A2 Fracture Implants Flashcards
become familiar with the basic treatment options for dogs and cats with fractures, know and understand the broad categories and nature of implants available - auxiliary implants, screws, interlocking nails, plates
What is a salvage procedure? Name two examples.
A salvage procedure is a treatment option that leads to a permanent change of a musculoskeletal structure which causes some change in the original function.
Examples include excision arthroplasty or limb amputation.
What do normograde and retrograde insertion of intramedullary pins refer to?
Normograde insertion implies entry of the pin at one end of the bone and across the fracture site into the other end of the bone.
Retrograde insertion indicates the pin has been inserted into the bone via the fracture through one of the bones and back down across the fracture once the fracture has been reduced.
What hree functions can bone plates have?
Plates can function as 1. compression plate 2. neutralisation plate 3. bridging plate (Important to note that these are specific functions, not specific plates).
What is the tension band principle and how does it apply to plates?
During weight bearing every bone has a tension and compression side. Plates should be applied to the tension side to convert this force into compression thus optimising fracture healing.
There is only one type of fracture configuraiton, in which the use of cerclage wires could be consdeired for stabilisation. Which one?
Long oblique fractures - the length of the fracture must be at least 2.5x the diameter of the bone.
What is a Lag screw and how would you insert it?
A lag screw is a way of inserting screws which results in compression of bone fragments - It is not an actual type of screw, any screw could be inserted as a lag screw.
To insert, over drill the bone fragment you initially insert the screw into (the near or cis-cortex) so that the threads of the screw do not engage with the walls of the hole and the screw just glides in - but then drill a normal hole of equal diameter to the screw in the second fragment (the far or trans-cortex) so that the threads of the screw will engage with this bone fragment - As a result, the head of the screw on the near cortex and the action of the threads on the far bone cortex will compress the fragments together.
What is a DCP? Briefly outline the principle and application.
DCP- Dynamic compression plate. It has oval holes to allow applying compression at the fracture site. In order to do this, the plate is fisrt fixed to the bone on one side, then a drill the hole on the other side is placed excentrically to the plate hole and when the screw is tightended, the head slides into the centre of the plate and thereby compresson is appied on the fracture side. Can be done with up to 4 holes, 2 on each fracture side. Useful in transverse fractures or transverse osteotomies.
What forces can different implants cope with?
IM pin- Bending 1/3
ESF- Bending 2/3, Shear 1/3, Compression 1/3, Torsion 1/3
Plate- Bending 1/3, Shear 2/3, Compression 3/3, Torsion 2/3
Briefly outline the technique of cerclage wire application.
Apply the wire with a ‘wire passer’ to go around the bone and protect the soft tissue, apply perpendicular to the bone, twist the wire evenly while pulling on it and leave three twists. Ideally do not bend twists, only in exceptional cirucmstances, when there is not enough tissue to cover them. Must use at least two wires, use the largest diameter possible and apply tightly!
What is a LCP? Briefly outline the principle and application.
LCP- Locking compression plate. Plate holes have threads and the screw heads have threads, and thereby the screws and plate engage into an angle stable construct (a little bit similar to an ESF, but on the inside). Requires less accurate plate bending (tolerates up to 2mm gap between plate and bone) and adds stability. Disadvantage - screws cannot be angeld (or only minimally, depending on lcoking system used), which can be a disadvantage close to the fracture site or around joint, for example.
What are hybrid plates? Briefly outline their principle and application. Do you know an example?
A hybrid plate has features of a dynamic compression plate and a locking compression plate. This can be helpful to add stablity to the overall construct. An example is the (Synthes) TPLO plate.
What are reconstruction plates?
Reconsruction plates can be bent in all directions, which is useful for the application around bone which is stongly shaped, e.g. maxilla, acetabulum, lateral humeral condyle. However, it is not a very strong plate, therefore not suited for stabilisation of long bone fractures.
What is a VCP? Explain the main features.
VCP = Veterinary cuttable plate. Can be cut to length. Useful for smaller bones (e.g. cats), but not very strong. Can be ‘sandwitched’ to add stability - put 2 plates together. Round holes - no cpmpression possible.
