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PubMed1999

Age-related changes to the molecular and cellular components of equine flexor tendons.

Specific tendons show a high incidence of partial central core rupture which is preceded by degeneration. In the performance horse, the superficial digital flexor tendon (SDFT) is most often affected. We have described previously the molecular changes that are associated with degeneration in the central core region of the equine SDFT. The pathophysiological mechanism leading to change in synthetic activity of central zone cells in degenerated tendons is not known. In this study, we test the hypothesis that ageing results in matrix composition changes within the central zone of the SDFT. Extracellular matrix composition and cellularity were analysed in equine SDFTs collected from Thoroughbred horses and compared with a flexor tendon which rarely shows degenerative change and subsequent injury (deep digital flexor tendon, DDFT). Data were examined for age-related changes to central and peripheral zone tissue of the SDFT and DDFT. Ageing in both tendons (SDFT and DDFT) resulted in a significant increase in collagen-linked fluorescence and a decrease in cellularity in the DDFT but not the SDFT. The central zone tissue from the SDFT had a significantly higher proportion of type III collagen than the peripheral zone of the tendon. The highest level of type III collagen was found in the central zone tissue of the SDFT from the older group of horses and this may represent the early stages of a degenerative change. Collagen content did not differ between the 2 flexor tendons; however, there were differences in collagen type and organisation. The SDFT had a higher type III collagen content, higher levels of the mature trifunctional collagen crosslink hydroxylysylpyridinoline, lower total chondroitin sulphate equivalent glycosaminoglycan content, smaller diameter collagen fibrils and a higher cellularity than the DDFT. In conclusion, differences in macromolecular composition exist between the flexor tendons and ageing contributes to a tendon specific change in composition.

Aging↗
PubMed1992

Normal anatomy and pathologic conditions of ankle tendons: current imaging techniques.

Radiologic assessment of tendon injuries requires familiarity with normal anatomy and the capabilities of available imaging modalities. Tenography, less commonly used nowadays, does not allow direct visualization of tendons, so that partial ruptures and longitudinal splits may go undetected. Ultrasonography can depict tenosynovitis, tendinitis, and complete tendon rupture of the Achilles tendon, but the other tendons are difficult to visualize with this technique. Magnetic resonance (MR) imaging is superior to computed tomography (CT) in the depiction of tenosynovitis and peritendinitis, tendinitis, tendon rupture, and tendon dislocation and subluxation. CT can demonstrate these abnormalities, but accompanying scar tissue or edema, early changes of tendon degeneration, and small amounts of inflammatory fluid are difficult to differentiate with this technique. CT is superior for demonstrating calcifications, convex retromalleolar groove, bone fragments, or spurs that complicate tendon dislocation and rupture. Although the authors prefer MR imaging, they caution that all of the modalities are not always specific and that differentiation between closely related processes such as tendinitis and early tendon rupture is difficult.

Ankle Joint↗
PubMed1991

Medial dislocation of the biceps brachii tendon: appearance at MR imaging.

Abnormalities of the long tendon of the biceps brachii muscle commonly accompany other lesions about the shoulder, especially rotator cuff rupture, and are a frequent cause of a painful shoulder. The spectrum of abnormalities associated with medial displacement of the biceps tendon seen at magnetic resonance (MR) imaging was reviewed in six patients. MR imaging was performed on a 1.5-T system with use of a dedicated surface coil. The findings at MR imaging were correlated with those at surgery. Two types of medial displacement of the biceps tendon were identified. More frequently observed was a defect in the subscapularis apparatus that allowed intraarticular entrapment of the biceps tendon. Less commonly observed was incomplete dislocation, with the biceps tendon lying between a partially disrupted subscapularis tendon. MR imaging enabled accurate identification of medial dislocation of the biceps tendon and entrapment of the tendon within the glenohumeral joint. MR imaging also demonstrated the associated disruption of the subscapularis tendon that must be present to allow the biceps tendon access to the joint space.

Aged↗
PubMed2001

Full- versus partial-thickness Achilles tendon tears: sonographic accuracy and characterization in 26 cases with surgical correlation.

