SASx Exam I Material Flashcards
What determines the bending strength of a screw?
Core diameter
T/F: Animals with partial-thickness burns involving less than 15% TBSA require minimal supportive therapy, whereas those with burns involving more than 15% TBSA require emergency supportive care
True
T/F: For the best lag screw function, partially-threaded cancellous screws should be used
False
cortical screws are best
T/F: Surgical drains should never be placed directly under the suture line
True
This would increase risk of dehiscence
In the case of quadriceps contracture, muscle fibers are replaced by __________
fibrous tissue
Muscle fibers are replaced by fibrous tissue; adhesions form between muscle and bone. Changes result in severe decrease in limb mobility. Periarticular fibrosis/joint ankylosis/DJD further inhibits limb function. This is often irreversible
If a dog presents with burns covering both of his hind limbs and his tail, approximately what percentage of his total body surface area (TBSA) is burned?
~37%
- Each hind limb is ~18% TBSA. The tail is ~1%.*
- 18 + 18 + 1 = 37*
What type of flap is pictured below?
Single Pedicle Advancement Flap
- Donor skin available on only one side
- Subdermal plexus flap
- Used when simple undermining and advancement would result in excessive tension or distortion of surrounding tissue
What type of fixator is shown in the image?
Type I a
What percentage of the intramedullary canal should be filled when an intramedullary (IM) pin is used with cerclage wire?
70%
You see a dog on emergency with a laceration as a result of a dog fight. You debride and lavage the wound but are not sure it is appropriate for closure so you decide to leave it open for additional observation and lavage. Two days later you decide it is ready for closure. What type of closure is this?
Delayed primary closure
T/F: Hybrid fixators are useful for treatment of metaphyseal fractures
True
How far apart from the fracture ends should cerclage wires be placed?
0.5 cm
T/F: Tightening a position screw pulls the trans cortex closer to the cis cortex causing compressions across the fracture
False
Tightening a _lag screw_ pulls the trans cortex closer to the cis cortex causing compressions across the fracture
_Position screws_ are placed across a fracture line to hold a fragments in place; No compression across the fracture is achieved
T/F: Split-thickness graft is the most common type of skin grafting technique
No.
Full-thickness graft is the most common grafting technique
What is the best method for intraoperatively detecting radiolucent foreign bodies?
Ultrasound
The ratio of volume of open space to volume of total bone is termed:
Porosity
When placing cerclage wires, they should be placed ~0.5 cm from the fracture ends. How far apart from each other should they be placed?
~0.5 - 1.0x bone diameter
T/F: Drains should always exit through the primary incision to prevent excessive maceration to tissues
False
Drains should never exit thru the incision line! This may inhibit proper wound healing
When a wound is closed within 1 to 3 days after injury, when they are free of infection but before granulation tissue has appeared, this is known as:
delayed primary wound closure
T/F: When using external skeletal fixation, fractures will heal by primary bone healing
False.
When using external skeletal fixation, fractures will heal by secondary bone healing
What are the risk factors associated with quadriceps contracture?
- Distal femoral fractures
- Young patients (< 6 months)
- Prolonged immobilization
- Extensive muscle/ST trauma
What type of closure is shown here?
secondary closure
wound closure after granulation tissue covers the wound
T/F: You should never use orthopedic wire as a sole method of fracture fixation, with the exception of some mandibular fractures
True
With what bone plate application does the implant bear all of the weight load at the level of the fracture?
Bridging plate application
- No load sharing at level of fracture due to lack of anatomic reconstruction
- Screw holes left empty at level of fracture
- Micro-motion at fracture site promotes secondary bone healing
T/F: Intramedullary pins have good resistance to bending forces, but poor resistance to axial and rotational forces
True
When placing transfixation pins, pins should be placed ____ away from the fracture and each other
When placing transfixation pins, pins should be placed 1/2 bone diameter away from the fracture and each other
What types of fractures are suited for repair/stabilization via cross pinning?
simple, transverse fractures close to the joint
- Usually young animals, Salter Harris I and II
- Fragments must have good contact to provide load sharing
What type of screw is best for use in metaphyseal and epiphyseal bone?
