Chapter 18
Basic Science Issues Which Relate to the Lumbar Spine
Anatomy: The Static Unit

  1. The functional demands of the spine (fundamental issue of evaluation):
    1. stability for support and load-bearing
    2. mobility in 3 dimensions
    3. protection of neuro-vascular elements

  2. The normal spine: curves, transitional zones
    1. typical vertebrae
    2. atypical vertebrae (L5, T12, L1)

  3. The bony lumbar spine (anterior and posterior columns)
    1. the anterior column: vertebral bodies, intervertebral disc, and ligaments. Unique features of the vertebral bodies:
      1. cancellous bone
      2. variations in shape to enhance load-bearing
    2. the posterior column: pedicle, lamina, articular processes. transverse and spinious processes.
      1. protection
      2. guide motion
      3. outriggers for attachment of muscles and ligaments

  4. Ligamentous support of the lumbar spine
    1. extra-segmental: ALL, PLL, and supraspinious
    2. segmental: ligamentum flavum, interspinious, intertransverse
    3. regional: iliolumbar

  5. The inter-vertebral joint (a closed-packed system consisting of the intervertebral disc (IVD), end-plate, and vertebral bodies)
    1. functional demands: load transmission, "ball bearing", "spacer".
    2. structure of intervertebral disc:
      1. annulus fibrosis: fibrocartilage, lamellar arrangement
      2. nucleus pulposis: mucopolysaccaride gel, 70-90% water
        1. exerts a pre-load on annulus
        2. not a rigid sphere, capable of deformation in 3 directions
      3. vertebral end-plate: hyaline and fibrocartilage
    3. nutritional factors: the IVD represents the largest avascular structure in the body. It does receive blood flow in its periphery. Nutrition is primarily due to osmosis. It's metabolic capacity is greatly affected by reduced pH, for example due to smoking.

  6. The posterior joints (facets)
    1. functional demands:
      1. restrict and guide vertebral motion
      2. limited load-bearing: generally (18-20%) of compressive loads. This depends upon degree of lordosis.
    2. structure: synovial joint formed by superior and inferior articular processes. Ligamentum flavum and multifidius muscle are associated with the joint capsule. Capsule is richly innervated.

  7. The spinal muscular system: Functions to provide dynamic stabilization against a variety of loads, to control movement, to attenuate forces and to provide proprioception. The following is one classification of spinal muscles:
    1. superficial
      1. thoraco-lumbar fascia: this system has multiple attachments, tightens like a "tent" and acts as a primary stabilizer during spinal flexion.
      2. abdominal system: reinforces spinal column by increasing intraabdominal pressure
    2. intermediate
      1. erector spinae: resist forward bending and anterior shear, increases compressive force on motion segment, thus aiding stabilization.
      2. quadratus lumborum: stability against excessive side-bending, assists abdominal system.
    3. deep posterior
      1. multifidious: longer moment arm than erector spinae, great proprioceptive function
      2. other intrinsic muscles
    4. deep anterior: psoas major opposes the erector spinae to "square" the motion segment. If shortened results in increased lordosis and greater stress on the posterior column.
    5. associated muscles
      1. gluteals
      2. piriformis
      3. hamstrings

  8. Neurology of the lumbar spine
    1. general organization
    2. Spinal cord: surrounded by dura, bathed with CSF, terminates at L1. In Cauda Equina nerve roots have own sleave of Pia.
    3. Ventral and Dorsal roots
    4. Spinal nerve: in IVF, tethered by dural sleave
    5. Ventral ramus:
      1. forms lumbosacral plexus
      2. sinu-vertebral nerve: anterior spinal canal, peripheral annulus fibrosis
    6. Dorsal ramus:
      1. medial branch: facet joints, multifidious muscle
      2. lateral branch: erector spinae, L1-L3 cutaneous innervation to the buttocks
      3. intermediate branch: variable
    7. Autonomic fibers
    8. Pain sensitive structures in the lumbar spine: irritated by chemical and mechanical factors
    9. The intervertebral foramen:
      1. formed by: pedicles, posterior annulus, PLL, posterior vertebral body, ligamentum flavum.
      2. contents: dural sleave, nerve root, trunk, dorsal root ganglion, sinuvertebral nerve, vascular structures, fat, lymph
      3. ratio of nerve circumference to IVF circumference:
        1. L1-L4: between 7-22%
        2. at L5 25-30%

KINESIOLOGY: the dynamic unit

  1. The normal motion of the lumbar spine (multi-segmental)
    1. cardinal planes vs. 3-dimensional
    2. measurement issues

  2. The normal motion of the lumbar spine (segmental)
    1. The motion segment (or vertebral unit) frame of reference for segmental motion
      1. contents: 2 adjacent vertbrae, IVD and soft tissues
      2. The nature of movement at the motion segment is determined by: facet planes and disc height
    2. Available motion: from White and Panjabi (appendix)
    3. Concept of joint coupling

  3. The mechanics of the intervertebral disc:
    1. Deformation of the IVD during spinal flexion and extension: normal vs. abnormal disc.
    2. Effect of varying lordosis in the supine position
    3. Intra-discal pressure in various postures and with varied loading.

