[Diseases of tendons, tendon sheaths and bursae (author's transl)].
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Adult↗
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[Studies of the pathology of tendons and synovial bursae. IV. Xanthogranuloma of the tendon sheaths and rheumatoid tenosynovitis].
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Adult↗
The Golgi tendon organ. Properties of the receptor and reflex action of impulses arising from tendon organs.
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Afferent Pathways↗
[Patellar tendon bearing plaster cast. Patellar tendon bearing or PTB plaster cast --technic and indications].
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Adolescent↗
Histopathological findings in chronic tendon disorders.
Tendon injuries and other tendon disorders represent a common diagnostic and therapeutic challenge in sports medicine, resulting in chronic and long-lasting problems. Tissue degeneration is a common finding in many sports-related tendon complaints. In the great majority of spontaneous tendon ruptures, chronic degenerative changes are seen at the rupture site of the tendon (1). Systemic diseases and diseases specifically deteriorating the normal structure of the tendon (i.e. foreign bodies, and metabolic, inherited and infectious tendon diseases) are only rarely the cause of tendon pathology. Inherited diseases, such as various hereditary diseases with disturbed collagen metabolism and characteristic pathological structural alterations (Ehlers-Danlos syndrome, Marfani syndrome, homocystinuria (ochronosis)), represent approximately 1% of the causes of chronic tendon complaints (2), whereas foreign bodies are somewhat more common and are found in less than 10% of all chronic tendon problems (1). Rheumatoid arthritis and sarcoidosis are typical systemic diseases that cause chronic inflammation in tendon and peritendinous tissues. Altogether, these 'specific' disorders represented less than 2% of the pathological alterations found in the histological analysis of more than 1000 spontaneously ruptured tendons (1, 3, 4). In this material, degenerative changes were seen in a great majority of the tendons, indicating that a spontaneous tendon rupture is a typical clinical end-state manifestation of a degenerative process in the tendon tissue. The role of overuse in the pathogenesis of chronic tendon injuries and disorders is not completely understood. It has been speculated that when tendon is overused it becomes fatigued and loses its basal reparative ability, the repetitive microtraumatic processes thus overwhelming the ability of the tendon cells to repair the fiber damage. The intensive repetitive activity, which often is eccentric by nature, may lead to cumulative microtrauma which further weakens the collagen cross-linking, non-collagenous matrix, and vascular elements of the tendon. Overuse has also been speculated to cause chronic tendon problems, by disturbing the micro- and macrovasculature of the tendon and resulting in insufficiency in the local blood circulation. Decreased blood flow simultaneous with an increased activity may result in local tissue hypoxia, impaired nutrition and energy metabolism, and together these factors are likely to play an important role in the sequence of events leading to tendon degeneration (4). A sedentary lifestyle has been proposed as a main reason for poor basal circulation of the tendon, and presumably is at least partly responsible for the high number of tendon problems in people with a sedentary lifestyle who occasionally take part in high physical activity sports events.
Humans↗
Insulin-like growth factor-I is expressed by avian flexor tendon cells.
