Spine ICF - LBP with Movement Coordination Impairments: Acute or Chronic (Lumbar Spine Instability)

What is it?

• The inability of the spine under physiologic loads to maintain its pattern of displacement so that no neurologic damage or irritation, no development or deformity, and no incapacitating pain occur

• Cause:

  • Increase in size of neutral zone (relative to total ROM)

  • Decrease in passive resistance to motion in elastic zone

Indications

• Low back and/or low back-related LE pain that worsens w sustained positions

• Lumbar hypermobility w posteroanterior segmental mobility testing

• + prone instability test

• Diminished trunk and pelvic region muscle strength, endurance, & neuromuscular control

• Aberrant movements w lumbar active motion testing

Important terms

• Neutral zone: Motion occurring in/around the spine’s neutral mid position is produced against minimal passive resistance

• Elastic zone: Motion occurring near the spinal motion end range is produced against increased passive resistance

• Functional instability: Loss of neuromotor capability to control segmental movement during mid-range

  • Aberrant movements affected by lack of motor control

• Structural instability: Disruption of passive stabilizers that limit the excessive segmental end ROM

  • Excessive ant/post translation on end range flex/ext radiographs

3 Subsystems of stabilization of the spine

• Passive

• Active

• Neural control

Passive subsystem

• Consists of the vertebral bodies, facet joints/joint capsules, spinal ligs, and passive tension from the spinal muscles/tendons

• Provides significant stabilization to the elastic zone and limits the size of the neutral zone

• Also gives the neural control subsystem information about position and motion of the spine

Active subsystem

• Consists of spinal muscles and tendons

• Provides the active forces needed to stabilize the spine in response to changing loads

• Primarily responsible for both supporting the size and motion of the neutral zone

• Similar to passive, also provide information to the neural control subsystem regarding information about the force that each muscle is producing

Neural control subsystem

• Receives information from the active and passive systems regarding positioning of the spine

• Uses this info to act on the spinal muscles to produce the force necessary to maintain spinal stability

Clinical instability

• Occurs when the size of the neutral zone is increased and the subsystems are unable to compensate for this increase, leading to poor control over motion in the neutral zone

• Causes:

  • Degeneration

  • Mechanical injury

  • Poor posture

  • Repetitive occupational trauma

  • Acute trauma

  • Lumbar musculature weakness

S&S Clinical instability

• Presence of aberrant motions (cardinal signs)

  • Altered lumbo-pelvic rhythm

    • In forward bending:

      • Hip motion > lumbar spine motion during first 1/3 of movement

      • Lumbar spine motion > hip motion during last 1/3 of movement

  • Gowers’ sign

    • In return to upright:

      • Lumbar spine motion > hip motion during first 1/3 of movement

      • Hip motion > lumbar spine motion during last 1/3 of movement

  • Deviation from sagittal plane

    • During return to upright stance:

      • Pt uses hands to climb up thighs

  • Instability catch/Shake/Judder

    • Sudden acceleration, deceleration, or stop

    • Momentary shake, quiver, or vibration of the paravertebral muscles

    • Brief out-of-plane movements

  • Painful arc of motion

    • Pt presents w increased pain during a portion of the arc of movement

    • Pt presents w increased pain throughout the arc of movement

• Tenderness of lumbar region

• Referred pain in thigh/buttocks

• Paraspinal muscle guarding

• Pain w sustained posture

Structural instability testing

• Passive lumbar extension test

• Lumbar forward bending >53 degrees measured w double inclinometer

• Lack of lumbar hypomobility w posteroanterior PAIVM test

• + results on each of these tests shows high specificity, and thus structural instability should be ruled in

• However, due to low sensitivity, negative results cannot fully rule out structural instability

Functional instability testing

• Predictors of positive:

  • Positive prone instability test

  • Aberrant motion present

  • Age <41 yrs

  • SLR >91

  • Presence of at least ¾ of these variables has a LR+ of 4 that the pt will respond well to a lumbar stabilization program

• Predictors of negative:

  • Negative prone instability test

  • Hypomobility w PAIVM testing

  • Aberrant motion absent

  • FABQ score less than or equal to 9

  • If 2/4 of the variables are present, Sn = 0.85, and Sp = 0.87

Muscles of the trunk

• Global system:

  • Muscles that work to transfer loads btwn the thoracic cage and the pelvis

  • Muscles that work to change the position of the thoracic cage in relation to the pelvis

    • Larger/superficial muscles:

      • Erector spinae, rectus abdominis, internal/external obliques

• Local system:

  • Muscles that work to control the spinal curvature

  • Muscle that work to give sagittal/lateral stiffness to maintain spinal mechanical stability

    • Smaller/deeper muscles: (muscles connecting to the vertebrae)

      • Transverse abdominis, multifidi, intertransverse muscles

• Exclusion: Quadratus lumborum

  • This muscle is part of both systems!

    • Lateral portion: global muscle

    • Medial portion: local muscle

Treatment

• Functional instability is often a result of an imbalance btwn strong/overactive global muscles and weak/atrophied local muscles, therefore treatment will be to remedy this via a motor control exercise program

• Increase the strength, control, and neuromuscular coordination of the local muscles —> specifically the transverse abdominis and lumbar multifidus have been shown to have the greatest impact on lumbar spine stabilization

• Decrease the tone of the global muscles

• Individuals who received a spinal stabilization program after a first-time incidence of LBP were 5.9x less likely to have a recurrence of the LBP than those who did not receive a program