Sciatica is one of the most common low back injuries seen in chiropractic offices. Sciatica presents as low back, buttock, and leg pain that can be accompanied by numbness, tingling, or burning pain. It is typically one sided but can involve both legs at once. True sciatica can have many causes but the most common result from muscular and skeletal problems in the low back and buttock. Chiropractic care offers fast, natural relief from the pain without the use of harmful prescription drugs and surgery. Tight muscles and spasms can cause the spine to misalign and put pressure on the sciatic nerve. The most common treatment for sciatica is to begin at home with ice and rest. The ice should be applied to the lower back on the side of the leg pain in intervals of 15-20 minutes with about 30 minutes between applications. If the pain does not go away within 3-4 days it is recommended that you go to see a health care professional. Further studies including x-rays, MRI's, or nerve conduction velocity testing may be required in some cases. Once it is determined that there is no serious injury or organic cause for the injury chiropractic is a natural, cost-effective form of treatment that can provide lasting relief from the back and leg pain. Chiropractic treatment usually begins with ice therapy and may include electric muscle stimulation in order to reduce swelling and muscle tension. Specific stretching is then used to loosen the muscles of the back and remove pressure from the sciatic nerve. Using gentle chiropractic adjustments, the chiropractor then realigns the spine in order to remove further tension from the nerve and allow healing and recovery. Then specific stretches and exercises are provided to the patient to be done at home along with icing in order to keep the back looses and strengthen any weak parts. In order to fully understand sciatica I will now discuss in detail the involved structures and the medical explanation behind the mechanism of injury.
In most cases the sciatic nerve is being affected by a number of structures within the lower back and pelvic region. The sciatic nerve is the largest nerve in the body measuring 2 cm across at its origin and is formed from the sacral plexus by the ventral rami of L4-S3. It leaves the pelvis through the greater sciatic foramen, travels beneath the anterior portion of the piriformis muscle, passes behind the sacrospinal ligament, and then descends along the posterior aspect of the thigh behind the quadratus femoris muscle to supply the skin of the posterior and lateral portion of the leg and foot as well as motor to the muscles of the posterior thigh, leg, and foot. The sciatic nerve has two main divisions: The tibial nerve and the common peroneal (fibular) nerve. The tibial nerve descends through the popliteal fossa and divides at the flexor retinaculum into the medial and lateral plantar nerves. Its main function is to supply motor innervation to the posterior muscles of the knee joint and leg. The common peroneal nerve descends with the medial aspect of the biceps femoris, and passes over the posterior aspect of the fibular head where it divides into the superficial (lateral compartment of the leg), and deep (anterior compartment) peroneal nerves. The relationship between the sciatic nerve and the piriformis muscle is very important, especially in this case. Normally the sciatic nerve passes inferior to the piriformis muscle as it leaves the inferior portion of the greater sciatic foramen, but in an estimated 12.2% of the population it divides before it enters the gluteal region and the common peroneal division passes directly through the piriformis muscle. In 0.5% of the population it divides early and the common peroneal division crosses the piriformis superiorly. The piriformis muscle itself helps to stabilize the femoral head in the acetabulum and externally rotates the extended thigh and abducts the flexed thigh. It travels from the anterior surface of the sacrum and sacrotuberous ligament to the superior portion of the greater trochanter of the femur. It is innervated by branches of the ventral rami of S1 and S2 and receives no innervation from the sciatic nerve.
Sciatica is defined as sharp pain in the leg along the course of the sciatic nerve caused by irritation, compression, or trauma to the sciatic nerve or its roots. Many factors can lead to the irritation of the sciatic nerve, resulting in low back and leg pain. Mechanical aspects of nerve compression play a large role in sciatica cases. The sciatic nerve can be slowly compressed and deformed from factors such as the multiple disc bulges, disc herniations, degenerative changes such as discogenic spondylosis, facet arthrosis, stenosis, and osteophytosis, and then peripherally at the piriformis muscle. When compression occurs either centrally or peripherally it impairs neural function due to compromise of the vascular supply. When it comes to any nerve compression in the body, the first structures to be compressed are within the venous system causing blood stasis. Venous stasis leads to capillary stasis which then changes the microcirculation to the nervous tissue. This decrease in neural tissue perfusion causes hypoxia or a decrease in oxygen. Without sufficient levels of oxygen the cells can no longer produce the energy rich molecule ATP via oxidative phosphorylation. Without ATP, important Na+/K+ pumps within the neural membrane can no longer maintain the needed ionic gradient across the membrane. This results in the leakage of Na+ into the cell and alteration of the resting membrane potential (RMP) of the nerve. Normally this RMP is -70 mV. During normal depolarization, the threshold for nerve firing is around -55 mV. Once the ionic charge within the nerve reaches this threshold the nerve will fire. The leakage of Na+ into the cell brings the RMP near threshold. This results in a hypersensitized nerve that needs very little input to fire. This is the cause of the associated numbness and paraesthesia in the areas of the sciatic nerve. Pain is also perceived much easier in this state. If the pressure on the nerve is not relieved, chronic hypoperfusion and hypoxia will result in neural death. In cases which involve arthritis, the patient may have advanced osteoarthritic changes throughout the lumbar spine. In the early phases of degenerative joint disease dehydration of the intervertebral disc causes thinning and approximation of bony structures. Damage often begins within the inner portion of the disc which as no innervation and thus goes undetected. As time goes on and compressive forces deform the inner nucleus, shearing and rotational forces cause tears and weakening of annular fibers. The annulus of the disc is highly innervated by the sinuvertebral nerve and can cause a great deal of diffuse low back pain. This weakening can cause disc bulging and herniation into the extradural space and can put compressive and chemical forces into neural structures including the cord and the nerve roots of the sciatic nerve. This will manifest as sharp pain along the nerve route and cause antalgia. If the inner disc materials fully protrude out in later stages of disease it can cause increasing pain and tenderness. This is due to the water attractive properties of glycosamino glycans once out of the contained space of the disc. This hydrophilic swelling will place more pressure on the neural structures. As disc degeneration continues and the bony structures of the vertebral column come in contact with one another, a reflex hypertrophy takes place to protect the surfaces. This is seen in subchondral sclerosis of the vertebral bodies often resulting in space occupying osteophytes protruding into the neural canal. Apophyseal joint arthrosis occurs at the posterior aspect of the neural canals and in Irene's case, hypertrophy of the ligamentum flavum occurs. Together, all these degenerative changes produce stenosis in the canal and place extradural compressive forces on the nerve roots of the sciatic nerve. Stenosis can result in one or two sided sciatica. If centralized, bilateral leg pain is more common.
As the sciatic nerve leaves the greater sciatic foramen it can also be compressed as it transverses the piriformis muscle in the gluteal region. Sciatica cases such as these are referred to as piriformis syndrome sciatica, which is very common. Spasm or hypertonicity of the piriformis will compress the sciatic nerve. These peripheral nerve entrapment syndromes usually occur as the nerve passes beneath or through muscles or fibrous tissues. These nerve compression symptoms usually develop gradually with pain and paraesthesia being the most common complaints. Weakness can be seen later in chronic settings although in cases of older individuals this may be hard to detect. These are just a few of the most common causes of sciatica but any severe case should be evaluated by a health care professional if symptoms remain the same or worsen after initial ice and rest routines.
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