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.     

指深屈肌腱及指伸肌腱止点的解剖研究

目的　通过解剖研究指深屈肌腱及指伸肌腱在远节指骨基底掌侧和背侧止点平面的差别，为西摩骨折发生机制提供解剖学依据。 方法　手部残肢10具，其中左手3例，右手7例，均为男性患者，年龄24~58岁。2~5指分别有10指，全部手指无外伤手术史、无畸形。自远节指间关节水平掌侧及背侧分别切开，于末节指骨水平分离各指的指深屈肌腱及指伸肌腱，记录其与末节指骨掌侧及背侧关节面的距离，比较指深屈肌腱及指伸肌腱在末节指骨掌、背侧的止点水平。 结果　指深屈肌腱止点近端至关节面距离：示指（2.19±0.27）mm，中指（2.50±0.14）mm，环指（2.23±0.16）mm，小指（1.83±0.19）mm；指伸肌腱止点近端至关节面距离：示指（0.12±0.02）mm，中指（0.18±0.02）mm，环指（0.12±0.05）mm，小指（0.06±0.01）mm；各指差异有统计学意义（P＜0.05）。指深屈肌腱止点中点至关节面距离：示指（3.73±0.45）mm，中指（4.33±0.45）mm，环指（3.53±0.46）mm，小指（3.16±0.41）mm；指伸肌腱止点中点至关节面距离：示指（1.77±0.06）mm，中指（1.76±0.20）mm，环指（1.77±0.06）mm，小指（1.47±0.10）mm；各指差异有统计学意义（P＜0.05）。 结论　指伸肌腱在末节指骨基底的止点较指深屈肌腱的止点距关节面更近，为西摩骨折的发生机制提供了解剖依据。     

指深屈肌腱及指伸肌腱止点的解剖研究

目的　通过解剖研究指深屈肌腱及指伸肌腱在远节指骨基底掌侧和背侧止点平面的差别,为西摩骨折发生机制提供解剖学依据。 方法　手部残肢10具,其中左手3例,右手7例,均为男性患者,年龄24~58岁。2~5指分别有10指,全部手指无外伤手术史、无畸形。自远节指间关节水平掌侧及背侧分别切开,于末节指骨水平分离各指的指深屈肌腱及指伸肌腱,记录其与末节指骨掌侧及背侧关节面的距离,比较指深屈肌腱及指伸肌腱在末节指骨掌、背侧的止点水平。 结果　指深屈肌腱止点近端至关节面距离：示指（2.19±0.27）mm,中指（2.50±0.14）mm,环指（2.23±0.16）mm,小指（1.83±0.19）mm;指伸肌腱止点近端至关节面距离：示指（0.12±0.02）mm,中指（0.18±0.02）mm,环指（0.12±0.05）mm,小指（0.06±0.01）mm;各指差异有统计学意义（P＜0.05）。指深屈肌腱止点中点至关节面距离：示指（3.73±0.45）mm,中指（4.33±0.45）mm,环指（3.53±0.46）mm,小指（3.16±0.41）mm;指伸肌腱止点中点至关节面距离：示指（1.77±0.06）mm,中指（1.76±0.20）mm,环指（1.77±0.06）mm,小指（1.47±0.10）mm;各指差异有统计学意义（P＜0.05）。 结论　指伸肌腱在末节指骨基底的止点较指深屈肌腱的止点距关节面更近,为西摩骨折的发生机制提供了解剖依据。     

Tissue-engineering strategies for the tendon/ligament-to-bone insertion

Injuries to connective tissues are painful and disabling and result in costly medical expenses. These injuries often require reattachment of an unmineralized connective tissue to bone. The uninjured tendon/ligament-to-bone insertion (enthesis) is a functionally graded material that exhibits a gradual transition from soft tissue (i.e., tendon or ligament) to hard tissue (i.e., mineralized bone) through a fibrocartilaginous transition region. This transition is believed to facilitate force transmission between the two dissimilar tissues by ameliorating potentially damaging interfacial stress concentrations. The transition region is impaired or lost upon tendon/ligament injury and is not regenerated following surgical repair or natural healing, exposing the tissue to risk of reinjury. The need to regenerate a robust tendon-to-bone insertion has led a number of tissue engineering repair strategies. This review treats the tendon-to-bone insertion site as a tissue structure whose primary role is mechanical and discusses current and emerging strategies for engineering the tendon/ligament-to-bone insertion in this context. The focus lies on strategies for producing mechanical structures that can guide and subsequently sustain a graded tissue structure and the associated cell populations.     

