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PubMed2004

Gene transfer to the tendon-bone insertion site.

This study investigated whether gene transfer to the tendon-bone insertion site is possible during early tendon-transplant healing using viral vectors. In addition, we evaluated the optimal gene delivery technique for an in vivo adenoviral gene transfer to a tendon-bone insertion site in a bone tunnel. Twenty-six rabbits underwent a bilateral transfer of the flexor digitorum longus tendon into a bone canal in the calcaneus. The animals were divided into two groups. The first group (n=18) received a direct injection of an adenoviral vector carrying the luciferase marker gene into the tendon on the left side, while on the right side the adenoviral vector was first injected into the bone trough and the tendon was later inserted into the trough. The analysis of this experiment showed that over a 4-week period a higher luciferase activity was achieved using the bone trough immersion technique. In the second group (n=8) we therefore used the qualitative marker virus (Ad/-LacZ) with the bone trough immersion technique in order to show the site of gene expression. The histological analysis of this experiment demonstrated the presence of beta-galactosidase positive cells within the tendon-bone interface over a 4-week period. Therefore we showed in the first part of this study that the bone canal provides a more efficient target for direct adenoviral gene delivery than the tendon. In the second part of the study we demonstrated the feasibility of the bone trough immersion technique since sustained gene expression within the tendon-bone interface was obtained for up to 4 weeks. This study has shown the feasibility of gene delivery to the tendon-bone interface and provides the basis for the application adenoviral delivery of growth factor genes to the tendon-bone insertion site.

Adenoviridae↗
PubMed1991

Comparison on collagen gene expression in the developing chick embryo tendon and heart. Tissue and development time-dependent action of dexamethasone.

Glucocorticoids modulate various cellular functions such as proliferation, energy metabolism and the synthesis of proteins. In the present study, the response of collagen genes to dexamethasone in different stages of chick embryo development was studied in tendon and heart using Northern blot analysis and specific cDNA probes. The changes in collagen gene expression were compared to alterations in two reference mRNAs: actin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The levels of specific mRNAs measured per ribosomal RNA in tendon and heart varied markedly during normal development. In tendon the relative levels of alpha 1(I), alpha 2(I) and alpha 1(III) collagen mRNAs were highest between days 14-16 when also the synthesis of matrix proteins is most active. In heart the levels of these mRNAs peaked at day 12. In addition, qualitative differences were observed in the expression of actin genes between tendon and heart. Dexamethasone in high dose decreased collagen mRNA levels in tendons, while in heart a stimulatory effect was noted. Dexamethasone also decreased GAPDH mRNA levels in tendons. The alterations in gene expression after dexamethasone treatment in tendon and heart did not correlate with the level of specific glucocorticoid receptors, which varied markedly during the development of chick embryos. The cDNA for pro alpha 1(I) collagen hybridized to two transcripts corresponding to 6.2 and 5.1 kb in tendon and heart. During normal development of chick embryos the ratio of 6.2/5.1 kb mRNAs decreased markedly in heart, but no such change was observed in tendons. Dexamethasone, however, decreased the ratio of 6.2/5.1 kb transcripts in tendons. There was a significant correlation between the ratio 6.2/5.1 kb transcripts and total alpha 1(I) mRNA both in tendon and heart, suggesting that the 6.2 kb transcript may be associated with the rate of synthesis of type I collagen.

Actins↗
PubMed1992

Genetic expression for type I procollagen in the early stages of flexor tendon healing.

To determine the precise mechanism by which contact tendon healing occurs at the cellular level, the production of pro alpha (I) collagen messenger RNA (mRNA) produced by fibroblasts of healing intrasynovial flexor tendons was determined by an in situ hybridization technique. The repair site and the proximal and distal tendon stumps of repaired tendons treated with early controlled passive mobilization were fixed and buffered in formalin, 3, 7, 10, and 17 days after repair. A complimentary DNA (cDNA) probe corresponding to alpha (I) procollagen mRNA was labeled with [32P]d-CTP. After hybridization, autoradiography, and staining of the sections, the level of procollagen mRNA was assessed by microscopic examination. Rising levels of procollagen mRNA, indicating progressively increasing levels of synthetic collagen activity, were detected in the healing tendons through 10 days. A moderate decrease in procollagen mRNA was seen at 17 days. Genetic expression for procollagen mRNA was localized specifically to the epitenon cells on the tendon surface overlying the repair site and to cells in the gap between the tendon stumps. No detectable expression was noted in endotenon fibroblasts. The finding of high levels of expression for procollagen type I mRNA in the surface layer of healing tendons demonstrates that cells intrinsic to tendon epitenon contribute the greatest quantity of native tendon collagen to the repair site during these important early intervals after tendon suture.

