Midterm Flashcards
What is the strength of bone dependent on?
Material properties
Structural properties
Rate of load applied (viscoelastic)
Orientation of applied load (anisotropic)
What are the different types of forces you can put on a bone?
Tension Compression Shear Bending Torsion
Which force produces elongation, creates avulsion fractures, and occurs at apophyses?
Tension
Which force is the opposite of tension and tends to create short oblique fractures? This is the force in which bone strongest.
Compression
Which force is eccentric loading of a bone’s surface? This is the force in which bone is weakest.
Shear
Which force results in compressive and tensile forces and causes transverse or short oblique fractures?
Bending
Which force includes rotational forces applied along the long axis of a bone and results in spiral fractures?
Torsion
*What forces cause oblique fractures?
Axial compression and bending forces
Which fracture type has limited inherent stability?
Oblique
Which fracture type is inherently stable is anatomically reduced?
Spiral
What are the classifications for open fractures?
I: Clean soft tissue laceration <1 cm
II: Soft tissue laceration >1 cm; mild trauma, no flaps or avulsion
IIIa: Soft tissue available for wound coverage despite vast laceration, flaps, or high energy trauma
IIIb: Extensive, soft tissue injury loss periosteum stripped and bone exposed
IIIc: Arterial supply to the distal limb damaged; arterial repair indicated
What are the different Salter-Harris classifications of fractures?
I: Physis (separation)
II: Metaphysis/physis
III: Epiphysis/physis
IV: Metaphysis/physis/epiphysis
V: Physis (compression)
What do articular fractures demand?
Anatomic reduction and rigid stabilization!
What do you always need to include in radiographs of a fracture?
Always include the joint proximal and distal to the fracture
Always obtain two orthogonal views of the bone
What is a fracture assessment score?
Score that assess the risks associated with a fracture repair
1-10, (1 being high risk, 10 being little risk)
Depends on clinical assessment (owner compliance, patient compliance, comfort level), mechanical assessment (type of fracture, pre-existing conditions, type of dog), and biological assessment (old patient, soft tissue envelope, velocity of injury)
What is the primary objective of fracture management?
Promote an early and complete return to function
What is the difference between anatomic reconstruction and biological fixation? Which is more common?
“The Carpenter”: Anatomic reconstruction is anatomic reduction and rigid fixation to promote weight-bearing and fracture healing
“The Gardner”: Biological fixation aims to preserve the vascular supply to the bone using bridging osteo-synthesis (ex fix, IM pins)
Biological is becoming more commonly used
What is the difference between reduction and alignment?
Anatomic reduction is putting everything back in its normal, anatomical position
Alignment refers to the orientation of joints proximal and distal to the fracture and has a greater impact on function
Anatomic reduction is not necessary to achieve anatomic or at least functional alignment
What is secondary bone healing?
Includes inflammatory, reparative, and remodeling phases of bone healing and is dependent on callus formation to heal
What is primary bone healing?
Requires anatomic reduction and rigid fixation
Associated with minimal callus formation
Contact healing or gap (<1mm) healing
When would a callus be evident on radiographs in a fracture healing by secondary bone healing?
2-4 weeks
What is bone grafting?
The transfer of bone from one site or source to another to facilitate and promote bone healing (osseous union)
What are the indications for bone grafting?
To enhance union in acute, nonunion or delayed union fractures
Replace areas of bone loss
Stimulate fusion of arthrodeses
What are the types of bone grafts?
Immunologic (auto, allo, xeno)
Histologic (cancellous, cortical, corticocancellous)
What are the functions of bone grafts?
Direct osteogenic effects (only fresh autografts)
Osteoinduction
Osteoconduction
Structural support
What are the common source sites for cancellous bone in bone grafting?
Greater tubercle
Iliac crest
Proximal tibia
What is osteoinduction?
Type of bone grafting that utilizes recruitment and differentiation of osteoprogenitor cells
Induces bone synthesis
Uses bone morphologic proteins
What is osteoconduction?