Three-dimensional reconstructions of the Achilles tendon insertion in man

The distribution of type II collagen in sagittal sections of the Achilles tendon has been used to reconstruct the three‐dimensional (3D) shape and position of three fibrocartilages (sesamoid, periosteal and enthesis) associated with its insertion. The results showed that there is a close correspondence between the shape and position of the sesamoid and periosteal fibrocartilages – probably because of their functional interdependence. The former protects the tendon from compression during dorsiflexion of the foot, and the latter protects the superior tuberosity of the calcaneus. When the zone of calcified enthesis fibrocartilage and the subchondral bone are mapped in 3D, the reconstructions show that there is a complex pattern of interlocking between pieces of calcified fibrocartilage and bone at the insertion site. We suggest that this is of fundamental importance in anchoring the tendon to the bone, because the manner in which a tendon insertion develops makes it unlikely that many collagen fibres pass across the tissue boundary from tendon to bone. When force is transmitted to the bone from a loaded tendon, it is directed towards the plantar fascia by a series of highly orientated trabeculae that are clearly visible in 3D in thick resin sections.     

富血小板血浆与脱蛋白骨复合物能增强早期腱-骨界面的愈合

背景：单独使用富血小板血浆凝胶已被证实并不能提高骨再生能力,且容易在关节液破坏下迅速流失或失活。 目的：观察富血小板血浆与脱蛋白骨复合物对前交叉韧带重建后早期腱-骨界面的生物力学性能的影响。 方法：将新西兰大白兔分为正常组、模型组、实验组和对照组,后3组建立自体肌腱重建膝前交叉韧带模型,模型组骨隧道中不植入任何材料,对照组和实验组分别植入脱蛋白骨与富血小板血浆+脱蛋白骨复合物。 结果与结论：治疗后2,4周时,各组拉力卸载方式主要是移植肌腱从骨隧道中拔出;8周时,实验组以肌腱体部撕裂为主,对照组与模型组大部分仍从骨隧道拔出,差异有显著性意义(P < 0.05);12周时,各组多数见肌腱体部撕裂。治疗后4,8周时,实验组最大抗拉载荷明显高于对照组及模型组(P < 0.05);12周时,各组最大抗拉载荷差异无显著性意义(P > 0.05);12周时,实验组最大抗拉载荷仍明显小于正常组(P < 0.01)。各组刚度随时间变化呈逐渐增大的趋势,但组间比较差异无显著性意义(P > 0.05)。 说明富血小板血浆与脱蛋白骨复合物能够增加早期腱-骨界面的力学强度。     

颅脑损伤促进的坐骨神经再生

BACKGROUND:Studies have shown that craniocerebral injury can promote the repair of sciatic nerve injury in rats, but its precise mechanism remains unclear. OBJECTIVE:To further explore the action mechanism of craniocerebral injury on the repair of sciatic nerve injury using morphology and histology. METHODS:Sixty specific-pathogen-free healthy male Sprague-Dawley rats were randomly divided into two groups. Rats with craniocerebral injury and sciatic nerve injury were considered as the experimental group. Rats with simple sciatic nerve injury were considered as the control group. Classical Feeney method was used in models of craniocerebral injury and SunderlandV sciatic nerve injury. At 8 and 12 weeks after modeling, sciatic nerve index was detected. Masson staining and NF200 immunofluorescence staining were used to observe the nerve regeneration at the anstomotic site. Transmission electron microscope was used to observe the number of regenerative axons. RESULTS AND CONCLUSION:At 8 and 12 weeks after modeling, compared with the control group, gait and sciatic nerve index recovered better in the experimental group. In the experimental group, Masson staining showed fewer nerve membrane collagen fibers, and the axon arranged neatly. NF200 immunohistochemistry showed that in the experimental group, the density of regenerated nerves was high, and nerves were regularly distributed. Transmission electron microscopy showed that in the experimental group, regenerative axons were regularly arranged, collagen scar was less, and myelin layer arranged regularly. Results suggested that the craniocerebral injury in rats may promote the repair of peripheral nerve injury by reducing scar collagen in nerve endings.     

