It is differentiated from the tendon, ligament or bone by the mineralization of the collagen fibers that fuse with the bone itself. This mineralization allows the enthesis to become part of the bone and to anchor the muscle or ligament to the bone.
This has traditionally been viewed as a focal abnormality, even though the inflammatory reaction intrinsic to enthesitis may be quite extensive. This highlights the fact that stress concentration at an insertion site involves not only the enthesis itself, but neighbouring tissues as well.
The archetypal enthesis organ is that of the Achilles tendon where intermittent contact between tendon and bone immediately proximal to the enthesis leads to the formation of fibrocartilages on the deep surface of the tendon and on the opposing calcaneal tuberosity, but similar functional modifications are widespread throughout the skeleton.
Many entheses have bursae and fat near the insertion site and both of these serve to promote frictionless movement. Collectively, the fibrocartilages, bursa, fat pad and the enthesis itself constitute the enthesis organ.
However, it also includes both the immediately adjacent trabecular bone networks and in some cases deep fascia. The SEC concept emphasizes the interdependence between synovial membrane and entheses within enthesis organs. It draws attention to the fact that one component the enthesis is prone to microdamage and the other the synovium to inflammation.
If an enthesis is damaged, any ensuing inflammatory reaction is likely to occur in the synovium.
Stress concentration at the enthesis itself is dissipated at many sites by fibrous connections between one tendon or ligament and another, close to the insertion site.
At a microscopic level, enthesis fibrocartilage is of paramount importance in ensuring that fibre bending of the tendon or ligament is not focused at the hard tissue interface.
Normal enthesis organs are avascular in their fibrocartilaginous regions, but tissue microdamage to entheses is common and appears to be associated with tissue repair responses and vessel ingrowth. This makes the enthesis organ a site where adjuvant molecules derived from bacteria may be preferentially deposited.
This microdamage and propensity for bacterial molecule deposition in the context of genetic factors such as HLA-B27 appears to lead to the characteristic inflammatory changes of AS.
Understanding the enthesis organ concept helps to explain synovitis and osteitis in spondy-loarthropathy. In this chapter, we review the extent and types of enthesis organs and show how a patho-anatomic appreciation of these structures leads to a new platform for understanding the pathogenesis of SpA.The effect of entheseal changes on size of the enthesis in young adults IV Jornadas Portuguesas de Paleopatologia 21st to 22nd November, Charlotte Henderson Coimbra CIAS – Research Centre for Anthropology and Health, University of Coimbra, Portugal [email protected] Introduction Results Entheses have been widely used to study activity-patterns in the past.
Fibrosis - within a microfocus of enthesis, lymphocytes, plasma cells and neutrophils are found Ossification- erosive lesions heal by forming new bone creating a new enthesis that protrudes What are spondyloarthropathies? Inflammation of the enthesis, known as enthesitis, is the foundation of the disease process of ankylosing spondylitis.
This inflammation causes bone to . Articular enthesis organs were found at 14 entheses, including the attachments of the digital extensor tendons and collateral ligaments, the cruciate ligaments, tibialis anterior, the lateral collateral ligament of the knee, and the popliteal tendon.
An enthesis is a point of attachment or insertion point of a sinew (tendon or ligament) to the bone. This image shows the foot and the Achilles enthesis or tendon insertion point in cartoon form.
The Achilles is the largest enthesis or insertion in the body but a multitude of such insertions hold the entire skeleton together and allow movement. RESULTS: On MRI, the dorsal capsular enthesis was the epicentre of an inflammatory reaction.
This extended to involve the soft tissues adjacent to the nail in 8 of 10 cases in PsA, but only 4 of 10 cases in OA where the inflammation is less intense and in none of the normal fingers.