Development and ageing of phenotypically distinct fibrocartilages associated with the rat Achilles tendon

Summary We describe by routine histology and by immunohistochemistry three phenotypically and developmentally distinct fibrocartilages associated with the Achilles tendon of the rat. All the fibrocartilages develop after birth and show significant age-related changes in the composition of their extracellular matrix. Attachment-zone fibrocartilage occurs at the insertion of the tendon on the calcaneus. It derives from the cartilage rudiment of the calcaneus and from the region where the tendon merges with the perichondrium. The extracellular matrix contain type II collagen and chondroitin sulphate. Compressive tendon fibrocartilage occurs in the deep part of the tendon where it presses against the calcaneus, and is derived by metaplasia of tendon cells. The cells label strongly for the intermediate filament vimentin, and the extracellular matrix contains chondroitin and keratan sulphates, but type II collagen only in very old animals (>2 years). Calcaneal fibrocartilage covered the posterior surface of the calcaneus where it was in contact with the Achilles tendon. It labelled intensely for type II collagen and contained chondroitin and keratan sulphates. The cells were rich in vimentin. This fibrocartilage was derived from the calcaneal perichondrium.     

Fetal and postnatal development of the patella, patellar tendon and suprapatella in the rabbit; changes in the distribution of the fibrillar collagens

The development of the patella, its associated tendons, and suprapatella of the rabbit knee joint is described from the 17 d fetus to the mature adult. The patellar tendon (ligament) with the patella on its posterior surface is seen in the 17 d fetus and is fully developed by 1 postnatal wk. It is composed of bundles of types I and V collagens separated by endotenons of types III and V collagens. Anteriorly there is an epitenon of types III and V collagens while synovium and a fat pad cover its posterior surface. In the 25 d fetus, the patella is cartilaginous and is separated from the femoral condyles. The cartilage contains type II collagen, but types I, III and V collagens are found along the articular surface. Ossification starts 1 postnatal wk and at 6 wk only the articular cartilage remains. In addition to type II, types III and V collagens are located around the chondrocyte lacunae. The long anterior junction between the patella and its tendon is fibrocartilaginous at 1 wk, but as ossification proceeds this is replaced by bone. Types I and V collagens are found in this region. The suprapatella on the posterior surface of the quadriceps tendon is first seen 1 wk postnatally as an area of irregularly organised fibres and chondrocyte-like cells. Types I, II, III and V collagens are present from 3 wk onwards. It is compared with the fibrocartilage of other tendons that are under compression. The arrangement of the collagens in the patellar tendon is discussed in relation to its use as a replacement for injured anterior cruciate ligaments. It is suggested that the structural differences between the patellar tendon and anterior cruciate ligament preclude the translocated tendon acquiring mechanical strength similar to that of a normal cruciate ligament. The designation 'patellar ligament' as opposed to 'patellar tendon' is questioned. It is argued that the term patellar tendon reflects its structure more accurately than patellar ligament.     

The interface between bone and tendon at an insertion site: a study of the quadriceps tendon insertion

Traumatic avulsions of ligament or tendon insertions rarely occur at the actual interface with bone, which suggests that this attachment is strong or otherwise protected from injury by the structure of the insertion complex. In this study we describe the terminal extent of quadriceps tendon fibres where they insert into the patellae of adult rabbits, humans, dogs and sheep. Specimens were examined by scanning electron microscopy (SEM) and light microscopy (LM). To facilitate tracing of tendon fibres the specimens were decalcified for SEM, and polarised light microscopy (PLM) was used in the LM segment of the study. By SEM it was possible to identify mature bone by the presence of osteocytes and a lamellar organisation. PLM and SEM showed that, unlike tendon fibres elsewhere, those in the calcified fibrocartilage were not crimped. No specific cement line was identified by SEM. Tendon fibres interdigitated among separate bone lamellar systems, (osteons or marrow spaces), but did not merge with the collagen systems of individual lamellae. The interdigitation was more extensive and the margin between tendon and bone was less distinct in the anterior third of the insertion. The segment of calcified tendon which interdigitated with bone stained less intensely blue and was less cellular than the more proximal calcified fibrocartilage zone adjacent to the tidemark. Lamellar collagen fibres of the bony trabeculae in the anterior patella were unusually parallel and longitudinal in orientation, making distinction of interposed tendon fibres difficult on LM and PLM sections. LM, SEM and transmission electron microscopy of rabbit patellae at birth revealed that anterior quadriceps tendon fibres extended over the patella in a fibrous cellular layer. By 2 wk of age, this layer had acquired chondroid features (i.e. cell lacunae and metachromasia) and contained vessels extending from patellar marrow. At 6 wk of age, part of this fibrocartilaginous layer was replaced by mature bone and osteoid. In the young adult animal, the quadriceps tension interdigitates extensively with the patellar bone. This segment of the insertion is perhaps the remnant of calcified fibrocartilage which has been remodelled by bone formation.     

