His right elbow appears broken, and part of the bone in the upper arm appears to be protruding from the skin. There appear to be fragments of bone in the wound.

Upstream

Background

Downstream

Direct Cause

Indirect Cause

12 year old boy fell forward while running

potential vitamin/mineral deficiency due to dietary restrictions resulted in weak bones

Anatomy of long bones

Cell

Tissue

Organ

Bone Growth

Bone Formation

Bone Remodeling: consists of bone deposit and bone resorption

Stages of Bone Healing

Raw materials required for bone growth and repair

Classification of Bone Fractures

Epiphysis

Compound comminuted fracture of right distal humerus

How the location of the break affects treatment

Suspected vitamin and mineral deficiency causing rickets

compound: the bone has perforated the soft tissue

comminuted: bone has fractured into shards

Treatment

Surgery

Antibiotics

Immobilization of joint/bone

Physical therapy

Because of lactose intolerance, vitamin and mineral supplements needed

Deficient in vitamin D and calcium

Elbow requires specific type of brace - hanging U splint

requires traction

Rickets will resolve within months with proper treatment

closed reduction

Prepubescent: may have involvement of epiphyseal plate

Limb development may be affected

risk of cellulitis and osteomyelitis

Spongy

Compact (Lamellar)

made up of a honeycomb of small, needle-like or flat pieces of bone called trabeculae

open spaces are filled with red or yellow bone marrow

dense outer layer on bone that appears smooth and solid

suspected rickets

Diaphysis

Location of epiphyseal plate

Metaphysis

tubular shaft that forms long axis of bone

ends of long bones that consist of compact bone externally and spongy bone internally

where the epiphysis and diaphysis meet

compact bone surrounds medullary cavity that contains yellow marrow in adults

where bone growth occurs

articular cartilage covers joint surfaces

Membranes

Periosteum

Endosteum

white, double layered membrane that covers external surfaces except joints

Osteogenic Layer

Fibrous Layer

contains many nerve fibers and blood vessels that continue on to the shaft through nutrient foramen openings

anchoring points for tendons and ligaments

outer layer consisting of dense irregular connective tissue consisting of Sharpey's fibers that secure bone to matrix

inner layer abutting bone and containing primitive osteogenic stem cells that give rise to most bone cells

delicate connective tissue membrane covering internal bone surface

covers trabeculae of spongy bone tissue

lines canals that pass through compact bone

contains osteogenic cells that can differentiate into other bone cells

red marrow produces red blood cells, platelets, and many white blood cells

yellow marrow produces fat, cartilage, and bone

Osteogenic cells

Osteoblasts

Osteocytes

Bone lining cells

Osteoclasts

also called osteoprogenitor cells

mitotically active stem cells in endosteum and periosteum

when stimulated, differentiate into different types of bone cells

some remain as osteogenic cells

bone forming cells that secrete unmineralized bone matrix called osteoid

actively mitotic

amitotic mature bone cells in lacunae

maintain bone strength and act as stress or strain sensors

respond to mechanical stimuli on bone - both positive and negative

communicate information to osteoblasts and osteoclasts so bone remodeling can occur

flat cells on bone surfaces believed to also help maintain matrix

called periosteal cells on outer surface, endosteal cells on internal surface

derived from the same hematopoietic stem cells that become macrophages

giant, multinucleate cells that function in bone resorption

when active, located in depressions called resorption bays

cells have ruffled borders that increase surface area for enzyme degradation of bone

also helps seal off area from surrounding matrix

consists of osteon (Haversian system), canals and caniculi, and interstitial and circumferential lamellae

organized around lines of stress

Organic

Inorganic

includes bone cells and osteoid

resilience of bone is due to sacrificial bonds in/between collagen molecules that stretch/break to dissipate energy and prevent fractures

if no additional trauma, bonds reform

Hydroxyapatites (mineral salts)

make up 65% of bone composition

consists mainly of calcium phosphate crystals between collagen fibers

responsible for hardness and resistance to compression

Also called osteogenesis

begins in month 2 of fetal development

Postnatal growth occurs until early adulthood

Endochondral Ossification

Intramembranous Ossification

Both occur up to about week 8 of fetal development

bone forms by replacing hyaline cartilage

bones are called cartilage (endochondral) bones

form most of skeleton

bone develops from fibrous membrane

called membrane bones

essentially all bones inferior to the skull except the clavicle

Five major steps:

