Vertebrae
Your spine is made up of 24 small bones, called vertebrae. The vertebrae protect and support the spinal cord. They also bear the majority of the weight put upon your spine. Vertebrae, like all bones, have an outer shell, called cortical bone, which is hard and strong. The inside is made of a soft, spongy type of bone, called cancellous bone.
The vertebral body is the large, round portion of bone. Each vertebra is attached to a bony ring. When the vertebrae arestacked one on top of the other, the rings create a hollow tube for the spinal cord to pass through. Each vertebra is held to the others by groups of ligaments. Ligaments connect bones to bones; tendons connect muscles to bones. There are also tendons that fasten muscles to the vertebrae.
The bony ring attached to the vertebral body consists of several parts. The laminae extend from the body to cover the spinal canal, which is the hole in the center of the vertebra. The spinous process is the bony portion opposite the body of the vertebra. You feel this part if you run your hand down a person's back. There are two transverse processes (little bony bumps), where the back muscles attach to the vertebrae. The pedicle is a bony projection that connects the laminae to the vertebral body.
Between each vertebra is a soft, gel-like cushion, called an intervertebral disc. These flat, round "cushions" act like shock absorbers by helping absorb pressure. The discs prevent the bones from rubbing against each other.
Each disc has a strong outer ring of fibers called the annulus, and a soft, jelly-like center called the nucleus pulposus. The annulus is the strongest area of the disc. It helps keep the disc's center intact. The annulus is actually a strong ligament that connects each vertebra together.
The mushy nucleus of the disc serves as the main shock absorber. The nucleus is made up of tissue that is very moist because it has high water content. The water content is what helps the disc act like a shock absorber-somewhat like a waterbed mattress.
The spinal column has real joints (just like the knee, elbow, etc.) called facet joints. The facet joints link the vertebrae together and give them the flexibility to move against each other. The facets are the "bony knobs" that meet between each vertebra. There are two facet joints between each pair of vertebrae, one on each side. They extend and overlap each other to form a joint between the neighboring vertebra facet joint. The facet joints give the spine its flexibility.
The facet joints aresynovial joints, structures that allow movement between two bones. The ends of the bones that make up a synovial joint are covered with articular cartilage, a slick spongy material that allows the bones to glide against one another without much friction. Synovial fluid inside the joint keeps the joint surfaces lubricated, like oil lubricates the parts of a machine. This fluid is contained inside the joint by the joint capsule, a watertight sac of soft tissue and ligaments that fully surrounds and encloses the joint.
Neural Foraminae
The spinal cord branches off into 31 pairs of nerve roots, which exit the spine through small openings on each side of the vertebra called neural foraminae. The two nerve roots in each pair go in opposite directions when traveling through the foraminae. One goes out the left foramina; the other goes out through the right foramina. The nerve root allows nerve signals to travel to and from your brain to the rest of your body.
The spinal cord is a column of millions of nerve fibers that carries messages from your brain to the rest of your body. It extends from the brain to the area between the end of your first lumbar vertebra and top of your second lumbar vertebra. Each vertebra has a hole in the center, so when they stack on top of each other they form a hollow tube (spinal canal) that holds and protects the entire spinal cord and its nerve roots.
The spinal cord only goes down to the second lumbar vertebra. Below this level, the spinal canal contains a group of nerve fibers, called the caude equina. This group of nerves goes to the pelvis and lower limbs.
A protective membrane, called the dura mater covers the spinal cord. The dura mater forms a watertight sac around the spinal cord and the spinal nerves. Inside this sac, the spinal cord is surrounded by spinal fluid.
The nerve fibers in your spinal cord branch off to form pairs of nerve roots that travel through the small openings between your vertebrae. The nerves in each area of the spinal cord connect to specific parts of your body. This is why damage to the spinal cord can cause paralysis in certain areas and not others. It depends on which spinal nerves are affected. The nerves of the cervical spine go to the upper chest and arms. The nerves of the thoracic spine go to the chest and abdomen. The nerves of the lumbar spine reach to the legs, pelvis, bowel, and bladder. These nerves coordinate and control all the body's organs and parts, and allow you to control your muscles.
The nerves carry electrical signals back to the brain that allow you to feel sensations. If your body is being hurt in some way, your nerves signal the brain. Damage to the nerves themselves can cause pain, tingling, or numbness in the area where the nerve travels. Without nerve signals, your body would not be able to function.
The muscles next to the spine are called the paraspinal muscles. They support the spine and provide the motor for movement of the spine. Joints allow flexibility, and muscles allow mobility. There are many small muscles in the back. Each controls some part of the totalmovement between the vertebrae and the rest of the skeleton. These muscles can be directly injured, such as when you have a pulled muscle or muscle strain. They can also cause problems indirectly, such as when they are in spasm after injury to other parts of the spine.
A muscle spasm is experienced when your muscle tightens up and will not relax. Spasms usually occur as a reflex (meaning that you cannot control the contraction). When any part of the spine is injured-including a disc, ligament, bone, or muscle-the muscles automatically go into spasm to reduce the motion around the area. This mechanism is designed to protect the injured area.