Changes in the mechanical properties or rat tail tendon during postnatal ontogenesis

Summary The ultimate tensile strength, elasticity modulus and ultimate elongation of tail tendon in rats aged 1–18 months were measured with an Instron tensile apparatus. An increase in all these parameters was observed during the period of maturation, with a later levelling off of the tensile strength and the ultimate elongation. The value of the elasticity modulus attained a maximum during sexual maturation, and then decreased and stabilized.     

Development of the tendon of todaro during the human embryonic and fetal periods

This study covers the development of Todaro's tendon during human embryonic and fetal periods. The tendon primordium first appears when human embryos attain a CR length of 22 mm, but it only becomes well-defined at 24 mm CR length. The tissue that will form the tendon proceeds exclusively from the inferior endocardial cushion. The tendon establishes a close relationship with the base of the septum secundum during its path towards the right venous valve, carrying myocardial tissue out and forming the fasciculus limbicus inferior to muscular tissue. The tendon's relationship with the superior aspect of the atrioventricular node primordium during the first part of its path is of particular interest. The relationship is most intriguing when the node morphology is least defined. This would explain the possible embryogenesis of extra atrioventricular nodes. We also consider Todaro's tendon to be largely responsible for the development of the sinus band which protrudes as a crest inside the right atrium. This band is particularly well-developed in the fetal heart and provides an explanation for the large sub-Eustachian sinus cavity. © 1994 Wiley-Liss, Inc.     

No donor age effect of human serum on collagen synthesis signaling and cell proliferation of human tendon fibroblasts

The aging process of tendon tissue is associated with decreased collagen content and increased risk for injuries. An essential factor in tendon physiology is transforming growth factor-β1 (TGF-β1), which is presumed to be reduced systemically with advanced age. The aim of this study was to investigate whether human serum from elderly donors would have an inhibiting effect on the expression of collagen and collagen-related genes as well as on cell proliferative capacity in tendon cells from young individuals. There was no difference in systemic TGF-β1 levels in serum obtained from young and elderly donors, and we found no difference in collagen expression when cells were subjected to human serum from elderly versus young donors. In addition, tendon cell proliferation was similar when culture medium was supplemented with serum of different donor age. These findings suggest that factors such as the cell intrinsic capacity or the tissue-specific environment rather than systemic circulating factors are important for functional capacity throughout life in human tendon cells.     

Regional differences in cell shape and gap junction expression in rat Achilles tendon: relation to fibrocartilage differentiation

Tendon cells have complex shapes, with many cell processes and an intimate association with collagen fibre bundles in their extracellular matrix. Where cells and their processes contact one another, they form gap junctions. In the present study, we have examined the distribution of gap junction components in phenotypically different regions of rat Achilles tendon. This tendon contains a prominent enthesial fibrocartilage at its calcaneal attachment and a sesamoid fibrocartilage where it is pressed against the calcaneus just proximal to the attachment. Studies using DiI staining demonstrated typical stellate cell shape in transverse sections of pure tendon, with cells withdrawing their cell processes and rounding up in the fibrocartilaginous zones. Coincident with change in shape, cells stopped expressing the gap junction proteins connexins 32 and 43, with connexin 43 disappearing earlier in the transition than connexin 32. Thus, there are major differences in the ability of cells to communicate with one another in the phenotypically distinct regions of tendon. Individual fibrocartilage cells must sense alterations in the extracellular matrix by cell/matrix interactions, but can only coordinate their behaviour via indirect cytokine and growth factor signalling. The tendon cells have additional possibilities — in addition to the above, they have the potential to communicate direct cytoplasmic signals via gap junctions. The formation of fibrocartilage in tendons occurs because of the presence of compressive as well as tensile forces. It may be that different systems are used to sense and respond to such forces in fibrous and cartilaginous tissues.     

