Midterm Flashcards
What are the five forces that cause fractures?
- Tension
- Compression
- Shear
- Bending
- Torsion
What type of fracture does the force of tension typically produce?
Avulsion
What type of fracture does the force of compression typically produce?
Short oblique
What type of fracture does the force of shear typically produce?
Lateral condylar fracture
What type of fracture does the force of bending typically produce?
Transverse or short oblique
What type of fracture does the force of torsion typically produce?
Spiral
When describing fractures, what does configuration generally refer to?
Incomplete or complete
Then orientation of the fracture
Name and differentiate the two types of incomplete fractures.
Greenstick (two cortices)
Fissure (one cortex)
Compare comminuted vs. segmental fracture
Comminuted = 3+ seg, fx lines intersect Segmental = 3+ segs, fx lines don't intersect
Define type I open fracture
Clean soft tissue laceration <1 cm
Define type II open fracture
Soft tissue laceration >1 cm; mild trauma, no flaps/avulsion
Define type III open fracture
Vast laceration; contamination
Why is it important to recognize articular fractures?
They demand anatomic reduction and stabilization for healing
Define type I Saltar-Harris fracture
Physeal separation
Define type II Saltar-Harris fracture
Involves metaphysis and physis
Define type III Saltar-Harris fracture
Involves epiphysis and physis
= ARTICULAR
Define type IV Saltar-Harris fracture
Involves metaphysis, physis and epiphysis
= ARTICULAR
Define type V Saltar-Harris fracture
Physeal crush/compression
What is the prognosis for any Saltar-Harris fracture?
Assume that the growth plate is going to close
What are the 6 descriptors of a given fracture?
Open/closed Configuration (incomplete/complete + orientation) Location (on bone) Right or left Bone Displacement
What is the purpose of the fracture assessment score and what factors is it based on?
Purpose: assist in selecting appropriate fracture repair, assess score based on risk
Factors: clinical, mechanical, biological
Fracture assessment score:
High scores signify __1__ healing with __2__ reliance on implants.
Low scores signify __3__ healing with __4__ reliance on implants.
1 - rapid
2 - less
3 - slow/complicated
4 - greater
Primary goal of fracture repair
To promote an early ambulation and complete return to function
Define reduction (verb vs noun) and the purpose
VERB: the process of re-apposing the fx fragments and/or segments (to their normal anatomic/functional position)
NOUN: describes apposition of the fx segments/fragments (anatomic, near anatomic or non-anatomic)
Purpose: anatomic reduction allows load sharing between bone and implants
Define mechanical fixation
Anatomic reduction and rigid fixation; fixing a fracture at both ends by means of pins or screws, then using fixation units to reduce and immobilize
Define biological fixation
Closed or limited open reductions to preserve the local fracture environment (soft tissue = vascular supply)
“Bridging osteosynthesis”
Define alignment
Orientation of the joints proximal and distal to the fracture
Define fixation and the purpose
Means by which the fracture segments are maintained in functional position
Purpose: rigid fixation promotes weight bearing, fx healing
Which has a greater impact on function, reduction or alignment?
Alignment
Don’t necessarily need to reduce to achieve functional alignment (biological approach)
Describe primary vs. secondary bone healing
Primary bone healing involves osteoblasts directly laying down bone, requires anatomic reduction and rigid fixation, produces minimal callus, takes longer to heal, but rapid/complete return to function
Secondary bone healing occurs with spontaneously or with minimal fixation (no rigid stabilization); strength depends on callus
- Stages: hematoma, granulation tissue, fibrocartilage, cartilage, woven bone, lamellar bone
Three indications for bone grafting
Enhance union
Replace bone loss
Arthrodesis
What three sites can a bone graft be harvested from? How should it be stored?