Bone graft in which the graft provides scaffolding for in-growth of capillaries and mesenchymal cells
Graft is eventually resorbed and replaced
What type of bone graft provides structural support?
Cortical allografts
What is coaptation?
Extra-corporal treatment modalities for musculoskeletal abnormalities
Casts, splints, slings, bandages, etc.
When is coaptation contraindicated?
Following open reduction and internal fixation
Will not increase stability and promotes fracture disease
What are the three different types of coaptation?
Schanz soft padded bandage
Lateral coaptation splints
Full and half cylinder casts
How would you pad the limb differently in rigid pre-formed splints and malleable splints?
Rigid pre-formed splints: pad depressions
Malleable splints: pad protuberances
What is one thing to remember with any type of coaptation of the limb?
LEAVE THE DIGITS EXPOSED
What is the cardinal rule of coaptation?
The joint proximal and distal to the injury must be immobilized!
*Which splint is most commonly used following closed reduction of elbow luxation?
Spica splint
Coaptation which extends proximally over midline
For what kind of injuries would you use a Robert Jones bandage?
Injuries distal to the elbow or distal to the stifle
For what type of injuries would you use a Mason-Meta Splint?
Injuries distal to the carpus and hock
Inappropriate for fractures of the radius and ulna!
For what type of injuries would you use a Velpeau sling?
Used for scapular fractures and some shoulder injuries
Prevents weight-bearing on forelimb
When would you use a Figure-of-8 sling?
Following reduction of coxofemoral luxations
Flexes, abduct, and internally rotates the hip and prevents weight-bearing of the hindlimb
When would you use an Ehmer sling?
Following reduction of coxofemoral luxations
Flexes, abducts, and internally rotates the hip and prevents weight-bearing of hindlimb
More effective than Figure-of- sling
When would you use 90/90 Flexion bandage?
Used to prevent “quadriceps tie-down” by maintaining the quadriceps mechanism in extension by keeping the stifle and hock at 90 degrees
Prevents weight-bearing
Used as a form of physical therapy to increase range of motion
What are the indications for external fixation?
Comminuted fractures
Open fractures
Infected and nonunion fractures
Arthrodeses
Transarticular stabilization
Limb deformities
What are the different types of external fixators?
Linear
Acrylic
Circular
Hybrid
What are the different nomenclatures (Type I, II, III) of external fixators?
Type I: Half-pin splintage and is uniplanar and unilateral (pins go through both cortices but only one skin surface)
Type II: Full-pin splintage and is uniplanar but bilateral (pins go through both cortices and skin surfaces)
Modified Type II: Utilizes both half and full-splintage
Type III: Utilizes both half and full-pin splintage and is biplanar and bilateral
What is the application of Type II external fixators limited to?
Disorders distal to the elbow and stifle
Due to impingement of the medial connecting column with the body wall
What is the weakest part of the external skeletal fixation construct?
The bone-pin interface
What are the disadvantages of the Kirschner-Ehmer (KE) Apparatus?
Cannot place positive profile pins directly through clamps
Pre-drilling pilot holes is difficult
Difficult to place a series of parallel full-pin splintage pins
Connecting system is not radiolucent
Connecting clamps only accept pins of limited diameter
Te connecting rod is relatively weak
What is the IMEX SK External Fixation System?
Innovative clamp design that allows pre-drilling of pilot holes and allows for variability in fixation pin diameter with better mechanics
Increased stability
What are some general guidelines for placing pins?
Place pins through small incisions
Don’t place pins through traumatic or surgical wounds
Close surgical wounds prior to placing pins
Avoid large muscle masses
What level of speed and torque would you use to drill your pilot hole? Place the fixation pin?
Pilot hole: High speed, low torque
Fixation pin: low speed, high torque
In what order do you place external fixator pins?
Place proximal and distal pins first
Place intermediate pins next, near the ends of the fracture segment
*Fixation pin diameter should not exceed what percentage of the diameter of the bone?
30%
The stiffness of a pin is proportional to what?
