KNES 355 Final Exam Review Part 2

biological maturation, skeletal system + growth injuries

What are the most common techniques for assessing maturity? When are they used?

• somatic maturity (age at peak height velocity, maturity offset)

  • growth studies + clinically

• skeletal maturity (hand-wrist radiograph)

  • pediatric clinical research

• sexual maturity (genitalia, breast + pubic hair development)

  • pediatric non-clinical research

• endocrine maturity (blood draw for circulating estrogen or testosterone)

  • clinical research + treatment programs

• dental maturity (# of erupted teeth, level of tooth calcification)

What is maturity offset?

years from peak height velocity

What is the average age at peak height velocity (APHV) for girls and boys?

girls: 11.5

boys: 13.5

Distinguish between early, average, and late maturers for girls and boys?

girls:

• early → 1 year before average APHV

  • <10.5 years

• average → 1 year before or 1 year after average APHV

  • 10.5 - 12.5 years

• late → 1 year after average APHV

  • >12.5 years

boys:

• early → 1 year before average APHV

  • <13.5 years

• average → 1 year before or 1 year after average APHV

  • 13.5 - 14.5 years

• late → 1 year after average APHV

  • >14.5 years

How is percent of attained adult height used to determine maturity?

pre-pubertal = <88%

pubertal = 88-95%

post-pubertal = >95%

What are the advantages of using APHV or % attained adult stature for assessing maturity?

APHV: estimates are valid when used close to APHV (~after age 10)

% attained adult stature: can be estimated throughout childhood/adolescence

Why is a radiograph of the hand + wrist used to assess skeletal age?

• sequence of events is predictable

• universal

• rate of development varies

• many bones from which to make assessment

• region not sensitive to radiation (low risk)

• can be used for one-time assessment + longitudinally

How many bones are in the hand/wrist at maturity?

30

How is skeletal age used to determine maturity status?

skeletal age - chronological age

± 1 year = average maturer

< 1 year = late maturer

> 1 year = early maturer

What are the advantages of sexual maturity assessment?

• non-technical

• relatively inexpensive + reliable

• can be self-assessed, at any time

______________ sex characteristics are used in male maturity assessment. This includes what?

______________ sex characteristics are used in female maturity assessment. This includes what?

primary, penis/testes development

secondary, breast size + shape, pubic hair distribution (males + females)

What is the alternative secondary sex approach for girls for assessing maturity? What are the strengths + limitations?

menarcheal age

strengths:

• most girls experience it

• memorable occurrence, accurately recalled

• usually predictable in order of events

limitations:

• only useful in girls

• used as a reference only after it occurs

How does timing of maturity impact performance in sports?

• early-maturing youth have temporary advantage in sports that demand strength, speed + power

• late-maturing youth eventually catch-up if they persist in or are retained by sport

  • may be more technically skilled

What is bio-banding?

players are grouped by % of adult height (grouped by similar maturity) vs. chronological age

What are the pros and cons of bio-banding for both early and late maturers?

pros:

• late: leadership + game-play, increased confidence, lower perceived injury risk, less physically challenging, impact game play, demonstrate wider range of physical + technical skills

• early: skill development, lower perceived injury risk, adopt more team-oriented playing style, more physically + technically challenging

cons:

• late: social/psychological factors with “playing down”

• early: not real life, parent buy-in and

What are windows of opportunity in maturity + performance?

• skill development during childhood prior to PHV

• strength gains after PHV

What are the components of bone?

• inorganic components:

  • ~65% of bone weight, mostly inorganic calcium + phosphate

• remainder:

  • 25% organic matrix, collagen

  • 10% water

What is cortical bone? What percentage of our bones are cortical bone?

• ‘compact’ bone

• external part of long bones

• dense, calcified tissue

• ~80% of bones

• structural support, protective functions

What is trabecular bone? What percentage of our bones are trabecular bone?

• ‘spongy’ or ‘cancellous’ bone

• metaphyses of long bones, vertebrae, iliac crest

• inner network of thin, calcified trabeculae

• active metabolic role

• ~20%

What are the 3 types of bone cells? What does each one do?

• osteocytes → mature bone cells

• osteoblasts → bone forming cells

• osteoclasts → bone resorbing cells

What is Wolff’s Law?

bone will optimize structure, so as to withstand functional loading, and to ensure the metabolic efficiency of locomotion

What is bone growth?

the accrual of bone mass through bone formation during childhood and adolescence

• changes in shape + length

• under endocrine control

• ceases following puberty, with epiphyseal closure

What is endochondral bone formation?

• formation of hyaline cartilage which will later be replaced by bone, responsible for growth in length of long bones

  • primary ossification center in the hyaline cartilage, bone collar forms around the sides of the cartilage

  • cavity (medullary canal) forms within primary ossification center

  • secondary ossification center at the epiphysis

  • epiphyseal growth plate eventually fuses

What is appositional growth?

direct production of bone without cartilage transition, responsible for growth in girth of long bones

In long bone growth, the epiphysis expands circumferentially due to the __________________________, further elongating the bone. Growth in bone length = ______________ and ______________ expansion.

secondary ossification center, metaphyseal, epiphyseal

What are the 4 zones of the epiphysis/epiphyseal plate? What occurs in each zone?

