Hand is a unique structure in the human body making everyday tasks in life easy and simple. It has got fine movement skills and high sensitivity. Because of its function it has got a relatively great representation in the brain. The invaluable use of hands is not realized unless it is disabled. Injury of hands is commonly encountered in the emergency department (1,2). Patients with tendon injuries form 29% of all patients treated for hand injuries (1). The extensor tendons are more prone for injury due to their superficial location (3,4). The extensor tendons of thumb are commonly injured (25.7%), followed by middle finger (24.8%), and the small finger was least affected (10.5%) (5).
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The results of our controlled laboratory study support the assumption that the aforementioned findings from ro- tator cuff studies are valid for the elbow, too. We found the double row repair technique to be significantly stron- ger than the single row technique for both the common extensor and flexor origin repair. Even though reasons for this finding have not been assessed, several arguments can explain these findings. First of all, the use of an additional suture anchor has probably added further stability to the repair. Furthermore, the resultant double row construct allowed for a better distribution of the loading forces and thus were probably able to withstand significantly higher loads compared to the single row repair technique before failing . Finally, a further known advantage of knotless fixation and thus a potential contributing factor to in- creased fixation strengths is the consistency in the fixation strengths, as previous studies have demonstrated that hand-tied knots have a high variability of strength [20, 21]. Of note, the vast majority of our constructs failed at the suture-tendon-interface with the sutures cutting out of the tendon. This mode of failure is typical for tendon- to-bone repairs and generally considered to be the weak spot of the repair .
Thirty-six ruptured extensor tendons derived from four- teen RA patients (11 women and three men) were recon- structed during the period Feb. 2000 to Feb. 2004 inclusively. (Table 1) The mean age of study participants at time of surgery was 47.3 years (range, 32–66 years) and their mean of time lag between tendon rupture and sur- gery was 9.4 weeks. (range, 2 to 24 weeks) All of the involved patients have received some level of medical treatment for their arthritic condition. No patient had undergone any previous surgical treatment to their hand. Larsen's x-ray classification  was used to assess the rela- tive severity of the rheumatoid arthritis from which each study participant suffered. In each case, we reconstructed extensor tendons using a section of autogenous palmaris longus tendon as a free interpositional tendon graft. The presence of this tendon was determined before grafting
it has been shown that energy storing tendons exhibit greater fati- gue resistance than positional tendons [6,7]. Indeed, the time to rupture for highly stressed wallaby flexor tendons is approxi- mately 10–20 times greater than that for extensor tendons, which experience much lower stresses in life . In the current study, we applied a maximum load equivalent to 50% of the predicted failure force. The energy storing SDFT is predicted to experience loads of up to 80% of failure force in vivo during intense exercise [3,24]. By contrast, maximum forces in the positional CDET are unlikely to exceed 25% of the tendon’s failure force [3,24]. It has not been established how much load an individual fascicle may experience in vivo, but it is likely that the forces applied in the current study far exceed those experienced in vivo by the CDET, which may explain the extremely low fatigue resistance of the fascicles from this positional tendon. It has previously been established that load- ing of tendons to the stress they experience ‘in life’ results in a sim- ilar time to failure for all tendon types [7,24]. It is not possible to perform these type of experiments at the micromechanical level, as the stress in life experienced by fascicles and IFM in functionally distinct tendons is yet to be determined.
