Bone Growth & Development

BPK 375

Bone Growth & Development

When do the first bones ossify? Which is the first bone to ossify? Does exercise affect bone growth &

development?

10 weeks gestation

16 weeks gestation

Osteocyte– Mature bone cell that turns over bone mineral and

assists in repairs Osteoblast

– Immature bone cell that secretes organic components of matrix

Osteoprogenitor Cell– Stem cells whose divisions produce osteoblasts

Osteoclast– Multinucleated cell that secretes acids and enzymes

to dissolve bone matrix

Intramembranous OssificationOssification of Mesenchymal Connective Tissue

Osteoblast

Osteoclast

Osteocyte

Growth of Skull

Fontanelles Suture Joints Proportions

Growth of Vault of Skull

Jaw Growth

Acromegaly

Oversecretion of growth hormone

Prior to growth plate fusion, causes increased height with normal proportions

After fusion, causes bone thickening and connective tissue overgrowth

Endochondral Bone Growth

Short bones e.g. carpals

Articular Cartilage

Periosteum

Haversian System

Compact Bone

Yellow Bone Marrow

Spongy (Cancellous)Bone

Compact Bone

Haversian System

Chondrocytes at the center of the cartilage model begin to hypertrophy and disintegrate as the matrix calcifies

Endochondral Ossification

Blood vessels grow around the edges of the cartilage, and the perichondrial cells convert to osteoblasts. The shaft of the cartilage then becomes ensheathed in a layer of bone

Endochondral Ossification

Blood vessels penetrate the cartilage and invade the central region, growing toward the epiphyses at either end.

Fibroblasts migrating with the vessels differentiate into osteoblasts and begin producing spongy bone

Endochondral Ossification

Endochondral Ossification

Remodelling occurs as growth continues, creating a marrow cavity.

The bone of the shaft becomes thicker, and the cartilage near each epiphysis is replaced by shafts of bone.

Cartilaginous Growth Plate

Metaphyseal Reshaping

HAND Primary Centres

FOOT Secondary CentresFOOT Primary Centres

HAND Secondary Centres

Fuse

Fuse

f.m. = fetal month, m = postnatal month, y = year

Time of Appearance of Primary & Secondary Ossification Centres

Hand most commonly used in studies of child development

Fairly representative of the total maturational status of the skeleton

Greater number of ossification centres than any other area in the arms and legs

Hand is an easy area to X-ray

Skeletal AgeGreulich and Pyle

– radiographic Atlas of Skeletal Development of the hand and wrist

– American children– Reliability: 95% ±0.8 – ±1.0 yrs on repeat

ratingsTanner & Whitehouse

– Bone Specific Ratings– English children– Reliability: 95% ±0.6 yrs on repeat ratings

American boys matured about 6 months earlier than English children

Longitudinal series of X-rays on a girl

X-ray shows bone not cartilage

TW2Tanner-Whitehouse

Bone specific ratings

Fulfill written criteria

Assign score for chosen stage

Bone Maturity Charts

Growth Hormone and Gonadotrophin Deficiency

Turner Syndrome

Bone Maturity Charts

Hippocrates

“That which is used develops and that which is not used wastes away”

Lines of Stress in a metal form loaded at its “head”

Lines of spicules of bone seen in head of the femur

Bone Development in response to Mechanical Forces

Exercise & Bone Growth

HOWELL(1917) DogsRetardation in diameter growth in

later lifeLength & Basic Configuration

genetically determinedWidth influenced by exercise

Some evidence for Longer more Slender bones in sedentary animals (Steinhaus;1933)

Exercise & Bone Growth

KATO & ISHIKO (1966)– Children– Femur and epihyseal plates showed early closure

by several years in heavy workers.– Poor environment

Exercise and Bone Size

BUSKIRK (1956)– Nationally ranked tennis players. – Dominant hands & forearms had longer bones.

IVANITSKY - Soccer players– Femur larger in diameter than nonathlete– Marrow cavity of tibia in runners active over five

years is often enlarged

Demineralization

Bed rest causes a loss in bone mass. Astronauts had decreased bone

mineralization after Gemini V and VI flights. Exercises were arranged on Gemini VII and

deminerallization was reduced.

Bone Density

DONALDSON (1970)– 30 week bed rest– Increased Calcium & Nitrogen in urine– Decrease 4.2% in total body calcium– Decreased bone mineralization– 2hr/day quiet standing prevented the loss

Bone Density

ISSEKUTZ (1966)– 3 hr quiet standing reduced calcium loss– 4 hr supine exercise did not

WYSE & PATTEE (1954)– Human paraplegics did not benefit from weight

bearing using a tilt table

EXERCISE causes increased bone density

Dynamic Changes

Woman with no teeth How do braces work? Why do teeth tend to return to their

original position after braces are removed?

Genetic or Environmental

Boy born without a tibia Fibula surgically moved over One year later fibula had taken

on the appearance of a tibia

Genetic or Environmental

3 year old impaled by nail, causing paralysis of one leg

At time of injury normal hip development

One year later drastic changes