Principles of Orthopedic Surgery II (3) Flashcards
Dr. Gilley
What are external skeletal fixations?
- versatile
- not indicated for articular fractures
- rarely used for pelvic and spinal fractures
- good for stabilization after closed reduction of comminuted fractures
- can be adjusted
- functional period for external fixators
What are linear external fixations classified by, frame-wise?
number of planes occupied by frame
number of sides of limb from where fixation protrudes
What are the common frames in linear external fixators?
- unilateral-uniplanar (type Ia)
- unilateral-biplanar (type Ib)
- bilateral-uniplanar (type II)
- bilateral-biplanar (type III)
Review the types of common external fixator frames
What are the characteristics of type III: bilateral-biplanar?
- type II + Ia (montage)
- interconnected for strength
- stiffest configuration
Type of external fixator?
type 3
What is this?
external fixator bandaged - 24 hr completely covered
- cast padding in between spaces
Where do you place pins with external fixators?
A. Half pins - penetrate both cortices but only one skin surface
B. Full pins - penetrate both cortices and skin surfaces
What are the types of pins?
Types of fixation pins?
What are the types of linkage devices to hold fixator pin to connecting bar?
- joint fixation pins - to connecting bats, connecting bars to each other
How do you increase the strength and stiffness of external fixators?
What is the maximum amount of pins per bone segment in an external fixator?
up to 4 pins per bone segment
What is the maximum amount pin size in an external fixator?
up to 25% of bone diameter
How do you insert fixation pins?
What are circular external fixators used for?
- stabilizing fractures
- compressing non-unions or distracting fractures
- transport bone segments
- dynamically correct bone angular and length deformities
What are ring fixators unique for and why?
for controlled distraction of bone segments
- creates new bone formation in trailing pathways —> distraction osteogenesis
What is distraction osteogenesis?
pull bone apart, creating new bone formation in trailing pathways
What is this?
circular external fixators
What is this?
intramedullary pins (IM)
What is this?
Kirschner wires - “K” wires
What is this?
interlocking nail
When do you NOT use intramedullary pins?
radius
T/F: You can pin the radius
FALSE
What are the advantages of intramedullary pins?
- resistance to applied bending loads - equally resistant to bending loads applied from any direction
What are biomechanics disadvantages of IM pins?
- poor resistance to axial (compressive) loads
- poor resistance to rotational loads
- lack of fixation (interlocking) with bone
What do intramedullary pins have poor resistance to?
rotational or axial (compressive) loads & lack of fixation (interlocking) with bone
What do intramedullary pins require?
require supplementation with other implants
What support do cerclage wire, external fixator, or plate provide?
rotational & axial support
Types of IM pins?
left: chisel
right: trocar
What are the concepts for applying IM pins - cerclage wire?
pin sized 60-70% of medullary canal width
What are the concepts for applying IM pins - external fixator?
select pin sized 50% to 60% of medullary canal width
What are the concepts for applying IM pins - bone plate?
select pin sized 40-50% of medullary canal width
Regarding IM pin application, how can it span the long bone in the humerus and femur?
retrograde
normograde
Regarding IM pin application, how can it span the long bone in the tibia?
normograde pin insertion
What is normograde placement of IM pins in the femur?
insert pin to enter bone proximally in craniolateral trochanteric fossa
direct caudally - glide along caudal cortex and seat in cauvocentral aspect of condyle
What is retrograde placement of IM pins?
- insert pin in marrow cavity at fracture surface
- force shaft of pin against caudomedial cortex
- reduce fracture and drive pin distally
How are Steinmann pins or Kirschner wires used?
used as crossed pins (wires) or placed in triangulated pattern
What are interlocking nails?
placement of interlocking nail in femur
- innovative animal products (old)
- I-Loc biometrix
What does this depict?
interlocking nails
When are interlocking nails indicated?
- stabilizing simple and comminuted mid-diaphysial femoral fractures
- resistance to bending, rotational, and axial loading forces
- effective IM fixation to bridge non-reducible fractures
What do interlocking nails provide resistance to?
- bending
- rotational
- axial loading forces
How are interlocking nails secured?
secured by proximal and distal transfixing screws
- engage bone to nail
- provide axial, bending, and torsional stability
What are key concepts for applying interlocking nails?