Cancellous Screws
-
Best for use in metaphyseal and epiphyseal bone (trabecular bone)
- Increased outer diameter to core diameter ratio
- Deeper thread
- Larger pitch
Name the cerclage wiring technique used on short oblique fractures in conjunction with a K-wire:
Skewer pin
Screw diameter should not exceed ____% of bone diameter when used in diaphyseal bone
40%
Screw diameter should not exceed 40% of bone diameter when used in diaphyseal bone
Cortical bone has a porosity of ~______%
5-10%
What is the term used for the dotted line in the image below?
bridging incision
Incision (red arrow) that connects base of flap and recipient site – avoids having to tube flap over intact skin
What is the most common complication associated with external skeletal fixation?
Pin tract morbidity/drainage/infection
Povidone iodine’s duration of activity in a wound is approximately:
4-6 hours
What are the general indications for external coaptation?
fractures below the knee and the elbow
- Minimally displaced fractures and those amenable to reduction
- Transverse, simple, closed fractures
- Greenstick fractures
- Non-articular fractures
What are the two types of non-union fracture healing complications?
viable and non-viable
- Viable: Biologically active fracture with cartilage and fibrous tissue between fracture ends
- Nonviable: Fracture ends are sclerotic with rounded bone edges and visible fracture gap
A wound is left open for 2-5 days and closed prior to visible formation of granulation tissue. How would you classify this wound closure?
Delayed primary closure
What are the “Four A’s” of radiographic evaluation when reviewing post-op or recheck radiographs of a fracture repair?
Apposition, Alignment, Apparatus, Activity
-
Apposition
- Are fracture fragments well apposed?
- Not important w/ biologic osteosynthesis
-
Alignment
- Are the joints above and below the fracture aligned to promote normal limb use?
- Include joints in all x-rays
-
Apparatus
-
Is the fixator/implants appropriately positioned?
- Screw/pin length and positioning
- No penetration of joint surfaces
- Is there evidence of implant loosening or failure?
-
Is the fixator/implants appropriately positioned?
-
Activity. Is there evidence of:
- Bone healing; infection; osteopenia; malunion
What is the most common source of surgical wound contamination?
patient’s endogenous flora
When placing a transfixation pin, the pin diameter should be no more than ___% of the bone diameter
25%
When placing a transfixation pin, the pin diameter should be no more than _25%_ of the bone diameter
What are the two approaches to internal fixation?
- open anatomic reduction/reconstruction
- biological osteosynthesis
What type of bone plate would be appropriate for fractures of curved bones (mandible, ileum, etc.)?
reconstruction plate
What wound dressings would you use to promote granulation tissue formation?
calcium alginate, honey, sugar, maltodextrin
Name the forces that are overcome by external coaptation:
bending & rotation (to a degree)
When using conventional bone plates, stable repair requires screw purchase of at least ____ cortices above and below fracture
Six
When using conventional bone plates, stable repair requires screw purchase of at least 6 cortices above and below fracture
What does the acronym MIPO stand for?
Minimally Invasive Plate Osteosynthesis
How would you classify this open fracture?
Type II
-
Open wound > 1 cm in size
- Wound from external source
- Mild soft tissue trauma-Without extensive soft tissue damage
- No flaps or avulsions
Debridement that begins at the top layer and works toward the deepest describes:
layered debridement
How soon before surgery are pre-sutures usually placed?
<24 hours
Usually placed the day before surgery. Pre-suturing takes advantage of the properties of mechanical creep and stress relaxation
Salter-Harris Type ____ fractures run through the physis and the epiphysis and are generally articular fractures
Salter-Harris Type III fractures run through the physis and the epiphysis and are generally articular fractures
__________ fractures have multiple fracture lines
comminuted
Comminuted fractures have multiple fracture lines
A __________ fracture, occurring in immature animals, is an incomplete fracture in which a portion of the cortex is intact, thus stabilizing the bone to some extent
greenstick
A greenstick fracture, occurring in immature animals, is an incomplete fracture in which a portion of the cortex is intact, thus stabilizing the bone to some extent
Identify the type of external skeletal fixator:
Type Ia
unilateral-uniplanar
What two types of Salter Harris fractures might go undiagnosed on initial radiographs?
Type I and Type V
Cancellous bone has a porosity of ~_____%
75-95%
What bone plate mode is used in biological osteosynthesis/MIPO?
bridging mode
-
Plate spans fractured area which cannot be anatomically reconstructed (comminuted area)
- Plate must “bridge” fracture gap
-
Plate bears all load at level of fracture
- No load sharing at level of fracture due to lack of anatomic reconstruction
- Screw holes left empty at level of fracture
- Micro-motion at fracture site promotes secondary bone healing
- Longer plate with fewer screws
In biomechanics, what is the term for the point at which a material transitions from elastic to plastic deformation?