Cells in normal tendon are in a resting G0 state, performing maintenance functions. However, traumatic injury introduces growth factors such as platelet-derived growth factor and insulin-like growth factor from blood as well as activates endogenous growth factors. These factors stimulate migration and proliferation of tendon cells at the wound area. Tendon cells require growth-promoting factors to transit the cell cycle. To evaluate the contribution of endogenous growth factors in tendon, extracts of the epitenon and internal compartment of avian flexor tendon as well as medium of cultured cells from the epitenon (tendon surface cells) and internal tendon (tendon internal fibroblasts) were collected to assess their ability to stimulate DNA synthesis. Acid-ethanol extracts of tissues and medium were chromatographed on a P-30 molecular sieve column and assayed for mitogenic activity by quantitating [3H]thymidine incorporation into tendon cell DNA. The extract from the internal tendon compartment was more stimulatory for DNA synthesis than that from the epitenon, particularly when tested on tendon internal fibroblasts. However, conditioned medium fractions from surface epitenon cells stimulated DNA synthesis to a high degree on both tendon surface cells and tendon internal fibroblasts. Conditioned medium from tendon internal fibroblasts was also stimulatory. An anti-insulin-like growth factor-I antibody ablated most of the mitogenic activity present in both tissues and conditioned medium. The levels of acid-extractable insulin-like growth factor-I in tendon were determined by competitive radioimmunoassay as 1.48+/-0.05 ng/g tissue for the epitenon and 3.83+/-0.03 ng/g tissue for the internal compartment. Results of Western immunoblots of conditioned medium revealed insulin-like growth factor-I at the 7.5 kDa position. Cultured tendon surface cells and tendon internal fibroblasts as well as cells in intact flexor tendon expressed insulin-like growth factor-I mRNA detected by reverse transcriptase-polymerase chain reaction. In situ hybridization histochemistry positively identified insulin-like growth factor-I mRNA in tendons from 52-day-old chickens. Platelet-derived growth factor was not detected at the protein or message levels. Furthermore, tendon surface cells and tendon internal fibroblasts both expressed receptors for insulin-like growth factor-I detected by flow cytometry. These data suggest that tendon cells express insulin-like growth factor-I mRNA and synthesize insulin-like growth factor-I in both the epitenon and the internal compartment of tendon, which is present in an inactive form, most likely bound to insulin-like growth factor-binding proteins.
Animals↗
Role of the muscle belly and tendon of soleus, gastrocnemius, and plantaris in mechanical energy absorption and generation during cat locomotion.
The functional significance of tendons, and the differences in tendon properties among synergistic muscles, is not well established for normal locomotion. Previous studies have suggested that tendons may store mechanical energy during the early phase of support, and then release this energy during the late phase of support. The storage and release of mechanical energy by tendons may modify the velocity of shortening and elongation and the power produced by the muscle belly and the fibers, and may influence the metabolic cost of locomotion. The aims of this study were (1) to estimate the amount of negative and positive work done by the tendon and the muscle belly of the cat soleus (SO), gastrocnemius (GA), and plantaris (PL), and (2) to determine the relative contribution of the elastic energy stored in the tendons to the total mechanical work done by these three muscles during walking and trotting. Forces of SO, GA, and PL muscles were measured using standard force transducers in three cats walking and trotting at speeds of 0.4-1.8 ms-1 on a motor-driven treadmill. Video records and a geometrical model of the cat hindlimb were used for calculating length of the muscle-tendon complexes of SO, GA, and PL during locomotion. Instantaneous lengths of the tendons of SO, GA, and PL during a step cycle were estimated from the stress-strain properties, the effective lengths, the cross-sectional areas, and the instantaneous forces of the tendons. Stress-strain properties for the tendons were obtained experimentally from one animal. The length of the belly was defined as the difference between the muscle-tendon complex length and the tendon length. Mechanical power of the tendon and the muscle belly was calculated as the product of the measured muscle force and the calculated rates of change in tendon and muscle belly lengths, respectively. Mechanical power and work of the tendons and bellies of SO, GA, and PL were calculated for 144 step cycles. During a step cycle, peak negative and peak positive velocities as well as peak powers of the muscle-tendon complexes of SO, GA, and PL were typically higher than those of the muscle bellies. Positive work done by the muscle-tendon complexes exceeded the positive work done by the muscle bellies. GA and PL tendons stored more mechanical energy than the SO tendon. The contributions of the elastic energy stored in the tendons to the positive work done by the muscle-tendon complexes decreased with increasing speeds of locomotion for two of the three cats studied and did not change for the third one. These contributions equaled 50-21%, 30-14%, and 25-18% for the three cats, respectively. The results of this study suggest that energy absorption and release by the tendons of cat SO, GA, and PL make up a substantial part of the total energy absorbed and generated by the corresponding muscle-tendon complexes.
