Tendon Healing and Grafting

Question 1

Describe the strustural composition of a tendon

Answer 1

• Cellular
  
  • tenoblasts- immature tenocytes
  • tenocytes - spindle fibroblasts (90%)
  • synovial cells
  • chondrocytes (at insertion pts)
• Collagen type 1
  
  • 3 troprocollagen fibrils ->fiber -> fiber bundle -> fascicles
• Ground substance
  
  • HA, PG, LP GAG

Question 2

Describe the blood supply of a tendon

STARRED FOR REVIEW?

Answer 2

Extrinsic (outside of synovial sheath)

• Paratenon
• Mesotenon - via vincula (Longus & brevis)
• Epitenon - sourrounded by paratenon

Intrinsic (wihtin synovial sheath of within tendon

• myotendinous and osteotedinous jxs
• Endotenon

(a different source says intrinsic supply is osseo- and myotendinous jxn, and extrinsic is paratenon [for extra-synovial] and vincula [for intra-synovial]????)

Question 3

Describe tendon healing

Answer 3

INFLAMMATORY PHASE (1ST WEEK)

• Hematoma, recruitment of macrophage and PMN
• Epitendon cells proliferatie
• Fibroblasts invade and produce collage 3

PROLIFERATIVE PHASE (WK 1- WK3)

• fibroblasts deposit collage 3, ECM
• epitendon >endotenon key for collagen deposition

REMODELLING PHASE (>6WKS)

• drop in cellularity and collagen 3 production -> rise in collagen 1 production and reorientation

Question 4

What factors promote extrinsic versus intrinsic healing?

Answer 4

Extrinsic healing (invasion of cells from surrounding and formation of adhesions)

• poor tendon apposition
• immobilization
• crush
• bacterial contamination
• damage of surrunding structures (devasculaized, fracture)

Intrinsic healing (I,P,R stages)

• mobilization
• good tendon apposition
• early repair
• tendon sheath preservation
• limited dissection

Question 5

What are potential sites for tendon harvest and technique

Answer 5

• Palmaris longus
  
  • 3mm, 15cm, 15% of population doesnt have one
  • ulnar to FCR
• Plantaris
  
  • 2mm, 25cm, 5% of population doesnt have one
  • medial and anterior to achilles, 5cm vertical incision
• Long toe extensor
  
  • of D2,3,4

Question 6

WHAT IS THE CELLULAR STRUCTURE OF TENDON

Answer 6

• Tenoblasts and tenocytes - 90%
• Synovial cells, chrondrocytes, capillary endothelial cells - 10%

Question 8

what structure detects changes in tendon tension / pressure ?

Answer 8

• golgi tendon organ

Question 9

describe extrinsic vs intrinsic tendon healing

Answer 9

• extrinsic - tendon relies on immobilization and adhesions for repair (original thought was that tendons had no intrinsic capacity to heal)
  
  • fibroblast ingrowth, neovascularization, fibrosis, adhesion
• intrinsic - tendon responsible for its own repair
  
  • 3 stages of tendon healing
  • inflammatory
  • proliferative
  • remodelling
• likely tendon healing is a combination of extrinsic and intrinsic methods; but knowledge that tendon can revascularize from paratenon (extra-synovial) or vincula/synovial diffusion (intra-synovial)