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Test TwoThe AnkleTibiotalar Joint-Hinge joint where convex surface of superior talus articulates with concave surface of distal tibia-Considered to be the ankle jointTibiofibular Joint-A syndesmosis where dense, fibrous tissue binds the distal tibia and fibula together-Dorsiflexors at the ankle include tibialis anterior, extensor digitorum longus, and peroneus tertius, assisted by extensor halluces longus[missed slide]Subtalar joint-Anterior and posterior facets of talus articulate with sustentaculum tali on the superior calcaneusTarsometatarsal and intermetatarsal joints-Nonaxial joints that permit only gliding movements-Enable foot to function as semi-rigid unit; adapt flexibly to uneven surfaces in weight bearingPlantar fascia-Thick bands of fascia that cover the plantar aspects of the foot-During weight bearing, mechanical energy is stored in stretched ligaments, tendons, plantar fascia of foot. This energy is released to assist with push-off of the foot from the surfaceMovements Of The Foot-Inversion: tibialis posterior, tibialis anterior-Eversion: Peroneus longus, peroneus brevis, assisted by peroneus tertiusAnkle Injuries-Ankle Fractures, Tendon Tears (Achilles)-Tendonitis-Usually insidious in onset-Improves with light activity-Labs and radiography not helpful-Ankle Sprains: 25% of all sports injuries-Stress Fracture Causes-Increasing amount or intensity of an activity too quickly (most common); hard or uneven running surfaces; improper or old shoes; untreated biomechanical imbalances-Flat Foot: Not isolated; affects the dynamics of the foot. Patients standing on a flat foot usually have:-Valgus position of the heel (turned outwards)-Pronation of the midfoot, usually referred to as hyperpronation (midfoot turns inwards)-Valgus (turned out) position of the forefootThe HipWhat is the Hip Joint?-Ball and socket joint where the head of the femur articulates with the concave acetabulum-More stable than the shoulder because bone structure, and number & strength of muscles and ligaments crossing the joint-Pelvic girdle has two ilia and the sacrum; rotates forward, backward, laterally to optimize hip positioningMobile AND Stable-Strong bones, powerful muscles, strongest ligaments; length and obliquity of femoral neck-Mobility is due to the long neck, which is narrower than the diameter of the head-Far more mobility, but creates more stress under it; hip breaks are usually in this area-Femoral neck is angulated in relation to the shaft in 2 planes: sagittal and coronalMovements at the Hip-Flexors: Iliacus and psoas major, assisted by pectineus, rectus femoris, sartorius, and tensor fascia latae-Extensors: Gluteus maximus and hamstrings: biceps femoris, semimembranosus, and semitendinosus-Abductor: Gluteus medius (assisted by gluteus minimus)-Adductor: Adductor magnus, adductor longus, and adductor brevis (assisted by gracilis)Loads on the Hip-Major loads acting on the hip during stance include the weight of body segments above the hip, tension in the hip abductor muscles, and the joint reaction force generated in accordance with Newton’s third law-The hip is a major weight-bearing joint that is never fully unloaded during daily activities. In addition to body weight, the tension in the large, strong hip muscles further adds to compression at the jointBiomechanics-To maintain stable hip, torques produced by body weight are countered by abductor muscles’ pullJoint Reaction Forces-Force generated within a joint in response to forces acting on the joint-In the hip, it is the result of the need to balance the moment arms of body weight and abductor tension-Maintains a level pelvis-2W standing; 3W in single leg stance; 5W walking; 10W runningThe SpineNormal Functions of the Spine-Protect spinal cord and nerves-Support the body weight and external load (stability)-Allow motion of the body for various activities (flexibility)-33 vertebrae, 23 intervertebral disksErector Spinae-Iliocostalis, longissimus, spinalis-Counteracted by the abdominal muscles in the front of the bodyIntervertebral Disc-Hydrostatic, load-bearing structure between the vertebral bodies-Nucleus pulposus and annulus fibrosus-No blood supply-L4-5, largest avascular structure in the body-Anatomy: Annulus fibrosus, nucleus pulposus, and vertebral end plateNucleus Pulposus-Type 2 collagen strand and hydrophilic proteoglycan-Water content: 70-90%-Confine fluid within the annulus-Convert load into tensile strain on the annular fibers and vertebral end plate-Chondrocytes manufacture the matrix componentVertebral End Plate-Cartilaginous and osseous component-Nutritional support for the nucleus-Passive diffusionFacet Joints-Synovial joint-Rich innervation with sensory nerve fiber-Same pathologic process as other large synovial joints-Share 18-24% of the lumbar spine load-Percentage can change with altered mechanics; in increased extension, Zygapophyseal joints will assume more