Where tendons and ligaments meet bone: attachment sites ('entheses') in relation to exercise and/or mechanical load

Entheses (insertion sites, osteotendinous junctions, osteoligamentous junctions) are sites of stress concentration at the region where tendons and ligaments attach to bone. Consequently, they are commonly subject to overuse injuries (enthesopathies) that are well documented in a number of sports. In this review, we focus on the structure-function correlations of entheses on both the hard and the soft tissue sides of the junction. Particular attention is paid to mechanical factors that influence form and function and thus to exploring the relationship between entheses and exercise. The molecular parameters indicative of adaptation to mechanical stress are evaluated, and the basis on which entheses are classified is explained. The application of the 'enthesis organ' concept (a collection of tissues adjacent to the enthesis itself, which jointly serve the common function of stress dissipation) to understanding enthesopathies is considered and novel roles of adipose tissue at entheses are reviewed. A distinction is made between different locations of fat at entheses, and possible functions include space-filling and proprioception. The basic anchorage role of entheses is considered in detail and comparisons are explored between entheses and other biological 'anchorage' sites. The ability of entheses for self-repair is emphasized and a range of enthesopathies common in sport are reviewed (e.g. tennis elbow, golfer's elbow, jumper's knee, plantar fasciitis and Achilles insertional tendinopathies). Attention is drawn to the degenerative, rather than inflammatory, nature of most enthesopathies in sport. The biomechanical factors contributing to the development of enthesopathies are reviewed and the importance of considering the muscle-tendon-bone unit as a whole is recognized. Bony spur formation is assessed in relation to other changes at entheses which parallel those in osteoarthritic synovial joints.     

Histopathological and biomechanical evaluation of tenocyte seeded allografts on rat Achilles tendon regeneration

Tendon injuries in humans as well as in animals' veterinary medicine are problematic because tendon has poor regenerative capacity and complete regeneration of the ruptured tendon is never achieved. In the last decade there has been an increasing need of treatment methods with different approaches. The aim of the current study was to improve the regeneration process of rat Achilles tendon with tenocyte seeded decellularized tendon matrices. For this purpose, Achilles tendons were harvested, decellularized and seeded as a mixture of three consecutive passages of tenocytes at a density of 1 × 10⁶ cells/ml. Specifically, cells with different passage numbers were compared with respect to growth characteristics, cellular senescence and collagen/tenocyte marker production before seeding process. The viability of reseeded tendon constructs was followed postoperatively up to 6 months in rat Achilles tendon by histopathological and biomechanical analysis. Our results suggests that tenocyte seeded decellularized tendon matrix can significantly improve the histological and biomechanical properties of tendon repair tissue without causing adverse immune reactions. To the best of our knowledge, this is the first long-term study in the literature which was accomplished to prove the use of decellularized matrix in a clinically relevant model of rat Achilles tendon and the method suggested herein might have important implications for translation into the clinic.     

Temperospatial Expression of Matrix Metalloproteinases 1, 2, 3, and 9 During Early Tooth Development

Odontogenesis involves a complex series of processes including epithelial-mesenchymal interactions, morphogenesis, differentiation, fibrillogenesis, and mineralization. Extracellular (ECM) remodeling plays a critical role in the rapid morphological changes that accompany these events. It is proposed that matrix metalloproteinases (MMPs) participate in the remodeling of tooth-specific matrices that accompanies the developmental events. MMPs are zinc-requiring endopeptidases that are centrally involved in the controlled turnover of ECM components and are key to a varied range of developmental processes. Thus, the aim of this study was to examine the expression of MMPs 1, 2, 3, and 9 within the developing tooth germ of Wistar rats, using immunohistochemical localisation. During the bud stage, MMPs 1, 2, 3, and 9 were expressed within both epithelial and mesenchymal cells. Later on, during the cap stage, differential expression was observed; of note was the expression of MMP 3 within the enamel knot. This study reports the temperospatial expression of MMPs 1, 2, 3, and 9 during early tooth development, and points to them having a key role during this important developmental period.     