Absorption↗
Glycosaminoglycans of human rotator cuff tendons: changes with age and in chronic rotator cuff tendinitis.
OBJECTIVES: To analyse the glycosaminoglycans of the adult human rotator cuff tendon matrix, to characterise changes in the glycosaminoglycan composition with age and in chronic rotator cuff tendinitis. METHODS: Rotator cuff (supraspinatus) tendons (n = 84) and common biceps tendons (n = 26) were obtained from cadavers with no history of tendon pathology (age range 11-95 years). Biopsies of rotator cuff tendons (supraspinatus and subscapularis tendons, n = 53) were obtained during open shoulder surgery to repair shoulder lesions (age range 38-80 years). Glycosaminoglycans were extracted by papain digestion and analysed by cellulose acetate electrophoresis, the carbazole assay for uronic acid and the dimethylmethylene blue dye-binding assay for sulphated glycosaminoglycans. Some digests were analysed for keratan sulphate by 5D4 monoclonal antibody ELISA. Soluble proteoglycans were extracted in 4M guanidine hydrochloride and analysed by 4-15% SDS PAGE. RESULTS: The mean (SD) sulphated glycosaminoglycan (GAG) content of the normal cadaver supraspinatus tendon was 12.3 (4.3) micrograms/mg dry weight, between three and ten times greater than in the common biceps tendon [1.2 (0.6) micrograms/mg dry weight]. The major GAG was chondroitin sulphate [6.9 (2.6) micrograms/mg dry weight], with a smaller proportion of dermatan sulphate [2.5 (1.2) micrograms/mg dry weight]. In contrast, the common biceps tendon contained predominantly dermatan sulphate [0.8 (0.2) microgram/mg dry weight] with less chondroitin sulphate [0.2 (0.2) microgram/mg dry weight]. There was no difference in the concentration of hyaluronan in these tendons [9.3 (2.8) micrograms/mg dry weight and 10.8 (4.3) micrograms/mg dry weight respectively] and there was no significant change of hyaluronan with age. Keratan sulphate was a small but significant component of the supraspinatus tendon [0.43 (0.33) microgram/mg dry weight, n = 25], whereas there was little or none in the common biceps tendon [0.04 (0.05) microgram/mg dry weight, n = 8] and there was no significant change across the age range. In the supraspinatus tendon, there was a significant decrease in total glycosaminoglycan, chondroitin sulphate and dermatan sulphate with age (p < 0.001), whether expressed relative to the tendon dry weight or total collagen content, and no change in the relative proportion of the different GAG types. There was, however, a large degree of variation within the samples. Supraspinatus tendons from patients with chronic tendinitis had a significantly increased concentration of hyaluronan [30.4 (10.1) micrograms/mg dry weight, p < 0.001], chondroitin sulphate [8.4 (1.8) micrograms/mg dry weight, p < 0.05] and dermatan sulphate [3.8 (1.1) micrograms/mg dry weight, p < 0.001] compared with normal cadaver supraspinatus tendons, although the keratan sulphate content was not significantly different [0.18 (0.05) microgram/mg dry weight]. CONCLUSIONS: The normal supraspinatus tendon has the proteoglycan/glycosaminoglycan of tendon fibrocartilage, which it is suggested is an adaptation to mechanical forces (tension, compression and shear) which act on the rotator cuff tendons in the shoulder, although other factors such as reduced vascularity, low oxygen tension and the influence of local growth factors may also be important. This functional adaptation may have important consequences for the structural strength of the supraspinatus tendon and to influence the ability of the tendon to repair after injury. The glycosaminoglycan composition of tendon specimens from patients with chronic tendinitis is consistent with acute inflammation and new matrix proteoglycan synthesis, even in relatively old tendon specimens and after at least one injection of corticosteroid.
Adolescent↗
Tendon involvement in pedal infection: MR analysis of frequency, distribution, and spread of infection.