Animals↗
PubMed1994

Cellular survival and proliferation in autogenous flexor tendon grafts.

In order to investigate fibroblast survival and proliferation in autogenous flexor tendon grafts, hindlimb intrasynovial and extrasynovial donor tendons were placed within the synovial sheaths of the medial and lateral forepaw digits of 21 dogs (42 tendons) and treated with controlled early passive motion. Intravital histologic evaluations with confocal microscopy and biochemical determinations of total DNA content and DNA synthesis were carried out at 10 days, 3 weeks, and 6 weeks. Intravital staining of the extrasynovial tendon grafts demonstrated variable degrees of cellular necrosis at the earliest intervals followed by cellular repopulation with fibroblasts and neovascularization from surface vessels. In contrast, intrasynovial tendon grafts were populated predominantly by viable cells at each interval, with occasional patches of cell necrosis and fibroblast ingrowth. Total DNA content and DNA synthesis values in the intrasynovial donor tendons were significantly lower than those seen in the extrasynovial tendon grafts at each interval. Extrasynovial tendons appear to act as scaffolds, undergoing extensive cellular death followed by a rapid repair response. Findings that intrasynovial tendon fibroblasts survive the tendon grafting process suggest that the nutritional supplies and metabolic requirements of intrasynovial and extrasynovial donor tendons differ largely.

Animals↗
PubMed1994

Variations in cellular proliferation and matrix synthesis in intrasynovial and extrasynovial tendons: an in vitro study in dogs.

Intrasynovial and extrasynovial flexor tendon grafts recently have been shown to have dissimilar patterns of cellular survival and host integration within the digital sheath. In an effort to determine if fundamental differences exist between these two types of tendons, we investigated the biochemical composition and cellular activity of intrasynovial and extrasynovial tendon segments of 12 adult mongrel dogs in short-term explant culture in MCDB 105 and in DMEM media. Proteoglycan, collagen and noncollagen protein synthesis and content and DNA synthesis were determined following culture in both media. Intrasynovial tendon segments cultured in MCDB 105 medium synthesized significantly less collagen, noncollagen protein, and DNA and had similar amounts of proteoglycans compared to extrasynovial tendons. Comparison of intrasynovial and extrasynovial tendon segment responses in DMEM medium showed that intrasynovial tendons synthesized more proteoglycan, protein, and DNA than they did in MCDB 105. Extrasynovial tendons had similar rates of matrix component and DNA synthesis in both media. Findings that the synthesis of matrix components and DNA between intrasynovial flexor and extrasynovial peroneal tendon segments differ significantly indicate that intrasynovial flexor tendons may be specially adapted to the nutritional milieu provided by an intrasynovial environment. These data are supported by the selective successful stimulation of fibrocartilaginous segments within intrasynovial flexor tendons in media favored for the culture of cartilaginous tissue.

Animals↗
PubMed2006

Biomechanical evaluation of the relation between number of suture anchors and strength of the bone-tendon interface in a goat rotator cuff model.

