Changes to Pediatric Bone & Muscle (10/18c) [Biomedical] Flashcards
Periods of change and variability
Skeletal maturation
Muscle growth
Sexual maturation
Skill acquisition
Growth, size, volume, structure and function of the skeleton are affected by
Hormones
Metabolic factors
Nutrition
Mechanical forces over time
Genetics
Disease or Pathologic processes
Muscle vs Bone Growth
Bone growth is affected by muscle action and activity
Muscle development and function is in turn affected by bone growth
Bone Growth - Growth Hormone (GH)
Stimulates synthesis of IGF-1
GH deficiencies lead to decreased BMD during childhood
Contribute to longitudinal bone growth and mass after birth
During puberty along with sex hormones continue to contribute to bone growth and development
Bone Growth - Insulin like growth factor 1 (IGF-1)
IGF-1 important during skeletal maturation for longitudinal growth, skeletal maturation, and BM acquisition
IGF-1 also important for maintenance of BMC during adulthood
Contribute to longitudinal bone growth and mass after birth
During puberty along with sex hormones continue to contribute to bone growth and development
Bone Growth - Thyroid Hormone (TH)
Direct impact on bone metabolism
Children with hypothyroidism have decreased bone lengthening
Bone Growth - Sex Hormones
Increased estrogens and androgens at puberty
Rapid longitudinal bone growth
Fusion of physis - leads to cessation of bone growth
Increased lean body mass
Contribute to significant variability
Bone Growth - Fibroblast Growth Factors (FGF)
23 different FGFs identified
A lot of interplay, continually regulate skeletal patterning and bone growth throughout the skeletal growth period
In periosteum, perichondrium surrounding the growth plate, chondrocytes, osteoblasts, etc
Bone Growth - Vitamin D
Vitamin D3 is produced in the skin following ultraviolet light exposure
Metabolized in the liver to 25D, then metabolized in the kidney to 1α,25-dihydroxyvitamin D (125D)
125D plays a critical role in the intestinal absorption of calcium and ionic phosphate
Bone Growth - Calcium
Calcium can only be absorbed 500mg at a time (4-6 hrs)
Calcium supplementation has positive effects on bone mineral density (BMD)
Change in dietary habits may be easier to maintain vs taking a pill
Anthropometrics
Measurements of age, growth, and development
- height
- weight
- BMI
- skeletal maturity
- sexual maturity
Measurements of Skeletal Maturity and Bone Age
All use left hand and wrist (due to majority right hand dominance)
Atlas technique of Greulich and Pyle
Tanner-Whitehouse bone-specific scoring
Fels hand-wrist method
Atlas technique of Greulich and Pyle
Modal maturity indicators described for a specific age
Tanner-Whitehouse bone-specific scoring
Total bone maturity indicator score up to 1000
Typically used in Europe
Fels hand-wrist method
Requires software to translate ratings into age
Typically used in North America
Growth Data - Females
Towards the end stage of sexual development for girls (~12.6 yo), 90% had their first period already
2 years left of long bone growth after getting first period
Increasing Growth Velocity: 9-11.5 yo
Peak Growth: 11.5 yo (8.3 cm/yr)
Velocity Stops: 15 yo
Growth Data - Males
Increasing Growth Velocity: 11-13.5 yo
Peak Growth: 13.5 yo (9.5 cm/yr)
Velocity Stops: 18 yo
Timing of Growth Plates with Injury
Consider timing of growth in males and females when there are injuries to determine if there could be growth plates still
Can also influence decision of timing of surgeries
Females — completion of fusion 12.5-18 yo
Males — completion of fusion 15-18 yo
Bone Mineral Content (BMC) aka mass
Total bone tissue in an area
Measured in grams
Bone Mineral Density (BMD)
Amount of bone tissue per volume
Measured as g/cm2 or g/cm3
Peak Bone Mass
Maximal amount of bone tissue following skeletal maturation
Density and Mass Measurements
USE Z SCORES, NOT T SCORES
Dual-energy X-ray absorptiometry (DXA)
Quantitative computed tomography (QCT)
Peripheral QCT (pQCT)
Quantitative Ultrasound (QUS)
Magnetic resonance imaging (MRI)
Continued increase of bone mass and density following end of height growth
Greater bone mass and density associated with decreased fragility fracture
- 10% increase in peak bone mass can decrease female fracture risk by 50%
Still important to optimize bone health after adolescence
Muscle/Lean Body Mass (US measurement study)
Females (3-13 yo) have greater quadriceps muscle mass than males
