Stefan Milz See discussions, stats, and author profiles for this publication at: Bronek Boszczyk letting you access and read them immediately.
Abstract The attachment between tendon and bone occurs across a complex transitional tissue that minimizes stress concentrations and allows for load transfer between muscles and skeleton.
This unique tissue cannot be reconstructed following injury, leading to high incidence of recurrent failure and stressing the need for new clinical approaches.
The attachment of a tendon/ligament to the skeleton is clearly the basic function of any enthesis and central to force transmission. Thus, tendons and ligaments often flare out at their attachment sites as an adaptation to securing skeletal anchorage and resisting the effects of insertional angle change. Tendon entheses can be classed as fibrous or fibrocartilaginous according to the tissue present at the skeletal attachment site. The former can be 'bony' or 'periosteal', depending on whether the tendon is directly attached to bone or indirectly to it via the periosteum. Tendon entheses can be classed as fibrous or fibrocartilaginous according to the tissue present at the skeletal attachment site. The former can be 'bony' or 'periosteal', depending on whether the tendon is directly attached to bone or indirectly to it via the periosteum.
This review describes the current understanding of the development and function of the attachment site between tendon and bone. The embryonic attachment unit, namely, the tip of the tendon and the bone eminence into which it is inserted, was recently shown to develop modularly from a unique population of Sox9- and Scx-positive cells, which are distinct from tendon fibroblasts and chondrocytes.
The fate and differentiation of these cells is regulated by transforming growth factor beta and bone morphogenetic protein signaling, respectively. Muscle loads are then necessary for the tissue to mature and mineralize. A number of fundamental questions regarding the development of this remarkable attachment system require further study.
These relate to the signaling mechanism that facilitates the formation of an interface with a gradient of cellular and extracellular phenotypes, as well as to the interactions between tendon and bone at the point of attachment.
This is achieved in the musculoskeletal system across a complex attachment system that includes the myotendinous junction and the tendon—bone junction, connected in series.
Although the myotendinous junction is rarely injured, tendon must often be repaired to bone to treat tendon injuries. Unfortunately, the specialized tissue that forms at the attachment of tendon to bone during fetal development and postnatal maturation is not regenerated during tendon-to-bone healing Rodeo et al.
Two examples of tendon—bone junctions prone to injury are the rotator cuff in the shoulder and the anterior cruciate ligament in the knee. Surgical repair of these tissues is particularly difficult because the surgeon must overcome the challenge of attaching two materials tendon and bone with vastly different mechanical properties.
A better understanding of the cellular and molecular mechanisms that drive development of the attachment tissue may allow researchers to develop therapeutic interventions for enhanced tendon-to-bone healing.
The formation of an attachment between a bone and a tendon starts during embryonic development.
Throughout musculoskeletal system assembly, the tendon—bone attachment unit forms a complex structure, which includes the distal end of the tendon, the transitional zone across which tendon inserts into bone, and the mineralized side of the attachment. Tendons often insert into bone eminences, projections that grow on bone surfaces, and exhibit a large variety of shapes and sizes Gray and Lewis, ; Hill, Bone eminences are termed according to their form: These superstructures provide a stable anchoring point for tendons, increase the moment arm for more effective muscle force transfer, and dissipate stresses at the tendon—bone interface.
This results in a more effective muscle attachment and facilitates movement Biewener et al. The structure of the attachment tissue is mechanically complex. Stress must be transferred between two materials that differ in material stiffness by two orders of magnitude.
Bone is a stiff, brittle material relative to tendon, with a material stiffness of approximately 20 GPa Bostrom et al. In contrast, tendon is tough and extensible when compared with bone, with a material stiffness of approximately MPa in tension Woo et al.
The attachment of two dissimilar materials results in stress singularities at their interface and a subsequent increased risk of failure. To overcome this inherent challenge, the tendon—bone attachment consists of transitional tissue with structural and compositional gradients that give rise to graded tissue mechanical properties and reduced stress concentrations Genin et al.Most tendons and ligaments have fibrocartilaginous entheses where there are 4 zones of tissue at their bony attachments--dense fibrous connective tissue, uncalcified fibrocartilage, calcified.
A periosteal fibrous enthesis can become a bony one with age, as the periosteum disappears from the attachment site with skeletal maturity (Matyas et al., ). The Skeletal Attachment of Tendons – Tendon ‘entheses.
Disorders at entheses (enthesopathies) are common and occur in conditions such as diffuse idiopathic skeletal hyperostosis and the seronegative spondyloarthropathies. They are also commonly seen as sporting injuries .
Jumper’s knee affects the attachment of there is skeletal unloading—e.g. prolonged bedrest, the patellar tendon to the lower pole of the patella. paralysis, cast immobilisation of a limb, or other It is common in sports such as volleyball and local methods of stress shielding.
Nov 17, · The enthesis is defined as the area where tendon, ligament, or joint capsule inserts into bone and acts to transmit tensile load from soft tissues to bone2.
En-theses are critical as they allow for the proper transmission of contractile forces from the muscle belly to the respective skeletal attachment, while simultaneously dissipating force away from the enthesis itself, from tendon into bone 1, 8, 9.
The skeletal attachment of tendons—tendon ‘entheses’ The skeletal attachment of tendons—tendon ‘entheses’ Benjamin, M; Kumai, T; Milz, S; Boszczyk, B.M; Boszczyk, A.A; Ralphs, J.R Tendon entheses can be classed as fibrous or fibrocartilaginous according to the tissue present at the skeletal attachment site.
The former can be ‘bony’ or ‘periosteal’, depending on whether the .