PURPOSE: The effect of contact area between tendon and bone on ultimate pullout strength of a repaired tendon is not known. The purpose of this study was to test whether the strength of a healed bone-tendon interface is related to the amount of tendon that is in contact with bone at the time of repair. METHODS: A total of 20 mature goats underwent bilateral open rotator cuff repair of the infraspinatus tendon. The tendon edge was repaired to bleeding cancellous bone in each case with the use of suture anchors. The tendon was repaired with 2 anchors (contact area A; n = 20) on 1 shoulder and 4 anchors (contact area B; n = 20) on the contralateral shoulder. Ten goats were euthanized at 4 weeks (group 1) and 10 goats at 8 weeks (group 2) postoperatively. Twelve specimens were evaluated with ultrasound in the sagittal and coronal planes in a saline bath before mechanical testing was conducted. Ultimate load to failure was reported for each shoulder. Data were analyzed by means of a paired t test and Wilcoxon signed-rank test. RESULTS: Ultrasound evaluation revealed several instances in groups 1/2 and contact areas A/B in which clear gap formation occurred without scar (collagen) interdigitation at the bone-tendon interface. Failures occurred at the bone-tendon repair site in all specimens during biomechanical testing. The mean load to failure for all specimens in group 1 was 350.7 N; it was 619.4 N for specimens in group 2 (P = .0002). In group 1, specimens with contact area A had a mean load to failure of 317.3 N; specimens with contact area B had a mean load to failure of 375.5 N (P = .15). In group 2, specimens repaired with contact area A had a mean ultimate load to failure of 635.8 N, whereas contact area B specimens had an ultimate failure strength of 688.5 N (P = .45; Wilcoxon signed-rank). CONCLUSIONS: Increasing the number of suture anchors and the surface area of the tendon that is in contact with bone at the repair site increased the ultimate load to failure of the repaired tendon at both 4 and 8 weeks postoperatively by less than 10% at both intervals. This was not a statistically significant increase in failure strength in this model. CLINICAL RELEVANCE: This animal model shows no statistically significant differences in strength at the repair site between a 2-anchor and a 4-anchor rotator cuff repair. This information may have direct clinical applications for the surgical technique employed in the repair of rotator cuffs.

Animals↗
PubMed2004

The effect of posterior tibialis tendon dysfunction on the plantar pressure characteristics and the kinematics of the arch and the hindfoot.

OBJECTIVE: To study posterior tibialis tendon dysfunction using an in vitro model of the foot and ankle during the heel-off instant of gait. BACKGROUND: Previous studies have concentrated primarily on the effect of posterior tibialis tendon dysfunction on the kinematics of the hindfoot and the arch. METHODS: The specimens were loaded using a custom designed axial and tendon loading system and the location of the center of pressure was used to validate heel-off. Arch position, hindfoot position and plantar pressure data were recorded before and after the posterior tibialis tendon was unloaded. These data were recorded with the ligaments intact and after creating a flatfoot deformity. RESULTS: Unloading the posterior tibialis tendon caused significant posterior movement in the center of pressure for the intact and flatfoot conditions. This also resulted in a medial shift in the force acting on the forefoot. The forefoot loads shifted medially after a flatfoot was created even when the posterior tibialis tendon remained loaded. The spatial relationships of the bones of the arch and the bones of the hindfoot also changed significantly for the intact specimen, and to a lesser extent after a flatfoot. CONCLUSIONS: The posterior tibialis tendon plays a fundamental role in shifting the center of pressure anteriorly at heel-off. Posterior tibialis tendon dysfunction causes posterior shift in the center of pressure and abnormal loading of the foot's medial structures. This may be the reason that posterior tibialis tendon dysfunction leads to an acquired flatfoot deformity. Conversely, flatfoot deformity may be a predisposing factor in the onset of posterior tibialis tendon dysfunction. This tendon also acts to lock the bones of the arch and the hindfoot in a stable configuration at heel-off, but a flatfoot deformity compromises this ability.

Biomechanical Phenomena↗
PubMed2004

Effects of glenohumeral rotations and translations on supraspinatus tendon morphology.