Stem-cell-capturing collagen scaffold promotes cardiac tissue regeneration

Stem cell based therapy is coming of age. Besides stem cell transplantation, it has been a goal to use native autologous stem cells for tissue regeneration. However, the recruitment of native autologous stem cells at the targeting site has not been sufficient which limits the clinical application of autologous stem cells. Biomaterials have been increasingly used in tissue repair. They not only serve as scaffolds for cell proliferation, differentiation, and also provide guidance for 3-D reestablishment. In this study, we have attempted to enrich autologous stem cells at the wound site through a stem-cell-capturing collagen scaffold by conjugating with a stem cell specific antibody. Sca-1 is a common surface marker of hematopoietic, cardiac and skeletal muscle stem cells. Due to the interaction of antibody and antigen, Sca-1 positive cells could be enriched to the functional collagen scaffold both in vitro and in vivo. When the functional collagen scaffold is transplanted into C57/BL6 mouse as a patch to repair a surgical heart defect, the regeneration of cardiomyocytes has been observed. Thus, the collagen scaffolds covalently conjugated with stem cell specific antibody could be an effective approach to promote tissue regeneration.     

Synthetic collagen fascicles for the regeneration of tendon tissue

The structure of an ideal scaffold for tendon regeneration must be designed to provide a mechanical, structural and chemotactic microenvironment for native cellular activity to synthesize functional (i.e. load bearing) tissue. Collagen fibre scaffolds for this application have shown some promise to date, although the microstructural control required to mimic the native tendon environment has yet to be achieved allowing for minimal control of critical in vivo properties such as degradation rate and mass transport. In this report we describe the fabrication of a novel multi-fibre collagen fascicle structure, based on type-I collagen with failure stress of 25-49MPa, approximating the strength and structure of native tendon tissue. We demonstrate a microscopic fabrication process based on the automated assembly of type-I collagen fibres with the ability to produce a controllable fascicle-like, structural motif allowing variable numbers of fibres per fascicle. We have confirmed that the resulting post-fabrication type-I collagen structure retains the essential phase behaviour, alignment and spectral characteristics of aligned native type-I collagen. We have also shown that both ovine tendon fibroblasts and human white blood cells in whole blood readily infiltrate the matrix on a macroscopic scale and that these cells adhere to the fibre surface after seven days in culture. The study has indicated that the synthetic collagen fascicle system may be a suitable biomaterial scaffold to provide a rationally designed implantable matrix material to mediate tendon repair and regeneration.     

Ultrasonography gives directly but noninvasively elastic characteristic of human tendon in vivo

To obtain an insight into tendon elasticity during human movement, a real-time ultrasonography was applied to the contracting tibialis anterior muscle. The insertion point of fascicles onto the aponeurosis was clearly visualized, and its position relative to a fixed marker on the skin moved proximally (1) according to the increasing dorsiflexion force (F) with a fixed ankle joint. Notably, the 1 – F relationship in the tendon was found to be quadratic in nature (F = c1²; c=1.48 2.24, r=0.985 0.992, n=9) as has been reported in the isolated tendon, although the F – 1 curves were slightly underestimated in comparison with the stiffness constant estimated from tendon architecture. This underestimation might be caused by changes in the height of the foot arch with the application of force.     