- largest nail that fits bone
- span length of bone with nail
- ream medullary canal with Steinmann pin
- insert nail in normograde fashion
Wat is orthopedic wire used as?
used as cerclage wire or hemicerclage wire
- used in combination with other orthopedic implants
supplements axial, rotational, and bending support of fractures
What is cerclage wire?
orthopedic wire placed around circumference of bone
What is hemicerclage wire?
wire placed through predrilled holes in bone
What is the effect of combining cerclage wire and K-wires?
prevents wire slipping where bones diameter changes
secure cerclage wires at oblique angle to long axis of bone
Which implant is the most misused and causes significant percentage of post-operative complications in veterinary patients?
cerclage wire
What are the characteristics of cerclage wire?
- provides stability to anatomically reconstructed long oblique or spiral fractures
- hold multiple fragments in position
When does cerclage wire function as a stabilizer?
- wire must compress between fracture surfaces
- prevents fragments from moving or collapsing under weight-bearing loads
What are 3 criteria of cerclage wire?
- length of fracture 2-3x diameter of marrow cavity
- maximum of two fracture lines - no more than 2 main segments and 1 large butterfly fragment
- fracture anatomically reduced
If the criteria is met for cerclage wire, what does it do?
- provides additional stability
- by generating compression between fragments to hold in place during healing
What are properties of cerclage wire?
- always supported by additional implats
- if >2 or 3 bone segments present or if fracture lines not sufficient enough
Cerclage wire is only used to hold ______
fragments in position
Why does cerclage wire fail most commonly?
try to gain stability with cerclage wire in multifragmented fractures
What are concepts for applying cerclage wire?
- only anatomically reconstructed long oblique or spiral fractures
- place 2 to 3 cerclage wires per fracture line
- place wires perpendicular to long axis of bone
- space wires 1/2 to 1 bone diameter apart
What are examples of fractures where cerclage wire is useful?
long oblique
spiral
What is the spacing of cerclage wire with fractures?
> 5mm from fractures ends
- spaced 1/2 to 1 times diameter of bone
What is the application of cerclage wire?
A. twisting wire ends by hand
B. needle holders twist and tighten wire by pulling and twisting
C. tighten and cut wire 3 mm from start of twist
D. OR, cut wire 5 to 7 mm from twist & bend in direction of the twist
What are applications of cerclage wire?
A. twisting wire ends by hand
B. needle holders twist and tighten wire by pulling and twisting
C. tighten and cut wire 3 mm from start of twist
D. OR, cut wire 5 to 7 mm from twist & bend in direction of the twist
When is hemicerclage wire used?
when fracture length <2x bone diameter
What is the purpose of a tension band?
convert distractive tensile forces into compressive forces - helps with avulsion fractures
What do tension bands help with?
avulsion fractures
What is this mechanism?
tension band wiring - tightening wire exerts force
counters force of muscle contraction & compresses fracture surface
What are concepts for applying tension band wires?
- 2 K-wires or small steinmann pins
- place wires parallel to each other and perpendicular to fracture
- seat wires opposite cortex
- place hole for wire same distance below fracture as pins are move fracture
- tighten fire in direct contact with bone
What are bone plates and screws ideal for?
complex or stable fractures - when prolonged healing is anticipated
What are bone plates used as?
- compression plate
- neutralization plate
- bridging plate
What is a compression plate used for?
transverse fractures
What is a neutralization plate used for?
to support long oblique fractures reconstructed with lag screws
What are bridging plates used for?
combined with IM pin to span a non-reducible fracture
Types of bone screws?
What is the function of neutralization plates?
protects reconstructed bone from torsional, bending, and shearing forces
What are the functions of bridging plates?
- serves as a splint for spatial alignment of bone during healing
- plate and screws carry ALL applies loads during early post-operative period
What do bridging plates result in?
greater stress on bone screws than compression of neutralization plates where applied loads are shared with bone
What is the function of a buttress plate?
prevents collapse of adjacent articular surface
What are locking plates?
screws secure in bone and plate
What are the indications of locking plates?
- alignment must be correct before securing plate
- if use combination of standard screws and locking screws - plate should conform to bone & standard screws applied first to pull bone to plate
Ortho equipment?
locking plates
Ortho equipment?
locking plates
What are concepts for applying bone plates?
What are lag screws?
compress fracture line between 2 bony fragments
How should lag screws be oriented?
perpendicular to fracture line
bisect angle: lag screw placed between lines 90 degree to prevent slipping
What is a glide hole?
hole equal in diameter to outside diameter or thread diameter of screw
What is a thread hole?
hole equal in diameter to inner core diameter or shaft of screw
How do you place lag screws?
What are key concepts for applying lag screws?
How do you insert partially threaded cancellous bone screw?
