Estimation of age from bones

The age of an individual can be determined from a combination of data provided by:

A. Skull.

B. Mandible and teeth.

C. Appearance of ossific centers.

D. Union of epiphyses.

A. Skull:

a- Dimensions:

In mature infant the circumference of the head is 13 inches. Its length is 5 inches and its width is 4 inches.

b- Fontanelles:

Posterior fontanel is closed at full term, while anterior fontanel is closed at about 18-24 months after birth.

c- Sutures:

• The condylar portion of the occipital bone fuses with the squamous portion at 3 years and with the basal portion at 5 years.

• Frontal suture closes at 3-5 years (except in negroid skull where it persists).

• The basioccipital and basisphenoidal suture closes at 23 years.

• The sagittal suture starts to close from the inner aspect of its middle part at 25 years and is completely closed from the outer plate at about 30 years.

• The coronal suture closes about the age of 40 years.

• Lambdoid suture closes about the age of 50 years, starting from the lambda downwards.

• At the age of 70 years, all skull bones are closed and faint except the suture between the temporal and parietal bones which remains open until extreme old age.

B. Mandible and teeth:

a) Mandible:

• In infants, the angle between the body of the mandible and the ramus is obtuse (small mandible that caries the milk teeth). The mental foramen near the lower border.

• In middle life, the angle becomes right angle. The mental foramen is midway between upper and lower border

• The senile mandible has an obtuse angle again, the teeth are lost and the alveolar margins are absorbed. So, the mental foramen is higher.

b) Teeth: There are two sets of teeth:

1. Milk teeth (temporary, primary or deciduous).

2. Permanent teeth (secondary).

- Milk teeth: they are twenty in number (4 incisors, 2 canines and 4 molars in each jaw). They are small, narrow, bluish white and delicate. The first dentition (central incisors) begins at the 6th month.

- Permanent teeth: they are thirty two in number (4 incisors, 2 canines, 4 premolars or bicuspids and 6 molars in each jaw).

- They are big, broad, heavy and strong. Permanent incisors have usually serrated edges. The 4th and 5th sockets are firstly occupied by the flat milk molars, which will be later replaced by bicuspid teeth which have two cusps (no milk bicuspids).

- A canine tooth has monocusp while a molar tooth has more than two cusps. The first erupted permanent tooth is the first molar (at 6 years). The teeth appear first in the lower jaw and then in the upper jaw.

Milk dentition:

Twenty teeth start to erupt about 6th month after birth in the following order:

Permanent teeth:

Thirty two teeth start to erupt about the age of 6 years in the following order:

N.B.:

- The space behind the second milk molar denotes the age above 2 years (3-5 years). While the space behind the second permanent molar denotes the age above 12 years.

- There are variations in the age of teeth eruption, depending on dietetic factors and some diseases e.g. delayed with rickets and early in syphilis.

Fig : Sequence of eruption of milk and permanent teeth

C. Appearance of ossific centers:

1- During intrauterine life

2-After birth:

• Ossific center of the head of femur appears at end of the first year.

• Ossific centre of the lower end of the radius appears at the end of the second year, it reaches 2/3 the breadth of the epiphysis at 7 years.

• Ossific centre of the upper end of the radius appears at 6 years.

• Ossific centre of the upper end of the ulna appears at 12 years.

D. Union of epiphyses:

1. In the upper limb:

a. Humerus:

• The trochlea unites with the capitulum at 14 years. They unite with the shaft at about 15 years.

• Lateral epicondyle unites with the shaft at about 16 years. Medial epicondyle unites with the shaft at about 17 years.

• Head of humerus unites with the shaft at about 20 years.

b. Radius and Ulna:

• The upper end of the ulna and radius unite with the shaft of its bone at about 16 and 17 years respectively.

• The distal ends of both bones (wrist) unite with their shafts at about 20 years.

c. Hands:

• The epiphyses of the metacarpals and phalanges unite with their shafts at about 18 years.

2. In the lower limb:

a. Femur:

• The lesser trochanter, greater trochanter and head of the femur unite with the shaft at about 16, 17 and 18 years respectively.

• The lower end unites with the shaft at about 21 years.

b. Tibia and Fibula:

• Lower end and upper end of the tibia and fibula unite with the shaft at about 18 (ankle) & 21 years respectively.

c. Feet:

• The epiphyses of the metatarsals and phalanges unite with their shaft at about 18 years.

3. Pelvis:

- Hip bone:

• Pubic ramus unites with the ramus of the ischium at about 6 years.

• Illium, ischium and pubic bones unite at about 14-15 years resulting in disappearance of the Y-shaped suture in the acetabulum.

• The epiphysis of the ischial tuberosity unites at about 21 years.

• The epiphysis of the iliac crest unites at about 23 years

- Sacrum:

Fusion of sacral segments starts between 20 – 24 years and completed at about 25 years.

4. Hyoid bone:

The greater cornu of the hyoid bone unites with the body at about 40 years.

5. Sternum:

• The xiphoid process unites with the body of the sternum at about 40 years.

• The manubrium fuses with the body at about 60 years.

6. Clavicle:

- The acromial end unites with the shaft at about 18 years.

- The sternal end unites with the shaft at about 23 years.

Fig : union of epiphysis in hip bone , clavicle , sternum and hyoid bones .

N.B.:

a) These mentioned ages (from 14 years and above) belong to males while females show union of epiphyses 2 years earlier.

b) At old age: the bones become lighter, more brittle and fatty marrow increases and enlarges the medullary cavity. The skull bones become rarefied and degenerative changes occur in the articular surfaces of the bones.

c) In the livings, the bones can be examined by X-rays while in the dead persons by dissection or x-rays.

d) Medullary cavity of the humerus reaches the surgical neck at 30 years in males and reaches the anatomical neck at 33 years.

Category: Forensic Medicine Notes