Principles of equine fx repair Flashcards
Classification of fractures
- complete/incomplete
- stable/unstable
- open/closed
- configuration
- Greenstick/fissure
- Transverse
- Oblique
- Spiral
- Comminuted
- Multiple
- Impacted
- Avul/Diaphy/Metaphy/Pyseal (salt-H)/Epiph/apophy/articular
- Other
Stable fracture
Cortical continuity, positive prognosis
Open fracture classification
Type 1: < 1cm diameter skin perf, no loss soft tissue, no bone exp or gross contam
Type 2: Larger skin lac, little loss skin tis, minimal exp bone, min gross contam
Type 3: Extensive lac, massive skin defects, gross contam soft tis and fx bone
Main criteria for repair
- Minimal comminution
- 180 degress cortex (strut) for axial load
- Closed fx
- Sensible horse
- Pain control, well trained staff, well designed recovery system
Foals are less likely to suffer from
Support limb laminitis
Foals are more likely to develop
Angular limb deformity from abnormal load of physes
Foal implant removal may be indicated
When fracture has completely healed
Stall rest
-Splints (don’t require fixation)
Fractures that will heal w/ minimal intervention
- Deltoid tubercle of humerus
- Non-articular patellar fractures
- Fractures of scapular spine
- Some pelvic fractures
- Third trochanter of femur
- Stress fractures
Risk of conservative tx
catastrophic propagation of long bone fx
Splint coaptation
Tx incomplete fx tibia or radius
- emergency support, not only means
- prevent animals from lying down with head tie/sling
Casts
Supplements internal fixation/P3 wing fx Can cause -calus formation -delayed/failed union -breakdown opposite limb
Casting procedure
- Palpate daily for heat/swelling/moisture
- First cast changed after 3-4 days
- Foal casts then changed q10-14d
- Adult casts then changed q5-6 weeks
When casted watch for
Lameness Swelling Odor Moisture Heat
Three types external fixation constructs in horses
- transfixation-pin casts
- external fixators
- external skeletal fixation devices
External fixation constructs indications
- Open fractures
- Severely comminuted fractures distal limb
- when ORIF is not possible
External fixation constructs not used for
proximal limb fractures, not possible to apply
Transfixation pin casts indications
- Comminuted phalangeal fractures
- Distal MC/MT3 fx
- Breakdown injuries of the MCP joint
Transfixation pin cast procedure
- 2-3 cross pins placed in metaphyseal region bone proximal to fracture
- Pins incorporated into full/half-limb fiberglass cast
External skeletal fixators
- Allow immediate sub-normal weight bearing
- Allow access to open wounds for tx
- Not enough axial support for most adults
- Used in non-weight bearing fractures (mandibular)
External fixation complications
- Pin loosening, likely infection
- removal and curettage - Pin tract infection/fx
- Grade 1-3 minor infection can continue external fixation
- Grade 4-6 major infection must abandon external fixation
Insufficient external fixation
Limb remains painful and increases risk of supporting limb laminitis
Required cortex for successful repair
180 degrees of intact cortex
Anatomic reconstruction joint surfaces required for
preventing development of Osteoarthritis
Long bone fx repair
Screws and plates
Intramedullary fixation with pins and orthopedic wiring
Can only be applied in a few, limited circumstances
Orthopedic screws weakest in
Bending and shear
Screw strength determined by
Core diameter
Resistance of screw to bending related to
radius to the fourth power
Cortical screws
Larger core diameter and small diameter threads
-preferred in adult equine bone
Cancellous screws
Smaller core diameter with larger diameter threads
-reduces screw pull out
Cortex screws can be
- Inserted as position screws
- Inserted as implant screws
- Placed in lag fashion
Cortex screws expected to withstand weight-bearing loads should be placed
perpendicular to the long axis of the bone
Screws may be used to
reconstruct fracture fragments
-then a plate is applied to withstand weightbearing forces
Commonly used plates
- DCP (Dynamic compression plate)
- LC-DCP (limited contact dynamic compression plate)
- LCP (locking compression plate)
Recommended rate of drilling
1mm/s
Temp that causes bone necrosis and protein coagulation
54 degrees celsius
Saline used as
lubricant
-not to cool drill or bone
Temperature generation is inversely related to
Drilling rate
Plate fixation procedure
- Minimum of 3 screws (6 cortices) should be engaged on each side of fracture frag
- Plate generally applied to entire length of the bone (prevents stress riser at plate termination)
- Screw placed into every plate hole when possible
Plates strongest in
tension
-apply to tension side of fracture
Plates weak in
torsion
Plates weakest in
bending
Persistent cyclic loading results in
implant failure
Inability to transmit load across the fracture site will result in
implant deformation
Load transmission across fracture line for anatomic reduction results in
stability
plate applied in compression contoured to fit bone perfectly
compression of fracture only occurs on cis cortex
- trans cortex remains decompressed
- slight over-bending of plate at fx line results in compression across entire fracture line
Locking compression plates
Two treatments in one
- compression plating
- internal fixation
Equine fx repair complications
- Implant infection
- breakdown of implants/fracture repair
- Supporting limb laminitis
Foal fx repair complications
- Supporting limb angular deformity
- Premature closure of affected physis in salter-Harris fracture
- flexural deformity
- OA
- Lameness