PURPOSE: To determine the accuracy of the use of sonography for differentiation of full- from partial-thickness tears or tendinosis of the Achilles tendon by using surgical findings as the standard of reference and to identify sonographic characteristics of full-thickness tears that can be used to differentiate the two types of tears. MATERIALS AND METHODS: In part A of this study, sonographic findings (based on reports) in 26 consecutive cases of tears of the Achilles tendon were compared with surgical findings. In part B, the sonograms were blindly and retrospectively evaluated with respect to six sonographic characteristics possibly related to pathologic findings in the tendon, and the characteristics were correlated with surgical findings. RESULTS: In part A, statistical data regarding the use of sonographic findings to distinguish full- from partial-thickness tears were as follows: sensitivity, 100%; specificity, 83%; accuracy, 92%; positive predictive value, 88%; and negative predictive value, 100%. In part B, tendon thickness (P <.001), posterior acoustic shadowing (P =.007), and tendon retraction (P <.001) were correlated with full-thickness tears. Visualization of fat herniation (P =.051) and of the plantaris tendon (P =.098) demonstrated marginal correlation with full-thickness tears. Echogenicity at the site of the pathologic finding in the tendon showed no significant correlation. CONCLUSION: Sonography can be used to differentiate full- from partial-thickness tears or tendinosis of the Achilles tendon with 92% accuracy. Undetectable tendon at the site of injury, tendon retraction, and posterior acoustic shadowing demonstrate statistically significant correlation with full-thickness tears.

Achilles Tendon↗
PubMedDate not supplied

A partially biodegradable material device for repair and reconstruction of injured tendons. Experimental studies.

We assessed the applicability of a partially biodegradable synthetic material composed of polyglycolic acid (PGA) and dacron to repair or replace severely injured tendons. Adult rabbits underwent complete laceration and repair of one Achilles tendon. Group 1 (N = 8) had end to end tenorrhaphy with size 0 braided polyester suture, and Group 2 (N = 16) tendons were similarly repaired with the bicomposite designed PGA-dacron device. Group 3 (N = 16) received laceration and removal of 1 cm of tissue, and the defect was bridged with the same PGA-dacron material. No postoperative immobilization was applied. Evaluation, consisting of biomechanical testing or histologic inspection, was done at 4 and 8 weeks after tenorrhaphy. All tendons healed, and at 8 weeks the mean maximum load at failure of the repaired tendons was 32.2 +/- 3.4 kgf, 40.3 +/- 2.4 kgf, and 31.8 +/- 3.2kgf for Groups 1, 2, and 3, respectively. Values between groups were not significantly different, but all were significantly less (P less than or equal to 0.05) than the strength of the unoperated control tendons (55.8 +/- 7.2 kgf). The most noteworthy finding was the lengthening of the repaired tendons, due to scar elongation at the tenorrhaphy site, that occurred during healing as determined by a landmark placed a fixed distance proximal to the repair site. Group 1 tendons lengthened 22 mm, while Group 2 and 3 tendons increased by 12.5 mm. Histologically, fibrous tissue ingrowth into the residual dacron scaffold occurred, but it was inconsistent and inadequate in quality and quantity to be satisfactory as neotendon. The fibrous tissue did not mature or align in response to load. We concluded that the PGA-dacron material had adequate strength and physical properties to use both for primary tenorrhaphy and to bridge the tendon defect. However, in our experience this material lacks any significant advantage over other materials available or known to be under evaluation to support neotendon formation when an actual soft tissue defect exists.

Achilles Tendon↗
PubMed1995

Exercise loading of tendons and the development of overuse injuries. A review of current literature.