OBJECTIVE: The purpose of this study was to evaluate the effects of glenohumeral rotations and humeral head translations on supraspinatus tendon morphology. DESIGN: A convenience sample of cadaver shoulders was used to measure supraspinatus tendon shape and dimensions from MRI images. BACKGROUND: Epidemiological evidence has indicated that shoulder elevation and external rotation may be risk factors for rotator cuff tendon pathology, but little is known about how these postures affect tendon morphology. METHODS: Measurements of supraspinatus tendon morphology were made from three-dimensional reconstructions based on T2-weighted fast spin-echo magnetic resonance images. Seven cadaver arms were imaged at neutral, 45 degrees external and 45 degrees internal rotations at 0 degrees, 30 degrees, and 60 degrees of glenohumeral abduction. Measurements of the anterior, middle, and posterior portions of the tendon were made using ANALYZE software. RESULTS: The supraspinatus tendon was twisted at the muscle-tendon junction of the middle and posterior portions in 45 degrees external and 45 degrees internal axial rotations of the humerus, especially over 30 degrees of abduction. Abduction over 30 degrees shortened the entire supraspinatus tendon. External and internal rotation motions elongated the anterior and posterior portions, respectively. CONCLUSIONS: Arm posture affects morphology of the supraspinatus tendon. RELEVANCE: The results support the epidemiologic evidence linking external rotation and abduction to supraspinatus tendon disorders.

Aged↗
PubMed2005

Orientation of tendons in vivo with active and passive knee muscles.

Tendon orientations in knee models are often taken from cadaver studies. The aim of this study was to investigate the effect of muscle activation on tendon orientation in vivo. Magnetic resonance imaging (MRI) images of the knee were made during relaxation and isometric knee extensions and flexions with 0 degrees , 15 degrees and 30 degrees of knee joint flexion. For six tendons, the orientation angles in sagittal and frontal plane were calculated. In the sagittal plane, muscle activation pulled the patellar tendon to a more vertical orientation and the semitendinosus and sartorius tendons to a more posterior orientation. In the frontal plane, the semitendinosus had a less lateral orientation, the biceps femoris a more medial orientation and the patellar tendon less medial orientation in loaded compared to unloaded conditions. The knee joint angle also influenced the tendon orientations. In the sagittal plane, the patellar tendon had a more anterior orientation near full extension and the biceps femoris had an anterior orientation with 0 degrees and 15 degrees flexions and neutral with 30 degrees flexions. Within 0 degrees to 30 degrees of flexion, the biceps femoris cannot produce a posterior shear force and the anterior angle of the patellar tendon is always larger than the hamstring tendons. Therefore, co-contraction of the hamstring and quadriceps is unlikely to reduce anterior shear forces in knee angles up to 30 degrees . Finally, inter-individual variation in tendon angles was large. This suggests that the amount of shear force produced and the potential to counteract shear forces by co-contraction is subject-specific.

Adult↗
PubMed2005

Core suture purchase affects strength of tendon repairs.

PURPOSE: It generally is considered that a certain distance should be maintained between the site of the tendon-suture junction and the laceration level of the tendon. In this study we assessed how the length of core suture purchase may affect the repair strength of transversely cut tendons using a 2-strand modified Kessler method and a 4-strand circle-locking method. METHODS: Seventy-four fresh pig flexor tendons were transected. Fifty-eight tendons were divided into 4 groups and repaired with a 2-strand grasping repair technique with the core suture purchase in the tendon stump ranging from 0.4 to 1.2 cm. Sixteen tendons were repaired with a 4-strand circle-locking tendon-suture repair technique. The core suture purchase of these tendons was 0.4 and 1.0 cm, respectively. The tendons were subjected to a linear, noncyclic, load-to-failure test in a tensile testing machine. The forces measured for initial gap formation, 2-mm gap formation, and ultimate strength were recorded for each repair. RESULTS: The resistance to gap formation and ultimate strength of 2-strand grasping technique repairs increased significantly as the suture purchase increased from 0.4 to 0.7, 1.0, and 1.2 cm although strength remained constant from 0.7 to 1.2 cm. The strength of 4-strand circle-locking repairs with a suture purchase of 1.0 cm was statistically greater than that of the repairs with a suture purchase of 0.4 cm. CONCLUSIONS: For both the 2-strand grasping and 4-strand circle-locking repair methods, the length of core suture purchase significantly influences the resistance to 2-mm gap formation and the ultimate strength of repairs in transversely lacerated flexor tendons. We determined that the optimal length of purchase is between 0.7 and 1.0 cm and that increased length of purchase from 0.7 to 1.2 cm does not increase the strength of the repair. Core suture purchase length of 0.4 cm or less results in significantly weaker repairs.

