The sciatic nerve, also called the ischiadic nerve, is a large
nerve
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the ...
in humans and other vertebrate animals which is the largest branch of the
sacral plexus and runs alongside the hip joint and down the
lower limb. It is the longest and widest single nerve in the
human body
The human body is the structure of a human being. It is composed of many different types of cells that together create tissues and subsequently organ systems. They ensure homeostasis and the viability of the human body.
It comprises a hea ...
, going from the top of the leg to the foot on the posterior aspect. The sciatic nerve has no cutaneous branches for the thigh. This nerve provides the connection to the nervous system for the skin of the lateral leg and the whole foot, the muscles of the back of the thigh, and those of the leg and foot. It is derived from
spinal nerves
L4 to
S3. It contains
fibers
Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...
from both the anterior and posterior divisions of the
lumbosacral plexus.
Structure
In humans, the sciatic nerve is formed from the L4 to S3 segments of the sacral plexus, a collection of nerve fibres that emerge from the
sacral part of the
spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...
. The lumbosacral trunk from the L4 and L5 roots descends between the sacral promontory and ala and the S1 to S3 roots emerge from the ventral sacral foramina. These nerve roots unite to form a single nerve in front of the
piriformis muscle. The nerve passes beneath
piriformis and through the
greater sciatic foramen, quitting the
pelvis
The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton).
The ...
.
From here, it travels down the posterior thigh to the
popliteal fossa. The nerve travels in the
posterior compartment of the thigh behind (superficial to) the
adductor magnus muscle, and is itself in front of (deep to) the long head of the
biceps femoris muscle. At the popliteal fossa, the nerve divides into its two branches:
* The
tibial nerve, which travels down the
posterior compartment of the leg into the foot
* The
common fibular nerve (also called the
common peroneal nerve), which travels down the
anterior and
lateral compartments of the leg into the foot
The sciatic nerve is the largest nerve in the human body.
Development
Function
The sciatic nerve supplies sensation to the
skin
Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
Other animal coverings, such as the arthropod exoskeleton, have different ...
of the
foot
The foot ( : feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg mad ...
, as well as the entire lower leg (except for its inner side). Sensation to skin to the sole of the foot is provided by the
tibial nerve, and the lower leg and upper surface of the foot via the
common fibular nerve.
The sciatic nerve also innervates muscles. In particular:
* Via the
tibial nerve, the muscles in the
posterior compartment of the leg and sole of the foot (plantar aspect).
* Via the
common fibular nerve, the muscles in the
anterior and
lateral compartments of the leg.
Clinical significance
Sciatica
Pain caused by a compression or irritation of the sciatic nerve by a problem in the lower back is called
sciatica. Common causes of sciatica include the following lower back and hip conditions:
spinal disc herniation,
degenerative disc disease,
lumbar spinal stenosis,
spondylolisthesis, and
piriformis syndrome. Other acute causes of sciatica include
coughing, muscular
hypertension
Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high b ...
, and
sneezing
A sneeze (also known as sternutation) is a semi-autonomous, convulsive expulsion of air from the lungs through the nose and mouth, usually caused by foreign particles irritating the nasal mucosa. A sneeze expels air forcibly from the mouth an ...
.
Injury
Sciatic nerve injury occurs between 0.5% and 2.0% of the time during a
hip replacement
Hip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant, that is, a hip prosthesis. Hip replacement surgery can be performed as a total replacement or a hemi (half) replacement. Such joint replacement o ...
.
Sciatic nerve palsy is a complication of total hip arthroplasty with an incidence of 0.2% to 2.8% of the time, or with an incidence of 1.7% to 7.6% following revision. Following the procedure, in rare cases, a screw, broken piece of trochanteric wire, fragment of
methyl methacrylate bone cement, or of a
Burch-Schneider antiprofusio cage can impinge on the nerve; this can cause sciatic nerve
palsy Palsy is a medical term which refers to various types of paralysisDan Agin, ''More Than Genes: What Science Can Tell Us About Toxic Chemicals, Development, and the Risk to Our Children;; (2009), p. 172. or paresis, often accompanied by weakness a ...
which may resolve after the fragment is removed and the nerve freed. The nerve can be surrounded in oxidized regenerated cellulose to prevent further scarring. Sciatic nerve palsy can also result from severe
spinal stenosis following the procedure, which can be addressed by
spinal decompression
Spinal decompression is the relief of pressure on the spinal cord or on one or more compressed nerve roots passing through or exiting the spinal column. Decompression of the spinal neural elements is a key component in treating spinal radiculopath ...
surgery.
