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Methods of Fracture Fixation

Methods of Fracture Fixation . What are the forces acting on a fracture after reduction and fixation? . Shear Torsional/ Rotational Bending . Which of these forces is most significant for: a) transverse fractures; b) oblique fractures; c) comminuted fractures. . Transverse

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Methods of Fracture Fixation

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  1. Methods of Fracture Fixation

  2. What are the forces acting on a fracture after reduction and fixation? • Shear • Torsional/ Rotational • Bending

  3. Which of these forces is most significant for: a) transverse fractures; b) oblique fractures; c) comminuted fractures. • Transverse • Rotational and bending • Oblique • Shear • Comminuted • Shear, compressive and torsional

  4. When is external coaplation indicated for tx of limb fractures in dogs and cats? • When rapid healing is expected • Immature dogs and cats • Simple, non-displaced, closed fractures • When joints above and below fracture can be immobilized • Fractures below elbow or stifle

  5. What is an external fixator? • device for holding fracture in place: a steel bar that is affixed parallel to a fractured long bone • Fixator pins are insterted through both cortices and secured external to limb with 1, 2 or 3 connecting bars.

  6. What forces does an external fixator counteract? • All forces

  7. What are the limitations on placement of Type II and Type III external fixators? • Type 2 fixators can not be placed on the humerus or the femur because they cannot be placed confortably • Type 3 ??

  8. Why is this method often used for open fractures and for comminuted fractures? • Open • The device is relatively easy to apply and may even be adjusted during the fracture site • Ready access is gained for open wound management • Comminuted • ??

  9. Why is it not considered a good method for articular fractures? • Does not offer stabilization of the joints above and below the fracture?????

  10. What type of bone healing would you expect with an external fixator? • Direct bone healing

  11. How can an external fixator be combined with other methods of fracture fixation? • Can be combined with cerclage wire, hemicerclage wire, IM pin ????????????

  12. What are the advantages and disadvantages of intramedullary pins? • Can only be used on a stable fracture in small dogs and cats and is not adequate for repair of femoral fractures in medium and large dogs • Excellent against bending forces

  13. What forces are and are not counteracted by intramedullary pins? • Only does bending forces

  14. What are indications and contraindications for intramedullary pins? • Indications: • Stable fracture • Small dogs and cats • Contraindications • Femoral fractures in large to medium dogs • Not used in the radius

  15. What other methods of fracture fixation may be used with an IM pin? • External fixators • Cerclage and hemicerclage wires

  16. Why are such combinations often used with intramedullary pins? • Because the IM pins only work against the bending forces and thus the addition of other methods of stabilization allows for better overall stability of the fractured limb

  17. What is cerclage wire? • Stainless steel wire • 18, 20 and 22 gauge • Spool or loop

  18. What are the guidelines for use of full cerclage wires? • Used in areas in which cylinder of bone can be reconstructed anatomically • Auxillary support – never used as primary means of fracture fixation

  19. What is a tension band? • One or two small pins are inserted through fracture fragments into the shaft of bone • A figure 8 of orthopedic wire is passed through a hole drilled into the shaft of bone and twisted around the pins

  20. In what type of fracture is it used? • Fractures of the tension physes

  21. What is the other use for a tension band? • May be used to close osteotomy done as part of approach to a joint

  22. Why does a tension band work only in these situations? • Because only in these situations can it convert distraction force of a tendon or ligament to compressive force.

  23. Define: dynamic compression plate, compression plate, neutralization plate, and buttress plate. What is a veterinary cuttable plate and what are its advantages? • Dynamic compression plate – self compressing screw holes • Compression plate – a type of bone plate in which the screws are arranged so that they compress the defect and actively promote closure (concept not an actual plate). • Neutralization plate – A metal plate used for the internal fixation of a long bone fracture to neutralize the forces producing displacement • Buttress plate - A metal plate used to support the internal fixation of a fracture.

  24. What forces do bone plates counteract? • All forces

  25. Why should a plate span the diaphysis in most situations? • Because of the stress riser effect and the fractured bone here

  26. What complication is associated with leaving a screw hole in a plate empty? • Empty holes means there is a weak spot and a large dog can break the plate.

  27. Why must 6 cortices be engaged on each side of the fracture? • There is a high rate of failure associated with fewer than 6 cortices, thus put in 6.

  28. Explain tension band plating. • Tension band plate is placed on tension side of weight bearing bone • Converts distraction (tension) forces to dynamic compression forces with weight bearing.

  29. What are the tension sides of the femur, tibia, humerus and radius? • Femur – craniolateral • Tibia – craniolateral • Humerus – varies with location of fracture • Radius – cranial

  30. Where are bone plates placed on each of these bones? • Femur – lateral • Tibia – medial • Humerus – cranial, medial, lateral or caudal • Radius – cranial

  31. What type of plate would you apply to a transverse fracture of the femur? • Compressive

  32. What type of bone healing would you expect? • Direct- contact

  33. What type of plate would you apply to a comminuted fracture of the femur? • Neutralization plate with lag screws or a buttress

  34. What type of bone healing would you expect? • Indirect for both depending if you use lag screws (direct)

  35. Describe the two types of bone screws • Cortical • Fully threaded, fine pitch • Used in cortical or cancellous bone • Cancellous • Fully or partially threaded, coarse pitch • Used in cancellous bone

  36. Describe lag screw fixation and positions screw fixation. • Gliding hole, equal to diameter of screw threads, is drilled in near cortex • Thread hole, equal to diameter of screw core, is drilled in far cortex and tapped • As screw engages far cortex, compression occurs across fracture line • Hole should be drilled so that it bisects angle between perpendicular to axis of bone and perpendicular to fracture line

  37. If you use 2 lag screws to fix a butterfly fragment to the main fracture fragments, and you then apply a bone plate, what type of plating have you done? • Neutralization plate?

  38. What is an advantage of an interlocking nail over a bone plate in resisting bending? • Neutral axis of the bone, plate is on one cortex.

  39. How, in general terms, is an interlocking nail placed in the bone? • Select nail of appropriate length, attach extension device to end of nail, use insertion tool to place nail into bone. Use drill guide jig for hole placement and place distal screws first

  40. When would a nail be contraindicated? • When there is no intact cortex proximal or distal to the fracture

  41. Nails, like IM pins, should not be retrograde in in the tibia. Why? • No way to get there without going through the joint and metal in a joint is a bad thing!

  42. What is the fracture assessment score? • Scoring system used to reflect high to low risk of failure of repair

  43. Give examples of mechanical factors, biologic factors and clinical factors that are used to develop a fracture assessment score for a patient. • Mechanical • # of injured limbs, patient size & activity, degree of load sharing • Biological • Age & health, open vs. closed, open vs closed reduction & surgeon’s skill, low vs. high energy, specific bone injured & fx location • Clinical • Patient compliance, owner compliance, patient comfort and pain tolerance

  44. Describe the requirements for implants for fractures with scores of 0-3, 4-7 and 8-10. • 0-3: lenghtneing plate, plate-fixator combination, plate-rod combination, fixator-pin combination with tie in, type II, type III fixator • 4-7: bone plate, type I/type II fixator, fixator-pin combiation with/without tie-in, pin plus cerclage • 8-10: type I fixator (smooth pins), pin plus cerclage, external coaptation

  45. Give an example of a suitable method of fixation for each of these groups. • 0-3: implant must bridge fracture and be strong enough to prevent bending or breaking as well as excess motion at fracture • 4-7: intermediate load sharing and healing time • 8-10: immediate load sharing, so do not need very strong or stiff implant; implant does not need to function for prolonged time

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