of compressive loadLumbar Spine Motion-Three joint complex-Intervertebral disc and 2 facet joints-Ligamentous structure, vertebral bodyArticulations-1. Interbody joints: Capable of translations and tilts in all directions-2. Zygapophyseal articulation (facet): True synovial joints; fibroadipose meniscoid structuresPathomechanics-Exaggerated Lordosis: Abnormal exaggeration of lumbar curve; weakened abdominal muscles; tight hip flexors, tensor fasciae latae, and deep lumbar extensors; increased compressive stress on posterior elements; predisposing to lower back pain-Flat back posture: Relative decrease in lumbar lordosis; COG shiftLumbar Disc Herniation-Inflammatory; biochemical; vascular; mechanical compressionClinical Anatomy-Disc injury: Annular disruption, fissuring, annular defect-Contained herniation: Non-contained herniation; extruded; sequestratedSpinal Disorders-Trauma-Tumor-Infection and inflammatory disease-Deformity-Cervical and low-back painBiomaterialsBackground-Historically, biomaterials consisted of materials common in the laboratories of physicians, with little consideration of materials properties-Early Biomaterials:-Gold: Malleable, inert metal; used in dentistry-Iron, Brass: High-strength metals; rejoin fractured femur-Glass: Hard ceramic, used to replace eyes (cosmetic)-Wood: Natural composite, high strength to weight used to limb prostheses-Bone: Natural compositeHistory-1st gen: Bio-inertness (since 1950s)-2nd gen: Bioactivity (ingrowth, cell exchange) (since 1980s)-3rd gen: Goal to regenerate functional tissue (since 2000s)What is a Biomaterial?-Nonviable material used in medical devices, intended to interact with biological systems-Any material that comes in contact with tissue, blood or biological fluids, intended for use in prosthetic/diagnostic/therapeutic/storage application without adversely affecting the organism-Biocompatibility: Ability to perform with appropriate host response in specific application-Host Response: Response of host organism (local and systemic) to implanted material or deviceCommon Biomaterials-Silicone rubber; Dacron; cellulose; PMMA; polyurethanes; hydrogels; stainless steel; titanium; alumina; hydroxyapatite; collagenMaterial Selection Parameters-Mechanical; conductivity; diffusion; water absorption; bio-stability; wear; biocompatibilityMaterials-Glasses & Ceramics: Highly biocompatible-Metals: To the extent they don’t oxidize-Polymers: Hit and miss-Coatings: Improve biocompatibility or ingrowthPolymeric Biomaterials-Advantages: Ease of manufacturability to produce various shapes; ease of secondary processability; reasonable cost; and availability with desired mechanical and physical propertiesImplants-Trauma vs. arthroplasty-Hip, knee, shoulder, plates/breaks/screws, hip/neck problems-Arthroplasty: Replacing/remodeling joint-Knee-Total knee arthroplasty (TKA) vs. compartmental-Design-Implants all come with their own personal tool belt-Fixtures and gauges-Uni-condylar replacement: Patello-femoral replacement (material: Oxinium)-Artificial patella: can’t put bone back on the steel implant-Not a good idea to take out ACL/PCL if it can be helpedHip-Femur (proximal): metal on metal; metal on polyethylene-Wearing out on bearing surface-Possible to break the neck of the femur again-Hip stress problems: FoS; neck failure; forces applied to proximal femur from legs and tendons-Hip Stress Problem: GOING to be on the test (stress on femoral neck of the hip; analyze stresses, compare strength)Shoulder-Made from cobalt-chrome (CoCr) and polyethylene -Screws into scapulaAnklePiece on talusTrauma-Bone-fixation: Titanium-stamped plates – contour to bone-Plates, screws, rods, wire, etc.Spinal Implants-Disc Implant-Past: Infusion and fixation (still needed for correcting deformities and stabilization)-35% stainless steel, 65% Ti64 (titanium alloy)Replacements: Trend is toward functional disc replacements-Two implants are currently undergoing controlled clinical evaluation in multicenter studies:-Bryan Disc-Prodisc-C-Others are nearing final stage of clinical testingInjuries and Injury Criteria-Bone and joint failure analysis-Femur axial stress; femur torsional stress-Injury criteria-Head; torso; femurFemur Fracture Classification-Type 0: no small fragments-Type 1: Insignificant butterfly fragment with transverse or short oblique fracture-Type 2: Large butterfly of less than 50% of the bony width, >50% of cortex intact-Type 3: Larger butterfly leaving less than 50% of the cortex intact-Type 4: Multiple fragmentsFemur Break on Bolster-Axial force on femur (tibia break if force is applied lower)-Softened the bolster-Testing showed axial forces were not enough to cause a break-Then discovered tensing of tendons caused additional stress to axial stress, causing breaksStresses to Knowσ=F/Aσ=Mc/Iτ=V/Aτ=Tr/JSpiral Fracture in the Femur-Common example: skiing-How to calculate stress?