Animals↗
PubMedDate not supplied

Entrapment of the long head of the biceps tendon: the hourglass biceps--a cause of pain and locking of the shoulder.

We describe an unrecognized mechanical condition affecting the long head of the biceps (LHB) tendon with entrapment of the tendon within the joint and subsequent pain and locking of the shoulder on elevation of the arm. We identified 21 patients with a hypertrophic intraarticular portion of the LHB tendon during open surgery (14 patients) or arthroscopic surgery (7 patients). All cases but one were associated with a rotator cuff rupture. Patients were treated by biceps tenotomy (2 patients) or tenodesis (19 patients) after removal of the hypertrophic intraarticular portion of the tendon and appropriate treatment of concomitant lesions. Minimum follow-up was 1 year. All patients presented with anterior shoulder pain and loss of active and passive elevation averaging 10 degrees to 20 degrees. A dynamic intraoperative test, involving forward elevation with the elbow extended, demonstrated entrapment of the tendon within the joint in each case. This test creates a characteristic buckling of the tendon and squeezing of it between the humeral head and the glenoid (hourglass test). The mean Constant score improved from 38 to 76 points at the final follow-up (P <.05). Complete and symmetric elevation was restored in all cases after resection of the intraarticular portion of the LHB tendon. The hourglass biceps is caused by a hypertrophic intraarticular portion of the tendon that is unable to slide into the bicipital groove during elevation of the arm; it can be compared with the condition of trigger finger in the hand. A loss of 10 degrees to 20 degrees of passive elevation, bicipital groove tenderness, and radiographic findings of a hypertrophied tendon can aid in the diagnosis. A definitive diagnosis is made at surgery with the hourglass test: incarceration and squeezing of the tendon within the joint during forward elevation of the arm with the elbow extended. The hourglass biceps is responsible for a mechanical block, which is similar to a locked knee with a bucket-handle meniscal tear. Simple tenotomy cannot resolve this mechanical block. Excision of the intraarticular portion of the LHB tendon, during bipolar biceps tenotomy or tenodesis, must be performed. The hourglass biceps is an addition to the familiar pathologies of the LHB (tenosynovitis, prerupture, rupture, and instability) and should be considered in cases of shoulder pain associated with a loss of elevation.

Aged↗
PubMed2005

Mechanical and functional properties of the equine superficial digital flexor tendon.

The in vitro and in vivo mechanical properties of the superficial digital flexor tendon have been described. To date the focus has been on single load to failure testing, however refined in vivo methods may prove useful to evaluate the effects of treatment and exercise on tendons. During maximal exercise, the adult superficial digital flexor tendon operates close to its functional limits with a narrow biomechanical safety margin. This combined with exercise and age associated microdamage, and a limited adaptive ability may increase the risk of fatigue failure. Studies evaluating treatment regimens for tendonitis have focused on repair and regeneration and yielded varying results. It would appear that the superficial digital flexor tendon has a limited ability if any to adapt positively to exercise after maturity. In contrast, the foal's superficial digital flexor tendon may have a greater adaptive ability and may respond to an appropriate exercise regimen to produce a more functionally adapted tendon. Recent studies have shown that foals allowed free pasture exercise develop a larger, stronger, more elastic tendon compared to foals that were confined or subjected to a training program. Effects on the non-collagenous matrix appear to be responsible for these differences. In contrast, training or excess exercise may have permanent detrimental effects on the biomechanical and functional properties of the superficial digital flexor tendon in the foal. The implication is that the determination of optimum exercise intensity and timing, and the role of the non-collagenous matrix in tendon physiology in the young horse may hold the key to developing tendons more capable of resisting injury.

Aging↗
PubMed1999

Magnetic resonance imaging and tendon anomaly associated with congenital superior oblique palsy.

