KN

RAD 1310 Week 2 Notes: Osteology and Arthrology

Osteology and Arthrology: Week 2 Notes (RAD 1310)

  • What osteology and arthrology mean

    • Osteo = Greek for bone; arthro = Greek for joint; logy = study of or the word on (as used here in context)
    • Osteology = study of bones; arthrology = study of joints
    • Key counts in the adult body:
    • There are 206\text{ bones} total
    • Axial skeleton = 80\text{ bones} (skull, spine, ribs, sternum)
    • Appendicular skeleton = 126\text{ bones} (extremities, shoulder girdle, pelvic girdle)

  • Why bones matter

    • Support, protection, movement, storage of minerals (e.g., calcium)
    • Hemopoiesis: marrow cell production (red marrow) occurs in cancellous bone
    • Yellow marrow in the medullary canal stores fat and is related to immunity and bodily function; long bones host yellow marrow
    • Radiation sensitivity: long bones’ yellow marrow can be affected by radiation; take precautions, especially with younger patients

  • Bone structure and components

    • Compact bone: hard outer shell; thicker at the metaphysis
    • Cancellous (spongy) bone: trabeculae; contains red marrow
    • Medullary canal/cavity: hollow shaft region where yellow marrow is produced
    • Periosteum: fibrous covering on outside of bone (except where cartilage is present)
    • Cortex: the outer layer of compact bone (edge of compact bone)
    • Endosteum: inner lining of bone
    • Articular cartilage: hyaline cartilage; radiolucent; enables smooth gliding at joints
    • Radiographic appearance notes:
    • Cancellous bone appears darker/grainy on images
    • Compact bone appears as white lines at the edges in 2D radiographs
    • Medullary canal appears bright white at its dense outer regions and grays toward the center because it’s hollow

  • Growth and ossification overview

    • Intramembranous ossification
    • Quick bone formation; protects major organs (e.g., skull, thorax)
    • Endochondral ossification
    • Slower, gradual replacement of cartilage; enables bone length/height; occurs at the ends of long bones
    • Growth centers and regions
    • Primary growth center located in the diaphysis (shaft)
    • Epiphyses at the ends of long bones; metaphysis is the widening zone between diaphysis and epiphysis
    • Epiphyseal plates (epiphyseal plate) are growth plates; red/or dark line on radiographs; growth occurs at this area
    • Distinguish between epiphyseal plate and epiphyseal growth center: two different structures adjacent to each other
    • Epiphyses are growth centers; plates are growth zones between shaft and ends
    • Epiphyseal plates typically disappear in late teens to early twenties as growth ends

  • Shapes of bones (bone taxonomy)

    • Long bones: elongated (e.g., femur, humerus, tibia, fibula, forearm bones)
    • Short bones: cube-like (e.g., tarsals, carpals)
    • Flat bones: protection and broad surfaces (sternum, ribs, skull, scapula)
    • Irregular bones: vertebrae, facial bones, coxal bones, etc.
    • Sesamoid bones: embedded within tendons to reduce friction and improve tendon mechanics; notable example: patella (largest sesamoid); additional sesamoids exist in hands and feet

  • Pathology overview: bone disease, trauma, and degenerative conditions

    • Degenerative diseases often present in joint spaces and progress with age; can occur after trauma at a younger age
    • Trauma types: fractures (bone breaks) and dislocations (bone out of place at joint)
    • Fractures arise from loads that disrupt the cortex; dislocations arise from forces separating bone from its joint

  • Fractures and loading mechanics

    • Open (compound) fracture: fracture with skin breach; higher infection risk
    • Simple (closed) fracture: fracture contained within skin
    • Displaced fracture: bone ends are separated; nondisplaced fracture: ends remain in approximate alignment
    • Directions of displacement: lateral, medial, posterior, anterior
    • Mechanisms of loading: compression, tension, shear, torsion, bending
    • Compression: smashing or pushing together (e.g., vertebral compression fractures in elderly after falls)
    • Tension: pulling apart; stress fractures in runners/metatarsals
    • Shear: sliding cut across the bone; transverse or oblique fractures; may accompany dislocation
    • Torsion: twisting fracture; common in femur with pivot/rotation or twist injuries; often displaced; spiral fracture
    • Bending: occurs in more pliable bones (younger patients); greenstick fractures (incomplete fracture where bone bends and cracks on one side)

