Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “TENDONS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources
PubMedDate not supplied

Braided hamstring tendons for reconstruction of the anterior cruciate ligament. A biomechanical analysis.

BACKGROUND: In an effort to improve the strength and stiffness of anterior cruciate ligament grafts, several authors have advocated alterations of graft structure and orientation, including braiding the tendons in hamstring tendon grafts. HYPOTHESIS: Braiding hamstring tendons does not increase graft strength and stiffness. STUDY DESIGN: Controlled laboratory study. METHODS: Sixteen hamstring tendon and 21 bone-patellar tendon-bone grafts were harvested from 12 cadavers and divided into three groups: 1) braided four-strand hamstring tendon, 2) unbraided four-strand hamstring tendon, and 3) bone-patellar tendon-bone. All grafts were placed under a 50-N preload on a servohydraulic testing device and were tensioned to failure. RESULTS: The strength and stiffness of the tested specimens averaged 427 +/- 36 N and 76 +/- 10 N/mm, respectively, for braided specimens, 532 +/- 44 N and 139 +/- 18 N/mm for unbraided specimens, and 574 +/- 46 N and 158 +/- 15 N/mm for patellar tendon specimens. There was a 20% decrement in hamstring tendon graft tensile strength and a 45% decrease in stiffness after braiding because of the suboptimal multidirectional orientation of individual tendons within the braided grafts. CONCLUSIONS: In vitro braided hamstring tendon grafts demonstrated mechanically inferior strength and stiffness characteristics compared with unbraided hamstring tendon grafts and patellar tendon grafts. CLINICAL RELEVANCE: Braiding of hamstring tendon grafts provides no mechanical advantage in anterior cruciate ligament reconstruction.

Aged↗
PubMed2004

Immediate Achilles tendon response after strength training evaluated by MRI.

PURPOSE: To evaluate the tendon response after acute strength training in chronic Achilles tendinosis using magnetic resonance imaging (MRI). METHODS: Twenty-two patients (44 Achilles tendons, 15 males, 8 patients with bilateral symptoms) with a median age of 45 yr (range 28-57 yr) were included in the study. In all patients, both Achilles tendons were examined with MRI before and immediately after a standardized training program. The most painful side underwent 6 sets and 15 repetitions of heavy-loaded eccentric training. The contralateral tendons underwent only concentric loading during the training program. The tendon volume and the intratendinous signal were evaluated and calculated by MRI using a seed-growing technique. RESULTS: The immediate response of eccentric loading on the symptomatic tendons resulted in a 12% increase of the tendon volume, evident on T2-WI, from 7.8 +/- 2.0 to 8.8 +/- 2.7 cm3 (P < 0.001), and a 31% increase of the intratendinous signal evident on PD-WI, from 221 +/- 74 to 278 +/- 78 signal units (SU) (P < 0.001). The corresponding sequences on the contralateral concentrically loaded tendons showed an increase of 17% of tendon volume, from 6.1 +/- 1.5 to 7.0 +/- 1.6 cm3 (P < 0.001), and an increase of 27% of the intratendinous signal, from 170 +/- 55 to 211 +/-57 SU (P < 0.001). There was no significant difference of the mean of the increased tendon volume and the intratendinous signal between the eccentrically heavily loaded symptomatic tendons and the concentrically loaded contralateral tendons. CONCLUSIONS: Both eccentric and concentric loading of the Achilles tendon resulted in increased total tendon volume and intratendinous signal. This increase may be explained by a higher water content and/or hyperemia in the Achilles tendon during and/or immediately after strength training of the gastrocnemius-soleus complex.

Achilles Tendon↗
PubMed2004

Effect of gap size on gliding resistance after flexor tendon repair.

