Core - Section 01: Basic Science

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AAOS COMPREHENSIVE ORTHOPAEDIC REVIEW

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AAOS COMPREHENSIVE ORTHOPAEDIC REVIEW

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SECTION 1: BASIC SCIENCE

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SECTION 1: BASIC SCIENCE

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1. Cellular & Molecular Biology, Immunology, & Genetics

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1. Cellular & Molecular Biology, Immunology, & Genetics

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This is a double-stranded deoxyribose

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DNA

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This is a portion of a gene that codes for mRNA

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An exon

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This translates and transfers DNA information into protein synthesis machinery

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mRNA

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Transfers amino acids to mRNA

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tRNA

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The process by which DNA → mRNA

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Transcription

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The process by which mRNA → protein

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Translation

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Achondroplasia is related to a defect in what?

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FGF receptor 3

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This is the process of converting extracellular signals to cell response

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Signal transduction

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Inflammatory stimuli may stimulate _______ to express RANKL, a key molecule of _____________.

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osteoblasts; osteoclastogenesis

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___________ is manipulation of DNA or RNA segments to produce specific desired DNA, RNA, or amino acids.

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Recombinant technology

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Infliximab is a monoclonal antibody for ________; it prevents ________ from binding to its receptors.

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TNF-α; TNF-α

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_________ is a competitive inhibitor of TNF-α signaling; it is a fusion protein that combines the ligand-binding domain of the TNF-α receptor.

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Etanercept

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_____, ______ and ______ can control excessive osteoclastogenesis.

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OPG, anti-TNFs, and anti-RANKLs

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2. Biomechanics

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2. Biomechanics

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Is when the sums of all forces and moments are zero.

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Mechanical Equilibrium

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What kind of diagrams show the locations and directions of all forces and moments acting on a body?

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Free body diagrams

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What describes the motion of objects without regard to how that motion is brought about?

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Kinematics

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What involves analysis of the effects of forces and/or moments that are responsible for motion?

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Kinetics

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Each joint has specific _____ ______ because of the particular characteristics of the joint and the muscle actions that cross the joint

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load interactions

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3. Biomaterials

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3. Biomaterials

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Force per unit area

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Stress

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The amount of energy stored in a loaded material?

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Strain energy

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In a stress-strain curve, this represents the area under the curve?

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Strain energy

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This is the ratio of stress to strain; it measures the ability of a material to maintain its shaper under the application of external load.

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Modulus of Elasticity

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The _______ the modulus of elasticiy, the stiffer the material

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higher

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This is the quantity that is determined by the cross-sectional area and distribution of tissue around a neutral axis in torsional loading.

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Polar Moment of Inertia

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The ________ the polar moment of inertia, the stiffer and stronger the material.

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larger

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A ____________ material has properties that are rate dependent or have time-dependent responses to applied forces.

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viscoelastic

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An ________ material has the same mechanical properties in all directions. In general, ceramics and metals are isotropic.

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isotropic

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An ______ material has properties that differ depending on the direction of load. Bone, muscle, ligament, and tendon all are all this type of material.

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Anisotropic

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These are metals composed of mixtures or solutions of metallic & nonmetallic elements that are varied to influence their biomechanical properties, including strength, stiffness, corrosion resistance, and ductility.

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Alloys

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The properties of a polymer of dictated by these 5 attributes.

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1. chemical structure (the monomer); 2. the molecular weight (the number of monomers); 3. physical structure (way monomers are attached to each other); 4. isomerism (different orientation of atoms in some polymers); 5. crystallinity (packing of polymer chains into ordered atomic arrays).

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These are are solid, inorganic compounds consisting of metallic and nonmetallic elements held together by ionic or covalent bonds.

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Ceramics

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4. Skeletal Development

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4. Skeletal Development

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Formation of the bony skeleton occurs via either __________ bone formation or _____________ bone formation. _________________ bone formation occurs through osteoblast activity; _______________ occurs at the growth plates and within fracture callus.

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intramembranous, endochondral; Intramembranous; endochondral ossification

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In the _________________, blood-borne precursors of osteoblasts and osteoclasts are delivered by the capillaries. This process signals the transition from the embryonic to the fetal period and occurs first at the ____________.

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primary center of ossification, humerus

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The total length of the growth plate depends on ________________________.

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the number of cell divisions of the progenitor cell

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The region of the hypertrophic zone where mineralization occurs is known as the ______________________________.

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zone of provisional calcification

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SCFE involves the ___________________ zone.