It is unclear if
inversion therapy
Inversion therapy, or simply inversion, is the process of seeking therapeutic benefits from hanging by the legs, ankles, or feet in an inverted angle or entirely upside down. It is a form of spinal traction. Spinal Traction can be useful for eff ...
is able to decompress the sacral vertebrae; it may only work on the lumbar aspects of the sciatic nerves.
Sciatic nerve injury may also occur from improperly performed injections into the buttock, and may result in sensory loss.
Other disease
Bernese periacetabular
osteotomy resulted in major nerve deficits in the sciatic or femoral nerves in 2.1% of 1760 patients, of whom approximately half experienced complete recovery within a mean of 5.5 months.
Sciatic nerve exploration can be done by
endoscopy
An endoscopy is a procedure used in medicine to look inside the body. The endoscopy procedure uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are inse ...
in a
minimally invasive procedure to assess lesions of the nerve. Endoscopic treatment for sciatic nerve entrapment has been investigated in
deep gluteal syndrome. Patients were treated with sciatic nerve decompression by
resection of fibrovascular scar bands,
piriformis tendon release,
obturator internus, or
quadratus femoris or by
hamstring tendon scarring.
Anesthetic
Signals from the sciatic nerve and its branches can be blocked, in order to interrupt transmission of
pain signal from the innervation area, by performing a
regional nerve blockade
Nerve block or regional nerve blockade is any deliberate interruption of signals traveling along a nerve, often for the purpose of pain relief. Local anesthetic nerve block (sometimes referred to as simply "nerve block") is a short-term block, u ...
called a
sciatic nerve block.
Society and culture
According to
Jewish law
''Halakha'' (; he, הֲלָכָה, ), also transliterated as ''halacha'', ''halakhah'', and ''halocho'' ( ), is the collective body of Jewish religious laws which is derived from the written and Oral Torah. Halakha is based on biblical comman ...
, the sciatic nerve (
Hebrew
Hebrew (; ; ) is a Northwest Semitic language of the Afroasiatic language family. Historically, it is one of the spoken languages of the Israelites and their longest-surviving descendants, the Jews and Samaritans. It was largely preserved ...
:
Gid hanasheh
''Gid Hanasheh'' ( he, גִּיד הַנָּשֶׁה ''Gīḏ hanNāše'', literally "forgotten sinew", often translated as "displaced tendon") is the term for sciatic nerve in Judaism. It may not be eaten by Jews according to Halacha (Jewish Law ...
) may not be eaten by Jews, to commemorate
Jacob
Jacob (; ; ar, يَعْقُوب, Yaʿqūb; gr, Ἰακώβ, Iakṓb), later given the name Israel, is regarded as a patriarch of the Israelites and is an important figure in Abrahamic religions, such as Judaism, Christianity, and Islam. ...
's injury in his struggle with an
angel
In various theistic religious traditions an angel is a supernatural spiritual being who serves God.
Abrahamic religions often depict angels as benevolent celestial intermediaries between God (or Heaven) and humanity. Other roles ...
.
Additional images
File:Sciatic nerve1.jpg, Sciatic nerve.
File:Gray344.png, Structures surrounding left hip-joint.
File:Gray832.png, Nerves of the right lower extremity. Posterior view.
File:Slide4i.JPG, Sciatic nerve.
File:Slide8z.JPG, Sciatic nerve.
File:Slide4hh.JPG, Sciatic nerve.
See also
*
Lesser sciatic notch
*
Greater sciatic notch
Notes
References
External links
*
*
* ()
* ()
Sciatica and the Sciatic Nerve
{{Authority control
Nerves of the lower limb and lower torso