Thoracic Spine Biomechanics

Question 1

spine morphology

Answer 1

• t1 and t12 are “transitional” vertebrae. T1 starts to look like thoracic, T12 has thoracic and lumbar components
• vertebral bodies larger than cervical
• demifacets present-articulation with ribs at posterolateral vertebral plateuas
• no uncinate processes present b/c ribs restrict
• longer SP than cervical with inferior angulation
• large TPs lateral and posterior (not protecting vertebral artery anymore)
• thickened TP laterally for articulation with costal tubercle
• facet articulations:
• -inferior facet of superior vertebra face inferior and anterior
• -superior facet of inferior vertebra face superior and posterior
• -60deg from horizontal plane-decreased WB occurs on facet joints compared to c-spine (compared to 45deg in c-spine)
• -means increased shear force in T-spine, decreased compression

Question 2

spine morphology: vertebral body

Answer 2

-vertical, oblique, and horizontal trabecular system in spongy bone
zone of weakness:decreased trabecular system evident
–can lead to compression fracture anteriorly
–thoracic spine most susceptible
-can increase with age

Question 3

spine morphology: vertebral arch

Answer 3

`-TP’s and SP’s sites for muscle and ligament attachements

• trabecular system evident, orientated compressive/shear force resister anteriorly, progressing predominately to horizontal plane alignment for shear forces posteriorly
• pars interarticularis

Question 4

fractures of the pars

Answer 4

• spondylolysis: collar seen, but no separation

- spondylolisthesis: collar with separation of vertebrae

Question 5

thoracic ROM

Answer 5

• ribs restrict ROM
• Upper thoracic: relative increased rotation and SB available like cervical (c. spine still better) (t1-t4/t5) 60 deg facets, looking slightly cervical
• lower thoracic: like lumbar spine for flexion and extension ROM is best: T9-T12
• middle thoracic: a little bit of upper and lower characteristics
• progression from T1-T12 SB increases due to increased rib separation

Question 6

fryettes laws

Answer 6

• upper thoracic spine: SB and rotation occur in same direction in neutral and non-neutral mechanics (like typical cervical, type 2)
• lower thoracic spine- SB and rotation occur in opposite direction in NEUTRAL mechanics (like lumbar, type 1)
• -also obey type 2 in non-neutral positions (flexed, rotate right/left)

Question 7

thoracic kinematics

Answer 7

• SB increases distally in the thoracic spine secondary to rib separation
• rotation decreases distally in thoracic spine (facet orientation, fryettes laws)
• ex: lower thoracic rotation from neutral, note tipping/tilting of the SP toward the concavity of spine (frontal plane) or concavity of ribs (sagittal plane)-clinical dysfunction
• -pt stuck in side bent/rotation opposite
• -sp is out of alignment, rotated opposite side too much
• ex: upper thoracic rotation from neutral not tipping/tilting of the SP toward the concavity of spine (frontal plane) or convexity of ribs (rib hump, viewed in sagittal plane)

Question 8

law 1

Answer 8

type 1 dysfunction

Question 9

law 2

Answer 9

type 2 dysfunction

Question 10

osteokinematics and arthrokinematics

Answer 10

• generally more mobile than lumbar but less than cervical
• flexion: sup and ant
• extension: inf and post
• rotation: sup/ant on L, post/inf on R for right rotation
• side bending/lateral flexion: same as rotation

Question 11

osteokinematic ROM thoracic

Answer 11

extension: 20-25
flexion: 30-40
rotation: 30
side bending: 25

Question 12

rule of threes

Answer 12

-refers to orientation of SP and Tp of a given vertebra
-groups segments in 3s
-T1-T3: sps are level with their respective TPs
-T4-T6: sps are 1/2 level inf to their tps (ex=T4 sp is 1/2 between the Tp of T4 and T5)
-T7-T9: sps are 1 full level inf to their TP (ex: T7 sp is at level of T8 vertebra
T10: sp is a whole segment below
T11: sp is 1/2 segment below
T12: sp is level with Tps