Cell and matrix biology of the suprapatella in the rat: A structural and immunocytochemical study of fibrocartilage in a tendon subject to compression

The structure, ultrastructure, histochemistry, and immunohistochemistry of the suprapatella have been described in the rat. The suprapatella is a fibrocartilaginous sesamoid within the tendon of quadriceps femoris that articulates with the femoral condyles during flexion of the knee joint and reduces the amount of bending required at the tendon-bone junction. The cells of the suprapatella were much larger and more numerous than those in the associated tendon and were packed with vimentin-containing, intermediate filaments. The tendon cells contained far fewer filaments. The cells of both regions contained actin and tubulin. Histochemical and immunohistochemical studies showed that the suprapatellar cells were embedded in a matrix that is rich in chondroitin sulphate, but does not contain keratan or heparan sulphate. The fibrocartilage of the adjacent attachment zone of the quadriceps tendon also contained chondroitin sulphate, but in addition was rich in type II collagen. The structure of the suprapatella was similar to that of the fibrocartilaginous regions of tendons that pass around bony pulleys. However, there were differences in matrix composition that could reflect functional differences between the fibrocartilages.     

Ultrastructural and immunohistochemical similarities of two distinct entities; multiple sclerosis and hereditary motor sensory neuropathy

In the present study, we present the ultrastructural and immunohistochemical properties of the sural nerves of two patients, one of whom was diagnosed as having multiple sclerosis with involvement of the peripheral nervous system (PNS), and the other as having hereditary motor sensory neuropathy type-I with involvement of the central nervous system (CNS). Expression of several extracellular matrix (ECM) proteins (fibronectin, laminin, and collagen type-IV), intermediate filaments (vimentin) and S-100 protein (marker for the axon-Schwann cell interface) was investigated by means of immunohistochemical methods. In addition, the tissue samples were evaluated ultrastructurally. Immunohistochemical staining revealed increased expression of the ECM molecules mentioned above in relation with the sural nerves of the patients. We hypothesize that this enhanced expression is due to Schwann cell-axon interactions. Vimentin expression was different in Schwann cells and S-100 immunostaining was decreased near the Schwann cell-axon interface. Myelin fragmentation, axon vacuolization, onion bulbs, tomoculous formation, axonal degeneration were found to occur. These results suggest that there is active ECM reorganization in the sural nerve of these patients, and some ultrastructural changes are similar in the damaged axonal organization and in Schwann cells although the changes are not completely the same in the two patients. In conclusion, our study demonstrates that there is an association between the demyelinization process in the CNS and the PNS even though they are affected by different mechanisms.     

Regional variations in human patellar trabecular architecture and the structure of the quadriceps enthesis: a cadaveric study

We investigated whether there were regional differences in the quadriceps enthesis and the patella bone structure that could suggest unequal force transmission to the patella. Quadriceps tendon enthesis was removed by cutting the patellae transversally in the middle and the quadriceps tendon approximately 1 cm from the bone. Tissues were post‐fixed, decalcified, dehydrated through and embedded in paraffin wax. Serial longitudinal sections were cut, mounted on glass slides at 1‐mm intervals and slides were stained. Trabecular architecture was analysed from digital images taken from the histological slides, and regional differences at the enthesis in the thickness of the uncalcified fibrocartilage and the cortical zone of calcified tissue (calcified cartilage and lamellar bone) were evaluated. At the quadriceps enthesis, the thickness of the cortical zone of calcified tissue was significantly greater in the central part of the enthesis than medially and laterally. The trabeculae were thicker in the central and lateral parts compared with the medial region. Similarly, the zone of uncalcified fibrocartilage was thicker laterally and centrally than medially. Bone structure and the thickness of uncalcified fibrocartilage presented a similarity between the centre and the lateral parts; however, the medial side was different. We suggest that the mechanical stress at the proximal quadriceps tendon enthesis is higher laterally and centrally compared with medially. This could induce a lateral patellar translation, which is potentially a risk factor for knee osteoarthritis.     

Cell and matrix biology of the suprapatella in the rat: a structural and immunocytochemical study of fibrocartilage in a tendon subject to compression.