Radius ^ 4
What are the advantages of acrylic connecting columns?
Pins can be any diameter
Pins don’t have to be placed in the same longitudinal plane
Most are radiolucent
Minimizes the distance between connecting column and the cis-cortex of the bone
Light in weight
Limited inventory and expense
What are the disadvantages of acrylic connecting columns?
Difficult to maintain reduction if used for primary fixation
Polymerization of PMMA is an exothermic reaction
Fumes generated during polymerization of PMMS are neurotoxic and teratogenic
Difficult to make adjustments or remove individual interior fixation pins
What is the most common form of internal fixation?
Intramedullary Fixation
What are the different typed of intramedullary implants?
Steinmann pins
Kirschner wires
Rush pins
Interlocking nails
What are the three points of intramedullay fixation?
- Proximal epiphyseal/metaphyseal cancellous bone
- Endosteal surface of diaphysis
- Distal epiphyseal/metaphyseal cancellous bone
What forces do intramedually pins resist?
Bending forces!
No resistance to compression, torsion, or tension
Little resistance to shear
What are the three types of tips for intramedually pins?
Trocar
Threaded
Chisel
How do you insert an intramedually pin?
Manually with a Jacob’s chuck or low speed power drill
Normograde: pin is inserted at one end of the bone and driven across the fracture site
Retrograde: Pin is inserted through the fracture site, driven out one end of the bone, reduced and driven across the fracture site
What do you do with the ends of a pin after inserting an intramedually pin?
End cut flush with the bone: less irritation, difficult to retrieve)
End cut and countersunk: no irritation and difficult to retrieve
“Tied-In” (articulated): contributes to stability, prevents migration, easily retrieve, increased morbidity
What are Kirschner “K” Wires?
Small diameter, flexible trocar tipped pins
Divergent, trans-cortical implants (makes an X)
Used in small dogs and cats
Used in “the manner of Rush pins”
What are Rush Pins?
Curved, elastic pins which provide dynamic three-point fixation
Kirschner wires or small diameter Steinmann pins are often used “in the manner of Rush pins”
What is Stress Pinning?
Dynamic intramedually cross pins places “in the manner of Rush pins”
Pins are inserted at an angle such that the pins deflect off the endosteal cortical surfaces
May provide added strength
Commonly used in metaphyseal or physeal fractures
What are Interlocking Nails (intramedullary fixation)?
Nails positioned within the medullary cavity are penetrated (perpendicularly) with screws or bolts
At least one or two screws/bolt proximal and distal to the fracture
Placement determined with a “guide jig”
What are the advantages of interlocking nails in intramedullary fixation?
Controls bending, rotational, and axial forces
Application fast and simple
Economical
What is the preferred method of pin placement in intramedullary fixation of the femur?
Normograde
*What is the preferred method of pin placement in intramedullary fixation of the tibia?
Normograde
What should you be careful about when placing an intramedullary pin in the femur?
Avoid sciatic!
What should you be careful about when placing an intramedullary pin in the tibia?
Do not enter the hock distally!
Don’t use malleoli as landmarks! They go past the end of the tibia
Cut the tip of the pin off
Should you open the joint capsule when placing an intramedullary pin in the tibia?
No
What should you know about intramedullary fixation of the radius?
DO NOT PIN THE RADIUS
JUST SAY NO
How should you place intramedullary pins in the ulna?
Normograde or retrograde (either)
How should you place intramedullary pins in the humerus?
Normograde or retrograde (retrograde is most common)
Greater tubercle to medial condyle
What is the definition of cerclage wire?
Heavy gauge stainless steel wire placed circumferentially around bone to provide fragment apposition and adjunctive fixation
What is the main function of cerclage wires?
Provide fragment apposition but inadequate stability to resist the forces of weight-baring alone
Neutralizes rotational, shearing, axial, and bending forces
What is required for correct application of a cerclage wire?
360 degree anatomic reconstruction of the cylinder of bone at the level the wires are placed
What are the main differences in the biomechanics of twist knots and loop knots?
