Physiology of Muscle, Tendon

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Physiology of Muscle, Tendon Ligament Healing

• Jason R. Miller, DPM, AACFAS, FAPWCA
• Dept. of Surgery

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Purpose of Lecture

• Tendon repair and tenoplasty are important
  aspects of podiatric surgery.
• Ligament ruptures are common and repairs are
  often needed.
• Knowledge of tendon and ligament healing allow
  the surgeon to make appropriate decisions
  concerning procedures, materials, post-op care
  and possible complications.
• Understand the basic biology of nerves and their
  response to injury.

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Definitions

• Tendon Transfer Detachment of a tendon of a
  functioning muscle at its insertion
• Tendon Transposition Rerouting without
  detachment to assist in other functions
• Muscle-Tendon Transplantation Detachment of a
  muscle tendon at both the origin and insertion to
  a new location with the NV structures intact.
• Tendon Suspension Tendon supports a structure

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Tendon Anatomy

• Very strong, stronger than muscle for size
• As strong as bone with a failing point similar to
  steel!
• Can transmit force through ability to glide
• Passive component of the musculotendinous unit in
  light of their incredible influence on the foot.

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Tendon Histology

• 30 Collagen, 2 Elastin, 68 Water
• Bulk is supplied by reticulin
• 70 Type I collagen

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Ligament Histology

• 33 Composition 90 Type I collagen,
• Elastin, Glycosaminoglycans.
• 67 Water

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Anatomy of the Tendon

• Tropocollagen the most basic molecular unit of
  tendon
• 3 Coverings
• Endotenon- fascicles are surrounded by this
  areolar CT, contains BV, L, N, and FB.
• Epitenon- Fascicles bound together by this 1-2
  cell fibroblastic synovial layer
• Paratenon- loose areolar layer continuous with
  the epitenon perimysium, straight.

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Anatomy of the Tendon

• Tendon/Synovial Sheath acts like a pulley when
  tendon has an angled course.
• Peritenon- term applied collectively to all CT
  structures associated with a tendon incl para-,
  meso-, epi-, and endotenon.

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Tendon Anatomy
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Tendon Anatomy
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Tendon Circulation

• 3 Sources
• Small amount from the central blood vessels
  originating in the muscle.
• Some from vessels of the bone and periosteum near
  the tendons insertion.
• Majority comes from small vessels in the
  paratenon or through the mesotenon. If absent
  then carried thru the vincula. Synovial fluid
  also nourishes the tendon.

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Tendon Sheath Anatomy
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Tendon Innervation

• Afferent supply only
• Source in musculotendinous junction and external
  local nerves.
• Golgi tendon organs monitor increases in
  tension rather than length.

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Tendon Attachment to Bone

• Attach at 90 angles to bone in 4 layers
• Tendon collagen fibers
• Fibrocartilage
• Bone
• Sharpeys fibers originate in bone and end in
  perisoteum.

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Tendon Healing

• 4 Stages
• Stage 1 Severed ends joined by fibroblastic
  splint. At the end of this stage, the repair
  site is in its weakest state with serous material
  granulation tissue (Zone of degeneration) 1
  week

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Tendon Healing

• Stage 2 Increase in paratenon vascularity and
  collagen proliferation.
• 2 weeks
• Stage 3 Collagen forms longitudinally,
  increases strength. Controlled passive motion is
  beneficial to decrease fibrous adhesions.
• 3 weeks

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Tendon Healing

• Stage 4 Fibers align, increasing strength
  further. Swelling and vascularity reduce. AROM
  can be performed.
• 4 weeks

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Tendon Healing

• Healing can be augmented by
• Early mobilization
• US
• Elec. Stim.
• Growth factors

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Tendon Lengthening

• Muscle strength will be reduced by one grade
  (Polio Foundation) once healed.
• Transfers will equally degrade muscle strength.

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Tendon Suture

• Surgilon Non absorbable, non reactive.
  Increased strength during end of Stage 1.
• Stainless steel Strongest, least reactive.
  Should be removed, can tear thru tendon.
• Silk Old school surgeons.
• Tevdek/Ticron Nonabsorbable braided
  polyester, resists gapping at 3 weeks better than
  nylon or polypropylene.

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Tendon Suture

• Vicryl/Dexon Absorbable polygalactic
  acid/polyglycolic acid strong enough to keep
  repair intact.
• Ethibond Strong, Non absorbable braided
  polyester. Good choice.

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Methods of Tendon Repair

• Bunnell end to end Strong, but restricts
  tissue.
• Double right angle Quick, for small tendons.
• Lateral trap Tightly pulls edges of tendon
  together w/o damaging central microcirculation

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Methods of Tendon Repair

• Chicago Simple X stitch
• Robertson Best method of anastomosis for
  tendons of differing sizes.
• Interlace Method for attaching small to large
  tendons.
• Herringbone stitch insertion Method for
  grafting one tendon into center of another.

