Biomechanics of Tendons and Ligaments PDF

Biomechanics of tendons and ligaments 1. Composition and structure of tendons TENDON - Union between muscles and bones - It is a structure subjected to large tensile forces - Regular dense connective tissue of parallel bundles - Functions: - Transmit the load from the muscle to...

Biomechanics of tendons and ligaments 1. Composition and structure of tendons TENDON - Union between muscles and bones - It is a structure subjected to large tensile forces - Regular dense connective tissue of parallel bundles - Functions: - Transmit the load from the muscle to the bone - Give information to the brain about joint position - Allow movement of the joints thanks to the transmission of muscle contraction COMPOSITION OF TENDONS - Thick bundles of type I collagen - Limited ground substance - Few fibroblasts → Tenocytes TENDON CELLS Sandwiched between collagen fibers and arranged in a network aligned along axis of the tendon - Vascular cells: tendon feeding vessels - Synovial cells: paratenon - Chondrocytes: tendon-bone union - Tenocyted: - The most numerous - Functions: synthesis of the extracellular matrix, maintenance of tendon homeostasis and repair of injuries - Sensitive to mechanical stimuli and adapt the extracellular matrix through anabolic or catabolic changes depending on the magnitude, frequency, direction and duration of the loads STRUCTURE OF TENDONS - Hierarchical fibrillar organization, with a sequence of collagen molecules forming fibrils, fibers and fascicles - Surrounded by various layers that reduce friction with the environment: - Endotenon: cover of the fascicles - Epitenon: cover of the tendon - Paratenon: cover of the epitenon EPITENON + PARATENON = PERITENON - Proteoglycans and glycoproteins aligned with the longitudinal axis of the tendon INNERVATION AND NEUROTRANSMISSION - MECHANORECEPTORS: - Ruffini’s corpuscles: sensitive to stretch (more abundant in areas with high mechanical requirements) - Vater-Paccini’s corpuscles: sensitive to transient mechanical displacements and vibration - Golgi tendon organs: sensitive to strain changes (fusiform and connected to groups of muscles fibers) - Neuromuscular spindles: sensitive to changes in length (information about joint position and joint movements) - NOCICEPTORS: free nerve endings sensitive to stimuli potentially damage to tissue - AUTONOMOUS SYSTEM: receptors located in the walls of blood vessels that are responsible for vasomotor modulation 2. Compositions and structure of ligaments LIGAMENT: - Union between bones - It is a structure subjected to larger tensile forces but less than those of the tendons - Regular dense connective tissue of parallel bundles - Functions: - Joint reinforcement and stability - Guide movements by restricting them in certain angles - Facilitation of proprioceptive information to the central nervous system COMPOSITION OF LIGAMENTS: - Collagen and elastic fibers - Ground substance - Fibroblasts - Similar to tendons but the fibers are less organized - Some of them have more elastic fibers than collagen fibers LIGAMENT CELLS: Compared to other tissues it has poor vascularization and few cells - Fibroblasts: synthesis of procollagen (connection to adjacent cells forming a three-dimensional network) - Fibrocytes: trapped in the extracellular matrix and aligned between fibers - Endothelial cells - Macrophages 75% OF COLLAGEN/ 25% CELLS, GLYCOPROTEIN, PROTEOGLYCANS AND ELASTINE STRUCTURE OF LIGAMENTS: - Hierarchical fibrillar organization, with a sequence of collagen molecules forming fibrils, fibers and fascicles - Surrounded by a thin coating membrane called epiligament with different characteristics in intra articular ligaments because they are surrounded by a synovial membrane INNERVATION AND NEUROTRANSMISSION: - MECHANORECEPTORS: - Ruffini’s endings: sensitive to joint position, intra articular and range and speed of movement - Paccini’s corpuscles: sensitive to acceleration - Golgi receptors: sensitive to strain changes, specially at the end of the range of motion - NOCICEPTORS: free nerve endings sensitive to stimuli potentially damage to tissue 3. Biomechanical properties and ligaments STRESS AND STRAIN: - Stress: load applied to the tissue - Strain: longitudinal deformation the tissue undergoes when loaded - Four stages: - Toe: under minor load → straightening of the crimp inherent in the structure - Linear: greater load → transient linear deformation - Yield: load even higher → irreversible deformation - Failure: maximum load → overall deformation and failure BIOMECHANICAL PROPERTIES: - Quasilinear viscoelasticity: - Elastic property: returning to their original shape after deformation - Viscous property: remaining in the deformed state depending on the strain rate - Tendons: - At low strain rates → absorb more mechanical energy but are less effective in carrying loads - At high strain rates → high stiffness and more effective in transmitting large muscular loads to the bone ETIOPATHOGENESIS OF TENDON INJURIES: - Compression forces (impingement): mechanical pinch of the tendon by a cone. Causes: anatomical abnormalities, soft tissue