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hypertrophic

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The genetic mutation in achondroplasia is a defect in ________________.

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FGFR-3

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Growth plate injuries occur when the mechanical demands of bone exceed the strength of the __________________ . The _________________- law states that increasing compression across the growth plate leads to decreased growth.

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epiphysis–growth plate metaphysis complex; Hueter-Volkmann

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Diastrophic dysplasia is a defect in _____________________.

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proteoglycan sulfation

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Bacterial infection affects the _____________ portion of the growth plate.

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metaphyseal

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Scurvy is caused by a vitamin C deficiency with resultant decrease in ________________ and ______________.

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chondroitin sulfate and collagen

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5. Bone & Joint Biology

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5. Bone & Joint Biology

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_______________ (long and short bones) occurs through a cartilage model; ________________ (flat bones) results from condensations of mesenchymal tissue.

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Endochondral bone formation; intramembranous bone formation

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The inner __________ of cortical bone is vascularized by nutrient arteries that pass through the diaphyseal cortex and enter the intramedullary canal and are at risk during intramedullary reaming. The outer ________ of the cortical bone derives blood supply from the periosteal membrane vessels. These vessels are at risk with periosteal stripping during surgical procedures.

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two thirds; one third

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The extracellular matrix of bone is composed of __________ mineral components and ________ organic components. The organic matrix is 90% __________ and 5% ___________.

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60% to 70%; 20% to 25%; type I collagen; noncollagenous proteins.

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_________ collagen is fibril-forming and has a triple helical structure (three α chains). The fibrils are intrinsically stable because of noncovalent interconnections and covalent cross-links between ________ residues.

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Type I; lysine

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Mature osteoblast marker proteins include _________, ___________, _________ and __________. The potential fates of a mature osteoblast include _____________ or ____________ or ____________.

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alkaline phosphatase, osteocalcin, osteonectin, and osteopontin; differentiation into an osteocyte or bone lining cell, or apoptosis.

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The marker proteins for osteoclasts include _____, ______ ______, and _______. Osteoclast differentiation and activity are regulated in large part by the bioactive factors ______ (positive regulator) and ______ (negative regulator).

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TRAP, calcitonin receptor, and cathepsin-K; RANKL; OPG

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Osteoblast and osteoclast functions are coupled via various systemic and local factors. Regulatory proteins (_____ and _____) secreted by osteoblasts provide direct coupling in bone remodeling.

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RANKL and OPG

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Fractures commonly heal with a combination of endochondral and intramembranous bone formation. Motion at the fracture site results in healing primarily through ___________, whereas stability at the fracture site enables ___________.

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endochondral ossification; direct intramembranous ossification

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Fracture healing includes a sequence of biologic stages including injury, inflammation, hematoma ______, hypertrophic _________ _______, new _____ formation, and _______ to mature bone.

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maturation, cartilage formation, bone, remodeling

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Articular joint synovium is composed of two layers—the _________ ______, which contains tissue macrophage-like cells and fibroblast-like cells that produce _________, and the connective tissue sublining.

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intimal lining; hyaluronin

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6. Articular Cartilage

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6. Articular Cartilage

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Articular cartilage consists mainly of extracellular matrix (ECM), with only a small percentage of _______________, which are responsible for the synthesis, maintenance, and homeostasis of cartilage.

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chondrocytes

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The major components of the ECM are __________,____________ and ________________

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water, proteoglycans, and collagen.

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Articular cartilage is classified into four layers (______________,_________________,______________ and _____________) according to collagen orientation, chondrocyte organization, and proteoglycan distribution.

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superficial, middle, deep, and calcified

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Cartilage is an avascular structure in the adult; this has implications for ______________ and ___________.

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repair and healing

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The breakdown of the cartilage matrix in normal turnover and in degeneration appears to be the action of ____________; their overactivity is implicated in _____________.

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proteinases, OA

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The water content of cartilage ____________ with aging and _________ in OA.

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decreases, increases

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Proteoglycan content and keratan sulfate concentrations ___________ with OA; proteoglycan degradation and chondroitin-4-sulfate concentration _____________.

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decrease; increase

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_____________________ lubrication is the principal mode of lubrication of articular cartilage.

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Elastohydrodynamic

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Superficial lacerations to cartilage rarely heal; deeper lacerations may heal with _______________.

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fibrocartilage

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Inflammatory ______________ and ______________ are responsible for macroscopic and histologic changes seen in OA.

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cytokine; metalloproteinases

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7. Tendons & Ligaments

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7. Tendons & Ligaments

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Tendons and ligaments are materials with highly ordered _______________ ______________.