指伸肌腱止点形态特点与损伤分型及治疗方法

目的　根据指伸肌腱止点的形态特点探讨其损伤分型与手术修复方法。 方法　依据将28例指伸肌腱止点区损伤情况分为带较大骨折块手指伸肌腱止点损伤、撕脱骨片小或骨折块粉碎无法固定及不带骨片的伸肌腱止点撕脱伤、靠近末节指骨基底背侧指伸肌腱腱性损伤3种类型。按损伤分型分别采骨块固定,末节指骨基底钻孔缝合固定及直接缝合修补等手术方法进行修复。 结果　28例无一例再度撕脱或断裂,其中3例远侧指间关节僵硬,其余25例远侧指间关节主动伸直受限度0°~10°,主动屈曲度30°~70°。 结论　根据伸肌腱止点损伤的分型,分别采用骨折块固定,末节指骨基底钻孔缝合固定及直接修补缝合手术方法进行修复,方法简便,疗效可靠。     

The long head of the biceps tendon is a suitable cell source for tendon tissue regeneration

Introduction

Tendon tissue engineering (TTE) tries to produce tendinous tissue of high quality to replace dysfunctional tissue. One possible application of TTE might be the replacement of ruptured tissue of the rotator cuff. Autologous tenocytes seem to be most suitable as no differentiation in vitro is necessary. Today it is still uncertain if there is a difference between tendon-derived cells (TDC) of different native tissues. Moreover, the search for suitable scaffolds is another important issue in TTE.

Material and methods

This study compared TDC of the long head of the biceps tendon (LHB), the anterior cruciate ligament (ACL) and the tendon of the musculus semitendinosus (TMS). The TDC were isolated using the cell migration method. Cell morphology was assessed using light microscopy and gene expression was performed using polymerase chain reaction (PCR). Afterwards, cell seeding efficiency and proliferation were tested on a collagen I scaffold using the WST-1 assay. Results were confirmed using H + E staining.

Results

The TDC of the LHB showed higher expression levels of collagen type I and decorin (p < 0.01) compared to TDC of other origin. Results showed efficient cell seeding and proliferation within the scaffold. Proliferation within the scaffold was not as high as when cells were cultivated without a scaffold.

Conclusions

The TDC of the LHB seems to be the most suitable cell source. Further research is necessary to find out if the results can be transferred to an in vivo model. The new collagen I scaffold seems to offer an opportunity to combine good biocompatibility and mechanical strength.     

Structure of the Achilles tendon at the insertion on the calcaneal tuberosity

Findings on the twisting structure and insertional location of the AT on the calcaneal tuberosity are inconsistent. Therefore, to obtain a better understanding of the mechanisms underlying insertional Achilles tendinopathy, clarification of the anatomy of the twisting structure and location of the AT insertion onto the calcaneal tuberosity is important. The purpose of this study was to reveal the twisted structure of the AT and the location of its insertion onto the calcaneal tuberosity using Japanese cadavers. The study was conducted using 132 legs from 74 cadavers (mean age at death, 78.3 ± 11.1 years; 87 sides from men, 45 from women). Only soleus (Sol) attached to the deep layer of the calcaneal tuberosity was classified as least twist (Type I), both the lateral head of the gastrocnemius (LG) and Sol attached to the deep layer of the calcaneal tuberosity were classified as moderate twist (Type II), and only LG attached to the deep layer of the calcaneal tuberosity was classified as extreme twist (Type III). The Achilles tendon insertion onto the calcaneal tuberosity was classified as a superior, middle or inferior facet. Twist structure was Type I (least) in 31 legs (24%), Type II (moderate) in 87 legs (67%), and Type III (extreme) in 12 legs (9%). A comparison between males and females revealed that among men, 20 legs (24%) were Type I, 57 legs (67%) Type II, and eight legs (9%) Type III. Among women, 11 legs (24%) were Type I, 30 legs (67%) Type II, and four legs (9%) Type III. No significant differences were apparent between sexes. The fascicles of the Achilles tendon attach mainly in the middle facet. Anterior fibers of the Achilles tendon, where insertional Achilles tendinopathy is most likely, are Sol in Type I, LG and Sol in Type II, and LG only in Type III. This suggests the possibility that a different strain is produced in the anterior fibers of the Achilles tendon (calcaneal side) where insertional Achilles tendinopathy is most likely to occur in each type. We look forward to elucidating the mechanisms generating insertional Achilles tendinopathy in future biomedical studies based on the present results.