BACKGROUND: Gap formation is a common complication after flexor tendon repair and is associated with adhesion formation, tendon rupture, and decreased strength. The purpose of this study was to investigate the effect of gap formation on tendon gliding resistance after flexor tendon repair in a human cadaver model. METHODS: Twelve index, middle, and ring fingers from four adult human cadaveric hands were used. Gliding resistance versus excursion between the flexor digitorum profundus tendon and the A2 pulley was first measured in intact tendons. After full laceration, each tendon was repaired with the Pennington suture technique and the gliding resistance was measured again. Then, the repaired tendon (a 0-mm gap) was stretched to form a 1-mm gap, and gliding resistance was remeasured. A magnified video image was used to monitor gap size. This process was repeated to evaluate gap sizes of 2, 3, and 4 mm at the repair site. Peak gliding resistance was determined, and the peak gliding resistance was compared among the groups. RESULTS: No significant difference in peak gliding resistance was detected between repaired tendons without a gap and tendons with a 1-mm gap. Repaired tendons with a 2-mm gap could pass through the A2 pulley; however, peak gliding resistance was significantly higher than that for tendons with a 0 or a 1-mm gap (p < 0.05). When the gap reached > or =3 mm, all tendons caught at the A2 pulley edge, causing a dramatically increased peak gliding resistance. CONCLUSIONS: The presence of a 2-mm gap after flexor tendon repair significantly increased tendon peak gliding resistance (p < 0.05), while a gap of > or =3 mm further increased peak gliding resistance because of catching at the pulley edge.

Aged↗
PubMed2000

Tendon tissue sampling.

Mechanical load is regarded as the most important etiologic factor in cumulative trauma disorders affecting human tendons. At present there is limited knowledge concerning adaptation and the influence of training on human tendon tissue and the time process of developing a chronic tendon disorder. Tendon tissue samples and data concerning tendon pathology and repair have been derived from biopsies removed during surgery for rupture or pain conditions and from autopsy material. The ultrasound-guided percutaneous core biopsy technique provides the possibility to obtain tendon tissue from human Achilles and patellar tendon with limited discomfort for the individual. The specimens can be used for diagnostic purposes or for research and have the potential to highlight novel knowledge in, for example, the early stages of painful human tendon disorders. The fact that the procedure is invasive is a limitation. Autopsy material has limitations regarding poor information on case history, post mortem alterations and legal regulations on the use of tissue for medical purposes. The inflammatory process quickly affects ruptured tendons. The subcutaneous tendons that sustain a rupture are commonly characterized by degenerative alterations. Many tendon ruptures are treated with surgery, facilitating easy access to biopsy material. In summary, tendon tissue sampling in humans has obvious limitations. The recently described use of the core biopsy technique in human tendon research and diagnosis gives potential for new knowledge concerning human tendon adaptation, repair and disease.

Achilles Tendon↗
PubMed1997

In vivo gene transfer and overexpression of focal adhesion kinase (pp125 FAK) mediated by recombinant adenovirus-induced tendon adhesion formation and epitenon cell change.

Adhesion formation is a frequent complication of tendon injury repair: however, little is known about its mechanisms. The intracellular focal adhesion kinase (FAK)-related signaling pathway may be one of the mechanisms involved in the induction of tendon adhesions. The replication deficient adenovirus containing the FAK gene (pp125 FAK) was constructed and named Adv-Fak. By in vitro transductions with the recombinant virus, overexpression of the FAK protein was documented in transduced cultured primary tendon cells. By in vivo direct injection of Adv-FAK into the space between the tendon and tendon sheath of White Leghorn chickens, FAK gene transfer with overexpression of the FAK protein was detected by immunohistological staining. The morphology of these stained cells changed from the normal flat shape to cuboid. The group with overexpressed adenovirus-mediated FAK had significant adhesion formation, as seen by increased work of flexion (118.197 +/- 29.616), compared with the group with overexpressed adenovirus-mediated beta-galactosidase (67.507 +/- 36.066) (p < 0.0393) and the group with adenovirus-mediated FAK antisense gene transfer (60.357 +/- 48.562) (p < 0.0211). Histological examination of the samples from tendons with Adv-FAK showed fibers between the tendon and tendon sheath; there were no fibers in the cavities of samples of injured tendons infected with Adv-beta gal. Moreover, at the application site of the former tendons, a thick fiber layer without epitenon cells was built up on the outer surface, whereas a thin fiber layer with clear epitenon cells was observed in the tendons to which Adv-beta gal was applied. Our results show that overexpression of FAK can induce tendon adhesion formation in vivo. This indicates that FAK and the FAK-related signaling pathway may be involved in the process of tendon adhesion formation. Understanding the details of this process may help to prevent tendon adhesion and improve healing.

