic fibroblasts with a smooth and rough endoplasmic reticulum and only a few mitochondria and lysosomes and myofibroblast-like cells with cytoplasmic microfilaments 5-6 nm in diameter, a rough endoplasmic reticulum, some mitochondrias and free ribosomes. These cells represented 19% of 471 studied non-inflammatory cells. In the extracellular space there was an increased amount of fibrils regarded as either type I or type III collagen as sign of tissue repair. Especially around the myofibroblastic cells a fine granular ground substance was found. The amount of ground substance was as a rule increased in pericellular space. Due to the capacity of contraction in healing tissue the myofibroblasts apparently have a role in the clinical symptoms of chronic Achilles paratenonitis.

Recapillarization of tenotomized skeletal muscles after delayed tendon suture. I. Experimental study

The investigation was under taken to study the long-term effect of tendon suturing on the capillarization of guinea-pig crural muscle after Achilles tenotomy. The results indicate that the capillary density has been greatly decreased by the tenotomy. The recapillarization and the time of restitution of the crural muscle are influenced by the interval between tenotomy and tendon suture.

The pathogenesis of tendolipomatosis; an electron microscopical study

The development of tendolipomatosis has been studied both by light and scanning electron microscopy in the tendons of healthy persons killed in accidents. Lipid cells are rarely seen in the intact tendon. In the early stages of tendolipomatosis lipid cells are found deep and singly but in the later phases lipocytes are seen to disrupt the continuity of collagen fibres and tendon bundles and so reduce the strength of the tendon.

Fine structural alterations of collagen fibers in degenerative tendinopathy

Fine structural alterations of collagen fibers were analyzed in 29 ruptured tendons. The most frequent alterations were longitudinal splitting, disintegration, angulation, and the so-called "Knickdeformation" of the collagen fibers. All these phenomena were considered to be the consequences of stress fatigue and mechanical injuries of fibers.