Low back pain is a type of pain that human beings encounter in any period of life and can be caused by different anatomical structures.
Knowing the shape of the pain and the anatomical structure from which it originates is essential for the treatment to be accurate and effective. Although the most common causes are those originating from the spine, it can also be caused by muscle and fascia, extraperitoneal and intraperitoneal diseases. Therefore, all these anatomical structures create different types of painful clinical pictures
Pain in the lumbar region can occur for 4 different reasons.
1-Local pain: Bone and ligament structures surrounding the spinal cord and muscles may cause pain. Except for the ligamentum flavum, all surrounding tissues are sensitive to pain. These pains are almost always seen in the affected segment. However, it can spread to the paravertebral tissues by decreasing its density. This is due to 3 reasons.
a) Bone-induced pain: It occurs especially in intraosseous tumors that stretch the periosteum, infections or fractures after trauma.
b) Discogenic pain: Unextruded disc hernias cause pain by stretching the annulus. Here, pain arises as a result of irritation of the recurrent nerve (ramus meningicus). This irritation may originate from both the posterior annulus, the posterior longitudinal ligament, and the dura.
c) Myofascial pain: Tensions at the attachment points of the muscles to the fascia cause pain.
2-Radicular Pain: It is pain due to radix irritation. It is usually seen in disc herniations. The most common examples are sciatica. In the involvement of the thoracic radix, chest and abdominal pains occur in the form of belts. Radicular pain does not spread to the distal dermatomes as it is thought, but remains in the proximal dermatomes of a radix. For example, sciatica does not usually go all the way to the toes.
3-Pain due to sympathetic irritation: There is a continuous and diffusely spreading pain here. Vasomotor-trophic changes also occur. This is how pain is seen in causalgia, reflex sympathetic dystrophy.
4-Neurogenic pain: It is the pain that occurs with partial or complete damage to the sensory parts of the peripheral or central nervous system. It is common in spinal cord injuries. It usually occurs months after spinal cord symptoms. Diabetic mononeuropathy and herpes zoster pain are neurogenic pain. In reality, this pain is deafferentation pain. It is a diffuse and burning pain. It is always accompanied by loss of sensation.
In order to better understand the pain in the lumbar region and to make accurate decisions in diagnosis and treatment, it is necessary to know the topographic anatomy of the region very well.
If we consider the anatomical structures in the lumbar region
VERTEBRA
Especially the most important structure of this region that causes pain; The lumbar vertebral column consists of 5 vertebrae.
Each vertebra consists of the vertebral body called the corpus anteriorly and the arcus in which the neural elements are located posteriorly. The part of the arcus vertebra between the transverse process and the corpus is called the pedicle, and the part between the transverse process and the spinous process is called the lamina. The superior and inferior articular processes, where the facet joints are located, are located at the junction of the pedicle and lamina. The spinous processes at the posterior middle junction of the right and left laminae can be palpated through the skin. The protrusions extending from the pedicle and lamina junction point to the sides are called transverse processes.
There are endplates formed by cartilaginous tissue on the upper and lower surfaces of the corpus. In newborns, endplates are cartilaginous. These cartilage plates ossify over time and merge with the bone vertebra at the age of 16-20 years. After puberty, when ossification is complete, the middle and posterior parts of the plate remain cartilaginous. . The cartilaginous structure on the lower and upper surfaces of the discs and the end plates are tightly adhered to each other. The anterior part of the vertebral body is the weakest region. Therefore, most of the fractures are located here.
Intervertebral foramina are windows that open outwards between the pedicle above and below, the intervertebral disc and vertebral body anteriorly, and the lamina and anterior aspect of the facet joint posteriorly. The lateral recess is the canal in which the spinal root travels before reaching the intervertebral foramen. The pedicle forms the outer edge of the canal, the superior articular process and ligamentum flavum the posterior edge, the vertebral body and the intervertebral disc form the anterior margin
Since the medulla spinalis ends at the L1 level, the spinal roots of the lumbar region are inside the spinal canal before traversing the vertebral column through the related intervertebral foramen. they go a long way from top to bottom. Before entering the relevant foramen, the root traverses the upper disc and proceeds downward. Thus, compression of the intervertebral foramen, where the nerve roots leave the vertebral column, by the upper disc is related to this path followed by the spinal root in the spinal canal. The root entering the intervertebral foramen in a vertical position is in close contact with the upper edge of the foramen. The arachnoid surrounding the spinal root follows the spinal root up to the sensory ganglion in the intervertebral foramen. The dura covering the spinal root along the entire foramen is then continuous with the perineurium covering the spinal nerve.
