THORACIC SEGMENT

INTRODUCTION The section of the spine found in the upper back is called thethoracic spine. It goes from the base of the neck to the bottom of the rib cage.

Two common anatomic terms are useful as they relate to the thoracic spine. The termanterior refers to the front of the spine. The termposteriorrefers to the back of the spine. The front of the thoracic spine is therefore called theanterior thoracic

CURVETURE IN THE SPINE

Important Structures The important parts of the thoracic segments include:bones and joints ligaments nerves muscles spinal segment

General feature THORACIC VERTEBRAE The middle 12 vertebrae make up the thoracic spine. Thoracic vertebrae are larger than those in cervical region . T2 to T8 are quite uniform, and are considered as typical thoracic vertebrae. T9 to T12 are the transition vertebrae, and shows some similarities with lumbar vertebrae. Thoracic region can also be subdivided as upper (T1-T4), middle (T5-T8), and lower (T9T12) thoracic areas.

BONES THORACIC SEGMENT Beginning with 3rd vertebrae and moving down ,the bodies of these bones increase in size. This reflects the stress placed on them by the increasing amounts of body weights they bear

The thoracic vertebra identified by presence of costal facets on sides of the vertebral bodies. There are 12 thoracic vertebrae out of which the 2nd to 8th are typical and the remaining 5 (1st,9th,10th,11thand

IDETIFICATION

ATYPICAL1st , 9th , 10th , 11th & 12th are atypical vertebrae 1st thoracic vertebraBody resembles to cervical type. Complete costal facet spine thick,long and horizontal 9th thoracic vertebra inferior costal facet missing. It has only superior costal facet

11th thoracic vertebra costal facet complete, transverse process is small & does not have articular facet 12th thoracic vertebra costal facet complete , the shape of the body, pedicles, transverse processes & spine are similar to those of a lumbar vertebra. The transverse process is small and has no facet but has 3 tubercles .

TYPICAL VERTEBRAE T2 to T8 are quite uniform, and are considered as typical thoracic vertebrae. Feature:

BODY The body of the typical thoracic vertebra has equal transverse and anteroposterior diameters. On each side it bears two costal facets (demifacets). Superior costal facet articulates with the head of the numerically corresponding rib. Inferior costal facet articulates with the next lower rib. The vertebral bodies are wedge shaped with posterior height greater than ant. Height which produce normal kyphotic posture.

Posterior height of each vertebrae increased gradually downward.

Typical thoracic vertebrae Facet joints Costal facets Pedicles Lamina Transverse process Body Spinous process Vertebral foramen/canal Intervertebral foramen

Pedicles- are directed straight backwards. They are teardrop or kidney shaped. Laminae- they are short thick and broad. Zygapophyseal articular processes Superior Zygapophyseal facet are thin and flat and face posteriorly and slightly superolaterally Inferior zygapophyseal facets face anteriorly and slightly superomedially

ARCHES

ARCHES cont.. Transverse processes They have thickened ends that support paired large oval facets (costotubercle facets) .They are for articulation with the tubercles of rib Spinous process- They slope inferiorly The spinous process of T11 and T12 have a triangular shape and project horizontally. Vertebral foramen-Comparatively small and circular

BODY: Resist compressive load PEDICLE:Transfer bending force from post element to vertebral body. LAMINA:Tranmit the force from articular ,transverse ,spinous process to pedicles. TRANSVERSE PROCESS: muscle attachment& act as mech. Lever. SPINOUS PROCESS: muscles attachment& act as mech. Lever. VERT. FORAMEN: Protection for spinal cord.

SUMMARY

Intervertebral Disks Disk Composition Nucleus pulposus Annulus Fibrosus

a) Nucleus Pulposus :inner gelatinous core

b) Anulus fibrosus collagen fibers & fibrocartilage

Thoracic IVD are thinner than other regions . The ratio of disk size to vertebral body size smallest in the thoracic region. SO PROVIDE stability rather than mobility. THE IVD are also some what wedge shaped,the posterior height greater than the ant. height which contribute thoracic kyphosis.