Adenoviridae↗
PubMed2004

Motion-based tendon diagnosis using sequence processing of ultrasound images.

Degenerative or pre-degenerative processes in the tendon, which could lead to a spontaneous rupture, are well known problems, especially among athletes. Existing non-invasive diagnostic methods are mainly based on subjective analysis of static images of the tendon, but in many cases the degeneration cannot be diagnosed in time. Combining a set of existing image processing techniques, a tool for tracking the in vivo motion of a tendon imaged with dynamic ultrasound was implemented. A group of subjects that had undergone a degenerative rupture of their Achilles tendon, one subject with a traumatic rupture, and a group of control subjects were all tested. Using the motion information that was obtained from both tendons of all subjects, we developed an automatic test that examines the symmetrical properties of the tendon's motion, and defined a negative asymmetry property that could be quantified as a score. This score was found to be significantly more enhanced in the post-operative tendons (18.0 +/- 9.0) than in the contra-lateral healthy tendons of the same subjects (3.9 +/- 4.6). In the single traumatic rupture subject, this effect was not found (0.0). This leads us to believe that the negative asymmetry of tendon motion may be associated with degenerative or pre-degenerative processes in the tendon. Also, the mean degree of negative asymmetry in the healthy tendons of post-operative subjects (3.9 +/- 4.6) was found to be higher than that of healthy tendons of the control group (1.5 +/- 1.8). This finding may be associated with the fact that tendons that are contra-lateral to spontaneously ruptured tendons have a higher risk of developing degenerative processes. The method presented here is objective, low-cost, non-invasive and possibly more sensitive than existing non-invasive techniques.

Achilles Tendon↗
PubMed2002

Biomimetic approaches to tendon repair.

The linear organization of collagen fibers in tendons results in optimal stiffness and strength at low strains under tensile load. However, this organization makes repairing ruptured or lacerated tendons extremely difficult. Current suturing techniques to join split ends of tendons, while providing sufficient mechanical strength to prevent gapping, are inadequate to carry normal loads. Immobilization protocols necessary to restore tendon congruity result in scar formation at the repair site and peripheral adhesions that limit excursion. These problems are reviewed to emphasize the need for novel approaches to tendon repair, one of which is the development of biomimetic tendons. The objective of the empirical work described here was to produce biologically-based, biocompatible tendon replacements with appropriate mechanical properties to enable immediate mobilization following surgical repair. Nor-dihydroguaiaretic acid (NDGA), a di-catechol from creosote bush, caused a dose dependent increase in the material properties of reconstituted collagen fibers, achieving a 100-fold increase in strength and stiffness over untreated fibers. The maximum tensile strength of the optimized NDGA treated fibers averaged 90 MPa; the elastic modulus of these fibers averaged 580 MPa. These properties were independent of strain rates ranging from 0.60 to 600 mm/min. Fatigue tests established that neither strength nor stiffness were affected after 80 k cycles at 5% strain. Treated fibers were not cytotoxic to tendon fibroblasts. Fibroblasts attached and proliferated on NDGA treated collagen normally. NDGA-fibers did not elicit a foreign body response nor did they stimulate an immune reaction during six weeks in vivo. The fibers survived 6 weeks with little evidence of fragmentation or degradation. The polymerization scheme described here produces a fiber-reinforced NDGA-polymer with mechanical properties approaching an elastic solid. The strength, stiffness and fatigue properties of the NDGA-treated fibers are comparable to those of tendon. These fibers are biocompatible with tendon fibroblasts and elicit little rejection or antigenic response in vivo. These results indicate that NDGA polymerization may provide a viable approach for producing collagenous materials that can be used to bridge gaps in ruptured or lacerated tendons. The tendon-like properties of the NDGA-fiber would allow early mobilization after surgical repair. We predict that timely loading of parted tendons joined by this novel biomaterial will enhance mechanically driven production of neo-tendon by the colonizing fibroblasts and result in superior repair and rapid return to normal properties.