Muscles that are in spasm produce too much lactic acid, a waste product from the chemical reaction inside muscle cells. When muscles contract, the small blood vessels traveling through the muscles are pinched off (like a tube pinched between your thumb and finger), which causes a build up of lactic acid. If the muscle cells cannot relax and too much lactic acid builds up, it causes a painful burning sensation. The muscle relaxes as the blood vessels open up, and the lactic acid is eventually washed away by fresh blood flowing into the muscle.
Doctors sometimes look at a spinal segment to understand and explain how the whole spine works. A spinal segment is made up of two vertebrae attached together by ligaments, with a soft disc separating them. The facet joints fit between the two vertebrae, allowing for movement, and the neural foraminae between the vertebrae allow space for the nerve roots to travel freely from the spinal cord to the body. The spinal segment allows physicians to examine the repeating parts of the spinal column to understand what can go wrong with the various parts of the spine.
Ankylosing Spondylitis
Ankylosing spondylitis is a rare condition that can cause back and neck pain. It is a rheumatic inflammatory disease that affects the spine and sacroiliac joints. It usually begins in the spine (usually the low back first), but this chronic and painful disease may also attack other joints, tendons and ligaments, and the chest wall.
Over time, this disease can cause the vertebral bodies in the spine to fuse together. When this happens, patients with ankylosing spondylitis will have difficulty moving freely. Common symptoms for ankylosing spondylitis are gradually occurring back pain and stiffness (usually over a period of weeks or months). Early morning stiffness is often helped with a warm shower or light exercise. Symptoms last longer than three months.
In particularly severe cases, patients may be unable to look above the level of the horizon, or they may develop a significant amount of pain from having a hunched over posture. Ankylosing spondylitis is usually diagnosed using x-rays of the sacroiliac joints, looking for changes in the tissues caused by inflammation. However, tissue changes are not always visible.
Infection/ Discitis
Discitis is a low-grade infection that affects the disc space between two vertebrae. Although discitis is uncommon, children under ten are usually the ones affected by this condition which is the result of an inflammation caused by staphylococcus, viruses, or other inflammatory processes. Discitis is characterized by the slow onset of severe back pain and may or may not be associated with fever, chills, sweats, feeling tired, loss of appetite or other symptoms. The diagnosis is usually made by seeing narrowing of the disc space between two vertebrae and a bone scan that shows that the disc and adjacent vertebra are "hot" on the scan. A MRI scan with contrast may also be helpful as long as lab tests which may include a CBC ( complete blood count with differential), CRP (C reactive Protein), and ESR (Sedimentation rate). This condition can be very painful and is often aggravated by any movement of the spine. The pain often travels to other parts of the body including the abdomen, hip, leg, or groin. It usually occurs in the lower (lumbar) back and upper (thoracic) back. This is a medical urgency, and should be addressed promptly.Young children with this condition are usually irritable and uncomfortable and refuse to sit up, stand or walk. The treatment of discitis generally involves antibiotics, rest, and a brace. Surgery is rarely needed.
Herniated / Ruptured Disc
The disks in your spine are your “shock absorbers” between the bones (vertebras). With forces too strong for the disk to support, such as, lifting an object that is too heavy or lifting it improperly, tears in the disk or a herniation of the disk may occur. A herniated disk is also called a bulging, protruding or “slipped” disk which may cause specific pain patterns from the back into the buttocks, hips, and/or legs. The ways in which a herniated disc causes different pain patterns and problems with your back is related to the location of the herniated disc along your spine, and also to the anatomy of your spinal column.
Osteoporosis
Osteoporosis is a disorder caused by a decrease in the amount of calcium in your bones, which can cause the bones in your spine to break because they are too weak to support the weight of the body. When this happens, people usually suffer from sharp back pain, and they often become shorter or have a "hunched over" posture. If you have these symptoms you could be suffering from osteoporosis.
Osteoporosis is a disease that affects more than eight million women and two million men. It's characterized by low bone mass and deterioration of bone tissue which can lead to fragile bones and increased risk in fractures of the spine, hip and wrist. More than 700,000 vertebral fractures every year are caused by osteoporosis.
Osteoporosis is some times called the "silent disease" because bone loss has no symptoms, and the disease usually remains painless until a bone breaks. Although the disease can affect any bone, spinal or vertebral compression fractures can have serious consequences including loss of height, severe back pain, and deformity, a curving of the shoulders and back, and a thickening waistline. Women in particular reach their maximum bone mass at about the age of 20. After that, they will gradually lose bone mass. In the 5-7 years immediately following menopause, women will lose up to 20% of their bone mass. When osteoporosis affects the spine, there is a gradual collapse of the vertebrae producing back pain, loss of overall height, and a stooped posture. The back pain at vertebral collapse may be severe at times.
Sciatica
Sciatica is the descriptive term for when pain runs from your back or buttocks down your leg and even into your foot. It is a condition caused by either compression or trauma of the sciatic nerve. Sciatica is made worse when you cough or if someone lifts your leg up while you are lying down. Symptoms may begin abruptly or gradually, are usually irritated by movement, and often grow worse at night. Sciatica implies that there is an irritation of your nerve root in the lower part of your spine. In some instances, this could be due to a ruptured or herniated disc in your lower back.