  1. Bone collar forms around diaphysis of cartilage model.
  1. Central cartilage in diaphysis calcifies then develops cavities.
  1. Periosteal bud invades cavities, leading to formation of spongy bone
  1. Diaphysis elongates and medullary cavity forms
  1. Epiphysis ossify.

Hyaline cartilage remains only in epiphyseal plate and articular cartilage

forms frontal, parietal, occipital, temporal, and clavicle bones

Four steps involved:

  1. Ossification centers are formed when mesenchymal cells cluster and become osteoblasts.
  1. Osteoid is secreted then calcified.
  1. Woven bone is formed when osteoid is laid down around blood vessels, resulting in trabeculae
  1. Lamellar bone replaces woven bone and red bone marrow forms.

outer layer of woven bone forms periosteum

long bones grow lengthwise at epiphyseal plate

Plate has 5 zones:

  1. Resting zone
  1. Proliferation zone
  1. Hypertrophic zone
  1. Calcification zone
  1. Ossification zone

area of cartilage on epiphyseal side of plate that is relatively inactive

area of cartilage on diaphyseal side is rapidly dividing

area with older chondrocytes closer to diaphysis; cartilage lacunae enlarge and erode, forming interconnected spaces

surrounding cartilage matrix calcifies; chondrocytes die and deteriorate

chondrocyte deterioration leaves spiculesof calcified cartilage at plate junction

spicules are eroded by osteoclasts and covered with new bone by osteoblasts, forming spongy bone

medullary cavity enlarges as spindles are eroded

Epiphyseal plate closes at the end of adolescence
(18 for women, 21 for men)

no more longitudinal growth of bone

Resorption

function of osteoclasts

secrete enzymes and protons that break down matrix

acidity converts calcium salts to soluble forms

also phagocytize dead osteocytes and demineralized matrix

Deposit

new bone matrix laid down by osteoblasts

osteoid seam: band of unmineralized bone matrix that marks area of new matrix

calcification front: abrupt transition zone between osteoid seam and mineralized bone

Three types are either/or

Displaced or non displaced

Complete or incomplete

Compound (open) or simple (closed)

Compound: skin is penetrated

Simple: skin is not penetrated

Displaced: ends are out of normal alignment

Nondisplaced: ends retain normal position

Complete: broken all the way through

Incomplete: not broken all the way through

can also be described by location, appearance, and nature of break

Other types of fractures:

Comminuted: bone broken into three or more fragments

Compression: bone is crushed

Spiral: ragged break occurs due to twisting forces

Epiphyseal: epihysis separates from the diaphysis at the epiphyseal plate

Depressed: broken bone is pressed inward

Greenstick: bone breaks incompletely, like a green twig; only one side breaks, the other bends

  1. Hematoma formation
  1. Fibrocartilagenous callus formation
  1. Bony callus formation
  1. Bone remodeling

capillaries grow into hematoma, phagocytic cells clear debris

torn blood vessels hemorrhage, causing a blood clot called a hematoma to form

site is swollen, painful, and inflamed

fibroblasts secrete collagen fibers to span break and connect broken ends

fibroblasts, cartilage, and osteogenic cells begin reconstruction of bone

new trabeculae appear in fibrocartilagenous callus

callus is converted to spongy bone

excess material on diaphysis exterior and within medullary cavity is removed

compound bone laid down to reconstruct shaft walls

final structure resembles original structure