Changes In Tissue During Injury, Immobilization,and

Remobilization

Part I: Review

• Identify Normal Connective Tissue

• Components of Normal Connective Tissue

• Collagen and Elastin

• Proteoglycans & Water

• Fibroblasts and Chondrocytes

• Soft Tissue Changes Following Injury

Normal Connective Tissue

• Characterized by intercellular material– Glycoprotein fibers– Protein polysaccharide ground substances– Other cells

• Functions– Provide nourishment for overlying epithelial

tissue– Link muscle & bone as tendons– Allow movement

Categories of Connective Tissue

• Loose Connective– Areolar: most abundant in the body– Adipose: fat (in the body, not the head)– Reticular: framework of branching fibers;

found in lymph, bone & liver

• Dense Connective– Collagenous & elastic fibers– Tendons , ligaments & skin

Components of Normal Connective Tissue

• Extracellular Components– Collagen, Elastin, Reticular fibers – Provide the matrix of connective tissue– Water & Glycosaminoglycans (GAG)– Provide lubrication & spacing between collagen

fibers

Components of Normal Connective Tissue

• Cellular Components– Fibroblasts & Chondrocytes

• Provide material for the matrix

Collagen Flow Chart

Collagen synthesized by Fibroblast

Procllagen 3 chain of

amino acids

Tropocollagen molecule

building blocks

Fibrils Fibers

Tendon ligaments

Skin

Clinical Implications For Understanding Collagen Tissue

• In mature collagen the intermolecular cross-linking is strong.

• In newly formed collagen the cross links are weak and can easily be pried apart.

• Avoid excessive force with mobilization in the early healing stages.– Tendency to damage cross links: can cause

mechanical weakness of the tissue.

Collagen Fiber Arrangement

• Tendons: parallel – Provide stiffness & strength with a

unidirectional load

• Ligaments: Looser, different directions– Multidirectional

• Skin: random arrangement– Stretching

Proteoglycans & Water• Form ground substance

• Gel like: provide spacing & lubrication between collagen microfibrils

• Hydrophilic: draws water into tissue

• Water is necessary for diffusion of molecules through tissue (exportation of metabolites)

• The spacing, along w/ water, prevents adjacent fibers from linking, thereby reducing friction.

Fibroblasts & Chondrocytes

• Cellular components of C/T

• Building blocks

• Fibroblasts – Found in ligaments, tendons, fascia, joint

capsules.

• Chondrocytes– Found in the collagen matrix of articular

cartilage.

Soft Tissues Changes Following Injury

• Two types of cellular events take place in order to repair tissue:– Immunological– Reparative

Immunological

• Immediate

• Prevents bacteria from entering injured area.

• Macrophages & leukocytes

Soft Tissues Changes Following Injury

• Reparative– Initiated about 48 hours after injury.– Collagen initially held by blood clots begins to

form a weak mesh.– During this period adhesions of collagen have

little mechanical strength.– Collagen deposition

• Increases 5th day

• Peaks 14th day

• 120 days: reduction of collagen turn over

Changes With Immobilization

• Research has shown adverse effects with prolonged immobilization.

• Changes take place from cellular matrix to gross tissue levels.

• Areas affected:– Collagen matrix– Ligaments/tendons– Muscle– Periarticular & intraarticular tissues

Effects of Immobilization on Collagen Matrix

• Increase in production of collagen– Deposits in random fashion, not along the lines

of stress.

• Decrease in GAG & H2O– Causes a loss of lubrication and a closer

contact of fibers– Abnormal cross-linking

• Restricted normal interfibril gliding

Immobilization On Ligaments & Tendons

• Ligaments– Loss of strength/ stiffness at the insertion point.– Harwood et al, 1990: atrophy of the ligaments

• Tendon– Atrophy – Gelberman 1986: extensive obliteration of

space between tendon and sheath • Adhesions / impediment of glide between sheath &

tendon

Effects of Immobilization On Muscle

• 2º shortening of the muscle

• Results in a 40% reduction of sarcomeres (Lederman)

Effects of Immobilization On Periarticular &

Intraarticular Structures• Atrophy of the capsule, ligaments &

synovial membrane

• Adhesions & abnormal cross-links

• Synovial tissue: most sensitive to effects of immobilization, undergoing fibrofatty changes– Mature fibrofatty tissue will cover non-

articulating areas and form adhesions.

Adhesions, Contractions, Cross-Links, Scar Tissue & Contractures

• Adhesions: “fibrous band holding parts together that are normally separated”

• Form in tendons and sheath, and in the joint capsule.– Can be stronger than original tissue.– Watch out when performing aggressive stretching: could

avulse normal tissue.

Contraction / Cross-links

• Contraction: tightening of tissue – Myofibroblasts pulling together. Eg., Scars– ROM exercises prevent this.

• Cross-links– Chemical bonds within & between the collagen

molecules.– Reduce tissue extensibility.

Contractures/ Scars

• Contractures- – Indicate loss of movement.– Shortening of CT & muscle for increased cross

linking.– Reduced by stretching or movement.

• Scar– Changes in cell & matrix after damage.

Effects Of Mobilization On Tissue

• Connective tissue matrix– Turn-over of collagen / remodeling lines

of stress.

– Improves GAG synthesis.

– Maintains inter-fibril distance /lubrication.

– Reduces abnormal cross linking.

Effects Of Mobilization On Tissue

• Joints– Pressure fluctuations important for

formation/removal of synovial fluid.

– Vital to articular cartilage health.

• Ligaments• Greater strength

Effects Of Mobilization On Tissue

• Muscle– Muscle regeneration is dependent on longitudinal

mechanical tension provided by passive stretching.

– Research (1966/91) shows the implication of longitudinal mechanical tension in promoting parallel alignment of the myotubules to the lines of stress.

• PROM can improve ROM and increase the cross -sectional area of muscle; also the number & size of sacromeres return to preimmobilization levels.

Effects Of Mobilization On Tissue

• Tendons– Higher tensile strength; less likely to rupture.– Decrease adhesion formation.– Early mobilization produces a higher DNA and

cellular content vs delayed mobilization. – Revascularization of blood vessels.

Summary

• Movement provides:– Direction for the deposition of collagen.

– Vascular regeneration.

– Reduces excessive cross-linking and adhesions.

Considerations

• Early stages– Little mechanical strength.

– Avoid aggressive stretching.

• Remodeling phase– Strong bond.

– Can be more aggressive.

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