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hierarchical structure

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The composition of tendons and ligaments is primarily ___________ _________ ________, aligned in the direction of loading (___________).

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primarily type I collagen; anisotropic

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________________ properties describe the capacity of the tissue to bear load; __________ properties describe the quality of the tissue.

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Structural; material

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Tendons and ligaments are _____________ (their properties are time dependent).

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viscoelastic

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Several biologic (eg, age) and environmental (eg, temperature) factors influence the __________ properties of tendons and ligaments.

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mechanical

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Tendon/ligament healing progresses through clearly defined phases: 1. _______________; 2. ____________ & __________ proliferation; 3. ___________/maturation.

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1. hemostasis/inflammation; 2. matrix and cell; 3. remodeling

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________________ & ________________ ligaments have a greater capacity to heal than do ______________ & ________________ ligaments.

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Nonsheathed tendons and extra-articular; sheathed tendons and intra-articular

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For tendon and ligament healing, increased _________ can be either beneficial or detrimental, depending on the anatomic location and type of injury.

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loading

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The physical environment influences tissue maintenance: __________ is detrimental and ___________ is beneficial to the biomechanical properties of these tissues (tendon and ligament).

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immobilization; exercise

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The tendon/ligament __________ is a specialized tissue that is necessary to minimize stress concentrations at the interface between two very different materials (tendon/ligament and bone).

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enthesis

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8. Peripheral Nervous System

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8. Peripheral Nervous System

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Schwann cell myelination speeds transmission of action potentials by ___________ conduction occurring at nodes of Ranvier.

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saltatory

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Most motor and sensory nerves are myelinated except for _____________ and ___________ fibers.

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autonomic; slow pain

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Nerve fibers (axons) are surrounded by __________, collections of nerve fibers (fascicles) by __________, and collections of fascicles by _______________.

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endoneurium; perineurium;epineurium.

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Nerve injury causes loss of distal function in the following sequence: ____________, ___________, ________, __________, __________ and __________. Nerves recover in the inverse order.

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motor, proprioception, touch, temperature, pain, and sympathetics

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___________ is a reversible conduction block (traction or compression); __________ involves axon disruption with preserved neural connective tissue (stretch or crush); ___________ is complete disruption of a nerve (open crush or laceration).

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Neurapraxia; axonotmesis; neurotmesis

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Tissue pressures up to 30 mm Hg can cause paresthesias and increased nerve conduction ____________.

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latencies

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Temperature, age, demyelination, and loss of axons ___________ rate of transmission.

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decrease

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Fibrillations are an EMG finding of abnormal spontaneous activity that occur in muscle fibers ________ after denervation (transient or complete).

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2 to 3 weeks

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Nerve repair (neurorrhaphy) involves reapproximation of the nerve ends with _________ appropriately oriented under minimal tension using a fine monofilament epineurial suture. Group fascicular repair increases scarring at the repair site.

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fascicles

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Nerve grafts may be cabled to increase diameter; they should also be reversed to minimize early ____________________.

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arborization of regenerating nerve fibers.

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9. Skeletal Muscle

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9. Skeletal Muscle

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Muscle fiber is a collection of _______________.

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myofibrils

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_____________ are collections of muscle fibers.

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Fascicles

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Actin’s binding sites for myosin are blocked by ______________.

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tropomyosin

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Know all bands and lines of sarcomere organization—A, I, H, M, and Z.

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Electron micrograph of skeletal muscle illustrating the striated, banded appearance. A = A-band; M = M-line; I = I-band; Z = Z-line. B, The basic functional unit of skeletal muscle, the sarcomere.

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Site of action of both depolarizing and non-depolarizing drugs is the _____________.

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NMJ

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Maximal force production is proportional to muscle _________ ________-_________ ________.

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pysiologic cross-sectional area (PCSA)

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___________ energy system has enough ATP for approximately 20 seconds of activity.

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Phosphagen

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DOMS peaks at 24 to 72 hours post-exercise, is most common in type _______ fibers, and is associated primarily with __________ exercise.

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IIB, eccentric

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___________ contraction generates the highest tension and greatest risk for musculotendinous injury.

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Eccentric

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Muscle strain is most likely in muscles that cross _________ joints.

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two

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10. Intervertebral Disk

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10. Intervertebral Disk

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The disk allows ____________ and provides ________ _________ of the functional spinal unit

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motion; mechanical stability

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The disk is mostly _________ and depends on _________ through pores in the end plate to provide nutrition to the disk cells.