Although the spinal root is highly flexible against stretching, the dura mater is highly resistant and this causes pain. Spinal roots are more mobile than is thought. Depending on the movements of the lumbar region, the length of the spinal roots changes. The sensory root forming the spinal nerve is twice as thick as the motor root. The motor root is located on the lower anterior surface of the intervertebral foramen. The spinal nerve occupies 35-40% of the intervertebral foramen, and the remaining space is filled by the supporting tissue, ligamentum flavum, artery, vein, lymphatics, and sinuvertebral nerve.
FACEET JOINTS
Facet joints are the joints located posterolaterally to the lumbar spinal canal and posterior to the intervertebral foramen. facet joints; It has joint capsule, articular cartilage, and rudimentary meninges. The upper surface of the joint faces downward, anteriorly, laterally and has a convex surface. The lower face is concave and faces medially from bottom to back.
The medial side of the joint capsule is formed by fibers of the ligamentum flavum, while the lateral capsule is formed by true fibrous tissue. In the joint, which has two recesses, superior and inferior, the superior recessus may herniate the spinal nerve, especially in the foramen. Those in the upper lumbar region are in the sagittal plane, and those in the lumbosacral region are more coronal than the others. Thus, there is an anatomical structure that allows limited lateral flexion in the lumbosacral region. Total movement in the lumbosacral region is considered as flexion and extension in the sagittal plane. In accordance with this structure, the combination of these two movements creates an additional load on the intervertebral discs in the lumbosacral region.
Facet joints have two main movements: translation (sliding) and distraction (opening). There is slippage on both sides in anterior flexion and on one side in lateral flexion. If there is an opening on one side and compression on the other, the resulting movement is rotation. In the dorsal region, the facet joints are located at an angle of 60 degrees with the horizontal plane, allowing lateral flexion rotation movements to be made from this region. In lumbar flexion, the separation of the facet joint surfaces from each other allows some lateral flexion and rotation movement from this region.
It has restraining effects on the facet joints, especially on rotation and hyperflexion movements. It has been observed that the facet joint surfaces in rotation and the facet joint capsule in flexion create significant resistance in the direction of restraining these movements.
INTERVERTEBRAL DISCS
33% of the entire lumbar column height is made up of discs. The discs in this region have the largest surface in proportion to the weight they carry. The ratio of disc thickness to vertebral body thickness is very important in mobility. As this ratio increases, the mobility of the segment increases. In the lumbar region, this ratio is 1/3, more than in the thoracic region and less than in the cervical region. Intervertebral discs are composed of nucleus pulposus in the middle, annulus fibrosus surrounding it, and cartilaginous lamellae that are in close relationship with the vertebral endplates above and below the disc. These lamellae located on the upper and lower surfaces of the annulus fibrosus; They are firmly attached to the epiphyseal ring at the periphery and to the cartilaginous endplate in the centre. Sharpney fibers, located at the outermost part of the annulus fibrosus, tightly attached to the vertebral cortex, in close relationship with the anterior and posterior longitudinal ligaments, are called Sharpney fibers
ANULUS FIBROSUS:
Annulus fibrosus fibrosis concentric surrounding the nucleus pulposus It has a fibroelastic network structure composed of lamellae. It carries 75% of the force on the disc. The reason why it is much more flexible than tendons and other ligaments; The arrangement and content of the fibers forming its structure is due to the high amount of proteoglycan. The fibers forming the concentric lamellae; They form an angle of 30 degrees with the disc surface and are arranged in opposite directions in the two adjacent layers. This arrangement allows the two vertebrae to roll (rocker-like) on each other, while restricting the shearing movement. Although the annulus fibrosus mainly has a collagen structure, it contains a very high rate of water, such as 65-70%. 50-55% of its dry weight is composed of collagen fibers, while the rest is composed of proteoglycans and glycoproteins such as keratin sulfate, chondroitin sulfate. while the side is thicker and more prominent, the back side is thinner.