-Torsion of hollow shaft: τmax=Tc2/JModeling and Testing of Injuries-Injury-Bone force to break-Location and loading condition; test and simulation-Joint injury-Location and loading condition; test and complicated simulation-System injury-Test and simulation; complex loading cases-Correlating analysis/modeling with cadaver data for injury prediction/prevention-Modeling: Kinematic and/or FEAMore Complex Questions-Beyond single bones or joints – systemsHead Injury-Acceleration has been roughly correlated to head/brain injuryHead Injury Criterions-1. FMVSS 208 requires that HIC be less than 1000, over no more than a 36ms t1 to t2, which is the injury limit for the 50th percentile male-Same for ECE R94 and R95 (but called Head Protection Criterion)-HIC = max[1/(t1-t2) * int(t1t2) a(t) dt]2.5*(t2-t1)-2. 3ms Criterion: Head acceleration must not exceed 80 g’s for 3ms to avoid injuryNeck Injury Criterion-1. NIC = 0.2arel(t) + vrel(t)2-arel = relative acceleration between CoG of head and T1-vrel = relative velocity between CoG of head and T1-Less than 15 m2/s2 to avoid neck injury-2. Neck Protection Criterion (Nkm)-Nkm = Fshear/Fsc + Moment/Mc-Nkm must not exceed 1.0-Fsc = 845N at neckMc = 47.5 Nm in extension; 88.1 Nm in flexion-3. ECE R94: Extension moment < 57 Nm-4. FMVSS 208 Limits: Flexion 190 Nm, Extension 57 Nm, Tension 3300 N, Compression 4000 N, Shear 3100 NThorax Injury Criterions-1. Viscous Criterion (VC)-VC = V(t) x C(t) = d/dt (D(t) x D(t)/b)-V(t) = velocity of deformation D(t) of the thorax-C(t) = percentage deformation D(t) compared to initial torso thickness b-ECE R95 and R94, and SAE J1727 require VC < 1.0Femur Force Criterion-FFC < 9.07 kN compression for less than 10ms-FFC < 7.58 kN compression for 10-60ms-ECE R94Tibia Injury Criterions-1. Tibia Index-TI = M/Mcrit + F/Fcrit; M = Moment; F = Compressive Force-Mcrit = 225 Nm; Fcrit = 35.9 kN for the 50th percentile male-Max compressive force F < 8.0 kN-TI < 1.3 (ECE R94)Motion, Gait, and TestingMotion: Kinematics/kinetics equationsMoments of inertiaMotion tracking/measurement and gaitProstheticsMADYMO (mathematical dynamic models)General Motion-Most movements are likely a combination of both linear and angular motion, but the internal kinetics are angularAngular Momentum-For linear motion: M = mv = Iω; L = mk2ω-Moment of Inertia: Inertial property for rotating bodies represents resistance to angular acceleration based on both mass and the distance the mass is distributed from the axis of rotation I = Σmr2-Radius of Gyration: Distance from the axis of rotation to a point where the body’s mass could be concentrated without altering its rotational characteristics; used as the index for mass distribution for calculating moment of inertia I = mk2-Angular Law of Acceleration: T = Iα = mk2α (where α is rate of change of angular velocity)Movement of Force or Torque-The effectiveness of a force to produce rotation about an axis-To calculate: force x perpendicular distance from the fulcrum; units = Nm-To increase torque, generate a larger force or increase lever arm-I for lower leg = ~0.3 kg?m2Measuring Motion-Kinematics: High speed cinematography and videography; stroboscopy; optoelectric; electrogoniometry; accelerometry-Kinetics: Pressure and force transducers; force platform; isokinetic dynamometer-Other: Electromyography-What is measured: Position, displacement, and distanceWhat Might We Measure?-Speed, velocity, acceleration-Kinetics: Inertia, Force, load cells/torqueGait Analysis: ObjectivesTo learn and understand:-General descriptive and temporal elements of the normal walking movements-Prosthetics-Important features and components of both the swing and stance phases of gait cycle-Joint range of motion and muscle activity during walking-Differences in movement patterns, muscle activity, range of motion, and walk/run forces-Gait changes with normal aging-Causes of problems in diseaseGait Changes with Normal Aging-Lower walking speeds; shorter sped and stride lengths; reduced plantar flexor force production; reduced hip extension; increase in step width; etc. (older people step wider and closer together)Normal Gait Is Dependent On-Free passive joint mobility-Appropriate timing of muscle-Appropriate intensity of muscle action-Normal sensory input (proprioceptive, vestibular, visual)Prosthetics-Replicate the lost limb’s kinetics AND kinematics-Aiming for similar: mass/CG, moment of inertia/radius of gyration; if joint, similar stiffness/dampingSimulation-MADYMO (mathematical dynamic models)-ANSYS explicit dynamics/LSDYNALikely Test 2 Topics-Math Problem: Stress on femoral neck of hip will for sure be on the test-Structures and materials of the spine-Anatomy of the hip-Spine problem: Normal and shear force through spine of a person bending over-Biomaterials-Injuries, types of breaks, injury criterions, etc.-Dynamics/fluids, probably a calculation problem-Spine, hip-Likely a rotational inertia calculation problem; not 100% certain ................
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