Animals↗
PubMed1995

[Functional adaptation processes of gliding tendons].

Structure and blood supply of the inserting tendons of supraspinatus and biceps brachii as well as the biceps brachii long head tendon are analyzed in respect of tendon rupture. Due to their course the three tendons investigated are gliding tendons. The part of the tendon adjacent to the pulley consists of fibrocartilage, the part looking away from the pulley having the structure of a traction tendon. The occurrence of fibrocartilage inside the investigated tendons is physiological and not a pathological finding. Development of fibrocartilage is a functional adaptation to pressure and shearing forces acting on the tendon at the pulley. In the investigated samples injection techniques and immunohistochemical methods show an avascular area in the part of the tendon that is adjacent to the pulley. The size of this area is identical with the fibrocartilage. The avascular zone in gliding tendons is due to structure, fibrocartilage is usually avascular. Localisation of rupture and fibrocartilage is nearly identical in the investigated tendons. Unphysiologically increased tensile stress which is inadequate for gliding tendons and occurs in certain kinds of sport may be responsible for the development of ruptures of the tendons of supraspinatus and biceps brachii.

Adaptation, Physiological↗
PubMed1996

MR imaging of posterior tibial tendon dysfunction.

OBJECTIVE: The purpose of this study was to describe the MR findings of posterior tibial tendon dysfunction. MATERIALS AND METHODS: MR images and medical records were reviewed for 11 patients with surgically proven posterior tibial tendon abnormalities (i.e., tears or tenosynovitis) and for six patients with clinical evidence of posterior tibial tendon dysfunction. Our study group included 16 women and one man from 37 to 70 years old (mean, 53.5 years old). MR examinations used T1-weighted and T2-weighted spin-echo sequences in the oblique axial and sagittal planes. RESULTS: Abnormal MR findings were observed in all 17 patients. The spectrum of MR abnormalities included fluid in the tendon sheath of a normal tendon interpreted as isolated paratenonitis (tenosynovitis, n = 3); tendon thickening and surrounding fluid with normal tendon signal interpreted as tendinosis (degeneration, n = 1); tendon thickening with increased linear or heterogeneous intrasubstance signal interpreted as partial tear (n = 11); tendon discontinuity with fluid-filled tendon sheath interpreted as complete rupture (n = 2). In 11 patients, the posterior tibial tendon was explored at surgery. In these patients, MR imaging accurately showed two cases of isolated paratenonitis, one case of tendinosis, four partial tears, and two complete ruptures. In the remaining two patients, the presumed MR diagnosis did not correlate very closely with the surgical findings: one patient with isolated paratenonitis shown by MR imaging had tendinosis found at surgery; however, the surgery in this patient followed the MR examination by 10 months, a time during which degeneration might have occurred. The other patient had an MR diagnosis of partial tear, which was not found at surgery; however, tendon degeneration was severe and a small tear not reaching the tendon surface could have been missed at inspection. MR imaging characteristics of severe tendinosis and partial tear may overlap. CONCLUSION: MR imaging is effective for detecting abnormalities related to posterior tibial tendon dysfunction. Familiarity with the appearance of these changes facilitates accurate characterization.

Ankle↗
PubMed2003

Association of biceps tendon tears with rotator cuff abnormalities: degree of correlation with tears of the anterior and superior portions of the rotator cuff.

