Di Imaging Final

Roentgenometrics

Quantitative radiographic measurements used to assess structural and biomechanical alterations.

Magnification

Error caused by x-ray beam divergence altering measurement accuracy.

Causes of radiographic distortion

Unequal magnification, projectional distortion, positioning error, anatomic variation, observer error.

Normal sella turcica size

16 mm length × 12 mm depth (40” SID).

Causes of enlarged sella

Empty sella, pituitary tumor, aneurysm, normal variant.

Empty sella syndrome

CSF herniation into sella causing pituitary flattening.

Basilar angle normal

137°–152°.

Platybasia

Flattening of skull base with increased basilar angle.

Basilar invagination

Congenital upward migration of vertebrae into foramen magnum.

Basilar impression

Acquired upward migration due to softened skull base.

Chamberlain line

Posterior hard palate to opisthion.

Normal dens relative to Chamberlain line

≤3 mm above.

McGregor line

Posterior hard palate to inferior occiput.

Normal dens relative to McGregor line

≤4.5 mm above.

McRae line

Basion to opisthion.

Dens relative to McRae line

Should not cross line.

Four cervical alignment lines

Anterior vertebral line, posterior vertebral (George’s), spinolaminar, posterior spinous.

Listhesis

Vertebral slippage.

Causes of listhesis

Degeneration, fracture, dislocation, ligament laxity, physiologic, anatomic.

Normal cervical canal AP (C3–5)

17–18 mm.

Lower cervical canal normal

12–14 mm.

Absolute cervical stenosis

<10mm

Atlantodental interval (adult)

Max 3 mm.

Atlantodental interval (child <8)

Max 5 mm.

Causes widened ADI

Trauma, Down syndrome, congenital anomaly, rheumatoid arthritis.

Ligament preventing ADI widening

Transverse ligament.

Jefferson fracture mechanism

Axial compression.

Rule of Spence

6.9 mm combined lateral mass displacement suggests instability.

C1/C2 ratio >1.15

100% specific for transverse ligament injury.

Cervical lordosis depth method normal

8–12 mm.

Cervical Cobb normal (C2–C7)

35°–45°.

Hyperlordosis cervical

45°.

Hypolordosis cervical

<35 degrees

Harrison posterior tangent normal

34° ± 9°.

Cervical gravity line normal

Passes through anterior portion of C7 body.

Cervical sagittal canal normal

16 mm.

Cervical stenosis relative

10–13 mm.

Retropharyngeal space at C2 adult

<6 mm

Retrotracheal space at C6 adult

<22 mm

Causes widened prevertebral space

Trauma, infection, tumor, edema, hematoma.

Thoracic kyphosis normal young adult

20°–29°.

Thoracic hyperkyphosis

40°.

Lumbar lordosis normal (L1–S1)

50°–60°.

Lumbosacral joint angle mean

18.7° (range 5°–39°).

Ferguson angle normal

27°–57°.

Meyerding Grade I

<25% translation

Meyerding Grade II

26–50%.

Meyerding Grade III

51–75%.

Meyerding Grade IV

76–100%.

Spondyloptosis

100% translation.

Teardrop distance normal

9–11 mm or <2 mm asymmetry.

Widened teardrop causes

Dysplasia, effusion, infection, tumor.

Ilioischial (Kohler) line

Line from iliac wing medial margin to ischial tuberosity.

Coxa profunda

Acetabular fossa touches/medial to Kohler line.

Protrusio acetabuli

Femoral head medial to Kohler line.

Klein line

Line along superior femoral neck to detect SCFE.

Trethowan sign

Klein line fails to intersect femoral head.

Shenton line

Smooth arc along inferior pubic ramus and femoral neck.

Shenton disruption indicates

DDH or femoral neck fracture.

Böhler angle normal

25°–40°.

Decreased Böhler angle

Calcaneal fracture.

Heel pad normal thickness

<23 mm

Heel pad thickening causes

Myxedema, acromegaly, obesity, edema.

Acromiohumeral interval normal

7–11 mm (avg 10 mm).

Narrowed A-H interval

Rotator cuff tear.

AC joint normal

1–7 mm, decreases with age.

Ulnar variance neutral

Ulna and radius same level.

Positive ulnar variance

Ulna >2.5 mm distal to radius.

Negative ulnar variance

Ulna ≥2.5 mm proximal to radius.

Negative ulnar variance association

Kienböck disease.

Positive ulnar variance association

TFCC degeneration, ulnar impaction.

Spina bifida occulta

Failure of laminae closure, most common L5–S1.

Clasp-knife deformity

Enlarged L5 spinous process engaging S1 SBO.

Nuclear impression

Endplate indentation from nucleus pulposus.

Schmorl node

Central intravertebral disc herniation.

Scheuermann disease

Juvenile discogenic disease causing kyphosis.

Scheuermann prevalence

~5%.

Scheuermann onset

12–17 years.

Scheuermann Type I

Thoracic only.

Scheuermann Type II

Thoracolumbar.

Sorensen criteria kyphosis

40° thoracic.

Sorensen wedging requirement

≥3 adjacent vertebrae wedged >5°.

Scheuermann radiographic features

Endplate irregularity, Schmorl nodes, disc narrowing.

Scheuermann associations

Scoliosis, limbus vertebrae, spondylolisthesis.

Scheuermann treatment <50°

Conservative.

Scheuermann treatment 50–75°

Bracing.

Scheuermann treatment >75°

Surgery.