BIOMECHANICS OF LIGAMENT AND TENDONS.pptx

what biomechanics is and why it's important in understanding ligaments and tendons. structure and composition of ligaments and tendons. the roles of ligaments and tendons in the body and how they contribute to movement and stability. mechanical properties of ligaments and tendons, including strength, elasticity, and viscoelasticity.

1. Biomechanics of tendon and ligament By : Jemini Parmar F.Y .MPT

2. The principal joint stabilizing connective tissues Tendon , Ligaments & joint capsules The passive structures Surround, connect & stabilize the joints of skeletal system Provide static stability to the joints

3. The principal joint stabilizing connective tissues Ligament & joint capsule Connect bone to bone The static restraints Augment the mechanical stability of the joints Guide joint motion Prevent excessive motion Provide joint sense to nervous system

4. The principal joint stabilizing connective tissues Tendons Attach muscle to bone The dynamic restrains & protect from instability Transmit tensile loads from muscle to bone The muscle tendon unit …..active structure

5. Structural composition of tendons Dense connective tissues(parallel-fibered collagenous tissues) Provide strength & flexibility Consist of relatively few fibroblast (tenocytes) & extracellular matrix Cellular material – Approx 20% of the total tissue volume Extracellular matrix - Approx 80%

6. Tendons …. Tendons cells(tenocytes) Specialized fibroblast within the tendon substance Function of tenocytes Control tendon metabolism Mechanotransduction ….collagen synthesis Tenocytes lie in longitudinal rows along fibrils Have multiple extensions in ECM , allowing for three dimensional communication via gap junctions

7. Tendons …. The extracellular matrix(ECM)…….. Water – Approx. 55 to 70% of the matrix Solids – 30 to 45% (collagen 60 to 85%, inorganic substance <0.2%, a small amount of elastin 2% & other proteins 4.5%) Maintain tendon structure Facilitate biomechanical response to mechanical loading

8. Tendons …. The collagen content…. 60% type 1 fibres Type 3, 4, 5 & 6 also present Type 1 sustains large tensile loads Some level of mechanical deformation

9. Collagen synthesis Process starts in tenocytes Integrins .. sense tensile strain & transform into adoptive responses of cells called mechanotransduction Growth factors TGF- β , IGF, IGF-BP, FGB et. IL & PGs are also involved MAPK(mitogen-activated protein kinase pathway)

10. Collagen synthesis Fibroblast procollagen extracellular collagen Type 1 collagen molecule…. The most common collagen molecule Consist of 3 polypeptide chains (α chains) in a triple helix ….Rod shaped Length – Approx 280nm Diameter - Approx 1.5nm

11. Intra- & interchain bonding is essential for the stability of the molecule Cross -linking between collagen molecules…. Essential for the strength of the tissues they compose Allows these tissues to function under mechanical stress “head-to-tail” inter-actions

12. Intra- & interchain bonding is essential for the stability of the molecule Cross-linking in immature collagen…. Relatively few & reducible Soluble in neutral salt & in acid solutions Cross -linking in mature collagen…. Stable and nonreducible cross-links by glycation Not soluble in neutral salt or in acid solutions

13. Schematic representation of the microarchitecture of a tendon.

14. Collagen …. The arrangement of the collagen fibers differs somewhat in the tendons and ligaments and is suited to the function of each structure . Arrangement of collagen fibers in tendons…. Parallel arrangement To bear high unidirectional tensile load during activity

15. Elastin Proportion of elastin mechanical properties of tendons & ligaments Protein elastin in tendons & extremity ligaments are very less 2%. In elastic ligaments ( lig.flavum )….relatively high 2 to 1 ratio of elastic to collagen fibers in ligamentum flavum

16. Ground substance Ground substance in ligaments & tendons…. Composed of inorganic substances , 0.2% & other proteins 4.5% Inorganic substances…. Proteoglycans (PGs)most dominant protein Only a small number of PGs exist in tendons PGs make the matrix a gel-like material PGs act as a cement like substance between the collagen microfibrils to stabilize the collagenous skeleton and contribute to the overall strngth

17. Composition and structure of ligaments Ligaments have same general composition as tendon with few key differences In contrast to tendons Closely interlaced with one another Sustain multidirectional tensile loads

18. Vascularity Limited vascularity Blood vessels in tendons accounts for 1-2%(white appearance) Other factors such as location , morphology , prior injury & level of physical activity also contribute Tendons receive their blood supply directly from vessels in the perimysium , the periosteal insertion , and the surrounding tissue Vascular tendons…. Tendons surrounded by sparatenon Avascular tendons…. Tendons surrounded by a sheath

19. Neural components of tendon & ligament Have specialized nerve ending and mechanoreceptors Provide proprioception and nociceptors

20. Outer structure of Tendons vs Ligaments The paratenon/ epiligament …. the outer loose areolar connective tissues Paratenon prtects the tendon and enhance its gliding The epitenon …. a synovial like membrane just beneath the paratenon in tendons subjected to high friction forces Facilitates gliding of the tendon The endotenon…. bind each fiber bundle together , which continues at the Musculo-tendinous junction into the perimysium

21. Insertion into bone The tendo-osseous junction…. Similar in ligaments and tendons Consists of four zones Zone-1 : parallel collagen fibers Zone-2 : unmineralized fibrocartilage Zone-3 : mineralized fibrocartilage Zone-4 : cortical zone

22. Biomechanical Properties of Tendons and Ligament Viscoelasticity Tendons and ligaments are viscoelastic structures Tendons are strong enough to sustain the high tensile forces The ligaments are pliant and flexible, allowing natural movement of the bones to which they attach, but are strong and inextensible so as to offer suitable resistance to applied forces.

23. load-elongation curve A load-elongation curve offers information regarding the tensile capacity of a tendon-ligament structure after loading a tendon or a ligament to failu The ultimate load (N) is the highest load placed on the structure before failure. The ultimate elongation (mm) is the maximum elongation of the complex at failure.

24. The uploaded collagen fibers have a wavy configuration. The collagen fibers straightened out under load.

25. load-elongation curve of ligaments with high level of elastin

26. Hysteresis During the loading and unloading of a ligament between two limits of elongation , the elastic fibers allow to its original shape and size after being deformed. Meanwhile part of this energy spent is stored. And this cycle is called as hystresis . The area enclose by the loop represents the energy loss.

27. Viscoelastic behavior in tendons and ligaments to tensile loads Both ligaments and tendons display this viscoelastic behavior that is assumed to result from the complex interaction of its constituents (i.e., collagen, water, surrounding protein, and ground substance) 1. Load relaxation 2. The creep response

28. Tendon injuries

29. Ligament injuries

30. Healing of tendons and ligaments Three phases occurring in succession: The inflammatory phase The proliferative phase or fibroplasia Remodeling and maturation phase There is also variation in the ability of tendons and ligaments to heal.

31. Factors That Affect the Biomechanical Properties of Tendons and Ligaments Maturation and aging Pregnancy and the postpartum period Mobilization and immobilization COMORBIDITIES : diabetes mellitus, connective tissue disorders PHARMACOLOGIC AGENTS : steroids , nonsteroidal anti-inflammatory drugs ( nsaids ) ,

32. Thank you