Long Bone Measurement & Orthoroentgenography

What type of ruler is used for long bone measurement?

Bell-Thompson ruler

Why can’t you use standard radiographs for long bone measurement?

not recommended due to diverging rays causing distortion and closed joint spaces

What are some reasons for long bone measurement in children?

• bone dysplasia - dwarfism

• osteogenesis imperfecta - brittle bone disease

• poor nutrition/calcium intake - rickets

• injuries affecting growth plates (epiphyses)

Explain dwarfism

• short stature

• under 4’ 10” as an adult

• common type is achondroplasia (skeletal dysplasia)

  • occurs in long bones

  • trouble converting cartilage to bone

Explain osteogenesis imperfecta

• genetic disorder

• bones that break easily

• abnormal or too little collagen

Explain osteomalacia

• “rickets”

• deficiency of vitamin D, calcium, and/or phosphate

• soft, weak bones

Injured growth plates can lead to ___

crooked or misshapen bones, short limbs, and/or arthritis

How can you use radiation protection in long bone measurement exams?

• careful positioning

• close collimation

• immobilization (to reduce repeats)

What are some reasons adults would get long bone measurement tests done?

• one leg visibly longer

• limping or toe walking

• trauma or infection

• back/hip/ankle pain

• deformities

• bone tumors

Explain orthoroentgenography

• 3 exposures taken on 1 large cassette

• patient supine, legs extended, feet dorsiflexed

• 40” SID

• ruler placed between legs and taped to table

• 1 exposure each on hips, knees, and ankles

What are the 3 measurements used in orthoroentgenography?

1. highest point on femoral head

2. between femoral condyles to lowest point

3. between ankle joints

Explain the centering for lower extremity orthoroentgenography

1. hip: midway between ASIS and symphysis

2. knee: ¾” distal to apex of patella

3. ankle: midway between malleoli

Explain the centering for upper extremity orthoroentgenography

1. shoulder: 2” medial and 2” distal to upper outer border (include entire humeral head)

2. elbow: mid elbow - ¾” below epicondyles

3. wrist: mid-wrist between styloid processes

Explain the teleoroentgenogram exam

• single exposure

• weight-bearing, erect

• 14×52 LW IR

• 72” SID

• bilateral

• tape ruler between legs

• remove shoes

• crest through talus

Explain CT teleoroentgenography

• measurements are made utilizing computer

• more radiation dose, more expensive, longer exam

• more accurate measurements