muscle injury , inflammation & repair

Muscle Injury Inflammation

Repair

Tahir RamzanRiphah International University

Introduction--- Types of injuries

• Primary Injury– Injury from acute or chronic trauma

• Secondary Injury– Inflammatory response to primary injury

3 Phases of Tissue Healing

• Inflammatory –response phase

• Fibroblastic-repair phase

• Maturation-remodeling phase– Healing process is a continuum and phases

overlap one another with no definitive beginning or end points

Inflammatory-Response Phase

• After injury, healing process begins immediately– Destruction of tissue produces direct injury to

cells of various soft tissue

– Characterized by redness, swelling, tenderness and increased temperature

– Critical to entire healing process


• Leukocytes and other phagocytic cells delivered to injured tissue– Dispose of injury by-products through

phagocytosis


• Vascular reaction– Blood coagulation

and growth of fibrous tissue occurs

– First 5-10 minutes vasoconstriction occurs

• Best time to evaluate• Followed by

vasodilation• Effusion of blood and

plasma last 24 to 36 hours

• Chemical mediators– Released from damaged

tissue, white blood cells and plasma

– Histamine, leukotrienes and cytokines assist in limiting exudate/swelling

– Amt of swelling directly related to extent of vessel damage

Inflammatory Response Con’t

• Formation of Clot– Platelets adhere to

collagen fibers and create sticky matrix

• Platelets and leukocytes adhere to matrix to form plug

• Clot formation occurs 12 hours after injury and is complete w/in 48 hrs

• Set stage for fibroblastic phase

• Chronic inflammation– Acute phase dos not

respond sufficiently to eliminate injury agent and restore tissue to normal physiologic state

– Damage occurs to connective tissue and prolongs healing and repair process

– Response to overuse and overload

Inflammatory Response Con’t

• Entire phase last 2-4 days– Greater tissue damage longer

inflammatory phase

– NSAIDS may inhibit inflammatory response thus delaying healing process

• Will assist with pain and swelling

Fibroblastic-Repair Phase

• Proliferative and regenerative activity leads to scar formation– Begins w/in 1st few hours after injury and can last

as long as 4-6 weeks

– Signs and Symptoms of inflammatory phase subside

– Increased O2 and blood flow deliver nutrients essential for tissue regeneration


• Break down of fibrin clot forms connective tissue called granulation tissue– Consist of fibroblast, collagen and capillaries

• Fills gap during healing process– Unorganized tissue/fibers form scar

• Fibroblast synthesize extracellular matrix consisting of protein fibers (Collagen and Elastin)

– Day 6 –7 collagen fibers are formed throughout scar– Increase in tensile strength increases with rate of

collagen synthesis


• Importance of Collagen– Major structural protein that forms strong, flexible

inelastic structure

– Type I, II & III• Type I found more in fibroblastic repair phase

• Holds connective tissue together and enables tissue to resist mechanical forces and deformation

– Direction of orientation of collagen fibers is along lines of tensile strength


• Importance of Collagen– Mechanical properties

• Elasticity– Capability to recover normal length after elongation

• Viscoelasticity– Allows slow return to normal length and shape after

deformation

• Plasticity– Allows permanent change and deformation

Maturation-Remodeling Phase

• Long term process that involves realignment of collagen fibers that make up scar– Increased stress and strain causes collagen fibers to

realign to position of maximum efficiency• Parallel to lines of tension• Gradually assumes normal appearance and function• Usually after 3 weeks a firm, contracted,

nonvascular scar exist– Total maturation phase may take years to be

totally complete


• Wolf’s law– Bone and soft tissue will respond to physical

demands placed on them • Remodel or realign along lines of tensile force• Critical that injured structures are exposed to

progressively increasing loads throughout rehab process

– As remodeling phase begins aggressive active range of motion and strengthening

– Use pain and tissue response as a guide to progression


• Controlled mobilization vs. immobilization– Animal studies show Controlled mob. Superior to

Immobilization for scar formation• However, some injuries may require brief period of

immob. During inflammatory phase to facilitate healing process

Factors that impede healing

• Extent of injury– Microtears vs.

macrotears

• Edema– Increased pressure

causes separation of tissue, inhibits neuro-muscular control, impedes nutrition, neurological changes

• Hemorrhage– Bleeding causes same

neg. effect as edema

• Poor vascular supply– Tissues with poor

vascular supply heal at a slower rate

– Failure to deliver phagocytic cells and fibroblasts for scar formation

Factors that impede healing

• Separation of tissue– How tissue is torn

will effect healing• Smooth vs. jagged

• Traction on torn tissue, separating 2 ends– Ischemia from

spasm spasm

• Atrophy

• Corticosteroids– In early stages

shown to inhibit healing

• Keloids or hypertrophic scars

• Infection

• Health, Age and nutrition

Healing Process-Ligament Sprains

• Tough, relatively inelastic band of tissue that connects bone to bone– Stability to joint