Greater tubercle Iliac crest Proximal tibia Storage: sterile container with lid HARVESTED PRIOR TO FX REPAIR
Four possible functions of bone grafts
- Direct osteogenic effect (transfer osteoblasts) = fresh cancellous autografts
- Osteoinduction (recruitment) = allograft from euthanasized animal
- Osteoconduction (scaffold)
- Structural support (complications) = cortical (allo)grafts
Define coaptation and give examples
Extra-corporeal treatment modalities used to approximate fractures/other msk abnormalities
Ex: casts, splints, bandages
ONLY DONE FOLLOWING CLOSED REDUCTION, NEVER FOLLOWING OPEN REDUCTION
What is the primary stability afforded with a splint or cast?
Stability against bending forces
Good for transverse fx!
Five indications for coaptation
- Temporary immobilization (msk injuries)
- Fractures in young animals
- Distal extremity fractures
- Simple, relatively stable fractures
- Ligament/tendon injuries (+/- post-sx)
Describe how a lateral coaptation splint would be applied.
Cast padding > cling > splint > vet wrap
- joints in normal functional angles
- make sure gauze is firm/tight
What 3 rules MUST be followed during any sort of coaptation?
- Radiographs following application - two orthogonal views
- Include the joint proximal and distal to injury (generally extended to the digits
- Always leave toes exposed to assess digits
How does padding technique differ between rigid pre-formed splints and malleable splints?
- Rigid pre-formed splints = pad depressions
- Malleable splints = pad protuberances
Spica splint/cast
For injuries proximal to elbow or stifle
Extends over midline
Robert Jones bandage
For injuries distal to humeral/femoral condyles
Temporary immobilization to prevent swelling/further displacement until definitive treatment/sx
Mason-Meta splint
For injuries distal to carpus/hock
Spoon splints
NOT for ulna/radius (won’t stabilize joint above/below)
Velpeau sling
Non-weight bearing sling for forelimb = scapular fx
Figure of eight sling
For coxofemoral luxations
Flexes, abducts, internally rotates the hip
BUT basically, non-weight bearing sling; doesn’t hold
Ehmer sling
For coxofemoral luxations
Figure of eight sling + wraps over midline
Flexes, abducts, internally rotates the hip
Prevents weight bearing
90/90 flexion bandage
For prevention of quadriceps tie-down/contracture = femur fx
Stifle and hock at 90 degrees
Maintains quads in extension
Five indications for external fixation
- Fractures that are comminuted, open, infected or non-union
- Arthrodesis
- Transarticular stabilization
- Limb deformities
- Traumatic wounds
List five advantageous properties of external fixators
Applied open or closed Can be adjunct to internal fixation Can make post-op adjustments Encourage early weight bearing Versatile and economical
What forces does external fixation counteract?
What type of bone healing occurs with external fixation
Forces: axial, bending, rotational (some extend, shear)
Healing: secondary b/c not rigid
Type I external fixation
Half pin splintage (both cortices, but one skin surface)
Loaded in cantilever bending
Low morbidity, least stable
Only option for humerus and femur fractures
Type II external fixation
Full pin splintage (both cortices, two skin surfaces)
Loaded in four-point bending
More stability, more morbidity
Limited to disorders distal to elbow and stifle
Type II modified external fixation
Half + full pin splintage (in one plane)
Easier to apply, comparable stabilization
Type III external fixation
Half + full pin splintage (biplanar, opposing planes)
MOST STABLE, time-consuming, difficult to see bone on rads
What is the weakest link in any external fixation construct?