OBJECTIVE: The objective of our study was to evaluate the frequency, distribution, and extent of tendon involvement in patients with pedal infections. MATERIALS AND METHODS: Contrast-enhanced MR imaging examinations of 159 infected feet performed at 1.5 T were reviewed by two musculoskeletal radiologists for the presence and location of tendon infection (peritendinous enhancement contiguous to an adjacent ulcer or cellulitis) and for the spread of infection along tendons, which was defined as peritendinous contrast enhancement extending more than 2 cm beyond surrounding cellulitis. The study group was composed of 156 consecutive patients, 82.7% of whom had diabetes; all patients underwent subsequent surgical treatment. Results of MR evaluations were compared with the patients' charts and surgical reports. RESULTS: Of the 129 MR examinations showing an infection in the forefoot, MR evidence of tendon involvement in the infection was observed in 56 MR examinations (43%). The sum of involved tendons per ray was as follows: first ray (flexor tendon, n = 19; extensor tendon, n = 13), second (flexor tendon, n = 12; extensor tendon, n = 7), third (flexor tendon, n = 5; extensor tendon, n = 4), fourth (flexor tendon, n = 5; extensor tendon, n = 1), and fifth (flexor tendon, n = 11; extensor tendon, n = 6). Of the 32 MR examinations showing infection in the hindfoot, 14 examinations (44%) showed evidence of tendon involvement, most frequently of the distal Achilles tendon (n = 7). MR evidence of the spread of infection along a tendon was seen in 12 examinations, always with proximal spread of infection; and infection led to the development of an abscess in the central plantar compartment in three patients. Intraoperative evidence of a tendon infection was documented in 11 patients. The surgical procedure was altered because of the tendon infection in six patients. CONCLUSION: MR evidence of tendon infection is present in approximately half the patients who require surgery for pedal infection. Evidence of spread of the infection along tendons is seen infrequently on MR imaging. Detection of a tendon infection could influence surgical therapy.
Adult↗
Femoral press-fit fixation of the hamstring tendons for anterior cruciate ligament reconstruction.
BACKGROUND: Press-fit fixation of patellar tendon-bone anterior cruciate ligament autografts is an interesting technique because no hardware is necessary. For hamstring tendon grafts, no biomechanical data exist of a press-fit procedure. HYPOTHESIS: Press-fit femoral fixation of hamstring tendons is mechanically equivalent to press-fit patellar tendon-bone fixation. STUDY DESIGN: Controlled laboratory study. METHODS: Patellar and hamstring tendons of 30 human cadavers (age, 53.8 +/- 18.0 years) were used. An outside-in press-fit fixation with a knot in the semitendinosus and gracilis tendons and an inside-out and outside-in fixation with the tendons wrapped around a bone block were compared with patellar tendon-bone press-fit fixation in 30 ovine femora. Constructs were cyclically strained and then loaded until failure. Maximum load to failure, stiffness, and elongation during failure testing and cyclical loading were investigated. RESULTS: The maximum load to failure was 561 +/- 309 N for the patellar tendon, 599 +/- 234 N for the semitendinosus/gracilis tendons knot construct, 678 +/- 231 for the semitendinosus/gracilis tendons bone construct inserted outside in, and 339 +/- 236 for the semitendinosus/gracilis tendons bone construct inserted inside out (inferior to the others; analysis of variance, Dunn test, P < .01). Stiffness of the constructs averaged 134 +/- 32 N/mm for the patellar tendon, 124 +/- 21 N/mm for the knot construct, 118 +/- 27 N/mm for the outside-in fixation, and 117 +/- 23 N/mm for inside-out fixation. Elongation during initial cyclical loading was 0.7 +/- 0.6 mm for the patellar tendon, 1.6 +/- 0.5 mm for the knot construct, 1.9 +/- 1.2 mm for the outside-in fixation, and 1.9 +/- 0.9 mm for the inside-out fixation (significantly larger for all semitendinosus/gracilis tendon techniques, P < .05). CONCLUSIONS: Failure loads for the semitendinosus/gracilis tendons bone construct inserted outside in and the semitendinosus/ gracilis tendons knot construct were within the confidence interval of the patellar tendon press-fit fixation. All semitendinosus/ gracilis tendon graft techniques exhibited larger elongation during initial cyclical loading than the patellar tendon graft. There was no difference in stiffness between all techniques. CLINICAL RELEVANCE: Two of the 3 hamstring press-fit fixation techniques showed loads to failure similar to the patellar tendon fixation. Preconditioning of the constructs is critical. These results must be interpreted with care because of high standard deviations.