OBJECTIVE: This study was performed to examine the relationship and association of abnormalities seen in the long head of the biceps brachii tendon to abnormal findings in the rotator cuff. MATERIALS AND METHODS: One hundred eleven patients underwent MR imaging for shoulder pain followed by arthroscopic or open shoulder surgery from January 1997 to December 2000. Patients were identified by a retrospective search, and all consecutive patients having undergone both MR imaging and surgery were included in the patient cohort. Official MR imaging interpretations were compared with operative reports, and all findings were recorded. RESULTS: Twenty-three patients were identified with partial- or full-thickness tears of the long head of the biceps tendon. The sensitivity, specificity, and accuracy of unenhanced MR imaging of the shoulder for detecting these bicipital tears were 52%, 86%, and 79%, respectively. When a tear was present in the biceps tendon, the prevalence of supraspinatous, infraspinatus, and subscapularis tendon tears was 96.2%, 34.6%, and 47.1%, respectively. Patients with biceps tendon tears were significantly more likely to also have subscapularis tendon tears (p < 0.0001) and supraspinatous tendon tears (p < 0.008) than those patients who did not have biceps tendon tears. No significant relationship was found between the presence or absence of a biceps tendon tear and the presence or absence of a infraspinatus or teres minor tendon tear (p = 0.17). CONCLUSION: Tears of the long head of the biceps tendon have a statistically significant association with tears of the anterior and superior rotator cuff and are highly correlated with tears of the supraspinatous and subscapularis tendons. When tears of these tendons are detected, specific attention directed toward the long biceps tendon is warranted to characterize the status of this structure that provides additional stability to the shoulder joint.

Adolescent↗
PubMed1991

Effects of sodium hyaluronate on tendon healing and adhesion formation in horses.

Sodium hyaluronate reduces adhesions after tendon repair in rodents and dogs, and has been used in limited clinical trials in people. To evaluate its effect on tendon healing and adhesion formation in horses and to compare these effects with those of a compound of similar visco-elastic properties, a study was performed in horses, using a model of collagenase injection in the flexor tendons within the digital sheath. Eight clinically normal horses were randomly allotted to 2 groups. Adhesion formation between the deep digital flexor tendon and the tendon sheath at the pastern region was induced in the forelimbs of all horses. Using tenoscopic control, a 20-gauge needle was inserted into the deep digital flexor tendon of horses under general anesthesia and 0.2 ml of collagenase (2.5 mg/ml) was injected. The procedure was repeated proximally at 2 other sites, spaced 1.5 cm apart. A biopsy forceps was introduced, and a 5-mm tendon defect was created at each injection site. Group-A horses had 120 mg of sodium hyaluronate (NaHA) gel injected into the tendon sheath of one limb. Group-B horses had methylcellulose gel injected at the same sites. The contralateral limbs of horses in both groups served as surgical, but noninjected, controls. Horses were euthanatized after 8 weeks of stall rest. Ultrasonographic evaluation revealed improved tendon healing after NaHa injection, but no difference in peritendinous adhesion formation. Tendon sheath fluid volume and hyaluronic acid (HA) content were greater in NaHA-treated limbs. Gross pathologic examination revealed considerably fewer and smaller adhesions when limbs were treated with NaHA. However, significant difference in pull-out strengths was not evident between NaHA-treated and control limbs. Histologically, the deep digital flexor tendon from the NaHA-treated limbs had reduced inflammatory cell infiltration, improved tendon structure, and less intratendinous hemorrhage. Treatment with methylcullulose had no significant effect on tendon healing, adhesion size, quantity, or strength or on the volume and composition of the tendon sheath fluid. Sodium hyaluronate, administered intrathecally, appears to have a pharmaceutically beneficial action in this collagenase-induced tendinitis and adhesion model in horses.

Animals↗
PubMed1985

Management of acute flexor tendon injury in the hand.

In this report, we have attempted to review the current state of the art with regard to the treatment of partial flexor tendon injuries, the strength of the flexor tendons and its relationship to complete tendon lacerations, and the importance of passive joint motion to improve tendon excursion. At this time, it appears that most partial flexor tendon injuries are best treated by nonsurgical repair and an early active assisted or passive range-of-motion exercise program for a period of 3 to 4 weeks. Protecting the hand up to a total of 10 to 12 weeks seems reasonable based on studies of tendon strength. Surgical intervention is necessary to prevent complications of triggering, entrapment, or rupture, which generally occur with lacerations of greater than 60%. We would reserve the repair of partial flexor tendon injuries to lacerations where tendon rupture, triggering, or entrapment would be expected. After flexor tendon repair, knowledge of the strength of tendons and the need for passive mobilization are important. There is not sufficient strength within the flexor tendon repair site to allow for active mobilization sooner than 17 days. Probably only with a lateral trap stitch similar to that described by Becker or with extremely well supervised and trusted patients can active motion be started this early. There is insufficient intrinsic tendon strength to consider active motion (without assistance) earlier than 3 1/2 to 4 weeks. Passive range of motion using the Kleinert-Atasoy or Durand technique before this period is important in not only increasing tendon gliding (or excursion) but also being a stimulus to improve flexor tendon healing strength.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1999

In situ expression of collagen and proteoglycan genes during development of fibrocartilage in bovine deep flexor tendon.

