How to find the second lumbar vertebra

There are five lumbar vertebrae in the human body. Lumbar disc herniation mostly occurs at L1 to L2 and L3 to L4, which are the most common places for it to occur clinically. But how do you determine which lumbar vertebra has the problem? In fact, our anterior superior iliac spine is level with the fourth lumbar vertebra, and two touches upwards is the second lumbar vertebra, which is very easy to find. This article introduces the structural characteristics of the lumbar vertebrae. Let’s take a look.

There are 5 lumbar vertebrae, the vertebral bodies are tall, higher in the front and lower in the back, and are kidney-shaped. The vertebral foramen is large and triangular in shape, larger than that of the thoracic vertebrae and smaller than that of the cervical vertebrae. In the sagittal plane, the articular surface of the superior articular process is concave and faces posteriorly and medially, while the articular surface of the inferior articular process is convex and faces anterolaterally. There is a mastoid process on the outside of the upper joint, and the spinous process is a square bone plate that protrudes horizontally backward. The transverse process is short and thin, extending posteriorly and laterally. There is a small nodule on the posterior and inferior side of the root, called the accessory process. During the development process, the transverse process is homologous to the rib, and the accessory process should be the true transverse process. The transverse processes of the 1st to 3rd lumbar vertebrae gradually grow longer, with the 3rd lumbar vertebra being the longest, and those of the 4th and 5th lumbar vertebrae gradually becoming shorter. The vertebral body of the 5th lumbar vertebra is particularly large, and the front of the vertebral body is particularly high. When the 5th lumbar vertebra connects with the sacrum, it forms a promontory that convexes forward.

The vertebral structure characteristics of the lumbar vertebrae:

1. Cross-sectional scan of cortical bone The cortical bone forms a shell structure surrounding the cancellous bone, with an average thickness of about 1.5 to 3.5 mm. It is divided into three types according to its thickness and bone characteristics: a. The horseshoe-shaped part at the front edge and both sides of the vertebral body, whose shape and cortical bone thickness are relatively regular, with a CT value range of 400 to 500; b. The pedicle area refers to the lateral and posterior walls of the vertebral body connected to the pedicle. The thickness of the cortical bone in this area gradually increases from the vertebral body to the pedicle, and is thickest at the connection to the pedicle. CT value range: 500-800; c. Interpedicular area: the posterior wall of the vertebral body between the pedicles. The cortical bone thickness is the thinnest among the three parts, and is even absent in the middle of the vertebral body, corresponding to the venous sinus of the posterior wall of the vertebral body. CT value range: 200-400.

2. Cross-sectional scan of cancellous bone Compared with cortical bone, cancellous bone is highly heterogeneous, with CT values ​​ranging from tens to over 250. Take the middle part of the vertebral body as an example: the bone in the part slightly behind the center of the vertebral body is relatively dense, the bone in the surrounding part is relatively sparse, and the part near the pedicle is in between. The cancellous bone under the cortical bone in the front part of the vertebral body is the lowest; the cancellous bone near the upper and lower lumbar endplates is denser than the middle part of the vertebral body on average, and the lower part is slightly higher than the upper part.

Under normal circumstances, the first lumbar vertebra, the second lumbar vertebra, and the fifth lumbar vertebra cannot be directly identified. It is necessary to count along the spinous processes through the surface landmarks of the third lumbar vertebra and the fourth lumbar vertebra. The surface mark of the third lumbar vertebra is at the same level as the rib margin in the lower chest. Counting one vertebra upwards, it is the second lumbar vertebra. The fourth lumbar vertebra is at the midpoint of the line connecting the two iliac bones. Counting two vertebrae upwards, it is the second lumbar vertebra. Lumbar spine radiography can be performed if necessary. More clearly the condition of the vertebral body.

To find the exact location of the spine, you need the help of bony landmarks on the body surface. It will be easier to find it based on the location of the bony landmarks on the body surface. The intersection of the line connecting the highest points of the left and right iliac crests and the posterior midline is at the level of the fourth lumbar vertebra. You can find it first, and then count two vertebrae upwards to find it. Stand upright with your hands hanging down. The midpoint of the horizontal line of the lower angles of the two shoulder blades and the line connecting the highest points of the left and right iliac crests is at the level of the twelfth thoracic vertebra. Count two vertebrae down and you will find it.