Epiphysis

OSSIFICATION CENTRES AND COMMON PITFALLS IN DIAGNOSIS OF FRACTURES
Ossification Centres
_ The development of primary ossification centres of major longitudinal bones occurs prenatally.
_ Carpal and tarsal bones develop primary ossification centres prenatally but only extensively postnatally.
_ Secondary ossification centres develop mainly after birth, with exception of distal femur.
_ These ossification centres help to determine skeletal age.
_ However, there are great variances in the age of onset of these ossification centres.
Age of Onset of Secondary Ossification Centres

Age of Physeal Closure in the upper and lower limbs

Elbow ossification centres
_ The interpretation of radiographs is made difficult by the changing complexities of the epiphyses. Typical appearances at age 2, 4, 6, and 9 years are shown.
_ C = Capitulum - present usually within the first 2 - 3 years of life
_ R = Radial head - appears at 3 - 5 years
_ M = Medial epicondyle - present by 6 years
_ T = Trochlea - appears at 7 - 9 years
_ L = lateral epicondyle - appears 11 - 14years
_ Olecranon appears between 8 - 11 years



The ossification centre of the medial epicondyle always ossifies before the trochlea. If radiographic examination of a child between 4 and 8 years of age reveals a bony structure in the region of the trochlea, and shows no evidence of the ossification centre of the medial epicondyle, it must be assumed that the ossification centre of the medial epicondyle is avulsed and displaced into the joint.



_ It is not necessary to order an X-ray of the opposite, uninjured limb in every single case of a child presenting with limb trauma, because most fractures are obvious.
_ However, if there is any difficulty in interpreting the radiographs, there should be no hesitation in sending the child for X-ray of the contralateral limb. These may draw attention to slight cortical irregularity of a minor greenstick fracture.
_ The anterior fat pad may or may not be present in a lateral radiograph of the elbow. However, the posterior fat pad is not visible in a normal elbow at any age. Its presence signifies the presence of an occult or hairline fracture, and treatment should be immobilisation of the elbow in a backslab and early referral to the orthopaedic surgeon with X-ray on arrival.

Olecranon

The ossification centre of the olecranon appears around 8 - 11 years and fuse at 14 years.
Diagnosis of an olecranon fracture is usually more straight forward than an elbow fracture, but beware of the following fallacies:
1. The normal epiphyseal line
2. Duplication of the normal epiphyseal line due to obliquity of the projection _ 3. Bifid olecranon epiphysis (normal variant) _ 4. Patella cubiti due to ossification in the triceps tendon

Carpal bones

_ In the first year of life, the capitate (C) and hamate (H) appear at 2 months, the radius (R) at 6 months, and the triquetral (T) at 10 months.
_ After the first year, the lunate (L) appears at 2, the trapezium (Tr) at 2 1/2, the trapezoid (Tz) and scaphoid (S) at 3, and the distal ulna (U) at 4 1/2 years.

Patella

_ The patella ossification centre appears at 3 - 5 years.
_ The fabella (A) is a normal inconstant sesamoid bone in the lateral head of the gastrocnemius; do not mistake it for a loose body.
_ Bipartite patella is a normal variant, and it involves the superolateral aspect of the main patella. It is usually smooth and rounded, in contrast to the sharp and irregular line in acute fractures.

Ankle

_ Do not mistake the common os trigonum accessory bone (A) for a fracture.
_ The epiphyseal line of the fibula (B) may resemble a fracture.
_ The amount of tibio-fibular overlap (C) is dependent on positioning and any diastasis.

Foot


_ The epiphysis of the base of the 5th metatarsal lie parallel to the shaft, while a fracture is usually transverse or slightly oblique.
_ Inconstant accessory bones may be mistaken for fracture or loose bodies: (G) os tibiale externum, (H) os vesalianum