Spondylolisthesis
Early treatment usually involves rest and medication. Progressive spondylolisthesis may require surgical treatment.There are two common forms of Spondylolisthesis; isthmic and degenerative. Spondylolisthesis occurs when there is a weakening of the pars interarticularis. The condition may also be caused by degenerative disc disease. When the vertebra slips forward, it may press on nerves, and surgery may become necessary. Spondylolisthesis may also be caused by degenerative conditions that affect the vertebral facet joints.
Spondylolysis
Spondylolysis is a defect in the lamina of the vertebrae in the pars interarticularis, usually the fourth or the fifth lumbar vertebrae in the lower (lumbar) spine. Spondylolysis may occur as a congenital defect or be the result of repetitive trauma. Some physicians believe spondylolysis may be caused by genetics, and that someone could be born with thin vertebral bones causing them to be vulnerable to the condition. Spondylolysis is common in teenage gymnasts and football players, and presents with lower back pain that is worse with strenuous exercise or activity. Radiographic findings are subtle, but bone scans, MRI scans, or CT scans will usually detect the lesion. Activity modification, bracing, injections or surgical treatment may be indicated for persistent symptoms.
Sprains & Strains
Most acute pain in the back results from sustaining a mild strain in the back or back musculature. Sprains and strains in your lower back usually happen during a sudden and stressful injury, causing stretching or tearing of the muscles, tendons, or ligaments in your lower back. When you strain or sprain your lower back it causes a lot of stress on your spine, irritating it. If you have this condition you may also suffer from painful muscle spasms which can occur during your daily activities or at night while you're sleeping. The pain is usually limited to five or ten days.
Stenosis
Lumbar stenosis is a natural product of aging, and the wear and tear on the spine throughout our lives. As our bodies grow older, the ligaments and bones that make up the spine grow thicker and become stiffer. The spinal canal gradually narrows, and the spinal cord is slowly compressed. The lack of space interferes with the normal function of the spinal cord and the body becomes less able to function normally.Stenosis produces a dull, aching pain in the lower back when standing or walking. The pain usually radiates down into the buttocks and thighs, and can be relieved by sitting, or by using a walker or a shopping cart in the grocery store. These symptoms usually slowly get worse over time, and people who suffer from spinal stenosis will notice a slow decrease in their ability to walk shorter and shorter distances.
Trauma/Spinal Cord Injuries
It is impossible to predict how badly someone's spine has been injured before a doctor has evaluated them. Therefore, everyone who is involved in an accident that could have damaged their back is treated as if they do have an injury to their spine. Most people are familiar with the "backboards" that paramedics use to transport accident victims, but they are unaware of how important these devices are in keeping the spine stable while they are taken to the hospital.
Paramedics and emergency response teams treat accident victims according to strict protocols that have been developed in order to save lives. These protocols are designed to minimize the possibility that someone with a spine injury could be injured while moving him or her from the accident scene or while taking them to a hospital. With these protocols, cervical collars are placed on all accident victims. The patient is secured on a backboard, and then taken to a hospital for further evaluation.
Each year in the United States, there will be approximately 50,000 new spinal cord injuries caused by accidents. A spinal cord injury occurs when the cord itself is crushed, stretched, or torn by the accident.
Unfortunately, this is still an injury that cannot be reversed or cured by modern medicine. More than half of these injuries involve the cervical spine, and most of them happen to young men. These injuries are incredibly devastating to the patient, their families, and also to their communities.
Much research is being done on ways to minimize spine injuries by designing cars for better safety, improving protective gear like football helmets, and educating people about the dangers of certain activities. Other research is being done on improving immediate care after a spinal cord injury, and also in determining the most appropriate type of rehabilitation for each individual patient.
Tumors (Benign/Malignant)
Doctors use the term "benign" to indicate that a particular tumor is unlikely to spread to others parts of the body. Benign tumors can still be a significant problem however, depending upon their location, size, adjacent structures, blood supply, and other factors. Fortunately, most benign tumors can be treated successfully.Tumors of the spine and spinal cord are relatively uncommon. The most common initial symptom that patients with a spinal tumor have is pain. Because back pain is very common, it is also not a specific symptom of any one disease or medical condition. Spinal cord tumors can be either primary (originating in the spinal cord) or secondary (metastases of cancer that originated elsewhere in the body). Therefore, the challenge is to determine how to evaluate back pain with the goal of specifically excluding a tumor as the cause of the pain. Luckily, most back pain is not due to a tumor. However, if a cancer were discovered after a long period of "conservative" management of back pain, most patients would feel that their problem should have been investigated more thoroughly in the beginning.
Doctors use the term "malignant" to indicate that a particular tumor or a cancer often spreads to other parts of the body, and can be difficult to cure or treat. This is very different from "benign" cancers, which are much less likely to spread, are easier to treat and control.
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