How is bone age measured?

Generally, bone age can be assessed using methods such as wrist X-ray examination, knee joint X-ray examination, ultrasound bone age assessment, computed tomography (CT), and magnetic resonance imaging (MRI). The specific details are as follows:

1. Wrist X-ray Examination: A posteroanterior (PA) view is generally used during imaging to clearly visualize the morphology and structure of the wrist bones. The wrist contains multiple ossification centers at different developmental stages. By observing characteristics such as the appearance and fusion timing of these ossification centers and the morphology of the bones, and comparing them with standard bone age atlases, the bone age can be determined.

2. Knee Joint X-ray Examination: The subject lies flat on the examination table with the knee extended, and X-ray images of the knee joint are taken, usually including both anteroposterior (AP) and lateral views. The epiphyseal growth plate of the knee is a key area for bone growth. During development, the morphology, size of the epiphysis, and the degree of fusion between the epiphysis and diaphysis continuously change. By comparing these features on the knee X-ray images with normal developmental standards, the bone age can be estimated.

3. Ultrasound Bone Age Assessment: Using an ultrasound bone age device, the probe is placed on the skin of the subject's wrist or other target area. Ultrasound waves travel at different speeds through tissues of varying densities. Bone tissue has a higher density than surrounding soft tissues, and the reflection characteristics of ultrasound signals at the bone surface and within the bone can reflect the bone structure and developmental status, thereby estimating the bone age.

4. Computed Tomography (CT): The subject lies flat on the examination table, and the scanning range is adjusted according to the area to be examined. CT can clearly display the internal structure of bones, such as the epiphysis, medullary cavity, and trabeculae. With three-dimensional reconstruction technology, the bone morphology can also be observed from different angles. By comparing these images with standard reference images of normal bone age, the bone age can be accurately determined.

5. Magnetic Resonance Imaging (MRI): The subject lies on the examination table with the target area positioned at the center of the magnetic field. MRI provides high-resolution images of both soft tissues and bones, clearly showing detailed structures such as the epiphyseal cartilage and growth plates. By observing developmental indicators such as the thickness of epiphyseal cartilage and the integrity of the growth plate, and combining these findings with MRI-based bone age evaluation criteria, the bone age can be determined.

Interpretation of bone age results should be made in conjunction with the individual's specific clinical context; conclusions should not be drawn based on a single measurement alone.