Small Ani. Sx- Orthopedics- Fracture Tx- Options of Tx 2

drraythe's version from 2016-04-29 14:51

Section Sx: External fixators

Question Answer
main 3 indications for an external fixator?(1) Treatment of fractures (preservation of blood supply) (2) Temporary stabilization of joints (Tendon repair, Wound treatment) (3) Treatment of osteomyelitis (bc no contact with the infected bone)
what three things do you need to make an external fixator?Pins, Clamps, Connecting bars
3 categories of options of different types of pins you can use for an external fixator? (which does he prefer out of the sets)(1) Smooth or threaded pins (smooth not used anymore- gets loose too fast) (2) Negative or positive thread.....neg is when the thread diameter is less than the shaft diameter. pos is when the thread diameter is bigger than the shaft diameter. (he says try to always use pos pins bc in pos there is an even core, negs like to break) (3) End or centrally threaded (he says centrally is more stable bc 2 connecting bars on either side)
Connecting bars can be different sizes, and can be metal or carbon composite. Whats the diff between metal/carbon?metal SUPER radiopaque, whereas carbon is not so you can see bone more on rads as its healing
2 main types of areas you can use external fixators in? two ways to apply them?(1) Long bones: better below stifle / elbow (too many mm above the stifle/elbow, irritate mm and cause dec mobility) (2) Mandible / maxilla...... can be Applied in closed or open fashion (closed- put pins through incision in the skin. Open- cut open skin and SQ and detract mm and apply)
how many pins per fragment?2 or more pins per fragment (only one= rotation around it)
how should the pin diameter compare to the bone diameter?Pin ∅ < 25% ∅ of bone (∅=diameter)
how far away should the pins be from the fracture?2 pins ∅ (diameter) from fracture (so if pin is 3mm, want to be 6mm from the fracture)
what is the minimum amount of pins that need to be placed per fracture, and how should they be arranged?Need at least 4: distant-close, close-distant (on pic, need at least 1,3,4,6 )
how do you apply the pins?Drill a Pilot hole--> Place the pins with power drill low speed (150rpm) (low speed to avoid thermal necrosis!!! can squirt saline on it too to keep it cool)
Blood supply and external fixators--> how does this compare to internal fixators? WHO does this matter the most in?external allows better healing bc a plate will compress on the periosteum and dec blood supply to that area. This is esp. detrimental in young animals where the majority of their blood supply comes from the periosteum.
what are the three types of configurations you can put external fixators in? which is the strongest?(1) Type 1 (unilateral) (2) Type 2 (bilateral, uniplanar) (from medial to lateral) (3) Type 3 (bilateral, biplanar) (STRONGEST)
do external fixators allow primary or secondary bone healing?secondary bc far away from bone so always some movement
what's a Ringfixateur (Ilizarov)?uses wire under tension and the clamps are replaced by rings wires are in the same plane so if you have a very distal fracture you can still provide stability create micromotion and stimulate bone healing stimulating lengthing and correct deformities (bandage between it to compress skin and then there is no mvt between skin, ring, and wire)
Postoperative management of placing external fixator?Clean, Disinfect pin/skin area, Bandage, Periodical bandage changes
4 main complications of external fixators?(Most complication are due to bad technique, pick wrong fixator, technical errors) (1) Pin tract infection (most common complication) (2) Loosening of implants (3) Apparatus´breakage (4) Bone fractures
more pins= ...?more stability
Pros vs cons of external fixator?Pros= no implants in fracture area. Cons= soft tissue trauma and postoperative care
how do you want the connecting bar positioned?As close as possible to the skin, but no contact between the skin and the bar.