This review examines recent studies on the effects of exercise on tendons in animal models. Although tendon adaptation to exercise has been described using histology, morphometry, ultrasonography and molecular biology, precise measurements of excess tendon loading during exercise protocols have not been reported. Only a few studies have attempted to evaluate the mechanical strength of exercised tendons. The long term effect of exercise on tendons appears to be positive, but researchers have suggested that periods of mechanical weakness occur in tendons during adaptation to loading conditions. Studies documenting changes associated with the terminal state of pathological tendons are also summarised. Unfortunately, there are no descriptions of tendon tissue in the early stages of overuse injury. Since blood flow is commonly implicated in the emergence of tendinitis, the final section covers recent work on blood flow and tendon physiology. Related research identifying cellular mediators (hyperthermia, hypoxia, and oxidative stress) involved in the development of tendinitis is also presented. Suggestions for further research into exercise loading and the development of tendon overuse injuries are made.

Adaptation, Physiological↗
PubMed1988

Sonography of the Achilles tendon and adjacent bursae.

Abnormalities of the Achilles tendon and adjacent bursae are common problems that may be difficult to diagnose clinically. Twenty patients with symptoms involving the Achilles tendon and 10 control subjects were evaluated with real-time sonography in order to explore the role of sonography in defining abnormalities of the tendon and adjacent bursae and in differentiating between conditions requiring surgery and those needing conservative therapy. Normal anatomic structures seen consistently included the Achilles tendon, the musculotendinous junction, the retrocalcaneal bursa, and the calcaneal tendon insertion site. The normal range of tendon thickness was 4-9 mm (mean, 6.2 mm). All patients had repeat sonograms after either clinical resolution (14 cases) or surgical intervention (six cases). Twelve of the symptomatic patients had abnormal findings. Partial ruptures of the Achilles tendon were reliably differentiated from other lesions. No evidence of tendon thickening was found in tendinitis. Tendon thickening was found only in cases of previous tendon rupture. The superficial tendo Achillis bursa was imaged only when inflamed. Sonography was found to differentiate reliably between conditions that require surgical intervention and those that will respond to conservative therapy.

Achilles Tendon↗
PubMed2004

MRI diagnosis of tears of the hip abductor tendons (gluteus medius and gluteus minimus).

OBJECTIVE: The purpose of our study was to determine the accuracy of MRI for diagnosing tears of the hip abductor tendons (gluteus medius and gluteus minimus) and to evaluate various signs of tendon disruption. MATERIALS AND METHODS: We retrospectively evaluated MRIs of 74 hips (in 45 patients) that were obtained using 35- to 42-cm fields of view and interpreted using primary and secondary signs of tendon disruption. Fifteen hips had surgically proven abductor tendon tears, and 59 hips were either asymptomatic or had surgically confirmed intact tendons. MRI findings were scored by two radiologists through consensus and then again independently by a third radiologist to determine interobserver agreement. RESULTS: The accuracy of MRI for the diagnosis of tears of the abductor tendons was 91%. Statistically significant associations were found between tears of the abductor tendons and areas of high signal intensity superior to the greater trochanter on T2-weighted images (p < 0.0001), tendon elongation in the gluteus medius (p = 0.0028), tendon discontinuity (p = 0.016), and areas of high signal intensity lateral to the greater trochanter on T2-weighted images (p = 0.0213). Interobserver agreement was good to fair. CONCLUSION: MRI showed good accuracy for the diagnosis of tears of the gluteus medius and gluteus minimus tendons. The identification of an area of T2 hyperintensity superior to the greater trochanter had the highest sensitivity and specificity for tears at 73% and 95%, respectively.

Aged↗
PubMed1989

Tendon healing in vivo. An experimental model.

Flexor tendon segments were incubated in a diffusion chamber in the subcutis of rabbits. Tendons incubated up to 6 weeks in the diffusion chamber showed proliferating and migrating cells from the epitenon cell layer as well as viable endotenon cells. Explants frozen in liquid nitrogen prior to incubation showed no signs of extrinsic cell contamination and remained non-viable indicating that no cell penetration occurred through the Millipore filter and that cell division seen in non-frozen and incubated tendons was an expression of intrinsic cellular proliferative capacity of the tendon. In tendon segments incubated in chambers for three weeks, collagen synthesis was reduced by 50% and the rate of cell proliferation measured as 3H-thymidine incorporation, was 15 times that of native tendons. Frozen and incubated tendons showed only traces of remaining matrix synthesis or cell proliferation. With this experimental model we have histologically and biochemically shown that tendons may survive and heal while the nutrition exclusively could be based on diffusion and the tendons have an intrinsic capacity of healing. The described model enables further studies on tendon healing and its regulation.