Yield Point
When a wound is closed immediately, this is known as:
primary closure
What bone plate type is illustrated below?
dynamic compression plate (DCP)
Wound closure after granulation tissue formation is considered what type of closure?
Secondary closure
What antibiotic is the best first choice for treatment of an open fracture?
Cefazolin
If a dog presents with burns covering his left front limb and his right hind limb, approximately what percentage of his total body surface area (TBSA) is burned?
~27%
- Front limb is ~9% TBSA. Back leg is ~18%*
- 9 + 18 = 27*
Which of the following three types of screws is the strongest under bending stress:
cancellous, cortical, locking
locking screw
The locking screw is strongest under bending stress b/c it has the largest core diameter; it’s only placed perpendicularly to the plate hole
What are the four primary bone tumors diagnosed in our small animal population?
osteosarcoma, chondrosarcoma, fibrosarcoma, hemangiosarcoma
Salter-Harris Type ____ fractures run through the physis and a portion of the metaphysis
Salter-Harris Type II fractures run through the physis and a portion of the metaphysis
To reduce a fracture, implants are placed through incisions distant to the fracture itself.
This describes what approach to fracture reduction?
minimally invasive osteosynthesis
-
Implants are placed through incisions distant to the fracture
- Fracture is not approached
- Closed reduction
- I**ntra-operative fluoroscopy is used to guide placement of implants and to confirm fracture reduction and alignment
- Steep learning curve
**is thought to promote faster bone healing**
T/F: Mechanically, a properly applied cast immobilizes the joints above and below the fractured bone, neutralizing bending, rotational, and axial forces on the fracture
False
- Mechanically, a properly applied cast immobilizes the joints above and below the fractured bone, neutralizing bending and rotational forces on the fracture.*
- A cast does not counteract axial forces applied to the fractured bone*
What technique is used to stabilize Salter Harris Type 1 fractures of the proximal humerus?
Diverging Pin Technique
How would you classify an open fracture with bone exposure and extensive soft tissue loss?
Type III B
__________ fractures occur when the insertion point of a tendon or ligament is fractured and distracted from the rest of the bone
avulsion
Avulsion fractures occur when the insertion point of a tendon or ligament is fractured and distracted from the rest of the bone
What type of screw has the largest core diameter?
locking screws
-
Screw type with largest core diameter
- 3.5 mm locking screw = 2.9 mm core diameter
- 3.5 mm cortical screw = 2.4mm core diameter
- Self-tapping
-
Threaded head locks into threaded hole in locking plate
- Can only be placed perpendicular through hole
- Only for use with locking plates
Briefly describe the “open but do not touch” approach to fracture reduction:
- Fracture is surgically approached and visualized
-
Fracture ends are NOT manipulated during placement of implants
- Fracture reduced via traction or manipulation of bone away from fracture
- Minimal disturbance of fracture hematoma, periosteum, and blood supply
What type of bone plate is most often used for minimally invasive plate osteosynthesis (MIPO)?
locking plate (LCP)
What percentage of the intramedullary canal should be filled when an intramedullary (IM) pin is used along with plating?
35-40%
When using locking bone plates, stable repair requires screw purchase of at least ____ cortices above and below fracture
Four
When using locking bone plates, stable repair requires screw purchase of at least 4 cortices above and below fracture
What fracture configuration is ideal for the use of cerclage wire?
Long Oblique
Fracture line should be greater than 2x the diameter of the bone
Dynamization is typically recommended at ~_____ post-repair
Dynamization is typically recommended at ~6 weeks post-repair
Dynamization is the Incremental destabilization of the construct. This allows increased axial loading of the fracture to enhance callus hypertrophy and remodeling of the fracture
Identify the type of external skeletal fixator:
Type IIb
bilateral-uniplanar; use of full pins and half pins
What is the difference between anatomic and physiologic degloving injuries?
- Physiologic: skin devitalized but still in place
- Anatomic: skin avulsed from underlying tissue
“bone remodels based on the forces that are applied” describes what theory?
Wolff’s Law
What fixation methods (2) cannot be used in the radius?
Interlocking nails and Intramedullary pins
T/F: Tension bands are appropriate for many long oblique fractures
No.
