Dogs and Cat 6 Flashcards
Fracture reduction direct and indirect ways
- Direct:
○ Traction/leverage on major bone fragments
○ Requires an open approach - Indirect:
○ Traction remote from fracture site often via ligaments and tendons (ligamentotaxis)
○ Can be performed closed or via minimally invasive techniques
○ Pins and Fracture distractor
Internal fixation goal and advantages and disadvantages
- Want to hold the alignment in place to allow animal to weight bear after surgery
ADVANTAGES - May allow complete reconstruction of the bony column and load sharing
- If applied correctly results in rigid stability allowing rapid weight bearing and minimizing fracture disease
- Typically very comfortable for the patient and minimal aftercare
DISADVANTAGES - Invasive: requires a surgical approach for application plus implants potentiate infection
Areamoment of inertia for internal fixation what is it, formular and therefore what dimentions have greater
- Property of a material (e.g. Stainless steel) to resist bending forces = Area Moment of inertia
- AMI of a rod ∝ Radius4
○ Small increase in radius -> large increase in AMI
§ Want to get large pin - greater resistance to bending forces
○ So 4mm pin AIM = 16, 6mm pin AIM = 81 - AMI of a plate ∝ Height3
○ Thicker plate resistance to bending
Intramedullary pins where placed what resist and don’t resist, benefits and how to choose pin size and what can use with
- Placed in the central axis (medullary canal) of bones
- Mighty resistors of bending
- Inexpensive and low inventory requirement
- Will not prevent axial compression, rotation, shear
- When placed alone (uncommon) select pin approximating 70% of IM canal diameter
- When used with a plate an IM pin of 50 % of medullary canal diameter will extend plate fatigue life 10 fold
○ IM supplies bending, plate provides contraction of compression and rotation
Intramedullary pins how to introduce into bone
○ Placed via a Jacobs chuck or a drill
○ Can be placed:
§ Normogradeor Retrograde (from the fracture site)
§ IM pins can be placed retrograde or normogradein the humerus, ulna and femur
§ IM pins can be ONLY be placed normogradein the tibia
§ IM pins cannot be placed in the radius
Kirschner wires and cerclage wiring what used for
INTERNAL FIXATION
Kirschner
- Primary stabilization for very stable fractures in young/small patients
- Achieving temporary stabilization
- As an adjunctive implant
- 2 points fixation required to prevent rotation
Cerclage
- Wire encircling the entire bony diameter to create compression
- Only suitable for long oblique fractures or spiral fractures.
- Only works with perfect anatomical reconstruction
- Need a minimum of 2 and ideally more
Orthopaedic wire how acquire strength, knots and application
- Strength is related to cross sectional area - need to twist around each other
- Knots:
1) Single loop cerclage
2) double looped cerclage
Applications
○ Tension band wiring: - most common
Screws what are the 2 main types, differences and which most common
1) Cortical bone screws: - most common § Designed for dense cortical bone. § Increased pitch (No. Threads/length) § Less thread depth § Greater core diameter 2) Cancellous bone screws (metaphysis only) § Designed for cancellous bone Decreased pitch § Increased thread depth
what are the 3 ways screws are placed and what does this result in
1) As positional screws:
§ Only results in fixation of the two fragments without compression
2) As a lag screw: - generally cortical screw
○ Creates compression across a fracture which markedly increases stability -> Achieves this by
□ Glide hole (first hole) - is drilled into cortex of one of the fracture pieces and has a larger diameter to the screw - so screw does not engage in this cortex
□ Second ‘pilot’ hole then drilled from the glide hole into the second fracture piece HOWEVER the diameter is equal to that of the screw so the screw engages with this cortex resulting in compressive force
Compression from screw in bottom piece and top of screw head in the top forces the fracture sites together
3) through plate
What are lag screws suitable for and rules for placement
○ Suitable for oblique fractures.
