Therapeutic Interventions Week 4 - Flexibility and Therapeutic Exercise Framework

• The text details tissue healing mechanisms and timelines for tendons, ligaments, fibrocartilage, articular cartilage, bone, and muscle.
• It also discusses therapeutic exercise frameworks.

Tendon Healing

• Tendon healing involves three phases: inflammatory, proliferative, and remodeling.
• During the inflammatory phase (approximately 1 week), macrophage activity increases.
• Granulation tissue, including capillary buds and fibroblasts, proliferates.
• Cells digest damaged tissue, creating space for new tissue formation.
• New tissue is laid down in a laminar or perpendicular fashion and is highly vascular.
• Fibroblasts proliferate from the synovial sheath of the tendon.
• In the proliferative phase (about 1-5 weeks), fibroblasts align parallel to the lines of force.
• Collagen content increases during the proliferative phase.
• During the remodeling phase (roughly 2-4 months), collagen matures and aligns functionally.
• It is worth noting that the different phases of tissue repair may overlap spatially and temporally.

Ligament Healing

• Ligament healing also includes inflammatory, proliferative, and remodeling phases.
• The inflammatory phase lasts about 5 days, involving phagocytic cells removing damaged tissue.
• Chemicals are released to stimulate fibroblast activity.
• The proliferative phase spans from day 5 to week 6, with fibroblasts multiplying and producing extracellular matrix and collagen.
• Initially, immature collagen is randomly organized and weak, but it can resist forces as early as 2-3 weeks.
• Collagen levels reach near-normal levels by week 6.
• The remodeling phase takes place from week 4 onwards.
• Collagen becomes oriented along stress lines, resulting in a more organized structure that can resist greater stress.

Fibrocartilage Healing

• Fibrocartilage examples include the meniscus in the knee joint, and the labrum in the hip and shoulder.
• There is no spontaneous healing in the avascular zone of fibrocartilage.
• Within the vascular zone, healing occurs in three phases: inflammatory, proliferative, and remodeling.
• The inflammatory phase lasts about 1 week, during which a fibrin clot forms and macrophages destroy dead tissue.
• The proliferative phase spans from weeks 1-10, involving migration and proliferation of undifferentiated mesenchymal cells.
• The lesion fills with fibrovascular scar tissue to “glue” wound edges together.
• The remodeling phase takes place from week 10 to several months.
• Remodeling to normal-appearing meniscal fibrocartilage takes several months.

Articular Cartilage

• Chondral injuries DO NOT heal due to the absence of blood vessels, therefore no inflammatory response.
• Osteochondral injuries have the capacity to heal, because of the close proximity of blood vessels in the bone.
• Articular cartilage healing progresses through inflammatory, proliferative, and remodeling phases.
• The inflammatory phase lasts about 0-2 weeks, when blood from a bone defect extends into the cartilage and forms a fibrin clot.
• Undifferentiated mesenchymal cells migrate to the area and form new matrix.
• During the proliferative phase (2-6 weeks), the matrix consists of type II collagen, proteoglycans, type I collagen, and non-collagenous proteins.
• The remodeling phase happens from week 6 onwards.
• Tissue assumes a look somewhere between fibrocartilage and hyaline cartilage.
• Many large osteochondral defects show signs of proteoglycan depletion, fragmentation, and fibrillation by one year post injury.

Bone Healing

• Fractures heal either indirectly or directly.
• Indirect healing, also known as secondary fracture healing, is the most common type.
• It does not require anatomical reduction or rigid stability, and relies on micro-motion and weight-bearing.
• Direct healing requires anatomical reduction of fractured ends and bone ends need to be in close proximity.
• Direct healing must be stable with no gap.
• General stages of fracture healing are inflammatory, reparative, and remodeling.

Indirect Bone Healing: Inflammatory Phase

• The acute inflammatory response lasts approximately 0-7 days.
• Hematoma formation occurs between bony ends.
• Macrophage activity increases.
• Angiogenesis is promoted.
• This phase peaks in 24 hours and completes after 7 days.
• Mesenchymal stem cells (MSCs) are recruited.
• MSCs differentiate into osteogenic cells, which are necessary for new bone cell formation.

Indirect Bone Healing: Reparative Stage

• The reparative stage involves the generation of cartilaginous and periosteal callus.
• Granulation tissue forms at the site of the hematoma, and callus formation begins.
• Soft callus formation peaks in 7-9 days post-trauma.
• Revascularization and neo-angiogenesis occur at the fracture site.
• Blood vessels invade the callus.
• Mineralization and resorption of the cartilaginous callus occur.
• The soft callus is absorbed and replaced by a hard callus.
• Mitochondria accumulate calcium-containing granules.
• Hard callus formation peaks by day 14.
• The hard callus is not initially strong enough to resist normal forces, as there is no lamellar woven bone yet, but a hard callus matrix.

Indirect Bone Healing: Remodeling

• The remodeling phase entails bone remodeling.
• The hard callus undergoes a second resorptive phase.
• Lamellar bone and a medullary cavity form, 3-4 weeks post-trauma.
• Full remodeling can take years.
• Remodeling is stimulated by the piezoelectric effect, an electrical polarity caused by pressure within the crystalline structural environment.
• Small bones are generally considered healed in 3-6 weeks (children to adults).
• Large bones are generally considered healed in 8-12 weeks (children to adults).

Direct Fracture Healing

• Contact healing requires intimate contact of two fractured ends and minimal shear forces.
• Gap healing occurs if intimate contact is not available.

Explores the healing processes for different tissues: tendons, ligaments, fibrocartilage, articular cartilage, bone, and muscle. Covers the inflammatory, proliferative, and remodeling phases with specific timelines. Discusses the role of therapeutic exercise frameworks in rehabilitation.