1. Variables that Influence Fracture Healing

2. Severe soft tissue damage associated with open and high energy closed fractures Infection Segmental fractures Pathologic fractures Fractures with soft tissue interposition Poor local blood supply Systemic diseases Malnutrition Vitamin D deficiency Corticosteroid use Poor mechanical fixation

3. Injury Variables Severe open fractures – Soft tissue disruption – Fracture displacement – Significant bone loss – Management Vascularized soft tissue flaps to cover bone exposed Debriding of infected bone and soft tissue Appropriate antibiotic treatment

4. Intra-articular Fractures – Extend into joint surfaces – Challenges Unstable joint Delayed healing or non-union Joint stiffness Segmental Fractures – Two level fracture pattern impairs or disrupts the intramedullary blood supply to the middle fragment

5. Soft Tissue Interposition – Suspected when bone fragments cannot be brought into apposition or alignment during attempted closed reduction Damage to the Blood Supply – May result from a severe soft tissue and bone injury or from the normally limited blood supply to some bones or bone regions

6. Patient Variables Diseases or Disorders – Diabetes – HIV infection Age – Rate of healing declines with increasing age Decreased number and function of stem cells Decreased chondrogenic potential of the periosteum Changes in local signaling at fracture site Impaired vascularization

7. Nutrition – Cell migration, proliferation and matrix synthesis necessary to heal a frature requires substantial energy – There is a need for a steady supply of proteins and carbohydrates

8. Systemic Hormones – Corticosteroids – Thyroid hormone, calcitonin, insulin and anabolic steroids Nicotine Use – Unknown mechanism – Possible that nicotine inhibited vascularization of autogenous cancellous bone grafts

9. Tissue Variables Form of bone (Cancellous or Cortical) – Cancellous bone Large surface area creates many points of bone contact rich in cells and blood supply – Cortical bone Much smaller surface area per unit volume Less extensive internal blood supply

10. Bone Necrosis – healing depends entirely on ingrowth of capillaries from the living side or the surrounding soft tissues Bone Disease – Pathologic fractures that require less force than necessary to break normal bone – Osteoporosis, malignant bone tumors, osteomalacia, fibrous dysplasia Infection – Many cells must be diverted to wall off and eliminate the infection and energy consumption increases – Necrosis of normal tissue and thrombosis of blood vessels

11. Treatment Variables Apposition of Fracture Fragments – Decreasing the fracture gap decreases the volume of repair tissue needed to heal a fracture Loading and Micromotion – Loading a fracture site stimulates bone formation while decreased loading slows fracture healing Fracture Stabilization – Prevents repeated disruption of repair tissue – May cause nonunion