MSK 3 ESF Fracture healing plates Flashcards
What are the four main types of Linear ESFs?
- Type 1a – half pins from 1 side of bone only – uniplanar
- Type 1b – 2 x Type 1a – biplanar unilateral
- Type 2 – full pins and connecting bars each side of the bone - uniplanar and bilateral
- Type 3 – combination of Type 2 and Type 1a, strongest and stiffest.
What factors influence the choice of ESF type on the tibia?
Soft tissue structures are mostly caudal and lateral on the bone, while the craniomedal aspect is superficial with little soft tissue coverage, making it ideal for pin placement.
Type 1a and 1b are commonly used in tibias.
List ways to maximize the pin/bone interface. (Esfs)
- Pin Type: threaded > smooth pins
- Pin size: threaded portion 20-30% of bone diameter
- Pin placement: central placement through widest part of the bone available
- Appropriate pre-drilling – drill hole 0.1mm smaller than pin
- Low speed insertion <300rpms
- Proper insertion force
How can stability be increased in pin configurations?
- Correct number of pins: 3-4 per fragment
- Decrease the pin working length; place clamp with bolt no more than 1cm from skin
- Pin configuration/frame stiffness – far-near-near-far pin placement
- Consider multiplanar frames
- Consider augmentation with articulations, diagonals, + IM pin or IN
Explain the concept of staged disassembly in EFS.
Staged disassembly is used in some fractures to avoid disturbing the hematoma necessary for bone formation while allowing for progressive destabilization to increase bending strength over time.
Timing and degree of destabilization depend on patient biology, fracture mechanics, and logistical factors.
What are the pros of ESF placed closed?
- Maintains biological envelope, preserving the hematoma
- Reduces damage to local blood supply
- Flexibility in pin placement
- Frame can be removed in a staged fashion
- Open wounds can be managed daily
- Always accessible and adjustable
- Frequent adjustments for limb deformities
- No long-term implant irritation
What are the cons of ESF placed closed?
- Increased risk of infection
- Large bending forces on fixation pins
- Not intended for long-term use
- Holes of pins may create areas of weakness
- Requires diligent management
- Can cause discomfort to the patient
What are the pros of closed plating with DCP in bridging fashion?
- Takes all load sharing across the fracture
- Reduced risk of healing complications
- More comfortable for the patient sooner
What are the cons of closed plating with DCP in bridging fashion?
- More damage to biology/blood supply
- Implant can act as a nidus for infection
- Risk of catastrophic fracture if improperly sized or positioned
What are the key steps in surgical approach to acetabular fracture for key exposure?
- Osteotomy of the greater trochanter
- Incise joint capsule + additional incision parallel to acetabular rim
- Use bone holding forceps for lateral distraction of the proximal femur
- Use Kern bone holding forceps to hold the ischial tuberosity
Define neutralization plating.
Plates that neutralize bending and rotational forces to protect lag screw fixation, often used after lag screws reduce an oblique diaphyseal fracture.
What is bridge plating?
Plates that bridge across multifragmentary long bone fractures, providing relative interfragmentary stability without disturbing the fracture site.
What is buttress plating?
Also known as anti-glide plates, used to supplement lag screw fixation of metaphyseal shear or split fractures.
How does a bone screw lock into a plate?
Locking screws engage with a thread on the plate, allowing for fixed angle stability without relying on bone/plate contact.
What is the mechanism of load transfer for locking plates compared to conventional non-locking plates?
Load is transferred through the entire construct in locking plates, while non-locking plates rely on frictional force between the bone and plate.
What are the indications for stabilizing pelvic fractures in cats?
- Not weight bearing
- Articular fractures
- Narrowing of the pelvic canal by 50% or more
- Bilateral fractures
- Pubic fracture repair with prepubic tendon avulsion
- Worsening displacement on sequential radiographs
What is the function of the lumbosacral trunk in pelvic injuries?
It becomes the sciatic nerve, and its function can be evaluated through the withdrawal reflex.
What are the principles of articular fracture repair?
- Accurate anatomical reduction
- Rigid fixation
- Early mobilization
What are the advantages of using an IM pin and plate?
- Minimally invasive technique
- Reduced cost of IM pin
- Increased stability
- Reduces plate strain
- Improves overall stiffness of construct
- Establishes bone length
What are the disadvantages of using an IM pin and plate?
- Disrupts fracture hematoma
- Migration risk of IM pins
- Potential sciatic nerve damage
- Difficult removal in case of infection
What is the difference between normograde and retrograde application of an IM pin?
Normograde: pin starts outside the bone; Retrograde: pin starts at the fracture site and advances out.
How much of the IM cavity can a pin take up when using both IM pin and plate?
35-40% if using a combined plate/rod.
What type of stress is created during axial loading or bending in a locking plate construct?
Shear stress is converted to compressive stress at the screw/bone interface
This conversion helps in load distribution across screws.
What is the weakest part of the plate/screw/bone construct?
The shear strength of the interface between bone and screw
This interface is critical for the stability of the construct.