Why Knee Bracing is Really Necessary

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Why Knee Bracing is Really Necessary!

Aaron Gresham MS, ATC DonJoy Orthopedics
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Knee Bracing at a Glance

• Why we brace?
• Biological
• A discussion of basic graft healing mechanics
• Mechanical
• A/P drawer
• Hyperextension
• Neuromuscular
• Proprioception
• Motor control

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Types of Braces Manufactured

• Post-Operative
• Prophylactic
• Functional
• Traditional Application
• Current Application
• As defined by AAOS 1986

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Post-Operative Braces

• Use immediately after surgery
• Generally long leg designs
• Primarily ROM control
• Used as protection

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Prophylactic Braces

• Serve as protective function only
• Single and double uprights now used
• Football
• Skiing
• Motorcross
• Womens Basketball?

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Functional BracesTraditional Applications

• Provide mechanical stability in ligament
  deficient knee
• Used in sports only
• Lenox Hill-1972

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Functional BracesCurrent Application

• Provide mechanical stability both sports and ADL
• Post-operative use ROM control/ graft strain
  protection
• Prophylactic both repaired
• and non-injured

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ACL Deficient Patients

• Have Difficulty..
• stop quickly on the injured leg
• run downhill
• land after jumping
• do quick lateral movements
• WHY?

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Why?

• These movements involve
• an extended knee
• quadriceps recruitment before foot strike
  (open kinetic chain)
• Lack of proprioception

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Proprioceptive Effects

• Braces amplify skin and subcutaneous nerve
  information to provide biofeedback that enhances
  proprioception
• Braces also provide enough mechanical support to
  permit muscles to relax so they no longer have to
  stabilize the injured area.
• Spasms are therefore reduced or eliminated thus
  helping to control pain instability

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How to Optimize this Effect?

• Maximize contact area?
• Provide constant force with motion?
• Provide pressure in key areas?
• Increase stiffness?
• No one really knows!
• A key key area for future research!

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Things we have seen

• If any substantial injury occurs there is a
  shutdown of some muscles, and a loss of
  proprioception
• A functional knee brace allows the muscles to
  relax thus preventing spasms Pain
• If the brace is removed to early the patient is
  uncomfortable and feels unstable
• A brace has no effect on response latencies and
  knee bracing increased activity in antagonist and
  stabilizer but not the prime mover muscles
  (Voight, Blackburn and Pflaster- 1998 AAOSM)

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Things we have seen

• ACL deficient knees have reduced proprioception
  compared to the uninjured knee ( Barack et al -
  Am J Sports Med 1989
• This loss of proprioception is believed to be
  caused by the loss of sensory perception within
  the ACL (Solomonow et al - Mosby 1991)

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History of a New ACL
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Graft Ligamentization

• Graft will lose its strength very quickly
  (avascular necrosis)
• Between 6-12 weeks graft is at its weakest
  careful with exercises
• A year after operation 75 initial strength
• Brace protection the first year crucial
• Brace makes functional exercise/ activity
  possible
• Less painful surgery, more risky behavior?

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Anatomic and Physiologic Considerations

• Leverage
• All braces utilize leverage for mechanical
  control of translations and/ or rotations
• Braces are applied to the two longest lever arms
  in the body
• Using leverage we can control rotations/
  translations in frontal and saggital planes
• Brace leverage advantage is reduced as flexion
  angle increases

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Types of BracesPassive vs Dynamic

• Dynamic design actively addresses the instability
  at all times
• With passive designs, some portion of the
  instability must occur before the brace can block
  translation.

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Length is Important

• Length increases leverage and thus enhances
  control on flaccid post-operative muscles
• The proper brace length places the distal end of
  the brace at proper position. It helps
  suspension!
• Length of leg and special needs are only reasons
  for short braces or calf cuffs

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Brace Selection

• Define
• Instability
• Mechanical VS functional
• Primary and secondary instabilities
• Material properties address specific demands
• Fit, comfort and appearance
• Patient age, condition, expectations, intended
  use and special needs

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Custom VS OTS

• Manufacturing process make no difference!
• Functional design and material properties
  determine brace function.
• Fit/ Special needs
• Expectations (sports)
• A/P- No Difference/ V/V- Depends on strength of
  material.

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New Technology in ACL Bracing
Introducing DonJoys latest advancement in
Anterior Cruciate Ligament protection
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Why did we develop FourcePoint?

• 70 ACL injuries are non-contact (cutting,
  jumping, etc.)
• Quadriceps have been attributed to the injury
  mechanism
• Women are 3-7x more likely to incur ACL injury
• Females participation in sports ? 800 since
  70s
• Conflict between rehab and knee laxity
  (aggressive vs conservative)
• Reduce quadriceps shear by increasing flexion
  angle
• Enhance Four-Points of Leverage
• Increase comfort and confidence

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Mechanism

• FOURCE POINT utilizes a leaf spring mechanism
  (like a truck)
• Applies a gradually increasing resistance during
  knee extension
• Resistance engages in the last 25 (relative to
  the stop)
• Increases knee flexion

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Design Rationale

• What puts the ACL at risk?
• Rehab important to successful ACL-R (Trend toward
  accelerated rehab)
• Graft is weak (Noyes)
• Quads induce injury (Garrett and Boden Noyes)
• Result quad induced graft elongation

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FP Research - Design Rationale

• Conclusion Indicates rehab can cause permanent
  laxity! (Demonstrated by Beynnon study)

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Summary

• FourcePoint Technology enhances the DonJoy
  Four-Points of Leverage design by damping knee
  joint extension, which improves the mechanical
  performance of the brace and reduces shear forces
  at the knee

• 3 Key Benefits
• Reduces injury potential -- At Risk positions
• 4-points Enhancement -- Both Active and Dynamic
• Comfort -- Eliminates hard stop, creates feeling
  of a more natural gait
• (Other Females ACL-R epidemic , ACL Deficient,
  Prophylaxis-not football)

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Clinically Proven Results

• Immediate Effects of a Knee Brace with a
  Constraint to Knee Extension on Knee Kinematics
  and Ground Reaction Forces in a Stop-Jump Task
  (Garrett study, 2004)
• Results Showed an increase in knee flexion
  angle by 5, thus reducing the strain on the ACL

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