(Lecture sites paper findings)
Loop knots produced greater tension than twist knots
Twist knot cerclage wires lost significant tension if bent over but provided greater resistance to distractive forces
Knot resistance to distractive forces increased with increasing diameter of the wire
What are the advantages and disadvantages of twist wires?
Advantages: More resistant to distractive forces Simpler to apply Wires can be re-tightened More economical
Disadvantages:
Final tension inferior to loop wires
Situated obliquely to the long axis of the bone
Twist protrudes into the surrounding soft tissue
What are the advantages and disadvantages of loop wires?
Advantages:
Greater final tension
Situated perpendicular to the long axis of the bone
Does not protrude into surrounding soft tissue
Disadvantages: Less resistant to distractive forces Cannot re-tighten More cumbersome to apply Increased cost
What are the 10 Commandments of cerclage wires?
- Wire must be of sufficient diameter
- Need 360 degree anatomic reconstruction
- Fracture must be oblique
- Never use a single wire
- Wires should be 1cm apart
- Wire must be 5mm from end of fracture segments
- No interpositioned soft tissue
- Wires must be placed perpendicular to the long axis of the bone
- Prevent slippage in regions where bone changes diameter
- Wires must be tight
*What is the main function of pin and tension band fixation?
Convert distractive forces to compressive forces
What are the 4 principles of internal fixation?
- Anatomic reduction
- Stable fixation
- Atraumatic technique of bone and soft tissue
- Early pain free return to function
What are the 4 common screw designs?
- Cortical
- Cancellous
- Lag
- Locking
What is the difference between cortical and cancellous screws?
Cortical has a larger core, used in diaphysis
Cancellous has larger threads, used in softer/metaphyseal bone
What is the difference between a cortical screw and a locking screw?
Locking screw has a threaded head
What is the most common use of screws?
Implant screws
What are position screws?
Screws used to aid in initial reductio by holding bone fragment in place
Does not provide compression
What is the main goal of placing a screw in lag fashion?
Compression
What are the common plate types?
Dynamic compression plates (DCP)
Limited contact dynamic compression plates (LC-DCP)
Locking plate (LCP)
Specialty plates
What are the common plate functions?
Compression
Neutralization
Bridging
What is the function of a compression plate? Neutralization plate? Bridging plate?
Compression: Produces compression at the fracture site to provide absolute stability
Neutralization: Protects interfragmentary stabilization via lag screw, cerclage, hemicerclage, or wire from bending, shear, and torsional loading
Bridging: Acts as a splint to maintain limb length and joint alignment, prevents axial deformity via bending or shear forces
What is the ideal fracture situation for internal fixation?
Closed Diaphyseal Long bone Adequate soft tissue coverage Can apply on the tension side of the bone
What are some basic goals for successful plate application?
6 cortices minimum on each side of the fracture
Plate contoured to bone
Screw are 30-40% bone diameter
Appropriate plate size
Plate applied to tension side of the bone
What are the main orthopedic complications?
Delayed unions
Nonunion
Malunion
Osteomyelitis
Quadriceps contracture
What is the expected time for normal fracture union?
3-6 mo old: 4-6 weeks
> 1 year old: 12 weeks
What are the two main things normal fracture healing (without complications) requires?
Blood supply
Stable conditions
What are the two biggest biological causes of delayed union?
Insufficient vascularity
Infection
What are the main mechanical causes of delayed union?
Inadequate reduction and fixation
Excessive post-op activity
What is a possible result of delayed union?
Implant failure secondary to implant fatigue
In nonunion, what is necessary for the bone to heal?
Surgical intervention
What are possible etiologies for nonunion?
Instability
Poor blood supply
Large gap between fracture segments
Soft tissue between fracture segments
Infection and sequestration
What are the clinical signs of nonunion?
Palpable instability at fracture site
Muscle atrophy
Limb deformity
Impaired limb function
Lameness
Variable pain
What are the radiographic signs of nonunion?