PURPOSE: To assess the relationship between tendon anomalies and the volume of the superior oblique muscle in patients with congenital unilateral superior oblique palsy. METHODS: Thirty-three patients with unilateral congenital superior oblique palsy were enrolled. Coronal, cross-sectional magnetic resonance imaging scans of the superior oblique muscle were obtained, and the volume of the paretic superior oblique muscle belly was calculated as a percentage of the superior oblique muscle belly on the normal side. The percentage volume of the affected superior oblique muscle was compared retrospectively with the angle of the vertical deviation in the primary position, the tendon looseness determined by a traction test, and other intraoperative findings. RESULTS: When a tendon was loose, the volume of its muscle belly was significantly smaller than the belly of muscles with a normal taut tendon (Mann-Whitney U test, P = .0005). The average vertical deviation of patients assessed to have loose tendons was 4.80 prism diopters, and the deviation in patients with normal tendons was 9.90 prism diopters. The mean vertical deviation of patients with atrophic muscle belly on magnetic resonance imaging was 18.1 prism diopters, and that with normal muscle structure was 10.1 prism diopters. The cases with loose tendon as determined by the traction test after administration of general anesthesia and the cases with atrophic muscle belly had significantly larger vertical deviation in the primary position than the cases with normal tendons and muscles. (Mann-Whitney U test, P = .01 and .0196, respectively). CONCLUSIONS: The traction test is sensitive enough to detect anomalies of the superior oblique tendons. Anomalous superior oblique tendons are nearly always associated with attenuated superior oblique muscle and this information provides us with an explanation for the phenomenon of laxity of the superior oblique tendon.

Adolescent↗
PubMed2003

Proteoglycans in chicken gastrocnemius tendons change with exercise.

Growth, loading, and mobilization lead to changes in tendon structure. Recent studies have shown that proteoglycans (PGs) regulate the organization of collagen fibrils, the main structural components of tendons. We hypothesized that moderate exercise alters PG synthesis in the avian gastrocnemius tendon. To test our hypothesis we compared the PG content in gastrocnemius tendons from control 6.5-week-old chickens with that in tendons from 6.5-week-old chickens that underwent exercise. Our results show high levels and a wide variety of glycosaminoglycans (GAGs) in 6.5-week-old tendons. Chondroitin-4-sulfate disaccharide was the major GAG disaccharide in control and exercised 6.5-week-old gastrocnemius tendons. Exercise led to an increase in the size of the tendons, the content of hyaluronic acid, and the level of decorin. High levels of keratan sulfate (KS) were found in the lower halves of gastrocnemius tendons, although the amount of KS decreased with exercise. This corresponded well with lower content of aggrecan in the lower halves of exercised tendons. In conclusion, our data support the hypothesis that exercise alters the content of PGs in chicken tendons.

Aggrecans↗
PubMed1999

Biomechanical properties of muscle-tendon unit under high-speed passive stretch.

OBJECTIVE: The purpose of this study was to investigate the strain injury mechanisms of the Achilles muscle-tendon unit during high-speed passive stretch. DESIGN: The high-speed traction device consisted of an impactor which dropped freely to hit one end of a lever, transferring the impact energy to traction energy at the other end. A muscle-tendon unit was attached to the other end of the lever via a force link, and the elongation was recorded with a high-speed camera. BACKGROUND: The muscle-tendon unit is thought to act viscoelastically. It is generally strain rate dependent, exhibiting higher tensile stress at faster strain rates. However, previous studies of passive stretch in muscle-tendon units usually employed low strain rates. METHODS: 16 fresh Achilles muscle-tendon units were subjected to passive stretch at a test speed of 310 cm s(-1). The history of elongation and the traction force of the muscle-tendon unit during the elongation process were analyzed. RESULTS: The muscle-tendon units exhibited highly nonlinear mechanical behavior. Most of the elongation occurred in muscle and resulted in structural failure. Failure was not found in the tendon or muscle-tendon junction. Muscle fibers during stretching reached their maximum mechanical strength and then progressively ruptured. CONCLUSION: The strain rate is an important factor in strain injuries of the muscle-tendon unit due to passive stretch. The muscle is a good energy absorber; the rupture process can absorb a great deal of external energy and prevent complete failure of the muscle, while also protecting bone and joints. RELEVANCE: The study of muscle-tendon unit under high-speed stretch could help us to understand the mechanism of strain injuries over passive stretch in real-life situations.

Achilles Tendon↗
PubMed1999

Mechanical properties of collagen fascicles from stress-shielded patellar tendons in the rabbit.