The structure, ultrastructure, histochemistry, and immunohistochemistry of the suprapatella have been described in the rat. The suprapatella is a fibrocartilaginous sesamoid within the tendon of quadriceps femoris that articulates with the femoral condyles during flexion of the knee joint and reduces the amount of bending required at the tendon-bone junction. The cells of the suprapatella were much larger and more numerous than those in the associated tendon and were packed with vimentin-containing, intermediate filaments. The tendon cells contained far fewer filaments. The cells of both regions contained actin and tubulin. Histochemical and immunohistochemical studies showed that the suprapatellar cells were embedded in a matrix that is rich in chondroitin sulphate, but does not contain keratan or heparan sulphate. The fibrocartilage of the adjacent attachment zone of the quadriceps tendon also contained chondroitin sulphate, but in addition was rich in type II collagen. The structure of the suprapatella was similar to that of the fibrocartilaginous regions of tendons that pass around bony pulleys. However, there were differences in matrix composition that could reflect functional differences between the fibrocartilages.     

节段腱移植修复陈旧性中央腱损伤：关节屈曲及背伸功能评价

背景：手指指伸肌腱中央腱损伤常用的治疗方法有Matev法、carroll法、fowler法及残余中央腱条翻转修复等,但仍存在外观臃肿、肌腱粘连、关节功能受限严重等不良后果。 目的：观察中节指背纵列钻孔、节段腱移植修复陈旧性中央腱损伤的临床效果。 方法：收集陈旧性中央腱损伤患者80例,按照随机数字表法将患者腱移植治疗组和对照组,每组40例,腱移植治疗组给予中节指背纵列钻孔、游离掌长肌腱条自远位骨孔进入,近位骨孔穿出,缝合牢固固定行节段腱移植治疗;对照组根据病情决定,手术方法包括carroll法、Matev法、Fowler法,观察两组修复效果。 结果与结论：腱移植治疗组优良率为85%,对照组为65%(P < 0.05);VCWS测试腱移植治疗组对原工作适应例数为30例(75%),对照组16例(40%)(P < 0.05)。两组患者近指间关节屈曲度入院时、住院15 d、出院前1 d、随访4个月逐渐增大,近指间关节背伸受限度逐渐降低(P < 0.05);治疗后住院15 d、出院前1 d、随访4个月时近指间关节屈曲度与近指间关节背伸度在两组间差异有显著性意义(P < 0.05)。结果表明,中节指背纵列钻孔及节段腱移植修复陈旧性中央腱损伤,恢复关节屈曲和背伸功能较好。      

Exposure of a tendon extracellular matrix to synovial fluid triggers endogenous and engrafted cell death: A mechanism for failed healing of intrathecal tendon injuries

Aim: The purpose of this study was to investigate the effect of normal synovial fluid (SF) on exposed endogenous tendon-derived cells (TDCs) and engrafted mesenchymal stem cells (MSCs) within the tendon extracellular matrix. Methods: Explants from equine superficial digital flexor (extra-synovial) and deep digital flexor tendons (DDFTs) from the compressed, intra-synovial and the tensile, extra-synovial regions were cultured in allogeneic or autologous SF-media. Human hamstring explants were cultured in allogeneic SF. Explant viability was assessed by staining. Proliferation of equine monolayer MSCs and TDCs in SF-media and co-culture with DDFT explants was determined by alamarblue®. Non-viable Native Tendon matrices (NNTs) were re-populated with MSCs or TDCs and cultured in SF-media. Immunohistochemical staining of tendon sections for the apoptotic proteins caspase-3, ?8, and ?9 was performed. Results: Contact with autologous or allogeneic SF resulted in rapid death of resident tenocytes in equine and human tendon. SF did not affect the viability of equine epitenon cells, or of MSCs and TDCs in the monolayer or indirect explant co-culture. MSCs and TDCs, engrafted into NNTs, died when cultured in SF. Caspase-3, ?8, and ?9 expression was the greatest in SDFT explants exposed to allogeneic SF. Conclusions: The efficacy of cells administered intra-synovially for tendon lesion repair is likely to be limited, since once incorporated into the matrix, cells become vlnerable to the adverse effects of SF. These observations could account for the poor success rate of intra-synovial tendon healing following damage to the epitenon and contact with SF, common with most soft tissue intra-synovial pathologies.     