○ Ideally screw should be placed perpendicular to fracture
○ Need 5 cortices at each end of the fracture site -> can have two cortices if go through both surfaces
Bone plates advantages and disadvantages
ADV
1. neutralises all fracture forces
2) can be applied minimally invasively
3) Can achieve maximal stability of fracture gap with dynamic compression plating,
4) Very rapid return to function with minimal post op pain and care
DIS
1) traditional rewuires extensive dissection
2) plate perioheral to mechanical axis
3) accurate contouring of the plate to the bone surface
Conventional plating what does stability require, minimum of how many cortices and clinical results
- Stability for this type of plate relies on friction between the plate, bone and screw
- Minimum of five cortices above and below the fracture
○ Generally 2.5 screws - Very good clinical results.
What are the 5 main ways to apply plate to bone and what size bone plate do you choose
1) dynamic compression plate
2) Neutralisation plate
3) bridging plate - span communicable fracture site
4) buttress plate - just hold fragments in place
5) locking plate - cotouring plate not required, better stability and rigid, more biological approach
SIZE - <30% bone diameter
Dynamic compression plate what does it have and therefore the 2 types of screws
○ Have an oval hole so two ways can use screws within
§ Compression -> Fracture anatomically reconstructable - results in compression at fraction site - eg: Transverse fracture
□ Use cortical screws with dynamic plate and drill eccentrically (off to one side of the plate hole), screw wants to be in the middle so will move slightly bringing the fracture site together
§ Neutral -> screw straight down the middle of the oval hole so no compression
Interlocking nails what is it, good at resisting and applicable to fractures of
- Like an IM pin with holes
- Good at resisting bending
- Screws/bolts prevent axial compression or rotation
- Can be placed minimally invasively with the aid of fluoroscopy
- Applicable to fractures of:
○ Femur
○ Humerus
○ Tibia
external skeletal fixation what good for and goal
good for Gardiner approach of fracture repair
- Frame: Supportive exoskeleton for the healing fracture.
Linear external skeletal fixation what are the types of pins
- Smooth: now largely superseded
- Positive profile:
§ Threads rolled on, thread diameter > core diameter
§ Better engagement - Negative profile:
§ Threads cut in, thread diameter = core diameter
§ Stress riser - End threaded half pins: - half pin
§ Only go through soft tissue on one side of bone - Centred threaded full pins: - full pins
§ Go through soft tissue on both sides of bone
Linear external skeletal fixation principles what forces resist, dependenat on and the 3 types
- Can resist all fracture forces: - like plates
○ Bending
○ Axial (Compression/distraction)
○ Rotational
○ Shear - Dependant on configuration:
○ Bending most effective in the same plane as the fixator frame. - Different types
○ Type 1 -> unilateral, uniplanar
○ Type 2 -> unilateral, biplanar -> two connecting bars at right angles to each other
○ Type 3 -> strongest, type 1 and 2 -> three connecting bars, two at 180 degrees and 1 at 90 degrees
Linear external skeletal fixation advantages and disadvantages
ADV
- versatile and adaptable
- well tolerated, particularly on distal limbs
– Implants are removed (easily) once fracture has healed –useful in contaminated/open fractures
- Frame can be adjusted post surgery to improve alignment or enhance fracture healing
- Implants are cheap vs plating
- Biologically friendly to extraosseoussoft tissue and blood supply for fracture healing
DIS
– Increased morbidity/decreased limb use compared with internal fixation
Draining Pin tracts:
○ Consequence of percutaneous elements transfixing skin and other soft tissues
- Increased patient care required by owner and clinician compared to internal fixation
Linear external skeletal fixation how to apply and how to increase frame strength/stiffness
- Frame needs to be strong/stiff enough to withstand forces applied during normal activity
- Frames should be applied with strict aseptic technique.
Can increase frame strength/stiffness by:
○ More pins: Minimum of two, ideally 3 per fragment, beyond 4, advantage is negligible
○ Bigger pins:
○ Decreasing pin working length (distance between clamp and bone) by getting clamp close to bone :
○ Span the fragment with pins (far, near, near, far principle).