PATHOKINESIOLOGY: the dysfunctional unit

General considerations
  1. Classification of back pain sources
    1. Viscerogenic
    2. Vascular
    3. Neurogenic
    4. Psychogenic
    5. Spondylogenic (musculoskeletal)

  2. Definitions:
    1. local pain: pain which is felt in the same anatomical area as it's source.
    2. radicular pain: pain which is felt along the pathway of a peripheral nerve.
    3. referred pain: pain which is felt in different anatomical location than its source.

  3. Issues relating to the classification of LBP:
    1. Should a classification be based upon morphologicaL changes (Klrkaldy-Willis), signs and symptoms (Quebec Task Force), treatment approaches (Mckenzie, Erhard), or a combination (Binckley)?
    2. A classification system must:
      1. be reliable
      2. have predictive validity
    3. An example of classification based upon signs and symptoms: The Modified Physical Therapy Diagnosis Classification (Quebec Task Force)

    Category   Definition

    1 Back pain without radiation
    2 Back pain with referral to extremity, proximally
    3 Back pain with referral to extremity, distally
    4 Extremity pain greater than back pain
    5 Back with radiation and neurological signs
    6 Post-surgical status (< 6 months or > 6 months)
    7 Chronic pain syndrome

  4. Neurological signs
    1. nerve root impairment: generally unilateral symptoms, pain often disproportionate to stimulus
      1. irritation: pain when subjected to mechanical distortion, may have inhibitory weakness and parasthesias. DTR's usually normal.
      2. compression: loss of conductivity which results in weakness and sensory impairment in corresponding tissues. DTR's usually sluggish or absent.
      3. inflammation: often pain at rest, increased with mechanical distortion. May be caused by repetitive distortion or chemical irritant such as a herniated nuclear pulposis. May have inhibitory weakness and parasthesias. DTR's usually normal.
    2. spinal cord impariment: generally bilateral symptoms
      1. irritation: pain when subjected to mechanical distortion, may have inhibitory weakness and parasthesias. DTR's usually normal.
      2. compression: loss of conduction, paraparesis, sensory loss, DTR's usually absent at the level of the lesion, hyperactive distal to the lesion. (+) Babinski, (+) Clonus.
      3. inflammation: diffuse pain, (+) SLR, (+) Kernig sign. Often due to infectious process.
    3. neuropathy: often "Stocking-Glove" distribution of weakness and sensory disturbance. Often associated with diabetes mellitus, ETOH abuse, AIDS related complex or ingestion of various toxins.

  5. Types of sensory impairment
    1. parasthesias
    2. anesthesia
    3. hyperesthesia

  6. Types of muscular "weakness"
    1. inhibitory
    2. disuse
    3. metabolic
    4. loss of innervated motor units (true neurological impairment)
    5. considerations:
      1. myotome vs. peripheral vs. central
      2. local or diffuse

  7. Interpretation of straight leg raising test (SLR)
    1. goal: determine "tethering" of neuromeningeal pathway, determine the extensibility of the hamstring muscles.
    2. Interpretation: for a (+) SLR the following should be present:
      1. "severe pain" distal to the knee
      2. increased pain <30 degrees of SLR
      3. (+) Lasique maneuver
      4. (+) well-leg raising

Pathoanatomical changes

  1. The concept of degeneration of the three-joint system
    1. the final result is DJD with spinal stenosis. Causes are:
      1. trauma
      2. aging
      3. other: congenital, various bone diseases
      B. posterior joint changes
      1. synovitus
        (lytic enzymes)
      2. cartilage degeneration
      3. capsular laxity
      4. subluxation: erosion
      5. osteophyte formation
      6. facet and lamina enlargement
      C. disc changes
      1. circumferential tears
      2. radial tears
      3. internal disruption
      4. disc narrowing
      5. osteophyte
      6. vertebral body
  2. other factors
    1. sacroiliac joint
    2. soft tissue injury

  3. specific clinical problems
    1. herniated disc: contained vs non-contained
    2. spinal stenosis
    3. facet joint dysfunction
    4. muscle injury/myofascial
    5. piriformis syndrome
    6. reflex sympathetic dystrophy
    7. hip joint: arthrosis, avascular necrosis
    8. sacroiliac joint
    9. referred pain
      1. from musculoskeletal structures
      2. from non-musculoskeletal structures
    10. spondylolesthesis
    11. fractures
    12. osteoporosis

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