External Fixation Flashcards
what is the ultimate goal of fracture treatment? (x2)
- early ambulation
- complete return of function
what are the 4 principles of fracture treatment, according to the AO group?
- anatomic reduction of fragments
- stable fixation (suitable to biomechanics)
- preservation of blood supply to fragments/soft tissue
- early, active pain-free mobilization of muscles and joints adjacent to the fracture
what are the objectives of fixation?
- stabilize fragments
- prevent displacement, angulation, rotation
ideally, fixation should permit the use of as many joints as possible during healing period
what does “fracture disease” mean?
phrase used to describe complications associated with fracture treatment and immobilization, such as:
* bone atrophy
* soft tissue atrophy
* nail, skin, cartilage atrophy
what is the most devastating form of fracture disease in dogs?
quadriceps muscle contracture associated with femoral fractures (young animals)
what are the 3 categories of fixation methods?
- splinting limb
- splinting bone
- compression of bone fragments
true or false: there is a certain amount of motion at the fracture site because of the inherent flexibility of devices like casts and splints.
true – and the surgeon must ensure this motion is still within limits to allow for healing callus to form
which devices are considered “coaptation fixation devices”?
external casts, splints, and bandages
how do bandages help in wound management?
bandages can:
* provide limb compression in early post-op period
* cover wounds with absorbent material
* provide support to limbs
* stretch joints
how do casts and splints differ from bandages as external coaptators/
these materials provide rigidity and may protect surgical repairs or provide support for soft tissue injuries
what is “bivalving” a cast?
it means that the cast is cut in half (cranial/caudal or medial/lateral)
doing this allows to easily inspect tissues under it and redressing without having to form another cast
what is the advantage of a moulded cast/splint compared to a commercial pre-made one?
custom fit = cause fewer soft tissue problems and are better tolerated by the patient
what is the most fundamental role of coaptation?
decrease joint motion
advantages of external coaptation:
- minimal disruption of fracture environment
- no implants at fracture site
- decreased risk of infection
do we use external coaptation in short or long term?
can be both!
short term: decrease motion of bone fragments before fracture repair
long term: decrease bone fragment motion in patients with fractures that can be managed without surgery
note that external coaptation does not neutralize all forces that may act on a fracture
what are 4 disadvantages of coaptation?
- cost of materials and labour
- decrease limb use in early post-op period (may lead to long term limb disuse)
- decrease joint motion (may promote long-term loss of motion and prolonged stiffness)
- tissue complications secondary to bandages (redness, chafing, bruising, ischemic injuries, lact of bone healing)
when do we use temporary splinting?
if there will be a delay in reduction and fixation a temporary splint of the limb should be used to reduce additional trauma and pain
especially true for:
- fractures distal to elbow/stifle
- any limb fracture where animal needs to be transported and there is risk for closed fracture to open
when do we use long-term splinting?
- closed fracture below elbow or stifle
- fractures amenable to closed reduction (without opening skin/soft tissues)
- fractures where bone will be stable after reduction relative to shortening or distraction
- fractures where bone can be expected to heal quickly so that cast/splint won’t cause fracture disease
what 3 fractures is casting suitable for?
- greenstick fractures
- long-bone fractures in young animals (periosteal sleeve intact)
- impaction fractures
all must be DISTAL to stifle or elbow
where should a splint or cast immobilize the joint to be effective?
ABOVE AND BELOW the fracture
what are 5 factors to consider when using a splint or cast?
- padding – light for soft tissues, pad valleys not mountains, shielding pressure points
- fixation – anchor cast/splint to avoid shifting on limb, mould cast to countour of limb
- radiographs – check reduction before and after a few days
- extent – expose tips of centre two toes to evaluate swelling
- tolerance – check if patient is in pain, lameness gets worse, high temp, swelling, numbness, odor, chewing cast and REMOVE IMMEDIATELY if so
what should i tell the owner about home care for external coaptation?
- observe toenails for swelling twice/day
- controlled short leash walks with protective covering
- remove wet bandages immediately
- routine bandage checks
- immediate check up if patient is bothered, smell present, worsening lameness, shifting or unstable bandage
what is external skeletal fixation, or “ex-fix”?
a surgical method whereby fractures, luxations, or injuries involving ligaments or tendons are stabilized using a device where the majority of the fixation remains outside the skin surface
what are 5 reasons to use an ex-fix?
- can be placed with minimal damage to local blood supply and disruption of fracture hematoma
- secondary healing achieved may be faster than primary with more invasive approaches
- with compromised biology this allows for adequate fixation & access to soft tissues
- frame is adjustable
- when used as the only repair, all implants can be removed
what are 4 disadvantages of an ex-fix?