Adolescent↗
[Liquid silicones in reconstructive surgery of the tendons. Experimental studies].
The results of reconstruction of flexor tendons of the hand are not satisfactory despite many operative methods. Since 70 years different surgical methods were described from which only some found application and some are tested up to day. The classical surgical methods do not prevent adhesions of tendons to the surrounding tissues. Therefore studies were undertaken to proof the usefullnes and the specific properties of silicone fluids in the reconstructive tendon surgery. Examinations were done on 48 mongrel rabbits of both sexes on surgically exposed tendon of the gastrocnemius muscle. The animals were divided into two groups. In group I the tendon of the right extremity was covered with Medical Fluid 360, and in group II - with Silol F 350. Each group was divided into two subgroups. In subgroups IA and IIA the tendinous sheath was removed whereas in subgroups IB and IIB the tendon was also cut and sutured. The silicone fluids were spread in amount up to 1 ccm, and uniform coat on tendon surface resulted. On the left tendons 0.9% natrium chloride solution was spread for control. In both groups the dissections were performed 14, 30, 90, 180 days after the operation. The following criteria were applied to evaluate the results: - the appearance of extremities, the range of motility in knee and ankle joint, wound healing, - the macroscopic appearance of isolated tendons, - the degree of excursion measured in millimeters, - the appearance and degree of adhesion between the tendon and surrounding tissues. 800 histological preparations were made. They were evaluated in biological microscope with special attention to the dimension of tissue reaction. In histological examinations the differences in tissue reaction were stated between subgroups A and B of both groups. However, no differences were found dependent from the applied silicone in groups I and II. In the early period, around the siliconized tendon poorly cellular, not significant exudative reaction was found. This reaction changed afterwards into proliferative one, which led to the development of a new tendon sheath. These changes did not discriminate distinctly the flexibility of the examined tendon. After applying 0.9% natrium chloride solution to uncovered tendon (control), adhesions of the tendon to surroundings were observed, which resulted in discrimination of tendon's flexibility. It was proved that silicone fluids applied to the sutured tendon (groups IB and IIB) did not handicap the healing process. The peritendinous adhesions were more intensive around the tendon's anastomosis than in the remaining tendon part. These adhesions were significantly smaller in comparison with the control extremities whose tendons were covered by0.9% natrium chloride solution. The application of small quantity of silicone fluids according to both up to day and own investigations do not cause local or general pathological changes...
Achilles Tendon↗
Flexor digitorum profundus tendon to bone tunnel repair: a vascularization and histologic study in canines.