• zone 1: resting zone

  • cells are relatively inactive

• zone 2: proliferating zone

  • chondrocytes (cartilage cells) rapidly divide + produce collagen

• zone 3: hypertrophic zone

  • cells increase in size + organize into columns

• zone 4: terminal zone

  • chondrocytes stop producing collagen + die

  • calcification occurs

At any point in time, the growth plates within a single long bone are growing at different rates. What is the way to remember which ends of which bones grow faster?

the ‘bathtub’ rule

growth plates above the water line are the fastest growing

What is bone modeling?

osteoblast + osteoclast activity at different places at the same or different times

• formation/resorption uncoupled, not sequential as in remodeling

• new bone formed by osteoblasts on outer surface (periosteal surface)

• bone resorbed by osteoclasts on inner (endocortical surface)

How does bone modeling affect the bone? When does it usually occur?

• alters shape + mass

• increases bone strength

• primarily in the growing years

• regional response to local mechanical factors

As the ends of bone grow longitudinally, _____________ and _____________ modelling occur to preserve bone shape.

formation, resorption

To preserve cortical thickness during growth, formation modeling occurs on the ________________ surface and resorption modeling occurs on the ________________ surface.

periosteal (outer), endocortical (inner)

What is bone remodeling?

osteoblast + osteoclast activity on the same site, at the same time, but in specific sequence

• coupled action (resorption followed by formation)

• replaces old bone + adds new bone

  • temporary lag between removal + formation (fragility)

Bone remodeling is the predominant bone process modifying mass in _________ but occurs concurrently with bone modelling during ____________. It repairs _______________ on bone.

adults, growth, everyday stress

Peak bone mineral content occurs after ___________. Age at peak bone mineral content velocity is _______ in boys vs. girls. Magnitude of PBMCV is ______________ in boys.

APHV, later, greater

Peak bone mass + strength occurs when?

early 20’s

Boys have greater bone ______ and greater _____________ area, which places bone mass further from the neutral axis, leading to increased bone strength.

area, medullary canal

Adolescence is characterized by __________________ and __________________ in relation to bone. Aging is characterized by ______________, reduced __________________ and _________________.

rapid bone growth, increases in strength, thinning of cortex, bone density, strength

What is stress?

force applied per unit area

What is strain?

deformation of a material → amount bone deforms when stress is applied

What are the 3 rules for bone adaptation?

1. bone responds to dynamic rather than static loading

   • adaptation increases with increases in strain magnitude + strain frequency

2. short bouts of loading are more osteogenic (bone promoting) than longer duration bouts

   • ceiling effect for bone tissue stimulation (bone desensitizes after longer durations)

3. bone becomes used to routine strains; structural change is driven by abnormal strains

   • bone responds to unusual strain distribution

in short:

1. dynamic loading

2. short, frequent bouts with recovery periods

3. abnormal, non-routine strains

Larger bone gains are seen when training is started _____________ puberty or in __________ puberty.

before, early

What is unique about children’s bones compared to adults?

more porous + flexible which allows for greater bending before breaking vs. adults → unique fracture patterns

What is the most common fracture pattern in kids?

buckle fracture (bone compression)

What is a greenstick fracture?

cortex fails on the tension side (analogy to green wood that only breaks on the outside)

in adults, this mechanism would usually result in complete fracture

Which zone of the growth plate is the weakest?

hypertrophic zone

List + describe the 5 Salter-Harris fractures.

1. type I (slipped/separated)

   • separation of epiphysis from metaphysis

2. type II (above the growth plate)

   • through growth plate + metaphysis

3. type III (lower than the growth plate)

   • through growth plate + epiphysis

4. type IV (through the growth plate)

   • through all 3 elements

5. type V (rammed growth plate)

   • crush injury of growth plate

Which Salter-Harris fracture is the most common?

type II

Which Salter-Harris fracture is rare, difficult to see on an X-ray, has a poor prognosis and is almost always diagnosed retrospectively when growth arrest occurs?

type V (rammed)

What is Sever’s disease?

affects growth plate at back of heel, attachment point for Achilles tendon

• repetitive stress from running, jumping, etc. causes pain + inflammation

What is Osgood-Schlatter disease?

swelling + irritation of the growth plate at the proximal tibia, pain + swelling below patella, patellar tendon pulls on growth plate causing injury + pain (caused by activities involving lots of running + jumping)

How does the injury pattern for children match the pattern of growth?

growth distal to proximal

• Osgood-Schlatter usually more common in older age groups

• Sever’s disease usually more common in younger age groups

Late maturers have higher incidence of overuse injuries in the year before PHV and during PHV compared to their early or average maturing peers. Why?

exposed to greater training load + higher intensity games due to their greater chronological age