Nonunion Flashcards by Anisia Peters

What is nonunion

Absence of healing across two opposing bony surfaces
- may be the result of fracture, osteotomy, arthrodesis

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Is nonunion chronic or acute condition

Chronic

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What are some symptoms of non-union

Pain
Deformity
Instability

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What is Campbell’s Operative Orthopedics Timeframe for nonunion

6 month timetable to differentiate delayed versus non-union

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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

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What is the rate of non-union in young triple arthrodesis patients

2-3%

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What is the rate of nonunion in adult triple arthrodesis patients

17-30%

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What is the rate of nonunion in calcaneocuboid joint fusions

~30%

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What is the rate of nonunion in Talonavicular fusions

~20%

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What is the rate of nonunion in ankle fusions

~40%

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What is the rate of nonunion in 1st MTPJ and 1st TMTJ

<10%

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What is the Weber & Cech Classficaiton

considers osteogenic potential in non unions

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What are the 2 categories of Weber & Cech Classification?

Hypervascular/Hypertrophic
Avascular/Atrophic

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What are the 3 types of hypervascular/hypertrophic weber & Cech classification

Elephant’s foot
Horse’s hoof
Oligotrophic

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What are the 4 types of avascular/atrophic nonunions

torsion wedge
comminuted
defect
atrophic

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What is the treatment guidelines for hypervascular/hypertrophic Weber & Cech

There is the potential to heal conservatively

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What is the treatment guidelines for avascular/atrophic Weber & Cech?

Usually requires surgical intervention

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Describe the hypervascular/hypertrophic Weber and Cech

Continuing proliferation of blood vessels at the fracture ends - enough biological activity to promote callus formation/healing

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Describe the Elephant’s foot vascular supply

rich in vascular supply, viable bone with an abundance of callus formation

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What does elephant’s foot results from

Results from premature weight bearing or insufficient fixation

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What does the elephant’s foo require to facilitate union

Requires improved stability

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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

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What dies horse’s hoof results from

Fatigue of internal fixation

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Describe the bone ends in Oligotrophic hypervascular/hypertrophic Weber & Cech

Viable bone ends, but callus is minimal or absent

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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

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

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