Sx: Screws and plates

Question Answer
2 ways you can use screws?by themselves or with plates
what is a Cancellous screw like? Where is it used?Thin core & deep threads, used in metaphyseal bone (cancellous bone is in the metaphysis)
screws alone cause what kinda compression?intrafragmentary compression
what is a Cortex screw like? where is it used?used in diaphyseal bone (thread is smaller and closer bc cortex is harder so dont need as deep sets)
2 most commonly used screw diameters are?2.7mm and 3.5mm
what are the two kinds of screws you can use and what is their purpose?(1) position screw- doesn't compress, just holds fragments in position. (2) Lag screw- causes compression in both ends of the fx, good for joint fractures and oblique fractures
what kinda holes do you make for a position screw, how do you put it in?Drill a pilot hole and then drill the same size and put in the screw. No compression. Basically 2 pilot holes.
what kinda holes do you make for a lag screw, how do you put it in?make a glide hole (big hole in one cortex) and a thread hole (tiny hole in other cortex) so when place screw there is compression and anatomical reduction
2 options of implants for treating articular fx are...K-wire and lag screws (these allow primary bone healing bc accurate anatomical reduction and compression)
3 pros to using a bone plate?Early use of the leg (avoid mm atrophy), Complete recovery, stable fixation
what are some tools you need to apply bone plates?Plate bender (bends plate to contour of bone) , power drill, drill bits of diff sizes, drill guides , deep gauge (put through hole you made to measure what size screw you will need) , tap (used to thread the bone-- newer screws are self-tapping) , screwdriver
3 ways to classify a plate?size, type, function
3 types of plates?Dynamic Compression plates (DCP) (most commonly used), Reconstruction plates (good for difficult areas), Veterinary cuttable plates(cut the amount you need).... (and diff forms of each kinda plate)
what is a Dynamic Compression Plate (DCP) like? what is a variation on this type of plate?have an oval hole , there is also a variation called a Limited contact dynamic compression plate (LC-DCP) (indentations under plate dec bone contact so less pressure and less damage to periosteum)
pros and cons of Veterinary Cuttable Plate?Cuttable 30 cm long, so comes in a long piece you can cut to size which is nice. It is also cheap. Has round screw holes and comes in 2 sizes. However, we cannot compress it!!!! (weak enough to be cut= not strong enough to take compression force) (good in young cats who heal fast)
what does a Reconstruction plate look like? pros and cons of it?Deep notches between holes. This plate allows more contouring and is good for difficult fx like pelvis, or close to joints. It is Weaker than DCP (dynamic compression plate) though
what are some different forms of reconstruction plates?T-Plates, L-Plates (articular fractures), Acetabular plates....
3 possible functions of a plate?Compression, Neutralization, Bridging (Same plate can be used in 3 ≠ manners <--idk what that symbol means)
how does a Compression plate work?allows intrafragmentary compression-- the oval hole means as you screw in the screw, it slides to the side, pulling the pieces together.
what type of fx is a compression plate good for tx? what kinda bone healing happens when you use one? what tools do you need to use it?Good for Simple transverse fractures, they allow 1* bone healing bc of the compression. You will need special drilling guides
what is this?compression plate! (hole shape shown underneath)
how do you achieve Maximal compression with a compression plate?With 4 eccentric positioned screws
explain a Neutralization plateused to protect weaker implants, Plate avoid collapse of a reduced fracture (stability). So basically the plate protects the fixation. If you see any other implant, it is a neutralization plate. Primary stabilization provided by other implants
How does a Bridging plate work? what kinda fx do you use it in?used with Comminuted fractures since there is no way to reduce them, you just bridge the fx/callus. The Plate supports all the acting forces. It is a Stronger plate which is used for Biological fixation.
what is one way to do Fracture reduction?can use forceps to pull and reduce the bone
how should you place the forcep in relation to the fx if you want to reduce with forceps?(also use forceps to keep reduction during sx) perpendicular to fx
How many screws?Never less than... 2 per fragment (4 cortices), 6 cortices for long bone (diaphyseal fractures)- bc each screw touching 2 cortex (basically know that one screw is NOT enough)
Do you put plate on tension or compression side?ALWAYS put plate on TENSION side, compression side placement will make it worse by forcing open the tension side
internal fixator aka?locking plate
why is an internal fixator called a "locking plate"? what is the benefit of this feature?screws "lock in" with threading on the head: means less friction between the plate and the bone
what happened here?? how do you avoid this problem? plate pressed on bone, compressed the periosteum, area under plate suffered devascularization--> necrosis. WE SOLVE THIS PROBLEM by instead of using a plate, using an internal fixator (locking plate) which allows you to leave a gap between the plate and the bone (no compression then)
how does a classic plate versus a locking plate (internal fixator) affect the reduction of the bone?loss of reduction with the classic plate bc the screws will pull the bone to the plate-- in the locking plate, this doesnt happen so there is no loss of reduction.
primary loss of reduction vs secondary loss of reductionPrimary: when you take out the plate, the bone loses reduction. Secondary: losing reduction as animal puts weight on the plate
Pros and cons of internal fixators? (what is their identifying feature?)(Screw head & plate hole threaded) PROS: More stability/ less screws needed, Less blood supply damage, Less contouring needed, Faster healing. CON: more expensive

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