Animals↗
PubMed2004

[Capability for anti-stretch of 4 allogeneic tendon grafts].

OBJECTIVE: To research the biomechanic property of 4 tendon grafts. METHODS: The biomechanic properties of profound hypothermua froze tendon allogeneic grafts, profound hypothermua froze and dried allogeneic tendon grafts, autologous tendon grafts and allogeneic tendon grafts without intervention were tested. RESULTS: The biomechanic property of allogeneic tendon grafts with profound hypothermua freezing and profound hypothermua freezing and dying was better than that of allogeneic tendon grafts without intervention (P < 0.05). No significant difference was seen between the former 2 grafts and dried autologous tendon grafts (P > 0.05). CONCLUSION: Allogeneic tendon grafts with profound hypothermua freezing and profound hypothermua freezing and drying, have the same biomechanic property as dried autologous tendon grafts and can be used in clinical practice.

Animals↗
PubMed1987

Flexor tendon injuries. Part 5. Flexor tenolysis, rehabilitation and results.

In this five-part series, we have attempted to review our current understanding of flexor tendon anatomy, physiology, biomechanics, healing and adhesion formation around a repaired tendon. The methods of acute flexor tendon repair, conventional free tendon grafting, staged flexor tendon reconstruction and pulley restoration have been discussed as well as flexor tenolysis, rehabilitation and results. From these articles it may be seen that flexor tendon surgery is a complex and difficult art which requires a thorough appreciation of the normal flexor tendon system, the exact status of that system following injury and a strong understanding of the techniques which may be best utilized to restore flexor tendon function. The procedures described require both technical skill and experience and postoperative therapy programs must be carefully instituted based on the unique status of each patient. With the important advances occurring in many areas of flexor tendon surgery, it is realistic to believe that in the near future the techniques described in these articles may be substantially altered and modified. Results will continue to improve until the patient and surgeon can realistically expect to return most digits to nearly full function after flexor tendon interruption.

Anesthesia↗
PubMed1985

Flexor tendon repair.

In 1979 Verdan wrote, "whatever the situation may be, adhesions are until now certainly not a technically avoidable accident, but rather a consequence of the physiological healing process. As long as we have no technical solution to the problem of accurately maintaining the two cut ends in an intact synovial sheath without interfering with the blood supply, adhesions will remain a biologic inevitability." Although his admonition remains applicable, advances are occurring in our understanding of tendon healing and nourishment, the pulley system, techniques of repair, and the modification of adhesions. Armed with this information, each surgeon dealing with interruptions of flexor tendons must develop a rational, systematic approach to the management of these difficult injuries. The principles of atraumatic technique, as set down many years ago by Bunnell, remain inviolate. Repair procedures should be carried out by surgeons who are thoroughly knowledgeable and well trained in the area of flexor tendon surgery. Primary or delayed primary tendon repair of both the profundus and superficialis tendons should be carried out in almost all patients in all zones of flexor tendon interruption. The use of nonabsorbable sutures with a modified Kessler or Tajima "core suture" has proved to be effective, and, whenever possible, repair of the flexor tendon sheath seems to be appropriate. A well supervised program of early motion utilizing either active or passive techniques is also beneficial in suitable individuals. The restoration of function to a digit following flexor tendon interruption may be a long and tedious undertaking, requiring strong rapport between surgeon, therapist, and patient. When initiating the care of a patient with such an injury, the surgeon should spend considerable time explaining the problems related to the particular injury, the likelihood of achieving success, and the number of procedures that may be required. A high degree of patient motivation must be established to insure the proper participation in the demanding postoperative regimen associated with these procedures. With the important advances occurring in many areas of flexor tendon surgery, it is realistic to believe that in the future the techniques described in this article will be substantially altered and modified. Results should continue to improve until the patient and surgeon can expect all digits to return to nearly full function after flexor tendon interruption.