Bone-pin interface
The stiffness of the pin (resistance to bending) is proportional to ________
DIAMETER to the FOURTH power
Threaded positive profile pins conserve core diameter = superior stiffness
Compare and contrast KE vs IMEX SK external fixation systems
KE:
- clamps only accept pins of limited diameter, no positive profile pins
- connecting rod weak and not radiolucent
- pilot holes difficult
IMEX SK:
- allows pilot holes, variability in pin diameter
- thick rod made of titanium or carbon fiber = simpler constructs
- better mechanics overall
Describe 11 proper external fixator application techniques (general)
- drill pilot hole
- place pins through small relief incisions
- don’t place through traumatic/sx wounds or large muscle masses
- low speed, high torque drill
- place proximal and distal pins FIRST = length
- then place near end of fx = finalize reduction
- connecting rod as close to bone/fx as possible
- fixation pin should not exceed 30% of bone diameter
- beveled tips should completely penetrate trans cortex
- min. 3-4 pins per fracture segment
- additional pins distribute force
Where are external fixators best placed on the following bones: Tibia Radius Ulna Metacarpus/MT Humerus Femur
Tibia = medial Radius = lateral proximally, medial distally Ulna usually NOT stabilized Metacarpus/MT = lateral (no biplanar) Humerus = craniolateral Femur = lateral
Four advantages of acrylic fixators
Pins can vary in diameter and don’t have to be placed in same plane
Most are radiolucent
Minimize distance b/t column and bone cortex
Lightweight, economical
Four disadvantages of acrylic fixators
Difficult to maintain reduction if used as primary fixation
Polymerization of PMMA = exothermic
Generates noxious, toxic, teratogenic fumes
Hard to make adjustments
Fixator pin should not exceed _________
30% of the diameter of the bone
Name the four implants used for intramedullary fixation in small animals.
Steinmann pins
Kirschner wires
Rush pins
Interlocking nails
3-point fixation
- Proximal epi/metaphyseal cancellous bone
- Endosteal surface of diaphysis
- Distal epi/metaphyseal cancellous bone
What forces are counteracted by intramedullary fixation?
Bending, which is proportional to the diameter of the pin to the fourth power!
NO - compression, torsion, tension
Name the three tip configurations of intramedullary pins and their attributes
Trocar = cuts easily Threaded = not used for IM pins, break where threading ends (good for ex fix) Chisel = doesn't cut as well
Are intramedullary pins suitable for stabilizing comminuted fractures?
Not alone - must be combined with ex fix or plate
Normograde vs retrograde placement of IM pins
Normograde: pin inserted at one end of bone, driven across fx site
Retrograde: pin inserted through fx site, driven out of one end then reduce and driven across fx site
Explain placing pins/wires in the manner of “rush pins”
Two pins/wires are inserted at an angle so that they cross proximal to fracture site and deflect of endosteal surface of both sides
Provides dynamic 3-point fixation “stress pinning”
K wires and Steinmann wires often used in this manner
For metaphyseal/physeal fx
Advantages afforded by interlocking nails
- controls bending, rotational, axial forces
- in central mechanical axis
- placed following closed/open reduction
- fast/simple application
- economical compared to plating
- jigs to find holes for bolts
Describe the process of interlocking nail application
Nail positioned within medullary cavity
Screws/bolts placement determined with a jig
Screws/bolts penetrate cortex to cortex, proximal and distal to the fracture
Four key points for IM pin placement in the FEMUR
Normograde just medial to greater trochanter
AVOID sciatic nerve
Over-reduction helps avoid migration to stifle joint, but prevents anatomic reconstruction
Augmented with ex fix
Three key points for IM pin placement in the TIBIA
Normograde through craniomedial aspect of tibial plateau
Medial to patellar tendon, on top of extra-articular fat pad
Cut off tip of pin so you don’t enter hock distally
Key point for IM pin placement in the RADIUS
DO NOT DO IT unless stress pinning physeal fx
Three key points for IM pin placement in the ULNA
Normograde or retrograde
Not a sole means of stabilization, but to supplement radial repairs
Incorporated with tension band technique
Three key points for IM pin placement in the HUMERUS
Retrograde more common than normograde
Exits prox through greater tubercle
Seated distally in or prox to medial portion of condyle
What is a cerclage wire and how does it function in stabilizing fractures?