Tension bands are indicated for avulsion fractures and some osteotomies
surgical immobilization of a joint by fusion of the adjacent bones is termed:
arthrodesis
T/F: Punch grafts are used to enhance epithelization
True
T/F: Lag screws should be positioned parallel to the fracture line
False
Lag screws should be positioned PERPENDICULAR to the fracture line
When is the diverging pin technique used?
to stabilize Salter Harris 1 fractures of the proximal humerus and the femoral head
Elastic Plate Osteosynthesis is only appropriate for what type of patient?
skeletally immature animals
less than 5-6 months of age is ideal
T/F: There is less risk of infection with active drains compared to passive drains
True
The most common bone plates are composed of stainless steel and are very stiff. How do these plates fail?
bending forces
Classify this open fracture
Type I
A type I open fracture is caused by the bone penetrating through the skin and is characterized by a small puncture hole located in the skin in the proximity of the fracture. Depending upon the amount of soft-tissue coverage, the bone may or may not be visible in the wound.
What type of fixation would be best for treatment of a Grade IIIA open fracture?
External Skeletal Fixation
What fractures must always be anatomically reconstructed?
Articular fractures
T/F: Interlocking nails are used to treat diaphyseal comminuted fractures
TRUE
This plate is being used in __________ mode
buttress
- Used in a metaphyseal fractures to prevent collapse of the adjacent articular surface
- Will frequently incorporate lag screws
-
Plate is subject to full loading
- Axial forces do not help with fracture compression and do not promote load sharing by the bone)
- Plate supports cortex and resists displacement
- Most or all screw holes should be filled
Name the condition that can occur when a young animal’s comminuted femoral fracture is treated with rigid immobilization for an extended period of time
Quadriceps contracture
What types of fractures are best repaired by tension band?
avulsion fractures and some osteotomies
What is the general goal of Minimally Invasive Plate Osteosynthesis (MIPO)?
To return limb alignment and length to normal without disruption of fracture
What are some indications for circular fixator devices?
- Complicated fractures of the tibia and radius
- Distraction Osteogenesis
- Bone lengthening procedures
- Correction of angular limb deformities
__________ are small, parallel, staggered incisions made in skin adjacent to a wound to allow closure with reduced tension
Multiple punctate relaxing incisions
What is the most common organism associated with bite wounds in small animals?
Pasteurella multocida
Identify the fracture:
lateral humeral condylar fracture
What is the main difference between a dynamic compression plate (DCP) and a limited contact DCP (LC-DCP)?
LC-DCP has a contoured underside
- Allows stress to be more evenly distributed across plate (less stress at screw hole)*
- Less contact with bone = less disruption of periosteal vascularity, which reduces the porotic changes under the plate*
Which of the following materials is most likely to result in chronically draining non-healing wound?
- Glass shard from a Stag bottle on the strip
- Steel pellets found in a Stag bottle on the strip
- Grass awns found around a Stag bottle on the strip
- Lead bullet fragments
grass awns
Salter-Harris type ____ classification has been used to describe the partial physeal closures resulting from damage to a portion of the physis and causing asymmetric physeal closure
Salter-Harris type VI classification has been used to describe the partial physeal closures resulting from damage to a portion of the physis and causing asymmetric physeal closure
Because the screws are fixed within the hole of the plate, frictional forces between the plate and bone are unnecessary with what type of bone plate?
locking compression plate (LCP)
- Locking plates and screw systems provide fragment stability with the locking mechanism between the screw and the plate. In a locking plate, because the screws are fixed within the hole of the plate, frictional forces between the plate and bone are unnecessary.*
- The principal method of load transfer is directly through the plate and screw, and termed “screw-only” mode force transfer.*
- **little to no contouring is required with LCP***
What types of fractures are best repaired by interfragmentary wire?
Simple fractures of flat, non-weight bearing bones that interdigitate well
Most commonly used for certain mandibular and maxillary fractures
T/F: Bone plates should be applied to the tension side of bone
True!
What is the term used to describe a reversible change in shape in which material returns to its original shape when load is removed?
Elastic deformation
For what patient populations are acrylic frames best suited?
toy breed dogs, cats, and exotics
Salter-Harris type ____ fractures are crushing injuries of the physis that are not visible radiographically but that become evident several weeks later when physeal function ceases
Salter-Harris type V fractures are crushing injuries of the physis that are not visible radiographically but that become evident several weeks later when physeal function ceases
Name the forces that are overcome by interlocking nails:
all forces
biatch!
