Delayed unions, nonunions, malunions Flashcards
What are the four tenets of bone healing?
Mechanics, scaffold, growth factors, cells
What size fracture gaps should be avoided to prevent non-union associated with too large defect size?
Defects approaching the diameter of the bone
What are the two aspects of the mechanical environment that need to be optimized to ensure uncomplicated bone healing?
- Geometric mechanical environment
- Forces and resultant motion of fracture fragments
What is the ideal strain for uncomplicated bone healing?
Varies depending on the direction of strain (tensile strain most tolerated) and the size of the fracture gap (large fracture gaps seem less tolerant of high strain than small fracture gaps). Limiting strain to less than 1% may result in stress protection. Strains of 5-10% are generally considered adequate for comminuted fractures or fractures with a small gap.
What are some negative intrinsic factors for growth factor activity?
Decreased/compromised vascularity of the periosteum, old age, sparse soft tissue attachments
What factors contribute to high cellular activity following fracture?
Thick periosteum, young age, metaphyseal bone, high vascularity, moderate hydrostatic tension
What are common mechanical and biologic causes of delayed union?
Mechanical: too large fracture gap, motion.
Biologic: intrinsic (patient factors), or extrinsic (surgeon factors)
What are the classifications of non-unions?
Viable: Hypertrophic, oligotrophic
Non-viable: necrotic, dystrophic, atrophic, defect
What is the new bone that surrounds a sequestrum called?
Involucrum
Aside from surgical fixation, growth factors and grafts, what other methods have been described to help with non-union?
Extracorporeal shock wave therapy, pulsed electromagnetic field, low intensity pulsed ultrasonography
