Lower Extremity Consequences of Core Dysfunction

1
Lower Extremity Consequences of Core
Dysfunction

• Joseph M. Hart, PhD, ATC
• University of Virginia
• Orthopaedic Surgery
• Sports Division

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Introduction

• Core stability may provide several benefits to
  the musculoskeletal system, from maintaining low
  back health to preventing knee injury
• Willson J D, Dougherty C P, Ireland M L, and
  Davis I M, Core stability and its relationship to
  lower extremity function and injury. J Am Acad
  Orthop Surg, 2005. 13(5) 316-25.

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What is the core?What is core stability?
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Where is the core

• Lumbo-pelvic-hip complex
• Includes the active passive structures that
  either produce or restrict movements of the
  lumbar, hip or pelvic segments

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What is the core?

• Movements/ stability occurs in 3 planes
• Sagittal Plane
• Frontal Plane
• Transverse Plane

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What is the core?

• Sagittal Plane stability
• Rectus abdominis
• transverse abdominis
• erector spinae
• multifidus
• gluteus max
• hamstrings
• Flexion/ extension
• Co-contraction causes trunk stiffness and raises
  intra-abdominal pressure
• rigid cylinder

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What is the core?

• Movements/ stability occurs in 3 planes
• Sagittal Plane
• Frontal Plane
• Transverse Plane

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What is the core?

• Frontal Plane
• Glut med., glut min. (1º lateral hip stabilizers)
• Quadratus lumborum
• Unilateral ipsilateral pelvis elevation
• Contralateral spine stiffness
• Perhaps best suited for spine stability active
  during nearly all upright tasks
• Hip adductors (magnus, longus, brevis, pectineus)

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What is the core?

• Movements/ stability occurs in 3 planes
• Sagittal Plane
• Frontal Plane
• Transverse Plane

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What is the core?

• Transverse Plane stability
• HIP rotation
• glut max., glut med.
• Piriformis
• superior/inferior gemelli
• quadratus femoris
• obterator internus/externus
• Trunk rotation
• internal/external obliques
• iliocostalis lumborum
• multifidus

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What is the core?

• Thoraco-Lumbar Fascia
• Covers and inter-connects muscles and fascia
  surrounding the spine
• Helps create a stabilizing corset effect
• Provides connective support from LE to UE
• Allows for integrated kinetic chain activities

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What is core stability
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What is core stability

• The ability of the Lumbo-pelvic-hip complex to
  prevent buckling of the vertebral column and to
  return it to equilibrium following perturbation
• Coordination and co-contraction of muscles
  provides spine stiffness
• Rigid Cylinder

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What is core stability

• the ability to control the position and motion
  of the trunk over the pelvis and leg to allow
  optimum production, transfer and control of force
  and motion to the terminal segment in integrated
  kinetic chain activities.
• Kibler W B, Press J, and Sciascia A, The role of
  core stability in athletic function. Sports Med,
  2006. 36(3) 189-98.

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What is core stability

• Core stability is instantaneous
• Must continually adapt to changing postures and
  loading conditions
• Ensure integrity of spine and provide stable base
  for movement of extremities.
• Absorb forces transmitted through the lower
  extremity during activity

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Importance of core stability

• Mechanical base for motion of the distal segments
• Many extremity prime movers attach to the core
• Core muscles are active before initiation of
  extremity movement.
• Proximal stability for distal mobility

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Importance of Core Stability

• Motor control
• Carefully coordinated contractions from
  antagonistic muscles is necessary to stabilize
  during posture, activity and to react to
  perturbations.
• Muscle activity assists with attenuating forces
  transmitted through the lower extremity to the
  spine during activity
• Neuromuscular training reduced serious knee
  injury in females by 62 (Hewett, 1999)
• Included abdominal curls, back extension exercise

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Importance of Core Stability

• Muscular capacity( ie endurance)
• Trunk muscle endurance is of greater value than
  the ability to generate force in the prevention
  of LBP (McGill, 2003)

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Importance of Core Stability

• the product of motor control and muscular
  capacity of the lumbo-pelvic-hip complex.
• Leetun D T, Ireland M L, Willson J D, Ballantyne
  B T, and Davis I M, Core stability measures as
  risk factors for lower extremity injury in
  athletes. Med Sci Sports Exerc, 2004. 36(6)
  926-34.

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Importance of Core Stability

• What is needed to achieve optimal stability?
• Depends on task/ activity
• Balance/ symmetry for co-contraction
• Endurance/ motor control during fatiguing tasks
• Same muscles that stabilize also needed for
  breathing at times of high O2 demand (fatiguing
  exercise)
• Loss of stabilization during high intensity
  exercise?
• --(McGill, 1995)

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What is Core Dysfunction
Problem for active people
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Core Dysfunction

• Poor/ altered function of muscles that stabilize
  the lumbar-pelvic-hip complex
• Causes?
• Muscle Weakness
• Poor muscular endurance
• Fatigue
• Pain/ injury avoidance
• The important question
• What happens during activity when muscles cannot
  stabilize the lumbar spine, pelvis and hips?

