1. Physiology of Muscle, Tendon & Ligament Healing
Jason R. Miller, DPM, AACFAS, FAPWCA
Dept. of Surgery

2. 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.

3. 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

4. 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.

5. Tendon Histology 30% Collagen, 2% Elastin, 68% Water
Bulk is supplied by reticulin
70% Type I collagen

6. Ligament Histology 33% Composition: 90% Type I collagen,
Elastin, Glycosaminoglycans.
67% Water

7. 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.

8. 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.

9. Tendon Anatomy

10. Tendon Anatomy

11. 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 tendon’s 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.

12. Tendon Sheath Anatomy

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

14. Tendon Attachment to Bone
Attach at 90° angles to bone in 4 layers:
Tendon collagen fibers
Fibrocartilage
Bone
Sharpey’s fibers – originate in bone and end in perisoteum.

15. 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

16. 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

17. Tendon Healing
Stage 4: Fibers align, increasing strength further. Swelling and vascularity reduce. AROM can be performed.
4 weeks

18. Tendon Healing Healing can be augmented by: Early mobilization US
Elec. Stim.
Growth factors

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

20. 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.

21. Tendon Suture
Vicryl®/Dexon®: Absorbable polygalactic acid/polyglycolic acid strong enough to keep repair intact.
Ethibond®: Strong, Non absorbable braided polyester. Good choice.

22. 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

23. 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.

24. Securing Tendon To Bone
Trephine plug
3 Hole Suture
Buttress & button anchor
Tunnel w/ sling
Screw & washer (cleated polyacetyl, Ti)
STATAC, Mitek, PEBA

25. 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

26. 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

27. 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

28. 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.

29. Nerve Healing & Repair Peripheral Nerves Conducting axons
Insulating Schwann cells
Connective tissue matrix

30. Nerve Healing & Repair Nerve fibers Basal lamina layer
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”

31. Nerve Healing & Repair Endoneurium Perineurium
Myelinated & unmyelinated are embedded with this CT
Perineurium
Compact layer that encircles the endoneurium composed of concentric, elongated perineural cells

32. Nerve Healing & Repair Perineurium Internal Epineurium
Partitions nerve fibers into fascicles
Internal Epineurium
External Epineurium
Concentric layers of CT encircling the fascicles
Contain fibroblasts, macrophages, mast cells, BVs, and fat

33. Nerve Healing & Repair Seddon classification of nerve injury 3 grades
Neurapraxia
Axonotmesis
Neurotmesis

34. 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.

35. Seddon classification
Etiologies:
Direct mechanical compression
Ischemia/PVD
Metabolic derangements
Disease or toxinscausing demyelination

36. 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

37. 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

38. Axonotmetic Injuries Mixed sensory & motor nerves regenerate slower
Nerve complexity dictates accuracy of nerve regeneration

39. 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.

40. 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)

41. Mackinnon & Dellon Added Grade VI
Combinations of the previous grades of injury.

42. 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.

43. 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 Seddon’s 3 grades

44. 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.

45. Thank You!