Lumbar spine and pelvis

• Functions of the lumbar spine

  • Attachment point for muscles
  • Consist of 5 vertebrae in lower back to provide support for weight of body
  • Surrounds and protects the spinal cord
  • Allows for a wide range of body motions

  
• Movements available at the lumbar spine

  • Flexion-extension
  • Lateral inflexions
  • Rotations

  
• Structures that limit the movements of the lumbar spine

  • Iliolumbar ligament – stability of lumbosacral junction – restricts side flexion and rotational movement at L5-S1 joint
  • Orientation of facet joints limits rotation

  
• Characteristics of a typical lumbar vertebra (L1-L4)

  • Large vertebral body
  • Vertebral arch
  • Seven processes
  • Spinous process is short and thick and projects perpendicular from the body
  • Articular facets vertical, superior facets directed posteromedially and medially. Also have a curved articular surface
  • Mammillary process on posterior aspect of the superior articular process

  
• Characteristics of the atypical lumbar vertebra (L5)

  • Has the largest body and transverse processes of all vertebrae
  • Anterior aspect of the body has a greater height compared to the posterior. Creates the lumbosacral angle between the lumbar region of the vertebrae and the sacrum

  
• The shape of the individual vertebrae contributes to the normal curve of the lumbar spine

  
• Anterior superior iliac spine

  Bony protuberance located at the junction of the superior margin (iliac crest) and the anterior margin of the ilium

  
• Posterior superior iliac spine

  Bony prominence that indicates the posterior end of the iliac crest. Located where the superior border (iliac crest) meets the posterior border of the ilium

  
• Iliac crest

  Curved part at the top of the hip. Forms the wing-like part of the pelvis which people rest their hands on

  
• Characteristics of the facet/apophyseal joints in the lumbar spine

  • Synovial plane joint
  • Formed by two adjacent vertebrae with the inferior facet of the superior vertebra meeting the superior facet of the inferior vertebra
  • Articular surfaces of the corresponding lumbar articular processes differ. The superior ones are vertical and concave, being oriented posteromedially in the coronal plane. The inferior ones are vertically convex and face anterolaterally
  • Surrounded by a thin and loose fibrous joint capsule which is lines by a synovial membrane that secretes viscous synovial fluid, which acts as lubricant
  • Ligaments: Ligamenta flava, Interspinous, Supraspinous, Intertransverse
  • Physiological movements: Forward flexion and extension in the lumbar spine

  
• Characteristics of the intervertebral joints

  • Classification: fused, fibrocartilaginous symphysis
  • Connect directly adjacent vertebrae of the vertebral column
  • Ligaments: anterior and posterior longitudinal, ligamenta flava, interspinous, supraspinous, intertransverse
  • Joint capsule: not enclosed in joint capsule, stability provided by anterior and posterior longitudinal ligaments
  • Physiological movements: flexion, extension, lateral flexion and axial rotation of the vertebral column

  
• Contents of the intervertebral foramen

  • Spinal nerve root, dorsal root ganglion, recurrent meningeal (sinuvertebral) nerve, segmental spinal arteries, intervertebral veins, transforaminal ligaments, fat

  
• Functions of the pelvis

  • Transfer of weight from the upper axial skeleton to the lower appendicular components of the skeleton, especially during movement
  • Provides attachment for a number of muscles and ligaments used in locomotion
  • Contains and protects the abdominopelvic and pelvic viscera

  
• Pubic symphysis

  Between the pubis bodies of the two hip bones. Secondary cartilaginous joint composed of fibrocartilage interpubic disc. Limited movement but important for cushioning the stress related to walking and running. During pregnancy, hormones cause structural changes to increase its width and mobility to prepare pelvis for childbirth

  
• Sacroiliac joint

  Between the ilium and the hip bones, and the sacrum. Synovial joint. Bears weight of the axial skeleton and transfer it to hip bones. Sacroiliac joints connect hip bones posterolaterally, pubic symphysis connects hip bones anteriorly
• Movements that occur in the pelvic region

  • Anterior pelvic tilt (sitting up, arched back, bum out)
  • Posterior pelvic tilt (slouching, lumbar lordosis, core muscles in)
  • Lateral pelvic tilting (bum shuffling, one hip at a time)

  
• Functions of the lumbar region

  • Surrounds and protects spinal cord from injury
  • Accepts and distributes load
  • Produces and accumulates movements of force
  • Serves as an attachment point for muscles

  
• Components of the neural control unit for spinal stability

  • Evaluating stability and coordinating and response
  • Spinal muscles: an active subsystem that provides dynamic stability
  • Spinal column: a passive subsystem that provides intrinsic stability
• Differences between lumbar and thoracic vertebrae

  • Shape and size of neural canal
  • Shape and size of vertebral body
  • Presence/absence of rib 'demifacets'
  • Shape, length, and angle of spinous process
  • Orientation of facet joint surfaces

  
• Contents of the spinal cord

  • 31 pairs of spinal nerves: 5 in lumbar region, 5 in sacral region, 1 in coccygeal region
  • The lumbar (and cervical) regions are enlarged to accommodate nerve plexi
  • Nerve roots exit via intervertebral foramina

  
• Cauda equina

  The spinal cord is shorter than the spinal column, ending level with the L1/L2 vertebrae. Nerve roots below L1/L2 are elongated to accommodate this. Compression of the cauda equina can be a medical emergency

  
• Components of the pelvis

  • Innominate bone: ilium, ischium, pubis
  • Sacrum: sacral foramina
  • Sacroiliac joints: interaction between innominate and sacrum
• Functions of the pelvis

  • Supports and protects the viscera
  • Support bodyweight transmitted through vertebrae
  • Is a significant attachment point for lumbar musculature and ligaments

  
• Muscles involved in lumbar spine movements

  • Extension: iliocostalis thoracis, longissimus thoracic, iliocostalis lumborum, spinalis thoracis
  • Forward flexion: rectus abdominis
  • Lateral flexion: interspinalis, quadratus lumborum

  
• Additional lumbar musculature

  • semispinalis cervicis, semispinalis thoracis, multifidus, internal oblique, external oblique, linea alba, inguinal ligament, latissimus dorsi, transverse abdominis