NUCLEUS PULPOSUS:
The nucleus pulposus in the middle is a viscous liquid consistency and consists of loose, delicate thin collagen fibers embedded in the gelatinous matrix. The nucleus pulposus is not located in the middle of the annulus fibrosus, but is located close to the posterior 1/3 of it. It contains 40-50% of the disk space. The fibers contained in the nucleus are scattered in the center and arranged in an oblique manner at the periphery in the gelatinous matrix, and this arrangement is thought to have an important role in the function of the nucleus. The amount of water contained in the nucleus pulposus is higher than that of the annulus fibrosus, and while it is 88% in young ages, this amount decreases to 65% in advanced ages. The collagen it contains is type II and constitutes only 20-30% of its dry weight. Proteoglycans (chondroitin 6 and 4 sulfate, keratin sulfate) and hyaluronic acid are other substances found in the nucleus. . Their rates change with age and joint degeneration.
The intervertebral disc contains cartilaginous lamellae that are tightly attached to the vertebral endplates above and below.
Most of the compression force is carried by the posterior annulus in the erect posture, and by the anterior annulus in the flexion posture. Under high pressure, fluid escapes from the disc to the endplates, while under low pressure the proteoglycans in the disc draw fluid from the environment. This fluid exchange is more in lumbar flexion. Under load, while the annulus loses 11% of the fluid it contains and the nucleus 8%, with the increase in the concentration of water-retaining electrolytes such as Na and K, the disc can resist the pressure by holding the remaining fluid, even if it is under pressure for a long time. As soon as the pressure is removed, the disc reabsorbs the lost fluid. The nucleus has the ability to absorb 8 times the water it contains.
LUMBAR REGION LIGAMENTS
The lumbar region has two very strong ligaments located anterior and posterior to the vertebral corpuscles.
The anterior longitudinal ligament is a very durable and wide ligament that covers the anterior surface of the vertebral corpuscles and is in close relationship with the annulus fibrosus fibers. The anterior longitudinal ligament has a restrictive function in lumbar extension.
It prevents excessive extension of the lumbar region and thus prevents the expansion of the anterior intervertebral disc space, narrowing the posterior intervertebral disc space, and thus prevents the overlapping of the facet joint surfaces in this region. This picture emerges in cases where the lumbar lordosis is increased due to the lumbosacral angle. In particular, the shortness of the iliopsoas muscle and the insufficient strength of the hip extensors or abdominal muscles cause the upward rotation of the pelvis, in other words, the posterior pelvic tilt to be incomplete, which means an increase in lumbar lordosis. It is the most important ligament that plays a role in the stabilization of the lumbar region.
The posterior longitudinal ligament, on the other hand, is a ligament that covers the posterior surface of the vertebral bodies and adheres very tightly to them and shows an angulation to both sides to join with the annulus fibrosus fibers at the intervertebral disc levels. showing an angulation means that the support it gives to the disc from behind decreases. This is one of the most important anatomical causes of disc herniations. One of the roles played by this ligament in the occurrence of disc herniation is that its width decreases gradually from the L1 level and this width decreases to half at the L5-S1 level.
The lateral ligament, on the other hand, is another ligament located between the anterior and posterior longitudinal ligaments and tightly attached to the intervertebral discs, and has a restrictive effect on lateral flexions.
The ligamentum flavum is a very flexible ligament located between the laminae behind the spinal canal and extending laterally to the intervertebral foramen. This flexibility is due to the high amount of elastin it contains. The ligament adhering to the lower anterior surface of the upper lamina and the upper posterior surface of the lower lamina thus creates a highly flexible wall that protects the neural structures on the posterior surface of the spinal canal.
It is in close relationship with the interspinous ligament fibers in the middle. This ligament, which forms a wide spectrum towards the sides, supports the facet joint from below and acts as a joint capsule on the anterior surface of this joint. It has a restraining effect on lumbar hyperflexion and plays a helpful role in returning to normal posture due to its elastic structure. However, rather than this function of the ligament, it has been stated that it protects the neural structures here by creating a soft environment on the posterior surface of the spinal canal in all lumbar region movements.