inflammation… - Friction forces: tendon rubs against a hard surface. Causes: overuse, lack of flexibility… - Tensile forces: when these forces exceed the elastic capacity of the tendon. Causes: overuse - Overuse: low intensity repetitive stimuli. TENDINOPATHY: - Reactive tendinopathy: - Non-inflammatory proliferative response - Short-term adaptation - Homogeneous thickening of a portion of the tendon - Tendon dysrepair: - Tendon healing attempt - Increase matrix degradation and cell number - Collagen separation, matrix disruption and neovascularization - Degenerative tendinopathy: - Changes in cells and matrix - More extensive collagen disruption, widespread cell death and extensive growth of new vessels and nerves - Irreversible changes MOST COMMON TENDON INJURIES: - Subacromial impingement: - Compression-entrapment of the rotator cuff and bursa in the subacromial space - Pain in the anterolateral side of the shoulder and functional inability to raise the upper extremity - Iliotibial band syndrome: - Friction of the iliotibial tendon against the femoral condyle - Pain in the lateral side of the knee, specially when climbing stairs, running or sitting for a long time with knee flexion - Epicondylitis: - Micro Tears of the extensor carpi radialis brevis and fibrosis - Pain in the lateral border of the elbow with inability to perform grasping tasks - Patellar tendinopathy: - Inflammation of the patellar tendon - Pain in the anterior side of the knee TREATMENT OF TENDINOPATHIES: - Therapeutic exercise programmes supervised by physiotherapists: - 14 weeks - 70 sessions (3 weekly sessions of neuromuscular strength training and 2 weekly sessions of aerobic work) - Intensity: 60% - 75% VO2 MAX - Five stages: - Stage 1: isometric contractions to control symptoms and prepare the neuromuscular system for later phases - Stage 2: isotonic and heavy slow resistance exercises, to improve muscle strength and tendon stiffness - Stage 3: strength training through exercises performed with a velocity loss of 20%, to increase muscle hypertrophy - Stage 4: high-load strength training, to obtain maximal strength benefits due to the hypertrophy and the neural adaptations - Stage 5: plyometric training and jumps to improve the energy storage capacity of the tendon. TRAINING IN TENDINOPATHIES: PREVENTION: - Progressive resistance training in athletes at risk. Example: jumping athlete - Avoid very explosive gestures in non-usual sport customers (“weekend athletes”) - Include balance training in relation to the specific sport activity - Not cause overuse of the upper limb in load above the horizontal TREATMENT: - Adapt the mechanical stimuli to the phase of the tendinopathy we are in - Include eccentrics but adapting the load → they are beneficial but risky at the same time - Design long-term programmes → slow progression in load and neural adaptations 4. Factors that affect biomechanical properties of tendons and ligaments TENDON RUPTURES: - Symptoms (total rupture): - Sudden, severe pain - Functional inability - Deformity to the retraction of the fibers - Symptoms (partial rupture): - Diffuse pain maintained over time - Progressive lack of strength - Sometimes: bruising and depression on palpation - Etiopathogenesis: - Sports activity (“weekend athletes”) - Previous tendon degeneration - Use of local corticosteroids - Adverse drug reaction. Example: fluoroquinolones - Background of gout - Blood group 0 - Biomechanical alteration: varus, valgus, hyperpronation… MOST COMMON TENDON RUPTURES: - Achilles tendon rupture: - The contraction of the triceps surae to gain impulse is opposed by body weight - Sports activity: jumping and running - Brunet-Guedj sign and Thompson sign - Patellar tendon rupture: - Eccentric contraction of quadriceps against body weight with knee flexion - High patella and feeling of knee instability - Rotator cuff tendon rupture: - Progressive degeneration by overuse in shoulder abduction - Jobe sign - Thumb tendon rupture: - Extreme force against resistance or fractures of adjacent bones - Interphalangeal joint or extension and no active mobility in the opposite direction TREATMENT OF TENDON RUPTURES: - Conservative approach: - Immobilization with plaster: 4 weeks on equine without load and 4 weeks decreasing the equine progressively and authorizing load CONS: incomplete functional recovery and high recurrence rate - Functional treatment with equine orthosis: 20 days at 30º plantar flexion, with 15-20 kg load; days 20 to 24 at 20º plantar flexion; days 24 to 28 at 10º plantar flexion; and from day 28 neutral position with complete load - Surgical approach: - Reconstruction of the tendon by union of the free endings - After surgery: protocols of early physiotherapy and functional immobilization with dynamic orthosis PROS: better healing, without permanent loss of strength, allowing early rehabilitation with less muscle atrophy and return to normality TRAINING AFTER TENDON RUPTURE: PREVENTION: - Warm-up period → to increase temperature of tissue and extensibility of the fibers - Previous training with eccentric strengthening → to prepare the tissue for the mechanical stimuli - Ask to the customers if they are under any pharmacological treatment TREATMENT: - Proprioceptive training → to recover the body awareness - Take into account factors that caused the injury to avoid them in the first instance, and make a safe readaptation to the injury mechanism.  