FUNCTIONS: The thoracic IVD are primary restraints to movt. And considered the primary stabilizer of the mobile segment. ACT as shock absorbver. Transmit the wt from one vertebrae to other.

Topographical landmarks: Topographical landmarks: T2-T3: Jugular notch T4-T5: Sternal angle T7;Inferior angle of scapula T9-T10: Tip of xiphoid Umblical area

ARTICULATION OF THRORACIC SEGMENTS The articulation of thoracic segment are:---1.Interbody joints 2.Zygopophyseal or facet joints 3.Costovertebral joints 4.Costotransverse joints

INTERBODY JOINTSThe joins between the vertebral bodies are known as inter body joints. Function :flat vertebral surface allow all translation to occur. The IVD allows tipping of vertebral bodies.

FACET JOINT Each vertebra has two sets of facet joints. Type : Diarthrodial jts ARTICULATION superior articulating facet of a vertebrae articulate with inferior facet of adjacent vertebrae.

FACET JTS Cont The facet joints help to prevent excessive movement, such as hyperextension or hyperflexion. The joint capsule are more taut than cervical and lumber region which contrebute to less avaible ROM.

Joints between articular processes synovial plane joints permit Sliding Movements 2. Intervertebral Discinterposed between bodies

Costovertebral joint Type:--Synovial joint Aticular surface:1. Head of the rib (the small,oval & slightly convex demifacets of the ribs are called superior & inferior costovertebral facet) 2. Two adjacent vertebral bodies 3. Intervertebral bodies

Costovertebral joint Rib 2 to 9 have typical CV joints .The inferior and superior facet on the adjacent vertebrae articulate ,respectively with the superior & inferior facets on the head of the rib. The heads of 2nd to 9th ribs fit into the angle formed by the adjacent vertebral demifacets and the intervening disk & are numbered by the inferior vertebrae with which a rib articulate. The 1st ,10th ,11th & 12th ribs are atypical ribs are atypical ribs because they articulate with only one vertebral body& numbered by that body. The CV facets of T10 to T12 are located more posteriorly on the pedicle of the vertebrae.

LIGAMENTS ; 1.Intra articular lig. (divided into two cavities & extend from the crest of the head of the rib to annulus fib.of the IVD.)

2.Radiate ligament which located with in the capsule & attach to the ant.lat portion of the capsule.The radiate ligament has 3 bands : Superior band(attach to superior vertebrae) Intermediate band (attach to IVD) Inferior band (attach to inferior vertebrae

3.A fibrous capsule surrounds the entire articulation of each CV joint.

MOVEMENT CV JTS Both rotation and gliding motion occur at all CV jts. 1st ,10th to 12th are more mobile because the rib head articulates with only one vertebrae. The interosseous ligament is absent in these joints therefore they each have only one cavity .

COSTOTRANSEVERSE JOINT TYPESynovial jts. Articulation :The costal tubercle of the rib with a costal facet on the transverse process corseponding vertebrae.

There are ten pair of CT joint articulating vertebrae T1 to T10 with the same no. rib. The CT T1 to T6 have slightly concave costal facets on the transverse process of the vertebrae and slightly convex costal tubercles on the corresponding ribs .This allows slightly rotation movement .

At the T-7 to T-10, CT joints both articular surfaces are flat and gliding motion predominant. Rib 11 and 12 do not articulate with their respective transverse process of T11 or T12.

LIGAMENT OF CT Fibrous capsule Three ligaments are Lateral costotransverse ligament (it is short ,stout ,bend ;Located between the lateral portion of the costal tubercle and the tip of the corresponding transverse process),costotransverse ligament(it is composed of short fibers that run within costo transverse foramen between the neck of the rib posteriorly and the transverse process at the same level) and the superior costotransverse ligament(It runs from the crest of the neck of the rib to the inferior border of the cranial transverse process)

LIGAMENT ATTACH TO THORACIC VERTEBRAE

Ligament Name Anterior Longitudinal Ligament (ALL) A primary spine stabilizer

Description About one-inch wide, the ALL runs the entire length of the spine from the base of the skull to the sacrum. It connects the front (anterior) of the vertebral body to the front of the annulus fibrosis. About one-inch wide, the PLL runs the entire length of the spine from the base of the skull to sacrum. It connects the back (posterior) of the vertebral body to the back of the annulus fibrosis. This ligament attaches the tip of each spinous process to the other. This thin ligament attaches to another ligament, called the ligamentum flavum that runs deep into the spinal column. This yellow ligament is the strongest one. It runs from the base of the skull to the pelvis, in front of and behind the lamina, and protects the spinal cord and nerves. The ligamentum flavum also surrounds the facet joint capsules.