The intertransverse ligaments located between the transverse processes and the supraspinatus ligaments, which progress by covering the interspinous and spinous processes extending between the spinous processes, work together and create an important resistance against the shearing force, especially in this region.
In particular, the tension created by the supraspinatus ligament is very important in reducing the shear force on the vertebrae. While coming from lumbar flexion to extension, anatomical structures up to the last 45 degrees are protected by taut ligaments. However, the early emergence of lumbar lordosis causes the loss of ligament support on these structures, and therefore, longer-term operation of the extensor muscles.
BLOOD CIRCULATION OF THE LUMBAR REGION
The nutrition of this region is directly from the aorta. Four pairs of lumbar arteries originating from the back of the aorta supply the first four vertebrae, and the fifth pair coming from the middle sacral artery supply the fifth lumbar vertebra. The sacrum is supplied by the superior medial and hypogastric arteries. These arteries originating from the posterior sacral foramen are also responsible for supplying the distal lumbar region muscles.
The venous system without valves empties the blood it receives into the inferior vena cava. There are quite common anastomoses between the internal and external anterior and posterior venous circulation. The absence of the valve system causes the venous circulation between the pelvis and the lumbosacral region to be in a very close relationship, which facilitates metastases from the pelvic region to the lumbosacral region.
The disc fed directly through blood vessels at birth, is removed from the cartilaginous endplates by the occlusion of these vessels towards the third decade. It is fed by diffusion. Lumbar flexion movement is very important in the nutrition of intervertebral discs.
MUSCLES OF THE LUMBAR REGION
Lumbodorsal fascia covering the muscles of this region; They are attached to the ribs above, to the sacrum below, laterally to the fascia of the latissimus dorsi and transversus abdominis muscles, and to the spinous processes in the middle.
1-Extensors:
-There are erector spina muscles showing a multisegmental array under the fascia. These muscles are tightly attached to the sacrum, iliac bone, lumbar spinous process and supraspinous ligament. They form three main columns in the lumbar region.
The outermost iliocostalis (lateral band), the middle longissimus (middle band), the innermost spinalis (medial band). The task of these muscles is to bring the lumbar region to extension and lateral flexion.
-Transverse spina muscles are located under the erector spina muscles
2-Flexors: rectus abdominalis, transversus abdominalis, internal and external abdominal oblique muscles.
3-Lateral flexors: Quadratus lumborum is the internal and external abdominal oblique muscles.
4-Rotators. Internal and external abdominal oblique muscles.
INNERVATION OF THE LUMBAR REGION
The posterior primary rami, which is formed by the division of the spinal nerve, is divided into two as medial and lateral.
. The medial branch is responsible for the innervation of the facet joints. Each facet joint is innervated by two adjacent medial branches. The paraspinal muscles are provided by the medial branch, and the skin innervation is provided by the lateral branch. The multifidus, intertransversalis, interspinous muscles, interspinous ligament, ligamentum flavum, spinous processes, lamina and lumbodorsal fascia are innervated by the posterior primary rami.
Significant sensory innervation of the lumbar spine is provided by the sinuvertebral nerve (Luschka’s recurrent nerve). The sinuvertebral nerve branches off from the spinal nerve before it divides into anterior and posterior divisions. The nerve entering the spinal canal through the intervertebral canal by incorporating the sympathetic fibers from the sympathetic ganglion in the relevant segment; It divides into descending, ascending and transverse branches around the pedicle and posterior longitudinal ligament. Each nerve branch has extensive anastomosis with opposing symmetrical branches. The posterior longitudinal ligament, posterior outer fibers of the annulus fibrosus, anterior dura mater, posterior vertebral periosteum, and lateral recesses are innervated by the sinuvertebral nerve.
Nerve endings associated with the posterior longitudinal ligament were detected in the posterior annulus fibrosus, but no nerve endings were found in other parts of the disc. . The source of the pain is the annulus and is carried by this very rich paravertebral sympathetic chain
The nucleus pulposus and annulus do not have nerve endings in the nucleus and inner part.
