The structure and locis minus resistentia of bone-tendon joints of the horse's finger flexors

Abstract

We studied the peculiarities of the structure and functions of bone tendon compounds (enthusis). The subject of the study is a horse. Subject of investigation – places of attachment of tendons of superficial finger flexor, deep finger flexor. Light microscopy, polarization microscopy and biomechanics were used. The general patterns of the structure of enthesis that belong to the fibrous cartilage and fibrous types are established. In the enthesis of the fibrous cartilage type there are zones of tendon, fibrous cartilage, mineralized fibrous cartilage, lamellar bone tissue. Areas of tendon, reticulofibrous bone tissue, lamellar bone tissue were identified in fibrous type enthesis. Biomechanical enthesis of different types are different. In fibrous cartilaginous entesis, the microhardness of tissues changes smoothly, in fibrous – more dramatically. It is shown that the fibrous-cartilaginous enthesis are adapted to dissipate the stresses that arise when the tendon is stretched. Fibrous-type enthesis tightly fix tendons on the bone. The revealed structural and functional features ensure the functional reliability of the entheses. But there are also places of least stability – stress concentration zones. These are the mineralization front, as well as the resorption cavities that occur during the remodeling of mineralized cartilage and subchondral bone. During overloads, they can be injured and lead to the occurrence of enthesopathies.