Ligaments & Tendons
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Roles in the Body (and fibrocartilage) Joint Capsule http://adam.about.com/encyclopedia/19089.htm Description Soft connective tissue composed of densely packed collagen fibers White Relatively inelastic Mechanical properties vary with shape and structural organization Simon, SR. Orthopaedic Basic Science. Science. Ohio: American Academy of Orthopaedic Surgeons; 1994. Structure Connective tissues are characterized by sparse cellularity distributed within an extracellular matrix Cells in tendons and ligaments are called fibroblasts Comparison Ligaments Tendons % of collagen Lower Higher % of ground substance Higher Lower Organization More random Organized Orientation Weaving pattern Long axis direction Simon, SR. Orthopaedic Basic Science. Science. Ohio: American Academy of Orthopaedic Surgeons; 1994. Composition COMPONENT LIGAMENT TENDON Cellular Materials: Fibroblasts 20% 20% Water 60-80% 60-80% Solids 20-40% 20-40% Collagen 70-80% Slightly higher Type I 90% 95-99% Type III 10% 1-5% 20-30% Slightly lesser Up to 2X collagen Scarce Extracellular: Ground substance Elastin Strength Ligament Tendon Tensile Strength Less than Tendon; Varies 50 to 150 MPa Elastic Modulus Meniscofemoral (355 ± 234 MPa Anterolateral bundle of PCL (294 ± 115MPa) Posterior bundle of PCL (150 ± 69MPa) 1,200 – 1,800 MPa *Wide ranges of mechanical properties are largely due to location and age http://ttb.eng.wayne.edu/~grimm/BME5370/Lect5Out.html http://dahweb.engr.ucdavis.edu/dahweb/126site/chp5.pdf Biomechanical Behavior Measured material property values vary due to: Location Varying degrees of crimp Use: Mobilization/Immobilization Aging Pregnancy Diabetes NSAID use Hemodialysis Viscoelastic Responses Tissue response to load dependent on: Affected by movement of water Magnitude of load Duration of load Prior loading Resistance to compressive force due to water trapped in proteoglycans Contributes to sustained or cyclic responses to stress Types of Response Creep Stress-Relaxation Hysteresis http://www.tendinosis.org/injury.html Creep Time dependent elongation of a tissue when subjected to a constant stress Example: Tendons: in an isometric contraction, the tendon will lengthen slightly and more muscle fibers will be recruited in order to maintain the position of the limb Ligaments: joints will loosen with time, decreasing the possibility of injury http://ttb.eng.wayne.edu/~grimm/ME518/L5A3.html http://www.orthoteers.co.uk/Nrujp~ij33lm/Orthconntiss.htm Stress-Relaxation Time dependent decrease in applied stress required to maintain a constant elongation Example: Tendons: in an isotonic contraction, the stress will decrease with time Ligaments: joints will loosen with time, decreasing the possibility of injury http://ttb.eng.wayne.edu/~grimm/ME518/L5A3.html http://www.orthoteers.co.uk/Nrujp~ij33lm/Orthconntiss.htm Hysteresis Energy lost within the tissue between loading and unloading Response of tissue becomes more repeatable Subsequent use of same force results in greater deformation Ligaments silver.neep.wisc.edu/ ~lakes/linksLec3.html Anterior Cruciate Ligament Lateral Collateral Ligament Posterior Cruciate Ligament Medial Collateral Ligament Anterior View of Knee Posterior View of Knee Posterior cruciate ligament Anterior cruciate ligament Click for more detail Medial meniscus Lateral meniscus www.ma.psu.edu/~pt/renee384/anatomy.htm Posterior View: Right knee in extension Superior View of Knee Posterior cruciate ligament Medial meniscus Lateral meniscus Anterior cruciate ligament Structure No molecular bonds between fascicles Free to slide relative to each other Orientations: Branching & Interwoven Parallel Spirally wound: Ex ACL Direct connection between bones: Ex Collateral Ligaments Smaller diameter fibers than in tendons http://dahweb.engr.ucdavis.edu/dahweb/126site/chp4.pdf http://silver.neep.wisc.edu/~lakes/BME601Fr.html Simon, SR. Orthopaedic Basic Science. Science. Ohio: American Academy of Orthopaedic Surgeons; 1994. Crimping Orientation of collagen in ligaments Allows elongation of fibers before tensile stresses are experienced Functions Transmit load from bone to bone Hold the skeleton together Provide stability at joints Flexible but plastic Maintain joint congruency Limit freedom of movement Prevent excessive motion by being a static restraint Occasionally act as a positional bend/strain sensor Mediate motions between opposing fibrocartilage surfaces Degrees of Freedom Potentially 6 degrees of freedom in all joints ¾ 3-plane