非手术与手术修复急性闭合性跟腱断裂的Meta分析

背景：关于非手术及手术修复急性跟腱断裂一直存在争议,相关研究多为回顾性分析,缺乏高等级循证医学证据。 目的：系统评价非手术与手术修复急性闭合性跟腱断裂临床疗效。 方法：计算机检索 PubMed、EMbase、The Cochrane Library(2014年第1期)、CBM、CNKI、Ovid及WanFang Data,手工检索相关杂志,检索时限均从建库或建刊至2014年2月,纳入非手术治疗与手术治疗急性闭合性跟腱断裂的随机对照试验,由2名研究人员独立提取文献数据及质量评价后,用RevMan 5.2软件进行系统评价。 结果与结论：最终纳入9篇随机对照文献,患者共874例,非手术组441例,手术组433例。Meta分析结果显示,与手术组相比较,非手术组总的并发症率更低[OR=0.41,95%CI(0.26,0.63),P < 0.000 1],但跟腱再断裂率高[OR=2.86,95%CI(1.62,5.02),P=0.000 2],瘢痕粘连=0.07,95%CI(0.03,0.19),P < 0.000 1]。而两者在患者满意度、浅表感染、恢复正常运动、深部感染等方面,差异均无显著性意义(P > 0.05)。非手术修复与手术修复急性闭合性跟腱断裂相比,可有效降低总的并发症及瘢痕粘连率,但跟腱再断裂率较高。受样本量及方法质量学的限制,以上结论需要更多大样本、多中心、高质量的随机对照试验验证。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程全文链接：     

Expression and accumulation of interstitial collagen in the neonatal rat heart

Significant physiological changes occur in the heart following birth including increased arterial blood pressure and heart rate. Concurrently, biochemical and structural alterations are evident in the neonatal heart in response to these dynamic physiological properties. Prominent among these is the elaborate development of the cardiac extracellular matrix, composed primarily of interstitial collagen. The collagenous fibers, together with other matrix components, form and elastic, stress-tolerant network which functions in the dissipation of force throughout the heart wall. The present studies have used biochemical and molecular techniques to show the temporal and spatial patterns of interstitial collagen accumulation expression during late fetal and neonatal development of the rat heart. The use of biochemical and particularly molecular methodologies allows the analysis of the expression of matrix components at a resolution previously not attained by structural studies alone. These data show relative increases in interstitial collagen immediately following birth as well as spatial differences in collagen mRNAs within the heart. The data presented provide further evidence for a role of mechanical stimulation in the regulation of collagen gene expression during this period of heart development. © 1993 Wiley-Liss, Inc.     

The cholinergic innervation of the rat cerebral cortex shows two distinct phases in development

Summary The cholinergic innervation of the rat cerebral cortex was examined in pre- and postnatal life using immunohistochemistry with a monoclonal antibody directed against choline acetyltransferase (ChAT). Our observations show that there are two separate phases in the development of the cholinergic innervation of the rat neocortex. The first, a transient phase, occurs in the late stages of gestation and in the perinatal period. During this time, ChAT-labelled cells (neuroblasts, as well as immature pyramidal and non-pyramidal neurons) are present throughout the entire rostro-caudal extent of the primordial cortex. The fate of these cells, which are not visible shortly after birth, is unknwon as is their functional role in the developing cortex. The second phase in the development of the cholinergic innervation begins in the middle of the second postnatal week. At this stage only a few faintly stained neurons and fibres appear in the cortex. Their numbers and staining intensity increase gradually until the fifth postnatal week when ChAT-labelled neurons and axonal arbours appear indistinguishable from their adult counterparts. The pattern of development observed in the second phase parallels closely that shown in a recent analysis of cortical ChAT activity during postnatal life.     

指浅屈肌腱止点的位置及其与A4滑车的关系

目的：观察和测定指浅屈肌腱止点的形态、位置及其与A4滑车的位置关系。方法：采用12只成人新鲜尸体手标本的48个手指,观察指浅选屈肌腱在中节指骨和近侧指间关节处的形态、位置,近止点的浅肌腱和腱纽的关系,观察止点和A4滑车的重迭关系和程序。结果：指浅屈肌腱在手指上止点由止于指骨、掌板和腱鞘的部分组成,浅肌腱近止点处为扁平腱束,有短腱纽完全附着,止点长度为0.6-1.0cm,距Camper腱交叉0.4-0.7cm,有79%的手指的止点与A4滑车部分重迭,21%手指止点完全在A4滑车以近。结论：指浅屈肌腱止点解剖结构复杂,与指骨、掌板、腱鞘、腱纽存在密切联系,在不同手指位于A4滑车以内和以近的位置,对指深屈肌腱的营养、力学功能及协同功能有重要作用。