Chapter 20.1 Delayed Unions Flashcards
What is the difference between an excellent and a poor outcome in fracture repair often attributed to?
The difference is sometimes a matter of mere details.
What is a delayed union?
A delayed union is a fracture that takes longer to heal than anticipated.
What factors determine the rate and extent of fracture healing?
The biological and mechanical environments.
What is essential for fracture healing?
Adequate vascularity of the bone and soft tissues.
What usually causes inadequate vascular supply in fracture healing?
Soft-tissue trauma.
What is a sequestrum?
A piece of dead bone surrounded by an involucrum.
An involucrum is a layer of new bone growth that forms around a sequestrum (a piece of dead bone) in response to infection, particularly in cases of chronic osteomyelitis.
What happens if a bone is deprived of its vascular supply?
It may become a sequestrum.
What can result from inadequate fracture fixation?
Development of a delayed union or even a nonunion.
What can high interfragmentary strain prevent?
Progression from granulation tissue to fibrocartilage and eventually bone.
What may cause implants to be unstable?
They may be undersized or have insufficient bone–implant contact.
What type of pins should be used in a linear external fixator for long-term stability?
Threaded pins.
How does stability differ from rigidity in fracture fixation?
Stability refers to the ability to maintain position, while rigidity refers to the inability to move.
What factors can be classified as responsible for the development of a delayed union?
- Initial trauma
- Contamination
- Vascular insufficiency
What happens to the vascular supply when kinetic energy from a traumatic insult is high?
The damage to the vascular supply increases, leading to a higher likelihood of necrosis and infection.
What is a typical example of a high-kinetic energy injury?
A gunshot wound with high-speed pellets.
What can occur if asepsis is not practiced in an open wound with devitalized tissues?
It is easily contaminated with highly resistant pathogens.
Delayed unions may be caused by _______.
- vascular insufficiency
- fracture instability
- inadequately chosen or applied implants.
What is the most important feature of the mechanical environment of a fracture?
Stability
Stability is crucial to prevent delayed union or nonunion.
What type of tissue forms initially at a fracture site?
Granulation tissue
- Granulation Tissue tensile force up to 0.1 Nm/mm2.
- Early Soft Callus tensile force is 4–19 Nm/mm2
- Ultimate tensile strength of compact bone is 130 Nm/mm2
This may progress to fibrocartilage and eventually bone as strain decreases.
What factors can lead to unstable implants?
- Undersized implants
- Insufficient bone–implant contact
- Inappropriate selection of fixation devices
Examples include too small plates or inadequate size pins.
What is a potential issue with using a linear external fixator for a highly comminuted fracture?
Insufficient bone–implant contact
This occurs when only two pins are used for each fracture segment.
What type of pins should be used for long-term stability with a linear external fixator?
Threaded pins
They are stronger and provide better bone purchase than smooth pins.
Circular external fixator provides stability or rigidity?
The circular external fixator provides stability but not rigidity due to its tensioned cross wires.
Stability allows for micromotion, while rigidity does not
What are the factors responsible for the development of a delayed union?
- Initial trauma
- Contamination at the site of the accident
These factors can lead to complications such as necrosis and infection.
How does kinetic energy from trauma affect fracture healing?
Higher kinetic energy results in greater damage to vascular supply
This increases the likelihood of necrosis and infection.
What is a typical example of high kinetic energy trauma?
Gunshot wound with high-speed pellets
This can cause cavitation and extensive tissue disruption.
What is a risk associated with comminuted, highly unstable fractures during transportation?
Creation of avascular bone fragments
Detached fragments may become sequestra due to loss of vascular supply.
Which types of fractures are particularly prone to becoming open fractures?
Long oblique and spiral fractures
Sharp points of their bone ends can penetrate the skin.
Which metabolic conditions can delay fracture healing?
Primary hyperparathyroidism
Hyperadrenocorticism
Diabetes mellitus
Hyper- and hypothyroidism
Growth hormone deficiency
Renal disease
Hepatobiliary disease
Intestinal malabsorption
These conditions are important to consider in treatment.
What nutritional deficiencies are associated with disturbed bone production?
- Calcium and phosphorus imbalance
- Vitamin A and D deficiency
- Vitamin K and copper deficiency
These deficiencies can affect healing and bone health.
Which drugs can interfere with bone healing?
- Corticosteroids
- Anti-convulsants
- Antineoplastic agents
Awareness of these medications is crucial during treatment.
Why is well-vascularized bone important in fracture healing?
It heals more rapidly and has greater resistance to infection
Inadequate reconstruction can lead to complications.
What is intraoperative skeletal traction ?
Intraoperative skeletal traction refers to the use of traction applied to bones during surgery, often to reduce fractures or correct deformities
Helps preserve the osseous vascular supply.
Fragment manipulation necessary for anatomical reduction
What can jeopardize even well-performed surgeries?
An uncooperative owner allowing excessive exercise
Proper postoperative management is crucial for recovery.
How are delayed unions diagnosed?
Through serial clinical and radiographic evaluations
These evaluations assess the progression of bone healing.
What is the diagnosis of a delayed union based on?
A quantitative judgment based on the expected rate of healing
Factors such as age, type of bone, and biomechanical environment are considered.
What should be evaluated postoperative for boney healing?
Both clinical and radiographic evaluations
Neither method alone provides definitive information.
What clinical signs may suggest a delayed union?
Increased pain or decreased use of the limb
Instability of the fracture is usually not evident unless related to implant issues.
What should be expected within a few days after surgery regarding joint assessment?
The animal should tolerate assessment of range of motion of proximal and distal joints
Articular fractures may require longer before movement can occur without pain.
When should radiographic examinations be scheduled to assess fracture healing?
Immediately postoperative, after 7-10 days, after 25-30 days, and after 2 months
Additional checks may be scheduled if healing is slower than expected.
What can mask the appearance of an active callus on radiographs?
Incorrect exposure with too high a kV
This can obscure delicate callus formation if imaging is done too early.
What is the radiographic appearance of a delayed union compared to normal healing?
The same, but changes occur at different time points
A persistent fracture line with some nonbridging callus is characteristic.
What are the types of ossification involved in the healing process?
- Intramembranous ossification (surface of collagen fiber bundles)
- Endochondral ossification (surface of fibrocartilaginous areas)
Osteoblasts deposit osteoid depending on local metabolic conditions.
How can vascularity of delayed union be assessed?
Using Doppler flow or ultrasound Doppler
Assessing bone vascularity is more challenging.
What is the general treatment approach for delayed unions?
Extended confinement time and continue monitoring bone healing.
What is generally preferred when dealing with delayed unions?
Continuing or augmenting the technique used originally.
What should be done if there is doubt in managing delayed unions?
Replace external coaptation with an osteosynthesis technique.
Under what conditions may the animal be confined for a further period without reoperation?
If fracture stability and vascularity are thought to be satisfactory.
What should be done if implants are loose or broken?
They should be removed and the fracture stabilized appropriately.
What is strongly recommended if implants are loose or broken?
Add autogenous bone graft.
How can a weak plate be reinforced?
Linear external fixator to counteract excessive bending and/or rotational forces.
What can be done to reinforce a weak linear external fixator?
By adding more threaded pins and/or a second connecting bar.
What may stimulate bone healing when animals are treated with external fixators?
Destabilizing the construct.