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avascular; diffusion

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Nucleus pulposus cells are more synthetically active in a _________ environment.

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hypoxic

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The nucleus pulposus is normally rich in aggregating proteoglycans (_________ and __________), which attract water and help maintain disk height. The nucleus pulposus has a higher concentration of ____________ than the anulus fibrosus.

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aggrecan & versican; type II collagen

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The anulus fibrosus is a well-organized laminated fibrous tissue composed primarily of _____________.

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type I collagen

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With increasing age, the disk cells produce less _________ and _________, leading to decreases in proteoglycan and water content. As the nucleus pulposus desiccates, disk height is lost and the anulus fibrosus develops ________.

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aggrecan & type II collagen; fissures

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_________ percent of asymptomatic individuals older than 60 years have MRI evidence of disk degeneration.

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90%

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Genetics plays a strong role in disk degeneration, but this seems to involve a multifactorial process that does not fit a ___________ pattern.

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Mendelian

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Disk degeneration is not necessarily a ______ condition.

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painful

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Diskography has a high __________ rate in patients with abnormal psychometric testing results.

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false-positive

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11. Musculoskeletal Biology & Infections

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11. Musculoskeletal Biology & Infections

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The most common general infectious symptom is _____________; it is rare for patients to not report pain as a presenting symptom.

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pain localized to the site of infection

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Septic arthritis in adults is most commonly associated with ____________ in otherwise healthy patients. ____________ is the second most common pathogen causing adult septic arthritis.

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N gonorrhea; S aureus

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Triad of symptoms strongly suggesting Clostridial myonecrosis: ______________, _____________ and _____________________

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(a) progressively severe pain out of proportion to obvious injury, (b) tachycardia not explained by fever, (c) crepitus.

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Bone loss of _______ to _______% is required before the classic signs of osteomyelitis (bone resorption, destruction, periosteal elevation) can be seen on radiographs.

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30% to 40%

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The most sensitive imaging tool for diagnosing osteomyelitis is ______. The classic finding includes a signal change that is due to the increased _______ and _____ content in bone, which is manifested as a reduction in ______ and an increase in ______ marrow signal. The increased signal intensity on T2 images results because the fatty marrow has been replaced by inflammation.

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MRI; edema & water; T1; T2

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Synovial fluid WBC count >_________ or with >90% PMNs is strongly indicative of infection in a TKA.

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2,500/mm3

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__________ is protected from host immune defenses by three mechanisms: (a) Excretion of _______, which inactivates IgG; (b) production of a ______ _________, which reduces opsonization and phagocytosis of the organism; (c) formation of a ________ (a “slime” containing an aggregation of microbial colonies embedded within a glycocalyx matrix that most commonly develops on THA/TKA implants or a devitalized bone surface), which also secludes the organism from host defense mechanisms.

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S aureus; protein A; capsular polysaccharide; biofilm

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Antibiotics have different modes of action (________ and _________ — inhibition of cell wall synthesis; ___________ — binds 30S ribosomal subunit; _________ — binds 50S ribosomal subunit).

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penicillin and cephalosporins; aminoglycoside; clindamycin

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Tuberculosis treatment—Extended triple drug therapy of _________, _________ and ____________ for 6 to 12 months has shown to be effective with osseous extrapulmonary involvement.

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isoniazid, rifampin and pyrazinamide

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The treatment of choice for MRSA is _____________.

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vancomycin

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12. Bone Grafting / Bone Graft Substitutes

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12. Bone Grafting / Bone Graft Substitutes

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Bone grafts may be ____________, _______________ and ______________.

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osteogenic, osteoinductive, or osteoconductive

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Bone healing progresses through three stages: early (________), middle (________), and late (_____________).

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inflammation, reparative, remodeling

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Bone healing may be affected by ______ and ______ factors.

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host & local

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__________ is the gold standard bone graft material.

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Autograft

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_________ has a reported rate of potential HIV transmission of 1 per million.

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Allograft

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_______ have been shown to have significant inter product and interlot variability. They are predominantly osteoconductive.

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DBMs

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Bone marrow aspirates provide potential access to _________ __________precursor cells.

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osteogenic mesenchymal

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Ceramics are inorganic compounds consisting of metallic and nonmetallic elements held together by _________ and ___________.

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ionic or covalent bonds

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BMPs are potent osteoinductive factors of the _______ superfamily.

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TGF-β

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Several forms of electromagnetic stimulation may facilitate bone _________.

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healing