Possibly hormonal since most females are well into puberty at 13 yo
Muscle/Lean Body Mass (DXA measurement study)
Tanner stage 5
Males have greater extremity lean soft tissue and total body skeletal muscle mass
Tanner stage < 5
No difference in extremity lean soft tissue and total body skeletal muscle mass
No differences between ethnicities
Isometric Muscle Strength Study
Children Ages 4 to 16
Suggests using weight related muscle reference data especially when testing “patients suffering from growth retardation”
Unable to demonstrate gender differences in LE strength in subjects > 15 years old
Differences Based on Socioeconomic Status, Culture, and Ethnicity - Studies
Black vs White
- black children have longer legs and greater long bone strength
- similar femoral density
- 0.5 SD ahead of white children in bone age, could be delayed when age-matched
US Born vs Southeast Asian Refugees
- US heavier and taller
Bone density similar prepuberty for Caucasian, Asian, Hispanic and African American
Pediatric Skeletal Difference
Preosseus cartilage
Physis – growth plate
Periosteum - thicker, stronger, more osteogenic
- Faster and bigger callous
More shock absorption
- Lower BMC and greater porosity
Pediatric Orthopedic Concerns
Growth Plate Injuries and conditions
- Apophysitis
- Salter Harris fractures
Lower Extremity Deformities
Growing Pains
Pediatric Fracture Remodeling
Apophysitis
inflammation or stress injury to the areas on or around growth plates in children
Telltale sign no matter where it is located, if you palpate on it they will jump
To treat, you have to strengthen the muscle and do slow static stretches
Why Does Physis Injury Occur Before Ligament Injury?
Younger age is more likely to have physics injury
Ligaments attach to epiphyses, transferring force to physis (most stresses occur horizontally)
Ligaments shoer and continuous tissue type (greater tensile strength)
Ligaments are generally stronger than bones in kids
Structural Contributions to Physis Injury
Physis is sandwiched between epiphysis and metaphysis of growing bone
- Relatively soft tissue between relatively hard tissue
Histologically, metaphyseal trabeculae are initially oriented longitudinally in long bones
- Progress to horizontal orientation with skeletal maturity
- Predisposes the region to certain fracture modes
Apophysitis - Osgood Schlatter Disease
Traction apophysitis of the tibial tuberosity
Characterized by prominent tibial tuberosity
Significant tenderness to palpation of tibial tuberosity
Apophysitis - Sinding Larsen Johansson Syndrome
Traction apophysitis of the inferior pole of the patella
Significant point tenderness to inferior patella tubercle and proximal patella tendon
Apophysitis - Sever’s Disease
Traction apophysitis of the posterior calcaneus
Pain with shoes, toe walking, running
Significant tenderness to posterior calcaneus
Prominent “pump bump”
Gastroc-soleus tightness
Apophysitis - Iliac Apophysitis
Traction apophysitis along the iliac crest and/or spine
- TFL
- Rectus femoris
- Sartorius
- Gluteus medius
- Abdominal obliques
Track and field athletes and dancers
Growing Pains
No conclusive evidence regarding cause
Diagnosis of exclusion
Anecdotally related to:
- Biochemical/hormonal factors
- Muscle strain during growth
Working while trying to keep up with the length of bone - “instability” at growing junctions
Treatment for comfort
- Massage, hot/cold packs, analgesics
Bone Remodeling Following Fracture - Major Factors
Age – younger children
Proximity to a joint – closer to a physis
Joint Axis – deformity in the plane of “primary” osteokinematic motion
Bone Remodeling Following Fracture - Overgrowth
< 10 yo frequently have a 1 to 3 cm overgrowth in long bone
Bayonet apposition to compensate
Due to physeal stimulation during fracture healing
Youth Resistance Training Programs - Requirements
Specifically designed program
- General muscle strengthening towards end of puberty
- Avoid max lifting until at least Tanner Stage 5 (16-17 yo)
Supervised settings with low instructor : participant ratio
Proper Technique
Safety guidelines for gym behavior and and equipment use
Strength Training Study - Changes in strength likely due to neural components
Motor unit recruitment
Frequency of motor unit firing
Changes in muscle activation
Changes in contractile properties
Strength Training - Factors Contributing to Injury
Poorly designed/supervised programs
Excessive load
Unqualified supervision
Poorly designed equipment
Free access to equipment