○ Use threaded pins rather than smooth
Linear external skeletal fixation aftercare
- Entire limb should be bandaged to reduce swelling.
- Sponges packed under the frame.
- Frame wrapped to reduce the risk of fixator snares
- ESF specific complications-
- Pin track discharge:
○ Especially an issue in areas with more soft tissue
○ May reflect instability
○ Often leads to infection, some cases require oral antibiotics
○ Cleaning the skin with chlorhexidinesurgical scrub
Open fractures what fixation device need to use and why and inital emergency treatment
○ Use external not internal fixation - IMPORTANT § Internal plate will be able to create a biofilm to harbour infection - leads to bone infection Initial emergency treatment: ○ Lavage and debridement ○ C&S ○ Commence intravenous antibiotics ○ Sterile dressing ○ Apply external coaptation
What are the 4 properties of a successful bone graft
- Osteogenesis
§ Surviving graft osteoblasts produce new bone - Osteoinduction
§ Chemical signalling from growth factors induce differentiation of pleuripotent mesenchymal cells into osteoblastic/chondroblastic lineage - Osteoconduction
§ Microstructural support for deposition of bone - Osteopromotion
§ Structural support
Autogenous cancellous bone graft and cortical grafts when used and which is better as provides which properties
Autogenous cancellous bone graft:
- Proximal humerus, ilialwing or proximal tibia.
- Remains the gold standard treatment
- Transferred as quickly as possible
- all 4 properties
Cortical grafts:
- Mainly used where a large bony defect exists
- Osteoinductive and osteoconductive & provide structural support
Postoperative management for fracture repair
- Lead walking only and cage rest
- Abdominal sling
- Owners are frequently poorly compliant
- Weightbearing on the operated limb is desired and encouraged.
- Adequate analgesia
- Ice packing
- Typically patients are discharged with an NSAID +/-Tramadol
What are the 4 factors to assess post-operatively after fracture repair
1. Alignment ○ both angulation and rotation. ○ Joint to joint alignment ○ Fracture alignment 2. Apposition: ○ Size of fracture gap 3. Apparatus ○ Is there sufficient purchase? ○ Does an IM pin engage the metaphysealtrabeculae? ○ do implants impinge on joints? ○ could implants impinge on adjacent ST? ○ Any problems with surgical stabilisation can then be immediately addressed- • 4. Activity ○ Bone healing ○ 6-8 weeks later take radiograph to determine
What are the 3 types of arthritis
- Osteoarthritis
- Infective arthritis
- Immune mediate arthritis
Osteoarthritis causes and 4 factors that may influence
- Primary: ○ no inciting cause ○ more common in cats than dogs - Secondary: ○ Underlying cause: § Articular fracture § Developmental/degenerative conditions § Changes that alter the way load is transmitted through the joint: □ Ligamentous injuries □ Angular limb deformities Factors that may influence 1. Age 2. Obesity 3. Neutering 4. Life style
Osteoarthritis pathogenesis 3 steps and history and clinical signs
Pathogenesis 1. Synovitis 2. Subchondral bone 3. Pain History and clinical signs 1. Lameness/stiffness 2. Signs exacerbated by vigorous activity 3. Reduced activity/exercise intolerance 4. Signs improved with NSAIDS 5. Reluctance to jump, climb stairs 6. Licking at affected joints 7. Aggression/irritability
Osteoarthritis diagnosis
- Radiographs
- Synovial fluid analysis:
○ Assess volume, colour, turbidity & viscosity
○ Mild increase in cell count (2-5 x 109/l <2 for normal),
○ Predominantly mononuclear cells
Osteoarthritis conservative management list the 6 main things involved
1) weight loss
2) excercise modulation - levels constant, swimming or hydrotherapy ideal
3) NSAIDS
