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Stabilization Mechanisms of the Lumbar Spine

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The spine is inherently unstable, without the support of the surrounding musculature. ... Recoil Force = Potential Contractile Force. Thoracolumbar Fascia (TLF) ... – PowerPoint PPT presentation

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Title: Stabilization Mechanisms of the Lumbar Spine


1
Stabilization Mechanisms of the Lumbar Spine
  • Kevin Domboski
  • Nick Richey

2
  • The spine is inherently unstable, without the
    support of the surrounding musculature.

3
Posterior Ligamentous System
  • Interspinous, Supraspinous, Facet Jt Capsule, and
    Thoracolumbar Fascia (TLF) provide PASSIVE
    SUPPORT
  • Balance between 24 55 of imposed flexion
    stress

4
Posterior Ligamentous System (Cont.)
  • ALL, PLL, and Ligamentum Flavum become aligned
    during flexion/extension
  • Ligaments become stiffer when loaded rapidly
    (Visoelastic)
  • Posterior Ligaments can sustain over 50 of the
    flexion stress on the spine

5
Posterior Ligamentous System (Cont.) 2 Passive
Systems at Work
  • Erector Spinae Recoil
  • In full flexion the muscle no longer contract
  • Recoil Force Potential Contractile Force
  • Recoil of Posterior Ligament System

6
Thoracolumbar Fascia (TLF)
  • Consists of 3 layers that cover the back
    musculature
  • Primary Importance of TLF is passive resistance
    to flexion
  • TLF Mechanism- tends to approximate the vertebrae

7
TLF Hydraulic Amplifier
  • Hydraulic Amplifier acts as even more of a
    stabilizing mechanism
  • The erector spinae contract
  • The TLF resists the muscle by increasing the
    tension in the fascia

8
Trunk Muscle Action
  • Spinal Extensor Muscles
  • Superficial Erector Spinae
  • Deep Multifidi, Interspinales,
    Intertransversarii
  • Abdominal Muscles
  • Superficial Recutus Abdominus, External Oblique
  • Deep Transversus Abdominus, Internal Oblique

9
Intersegemental (Deep) Muscles
  • Location gives faster reaction time
  • Smooth and more efficient stabilizing control
    system
  • 7x the muscle spindles ? Proprioceptive Role

10
Multifidus
  • Primary Function- Control lordosis at its level
    and counteract any imposed loading
  • Most important for lumbar stabilization

11
Multifidus
  • Act at a 90 angle to spinous process
  • Produces posterior sagittal rotation (rocking)
  • Neutralizes spinal flexion
  • Active during whole range of flexion, rotation in
    either direction, and during extension movements
    of the hip

12
Multifidus
  • Recovery does not occur automatically
  • Can be retrained Must Be retrained
  • Treatment ( Bed Rest, Analgesics, NSAIDS)
  • 4 wks 17diff
  • Treatment and Rehabilitation
  • 4 wks .7 diff.

13
Superficial Muscles
  • Consist of two muscles Iliocostalis
    Longissimus
  • Lumbar Longissimus Act more on the posterior
    translation of the vertabrae than the posterior
    sagittal rotation.
  • Lumbar Iliocostalis Cooperate with multifidus to
    neutralize flexion

14
Abdominal Muscles
  • Superficial Abdominals
  • Rectus Abdominus
  • External Obliques
  • Prime movers of trunk flexion
  • Deep Abdominals
  • Transversus Abdominus
  • Internal Obliques
  • Are the major stabilizers
  • Tough to contract voluntarily
  • Activated by Abdominal hollowing
  • Activated at the initiation of overhead and lower
    extremity movement

15
Abdominal Performance
  • The ratio of the muscle activity is more
    important than intensity.
  • Abdominal Hollowing helps to train the deep
    abdominal muscles and differentiate from the
    superficial muscles.
  • Transversus Abdominus always activates during any
    trunk movement
  • Always precedes the contraction of other trunk
    muscles in normal subjects.

16
Intra-abdominal Pressure Mechanism
  • Created by the synchronous contraction of the
    abdominal muscles, the diaphragm, and the muscles
    of pelvic floor.
  • Helps reduce axial compression, shear loads and
    transmits loads over a wider area.

17
Local Muscle Dysfunction in Low Back Pain
  • Dysfunction of Traversus Abdmonius
  • Dysfunction of the Multifidus

18
Transversus Abdominus Dysfunction
  • Changes in Motor Control
  • Delayed Activation
  • Direction Specific Contraction
  • Phasic Contraction
  • Loss of Independent Control
  • Response Failure in Natural Speed Movements
  • Mechanism, Relevance and Timing

19
Changes in Motor Control
  • Transversus Abdominus contractions precede
    movement in extremities.
  • T.A. function is found to be poor in patients
    with low back pain.
  • EMG studies show that pts. With low back pain
    have no contraction of T.A. in pre-movement
    period.
  • Lack of T.A. function fails to prepare spine for
    motion.