Heavy gauge stainless steel wire placed circumferentially around bone to provide fragment apposition and ADJUNCTIVE fixation/stability
10 rules of proper cerclage wire application
- sufficient diameter
- 360 degree anatomic reconstruction
- oblique (or spiral) fracture
- never use single wire
- wires 1cm apart
- 5mm from end of fx segments
- no interposition soft tissue
- perpendicular to long axis of bone (unless using k wire)
- prevent slippage in regions where diameter changes
- must be tight
Why is a loose cerclage wire so detrimental for fracture healing?
A loose wire will shear the bone, disrupting vascular supply, thus impeding healing
Advantages/disadvantages of twist wires
Advantages: more resistant to distractive forces, simple to apply, re-tighten if needed, economical
Disadvantages: less final tension, oblique to long axis of bone, twist protrudes to soft tissue
Advantages/disadvantages of loop wires
Advantages: greater final tension, perpendicular to long axis of bone, does not protrude into soft tissues
Disadvantages: less resistance to distractive forces, cannot re-tighten, increased cost
How can slippage of the cerclage wire be prevented in regions of varying bone diameter?
Hemicerclage wires or k wires
K wires:
- prox cerclage wire prox to k wire
- distal cerclage wire distal to k wire
Tension band principle
Converts/redistributes distractive/tensile forces to compressive forces on the bony protuberances (where lig/tendons attach)
Used to stabilize osteotomies and fx at traction epiphyses
Four principles of internal fixation
same for SA and equine
Anatomic reduction
Stable/rigid fixation
Atraumatic technique/preserve blood supply
Early pain-free return to function
Properties of cortical screws
Thicker core = resistant to bending
Thinner threads = easier to pull out
Used in diaphyseal bone
Properties of cancellous screws
Longer threads = harder to pull out
Used in metaphyseal bone
Can also be used to rescue/replace stripped cortical screw
Properties of locking screws
Threads into plate and locks to it
Thicker core = better resistance to bending
Implant screws (traditional vs locking) vs position screws
Implant screws just means it is being incorporated ito a plate = most common usage
- traditional compress plate to bone
- locking does not compress
Position screws hold bone fragment in reduction; threads engage both cortices so there is no compression
Describe what is means to place a screw in lag fashion
Over-drill hole on near side, smaller hole on far side so that the threads only engage on the far cortex, pulling/compressing it to the near portion
(a true lag screw is partially threaded distally)
Properties of dynamic compression plates (DCP)
Hole design allows compression across fracture
Full contact b/t plate and periosteum = reduced healing
Has a hill on one side of hole, if you place eccentrically place screw it will compress fx as it moves down incline
Properties of limited contact dynamic compression plates (LC-DCP)
Reduced contact b/t plate and periosteum = increased blood supply immediately under plate
Reduces stress riser at holes
Properties of locking compression plates (LCP)
Threaded = compression
Non-threaded = cortical screw, just presses plate to bone
PLACE CORTICAL SCREWS FIRST
Plate functions:
Compare compression vs neutralization vs bridging plates
Compression: produces compression at fx site to provide absolute stability (consistent, but not faster healing)
Neutralization plate: protects primary repair mechanisms (ie: lag screw, cerclage, hemicerclage or wire) from bending, shear and torsional loading; DOES NOT COMPRESS
Bridging: acts as splint to maintain limb length and joint alignment to prevent axial deformity (bending, shear forces)
Ideal fracture situation for internal fixation with plates and screws (four characteristics)
Closed
Diaphyseal (long bone)
Adequate soft tissue coverage
Can apply on tension side of bone/break
Four basic goals for successful plate application (traditional plates)
Min. 6 cortices (3 screws on each side of fx)
Good plate/bone contact
Screw 30-40% bone diameter
Plate applied to tension side of bone
Expected healing time for a union
3-6 m/o: 4-6 weeks
>1 y/o: 12 weeks
Four causes of delayed union and whether they are biological or mechanical
Insufficient vascularity (b)
Infection (b)
Inadequate reduction and fixation (m)
Excessive post-operative activity (m)
When is surgical intervention deemed necessary for a fracture?