PURPOSE: Recent in vivo canine studies have shown incomplete restoration of the flexor digitorum profundus (FDP) insertion site after transection and repair to the cortical surface of the distal phalanx. Previous biomechanical analyses of tendon to bone surface repair have suggested that repair site gap formation of greater than 3 mm occurs frequently under physiologic loads. A recent ex vivo investigation into a novel repair of the FDP tendon into a bone tunnel in the distal phalanx showed improved tensile properties with a decrease in repair site gap formation. Time-zero data, however, do not always accurately reflect in vivo responses. The repair response of the FDP tendon when placed in an osseous compartment is not known. The purpose of this study was to analyze the histologic and vascular anatomic properties of the FDP insertion site after transection and repair in a bone tunnel within the distal phalanx. METHODS: Twenty-six FDP tendon to bone repairs were performed in 13 adult mongrel dogs after insertion site transection. The tendons were repaired in a bone tunnel in the distal phalanx. Vascular analysis of the tendon and repair site was performed by using a modified Spalteholtz technique and routine hematoxylin-eosin staining was used to assess histologic properties of the repair. RESULTS: In normal specimens the vascular analysis showed that there was a distal network of vessels extending 1- to 2-cm proximal to the FDP insertion site. At 10 days after repair the distal tendon segment tendon remained avascular. By 21 days after repair there was proximal migration of an unorganized reticular network of tendon surface vessels with sparse intratendinous communications. At 6 weeks after repair the structure of the distal tendon vascular network resembled that of normals. The vascular response of the tendon within the bone tunnel followed a similar time frame. Histologic analysis showed an inflammatory reaction in the bone tunnel leading to a progressive degradation of that portion of the FDP tendon that resided in the tunnel. Tendon necrosis was not seen. CONCLUSIONS: The FDP tendon, after insertion site transection and repair in a bone tunnel, undergoes a process of neovascularization and revascularization over a period of 6 weeks. There is a progressive loss of tendon parenchyma within the bone tunnel and the suture tracks appeared to serve as conduits for the ingrowth of inflammatory tissue. Restoration of the normal 4-zone tendon-bone interface was not seen. Although ex vivo biomechanical assessment of tendon repair in a bone tunnel appears promising, the repair response in vivo may not be favorable for tendon to bone healing. The progressive tendon degeneration that was observed here may have detrimental effects on repair site tensile properties, increasing the potential for early failure.
Animals↗
An experimental study of healing of the partially severed flexor tendon in chickens.
There is a lack of clinical and experimental studies of the treatment of incompletely transected tendons. The controversy concerning the source of flexor tendon nutrients is of important clinical concern in healing of the injured tendon; thus, the flexor tendon blood supply has cited as a reason for using specific tendon suture techniques, and as a rationale for preserving the superficialis tendon and its vincula during tendon repair surgery. Our knowledge of the normal physiology of digital flexor tendons and the mechanism of their healing process is deficient. The aim of this study was to investigate the relative importance of the synovial fluid and the blood supply respectively for the healing of partially severed flexor tendons. We observed the sequential histological and vascular changes which occur in healing of the partial lacerations in the dorsal and plantar aspects of the tendons. We observed the vascularities of the two partially severed tendon groups after injection of microfil and india ink through the femoral artery. In the healing process there was no sequential histological difference between the dorsal and the plantar severed tendons. The vascularity patterns of the healing tendons were significantly increased and the hypervascularity of dorsal severed tendons was greater than that of plantar severed tendons. Partially severed tendons were completely healed without surgical repair with dense collagen fibers without adhesion in most cases. We concluded from this study that the blood vessels appeared to play a significant role in the healing of the severed flexor tendons. An intact synovial environment did not seem to be required for healing of the severed tendon. It is not necessary to surgically repair the partially severed tendon for prevention of rupture and adhesion.
Animals↗
Mechanical properties of the human achilles tendon.
OBJECTIVE: To determine whether the human Achilles tendon has higher material properties than other tendons and to test for strain rate sensitivity of the tendon. DESIGN: Mechanical testing of excised tendons. BACKGROUND: While the human Achilles tendon appears to experience higher in vivo stresses than other tendons, it is not known how the Achilles tendon's material properties compare with the properties of other tendons. METHODS: Modulus, failure stress, and failure strain were measured for excised human Achilles tendons loaded at strain rates of 1% s(-1) and 10% s(-1). Paired t-tests were used to examine strain rate effects, and average properties from grouped data were used to compare the Achilles tendon's properties with properties reported in the literature for other tendons. RESULTS: Failure stress and failure strain were higher at the faster strain rate, but no significant difference in modulus was observed. At the 1% s(-1)rate, the mean modulus and failure stress were 816 MPa (SD, 218) and 71 MPa (SD, 17), respectively. The failure strain was 12.8% (SD, 1.7) for the bone-tendon complex and 7.5% (SD, 1.1) for the tendon substance. At the 10% s(-1) rate, the mean modulus and failure stress were 822 MPa (SD, 211) and 86 MPa (SD, 24), respectively. The mean failure strain was 16.1% (SD, 3.6) for the bone-tendon complex and 9.9% (SD, 1.9) for the tendon substance. These properties fall within the range of properties reported in the literature for other tendons. CONCLUSIONS: The material properties of the human Achilles tendon measured in this study are similar to the properties of other tendons reported in the literature despite higher stresses imposed on the Achilles tendon in vivo.