Fracture margins distinct
Pseudoarthrosis
Sclerosis (sealed marrow cavity)
Serial evaluation reveals arrest or regression of healing
How do you classify a nonunion?
Viable
Non-viable
What are characteristics of a viable nonunion?
Hypertrophic (elephant foot)
Slightly hypertrophic (horse foot)
Oligotrophic (no signs of healing, treated as non-viable)
What are characteristics of a non-viable nonunion?
Dystrophic (poor vascularized fragment with partial healing)
Necrotic
Defect
Atrophic (resorption of adjacent bone ends)
How do you treat a nonunion?
Consider underlying cause
Debridement of necrotic bone
Opening of medullary canal
Rigid internal fixation
Autogenous cancellous bone graft
What causes a malunion? What can it result in?
Inadequate fracture reduction or stabilization
Position is not anatomic
Results in an angular, rotational, distracted, or over-riding deformity
Does a malunion always cause clinical problems?
No
What are the clinical fidings with a malunion?
Malalignment of limb
Fracture site palpably stable and non-painful
Lameness and/or decreased range of motion
What is the treatment for malunion?
Corrective osteotomy
Realignment
Rigid fixation
When is surgery indicated for malunion?
When there is:
Impaired limb function
Stenosis of pelvic canal
Jaw malocclusion
Patellar luxation
What is osteomyelitis?
Inflammation of the bone and marrow
usually infectious in etiology
Adjacent soft tissue often involved
What is the most common clinical entity in small animal practice?
Chronic, post-traumatic osteomyelitis
What are contributing factors to osteomyelitis?
Tissue ischemia
Bacterial inoculation
Bone necrosis and sequestration
Fracture instability
Foreign material implantation
What are the radiographic findings associated with osteomyelitis?
Soft tissue swelling
Irregular periosteal reaction far from fracture
Lysis/bone resorption
May be difficult to distinguish from normal healing or bone tumor
What is a sequestrum?
Necrotic bone fragment
What is an involcrum?
Periosteal reaction surrounding a sequestrum
What is a cloaca?
Opening in involcrum, resulting in drainage
How do you diagnose osteomyelitis?
Positive culture
How do you treat osteomyelitis?
Meticulous debridement
Removal of all foreign material
Establishment of drainage
Rigid stabilization
Long-term antimicrobial therapy
Will antibiotics alone cure osteomyelitis?
NO
How can you minimize infection associated with fracture repairs?
Prophylactic antibiotics
Minimize duration of surgery/anesthesia
Debridement
Irrigation
Post-op cultures
What are predispositions for quadriceps contracture?
Young, growing dogs
Femoral fracture
Excessive fibrous tissue
What causes quadriceps contracture?
Quadriceps trauma with prolonged immobilization
How can you prevent quadriceps contracture?
Early fracture management
Rigid fixation
Early return to function
Only temporary (or no) immobilization
What is the treatment for quadriceps contracture?
Limb amputation
What is considered an equine orthopedic emergency?
Any acute-onset, severe lameness
What is the primary goal in initial management of an equine fracture?
Stabilize limb for transport
What type of sedation would be appropriate in equine emergency fracture assessment?
200mg xylazine + 5mg butorphanol
Or
5mg detomidine + 5mg butophanol
What should you avoid when sedating an equine patient with an orthopedic emergency?
Excessive ataxia
Acepromazine (hypotension)
What are the goals of equine fracture stabilization?
Reduction of pain and anxiety
Minimize further trauma
Immobilize adjacent joints
What are the goals of splinting equine fractures?
Neutralize damaging forces
Not overly cumbersome
Can be applied in difficult circumstances
Does not require anesthesia
Economical and accessible
Span the joint above and below when possible
How would you bandage distal fractures (equine)?
Align dorsal cortices into straight line
Neutralize bending forces at fetlock joint and fracture site
Apply a light compression bandage (1,/2” thick)- NOT robert jones
How would you bandage a mid-forelimb fracture (equine)?