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Core Dysfunction

• Lumbar spine experiences compressive loads gt6000N
  
• Passive restraints able to resist only 90N
• Remaining support provided by active tissue
• What happens when muscles fatigue quickly or at
  different rates?
• COPING MECHANISM..

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Low Back Pain

• Core Dysfunction is common in persons with LBP

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Low Back Pain

• Non-specific LBP presents a major clinical
  problem due to the likelihood of high cost,
  limited activity levels and recurrence.
• Back injuries account for 20 of all injuries and
  illnesses in the workplace
• 2 of the US workforce are compensated for back
  injuries each year
• Enormous economic burden ?25 billion annually

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Low Back Pain

• The likelihood of experiencing LBP increases with
  age
• peak prevalence of LBP occurs in persons aged
  55-64 years in US
• 85-90 of the population is likely to experience
  an episode of low back pain in their lifetime
• 2-5 of the population at least once every year.
• LBP causes the greatest level of activity level
  limitations in persons less than 45 years.

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Low Back Pain

• Back pain etiology is multifactorial
• What do we know about risk for developing LBP?
• Previous LBP including (frequency and duration of
  symptoms)
• Weak, highly fatigable and unbalanced muscles
• Specifically, poor lumbar paraspinal endurance
• (Biering-Sorensen)
• Hamstring tightness
• Poor spinal flexibility
• Reduced lumbar lordosis

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Back to the core
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The core question

• How does fatigue affect muscular stability of the
  lumbar spine, pelvis and hips?
• In the presence of Recurrent Low Back Pain?
• Poor core stability
• How does this affect Lower Extremity muscle
  function?
• Lower extremity injury risk??

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Research Findings

• Persons with LBP who fatigue quicker (lumbar
  extension endurance) tend to have more quadriceps
  inhibition
• Suter, 2001
• Localized lumbar paraspinal muscle fatigue causes
  increased quadriceps inhibition
• Hart, et al, 2005

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Knee Extension Force
Quad EMG
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Central Activation Ratio (C.A.R.)

• CAR estimate of muscle inhibition
• FMVIC ? Force of MU voluntarily recruited
• FSIB ? Force of MU electrically recruited
• FMVIC FSIB ? Force of TOTAL MU pool

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Research Findings

• Compensation for local lumbar paraspinal fatigue
  during gait
• Similar to avoidance strategy observed in persons
  with injured/ reconstructed knee -Hart et
  al 2005

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Research Findings

• Postural compensation for local lumbar fatigue
• Forward trunk posture (Madigan, 2006)
• More anterior COP during stance
• Redistribution of ankle, knee and low back
  torques during stance
• How will this affect Gait?

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Is trunk forward lean bad?
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Is trunk forward lean bad?

• Anteriorly displaced ground reaction force vector
  during activity/ gait
• Reduces sagittal plane knee joint moment
• Indicates quadriceps eccentric control during
  gait

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Trunk Forward Lean

• Alters force attenuation at the knee
• Etiology or forward lean?
• Weak Gluteals?
• Weak Quadriceps?
• Weak Lumbar paraspinals
• Poor endurance in muscles that stabilize pelvis,
  spine, hips?
• Sequellae?
• Higher thoraco-lumbar disc loads
• Quadriceps atrophy/ weakness
• LE joint surfaces exposed to unusual/ excessive
  forces

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Trunk Forward Lean

• Flat-back patients show similar gait
  adaptations to persons with knee OA
• Reduced velocity, reduced stride length,
  increased stance phase duration
• Note continued high force during mid-stance in
  persons with forward flexed trunk posture during
  gait

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Trunk Forward Lean

• Compensation for forward flexed position of the
  trunk is a crouched posture
• Flexed knee and hip in stance and during gait
  (also similar to patients with advanced OA)
• Places weaker gluteals in a mechanically
  advantaged position
• Higher demand on quadriceps

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Core Stability and LE Injury

• Inappropriate positions of hips and trunk during
  gait or landing may place LE joints at risk for
  injury
• Inability of hip rotators to control femur
  rotation ? knee valgus/ internal rotation

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Gait Compensations

• Persons recurrent LBP exhibit a quadriceps
  dominant pattern during gait. (Hart, 2005)
• Adaptation to poor spine, pelvis, hip muscular
  stability?

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Gait Compensations

• What other group exhibits quadriceps dominance,
  trunk lean, poor control of femur rotation?
• position of no return
• Body forward flexed
• Hip adducted
• Internally rotated
• Valgus knee
• Tibia externally rotated
• Foot pronated

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Review

• Persons with poor Lumbo-pelvic-hip stability
• During exercise Fatigue
• Deteriorated postural control
• Difficult for hip muscles to appropriately
  position femur during gait, landings, etc
• Trunk Forward Lean
• Re-distributing Lower extremity forces during
  gait
• Inhibited Quadriceps
• Reduced knee joint torque during gait
• Reliance on proximal, postural muscles
• (which are probably weak, inhibited, poor
  endurance)
• What absorbs forces if muscles cannot?

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Discussion

• Core stability may provide several benefits to
  the musculoskeletal system, from maintaining low
  back health to preventing knee injury

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Thank you for your attention
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