A region of fibrocartilage develops in bovine deep flexor tendon where the tissue wraps around bone and is subjected to compressive and shear forces in addition to tension. There is no fibrocartilage at this location in fetal tendon or in adjacent adult tendon that is subjected to tensional load only. We investigated the development of fibrocartilage in tendon using in situ hybridization to localize cells that express collagen and proteoglycan genes typical of either tendon or cartilage. The signal for type I collagen and decorin was high in cells throughout fetal and newborn tendon, as is expected in a growing tissue composed predominantly of type I collagen. No signal for aggrecan was seen in either fetal or newborn tendon. No hybridization with any of the probes for collagen or proteoglycan was detected in cells in the tensional region of adult tendon, indicating that the cells in this tissue are normally quiescent. However, the cells in the fibrocartilage of adult tendon displayed a high level of expression for types I and II collagen, decorin, biglycan, and aggrecan. This suggests that the fibrocartilage in adult tendon is a dynamic tissue. Expression of type IIA collagen is considered a marker of prechondrocytes. Type IIA collagen gene expression was present throughout both the tensional and compressed regions of fetal and newborn tendon but was absent in cartilage and adult tendon. This suggests that cells located throughout fetal tendon may have the capacity to develop as chondrocytes. Fibrocartilage signal was detected for type I collagen in 75% of the cells and for type II collagen in 50% of the cells at one location in adult tendon, suggesting that some cells in this tissue could have expressed mRNA for both type I and type II collagen.

Animals↗
PubMed1983

The in-series and in-parallel components in rat hindlimb tendon organs.

The structure of the tendon organs was studied in the shank muscles of adult rats both under the light- and electron-microscope. The rat tendon organs measure on the average about 500 microns in length and 60 microns in diameter. Most tendon organs are surrounded by muscle fibres and their short individual tendons, and insert into the aponeuroses or intramuscular tendons. Each tendon organ consists of a neurotendinous core composed of collagen bundles that represent tendons of 5-10 muscle fibres; it is innervated by a Ib sensory fibre that branches and terminates among the loose collagen fascicles of the core. Sensory terminals are oriented both transversely and longitudinally. Their position and relation to collagen bundles indicate that, during tendon organ activation, the terminals are probably depolarized both by lateral compression and elongation. The core is enclosed in a capsule that consists of about 5 lamellar layers of capsular cells and closely resembles the perineurium. The majority of the tendon organs also comprise a purely tendinous compartment in the lumen or within the capsular wall. These tendinous components remain separated from the neurotendinous core and do not come into contact with axon terminals. The collagen fibrils of the tendinous compartments are densely packed and larger in diameter than those of the neurotendinous core. The sensory terminals of the tendon organ lie in series with those muscle fibres and collagen bundles that constitute the neurotendinous core, but they are in parallel with the purely tendinous tendon organ components and their respective muscle fibres. Thus, one tendon organ may comprise both in series and in parallel components, which is apparently reflected in its function. It is suggested that the purely tendinous tendon organ compartments account for the in-parallel effects upon the function of tendon organs described in some recent electrophysiological studies.

Animals↗
PubMed2004

Graft-bone motion and tensile properties of hamstring and patellar tendon anterior cruciate ligament femoral graft fixation under cyclic loading.

