Large Animal Fracture Specifics and Coaptation

Question 1

describe common concepts of fracture occurrence

Answer 1

2 common etiologies

1. extrinsic cause: external trauma
2. intrinsic cause:
   -excessive muscle (soft tissue) action: avulsion fractures
   -pathologic fractures: bone is abnormal for some reason and as weakens progressively, bone may fracture (cancer, cyst)

Question 2

describe the forces involved in fracture development (5)

Answer 2

1. tensile forces:
   -pull bones in opposite direction cause osteons to fail at the cement line and lead to transverse fractures, avulsion fractures
   -counteract in orthopedics with a tension band (fasten fragment removed from parent bone to the parent bone to repair)
2. compressive forces (opposite of tensile):
   -are rarely the only force involved resulting in a fracture (in quadrupeds); often combined with SHEAR forces
   -result in oblique failure of the osteon when combined with shear forces
3. shear forces:
   -act parallel to a surface to deform bone in an angular manner (when two surfaces collide over each other)
   -leads to oblique failure of osteon along the plane of maximal shear stress when combined with compressive forces
   -counteract by placing a plate on the side of the shear stress to provide adequate support
4. bending:
   -compression and tension combined
   -bone is weaker in tension, so the fracture starts from the tension side (the one opposite the compression, the side being pulled apart)
   -implants MUST be placed on the tension surface of bones when possible to counteract tensile stress
5. torsion:
   -twist/rotate around an axis due to multiple forces
   -interior of bone undergoes compression, tension, and shear
   -result in spiral fractures (spiral up the shaft of the bone)

Question 3

what are the purposes of coaptation? (5)

Answer 3

1. apply pressure on soft tissues
2. minimize dead space
3. protect wounds
4. support structurally unsound limbs
5. minimize further damage

Question 4

what must be established BEFORE any coaptation?

Answer 4

restraint of the animal!! quickly!

physical restraint, twitch, sedation

Question 5

describe principles of sedation before coaptation

Answer 5

1. calm patient to allow the exam and immobilization of the limb
2. avoid over-sedation: avoid ataxia and further trauma
3. best combination:
   -alpha2 agonist (detomidine or xylazine) and
   -opioid (butophenol)
4. avoid acepromazine! (causes hypotension)

Question 6

describe the 3 layers of the basic bandage

Answer 6

1. wound covering layer (+/-) dressing:
   -sterile and non-adhesive to protect wound and minimize contamination, hold in place with roll kilng or gauze
2. absorbable/absorben layer (bulk of the bandage):
   -variable but usually some variation of thick cotton padding wrapped with even tension
3. retaining layer: most commonly vetrap (good tension and progression) or elasticon (interior layer is very sticky, allows bandage to stay in place)
   -more wiggle room to put elasticon on skin without overwhelming with tension in large animals versus small animals
   -can use elasticon through entire bandage if want to distribute compression throughout

Question 7

describe the Robert Jones bandage

Answer 7

1. multiple layer bandage where each layer consists of padded layer covered by elastic gauze
2. total diameter of bandage should be at least twice the diameter of the leg
3. thicker and can provde more compression and restraint that the basic bandage

Question 8

describe the splint or cast bandage (2)

Answer 8

1. same as the basic bandage but with the addition of rigid material: PVC pipe, cast material, wood board, or other
2. used when a limb is unstable: soft tissue injury (tendon or ligament damage) or with bone or joint trauma (fracture, luxation) to prevent further damage during therapy or transportation

Question 9

describe splinting of the distal limb in equine (carpus or tarsus down, both forelimb and hindlimb)

Answer 9

1. fetlock is the dominant biomechanical force, a bending force; counteract by placing fetlock in a straight line
2. align the dorsal cortices (front portions of each bone in the limb) by splinting in a straight line, may need to place something underneath the foot (cast material, plastic object, to allow heel to be higher than the toe for alignment, but ensure no direct impact between skin and whatever device you use!)

Question 10

describe splinting of proximal limb (3)

Answer 10

1. counteract dominant bending force at the carpus
2. align the limb by splinting the carpus in a straight line, can add something in the bandage to accomplish, but remember no contact with the skin
3. extend splint beyond elbow to try to meet the “one joint above and one joint below rule” of coaptation

Question 11

describe splinting the forelimb

Answer 11

robert jones bandage in multiple 1 inch thick layers to get bulk with a splinting device, likely on lateral side of limb to achieve stability

Question 12

describe splinting the midforelimb splint (4)

Answer 12

1. rigid splints placed from elbow to the ground
2. 2 splints: lateral and caudal
3. tape splint with nonelastic adhesive tape as tightly as possible to try to prevent injury from the splint itselt
4. commonly provide this kind of coaptation due to loss of triceps function (fractured ulnar, radial nerve damage, etc.) resulting in inability to hold limb in extension

Question 13

describe splinting the proximal hindlimb (4)

Answer 13

1. difficult to splint due to reciprocal apparatus!
2. flexion of the stifle causes over-riding at the fracture site rather than flexion of the hock
3. stifle flexion cannot be prevented
4. do to best of ability, place bandage on limb as high as possible and splint hindquarters to prevent lateralization but know that this is difficult due to lack of prevention of stifle flexion
5. full limb cast can cause rupture of reciprocal apparatus or peroneus tertius!!