Fingers↗
PubMed1983

Comparison of unrepaired, primarily repaired, and polyglactin mesh-reinforced Achilles tendon lacerations in rabbits.

The tensile and histologic characteristics of sharply transected Achilles tendons treated by cast immobilization, surgical repair, and surgical repair reinforced with polyglactin mesh were evaluated in 31 rabbits. All modes of tendon treatment resulted in tensile failure at significantly lower loads than in the contralateral control tendons. However, when the cross-sectional area and rupture stress of each pair of tendons were considered, the surgically repaired tendons more closely approximated the load tolerance of the control side than did the unrepaired, casted tendons. The mesh-reinforced tendons exhibited no mechanical superiority to the suture-repaired tendons. No microscopic difference in the quality of collagen deposition for the three types of repairs was apparent. Subcutaneous mesh did not evoke a significant cellular or fibrous reaction and was totally absorbed by the time of necropsy. A significant difference was found between the tolerated stress of the unrepaired and repaired tendons, but no functional benefit of repairing acutely transected Achilles tendons with synthetic mesh was observed.

Achilles Tendon↗
PubMed1993

Effects of constant mechanical tension on the healing of rabbit flexor tendons.

The biomechanical effects of constant mechanical load on tendon repair in vitro were determined for rabbit flexor tendons. Tendons were removed from Zone II, transected, reapproximated with four simple sutures, and cultured in standard medium. Tendons from the right forelimbs were loaded with 3.1-g weights; tendons from the contralateral forelimbs served as unloaded tendons. Tenorrhaphies were disrupted at zero, one, three, and six weeks postsuturing by fixed-speed tensiometry. True maximum stress (strength), normalized energy absorbed, and tangent modulus steadily increased over time, becoming significantly greater than unincubated controls in the loaded and unloaded groups at six weeks. True strain at maximum stress increased with duration for unloaded tendons; after six weeks it was significantly greater than unincubated control tendons. This study demonstrates a method for quantifying the biomechanics of tendon after intrinsic tendon segment healing and presents the first biomechanical evaluation of constant tension applied across the laceration site during an in vitro healing phase.

Animals↗
PubMed1996

Tendon repair by laser welding: a histologic and biomechanical comparison and suture repair with CO2 and argon lasers.

BACKGROUND AND OBJECTIVE: The purpose of this study was to determine whether welding of tendinous tissue is possible with the application of thermal lasers. STUDY DESIGN MATERIALS AND METHODS: After sharp transection of a unilateral achilles tendon, 40 male outbred Spraque Dawley rats were divided equally between four treatment groups. Ten animals underwent repair using the modified Kessler suture technique. The remaining animals underwent application of laser after the tendon edges were reapproximated and held in place with a vascular clamp. CO2 and Nd:YAG lasers were applied using 25% human albumin as a solder. Fluorescein dye was added to albumin and used as solder for the Argon laser. Biomechanical and histologic testing were performed immediately and 14 days postoperatively. RESULTS: Argon and CO2 lasers successfully fused the tendon ends together. However, immediately postoperative, the resultant tissue weld was tenuous and conventional tensile strength testing was not possible. At 14 days postoperatively, all modes of tendon repair resulted in tensile failure at consistently lower levels of tension than those required for the normal uninjured tendons. The ultimate tensile strength for the suture-repaired, CO2 laser welded, and Argon laser welded tendons were 74%, 59%, and 64% of the strength of the control tendons respectively. No statistically significant difference was found in the tensile strength among the three repair groups. Histologic evaluation at 14 days revealed the greatest degree of inflammatory response in those tendons repaired with the Argon laser. Those tendons repaired with suture demonstrated the least amount of inflammatory change. CONCLUSION: Our study demonstrates that welding of a tendon is possible with the application of laser energy. However, we were unable to produce a weld sufficient to withstand significant tensile loads in the immediate postoperative period.