A major feature of the Scx –/– phenotype, the dorsal flexure of the forelimb paw, can be explained by a specific loss of flexor tendon activity, such that dorsal extension is not counteracted by flexor tendon activity. We therefore decided to analyze the flexor and extensor tendons in Scx –/– mutants in detail. In wild type mice, there are two major flexor tendons in the autopod, shown schematically in Fig. 4A. The flexor digitorium profundus (FDP) tendons insert at the distal joint of each digit and extend along the digits and metacarpals, fusing to a seemingly continuous tendon sheath at the proximal end of the metacarpals (Fig. 4A, green). The flexor digitorium superficialis (FDS) tendons insert more proximally, at the second digital joint, and bifurcate to wrap around the FDP tendons, subsequently fusing to a single tendon ventral to the FDP at the metacarpal level (Fig. 4A, red). The morphology and relative organization of these tendons in cross sections are therefore excellent indicators for the proximal-distal position within the autopod. In Scx –/– mutants, we found smaller FDP tendons and only rudimentary FDS tendons when compared with wild-type in cross sections through the digits (Fig. 4B,E) and at the metacarpal- phalangeal joint (Fig. 4C,F). However, at metacarpal levels, both flexors were completely absent, replaced by clouds of unorganized ScxGFP-positive cells (Fig. 4D,G, yellow arrowheads). Conversely,
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flexor tendons and also, more marginally, the plantaris tendons appear of excessive fatigue quality. A reason for this may be that toe flexor tendons are more likely than toe extensor tendons to be subjected to stresses higher than those attributed in our calculations of stress-in-life. The flexor tendons are branched, and assigning equal stress to each branch may underestimate the maximum stress achieved in normal life. If a single toe lands on a stone, while the other toes are unsupported, its branch of the flexor tendon may be excessively loaded. Furthermore, although we have argued above that flexor muscles are unlikely to produce forces above their maximum isometric force in steady locomotion, they may well do so when running downhill or decelerating and when landing from a jump. Had we been able to allow for such factors in assessing the stress to be applied in the experiments leading to Fig. 5, the points for the flexor tendons would have moved to lower times-to-rupture. A modest shift in this way would serve to strengthen the main conclusion, which is that all tendons appear similarly prone to fatigue rupture, when tested under conditions related to those they experience in life. Young’s modulus
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Dissection of the forelimb revealed that extensor muscles of the digits were originated normally from the lateral surface of the radius, but their tendons were run at the lateral border of the radius to the carpal joint and finally deviated to the caudolateral aspect of the carpal joint to reach to the metacarpal bone. At the metacarpal region according to the outward bending of the forelimb distal to the carpal joint, extensor tendons run slightly to the cranial surface. It had resulted in the change of dorsopalmar axis of metacarpal to the lateromedial one. According to this change, extensor digital tendons in the metacarpal region were observed on the lateral surface of the metacarpal bone but their divisions were normal proximal to the fetlock. Due to these events, normal lateromedial arrangement of the extensor tendons of the metacarpal region had been changed to the caudocranial position (Fig. 1). The cranial tendon, extensor digitrum communis, was divided into the two lateral and medial branches proximal to the fetlock. Medial branch was continued to the medial digit while lateral one divided to two lateral and medial branches which were run to the lateral and medial digits, respectively. The tendon of caudal muscle, extensor digitrum lateralis, was continued to the lateral digit similar to normal arrangement.
In consideration of the clinical importance of the distri- bution of the DBRN, we dissected 32 upper limbs to de- termine whether the branching pattern of the DBRN var- ied between the forearms possessing single versus double tendons of EI. The radial nerve arose from the posterior cord of the brachial plexus and incorporated the anterior primary rami of C5-T1 spinal nerves. From the axillary fossa, it wound around the posterior aspect of the humerus and pierced the lateral intermuscular septum to enter the anterior compartment of the arm dividing into superficial and deep terminal branches. In the literature, the DBRN is frequently called the posterior interosseous nerve (PIN). 31
I . F . Wi l l iams ( Dept . of Pathology , School of Veter i na r y Sciences , Un iversi ty of Br isto l ) . The protocol for bacter ial col l agenase t reatment and the subsequent cl i nical and post-mortem observat i ons are deta i led in Append i x 5 . The controls for these exper linents were taken from the contralateral tend ons of the affected animal s and the collagen f ibr i l d iameter d i str ibu t i ons from these tissues were p lotted as bo th number and volume d istr ibuti ons in Figure 5 . 7 . The form of the d i str ibut ions obta i ned from the horse four weeks after bacter ial col lagenase treatment is character istic of a young animal ( see Parry et a l . , 197 8b) . The frequency and volume d i str ibut i ons of the col l agen f ibr i l s measured i n the bacter ial collagenase treated tendons are shown i n Figure 5 . 8 . The forel lltib flexor o f a normal horse has a col l agen fibr i l d iameter d istr ibut ion which is both broad and bimodal . The two peaks in the d i str ibution have mean d i ameter s o f about 35 and 165 nm and conta in about 90 and 10% respectively of the number of f ibr i l s in the d i str ibut i on ( see Parry et al . , 1978b ; Figure 5 . 9a) . Wi th i n a day o f col lagenase treatment the sma ll d i ame ter f ibr i l s had completely d isappeared and the largest d iameter fibr i l s had apparently been part ia l ly degraded to f ibr i l s of i ntenned iate s i ze . The a f fected part of the tendon then conta i ned a unimodal d istr ibut ion of fibr i l d iameter s (mean d i ameter 73 . 1 i 10 . 7 nm , mass-average d iameter 76 . 7 nm; F igure 5 . 9b) which , in higher resol ution m icrog raphs , have been resolved i nto a d i screte number o f populat i ons (Tables 5 . 1 , 5 . 2 ) each with a mean d i ameter
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Collagen is the most abundant protein in the human body and the major component of tendon tissue. Tendon tissues are composed of around 90% Type I, 10% Type III and small amounts of other types of collagens (Thorpe et al., 2015). Type I and Type III collagen have been used extensively for medical devices, as coating, individual components, or whole devices prepared and assembled in various forms. The electrochemically aligned collagen threads have already successfully produced from commercial bovine collagen and lab extracted collagen from lamb skin by Dr. Ozan Akkus and his research group in Case Western Reserve University (Webster, 2015; Islam, 2015). Porcine patella tendons have also been used for extracting collagen in the lab, which however were not be able to yield high concentrated collagen solution required for collagen threads fabrication. Therefore, the rat tail tendons were selected which have a high collagen content, and have been widely used in the extraction and preparation of commercial collagen products available on the market. This chapter discusses the extraction and characterization of the collagen material that was used for producing the electrochemically aligned collagen yarns that were used in this study.