  • Fracture patterns and pediatric considerations

    • General fracture types to memorize: compression/impacted, depressed (e.g., skull), longitudinal, stress fractures (repetitive stress)
    • Pediatric fracture characteristics
    • Greenstick fracture: incomplete fracture with angulation; typical in children; cast often required
    • Buckle (torus) fracture: minimal angulation; often treated with removable splint; limited cortical disruption
    • Plastic deformation: bending without a full fracture due to elasticity of pediatric bone; may mimic a fracture
    • Complete vs incomplete fractures: angulation threshold often around 9^ ext{o}; complete fractures cross the bone
    • Fracture healing and remodeling in pediatrics: depends on fracture type and treatment; simple breaks may heal with near-normal appearance; more complex fractures may show deformity if not surgically treated

  • Growth plate (Salter-Harris) fractures

    • Salter-Harris classification: Types I–V; used to describe growth plate injuries in children
    • Type I: growth plate disrupted with lateral/slippage through plate; growth plate injury without metaphyseal/epiphyseal fracture
    • Type II: fracture through metaphysis with punched growth plate involvement (metaphysis injury with plate injury)
    • Type III–V: involve epiphysis and/or metaphysis and/or plate; higher numbers indicate more severe involvement and greater risk of growth disturbance; Type V can obliterate the plate and halt growth, potentially requiring surgical intervention
    • Note: open physes (growth plates) in children/young teens; plates close in early twenties

  • Avulsion fractures and diagnostic clues

    • Avulsion fracture: ligament or tendon pulls a fragment of bone away; common in ankle, toes, fingers, knee posterior region
    • Important diagnostic caveat in pediatrics: avulsion injuries can resemble growth plate abnormalities; look for adjacent signs such as fat pads or sail signs (e.g., elbow) indicating fracture
    • Sail sign fat pad/Sail sign: fat pad displacement on elbow radiographs may indicate fracture

  • Ossification, healing, and post-injury imaging basics

    • Ossification summary: intramembranous (quick protection bones) vs endochondral (slower, length growth) ossification
    • Fracture healing stages
    • Inflammatory stage: hematoma formation and acute inflammation; lasts about 1\text{ week}
    • Reparative phase I: soft cartilaginous callus forms around fracture ends; lasts 2!-\,3\text{ weeks}
    • Reparative phase II: cartilaginous callus calcifies; early calcified spongy bone forms; cancellous bone participates in healing
    • Remodeling stage: calcified callus replaced with mature, dense bone; spongy appearance reduces; final restoration may resemble pre-injury bone
    • Radiographic progression of healing: soft callus → hard callus → remodeling
    • Imaging considerations with casts/splints
    • Splints: radiolucent or non-radiolucent; do not remove splints; imaging through splints is possible
    • Casts: thickness increases affect radiographic exposure; adjust technical factors accordingly
      • Small/medium plaster cast: increase mass by 50 ext{ \,%} or maintain ~5{-}7\text{ kV} increase
      • Large plaster cast: increase mass by 100 ext{ \,%} or increase KV by ~8{-}10\text{ kV}
      • Fiberglass cast: increase mass by 25\% or KV by ~3{-}4\text{ kV}
    • Practical imaging tips in the ER
    • Always support both ends of joints and fracture sites; consider an extra person to assist
    • When moving injured patients, balance patient safety with imaging needs

  • Bony terminology (landmarks and features)

    • Projections and processes
    • Condyle: rounded process at a joint
    • Epicondyle: projection above the condyle (8 total in the body)
    • Coracoid and coronoid processes (2 coracoid; 4 coronoid in the body)
    • Styloid processes (8 total)
    • Trochanters: on the femur (greater and lesser trochanters)
    • Tubercle (small projection) vs Tuberosity (larger projection)
    • Spine, eminence, crest: ridges on bones
    • Depressions and openings
    • Foramen: a hole for vessels or nerves to pass through
    • Fossa: a pit or hollow
    • Groove: long depression
    • Sinus: a deeper recess or cavity within a fossa