OBJECTIVE: To know the effects of stress shielding applied to the patellar tendon on the collagen fascicles. DESIGN: The mechanical properties of collagen fascicles obtained from stress-shielded patellar tendons were compared to those of collagen fascicles from non-treated patellar tendons and those of stress-shielded bulk patellar tendons in the rabbit. BACKGROUND: Effects of stress deprivation and stress enhancement on the mechanical properties of knee joint tendons and ligaments have been extensively studied in various animal models. However, the roles of such substructural components as collagen fascicles in the remodeling of tendons and ligaments have not been studied well. METHOD: Tensile and viscoelastic properties of collagen fascicles obtained from the rabbit patellar tendons which were completely stress-shielded for 1 to 3 weeks by a special method developed by the authors were determined using a micro tensile tester. RESULTS: Stress shielding significantly decreased the tangent modulus, tensile strength, and strain at failure of collagen fascicles. However, these changes were much smaller than those observed in bulk tendons. The relaxation of stress-shielded collagen fascicles was greater than that of non-treated ones. CONCLUSIONS: Ground substance and mechanical interaction between collagen fascicles have important roles in the remodeling of tendons and ligaments. RELEVANCE: Knowledge of the role of such substructural components as collagen fascicles in the remodeling of tendons and ligaments is essential not only to the basic biomechanics of knee joint tendons and ligaments but also to the development of their reconstruction methods using autografts.

Animals↗
PubMed1995

The flexor digitorum longus: an anatomic and microscopic study for use as a tendon graft.

Recent experimental studies have shown that intrasynovial donor tendons have the capacity to heal with minimal alteration in the gliding surface when grafted to an intrasynovial location. In order to evaluate the flexor digitorum longus of the foot as a potential matched donor tendon for use in flexor tendon grafting, we dissected 15 feet (75 toes) and 10 hands (50 fingers) to determine the intrasynovial lengths of the flexor digitorum longus and flexor digitorum profundus and to determine a method of tendon graft harvest. Specimens were taken from the intrasynovial portion of each tendon for evaluation by light and electron microscopy. The intrasynovial tendons of the hand and foot were similar in vascularity, cellularity, gliding surface, and ultrastructure. The flexor digitorum longus tendon of the foot was a mean length of 12 cm to the area of tendon confluence in the midfoot, which will usually provide enough tendon length for grafting from the distal phalanx to the palm of the hand. Because of the difference in length of the synovial sheaths of the fingers and toes, some extrasynovial tendon will be transferred to the synovial space when a flexor digitorum longus tendon is used.

Cadaver↗
PubMed1996

Biomechanical and histologic evaluation of tendon sheath management.

The effect of changes in diameter of the flexor sheath after tendon repair on tendon function was studied using the long toes of 64 white leghorn chickens. Biomechanical studies of gliding excursion, toe flexion, and ultimate load were carried out at 6 and 12 weeks after tendon repair to determine functions of the tendons healed in narrowed, directly closed, partially excised, and enlarged flexor sheath experimental groups. Histologic examination was used to evaluate the extent of adhesions, healing status of the tendons, and status of the managed sheath. At 6 weeks, gliding excursions and range of toe flexion were statistically the smallest in the group with sheath narrowing, statistically larger in the groups with direct sheath closure or sheath excision, and statistically the largest in the sheath enlargement group (p < .01). These differences in gliding excursions and range of toe flexion were persistently observed at 12 weeks. The ultimate load of the repaired tendons was statistically the weakest in the group with sheath narrowing at either 6 or 12 weeks (p < .01). However, the ultimate load of the groups with sheath enlargement, direct sheath closure, and partial sheath excision was statistically the same. Results of histologic examination demonstrated more severe adhesions and worsened tendon healing in specimens with sheath narrowing. The repaired tendons in the group with sheath enlargement healed better and had less severe peritendinous adhesions than those in the group with sheath narrowing. The extent of adhesions and tendon healing were similar in the groups with sheath enlargement and direct sheath closure. This study demonstrates that the diameter of the repaired sheath exerts significant influence on flexor tendon function. Enlargement of the digital flexor sheath may provide an additional way to improve function of repaired tendons.

Animals↗