Case Study - Cannon Bone Laceration

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Presentation prepared for veterinary students in the AAEP student club. Case study of a cannon bone laceration.

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Case Study - Cannon Bone Laceration

  1. 1. Resident Rounds with AAEP Student Club April 21st, 2014 Dane M. Tatarniuk DVM
  2. 2. Case Study • Signalment – 6 year old Quarter Horse gelding – Will be a barrel racing prospect – Found this AM in the pasture with wound • Owner is on the phone and unsure what to do – What other questions do you ask for history?
  3. 3. History • Wound is located on right hind leg, front of the cannon bone – Appears really deep – Approximately 4 x 12 inches • Horse has not had any medications yet • Not sure what horse hurt itself on, suspect the fence • Horse was vaccinated last Spring • No previous medical or lameness problems • Horse is lame at the walk, appears to ‘knuckle’ over onto fetlock, but still bearing full weight on limb
  4. 4. • What recommendations do you make to the owner over the phone prior to you arriving on-farm or horse coming to your clinic?
  5. 5. • Can administer NSAID for pain – Depending on your time till you can attend to horse – Non-steroidal anti-inflammatory • Phenylbutazone (Bute) or Flunixin meglumine (Banamine) – Usually avoid pain medication prior to subtle lameness exams; in this case, important for horse • Can cold-hose the limb • Apply a compression bandage – Shipping or standing wrap – Cotton / Vetwrap / Elasticon – Compression aides in decreasing contamination and helps coagulation
  6. 6. • If your concerned about a cannon bone fracture, your on-farm and transporting the horse, what would be an appropriate way to splint the limb for transport?
  7. 7. • If your concerned about a cannon bone fracture, what would be an appropriate way to splint the limb for transport? – Need 90 degree stability – Lateral and plantar splint acceptable – Use PCV pipe, wooden board, broom sticks, etc. – Apply from foot up to point of the hock – Tape splints to a bandage placed on the leg – Or, can use ‘Kimzey’ pre-made splints
  8. 8. • Which way would you want the horse in the trailer to face?
  9. 9. • Which way would you want the horse in the trailer to face? – Forwards, • When applying the brakes to the truck/trailer unit, momentum will put more weight on forelimbs instead of hind. – Opposite holds for forelimb injuries; place horse in trailer backwards
  10. 10. • Horse arrives to your clinic, you place it in the stocks. – What do you want to do first?
  11. 11. • Horse arrives to your clinic, you place it in the stocks. – What do you want to do first? • Systemic (Physical) Exam! – Heart rate » Pain » Shock – Resp. rate » Pain – Temperature » Should be normal – Mucus Membranes » Hypo-perfusion – Don’t forget the Zebra • Primary Colic -> horse thrashes -> cuts itself
  12. 12. Wound evaluation…..
  13. 13. Wound evaluation: What anatomy are you looking at?
  14. 14. Wound evaluation: What anatomy are you looking at?
  15. 15. Wound evaluation: What anatomy are you looking at?
  16. 16. Wound evaluation: What anatomy are you looking at?
  17. 17. Wound evaluation: Where do the vessels run?
  18. 18. Wound evaluation: Where do the vessels run?
  19. 19. Wound evaluation: How proximal does the flexor tendon sheath live?
  20. 20. Wound evaluation: How proximal does the flexor tendon sheath live?
  21. 21. • Why is the horse knuckling over when it walks?
  22. 22. • Why is the horse knuckling over when it walks? – Loss of long digital extensor tendon and lateral digital extensor tendon – Able to flex the fetlock – Not able to extend the fetlock
  23. 23. • Why is the horse knuckling over when it walks? – Lacerated extensor tendons…low concern – Lacerated flexor tendons…huge concern
  24. 24. What steps do you want to take next?
  25. 25. • Sedate your patient – Safety first – xylazine, romifidine, or detomidine • +/- butorphanol • Clip and clean – Sterile lube over wound – Clip hair out of way – Clean gently with betadine or chlorhexidine and saline
  26. 26. • Probe the wound with sterile instrument – Hemostat – Teat cannula • Map out extent of dead space, depth of the wound, feel for fracture lines, • Can palpate with instrument to see if wound extends into joint, but be gentle so that you don’t accidentally make a closed joint, open
  27. 27. • So you palpate the wound, – Feel tons of cannon bone exposed – Some dead space that extends towards the hock joints – Wound does not seem to extend towards the flexor tendon sheath • You have concern regarding the close proximity of the wound to the hock. – What do you want to recommend next?
  28. 28. • Three options: – Radiographs with radio-opaque instrument inserted • Visualize instrument in joint space – Arthrogram • Contrast injected into joint, then radiograph – Joint Distention with sterile saline/carbocaine • Check for leakage from wound • What are the pro’s / con’s of each of these methods?
  29. 29. • Before you perform anything, think about the anatomy: – What are the joints of the hock?
  30. 30. • You perform a radiograph with a teat cannula inserted at the top of the wound: Interpretation?
  31. 31. • You also distend the tarsal-metatarsal joint with sterile saline, following a 10 minute preparation of the skin. – No leakage into the wound is noted, pressure on the syringe plunger. • What is the landmark to enter the TMT joint?
  32. 32. • Needle: 1.5 inch, 20 gauge • Volume: 3 – 5 cc • Tarsal-metatarsal joint: – Injected on the plantar- lateral aspect of the hock – Needle is inserted immediately above the head of the lateral splint bone – Needle is angled in a dorsal- medial and distal direction
  33. 33. • So now that you have confirmed that the wound doesn’t extend into the joint…. • Beyond sedation, how are you going to provide analgesia so that you can repair this?