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Which condition or stimulus is able to cause this erro- neous differentiation of TDSCs? Many proteins could be involved in tendon degeneration, calcification and rear- rangement processes, playing different roles in the var- ious phases of calcification and resorption. Among the possible candidates are bone morphogenetic proteins (BMPs) and transglutaminases (TGs). Recently, Zang and Wang suggested that BMP-2-mediated effects on human TDSCs may contribute to the formation of calci- fic deposits in CT . We observed an increased expression of osteopontin, cathepsin K and TG2 mRNA in the calcific areas of the supraspinatus tendon as com- pared to what observed in the normal tissue . TG2 is ubiquitously expressed, and plays a role in a variety of cellular processes, including the crosstalk between macrophages and apoptotic cells, glucose tolerance and other processes. It is also important in maintaining the structural integrity of tendons and it could be involved in tendon repair . The increased expression of osteo- pontin and TG2 could thus be compatible with their increased production in the calcific area, probably by osteoclast-like cells involved in the resorptive phase . The mRNA and protein expression of major proteo- glycans of extracellular matrix, including decorin, aggre- can, biglycan and fibromodulin and their relationship
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In the pretensioning system, the tenders are first tentioned between rigid anchor blocks cast on the ground or in a column or unit mould type pretensioning bed, prior to the casting of the concrete in the moulds. The tendons comprising individual wires or stands are stretched with constant eccentricity or variable eccentricity withtendon anchorage at the one end and jacks on other. With the forms in place, the concrete is cast around the stressed tendon.
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In the past few decades, with the advancement of surgi- cal techniques, tumor prosthesis replacement has been increasingly accepted by orthopedic oncology surgeons , and limb salvage therapy has gradually become a mainstream approach. However, postoperative complica- tions — such as aseptic loosening of the prosthesis, pros- thesis rupture, infection, and dislocation — are reportedly higher after tumor prosthesis replacement [7, 18]. The most urgent problem after resection of a proximal tibial tumor is the reconstruction of the extensor mechanism and the risk of postoperative infection. The transfer of a gastrocnemius muscle flap reduces the risk of postopera- tive infection and facilitates effective reconstruction of the extensor mechanism (Pedicled Rotational Medial and Lateral Gastrocnemius Flaps: Surgical Technique). However, the application of the above technology is not perfect, and the main concern is the challenge of recon- structing extensor lag. The prevention of the above symptoms has also become a major concern for sur- geons. The inadequacy of postoperative extensor func- tion is the driving force for the surgeon to improve his or her surgical technique. This study discusses the role
hand tendons by initiating creep and then applying a sudden change in temperature. They carried out a series of experiments with the same tendon using different creep stresses. Clearly rupture and, indeed, damage had to be avoided. Nemetschek and co-workers (Nemetschek et al. 1978; Folkhard et al. 1987) carried out creep experiments as part of their wide-ranging investigations, by X-ray diffraction, into changing the 67 nm repeat of the collagen molecule. However, it appears that they did not allow their tests to continue to failure. Many studies aim to describe the time- dependent mechanical properties of tendons and ligaments using mathematical models, either directly by expressing stress as a function of strain history or indirectly by analogy to an array of springs and dashpots. Viidik (1980) reviews both versions. The models assume that the tendon material is unaltered by creep, just as a dashpot demonstrates creep but is not thereby damaged. The parameters required by a model are best measured by applying a range of tests to the same tendon, whilst avoiding damage.
