LA DIALÉCTICA DE LOS DERECHOS DEMOCRÁTICOS EN LA ACTUALIDAD

Like the mandible, the hyoid bone (Figs 13.1A and B) is also a horse-shoe shaped bone suspended in the neck.

Parts of the Hyoid Bone

Hyoid bone consists of the following parts: • A body.

• Lesser cornu/horn. • Greater cornu/horn.

The lesser cornu fuses the body of the hyoid bone superiorly whereas the greater cornu fuses the body of hyoid bone inferiorly.

Radiographic Anatomy of Hyoid Bone

• The hyoid bone is well appreciated on the lateral cephalogram. • On the lateral cephalogram, the hyoid bone appears

boomerang-shaped radio-opaque area below the inferior to the middle of the mandibular body.

• The greater and lesser cornu of the hyoid bone appear as radio-opaque on the lateral cephalogram.

• The body of the hyoid bone on the lateral cephalogram appears as radio-opaque.

• In children, greater cornu is seen separately as it is not fused to the body of hyoid but in adults both lesser and greater cornu are fused to the body of hyoid bone.

Cephalometric Landmarks (Points) on Hyoid Bone

Cephalometric landmarks seen on the hyoid bone are of anatomic origin and are as follows:

Table 13.1: Cephalometric landmark related to hyoid bone Cephalometric

landmark Abbreviation Type Origin

Hyoid Hy or H Unilateral anatomic

Hyoid

Abbreviation

Hy–Hyoid is abbreviated using English alphabet and is

expressed as capital or upper case H followed by lower case or small y, and both are written continuously without any space between the alphabets.

Figures 13.1A and B: hyoid bone

Section 5

Cephalometric Landmar

ks R

elat

ed t

o Cervical Bones

H–Hyoid is abbreviated using English alphabet and is

expressed as capital or upper case H.

Note: Most widely and commonly used abbreviation for hyoid

is Hy.

Definition

Hyoid (Figs 13.2A to D) is the most superoanterior point on the body of the hyoid bone.

According to Robert M Ricketts

According to Robert M Ricketts, the hyoid is the point at the anterior-superior margin of the body of the hyoid.1

Type

Hyoid is a unilateral, anatomic, hard tissue cephalometric landmark.

Tracing of Hyoid on the Lateral Cephalogram

The body, lesser and greater cornu of the hyoid bone appears as boomerang shaped radio-opaque area. The superioanterior point on the body of the hyoid bone is the point of hyoid. It is a unilateral, anatomic hard tissue cephalometric landmark.

Reference

1. Ricketts RR. Provocations and perceptions in cranio-facial orthopedics– dental science and facial art. Rocky Mountain Inc. 1989;797-803.

Figures 13.2A to D: hyoid

A B

Cha

p

ter

14

Radiographic anatomy of cervical vertebrae (fig. 14.1)

Anteroinferior to the occipital condyle, which appears as a curved radio-opaque line, the anterior arch of the atlas can be identified as a small triangular radio-opaque area. The apex of the triangle faces the posterior border of the mandibular ramus, while its base faces the odontoid process of the axis. The central mass of the atlas, which appears as radio- opaque area superimposed on the radio-opaque shadow of the odontoid process. Posterosuperior to the inferior articular facet is the superior articular facet, which can be identified as radio- opaque area. Its superior border is concave and corresponds with the contour of the occipital condyle. Next to the superior articular facet is the posterior arch with the posterior tubercle. At the superior border of the posterior arch is a groove for the vertebral artery and the first cervical nerve.

The odontoid process and the body of the axis appear as a triangular radio-opaque area. The odontoid process represents the apex of the triangular points toward the occipital condyle. The spinous process of the axis appears as a radio-opaque projection extending superiorly.

The radiographic appearance of the third cervical vertebra (C3) to the seventh cervical vertebra (C7) is similar. The body of the each of these cervical vertebrae appears as wedge shaped radio-opaque area situated behind the pharyngeal space. Posterior to the body is the spinous process. The transverse processes, the superior articular process and the inferior articular process appear as radio-opaque area superimposed on the shadow of the body and the spinous process. The body of each cervical vertebra is separated from the adjacent ones by the intervertebral disc, which appears as radiolucent strip. At the midpoint between the third and fourth cervical vertebrae is the hyoid bone, which is separated anteriorly.

cephalometric Landmarks on cervical vertebra

Cephalometric landmarks seen on the cervical vertebra are of anatomic origin and are as follows (Table 14.1):

Table 14.1: Cephalometric landmarks related to cervical vertebra Cephalometric

landmarks Abbreviation Type Origin

cv2ap cv2ap Unilateral anatomic

cv2ip cv2ip Unilateral anatomic

cv2ia cv2ia Unilateral anatomic

cv3sp cv3sp Unilateral anatomic

cv3ip cv3ip Unilateral anatomic

cv3sa cv3sa Unilateral anatomic

cv3ia cv3ia Unilateral anatomic

cv4sp cv4sp Unilateral anatomic

cv4ip cv4ip Unilateral anatomic

cv4sa cv4sa Unilateral anatomic

cv4ia cv4ia Unilateral anatomic

cv5sp cv5sp Unilateral anatomic

cv5ip cv5ip Unilateral anatomic

cv5sa cv5sa Unilateral anatomic

cv5ia cv5ia Unilateral anatomic

cv6sp cv6sp Unilateral anatomic

cv6ip cv6ip Unilateral anatomic

cv6sa cv6sa Unilateral anatomic

cv6ia cv6ia Unilateral anatomic

cephalometric Landmarks (Points) Related to cervical vertebra

• cv2ap–The apex of the odontoid process of the second

cervical vertebra.

• cv2ip–The most inferoposterior point on the body of the

second cervical vertebra.

• cv2ia–The most inferoanterior point on the body of the

second cervical vertebra.

Cephalometric landmarks