  34. 34. • Analgesia Options: – Local ring block around the circumference of the wound • Lidocaine, Carbocaine (mepivicaine) – Regional Limb Perfusion • Tourniquet proximal to wound, inject ~60cc of carbocaine/lidocaine into vein. • “Bier block” – Peroneal-Tibial nerve block • Desensitizes most tissue from hock and below – General Anesthesia • If horse was too dangerous to work on standing • Ketamine / Diazepam or Triple Drip • Always a risk that the cannon bone could have a hairline fracture – high risk for recovery
  35. 35. • What steps do you need to take to provide this wound with the best chance to heal by primary intention?
  36. 36. • What steps do you need to take to provide this wound with the best chance to heal by primary intention? – Debridement of bone • Curette or scrape off the exposed bone surface • Take tissue to where it bleeds, remove contamination – Debridement of soft tissue • Remove any tissue that is black, purple, green, etc. • Leave only healthy, bleeding tissue behind • Trim edges of the flap of the wound 1-2mm – Debride tendon • Remove the ends of the tendon • Let it undergo fibrosis via 2nd intention healing, or can consider suturing it to expedite the process – Immobilization
  37. 37. • Following debridement, good idea to lavage the wound to remove contaminants – Sterile saline • Add in 10cc of 2% betadine solution / L • Or, add in 25cc of 2% chlorhexidine solution / L – Optimal pressure is 7-8 psi. Consider using 35cc syringe with 18 gauge needle – Alternatively, can use motorized wound irrigation systems • ie, Stryker
  38. 38. • What size of suture do you want to use? • What type of suture material do you want to use? • What suture pattern do you want to use?
  39. 39. • What size of suture do you want to use? – Larger is more resistant to tension. – Anywhere from #0 to #2 should work OK • What type of suture material do you want to use? – Ideally, non-absorbable • Prolene – PDS would be acceptable as well – Want monofilament, not multifilament • What suture pattern do you want to use? – Tension relieving • Vertical mattress • Near-far-far-near
  40. 40. • What do you want to say to the owners regarding prognosis / time frame for healing?
  41. 41. • What do you want to say to the owners regarding prognosis? – A lot of these wounds, even with proper suturing, will dehisce – Always good to try and suture the wound as it acts as a physiologic bandage – If wound dehisce, it will still heal by 2nd intention, however the time frame changes significantly • 1st intention healing – 2 to 3 weeks • 2nd intention healing – 2 to 6 months
  42. 42. • So now that you have repaired the wound, what kind of aftercare do you want to recommend? – Medications?
  43. 43. • So now that you have repaired the wound, what kind of aftercare do you want to recommend? – Medications? • Systemic Antibiotic Options – Trimethoprim sulfa – Ceftiofur – Penicillin / Gentamicin • Consider Regional Limb Perfusion • Anti-inflammatory – Phenylbutazone
  44. 44. • Regional Limb Perfusion – Place a tourniquet around the tibia, to occlude the vasculature – Inject antibiotic (such as amikacin), diluted in a large volume of saline, into the vein – High pressure in the vasculature, from the tourniquet and large volume of medication, increases extravasation of antibiotic out of vein and into tissue – Tourniquet kept in place for 20-30 minutes – Attains antibiotic levels that are 5-15x the MIC of common pathogens in the tissue / synovial fluid – Minimizes systemic side effects, reduces cost
  45. 45. • So now that you have repaired the wound, what kind of aftercare do you want to recommend? – Exercise Recommendations?
  46. 46. • So now that you have repaired the wound, what kind of aftercare do you want to recommend? – Exercise Recommendations? • Stall rest until suture removal – If it holds • Stall rest or small paddock rest if it dehisces and you wait for second intention healing to occur
  47. 47. • So now that you have repaired the wound, what kind of aftercare do you want to recommend? – Bandaging Recommendations?
  48. 48. • So now that you have repaired the wound, what kind of aftercare do you want to recommend? – Bandaging Recommendations? • Wound bandage overlying the incision – Non-adherant pad (Telfa) – Held in place with white kling or elasticon • Support bandage – Important in first few weeks of healing – Decrease edema – Hock can be difficult to keep bandaged • +/- Splint – Decrease movement on suture line by keeping fetlock extended – Hard to properly splint the hock such that it remains immobile • Could also consider a bandage cast
  49. 49. • So now that you have repaired the wound, what kind of aftercare do you want to recommend? – Suture removal?
  50. 50. • So now that you have repaired the wound, what kind of aftercare do you want to recommend? – Suture removal? • If it doesn’t dehisce sooner, then sutures can be removed at 14 days • For high tension wounds, consider staggering suture removal – Half taken out at 14 days – Half taken out at 21 or 28 days
  51. 51. • Horse goes home. At day 3, the owner emails you this picture:
  52. 52. • Day 6
  53. 53. • Day 11
  54. 54. • Day 14
  55. 55. • Day 16
  56. 56. • Day 30
  57. 57. • 5 weeks
  58. 58. • 8 weeks • What has happened to the wound?
  59. 59. • 8 weeks • What is happening to the wound? – Proud-flesh – “Exuberant granulation tissue”
  60. 60. • 9 weeks • Few days post trimming proud flesh
  61. 61. • 12 weeks
  62. 62. • 16 weeks • Owner reports increase in lameness, increase in discharge present
  63. 63. • Horse comes into clinic for evaluation. • Radiograph is taken. What is your diagnosis?
  64. 64. • “Sequestrum” • Necrotic bone – Results from concurrent infection and loss of blood supply • Body is trying to reject the diseased bone • Surgical removal indicated
  65. 65. • Horse had removal of sequestrum 3 weeks ago. Is recovering well. Wound still hasn’t fully healed. • QUESTIONS ?

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