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Securing Tendon To Bone

• Trephine plug
• 3 Hole Suture
• Buttress button anchor
• Tunnel w/ sling
• Screw washer (cleated polyacetyl, Ti)
• STATAC, Mitek, PEBA

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Objectives of Tendon Transfer

• To improve motor function where weakness or
  imbalances exist to prevent deformity.
• To eliminate deforming forces
• To provide active motor power
• To provide better stability
• To eliminate or reduce need for bracing
• To improve cosmesis

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Principles of Transfer

• Do not create new imbalances
• Understand anatomy physiology
• Correct fixed/structural deformities 1st
• Perform at appropriate age
• Select suitable tendon
• Provide a mechanically efficient line of pull
• Perform stabilizing procedures 1st

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Principles of Transfer

• Preserve the gliding mechanism
• Use atraumatic technique
• Preserve neurovascular supply
• Provide adequate muscle-tendon tension
• Use secure fixation techniques
• Appropriate post-op management

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Ligamentous Healing

• Treated similarly to tendon, blood supply similar
  without muscular blood supply
• Healing stages similar
• Primary repair of initial ruptures is preferred
• Suture choices same as tendon.

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Nerve Healing Repair

• Peripheral Nerves
• Conducting axons
• Insulating Schwann cells
• Connective tissue matrix

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Nerve Healing Repair

• Nerve fibers
• Ensheathed by Schwann cells
• Myelinated fibers are individually encased
• Non-myelinated fibers are encased in groups
• Basal lamina layer
• Envelops Schwann cells
• Critical role in supporting axonal regeneration
  by serving as a highway

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Nerve Healing Repair

• Endoneurium
• Myelinated unmyelinated are embedded with this
  CT
• Perineurium
• Compact layer that encircles the endoneurium
  composed of concentric, elongated perineural cells

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Nerve Healing Repair

• Perineurium
• Partitions nerve fibers into fascicles
• Internal Epineurium
• External Epineurium
• Concentric layers of CT encircling the fascicles
• Contain fibroblasts, macrophages, mast cells,
  BVs, and fat

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Nerve Healing Repair

• Seddon classification of nerve injury
• 3 grades
• Neurapraxia
• Axonotmesis
• Neurotmesis

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Seddon classification

• Neurapraxia - mildest grade of nerve injury
• Reduction or complete blockage of conduction
  across a segment of nerve.
• Axonal continuity is maintained
• Nerve conduction is preserved proximal distal
  to the lesion but not across it
• Usually reversible injuries, full recovery in
  days to weeks.

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Seddon classification

• Etiologies
• Direct mechanical compression
• Ischemia/PVD
• Metabolic derangements
• Disease or toxinscausing demyelination

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Seddon classification

• Axonotmesis
• Interruption of the axons with preservation of
  the surrounding CT highway
• Distal Wallerian degeneration of the axons occurs
  during a several day period
• Direct e-stim will NOT give rise to nerve
  conduction or muscle response
• Recovery can occur through axonal regeneration
  due to CT highway

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Seddon classification

• Schwann cells proliferate and form longitudinal
  conduits (bands of Bungner) through which axons
  regenerate in months.
• Recovery depends on
• Extent of retrograde axonal loss
• Time to regenerate reinnervate target
  muscles/sensory end organs
• Regenerate at 1mm/day

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Axonotmetic Injuries

• Mixed sensory motor nerves regenerate slower
• Nerve complexity dictates accuracy of nerve
  regeneration

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Seddon Classification

• Neurotmesis most severe grade
• Disruption of axon, myelin, and CT highway
  components of nerve.
• Recovery through regeneration cannot occur
• External continuity is preserved but intrneural
  fibrosis occurs
• Also includes complete loss of continuity
• Surgery is required to remove roadblocks to
  healing.

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Sunderland Classification

• Created 5 grade system.
• Grade I neurapraxic injury
• Grade II axonotmetic injury
• Grade III endonerium disrupted
• Grade IV additional disruption of perineurium
• Grade V epineural continuity is disrupted
  (neurotmesis)

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Mackinnon Dellon

• Added Grade VI
• Combinations of the previous grades of injury.

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Operative Decision Making

• Open injury
• Lesion in continuity
• Medical mgmt. with close F/U, EMG/MRN
• Lesion Discontinuity
• Sharp transection end to end repair
• Blunt transection delayed repair, resect scar,
  graft, repair.

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Operative Decision Making

• Closed Injury
• Majority caused by stretch and/or compressive
  forces.
• Hematoma may require emergent surgery (ie
  compartment syndrome, pseudoaneurysm)
• Most injuries do not involve transection
• May represent any of Seddons 3 grades

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Summary

• Guidelines will help you as a surgeon to deal
  with tendon, ligament, nerve injuries.
• Understanding principles will lead to more
  successful repairs and mgmnt.

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Thank You!