rotation o o o ¾ Flexion-extension Abduction-adduction Internal-external 3 -plane translation o o o Medial-lateral Compression-distraction Anterior-posterior Primary Restraint* Knee Flex @Knee flexion Maximal Stretch of (°) Anterior Cruciate anterior tibial translation 30 - 45 Posterior Cruciate anterior tibial translation 90 Medial Collateral Valgus forces internal tibia rotation Lateral Collateral varus forces *No peer-reviewed documentation to support this information 0 10-60 0 Mechanical Behavior Human cadaveric ACL in knee joint 3a Tensile Response Curve Region 1 “Toe” Crimp: low stiffness; change in slope as collegen fibers straighten; ligaments become more stiff as more fibers are recruited Region 2 Linear Region: slope = stiffness/Elastic Modulus Elastic: higher stiffness Region 3 Less linear behavior; deformation is permanent (tearing, stretch); Area of Microfailure; Ultimate Load: where failure occurs (N) Region 3a Energy absorbed to failure: area under the curve (Nmm) Region 4 Ligament ruptures Region 5 Ligament may appear intact; Fibers to slide under low loads Stress Vs. Strain More relevant method of expressing Force vs. Deformation behavior Region descriptions same as Force vs. Deformation curve Stress (N/mm2) = load per cross-sectional area of sample Strain = percentage change in length Injuries Occur most frequently during athletic activities Knee injuries ACL PCL Partial or complete tear of ligament caused by quick changes in direction, slowing down while running, landing a jump, direct contact Symptoms include delayed pain and swelling Sprain of ligament due to overstretching, impact to the front of the knee, misstep MCL Diagnosis Press gently at knee cap to feel for fluid at the joint X-ray MRI http://orthoinfo.aaos.org/fact/thr_report.cfm?Thread_ID =157&topcategory=Knee http://orthoinfo.aaos.org/fact/thr_report.cfm?Thread_ID=157&topcategory=Knee http://hcd2.bupa.co.uk/fact_sheets/mosby_factsheets/Knee_ligament_injuries.html http://hcd2.bupa.co.uk/fact_sheets/mosby_factsheets/Knee_ligament_injuries.html Healing RICE Physical therapy Rest, Ice, Compression, Elevation Strengthening exercises Range of motion tests Braces Crutches Surgery http://orthoinfo.aaos.org/fact/thr_report.cfm?Thread_ID =157&topcategory=Knee http://orthoinfo.aaos.org/fact/thr_report.cfm?Thread_ID=157&topcategory=Knee http://hcd2.bupa.co.uk/fact_sheets/mosby_factsheets/Knee_ligament_injuries.html http://hcd2.bupa.co.uk/fact_sheets/mosby_factsheets/Knee_ligament_injuries.html http://12.31.13.115/hwdb/images/hwstd/medical/orthoped/n5550876.jpg Structure Long cylindrical structures Tightly packed longitudinally running collagen fibers Nuclei and sparse cytoplasm of fibrocytes compressed almost flat between them Relatively avascular Slow to heal from trauma injuries http://adam.about.com/encyclopedia/19089.htm Attachment Each muscle has two tendons: Proximal: Myotendinous Junction (MTJ) ¾ The point of union with a muscle: origin Distal: Osteotendinous Junction (OTJ) ¾ The point of union with a bone: insertion Function Force transmission between muscle and bone Sustain high tensile stresses Conserve substantial muscular energy during locomotion Energy storage capacity Enables the muscle belly to be at a convenient distance from joint Satisfies kinematic and damping requirements Function Withstand tensile forces while retaining flexibility Structure Orientations: Parallel to direction of tensile force Larger collagen fibers than in ligaments Structure of Tendons Collagen Fibers In Vitro Tensile Test Tissue is elongated to failure Prescribed rate Changes in force are recorded The force is plotted against time Time axis is proportional to elongation Constant strain rate Response to Tensile Forces Highest tensile strength of any soft tissue Schematic load-elongation curve with 3 distinct regions of response to tensile loading: Mechanical Behavior Energy absorbed to failure: area under the curve Mechanical Behavior Region 1: “Toe” Region Collagen fibers straighten (less prominent than in ligaments because fibers begin more aligned); Continued elongation stiffens tissue Region 2: Linear Response Slope represents stiffness; Micro failure occurs at the end; Elastic recovery at stresses less than 4% Region 3 Corresponds to strains of 3-8% Crosslinks fail; Collagen fibers slide past one another; irreversible changes such as tearing or permanent stretching occurs Region 4: Macroscopic Failure Tensile failure of the fibers Shear failure between the fibers Once maximum load is surpassed ¾ Complete failure occurs