Nonunion Flashcards
What is nonunion
Absence of healing across two opposing bony surfaces
- may be the result of fracture, osteotomy, arthrodesis
Is nonunion chronic or acute condition
Chronic
What are some symptoms of non-union
Pain
Deformity
Instability
What is Campbell’s Operative Orthopedics Timeframe for nonunion
6 month timetable to differentiate delayed versus non-union
What is the FDA timeframe for a non-union
Established when a minimum of 9 months has elapsed since the injury, and the fracture site shows no visibly progressive signs of healing for a minimum of 3 months
What is the rate of non-union in young triple arthrodesis patients
2-3%
What is the rate of nonunion in adult triple arthrodesis patients
17-30%
What is the rate of nonunion in calcaneocuboid joint fusions
~30%
What is the rate of nonunion in Talonavicular fusions
~20%
What is the rate of nonunion in ankle fusions
~40%
What is the rate of nonunion in 1st MTPJ and 1st TMTJ
<10%
What is the Weber & Cech Classficaiton
considers osteogenic potential in non unions
What are the 2 categories of Weber & Cech Classification?
- Hypervascular/Hypertrophic
- Avascular/Atrophic
What are the 3 types of hypervascular/hypertrophic weber & Cech classification
- Elephant’s foot
- Horse’s hoof
- Oligotrophic
What are the 4 types of avascular/atrophic nonunions
- torsion wedge
- comminuted
- defect
- atrophic
What is the treatment guidelines for hypervascular/hypertrophic Weber & Cech
There is the potential to heal conservatively
What is the treatment guidelines for avascular/atrophic Weber & Cech?
Usually requires surgical intervention
Describe the hypervascular/hypertrophic Weber and Cech
Continuing proliferation of blood vessels at the fracture ends - enough biological activity to promote callus formation/healing
Describe the Elephant’s foot vascular supply
- rich in vascular supply, viable bone with an abundance of callus formation
What does elephant’s foot results from
Results from premature weight bearing or insufficient fixation
What does the elephant’s foo require to facilitate union
Requires improved stability
Describe the bone ends of Horse’s hoof
- vocable bone ends but marked decrease in callus formation
- may appear sclerotic at the ends of the bony surfaces
What dies horse’s hoof results from
Fatigue of internal fixation
Describe the bone ends in Oligotrophic hypervascular/hypertrophic Weber & Cech
Viable bone ends, but callus is minimal or absent
Which type of the hypervascular/hypertrophic nonunion has the least biological activity
Oligotrophic
What does a Oligotrophic hypervascular nonunion results from
Poor initial apposition of osseous surfaces or distraction of the bony fragments
Describe the biologics of avascular/atrophic nonunion
Little or no vascular supply, exhibit poor osteogenic potential and are considered non viable
Describe the torsion wedge avascular nonunion
Butterfly fragment with diminished blood supply at the fracture site
- typically only unites with one side of the fracture
Describe the comminuted avascular nonunion
Multiple fragments that may exhibit necrosis and persistent gapping at the fracture site
Describe the Defect Avascular nonunion
- complete loss of bone substance within the fracture site, significant gapping at fracture site
- due to distance, it is hard to for bone to heal, therefore, union is only possible with replace of bone
What dies Defect nonunion results from
Excessive bone resection ie infection, open fracture
What is an example of a surgery that can result in Defect nonunion
Brachymet
Describe atrophic avascular nonunion and what it results from
Results from necrosis of a fragment with fibrous tissue filling the void
- partial absorption of osseous surfaces (rounded of ends), osteoporosis, atrophy
Which type of non-union is also known as pseudoarthrosis
Atrophic
What is pseudoarthrosis
False fluid and tissue filled space between two fracture fragments
What is primary bone healing
- direct, surgical intervention/ apposition of bone or joint
Does primary bone healing have a callus formation stage
No
What is secondary bone healing
- indirect, conservative management
- initial connective/fibrous tissue bridge, replaced by bone
Is there callus formation in secondary bone healing
Yes
Is there motion present in secondary bone healing
Yes
What are the steps in primary bone healing
- anatomic reduction
- stable fixation
- cutting cones
What is anatomic reduction
Osseous surfaces need to be in direct contact
Why is stable fixation required
To resist deforming forces, facilitate adequate compression across the surgical site
What is cutting cones
New lamellar bone laid down along the path of osteoclasts, facilitates the ingrowth of new vasculature and the delivery of bone forming cells
During primary bone healing, how much new bone is seen after 2-3 days
One millimeter
At what rate do cutting cones advance
50-80 micro meters per day
After the union, what does the newly formed bone do
Begins the remodeling process
What are the different phases in secondary bone healing
- impaction phase
- induction phase
- inflammatory phase
- soft callus
- hard callus
- remodeling phase
How long is the inflammatory phase in secondary bone healing
Usually lasts 3-5 days from the inciting event
When does the soft callus develop
Up to 16 weeks to develop
When does the hard callus develop and how long can it last
Begin 7-10 days
Lasts up to 1-4 years
What is the remodeling phase
Immature woven bone resorted by the osteoclasts and replaced with lamellar bone by osteoblasts
What is the relationship between diabetes and bone healing
Studies show that HbA1c >7 is a risk factor for the development of complications, inducing nonunion
Relationship between smoking and bone healing
Smoking affects tissue oxygenation and impedes wound healing
What are some operative factors we have to consider in a nonunion
- inadequate joint prep - must resect all cartilage, subchondral drilling
- inadequate fixation - must be stable to avoid micro motion, chosen based on anatomic location/procedure/patient characteristics
- mal position - must have good apposition, compression helpful but not necessary
What is the clinical hallmark of nonunion
Pain, Edema, erythema
What is the standard imaging for evaluation of bony healing process
X-ray
What type of imaging is best to visualize trabeculation, and when nonunion is questionable on X-ray
CT
What type of imaging is used when vascular it’s is questioned regarding a non-union
MRI
What type of imaging is 100% sensitive for AVN
MRI
What represents hypertrophic nonunion on bone scan
Hot spot - dark colored, increased uptake
What resents atrophic non-union n a bone scan
Cold spot, lighter colored
What type of treatment do you recommend if you suspect delayed union and why
Conservative NWB, immobilization treatment, to avoid progression to nonunion
What is the piezoelectric property of bone stimulation
Electrical potentials that occur within a bone with an external force is applied
What are the two types of bone stimulation
Internal
External
What type of current is used with internal bone stimulation
Direct current
What type of surgery is internal bone stimulation used for
Revisional surgery
Where is the cathode and anode placed in internal bone stimulation
Cathode - at nonunion site
Anode - in nearby subcutaneous
What are the 3 types of external bone stimulation
- capacitive coupling (CC)
- pulsed electromagnetic fields (PEMF)
- low-intensity pulsed ultrasound (LIPUS)
Describe capacitive coupling bone stimulation
Low voltage
Alternating/oscillating current
Electrode pads applied on either side of nonunion
24 hours a day
What are some disadvantages of capacitive coupling
Compliance
Skin irritation
Describe PEMF bone stimulation
Broad field
Low level current
Wire coil transducer
3-10 hours a day
What is one benefit of PEMF bone stimulation
Can be used over cast/splint
Describe LIPUS bone stimulation
- mechanical signal creates micro motion at nonunion site
- 20 minutes a say
- must be in contact with the skin
- depends on stable fixation, minimal gapping
- most commonly used one nowadays
What is the paprika sign?
Bleeding through medullary bone after joint prep
What type of bone graft do you need for nonunion
Autogenous bone graft