PURPOSE: To assess longitudinal graft-bone motion and tensile properties of the femur-anterior cruciate ligament (ACL) graft fixation-ACL graft complex based on the hypothesis that there is little difference in graft-bone motion between suspensory and aperture hamstring ACL femoral graft fixation techniques, and between hamstring and patellar tendon ACL femoral graft fixation techniques. TYPE OF STUDY: In vitro biomechanical study using human cadavers. METHODS: The distal femur-ACL graft fixation-ACL graft complex was cyclically loaded between 50 and 250 N at 1 Hz for 1,000 cycles with the direction of the load applied parallel to the axis of the femoral bone tunnel. Graft-bone motion was measured indirectly using retroreflective markers and a video motion-analysis system. Tensile testing to failure was performed at 1 mm/sec for fixation techniques completing 1,000 cycles without fixation failure. RESULTS: Among the hamstring fixation techniques, 4 of 13 Bio-Interference screws (Arthrex, Naples, FL), 2 of 12 LinX HT fasteners (DePuy Mitek, Norwood, MA), and 1 of 11 TransFix cross-pins (Arthrex) failed before completing 1,000 cycles. Five of 13 patellar tendon grafts fixed with metal interference screws, and 2 of 12 patellar tendon grafts fixed with a plastic button and No. 5 sutures failed before completing 1,000 cycles. Suture/button fixation of patellar tendon grafts resulted in significantly more graft-bone motion than hamstring tendon grafts fixed using the Bone Mulch Screw (Arthrotek, Warsaw, IN), or interference screw fixation of patellar tendon and hamstring grafts. Otherwise, there was no significant difference in graft-bone motion among the various hamstring fixation techniques or the various hamstring fixation techniques and interference screw fixation of patellar tendon grafts. Maximum graft-bone displacement after cyclic loading was significantly greater for hamstring grafts fixed with the EndoButton and EndoButton Tape (Smith & Nephew Endoscopy, Andover, MA) compared with the other hamstring fixation techniques and interference screw fixation of patellar tendon grafts. All fixation techniques except hamstring tendon grafts fixed with the Bio-Interference screw achieved at least 59% of maximum graft-bone displacement after 20 cycles. Hamstring tendon grafts fixed with the EndoButton CL were significantly stronger than all other hamstring and patellar tendon fixation methods. Patellar tendon grafts fixed with interference screws and hamstring tendon grafts fixed with interference screws and the Bone Mulch Screw and TransFix were significantly stiffer than hamstring tendon grafts fixed with the EndoButton CL. CONCLUSIONS: There is no significant difference in graft-bone motion between aperture and suspensory femoral fixation methods when the stiffness of the femur-ACL graft fixation-ACL graft complex is similar. CLINICAL RELEVANCE: The small differences in graft-bone motion reported in our study provide further evidence that graft-tunnel motion or the so-called bungee effect is unlikely to be the primary cause of radiographic bone tunnel enlargement following ACL reconstruction.

Anterior Cruciate Ligament↗
PubMed2003

Establishment of tendon-derived cell lines exhibiting pluripotent mesenchymal stem cell-like property.

Development of the musculoskeletal system requires coordinated formation of distinct types of tissues, including bone, cartilage, muscle, and tendon. Compared to muscle, cartilage, and bone, cellular and molecular bases of tendon development have not been well understood due to the lack of tendon cell lines. The purpose of this study was to establish and characterize tendon cell lines. Three clonal tendon cell lines (TT-E4, TT-G11, and TT-D6) were established using transgenic mice harboring a temperature-sensitive mutant of SV40 large T antigen. Proliferation of these cells was significantly enhanced by treatment with bFGF and TGF-beta but not BMP2. Tendon phenotype-related genes such as those encoding scleraxis, Six1, EphA4, COMP, and type I collagen were expressed in these tendon cell clones. In addition to tendon phenotype-related genes, expression of osteopontin and Cbfal was observed. These clonal cell lines formed hard fibrous connective tissue when implanted onto chorioallantoic membrane in ovo. Furthermore, these cells also formed tendon-like tissues when they were implanted into defects made in patella tendon in mice. As these tendon cell lines also produced fibrocartilaginous tissues in tendon defect implantation experiments, mesenchymal stem cell properties were examined. Interestingly, these cells expressed genes related to osteogenic, chondrogenic, and adipogenic lineages at low levels when examined by RT-PCR. TT-G11 and TT-E4 cells differentiated into either osteoblasts or adipocytes, respectively, when they were cultured in cognate differentiation medium. These observations indicated that the established tendon cell line possesses mesenchymal stem cell-like properties, suggesting the existence of mesenchymal stem cell in tendon tissue.