4) other drugs - paracetamol, tramadol, codeine and oral opiods, corticosteroids
5) nutraceuticals - disease modifing osteoarthritis drugs, glucosamine, essential fatty acids
6) regnerative medicine - stems cells
NSAID use in osteoarthritis what does it do and side effects
○ Block the cyclooxygenase pathway § Leads to formation of thromboxanes and prostaglandins § COX 1 - constitutive form § COX 2 - inducible form ○ Side effects § Gastroduodenal damage/ulceration § Reduced renal blood flow § Reduced platelet function
Other drugs used in treatment of osteoarthritis
○ Paracetamol:
§ Centrally acting
§ Improved GI and renal safety profile c/w NSAID’s
§ For Dogs ONLY, HIGHLY TOXIC/FATAL IN CATS
○ Tramadol:
§ Synthetic opioid
○ Codeine and oral opioids:
○ Amantadine:
§ MMDA (3-methoxy-4,5-methylenedioxyamphetamine) antagonist
○ Corticosteroids:
§ Intra-articular preparations
§ deleterious effects on cartilage matrix synthesis
Nutraceuticals what are hte main ones used in osteoarthritis and evidence supporting their use
1) Disease modifying ostoeoarthritis drugs (DMOADs): § Pentosan Polysulfate: □ In vitro positive effect on cartilage □ Fibrinolytic and thrombolytic effects, □ Some evidence to support efficacy in dogs 2) Nutraceuticals: § Glucosamine and chondroitin: □ No evidence to support efficacy □ Expensive □ Safe 3) Essential fatty acids: § Eicosapentaenoic acid (EPA) § significant effect based on force plate analysis.
Regenerative medicine use in osteoarthritis and evidence
○ Stem cells:
§ Harvested from autologous adipose tissue then expanded and injected intraarticularly
§ allogenic
§ Mechanism unknown
§ No evidence (so far)
§ Some anti-inflammatory effects for a short period
Salvage surgery for osteoarthritis when used and the 4 options
- If refractory to medical management
1. Excisional arthroplasty
2. Arthrodesis
3. Total joint replacement
4. Amputation – rule out other limb pathology before cut
Infectious/septic arthritis what are the 3 types, causes and common organisms in dogs vs cats
Classification - Type 1 (acute) - Type 2 (chronic) Causes - Iatrogenic (Surgery/arthrocentesis): - Penetrating wound - Bite wounds - Hematogenous Typical organisms - Dogs: ○ Staphylococcus, betahemolytic streptococcus - Cats: ○ Pasteurella and Bacteriodes
Infectious/septic arthritis pathogenesis and clinical signs
Pathogenesis - Rapid infiltration of the synovium and joint fluid with suppurative inflammatory cells - Release of inflammatory cytokines and proteolytic enzymes - Rapid degradation of collagen and glycosaminoglycan - Changes are rapid and irreversible - Fibrin deposition Clinical signs - Acute onset severe lameness (type 1) - Marked swelling/effusion - Warmth and pyrexia - Lymphadenopathy - Systemic signs
Infectious/septic arthritis diagnosis what are the 2 main techniques used and what looking for on each
1. Arthrocentesis ○ High cell count: >50 x 109/l ○ Predominantly neutrophils (80-90%) with toxic change ○ Intracellular bacteria ○ Culture: Negative in 80-90% ○ Synovial fluid should be inoculated into blood culture medium ○ Synovial biopsy: equivalent positive culture rates 2. Radiography ○ Joint swelling ○ Gas ○ Bone lysis, periosteal reaction ○ Radiographic changes take 2 weeks
Infectious/septic arthritis what are the 2 main treatment options and prognosis
- Broad spectrum antibiotics: ○ Intravenous initially ○ Only AFTER synovial fluid sample taken ○ Minimum of 28 days ○ Cessation based on synovial fluid analysis ○ If no improvement within 24-48 hours consider surgery - Surgery - joint irrigation surgery ○ Indicated if: § Gross contamination § Poor response to initial antibiotic therapy § Implant retrieval required - Prognosis: ○ Guarded ○ OA long term