  • Arthrology: joints and their classifications

    • Proximal-to-distal naming convention: for joint naming, start with the proximal bone then the distal bone (e.g., carpo-metacarpal joints; interphalangeal joints for between phalanges)
    • Functional vs Structural classification
    • Functional: degree of movement
    • Structural: tissue type at the joint ends; determines what joints are made of
    • Functional subcategories (three):
    • Diarthrodial: freely movable joints
    • Amphiarthrodial: limited movement
    • Synarthroial: no movement
    • Structural subcategories (three):
    • Fibrous
    • Cartilaginous
    • Synovial
    • Fibrous joints (three types): sutures, syndesmosis, gomphosis
    • Fibrous joints are generally synarthrodial or amphiarthrodial (little to no movement)
    • Sutures: cranial sutures
    • Syndesmosis: e.g., distal tibiofibular joint (slight movement allowed)
    • Gomphosis: teeth in sockets
    • Cartilaginous joints
    • Typically synarthrodial or amphiarthrodial (limited/no movement)
    • Symphysis (e.g., pubic symphysis; intervertebral discs)
    • Synchondrosis (e.g., ribs–sternum articulation; epiphyseal plates; growth plate areas)
    • Synovial joints (six classifications; all diarthrodial)
    • Gliding (plane/arthrodia): slight sliding; intercarpal and intertarsal joints
    • Hinge (ginglymus): one plane of movement; flexion/extension; e.g., elbow, knee, interphalangeal joints
    • Pivot (trochoidal): rotation around a single axis; e.g., radial–ulnar joints; C1–C2 (atlas-axis) in the spine
    • Condyloid (ellipsoidal): two planes of movement; e.g., metacarpophalangeal joints; metatarsophalangeal joints; allows flexion/extension and some abduction/adduction
    • Saddle (sellar): two planes with complementary surfaces; more range than hinge; example is the first carpometacarpal joint (base of the thumb)
    • Ball-and-socket (spheroidal/true anarthrosis): greatest range of motion; e.g., glenohumeral (shoulder), hip joint; ball fits into a socket (convex/concave arrangement) with two axes of movement
    • Synovial joint features
    • Capsule enclosing the joint; fluid-filled cavity containing synovial fluid
    • Synovial joints are more prone to dislocation due to fluid; but dislocations and fractures can occur with excessive stress

  • Practical takeaways for image critiques and exams

    • Memorize functional vs structural categories and the six synovial joint types with their movements
    • Be able to identify bone regions on radiographs: compact vs cancellous bone; medullary canal; epiphysis/metaphysis/diaphysis; epiphyseal plates
    • Recognize growth plate injuries (Salter-Harris) and their radiographic features
    • Distinguish avulsion fractures from physeal plate injuries in pediatric patients; look for fat pads/sail signs as indirect indicators of fracture
    • Understand healing stages and how casts/splints affect imaging and technique
    • Recall key terms for bone surfaces and landmarks for image description and report accuracy

  • Quick reminders and study tips

    • Pause and review if needed; make flashcards for each term and fracture type
    • Expect image critiques to require identification of bone regions, fracture types, and joint classifications
    • Use the acronyms and visual cues (e.g.,
    • Diarthrodial = freely movable (think “jazz fingers” for some examples),
    • Gliding = plane joints, simple sliding movements, etc.)
    • When in doubt, describe both functional and structural aspects of a joint for a complete critique

  • Sources and extra notes

    • Several images and references were mentioned as external sources; consult slide citations for visuals and additional examples if needed
    • Remember: this is week 2 material, building on prior fundamentals; expect repetition across image critiques and exams

  • Closing reminder

    • This content covers a lot of material in osteology and arthrology; take breaks, review, and come back ready to apply concepts to real radiographs