The thoracic spine has 12 vertebrae that connect the ribs to the sternum. It allows for limited movement like extension, flexion, and axial rotation coupled with lateral bending. The anatomy includes facets for rib articulation, transverse processes, and kyphotic curvature. Key biomechanics are pump handle and bucket handle movements of the ribs that influence breathing. Pathologies include scoliosis causing a rib hump and kyphosis causing a rounded back. The pedicles are oriented posterolaterally and are important anchors for instrumentation.

1. Biomechanics and anatomy
of thoracic spine
Dr N.Vagic

2.  Knowledge of the essential anatomy and
biomechanics of the thoracic spine is needed to
avoid or minimize surgical complications.

3. Thoracic spine
 12 vertebrae
 Upper T1-T4
 Middle T5-T9
 Lower T10-T12
 Largest segment of the spine
 Kyphosis

4. Pump handle movement
 This occurs mostly in the
vertebrosternal ribs ( 2nd to
6th). In this way AP diameter
of the thorax is increased
along with the up & down
movement of the 2nd to 6th
ribs , the body of the
sternum also moves up &
down .

5. BUCKET HANDLE MOVEMENT
 The middle of the shaft of
the rib lies at a lower level
than the plane passing
through the two ends .
Therefore , during elevation
of the rib the shaft also
moves outwards. This causes
increase in transverse
diameter of the thorax. Such
movements occur in
vertebrochondral ribs ( 7th to
10th) & are called bucket
handle movements.

6. Cervical Lordosis
Thoracic Kyphosis
Lumbar Lordosis

7. Spinal Column Structure
 Base of support.
 Link between upper and lower extremities.
 Protects spinal cord.
 Stability vs. mobility
 Example: cervical vs. thoracic spine

8. Thoracic Spine Function
 Articulation for the ribs
 Connected with sternum
 Thoracic cage
 Least mobility
 Increasing load bearing

9. Identification
 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 12th)
are atypical.

10. Body
 Equal transverse and anteroposterior diameters.
 On each side - two costal facets
 Superior costal facet articulates with the head of the numerically
corresponding rib.
 Inferior costal facet articulates with the next lower rib.

11.  Transverse processes – costotubercle facets
 Spinosus process- inferiorly
 Spinosus process of T11 and T12 - horizontally
 Vertebral foramen-Comparatively small and
circular

12. Posterior Anatomical structures
 Pedicles- are directed straight backwards. They
are teardrop or kidney shaped.
 Laminae- they are short thick and broad.
 Superior facet are thin and flat and face
posterior and slightly superolaterally
 Inferior facets face anterior and slightly
superomedially

13. ATYPICAL THORACIC
VERTEBRA
 1st , 9th , 10th , 11th & 12th are atypical vertebrae
1st thoracic vertebra- body cervical in type
9th and 10th thoracic vertebra – inferior costal
facet missing. It has only superior costal facet

14.  11th thoracic vertebra – superior costal facet,
transverse process does not have facet
 12th thoracic vertebra – superior costal facet ,
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. Largest articularis processus
and it is transit vertebra

15. Intervertebral Foramina
 Exit for nerve root.
 The size is dictated by the
disc heights and the pedicle
shape.
 Will lose space with
osteophytic formation,
hypertrophy of ligaments and
loss of disc height with aging
– lateral stenosis.
 Decreases by 20% with
extension and increases 24%
with flexion

16. ATTACHMENTS ON THORACIC
VERTEBRA

17. Longitudinal Ligaments
Anterior longitudinal
Supraspinous
Posterior longitudinal
Ligamentum flavum (elastic)

18. Intervertebral Disc
 20-30% of the height of the column and
thickness varies from 3mm in cervical region,
5mm in thoracic region to 9 mm in the
lumbar region.
 Ratio between the vertebral body height and
the disk height will dictate the mobility
between the vertebra –
 Highest ratio in cervical region allows for
motion
 Lowest ratio in thoracic region limits motion

19. Disc Structure
 80-90% is H2O – decreases with age.
 Disc volume will reduce 20% daily (reversible)
which causes a loss of 15-25 mm of height in the
spinal column.
 Acts as a hydrostatic unit allowing for uniform
distribution of pressure throughout the disc.

20. Osteokinematics
 The thoracic region is less flexible and more
stable due to limitations by the rib cage,
spinosus process, joint capsules, and the
dimensions of the vertebral bodies.
 The various movements allowed are
extension
flexion
lateral flexion
axial rotation (with the movement of the
corresponding ribs and the sternum)

22. During extension
 Vertebra approximated
posteriorly and disc
expands anteriorly
with nucleus pulposus.
 Anterior longitudinal
lig. is stretched while
posterior long. Lig. ,
lig. Flava&
interspinuos lig are
relaxed.

24. During flexion
 The interspace between
two vertebra open out
posteriorly and nucleus is
displaced posteriorly.
 Flexion is limited by
interspinous lig, PLL
lig. Flava.
 Anterior long. Lig. Is
relaxed.

25. During lateral flexion
On the contralateral side
 Thorax is elevated
 Intercostal spaces widen
On the ipsilateral side
 Thorax cage is lowered
 Intercostal spaces narrowed

26. Arthokinematics
 Facet orientation in the upper thoracic spine is
in the frontal plane. Thus allowing a coupling
movement - lateral flexion along with axial
rotation
 Orientation of the facets in the lower thoracic
spine is more in the sagital plane thus allowing
more of flexion and extension

27. Spinal canal
 Narrow
 Spinal cord in danger
 Blood supply of the spinal cord is provided by the
medullary or radicular arteries.
 Feeder artery for the lower thoracic spinal cord is
the greater medullary artery or Adamkiewicz artery,
which originates from lower intercostal or upper
lumbar artery between T10-T12. Spinal cord
ischemia may occur as a result of injury of the
greater medullary artery by fractures, disk herniation
or surgical procedures.

29. Pathomechanics
1. Scoliosis
2. Kyphosis

30. Scoliosis
 A lateral curvature of the
spine which exceeds by
10 degrees from the
normal is termed as
scoliosis.
 Types :-
1. Structural
2. Non structural

31. Thoracic Spine
 Scoliosis will cause a
rib hump.
 Combination of
tranverse plane rotation
and frontal plane
sidebend – contralateral
coupling.
 Convex side will occur
on the ipsilateral
rotated side – causing
hump.

32. Signs of scoliosis

33. Kyphosis
 Is the exaggeration of the
posterior spinal curve
 Is generally localised to
the dorsal spine
 Back is rounded
 Head is carried forward

34. Changes with age
With ageing, the costal cartilages ossify and allow
less movement and as the ligaments and joint
capsules stiffen, the thoracic spine loses
mobility.
The thoracic vertebrae commonly become
anteriorly wedge-shaped, as the result of
postural issues or osteoporotic vertebral
collapse. This contributes to an increasingly
kyphotic spine.

35. Pedicles
 Strongest structures
 Ideal anchor for screw insertion.
 Technically difficult.

36. Thoracic pedicles
 Greater superoinferior diameter and smaller mediolateral
diameter.
 The pedicles are oriented from posterolateral to
anteromedial direction.
 The medial inclination of the pedicle decreases from T1 to
T12.
 Projection point of the pedicle axis lies medial to the
lateral edge of the superior facet and superior to the
midline of the transverse process. and the screw should be
oriented 90 digress according to entering point
 The superior and inferior facets arise from the upper and
lower part of the pedicle of the thoracic vertebrae.

44. Thank you