Posterior Longitudinal Ligament (PLL) A primary spine stabilizer

Supraspinous Ligament Interspinous Ligament

Ligament Flavum The strongest ligament

Adjacent vertebrae held tightly together (protect spinal cord) 1. ANTERIOR LONGITUDI NAL LIGAMENT Strong band joins bodies on anterior side

POSTERIOR LONGITUDINAL LIGAMENT- weaker, narrower band

LIGAMENTA FLAVA yellow elastic bands connecting laminae

1. ANTERIOR LONGITUDINAL LIGAMENT 2. POSTERIOR LONGITUDINA L LIGAMENT LIGAMENTA FLAVA -

4. INTERSPINOUS AND SUPRASPINOUS LIGAMENTS

SUPRASPINOUS

MUSCLE There are two major groups of muscles in the back. The extrinsic back muscles produce and control limb and respiratory movements. The intrinsic (deep) back muscles act on the vertebral column, maintaining posture and producing its movements

Extrinsic Back Muscles The extrinsic back muscles include superficial and intermediate muscles. The extrinsic back muscles include trapezius, latissimus dorsi, levator scapulae, and rhomboids

FUNCTION: The function of this muscle group is to connect the upper limbs to the trunk and produce and control limb movements.

Intrinsic Muscle The intrinsic back muscles (also called as deep back muscles, muscles of back proper) are act to maintain posture and control movements of the vertebral column, and innervated by the posterior rami of spinal nerves. The deep muscles of the back are separated from the overlying muscles by fascia.

The deep back muscles can be grouped into superficial, intermediate, and deep layers according to their proximity to the surface Superficial layer of intrinsic back muscles include splenius capitis and cervicis muscles.

Superficialis ms The splenii arise from the midline and extend superolaterally to the cervical vertebrae (splenius cervicis) and cranium (splenius capitis). The splenii cover and hold the deep neck muscles in position. The splenius capitis arises from the ligamentum nuchae and the spinous processes from C7 to T3 or T4 and attaches to the superior nuchal line and mastoid process of the skull. The splenius capitis arises from the spinous processes below the splenius capitis, usually T3 to T6.

Intermediate layer of intrinsic back muscles also known as erector spinae muscles and It include iliocostalis, longissimus and spinalis muscles. This group is the chief extensor of the vertebral column. These three muscles occupy the area between the spinous processes centrally and the angles of the ribs laterally.

They are ordered lateral to medial: the iliocostalis forms the lateral column, the longissimus forms the intermediate column, and the spinalis forms the medial column. Each column is divided regionally into three parts according to the superior attachments: iliocostalis is subdivided into the cervicis, thoracis and lumborum; the longissimus and spinalis are subdivided into the capitis, cervicis, and thoracic portions.

Deep layer of intrinsic back muscles also known as transversospinal muscle group, and include semispinalis, multifidus, and rotatores muscles

DEEP MUSCLEMuscular structures Multifidus

Between transverse and spinous processes

DEEP MUSCLEMuscular structures Longissimus

Between transverse process and thoracolumbar fascia

th o ra c ic .f lv

MovementFlexion Rectus Abdominis Obliques Extension Erector Spinae Quadratus lumborum Trapezius (lower)

ROTATION & LAT.FLEXION Oblique Psoas major Quadratus lumborum Multifidus Iliocastalis lumborum Iliocastalis thoracis Rotatores

Radicular artery which is a branch of posterior intercostal artery.