Achilles Tendon↗
The role of vasculature and angiogenesis for the pathogenesis of degenerative tendons disease.
More than 100 years ago Wilhelm Roux (1895) introduced the term "functional adaptation to anatomy and physiology". Compared with other organ systems the functional adaptation processes are best identifiable in the locomotor system, like for example in the two types of tendons: traction and gliding tendons. Traction tendons are tendons where the direction of pull is in line with the direction of the muscle (e.g. Achilles tendon). Gliding tendons (e.g. tibialis posterior tendon) change direction by turning around a bony or fibrous hypomochlion. In this region the tendon is subjected to intermittent compressive and shear forces and the extracellular matrix consists of avascular fibrocartilage. Avascularity is considered to be a key factor for the etiology of degenerative tendon disease. The repair capability after repetitive microtrauma is strongly compromised in avascular tissue of gliding tendons. Reduced vascularity is not a specific feature of gliding tendons; several studies have shown that the number and size of blood vessels are largely shortened in the waist of the Achilles tendon. However, histological biopsies from degenerated Achilles tendons and Doppler flow examinations revealed a high blood vessel density in patients with degenerative tendon disease. Angiogenesis is mediated by angiogenic factors and recent studies have shown that the vascular endothelial growth factor (VEGF) is highly expressed in degenerative Achilles tendons, whereas VEGF expression is nearly completely downregulated in healthy tendons. Several factors are able to upregulate VEGF expression in tenocytes: hypoxia, inflammatory cytokines and mechanical load. Since VEGF has the potential to stimulate the expression of matrix metalloproteinases and inhibit the expression of tissue inhibitors of matrix metalloproteinases tissue inhibitor of metalloproteinases (TIMP) in various cell types (e.g. endothelial cells, fibroblasts, chondrocytes), this cytokine might play a significant role for the pathogenetic processes during degenerative tendon disease. An animal experiment in the rabbit has shown that local injection of VEGF reduced the material properties of the Achilles tendon. These experimental findings are in accordance with clinical results that a locally administered (in the area with neovascularization) sclerosing drug (Polidocanol) has a beneficial effect on chronic mid-portion Achilles tendinosis. In conclusion, decreased and increased vascularity might be involved in the pathogenesis of degenerative Achilles tendon disease.
Achilles Tendon↗
The influence of cross-sectional area on the tensile properties of flexor tendons.
Clinicians have long noted substantial variation in the cross-sectional size of flexor tendons in the hand; however, data indicating that surgical repair techniques of lacerated flexor tendons should be altered according to size are unavailable. Our objectives were to evaluate the cross-sectional size differences among tendons within the same hand and to correlate tendon size with tensile mechanical properties after suture repair. Fifty human cadaver flexor digitorum profundus tendons were measured with digital calipers to determine radioulnar and volardorsal diameters. Twenty tendons were used to measure resistance to suture pull-through; tendons were transected at the A2 pulley, and a transverse double-stranded 4-0 Supramid suture (S. Jackson, Inc, Alexandria, VA) was passed through the radioulnar plane of the tendon 1 cm from the transection site. The remaining tendons were transected and repaired by using a modified Kessler repair with double-stranded 4-0 Supramid suture. Both tendon repairs and tendon-suture pull-through specimens were tested to failure in tension by using a material testing machine. Dorsovolar tendon height and tendon cross-sectional area varied significantly between digits, with an average difference of approximately 40% between the values of the smallest (fifth) and largest (third) fingers. Yield and ultimate force determined by pull-through tests of the simple transverse suture correlated positively with tendon radioulnar width. Tensile properties of tendons repaired with a double-stranded modified Kessler repair, however, did not depend significantly on tendon size. These results indicate that the strength of the commonly used Kessler suture technique is not dependent on tendon cross-sectional size within the clinically relevant range of tendons evaluated.
