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Spine

Spinal stability and motion segment

Functional spinal unit, motion segment mechanics and clinical concepts of spinal stability

12 questions 2 source pages

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12 questions
Q1What is the White and Panjabi model of spinal stability?▸
  • Active - muscle
  • Passive - osteoligamentous
  • Neural; the three subsystems interact to maintain stability
  • Described by White and Panjabi 1987
Q2What is the White and Panjabi (1987) definition of spinal stability?▸
  • The spine's ability under physiologic loads to maintain its patterns of displacement
  • So as to avoid initial or additional neurologic deficits
  • Incapacitating deformity
  • And intractable pain
Q3What are the neutral zone and elastic zone of the spine?▸
  • Load-displacement is nonlinear due to viscoelastic properties; two zones
  • Neutral zone: maintained by active and neural subsystems; flexible with greater displacement under low loads
  • Elastic zone: maintained by passive subsystem; stiffer with decreased slope of curve
  • After injury (e.g. fracture), neutral zone decreases and passive zone increases, but passive zone exhausts quickly
Q4What is a functional spinal unit?▸
  • Small physiological unit of the spine
  • Exhibits biomechanical properties similar to the entire spine excluding muscle
Q5What is the functional spinal unit (motion segment)?▸
  • Smallest physiological motion unit of the spine
  • Two adjacent vertebrae + intervertebral disc + all ligaments between them
  • Excludes muscles
  • The three joint complex is called the articular triad
Q6List the ligaments of the functional spinal unit and their cranial continuations.▸
  • ALL - continuation of anterior atlanto-occipital membrane
  • PLL - continuation of tectorial membrane
  • Ligamentum flavum - continuation of posterior atlanto-occipital membrane
  • Facet capsules, inter- and supraspinous, intertransverse ligaments
Q7What forms the cruciform ligament and what is its function?▸
  • Transverse atlantoaxial ligament + superior and inferior fibres
  • Limits flexion and extension while allowing rotation
Q8What is the function of the alar ligament?▸
  • Runs from dens tip to occipital condyles
  • Limits flexion, rotation and lateral flexion
Q9What is the role of muscles in Panjabi's theory of stability?▸
  • Confer stability in the elastic zone
  • Anterior C spine: SCM, scalene, longus coli
  • Anterior TLS: abdominal muscles, psoas, quadratus lumborum
  • Deep intrinsic: semispinalis (not lumbar), multifidus, rotators, short rotators
Q10What are the ligaments specific to the C0-2 region?▸
  • Anterior atlantoaxial membrane
  • Tectorial membrane
  • Posterior atlantoaxial membrane
Q11Describe the posterior spinal muscles by layer.▸
  • Extrinsic (thoracic): trapezius, serratus posterior superior and inferior (ICN), latissimus dorsi
  • Intrinsic superficial (cervical): splenius capitis/cervicis, semispinalis capitis
  • Intermediate (whole spine): spinalis, erector spinae = longissimus + iliocostalis
  • Deep (whole spine): semispinalis (not in lumbar), multifidus, rotators, short rotators
  • Deepest: interspinalis, intertransversalis
Q12What muscle plane does the Wiltze approach use?▸
  • The plane between multifidus and longissimus
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