ETIOPATHOGENESIS OF LIGAMENT INJURIES: - Force exceeding the resistance of ligament tissue - Hyperlaxity or other syndromes involving collagen (Ehlers-Danlos, Marfan…) - Biomechanical alteration. Example: differences in Q angle - Hormonal status: during the menstrual cycle more elastin is produced, so there is more ligamentous laxity - Muscle imbalance SPRAIN (ANKLE): - Distention of the capsuloligamentous apparatus caused by a forced movement beyond the physiological limits - Classification: - GRADE 1: ligament elongation without tear Symptoms: pain and inflammation, without instability - GRADE 2: partial rupture of ligament fibers Symptoms: pain, inflammation, ecchymosis, partial functional inability and partial instability - GRADE 3: total rupture of ligament Symptoms: pain, inflammation, ecchymosis, complete functional inability and relevant instability TREATMENT OF SPRAIN: - First instance → RICE protocol: - Repose - Ice - Compression: functional bandage - Elevation - Therapeutic exercise programme: - Mobility, specially dorsal flexion - Motor control and strength - Proprioceptive training - Plyometric training - Return to play TRAINING IN SPRAINS: PREVENTION: - Analyze the laxity of the ligaments before prescribing exercise → to “play” with the range of motion - Include proprioceptive training → especially in people with background of sprain - Bet on neuromuscular coordination → dual tasks TREATMENT: - Use functional bandage or braces to return to play but do not abuse of these tools - Include exercises for quick changes of direction when the customer has enough strength and motor control - Work on impact exercises progressively LIGAMENT RUPTURES (ACL): - Interruption of the transverse section of the ligamentous tissue that promotes symptoms such as edema, swelling, pain, ecchymosis and functional inability - Mechanism of injury in knee ligaments: - Impulse in a jump and fall with the knee in semiflexion, forced valgus and external rotation of the tibia ACL + ILL + INTERNAL MENISCUS - Turn of the body with the knee in semiflexion, forced varus and internal rotation of the tibia ACL + ELL + IN/EX-TERNAL MENISCUS - Turn of the body with the knee in extension and forced valgus ILL + ACL/PCL - Turn the body with the knee in extension and forced varus ELL + ACL + PCL - Abrude hyperextension of the knee ACL SURGICAL APPROACH (ACL): Replace the torn ligament with a plasty: - Autologous ligamentoplasty: material from the patient himself, extracted from another area → generally from a tendon such as the patellar or quadriceps tendon - Heterologous ligamentoplasty: graft from a tissue bank (cadaver) → risk of rejection After, a long-term rehabilitation program with the physiotherapist based on: - Recovery mobility - Gain strength - Return to the normality in terms of muscle mass - Functional readaptation TRAINING LIGAMENTS RUPTURES: PREVENTION: - Include exercises focused on body awareness and motor control at the hip, knee and ankle - Neuromuscular training (quadriceps and hamstrings) on pre-season and during the season TREATMENT: - Bet on exercises focused on restoring technical skills - Progression from controlled slow pro-planned movements to highly chaotic reactive sport-specific movements - Ensure that the patient is psychologically prepared for each new challenge. JOINT INSTABILITY AND DISLOCATIONS (SHOULDER): Overstretched or torn ligaments → joint instability → dislocation complete and stable separation of two joint surfaces - Symptoms: - Deep and fatiguing pain that is exacerbated by moving the joint - Absolute functional inability - Deformation - Adema Risks: - Increase of the feeling of instability → CHRONIC - Bone injury → fractures of loss of bone - Nerve injury → nerve rupture or nerve impingement TREATMENT OF JOINT INSTABILITY: - Immediate medical treatment aimed at reducing the dislocation - Immobilization of the joint to ensure healing of the damaged tissues - Therapeutic exercise programme supervised by a physiotherapist: - 12 weeks - 36 sessions (3 weekly sessions) - Intensity: 60% - 85% MR - Progression: strength from isometric to isotonic – hypertrophy – neural adaptation (without velocity loss) – functional readaptation - If the conservative approach doesn’t work or the structural damage is enough → surgical approach: labral-anchored capsulorrhaphy or ligamentoplasty TRAINING IN JOINT INSTABILITY: PREVENTION: - Analyze the laxity of the ligaments before prescribing exercise → to “play” with range of motion - Do not abuse of overhead exercises or exercises position of maximal abduction plus external rotation - Ensure strength and stability before looking for hypertrophy TREATMENT: - Be careful with the range of motion of the exercises prescribed - Established a plan to achieve a safe readaptation to the mechanism, of injury - Overlap different stages in a waterfall manner