When there is non-union or no further evidence of further progression
Five causes of non-union and whether they are biological or mechanical
Instability at fx site (m) Poor vascularity (b) Large gap b/t segments (b/m) Soft tissue b/t segments (m) Infection and sequestration (b)
Five clinical signs of non-union
Palpable instability at fx site Muscle atrophy Limb deformity Impaired limb function/lameness Variable pain
Four radiographic signs of non-union
Distinct fracture margins
Pseudarthrosis
Sealed marrow cavity (sclerosis)
Arrest or regression of healing on serial rads
What are the three sub-classifications of a viable non-union?
Hypertrophic
Slightly hypertrophic
Oligotrophic
What are the four sub-classifications of a non-viable non-union
Dystrophic (partial healing on one side)
Necrotic
Defect (gap >1.5X diameter)
Atrophic (resorption of adjacent bone ends)
Treatment of non-union
Find out what factors are contributing and address them
- debride necrotic bone
- open medullary canal
- rigid internal fixation
- autogenous cancellous bone graft
What is the ONLY contraindication for an autogenous cancellous bone graft?
Infection
Define malunion
Inadequate fracture reduction or stabilization leading to an non-anatomic bony union = deformity
Clinical signs of malunion
Malalignment of limb
Fx site palpably stable and non-painful
Lameness/decreased ROM
DOESN’T ALWAYS CAUSE CLIN PROBLEMS
What are the three components of malunion treatment and when is it indicated?
Corrective osteotomy
Realignment
Rigid fixation
Indicated when clinical signs are present!
What two components does osteomyelitis require to occur?
vascular compromise
bacterial contamination
What are five contributing factors to osteomyelitis?
Tissue ischemia Bacterial inoculation Bone necrosis and sequestration Fracture instability = vascular compromise Foreign material implantation
Radiographic signs of osteomyelitis
Soft tissue swelling
Irregular periosteal reaction
Lysis/bone resorption
How is osteomyelitis specifically diagnosed?
Positive culture obtained by aseptic technique from deep aspirate of fx site, sequestra, local necrotic tissue or implants
NOT from draining tracts
Osteomyelitis treatment
Long-term, culture guided antibiotics +/- beads
PLUS meticulous debridement
Establish drainage
Rigid stabilization
What are some ways we can decrease the risk of osteomyelitis during fracture repair?
Prophylactic abx
Minimize duration of sx and anesthesia
Debridement
Irrigation
Describe quadriceps contracture and why it occurs
When the quads contracted for long periods of time (hock extended) resulting in fibrosis of the muscles
Usually seen in young dogs following a femoral fx = infarcts quads
Can also be caused iatrogenically from surgical “repair” or prolonged immobilization/coaptation
List five ways we can prevent quadriceps contracture
Early fx management Rigid fixation Early return to function (PT!) Only TEMP immobilization of femur 90/90 sling WANT QUADS EXTENDED, HOCK FLEXED
Treatment for quadriceps contracture
Amputation
EQ: What is classified as an orthopedic emergency?
ANY ACUTE-ONSET, SEVERE LAMENESS
EQ: What is the primary goal for fx and catastrophic traumas?
Stabilize limb for transport
EQ: Three main things to examine in equine patient with a fracture
CV status = MM, CRT
Affected limb/limbs
Evidence of trauma elsewhere
EQ: Reliable sedatives for equine fractures
Xylazine or Detomidine (alpha-2 agonists) +/- butorphanol
May need higher/repeat doses
However, avoid excessive ataxia (tend to do repeat doses over increased doses)
EQ: Which drug should be avoided for sedation and why?
