19 – Malunion, Delayed Union and Non-Union Flashcards
What are some technical errors of fracture healing?
- If the repair method chosen is insufficient to neutralize forces acting on the fracture, the repair will fail
- Issues in soft tissues as well
o Muscle atrophy
o Joint stiffness
o Tissue fibrosis
o Poor function
Quadriceps contracture
- Tends to follow delayed femoral fracture union
- Common after splinting of femoral fractures
- Might be associated with compartment syndrome
- Common in young dogs (and cats)
What is the best way to avoid quadriceps contracture?
- Make sure you have SOLIDE fracture repair and aggressive, early physical rehabilitation
- In surgery avoid causing it
What is malunion?
- Fracture healing with abnormal alignment
- Malalignment may be angular, axial, torsional or a COMBO
- May or may not be a clinical problem
- Up to 15 degrees self-correct of angular malalignment may happen over time
- Rotational malalignment DO NOT self-correct
How much femoral length is well tolerate in dogs and cats (due to malunion)?
- Up to 20%
How can you correct malunions?
- *osteotomy=making a cut in a bone
- Ostectomy=removing a piece of bone
Closing wedge osteotomy
- Many variations
o Modified cranial closing wedge osteotomy technique used for treating cranial cruciate disease
Opening wedge osteotomy
- In dogs with a lot of healing potential (NOT used in a horse)
- Make a single cut parallel with distal part and ‘pull the leg’ straight and leave the area open
>use a fixation device
-allows you to not have to shorten the bone
Oblique Osteotomy
- Cut parallel with distal joint surface and move the fragment over more (proximal fragment moved into medullary cavity of the distal fragment)
- *need great healing potential
Dome osteotomy
- Make a curve cut
- Maintain bone length and great healing
Step osteotomy
- This is a step wedged osteotomy in the picture
- *can be used to make bones longer of shorter
- Adding a wedge allows for angular correction
What is distraction osteogenesis?
- Use fixators to make corrections and support while making the bone longer or pulled into normal position
What is delayed union?
- Fracture has not healed within the expected time (ex. 3-5 months)
What is a non-union?
- No healing well beyond the expected maximal time (ex. 6 months in adult dogs and cats)
What are some causes of delayed and non-union?
- Excessive motion of fracture fragments
- Infection
- Excessive gap between fragments
- Devitalized bone
- Poor blood supply to fragments
What do vascular (hypertrophic) nonunions result from? What is present?
- INSTABILITY of the fracture site
- Callus is present, fracture edges are indistinct
How do you treat vascular (hypertrophic) nonunions?
- Rigid stabilization of the fracture
What do avascular (atrophic) nonunions result from? What is seen?
- POOR blood supply or excessive gap
- Minimal to no callus evident
- Sharp edges to bone ends, which may be sclerotic
- Osteopenia may be marked
- Bone looks like it is withering away
How can you treat avascular (atrophic) non unions?
- Encourage ingrowth of new blood vessels
- Rigid stabilization, under compression if possible
- Stimulate bone growth
How can you encourage ingrowth of new blood vessels? (avascular nonunion)
- Remove offending hardware
- Resect fibrous tissue, sclerotic bone ends from fracture sites
- Open up medullary canal (drill longitudinal holes) to encourage blood vessel ingrowth)
How can you stimulate bone growth? (avascular nonunion)
- Cancellous bone graft
- Bone morphogenetic protein or other growth factors
- Mesenchymal stem cells
- Omentum!!
- Bone transport (via distraction osteogenesis)
What is bone grafting?
- Transplantation of bone to stimulate healing or replace bone deficits
What are different types of bone grafting?
- Autografts: same animal
- Allografts: different animal of same species
- Xenografts: from other species
- Cortical vs. cancellous
Cortical bone grafts
- Used to replace big bone defects and provide physical support
Cancellous bone grafts
- Provide little to NO physical support, but stimulates healing
What do cancellous bone grafts provide? (3)
- Osteogenesis
- Osteoconduction
- Osteoinduction
Osteogenesis
- Mesenchymal precursor cells in the graft differentiate into active osteoblasts
Osteoconduction
- Graft provides a scaffold for osteoblasts to lay down new bone upon
Osteoinduction
- Growth factors in the graft recruit more cells to turn into osteoblasts and lay down new bone
How do you collect cancellous bone for a graft?
- Make a small hole in the donor bone with a pin or drill
- Use a curette to scoop out cancellous bone
- Store cancellous bone in a bloody sponge, in the dark, in a safe place until implantation
What are some places to get cancellous bone from?
- Proximal humerus
- Proximal tibia
- Femoral condyle
- Ilium (especially in cats)
- Sternum (horses and cattle and birds)
Where can you use a cancellous bone graft?
- Delayed unions and nonunions
- Long bone fractures in adult animals that you expect to heal slowly
- Places where there are bone deficits
- Osteomyelitis
- Arthrodesis
What are some bone graft substitutes?
- Injection of bone marrow into a fracture/delayed union site
- Calcium phosphate cements
- Bioglass (ex. Consil made by Nutramaxx(
- Coral
- Bone morphogenetic proteins in carrier substances
