Fracture Tissue Repair: Bone Healing

• Fracture tissue repair covers different bone types, healing phases, classifications, and management of fractures.

Bone Tissue Repair

• Cortical bone makes up 80% of bone and is the tough, dense outer layer.
• Cancellous/Trabecular bone makes up 20% of bone and consists of spongy, thin plates.
• Bone injuries result from trauma (fractures), infection, infarction, adverse responses to prostheses, inflammatory conditions, tumors, metabolic conditions, and systemic conditions.

Bone Cells

• Osteoblasts produce the bone matrix and initiate mineralization of the periosteum and endosteum
• Osteoclasts are phagocytic bone cells that resorb bone.
• Osteocytes detect local mechanical loading and signal osteoblasts to initiate remodeling
• Osteoprogenitor cells are stem cells that develop into osteoblasts

Fracture Healing Phases

• Hemostasis involves the formation of a fracture hematoma, which brings fibroblasts, platelets, and osteoprogenitor stem cells to the site
• Inflammatory phase (weeks 2-6) involves a fibrin scaffold forming between the ends of the fracture.
• Reparative phase (weeks 6-12) involves bone growth factors.
  • A callus forms and transforms through endochondral ossification.
  • Soft callus (days to 3 weeks) consists of granulation tissue and fibrocartilage.
• Hard callus (2-12 weeks) is made of osteoblasts.
• Bridging on radiograph offers evidence of healing.
• Remodeling phase takes months to years:
  • Woven bone transforms into lamellar bone, increasing stability.
  • Excessive callus is reabsorbed by osteoclasts
  • Mechanical stress assists remodeling.

Fracture Classifications

• Fractures can be classified as complete or incomplete, displaced or non-displaced, and open or closed
• The number of pieces the bone is broken into is also a factor (comminuted).
• The Salter-Harris classification is used for pediatric fractures.

Fracture Healing Timeline

• Children typically heal in 4-6 weeks.
• Adolescents heal in 6-8 weeks.
• Adults heal in 10-18 weeks.
• Abnormal conditions include malunion and nonunion

Types of Fractures

• Traumatic fractures occur from significant impact.
• Stress or fatigue fractures happen due to repetitive stress.
• Insufficiency fractures occur due to normal stress on abnormal bone.
• Pathologic fractures happen because of disease processes weakening the bone.

Fatigue Fractures

• Fatigue fractures occur when normal bone is exposed to repeated abnormal stress, such as in the tibia, metatarsals, femoral neck, or spine.
• Two Types:
  • Compressive: running, marching, gymnastics.
  • Distractive: result of muscle pull (throwing, golf).
• Can result from being a long-distance runner or military personnel
• Risks include the female athlete triad, poor muscle endurance, and a sedentary lifestyle with a sudden increase in activity
• Initial symptoms are painless, but progress to pain during activity and eventually constant pain.
• Diagnosed via bone scan, and sometimes are if radiograph (-)
• Treatment includes immobilization and activity modification

Insufficiency Fractures

• Insufficiency fractures are caused by normal stress on abnormal bone density
• They are commonly found in vertebrae, specifically as thoracic vertebral body compression fractures
• Symptoms include respiratory issues, decreased height, and sharp pain.
• Risks include radiation, menopause, and metabolic disorders.
• Imaging is performed using radiograph and CT scans
• Treatment involves postural correction, resistance training, and bracing.

Pathologic Fractures

• Pathologic fractures occur when bone is abnormally fragile due to disease
• The most common cause is cancer metastasis
• Other causes include primary bone lesions, benign lesions, and metabolic disorders
• Activation of osteoclasts weakens the bone
• These fractures most often occur at the femoral head and neck, spine, and pelvis.

Fracture Management

• Severity of injury dictates the intervention
• Surgical intervention is often necessary for
  • Unstable
  • Displaced
  • Comminuted
  • Open fractures
• Surgical options include open reduction internal fixation (ORIF) and joint arthroplasty
• Conservative treatments include casting, immobilization, possible limited weight-bearing, and physical therapy

Immobilization Effects

• Muscle: Atrophy, decreased strength, contracture
• Bone: Osteopenia
• Tendons/Ligaments: Disorganization of parallel cells, increased deformation with standard load or compression
• Ligament Insertion Site: Ligaments not attached to bone, reduced load to failure
• Cartilage: Adherence of connective tissue leading to decreased thickness
• Meniscus: Adhesions of synovium, decreased synovial fluid
• Joint: 0-12 weeks decreases ROM, increased intra-articular pressure; force required for flexion/extension increases significantly after 12 weeks

Healing Errors

• Decreased Bone Mineralization causes Fracture
• Inappropriate Collagen causes Tendinopathy
• Scar Tissue causes
  • Muscle Contracture
  • Decreased Tensile Strength
  • Fibrosis
• Increased Osteoblasts
  • Heterotopic ossification
  • Myositis ossificans

Heterotopic Ossification/Myositis Ossificans

• Defined as formation of bone in non-skeletal tissue after burns, trauma, surgery, or injury to the CNS
• Interventions:
  • NSAIDs
  • Radiation therapy
  • Surgery
  • Conservative care includes PROM, gentle self-stretch, and avoid aggressive stretching

Explores bone tissue repair, covering cortical and cancellous bone, bone cells (osteoblasts, osteoclasts, osteocytes), and fracture healing phases. Discusses the processes involved in hemostasis and inflammation during bone repair.