Achilles Tendon↗
PubMed1998

Laser photostimulation of collagen production in healing rabbit Achilles tendons.

BACKGROUND AND OBJECTIVE: Low energy laser photostimulation at certain wavelengths can enhance tissue repair by releasing growth factors from fibroblasts and stimulate the healing process. This study was designed to evaluate the influence of laser photostimulation on collagen production in experimentally tenotomized and repaired rabbit Achilles tendons. STUDY DESIGN/MATERIALS AND METHODS: A total of 24 male New Zealand rabbits, ages 10-12 weeks, were used. Following tenotomy and repair, the surgical hind limbs of the rabbits were immobilized in customized polyurethane casts. The experimental animals were treated with a 632.8 nm He:Ne laser daily at 1.0 J cm(-2) for 14 days. Control animals were sham treated with the laser head. On the fifth day after repair, the casts were removed to allow the animals to bear weight on the lower extremity. The animals were euthanized on the 15th postoperative day, then, the Achilles tendons were excised, processed and analyzed. RESULTS: Biochemical analyses of the tendons revealed a 26% increase in collagen concentration with laser photostimulation indicating a more rapid healing process in treated tendons compared to controls. Sequential extractions of collagen from regenerating tissues revealed that the laser photostimulated tendons had 32% and 33% greater concentrations of neutral salt soluble collagen and insoluble collagen, respectively, than control tendons suggesting an accelerated production of collagen with laser photostimulation. A significant decrease (9%) in pepsin soluble collagen was observed in laser-treated tendons compared to controls. There were no statistically significant differences recorded in the concentrations of hydroxypyridinium crosslinks and acid soluble collagen between treated and control tendons. CONCLUSION: This study of laser photostimulation on tendon healing in rabbits suggests that such therapy facilitates collagen production in a manner that enhances tendon healing.

Achilles Tendon↗
PubMed1985

A morphometric analysis of the muscle-tendon junction.

Transmission of the contractile force produced by skeletal muscle fibers from myofilaments to tendon fibers occurs at the muscle-tendon junction. This interface between muscle and tendon is characterized by an amplification of the membrane area across which force is transmitted, with the result that stress at the muscle-tendon interface is less than it would be if the muscle fiber ended without surface folding. The amount of stress reduction is proportional to the degree of surface amplification. Because an understanding of the mechanical properties of the muscle-tendon junction requires a quantitative appreciation of the amplification of interfacial area, and hence the reduction of stress, produced by membrane elaboration at the muscle-tendon junction, we have developed a reliable morphometric approach for quantifying this surface amplification. The approach reported here makes use of point-counting techniques applied to thin sections of murine muscle-tendon junctions, together with a statistical analysis of the data. The results indicate that the load on the cell membrane at the muscle-tendon junction is reduced approximately 1 order of magnitude by membrane amplification, compared to the load calculated to occur if the muscle fiber ended as a right cylinder. In addition, significant differences in the degree of membrane amplification have been detected among the four muscle-tendon junctions analyzed in this study. These results and methods should prove useful in future analyses of normal and abnormal muscle-tendon junctions.

Analysis of Variance↗
PubMed1995

Extensor tendons of the fingers: arrangement and variations--II.

One hundred eighty-one dissected hands were examined to study the pattern of extensor tendons on the dorsum of the hand. Extensor digitorum often had multiple tendons for the middle and ring fingers. Its contribution to the little finger was usually by a bifurcating tendon common with that of the ring finger. The index finger always received a single tendon. Intertendinous connections between the various tendons of the extensor digitorum were variable but were most frequent between ring and middle fingers. Extensor indicis had one tendon in most of the specimens and it was always on the ulnar side of the extensor digitorum tendon. This remained true even when there were multiple tendons. Extensor digiti minimi had two tendons in most cases. It was always linked to extensor digitorum either by receiving one or part of its tendon or by an intertendinous connection. Two accessory muscles were seen, one was extensor indicis brevis replacing the proper muscle. The other, the extensor medii brevis, was distributed to the middle finger.

Cadaver↗