BLOOD SUPPLY

Spinal nerves The spinal nerves are numbered according to the vertebrae. 12 thoracic spinal nerves are T1 through T12

SPINAL DEFORMITIES A visible deformity of the spine may be present at birth, as a direct result of the deformity causing a bend in the spine, or it may become obvious as the child grows, the unbalanced forces which the anomaly exerts on the surrounding vertebrae causing

Types spinal deformity Of thoracic region are :Scoliosis: a side-to-side curving of the spine when viewed from behind Kyphosis: a forwards bending of the spine when viewed from the side. Potts disease

kyphosis Kyphosis is a progressive spinal disorder that can affect children or adults. This disorder may cause a deformity described as humpback or hunchback. Kyphosis can be in the form of hyperkyphosis or sharp angular gibbus deformity (see 'Gibbus Deformity' below). Abnormal kyphotic curves are more commonly found in the thoracic or thoracolumbar spine

kyphosisKyphosis is classified as either postural or structural. Postural means the kyphosis is attributed to poor posture, usually presenting a smooth curve, which can be corrected by the patient. Structural kyphosis is caused by an abnormality affecting the bones, intervertebral discs, nerves, ligaments, or muscles. Kyphosis with a structural pathology may require medical intervention because the patient alone cannot control curve progression.

SCOLIOSIS Scoliosis Scoliosis means abnormal curvature of the spine greater than 10 degrees, as measured on an X-ray. Anything less than 10 degrees is considered normal variation in a normal individual. The curvature takes place in three dimensions. n scoliosis, the spine appears S-shaped when looking at the front or back.

Pott's disease is named after Percival Pott (1714-1788), who was a surgeon in London. Pott's disease is tuberculosisof the spinal column

The usual sites to be involved are the lower thoracic and upper lumbar vertebrae. The source of infection is usually outside the spine. It is most often spread from the lungs via the blood. There is a combination ofosteomyelitisand infective arthritis. Usually more than one vertebra is involved. The area most affected is the anterior part of the vertebral body adjacent to the subchondral plate. Tuberculosis may spread from that area to adjacent intervertebral discs. In adults, disc disease is secondary to the spread of infection from the vertebral body but in children it can be a primary site, as the disc is vascular in children.

Children are sometimes born with vertebrae which are only partly formed, (hemivertebrae or wedge vertebrae ) or vertebrae which are fused together (block vertebrae). The so-called butterfly vertebra is actually two hemivertebrae which have occurred at the same level. Missing or extra vertebrae often associated with an extra pair of ribs if located in the thoracic region of the spine do not generally cause deformity or other

Vertebral anomalies

Scheuermann's disease is considered to be a a form of juvenileosteochondrosisof the spine. It is found mostly in teenagers and presents a significantly worse deformity than postural kyphosis. Patients suffering with Scheuermanns kyphosis cannot consciously correct their posture. The seventh and tenth thoracicvertebrae are most commonly affected. It causes backache and spinal curvature

Schuermann's disease describes a condition where thevertebrae grow unevenly with respect to theSagittal plane ; that is, theanterior angle is often greater than theposterior This uneven growth results the signature "wedging" shape of the vertebrae, causingkyphosis

Osteoporosis Osteoporosis is a disease process that causes bones to lose mineral density and become fragile or brittle. These brittle bones become very susceptible to fractures and may break with even very minor stresses. According to the National Osteoporosis Foundation, women are four times more likely to get osteoporosis than men. This condition causes progressive degeneration of the bones, but is generally painless in and of itself.

Osteoarthritis Osteoarthritis is a progressive wear-and-tear form of arthritis. According to the American Academy of Orthopedic Surgeons, it affects the cartilaginous covering of bones in the joints, causing them to wear out quickly. Symptoms of osteoarthritis include pain, stiffness and a grinding sound with movement. Again, because of the relatively small amount of movement in the thoracic spine, osteoarthritis is not as common here as in the cervical and lumbar spine.

Radiculopathy, sometimes called radiculitis refers to any disease of the nerve root and usually involves inflammation. Compression fractureis usually an osteoporatic condition and may or may not involve trauma.