Sacral ala - Winglike
anatomic process of the sacrum articulating with the ilium on
its lateral side by the sacro-iliac joint.
Sacral nerve stimulation - Electrical pulses sent to the sacral nerve by a
neurostimulator.
Sacral nerves - Nerves
located near the base of the spinal cord in the lower back. Sacral
nerves control the bladder, bowel and pelvic organs.
Sacral plexus - A
nerve plexus that lies against the posterior and lateral walls
of the pelvis. It is formed by the union of the lumbosacral trunk
and the first, second and third sacral nerves and continues into
the thigh as the sciatic nerve.
Sacral promontory - The inwardly projecting anterior part of the body
of the first sacral vertebra.
Sacrum - Curved
triangular bone at the base of the spine, consisting of five
fused vertebrae known as sacral vertebrae. The sacrum articulates
with the last lumbar vertebra and laterally with the pelvic bones.
Sagittal balance - Alignment of C7 to the posterior superior aspect
of the sacrum on an upright long cassette radiograph of the spine.
Scalloped - Having
curved projections at the border.
Sciatic nerve - Either
of the pair of largest nerves in the body that arise one on each
side from the sacral plexus and that pass out of the pelvis through
the greater sciatic foramen and down the back of the thigh to
its lower third where division into the tibial and common peroneal
nerves occur.
Sciatica - Pain
along the course of the sciatic nerve.
Scoliometer - a
proprietary name for an inclinometer used in measuring trunk
rotation.
Scoliosis - lateral
deviation of the normal vertical line of the spine which, when
measured by X-ray, is greater than ten degrees. Scoliosis consists
of a lateral curvature of the spine with rotation of the vertebrae
within the curve.
Spinal instrumentation - metal implants fixed to the spine to improve spinal
deformity while the fusion matures. This includes a wide variety
of rods, hooks, wires and screws used in various combinations.
Secure hemostatic seal - A closure to prevent blood leakage.
Segmental instability - Abnormal response to applied loads characterized
by motion in the motor segment beyond normal constraints.
Semilunar valves - The aortic and pulmonary valves within the human
heart are called semilunar valves because their leaflets have
a half-moon configuration.
Seroma - A
fluid-filled mass in a tissue or organ.
Shear stress - Intensity
of force parallel to the surface on which it acts.
Skeleton - The
rigid framework of bones that gives shape to the body and protects
inner organs.
Spina Bifida - Congenital
defect of the spine marked by a defective closure of the vertebral
arch. There are three types of Spina Bifida : the Spina Bifida
Occulta, the Meningocele and the Myelomeningocele.
Spina Bifida Occulta - When there is an opening in one or more of the
vertebrae of the spinal column without apparent damage to the
spinal cord.
Spinal canal - Body
channel that contains and helps protect the spinal cord and nerve
roots.
Spinal cord - Thick
longitudinal cord or nervous tissue that extends along the back
dorsal to the bodies of the vertebrae and is enclosed in the
spinal canal formed by their neural arches. Serves not only as
a pathway for nervous impulses to and from the brain but also
as a center for carrying out and coordinating many reflex actions
independently of the brain.
Spinal cord stimulation - Spinal cord stimulation uses a small neurostimulation
system that is surgically placed under the skin to send mild
electrical impulses to the spinal cord. The electrical impulses
are delivered through a lead (a special medical wire) that is
also surgically placed. These electrical impulses block the signal
of pain from reaching the brain.
Spinal fusion - Surgical
fusion of two or more vertebrae for remedial immobilization of
the spine.
Spinal instrumentatiion - Metal implants fixed to the spine to improve spinal
deformity while the fusion matures. This includes a wide variety
of rods, hooks, wires and screws used in various combinations.
Spinal stenosis - Degenerative
narrowing of the spinal canal, nerve roots canals and / or intervertebral
foramina caused by bone and / or ligaments hypertrophy in local,
segmental or generalized regions. This narrowing results in compression
of spinal nerves and nerve roots causing lower back pain, neurogenic
claudication and lower extremity pain.
Spine - The
flexible bone column extending from the base of the skull to
the tailbone. It is made up of bones, discs, ligaments and muscles.
The spine is also referred to as the vertebral column, spinal
column or backbone.
Spinous process - The
median spinelike or platelike dorsal process of the neural arch
of a vertebra.
Spondylitis - an
inflammatory disease of the spine.
Spondylolisthesis - an anterior displacement (either congenital or
due to a pars defect or traumatic or degenerative) of a vertebra
on the adjacent lower vertebra. It occurs in the lower part of
the lumbar spine, mostly in L4 or L5.
Spondylolysis - Inadequacy
or absence of ossification of the vertebral arch at the level
of the pars interarticularis. It is a rupture due to bone fatigue,
sometimes a malformation.
Spondylosis - Degenerative
disease of both the disc and the zygapophyseal joint.
Stable vertebrae - The most proximal thoracic or lumbar vertebra most
closely bisected by a vertically directed central sacral line
assuming the pelvis is level. In the sagittal plane, the vertical
line is drawn proximal from the posterior superior edge of S1.
Static load - A
load applied to a specimen is called static if it remains constant
with respect to time.
Stenosis - When
a passage does not fully open; a constriction or narrowing.
Stiffness - A
measure of resistance offered to external loads by a specimen
or structure as it deforms.
Strain - The
change in unit length or angle in a material subjected to load.
Stress - The
force per unit area of a structure and a measurement of the intensity
of load.
Structural curve - a segment of the spine that has fixed lateral curvature.
Subdural hematoma - A blood clot under the dura mater, the outermost
membrane surrounding the brain.
Subluxation - An
incomplete dislocation.
Supine - Lying
flat on the back with the face up.
Supraspinous ligament - It joins the tips of the spinous processes from
the seventh cervical vertebra to the sacrum.
Synovium - Thin
membrane surrounding a moveable joint.