Maintain bony alignment and immobilize distal to fracture site
Robert Jones bandage, ground to elbow (diameter = 3x limb)
Caudal and lateral splints
How would you bandage mid and proximal metatarsal fractures (equine)?
Stabilize by using calcaneal tuberosity as extension of MT3
Apply lateral and plantar splints over Robert Jones bandage bandage
Caudal splints should extend from calcaneus to ground
What is the main goal of bandaging mid and proximal radial fractures (equine)
Prevent abduction
Can lead to open fracture!
How would you bandage mid and proximal radial fractures (equine)?
Robert Jones bandage with caudal splint (elbow to ground) and lateral splint (withers to ground)
What is the main goal of immobilizing tarsus and tibial fractures (equine)?
Prevent abduction
How would you bandage tarsal and tibial fractures (equine)?
Apply Robert Jones bandage from stifle to ground
Lateral splint from tuber coxae to ground
Width- resistance to rotational forces
Length- prevents abduction
How do you bandage fractures proximal to elbow (equine)?
You don’t. No coaptation.
What is the goal of coaptation for olecranon fractures (equine)?
Align bones
Fix carpus in extension
Allow weight bearing
Padded bandage (Not RJB)with caudal splint
How would you bandage a fracture proximal to the stifle (equine)?
You don’t. No coaptation.
Bandaging/splinting could increase trauma by creating a pendulum effect.
How do you manage an open fracture (equine)?
Clean woumnd before bandagin
Keep moist
Broad spectrum antibiotics
Tetanus toxoid
Analgesia
What analgesia should be provided to equine patients with fractures?
1.1 mg/kg flunixin meglumine
Or
4.4 mg/kg phenylbutazone IV
When is the best time to take radiographs of a fracture in equine patients?
At the referral hospital
What are some key guidelines for transporting horses with fractures?
Minimize the distance the horse must walk
Hindlimb fractures: face front
Front limb fractures: face back
What does fracture prognosis in equine patients depend on?
- Type, number, and location of fractures
- Open vs closed
- Degree of soft tissue damage or vascular injury
- Age, breed, and weight of the horse
- Nature of patient
- Time between injury and repair
- Effectiveness of first aid before referral
Fractures in what bones are amenable to repair in equine?
Phalanges Sesamoids MC/MT Carpal Tarsal Patella Ulna
Fractures in what bones are difficult to repair in equine?
Radius Humerus Scapula Calcaneus Tibia Femur Pelvis
What are some unique characteristics of fracture healing in foals?
Heal faster than adults
Prone to angular limb deformities
Salter-harris fractures
More prone to cast sores and tendon laxity
Stall rest is used for what kind of fractures?
Stress fractures
Splint bone fractures
third trochanter, deltoid tubercle
What is the main risk of stall rest in fracture management?
Catastrophic propagation
What splint is commonly used in fractures of small ruminants?
Thomas-Schroeder splint
What are the indications for transfixation-pin casts in equine patients?
Comminuted phalangeal fractures
Distal MC/MT III fractures
MCP breakdown
When are external fixators used in equine patients?
Usually with non-weightbearing fractures (mandible)
Foals
(Often do not provide enough axial support for anything else)
What external fixator was specifically developed for comminuted phalanx, MC/MT III or MCP breakdown (equine)?
U-shaped apparatus with transosseus pins incorporated into tapered sleeves
What are the key principles for internal fixation (equine)?
Anatomical reduction
Rigid fixation
Preservation of blood supplies
Early mobilization
What is the minimum number of screws that need to be placed on each side of a fracture when plating in equine patients?
4
What is the function of plate luting in equine fracture repair?
Optimized contact between plate and bone using PMMA
Increases frictional forces “lags” plate to bone
(Not performed in small animal)
When should you remove implants (equine)?
Infection/loosening/lameness
Problems when returning to exercise
Screws: generally don’t remove unless there is a problem. Then -> staggered removal
What are possible complications of fracture repair in horses?
Implant infection
Catastrophic breakdown
Osteoarthritis
Angular or flexural limb deformities (foals)
Supporting limb laminitis (founder)