– Provide control of one articulating bone to another during movement

– Provide proprioceptive input or sense of joint position through mechanoreceptors

• 3 Grades of lig. tears


• Physiology– Inflammatory phase-loss of blood from damaged

vessels and attraction of inflammatory cells

– During next 6 weeks-vascular proliferation with new capillary growth and fibroblastic activity

• Immediately to 72 hours– If extraarticular bleeding in subcutaneous space– If intraarticular bleeping occurs in inside joint capsule


• Essential that 2 ends of ligament be reconnected by bridging of clot– Collagen fibers initially random woven pattern with

little organization– Failure to produce enough scar and of ligament to

reconnect 2 reasons ligaments fail

• Maturation– May take 12 months to complete– Realignment/remodeling in response to stress and

strains placed on it


• Factors that effect healing– Surgery or non surgical approach

• Surgery of extraarticular ligaments stronger at first but may not last over time

• Non surgical will heal through fibrous scarring , but may also have some instability

– Immobilization• Long periods of immobilization may decrease

tensile strength weakening of insertion at bone• Minimize immobilization time• Surrounding muscle and tendon will provide

stability through strengthening and increased muscle tension

Healing Process-Cartilage

• Cartilage– Rigid connective tissue that provides support

• Hyaline cartilage: articulating surface of bone

• Fibro cartilage: interverterbral disk and menisci. Withstands a great deal of pressure

• Elastic cartilage: more flexible than other types-auricle of ear and larynx


• Physiology of healing– Relatively limited healing capacity

• Dependant on damage to cartilage alone or subchondral bone.

• Articular cartilage fails to elicit clot formation or cellular response

• Subchondral bone can formulate granulation tissue and normal collagen can form


• Articular cartilage repair– Patients own cartilage can be harvested and

implanted into damages tissue to help form new cartilage

– Promise for long term results

• Fibrocartilage/Menisci– Depends on where damage occurs– 3 zones of various vascularity

• Greater that blood supply better chance of healing on own

Healing Process-Bone

• Similar to soft tissue healing, however regeneration capabilities somewhat limited– Bone has additional forces such as torsion,

bending and compression not just tensile force– After 1 week fibroblast lay down fibrous collagen– Chondroblast cells lay down fibrocartilage creating

callus– At first soft and firm, but becomes more firm and

rubbery– Osteoblast proliferate and enter the callus

• Form cancellous bone and callus crystallizes into bone

Healing Process-Bone

• Osteoclasts reabsorb bone fragments and clean up debris– Process continues as osteoblast lay down new

bone and osteoclasts remove and break down new bone

• Follow Wolfs law-forces placed on callus-changes size, shape and structure

• Immobilization longer 3 to 8 weeks depending on the bone

Healing Process-Muscle

• Similar to other soft tissue discussed– Hemorrhage and edema followed by phagocytosis to

clean up debris– Myoblastic cells from in the area and regenerate new

myofibrils– Active contraction critical to regaining normal tensile

strength according to Wolff's Law– Healing time lengthy-Longer than ligament healing

• Return to soon will lead to re-injury and become very problematic

• 6-8 weeks?

Healing Process-Tendon

• Not as vascular as muscle– Can cause problems in healing– Fibrous union required to provide extensibility

and flexibility• Abundance of collagen needed to achieve good

tensile strength• Collagen synthesis can become excessive can

result in fibrosis: adhesions from in surrounding structures

– Interfere with gliding and smooth movement– Tensile strength not sufficient to permit strong pull for

4 to 5 weeks» At risk of strong contraction pulling tendons ends

apart

Healing Process-Nerve

• Nerve cell is specialized and cannot regenerate once nerve cell dies– Injured peripheral nerve- nerve fiber can

regenerate if injury does not affect cell body

– Regeneration is very slow 3-4 mm /day• Axon regeneration obstructed by scar formation

• Damaged nerve within CNS regenerate poorly compared to peripheral nervous system

– Lack connective tissue sheath and nerve cells fail to proliferate

Rehabilitation philosophy• Choose therapeutic exercises/modalities that

facilitate healing process at specific phases– Stimulate structural function and integrity of injured

part– Positive influence on the inflammation and repair

process to expedite recovery of function– Minimize early effects of inflammatory process

including pain, edema control, and reduction of muscle spasm.

• Produce loss of joint motion and contracture

– Finally concentrate on preventing reoccurrence of injury by assuring structural stability of injured tissue

• Appropriate return to play guidelines

muscle injury , inflammation & repair

Health & Medicine