Adipocytes↗
PubMed1992

A new classification of superior oblique palsy based on congenital variations in the tendon.

BACKGROUND: Superior oblique palsy is the most frequent isolated cranial nerve palsy seen in strabismus practice. It is traditionally diagnosed according to etiology as acquired, congenital, or idiopathic, but surgical treatment is based on deviation not etiology. Observations at surgery led to speculation that the superior oblique tendon is different in congenital compared with acquired superior oblique palsy and that this difference should be considered in surgical treatment. METHODS: The authors reviewed the charts of 82 patients (89 eyes) undergoing surgery on the superior oblique tendon for superior oblique palsy. In each case, the palsy had been diagnosed preoperatively as acquired, congenital, or idiopathic, and, at surgery, characteristics of the tendon anatomy were described. RESULTS: Thirty-eight superior oblique tendons (36 patients), diagnosed as congenital superior oblique palsy, included 33 abnormal tendons and 5 normal tendons. Twenty-four tendons (21 patients), diagnosed as traumatic superior oblique palsy, included 22 normal and 2 abnormal tendons. Twenty-seven tendons (25 patients), diagnosed as idiopathic, included 19 normal and 8 abnormal tendons. Abnormal tendons were divided into 4 categories: (1) redundant, (2) misdirected, (3) inserted in posterior Tenon's capsule, and (4) absent. CONCLUSIONS: The authors conclude that congenital superior oblique palsy is usually associated with a structural abnormality of the superior oblique tendon (87%). Whereas acquired superior oblique palsy usually has a normal tendon (92%). Superior oblique underaction in acquired superior oblique palsy results from a neural deficit. Potential variance in anatomy of the superior oblique tendon should be considered when undertaking surgery for superior oblique palsy.

Adolescent↗
PubMed2000

Mechanical properties of collagen fascicles from in situ frozen and stress-shielded rabbit patellar tendons.

OBJECTIVE: To know the effects of stress shielding on the biomechanical properties of collagen fascicles obtained from in situ frozen patellar tendons (an autograft model). DESIGN: Collagen fascicles of approximately 300 microm in diameter were obtained from in situ frozen rabbit patellar tendons and also from in situ frozen and stress-shielded ones, and their mechanical properties and fibroblast density were determined. BACKGROUND: Stress shielding changes the mechanical properties of in situ frozen patellar tendons in which there exist no fibroblasts. The mechanisms of this phenomenon have not been studied well. METHOD: Patellar tendons of both in situ frozen group and in situ frozen and stress-shielded group were frozen in situ by liquid nitrogen to kill fibroblasts. Then, in the in situ frozen and stress-shielded group, no tension was applied to the tendons for 2, 3, and 6 weeks, while normal tension was applied to the tendons of the in situ frozen group. Tensile properties of the collagen fascicles obtained from these tendons were determined using a microtensile tester, and were compared to the collagen fascicles from non-frozen, stress-shielded patellar tendons. RESULTS: Tangent modulus and tensile strength of collagen fascicles from the in situ frozen and stress-shielded group progressively decreased with the time of stress shielding; however, these decreases were much smaller than those of the fascicles obtained from non-frozen, stress-shielded tendons. Although there were few fibroblasts in the patellar tendon of the in situ frozen and stress-shielded group at 2 weeks, the modulus and strength of the fascicles from the posterior portion were significantly lower than those in the in situ frozen group. In addition, the reduction of strength caused by stress shielding was much smaller in collagen fascicles than in bulk patellar tendons. CONCLUSION: The mechanical properties of collagen fascicles in in situ frozen tendons (an autograft model) are affected by stress shielding even under acellular condition. RelevanceThe in situ frozen, stress-shielded patellar tendon is a model of augmented autografts which are clinically used for the reconstruction of injured anterior cruciate ligaments. The sub-macroscopic studies of the tendon are useful to understand the mechanisms of the reduction of graft strength and its gradual recovery observed after reconstruction.

Animals↗