- while in place, there is a breach of skin which could increase local infection
- big forces (bending) act on the pin, which could impact healing if frame not constructed properly
- not intended for long-term use – the longer it is there, the greater the chance for complications
- bulky, require daily care at home, and needs patient and owner compliance
list the 3 components of an ex-fix
- fixation pins
- connecting clamps
- connecting bars
what types of pins exist? what is the one rule when it comes to pin diameter?
generally:
- smooth or threaded (smooth not ideal since they are prone to loosening)
- half (penetrate soft tissue on one side) or full (penetrate soft tissue on both sides) pins
types of threaded pins: positive-profile or negative profile
diameter of whatever pin you choose should not exceed more than 25% of bone’s diameter
what are clamps? what types exist?
clamps = secure pins to external frame (via connecting bar)
types:
- single clamps = secure fix pin to connecting bar
- double clamps = secure two connecting bars to each other, forming articulated frame
what are connecting bars?
- these connect and stabilize fixation pins
- generally light weight with large diameter
- made from titanium, aluminum, carbon, acrylic
building an ex-fix: unilateral vs. bilateral
unilateral: one one side of limb using half-pins
bilateral: on both sides of limb using full pins
building an ex-fix: uniplanar vs. biplanar vs. multiplanar
uniplanar: with all pins in one plane
biplanar: pins in two planes
multiplanar: pins in multiple planes
Type Ia: give me pin type, # connecting bars, and -lateral or -planar
- half pins
- one connecting bar
- unilateral
- uniplanar
Type Ib: give me pin type, # connecting bars, and -lateral or -planar
- half pins
- two connecting bar
- unilateral
- biplanar
Type I-II: give me pin type, # connecting bars, and -lateral or -planar
- half pins with one full pin
- 2 connecting bars
- bilateral
- biplanar
Type II modified: give me pin type, # connecting bars, and -lateral or -planar
- half pins and 2 full pins
- 2 connecting bars
- bilateral
- uniplanar
Type II: give me pin type, # connecting bars, and -lateral or -planar
- full pins
- 2 connecting bars
- bilateral
- uniplanar
Type III modified: give me pin type, # connecting bars, and -lateral or -planar
- half and full pins
- 3 connecting bars
- bilateral
- biplanar
what is the weakest ex-fix configuration? strongest?
weakest: type I
strongest type III modified
what are 5 principles of ex-fix use?
- ex-fixes can neutralize all forces
- more complex frame = greater strength & stiffness
- Type II & III frames are mechanically superior but biologically more damaging (consider IM pin or “tie-in”)
- consider practicality of placement (femur + humerus can’t have full pin because there’s body close by)
- consider safe corridors
what is a safe corridor?
anatomic regions of the bone that are relatively devoid of overlying neuorvascular structures and are areas with minimal soft tissue coverage.
hazardous corridors and unsafe corridors also exist
you can get more rigidity in bilateral + multiplanar frames by incorporating interconnections. what are the two types of interconnections and which add more stability?
- articulations = do not cross fracture gap
- diagonals = do cross fracture gap
diagonals add more stability to the frame
what are acrylic external skeletal fixators?
= acrylic-based compounds that replace connecting bars and fixation clamps
great to use because they are custom molded, strong, lightweight, economical, no sharp edges, can place fixation pins anywhere
bad because you can’t adjust it after acrylic hardens (need to reapply)
what are circular external skeletal fixations?
these use fine tensioned wires (instead of large bone pins) to secure bone segments
wires are passed through the limb (like a full pin) and are supported on each end by specialized bolt attached to rings that act as clamps; the rings are connected along the length of the bone by connecting rods.
real useful because the ring-bone segment constructs form blocks that can easily be adjusted in 3D – useful for angular limb deformities and malunions
can be used together with a linear ex-fix on one side and circular ex-fix on other side = combine geometry + biomechanics provides stability of fracture in certain locations that are hard to achieve fixation
what are 6 principles of application of ex-fixes?
- utilize closed reduction
- know your anatomy
- fixation pins should be going through centre of bone (max stability and pull-out resistance) and don’t irritate soft tissue if you don’t have to
- ideally, use 3-4 pins per major fracture fragment
- preserve the bone-pin interface by using appropriate pin type/size, placement and drilling
- keep the working pin length as short as possible while not injuring soft tissues (~1 cm)
what are 3 major aspects of post-op care with an ex-fix?
- bumper bandages
- daily care (cleaning, ointment, check stability and lameness)
- routine radiograph assessment
bonus: if anything is wrong, assess immediately!
what are major soft tissue complications that come with ex-fix?
- skin irritation when placed near joint, pull and tear skin
- disrupt neurovascular bundles
- impale muscles
- pin tract infections are most common and result in discomfort and loosening or removal
what are some fixator complications that come with an ex-fix?
- pin or wire loosening
- pin or wire breaking
depends on if it happens early in healing or late – early means replacement and additional impants to improve stiffness
how do you evaluate fracture healing on a radiograph?
AAAA
- alignment = restoration of major fragments in bone as a whole
- apposition = replacement of displaced fracture fragments to original location
- apparatus = is device maintaining stability of fracture? is there loosening or bending?
- activity = biological response of bone to fixation being used – evaluate type and amount of callus and look for signs of infection and new bone formation