rapidly ¾ Fibers recoil and blossom ¾ Tangled bud at ruptured end ¾ Loses Load supporting ability Mechanical Properties (Cont’d) Greater cross-sectional area ¾ ¾ ¾ Larger loads can be applied prior to failure Increased tissue strength Increased Stiffness Longer tissue fibers ¾ ¾ ¾ Greater fiber elongation before failure Decreased tissue stiffness Unaltered tissue strength Injuries Overuse Spontaneous Rupture Dislocation Thermal Injuries Other Injuries Healing Regeneration ¾ New tissue identical to normal tissue ¾ Soft tissue injury healing Scar repair ¾ Repair by connective tissue Structurally Functionally Inferior structural properties Inferior functional properties Or by their combination Healing Process Inflammation phase ¾ Proliferative phase ¾ From the first day of injury to the fourth through seventh day From the seventh through twenty-first day Maturation or remodeling phase ¾ From three weeks to one year The End Anterior Cruciate Ligament ACL: Location ACL: Flexion A-A’ – Anteromedial band B-B’ – Intermediate component C-C’ – Posterolateral aspect of ligament ACL Located between the femur and tibia at the center of the knee Consists of two bundles Origin from lateral femoral condyle Insert into the surface of tibial plateau Intracapsular Extrasynovial Anteromedial Posterolateral Blood supply originates primarily from femoral side http://www.amershamhealth.com/medcyclopaedia/medical/volume%20III%201/CRUCIATE%20LIGAMENT.ASP Posterior Cruciate Ligament: Location PCL: Flexion A-A’ – Small band B-B’ – Bulk of the ligament C-C’ – Anterior meniscofemoral ligament PCL Location ¾ ¾ Origin: Medial femoral condyle Insert: Posterior cortical surface of tibia in the sagittal midline Intimately associated with posterior capsule Covered by Synovium Less susceptible to vascular injury than ACL Blood supply comes from middle geniculate artery Spiral shape permits tibiofemoral rotation Medial Collateral Ligament MCL Primary stabilizer of the medial aspect Location Origin: Medial femoral condyle at the adductor tubercle Fans out in anterior and posterior directions Insert: Medial side of tibia Has both superficial and deep layer Visually appears like a sailboat MCL (Cont’d) Deep Layer Originates at adductor tubercle ¾ Separates distally ¾ Above the joint line ¾ Inserts into the medial meniscus Holds the fibro cartilage in place ¾ Along the inferior meniscal margin Blends into superficial layer Inserts into the medial tibial diaphysis ¾ Has generous blood supply Lateral Collateral Ligament Ligament of Humphrey Ligament of Wrisberg Other Injuries Tendon Avulsions Tendon Strains Partial Tendon ruptures Lacerations Tendon division Foreign bodies in Tendons Bite Injuries and Acupunture induced complications Tendon Composition Joint Rotations Knee Translations Fibrocartilage Fibrocartilage (n.) A kind of cartilage with a fibrous matrix and approaching fibrous connective tissue in structure http://www.kumc.edu/instruction/medicine/anatomy/histoweb/cart/cart12.htm http://www.brainydictionary.com/words/fi/fibrocartilage164589.html Fibroblasts Any cell or corpuscle from which connective tissue is developed Oriented longitudinally with respect to tissue Ovoid or spindle shaped http://www.digitalnaturopath.com/cond/C136641.html Fibroblasts Secrete elements and absorb matrix Components: Collagen Proteoglycans Elastin (recoil) Fibronectin (cell-to-cell adhesion and migration) Joint Capsule Fluid sac at joints that holds joints together Creates skeletal system for synovial membrane Ligaments or tendons thicken the exterior Protects cartilage, muscles, connective tissue Difficult to identify ligaments and tendons from capsule in the body http://physicaltherapy.about.com/cs/disabilities/l/aa111700f.htm http://web1.tch.harvard.edu/cfapps/A2ZtopicDisplay.cfm?Topic=Anatomy%20of%20a%20Joint Collagen Different Types: I>>>III>>V,VI,X,XII Collagen Type I is fibrillar Made up of three polypeptide chains 2α 1 1α 2 Chains are left-handed helixes but are wound together in a right-handed helix http://www.accessexcellence.org/RC/VL/GG/collagen_Elastin.html http://en.wikipedia.org/wiki/Collagen Collagen Hydrogen bonds form between glycines (interchain) and prolines and hydroxyprolines (interchain) Cross-links between collagen molecules “headto-tail” and staggered in parallel Collagen Hydrogen bonds and cross-links contribute to the stability of each molecule and aggregation at the fibril level Result: Structures extremely resistant to tensile forces http://www.orthoteers.co.uk/Nrujp~ij33lm/Orthconntiss.htm Additional Pictures