Humans↗
Sonographic differentiation of digital tendon rupture from adhesive scarring after primary surgical repair.
PURPOSE: After the surgical repair of finger tendons finger range of motion may be limited by tendon rupture or adhesive scarring. Differentiating tendon rupture from adhesive scarring may be difficult clinically. Digital tendon sonography allows the evaluation of tendon integrity in a dynamic setting. Our objective was to determine if sonography could differentiate tendon rupture from adhesive scarring in patients who have had primary tendon repair. METHODS: A retrospective review was performed of the radiographic, clinical, and surgical records of patients referred for finger sonography over a 2-year period. Twenty-eight digits in 21 patients were evaluated for finger tendon disruption after primary surgical repair. The diagnosis of complete tendon rupture was made when 1 or more of the following was identified: a gap separating the proximal and distal tendon margins, visualization of only the proximal tendon margin, or visualization of only the distal tendon margin. Adhesive scarring was diagnosed if the tendon appeared intact with abnormal peritendinous soft tissue abutting or partially encasing the tendon, with synovial sheath thickening, or with restricted tendon motion during dynamic evaluation. RESULTS: Sonography correctly identified tendon rupture or adhesive scarring in 27 of 28 digits with 1 false-positive case (sensitivity, 100%; specificity, 93%; positive-predictive value, 93%; negative-predictive value, 100%; accuracy, 96%). CONCLUSIONS: Sonography is an accurate modality for differentiating tendon rupture from adhesive scarring in patients with prior surgical tendon repair. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic, Level I.
Adolescent↗
Tensile properties of the in vivo human gastrocnemius tendon.
In the present experiment we obtained the tensile properties of the human gastrocnemius tendon, a high-stressed tendon suitable for spring-like action during locomotion. Measurements were taken in vivo in six men. The gastrocnemius tendon elongation during tendon loading-unloading induced by muscle contraction-relaxation was measured using real-time ultrasonography. Tendon forces were calculated from the moment generated during isometric plantarflexion contraction, using tendon moment arm length data obtained in vivo with the tendon travel method. Tendon stiffness data were calculated from the slope of the tendon force-elongation curve, and were then normalized to the tendon's original dimensions, obtained from morphometric analysis of sonographs, to estimate the tendon Young's modulus. Mechanical hysteresis values were obtained from area calculations by numerical integration. The elongation of the tendon increased curvilinearly with the force acting upon it, from 1.7+/-1mm (0.8+/-0.3% strain) at 87.5+/-8.5 N to 11.1+/-3.1mm (4.9+/-1% strain) at 875+/-85 N. The tendon Young's modulus and mechanical hysteresis were 1.16+/-0.15 GPa and 18+/-3%, respectively. These values fall within the range of values obtained from in vitro experiments and are very similar to the respective values recently obtained from in vivo measurements in the less highly stressed human tibialis anterior tendon (1.2 GPa and 19%), thus indicating that the material properties of tendon are independent of physiological loading and function. Combining the present tendon force-elongation data with previously reported Achilles tendon force data recorded during walking indicates that the gastrocnemius tendon would provide approximately 6% of the total external work produced by the locomotor system. This estimate illustrates the contribution of passive elastic mechanisms on the economy and efficiency of walking. The contributions would be greater in more active exercise such as running.
Achilles Tendon↗