Age Determination by Radiology

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©Dr. Rajneesh Kumar Sharma MD (Hom)

Introduction

Abstract

From the moment of birth until the time one has grown up, bones go through a set a characteristic changes. Therefore the skeletal maturity, or bone age, can be estimated from radiographs of specific bones in the human body. Children who grow exceptionally slow or fast are often examined by making a radiograph of their left hand and wrist. This all is due to a variety of internal and external factors. Extracellular substance and bone cells get old and characteristic structural remodeling occurs with age. These age-related changes are important in the discrimination between pathological and physiological changes during old age. About 20% of the bone mass is lost between the fourth and the ninth decades, osteoblasts function less efficiently, and gradual loss of bone substance is enhanced by delayed mineralization of an increased surface area of thin and relatively less active osteoid seams. After the fifth decade, osteoclasia and the number of Howship’s lacunae increase and, with age, the number of large osteolytic osteocytes increases as the number of small osteocytes declines and empty osteocyte lacunae become more common. The result is greater liability to fracture and diminished healing or replacement of injured bone.

Bone maturation

In the fetus, bone is formed in two ways, either from condensed mesenchymal tissue to form intramembranous bone, or from endochondral bone by the indirect conversion of an intermediate cartilage model. Intramembranous ossification occurs in the bones of the cranial vault, i.e. the frontal bones and parietal bones, and in parts of the occipital bones and temporal bones, the mandible and maxilla. Endochondral bone formation takes place at the base of the skull, and the vertebral column, pelvis and the bones of the extremities, although mesenchymal bone formation can also be seen in these locations. Bone formation occurs in ossification centres that are usually located centrally within the mesenchymal tissue or in the cartilaginous model. Secondary ossification centres appear later and are located at the end of the cartilage models within the epiphysis and the apophysis. In tubular bone ossification proceeds towards the ends of the bones, where it beomces better delineated and appears as a plate of cellular activity. This plate is located between the epiphysis (secondary ossification centre) and the diaphysis forming the growth plate ( physis) that later becomes the site of longitudinal growth of the bone. The ossification centres of the epiphysis and the ossification centres of the small bones of the wrist appear at different ages.

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