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The word pronator comes from the Latin pronus and translate to “inclined forward or lying face downward”, which describes the action of pronator teres on the forearm. The Latin term teres means “round or cylindrical shaped” or “long and round”, which describes the shape of the muscle. PT is located on the volar aspect of the fo- rearm, and functions to rotate the forearm palm-down (pronation) with pronator quadratus (PQ). The muscle originates from two heads (humeral and ulnar) and at- taches onto the lateral aspect of the radius. The humeral head is larger and shallower, and begins above the medial epicondyle, at the medial supracondylar ridge with the other common flexor tendons. The ulnar head originates below the elbow on the medial aspect of the coronoid process of the ulna. The two heads come together, cross the forearm diagonally, and insert halfway down the lateral surface of the radius via a tendon.
Tests were performed over various stress ranges, at frequencies of 1.1, 2.1, 5.3, 10 and 50 Hz. The length of the tendon samples tested at 1.1, 5.3 and 10 Hz was about 120 mm. At 50 Hz, shorter tendons (40 mm) were used because the amplitude that the Instron machine can achieve is limited at high frequencies. To control for possible effects of specimen length, 40 mm specimens were also used in the tests at 2.1 Hz. The length of specimens may affect their mechanical properties (Wang and Ker, 1995), so we do not attempt to compare the results between different specimen lengths in this paper.
Tendon data were analyzed using SAS/STAT software, Ver- sion 9.1 of the SAS System for Windows (SAS Institute, Cary, NC). A mixed model two-factor within-subject anal- ysis of variance (ANOVA) was used to conduct the initial statistical analysis. The design factors included age and loading treatment (i.e. stretch-shortening cycle treatment or limb). Since tendons from both limbs were assessed, animal was included as a random effect to appropriately model the covariance structure. Data that were normal- ized to the untreated limb were analyzed using one-way ANOVAs with age as the factor. Post hoc comparisons were also carried out using Fishers Least Significant Differ- ence method. All differences and effects were considered significant if p < 0.05. All data are depicted as the mean value ± standard error.
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Nayak et al.  and Mehta et al.  presumed an embryological basis for the accessory APL tendons. The differentiating APL tendon is divided into 3 slips attached to trapezium, first metacarpal and opponens pollicis. Subsequently, new attachments may develop to adjacent abductor pollicis brevis, whereas the link with the opponens pollicis disappears. In the current research, this could be explained by the presence of transverse tendinous fibres connecting the various APL tendons. Also, Van Oudenaarde  detected a link by a web of synovium between the main and the accessory APL tendons, with the presence of a bursa between them.
The molecular nature of the interaction between the muscle and tendon at this stage has not been elucidated. However, the expression of Fgf4 at the extremities of limb muscles and of FGF target genes (e.g. sprouty) at the extremities of limb muscles in differentiating tendons, combined with the ability of exogenous FGF to induce Scx in muscle-less limbs, suggest the possible involvement of FGF signaling in tendon differentiation (Edom- Vovard et al., 2002; Eloy-Trinquet et al., 2009). An intriguing aspect of this model is the suggestion that tendon differentiation in both vertebrate and Drosophila embryos occurs through the activation of a tyrosine kinase receptor in the tendon progenitors by a ligand secreted from the muscle. In vertebrates, however, the muscle signal is likely to affect mostly the differentiating tenocytes (see Glossary, Box 2) at the myotendinous junction. It is therefore possible that tenocyte differentiation through the length of the tendon depends on the propagation of cellular interactions from a solid anchor in the form of the myotendinous junction. A similar essential role for the cartilage in tendon differentiation has not been shown to date, suggesting that the effect on tendon differentiation could be unique to muscles or that a mutant with an adequate disruption of cartilage differentiation has not been identified so far.
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Moreover, the results of this ex vivo study reflect only the initial mechanical characteristics of the complex for the ACL reconstruction without any biologic healing and remodelling responses. So caution should be used in extrapolating the results of our study to clinical estimates as we cannot assume that the structural properties of fixa- tion devices determined in animal tissue and laboratories studies predict its performance in human knees. On the other hand, this study was performed in the laboratory of our university by a team with substantial experiences in biome- chanics of ligaments and tendons [16, 20, 21].