Case Study - Cannon Bone Laceration

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

1. Resident Rounds with AAEP Student Club April 21 st , 2014 Dane M. Tatarniuk DVM

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. 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. What recommendations do you make to the owner over the phone prior to you arriving on-farm or horse coming to your clinic?

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. 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. 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. Which way would you want the horse in the trailer to face?

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. Horse arrives to your clinic, you place it in the stocks. What do you want to do first?

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. Wound evaluation…..

13. Wound evaluation: What anatomy are you looking at?

14. Wound evaluation: What anatomy are you looking at?

15. Wound evaluation: What anatomy are you looking at?

16. Wound evaluation: What anatomy are you looking at?

17. Wound evaluation: Where do the vessels run?

18. Wound evaluation: Where do the vessels run?

19. Wound evaluation: How proximal does the flexor tendon sheath live?

20. Wound evaluation: How proximal does the flexor tendon sheath live?

21. Why is the horse knuckling over when it walks?

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. Why is the horse knuckling over when it walks? Lacerated extensor tendons…low concern Lacerated flexor tendons…huge concern

24. What steps do you want to take next?

25. Sedate your patient Safety first xylazine, r omifidine, or detomidine +/- butorphanol Clip and clean Sterile lube over wound Clip hair out of way Clean gently with betadine or chlorhexidine and saline

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. 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. 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. Before you perform anything, think about the anatomy: What are the joints of the hock?

30. You perform a radiograph with a teat cannula inserted at the top of the wound: Interpretation?

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. 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. So now that you have confirmed that the wound doesn’t extend into the joint…. B eyond sedation, how are you going to provide analgesia so that you can repair this?

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. What steps do you need to take to provide this wound with the best chance to heal by primary intention?

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 2 nd intention healing, or can consider suturing it to expedite the process Immobilization

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. 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. 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. What do you want to say to the owners regarding prognosis / time frame for healing?

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 2 nd intention, however the time frame changes significantly 1 st intention healing – 2 to 3 weeks 2 nd intention healing – 2 to 6 months

42. So now that you have repaired the wound, what kind of aftercare do you want to recommend? Medications?

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. 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. So now that you have repaired the wound, what kind of aftercare do you want to recommend? Exercise Recommendations?

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. So now that you have repaired the wound, what kind of aftercare do you want to recommend? Bandaging Recommendations?

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. So now that you have repaired the wound, what kind of aftercare do you want to recommend? Suture removal?

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. Horse goes home. At day 3, the owner emails you this picture:

52. Day 6

53. Day 11

54. Day 14

55. Day 16

56. Day 30

57. 5 weeks

58. 8 weeks What has happened to the wound?

59. 8 weeks What is happening to the wound? Proud-flesh “Exuberant granulation tissue”

60. 9 weeks Few days post trimming proud flesh

61. 12 weeks

62. 16 weeks Owner reports increase in lameness, increase in discharge present

63. Horse comes into clinic for evaluation. Radiograph is taken. What is your diagnosis?

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. Horse had removal of sequestrum 3 weeks ago. Is recovering well. Wound still hasn’t fully healed. QUESTIONS ?