Plates that are used in addition to primarily placed lag or positional screws are in __________ mode
neutralization
Plate acts to protect/neutralize against shearing, bending, and rotational forces which would otherwise damage the interfragmentary repair achieved by the screws
T/F: When performing surgery on a clean wound, risk of infection generally doubles every 3 hours
False
When performing surgery on a clean wound, risk of infection generally doubles every hour
Identify the type of external skeletal fixator:
Type Ib
- unilateral-biplanar
- Pins 60-90 degrees from each other
- Interconnecting bars increases rigidity (more stable than IA)
- Only types IA and IB can be used on humerus and femur
What type of pinning is illustrated below?
Retrograde pinning
What bone tumor locations are amenable to treatment by limb sparing?
Distal radial lesions have best outcome
High complication rates though
Name the forces that are overcome by plating:
loading, bending, torsion
What type of screw is shown in the image below?
self-tapping screw
You can tell because of the fluted tip. This screw does not require tapping (pre-cutting the thread pattern into the bone following drilling)
What type of screw is best for use in dense, cortical bone?
cortical screws
- Best for use in dense, cortical bone
- Decreased outer diameter to core diameter
- More shallow thread
- Decreased pitch
When placing transfixation pins, you should place at least ___ pins in each bone segment
Two
When placing transfixation pins, you should place at least 2 pins in each bone segment. 3 pins per segment is ideal for optimal stabilization
An incomplete fracture in which a portion of the cortex is intact, thus stabilizing the bone to some extent, is termed:
Incomplete (Greenstick) fracture
What osteosarcoma treatment option is associated with the longest median survival time?
Amputation + chemotherapy
Together mean survival time is ~9-12 months
Dirty jokes aside, what is the main indication for “tubing the flap”?
“Tubing the flap” avoids making bridge incision but will require a second surgery to cut the flap free after it has healed in the wound bed – usually 14-21 days
What are some complications associated with external skeletal fixation?
- Pintract drainage: possible infection of soft tissues
- Loosening of pins/wires
- Pin bone interface sustains high stress loads, resulting in bone resoprtion
- Loose pins/wires must be removed
- Osteomyelitis
- Ring sequestrum
- Nerve or vascular damage
How would you classify an open fracture in which the wound is smaller than 1 cm, with mild to moderate soft tissue contusion?
Type I
Why are hybrid fixators particularly useful for treatment of fractures that are close to articular surfaces?
thin wires or a circular fixator allow for multiple sites of bone purchase in a smaller bone fragment
hybrid fixators utilize components of linear and circular ESFs
What tumor types are specific to the digits in the dog?
SCC and melanoma
inflammation within a joint is termed:
arthritis
What fixation technique would be ideal for treatment of an avulsion fracture?
Tension band
__________ is considered to be the single most important element for prevention/treatment of osteoarthritis
weight management
Open anatomic reduction is most appropriate for repair of what type of fractures:
transverse, oblique, segmental, and minimally comminuted fractures
**open anatomic reduction is required for articular fractures**
Name the primary implants that were discussed in lecture:
bone plates, interlocking nails, external skeletal fixators (ESFs)
Of the four A’s that are evaluated in post-op fracture repair radiographs, which term relates to the positioning of the joints?
Alignment
T/F: Axial pattern flaps are considered transpositional flaps
True
When placing cerclage wires, how should they be positioned in reference to the long axis of the bone?
Perpendicular
T/F: Fractures classified as Salter I and II have an articular component
False
A fracture line perpendicular to the long axis of the bone is a __________ fracture
transverse
A fracture line perpendicular to the long axis of the bone is a transverse fracture
Other than obvious implant migration, what is a radiographic change that would be indicative of implant loosening?
lucency around the pin
What is the term used to describe a permanent change in shape in which material DOES NOT return to its original shape when load is removed
Plastic deformation
spontaneous fusion of joint; end stage of joint disease is termed:
ankylosis
T/F: Osteochondrosis is a defect in endochondral ossification
True
This posture is characteristic for:
Infraspinatus Contracture
- Elbow adducted, antebrachium abducted
- Scapulohumeral joint can’t be internally rotated-scapula elevates when shoulder is rotated
- Limited range of motion
- Usually no pain on manipulation of joint
Muscle shortening not caused by active contraction is termed:
contracture
What is the most common direction of traumatic shoulder luxation?
medial
What form of coaptation should be applied for medial shoulder luxation?
Velpeau Sling
What form of coaptation should be applied for lateral, cranial, and caudal shoulder luxation?
Spica Splint
This procedure uses heat to shrink and tighten the shoulder capsule:
capsulorrhaphy
A dog presents with acute onset of pain on palpation of the shoulder. You note malpositioning of greater tubercle. What is your diagnosis?
traumatic shoulder luxation