Acepromazine = hypotension
EQ: Goals of fracture stabilization
Reduce pain/anxiety
Minimize further trauma
Immobilize adjacent joints
ESSENTIAL FOR TRANSPORT
EQ: Describe the method of fracture stabilization for distal MC/MT3, P1, P2, breakdown injury, or fetlock luxation for front and hindlimb (level 1)
FL: light bandage + dorsal splint
HL: light bandage + plantar splint
EQ: Describe the method of fracture stabilization for proximal 2/3 metacarpus, carpus and distal radius (level 2)
RBJ (elbow to ground) + caudal + lateral splints
EQ: Describe the method of fracture stabilization for mid/proximal metatarsus (level 2)
RBJ (hock to ground) + caudal + lateral splints
Uses calcaneal tuberosity to stabilize
EQ: Describe the method of fracture stabilization for mid/proximal radius (level 3)
RBJ (elbow to ground) + caudal + lateral splints
C: elbow to ground
L: withers to ground (CRITICAL to prevent abduction)
EQ: Describe the method of fracture stabilization for tarsus + tibia (level 3)
RBJ (stifle to ground) + lateral splint (tuber coxae to ground)
Width = resistant to rotation
Length = prevent abduction
EQ: Describe the method of fracture stabilization for humerus, scapula and femur (level 4)
No coaptation
EQ: Describe the method of fracture stabilization for olecranon. What is the classical clinical signs associated with this type of fracture?
Align bones, fix carpus in extension = allows wt bearing
Padded bandage + caudal splint (olecranon to fetlock/ground)
“CLASSIC DROPPED ELBOW” b/c triceps apparatus inserts here
EQ: Five principles of treatment for any open fracture
Clean Keep moist Bandage BS antibiotics Tetanus toxioid
EQ: Three main further treatments for fractures, ONCE STABILIZED
Analgesia: NSAIDs (flunixin, bute)
Isotonic IV fluid bolus for hypotensive shock
Radiographs (better at referral facility)
EQ: List a few factors that affect fracture prognosis(main ones)
Fx type/location Open/closed, degree of soft tissue damage Age, weight Patient behavior FIRST AID PRIOR TO REFERRAL
EQ: Six bones that are more likely amenable to healing
Phalanges Sesamoids MC/MT Carpus/tarsus Patella Ulna
EQ: Seven bones that are more likely aversed to healing
Radius Humerus Scapula Calcaneous Tibia Femur Pelvis
EQ: List some differences in fractures in foals relative to adult horses
- faster healing
- angular limb deformities (growth plate)
- SH fractures
- more prone to cast sores
- more prone to tendon laxity when splinting
EQ: Which types of fractures can be treated by stall rest? What is the risk associated with this type of treatment?
Stress, splint bones, third trochanter, patellar, deltoid tubercle
Risk: catastrophic propagation, always
EQ: How is external coaptation usually used with equine fractures?
To supplement internal fixation or emergency stabilization
EQ: List three examples of external fixation in horses
Transfixation-pin casts, external skeletal fixators, ESFD
EQ: Describe transfixation-pin casts and their indications
2-3 cross pins proximal to fracture, incorporated into cast to provide axial support and decrease rotation
Indications: comminuted phalangeal fx, distal MC/MT 3 fx, MCP breakdown
EQ: Describe external skeletal fixators and their indications
Allow immediate wt bearing, access to wounds, but often do not provide enough axial support
Indications: foals, non-wt bearing fx (mandibular)
EQ: What is the one key to a successful internal fixation fracture repair?
Intra-operative imaging, specifically CT
EQ: Which type of screw is most commonly used in equine fracture repair and why?
Cortex because stronger and more rigid than cancellous
EQ: What are the three ways/fashions a cortical screw can be placed and what is meant by each?
Position = does not compress, holds in place Implant = in a plate Lag = compressing
EQ: What is the purpose of tapping?
Creates thread holes in the drill holds to improve bone-screw interface
EQ: two main principles of plate fixation
Min. 4 screws on each side of fracture
Apply to tension side
EQ: four indications and two exceptions for implant removal
Indications: infection, loosening, lameness, return to exercise (if problem)
Exceptions: arthrodesis, screws (unless a problem)
staggered removal preferred!
EQ: List 5 common complications of implants
Implant infection Catastrophic breakdown post sx/anesthesia Osteoarthritis Limb deformities in foals Laminitis
