Tendon Injury, intro and healing

Different types of Tendon injuries we will be learning about

- tendon rupture

- tendinopathy

- tenosynovitis

tendon and ligaments are classified as

dense connective tissue

Tendon and ligaments have low cellularity meaning

they have few fibroblasts and fibrocytes which are cells that produce and maintain the extracellular matrix

the primary component of the tendons and ligaments extracellular matrix is

type 1 collagen

the main difference between tendon and ligaments, is that ligaments also have

varying amounts of elastin which allows them to have a little more strech than tendons

function of tendons

to transmit muscle forces to the bone

difference between tendons and ligaments pertaining to the collagen fibers

- tendon: all fibrils aligned in same direction

- ligament: collagen bundles aligning in several different directions depending on the joint forces the ligament must control

tendons only have one line of pull on them and so the collagen fibers

all align in one direction

4 phases of healing in tendon injury

- immediate injury

- inflammatory phase

- proliferative/repair phase

- maturation and remodeling phase

Immediate Injury Phase I: bleeding response

platelets initiate a fibrin clot that stops the bleeding

Immediate Injury Phase I: Platelets provides

very weak stabilization between the 2 torn ends (fibrin and fibronectin crosslinks with collagen ends)

Inflammatory Phase II: timing

- builds over the first 48 hours

- phase will gradually decline and complete within 7 - 14 days

Inflammatory Phase II: Chemotactic mediators signal

inflammatory WBC and phagocytic cells clean up "debris" from the injury

Inflammatory Phase II: duration of the phase depends on numerous factors including

- extent of tendon injury

- persons nutritional status

- persons health status

Proliferative/Repair Phase III: begins within

the 1st week of injury and overlaps the latter half of the inflammatory phase

Proliferative/Repair Phase III: the Chemical mediators job

signal the fibroblasts (tenoblasts) needed to begin the repar phase

Proliferative/Repair Phase III: Migration and proliferation of fibroblasts begin

laying down the type III collagen scaffold to provide stronger stabilization of the torn ends than the original fibrin/fibronectin stabilization of the torn ends

Proliferative/Repair Phase III: Key necessary element

blood supply, so angiogenesis occurs

Proliferative/Repair Phase III: the type III collagen scaffold has

random orientation

Proliferative/Repair Phase III: tendon is easily re-ruptured in this phase due to

- weaker type of collagen

- random orientation of collagen present

Proliferative/Repair Phase III: Critical to

minimize stresses to the healing tendon

Maturation and Remodeling Phase IV: timing

- begins about 3 weeks following the injury

- overlaps the proliferative phase

Maturation and Remodeling Phase IV: Duration

- most active for the next 12-16 weeks

- tendon to return to normal strength, takes about a year

Maturation and Remodeling Phase IV: During this phase

Type III collagen is replaced by Type I collagen

Maturation and Remodeling Phase IV: as the replacement occurs

the collagen fibrils will align to stresses that are applied to it

Maturation and Remodeling Phase IV: during this phase to facilitate optimal collagen alignment

controlled appropriately timed stresses are important, too much and the tendon re-ruptures, not enough and the strength of the tendon is negatively impacts

Tendons that reside in synovial sheaths (hands) are

at significant risk for adhesions as they are healing

For Tendons at risk for adhesions, it is critical to

- PROM during proliferative phase

- early active motion as soon as possible during remodeling phase

Tendon adhesions can

limit tendon excursions, reducing active joint motion

Tendon injuries can be subdivided into

- macro-trauma

- micro-trauma

Macro-trauma injuries tend to be

acute type injuries including ruptures, either partial or complete caused by excessive tensile load on the tendon

macro-injuries can occur in

- normal tendon

- weakened tendon by indicated micro-traumas

strong direct blows to tendon can

- result in contusions of the tendon

- if blow is significant enough, cause the tendon to rupture

if a blow does not causes a tendon rupture it can instead

bruise the tendon causing at least some micro-damage to the tendon

micro-trauma injuries tend to be

more chronic and are typically overuse injuries

an overuse injury is an injury that occurs because of

repetitive overloading that does not exceed the one-time load tolerance of the tendon