20
Changes in Motor Control cont.
  • Studies in Upper and Lower extremity reveals
    identical results.
  • In studies of Upper and Lower extremities, T.A.
    function actually occurs after Prime Mover
    Function.

21
Direction Specific and Phasic Contractions
  • T.A. is normally not direction specific however,
    in patients with low back pain, it begins to
    respond in a directionally specific manner.(T.A.
    is unable to control direction specific forces)
  • T.A. also begins to fire in phasic bursts in
    patients with low back pain.
  • Test show one burst with shoulder flx and two
    bursts with ext. (Works with flexing abs)
  • Indicates a change in control by CNS, loss of
    tonic or isometric function of T.A. in patients
    with low back pain

22
Loss of Independent Control
  • Patients with low back pain have delayed T.A.
    function which suggests that the CNS is waiting
    to know what movement is being performed before
    firing the T.A.
  • This change in CNS control suggests that control
    of the T.A. is no longer independent.

23
Natural Speed Movements
  • Patients without low back pain had T.A. that
    responds at high and normal speeds but not slower
    speeds. This suggests the T.A. operates between
    thresholds.
  • Threshold is increased in low back pain patients
    so that T.A. only responds at high speeds.

24
Mechanism, Relevance and Timing
  • Why does low back pain happen?
  • Changes in control of movement by CNS
  • Reflex inhibitiondecreased motor pooldelayed
    muscle activity.
  • Joint effusion, pain, ligament stretch, capsular
    compression are all causes.
  • Fatigue and postural variation also have been
    linked to decreased excitability in the motor
    neuron pool.

25
Summary
  • Transverse Abdominus problems arise because of
    issues with motor control.
  • T.A. issues remain consistent with each other
    regardless of pathology

26
Dysfunction in the Multifidus
  • Muscle Activation
  • Fatiguability
  • Composition
  • Size and Consistency

27
Muscle Activation
  • EMG results show decreased muscle activity at L4
    and L5 vertebral levels during lumbar extension
  • EMG also shows less activity at unstable
    vertebral levels in patients with segmental
    instability.(28 of 87 patients having 4mm or more
    sliding.)

28
Fatiguability
  • Potentially inadequate muscular support over
    extended periods of time.
  • Evidence of fatigue in paraspinals in patients
    with low back pain.
  • Isometric contraction can no longer be
    maintained at a certain level.
  • Dynamic repetitive work can no longer be
    maintained at a certain output.

29
Fatiguability Cont.
  • Patients with low back pain show considerably
    less muscular endurance.
  • greater fatiguability
  • No specific muscles have been identified within
    the extensor group
  • Study by Biedermann et al identifies the
    Multifidus as demonstrating the most fatigue.
  • Local weakness in multifidus is found in elite
    athletes on regular, rigorous training schedules.

30
Composition
  • Muscle fiber size and muscle fiber internal
    structure have been examined.
  • Atrophy is reported as causing some problems but
    its significance is not understood because some
    patients with atrophy never have any problems at
    all.

31
Composition Cont.
  • Internal Structure changes seem to be much more
    of a problem.
  • Fibers appear core-targetoid and moth-eaten
    these changes are considered abnormal.
  • It seems that through surgical intervention and
    physical therapy, that these pathological changes
    can be reversed.

32
Size and Consistency
  • Decreased muscle density can lead to problems in
    the low back.
  • Paraspinals and multifidus have shown atrophy
    with disuse and deconditioning.
  • Pain, caused by injury or trauma is shown to
    significantly decrease multifidus size.
  • Studies show mixed reviews concerning muscle
    size some patients with decreased muscle size
    have back problems and some do not.

33
Size and Consistency Cont.
  • Patients with back injuries lose less muscle size
    and are less likely to have a recurrence of the
    back pain episode when an active treatment
    approach is taken to localize the multifidus.
  • Patients with a more generalized approach to
    treatment showed a lack on recovery of multifidus
    size and are more likely to have long term,
    recurring problems.

34
Summary
  • Since the multifidus provides segmental stability
    in the lumbar spine in normal function,
    dysfunction of the muscle can adversely effect
    patients with low back pain.
  • Rehabilitation that focuses on the multifidus,
    rather than generalizing the low back, is shown
    to be much more effective.
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