Veterinary Orthopedics
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| Characterize cortical bone | *limited blood supply
*strong dense bone
*good implant holding
*slow healing
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| Characterize cancellous bone | *excellent blood supply
*weaker porous bone
*good healing potential
*close to bone ends
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| Structural properties of a bone are dependent on what factors? | *size and shape
*load
*deformation
*stiffness
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| What does the slope of the linear portion of a Load-Displacement Curve represent? | stiffness of the bone
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| The point at which the linear portion of Load-Displacement curve levels off is called _____. What does it represent? | *it is called the yield
*it represents some structural change to the bone in response to load
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| What is the elastic region of the Load-Displacement curve? | *the region over which displacement of the bone will return to normal once the load is removed
*this is the portion of the curve before the yield
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| What is the plastic region of the Load-Displacement curve? | *the region over which displacement of the bone will not return to normal (there is structural change to the bone)
*this is the portion of the curve after the yield
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| Yield energy | The energy required to get to the yield point (where the bone's structure starts to get altered in response to load)
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| Failure energy | The energy required to get to the failure point (where the bone breaks)
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| Material properties of bone | Strain
Stress
Modulus of elasticity
Anisotropy
Viscoelasticity
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| Strain | *the change in length that is associated with tension (pulling) or compression forces (pushing)
*unitless entity
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| Stress | *force per area
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| What does Wolf's law state | *bone will adapt to loads
*if loading increases -> bone will remodel to resist loading
*if loading decreases -> bone will become weaker due to turnover
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| Anisotropy | *material (bone) response depends on force direction
*Structure of the bone determines its response to forces in different directions
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| Viscoelasticity | *response to load varies with rate of loading
*high speed vs. low speed impacts cause different types of fractures
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| Stress risers | *things that potentiate stress and decrease bone strength
*e.g. geometric irregularities
**holes, notches, edges of implants
*especially prominent under torsional loading
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| What does Wolf’s law state? | *Bone adapts to forces
**Increasing forces -> bone becomes bigger
**Decreasing forces -> bone becomes smaller
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| what parameters are tested in material properties | *Stress and strain
*Modulus of elasticity (slope)
*Anisotropy
*viscoelasticity
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| what parameters are tested in structural properties | *size and shape
*load
*deformation
*stiffness (slope)
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| How is the neutral axis defined during bending of a structure? | It is the plane at which there is zero force.
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| Where are tension and compression forces the largest during bending of a long bone (in relation to the neutral axis)? | The further away from the neutral axis, the greater the force (and the greater the bone's response, which is to remodel) --always put plate on tensile side--
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| Why is it important to appreciate the viscoelastic property of a bone? | Viscoelastic properties predict varying response of bone to hi and lo energy forces: faster loading (hi speed forces, a bullet) causes bone to store more energy, which when released, causes more damage to bone and surrounding soft tissue
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| What are the three factors that may influence the moment of inertia of a bone or implant? | *Shape of the implant
*Position of the implant
**further away from the Neutral axis = greater resistance to bending
*Bone remodeling
**Distribution of bone around the neutral axis
**X-sectional area of the bone
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| What are the 5 steps in fx management? | patient assessment, fx description, fx assessment, fx fixation method/plan, intra/post op fx assessment
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| Always take _______________ views of a fx. | orthogonal
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| What 3 general factors determine the fx assessment? | biological, mechanical and practical factors
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| Name some of the biological and mechanical factors involved in fx assessment. | biological- age, ST damage, closed v open, systemic dz, nutrition status
mechanical-communition, bone loss, intrinsic stability, weight, #limbs affected, controlled v excessive activity, early v delayed fx repair
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| What are the 4 As of your intra-and post-op fx assessment? | *alignment *apposition *apparatus *activity
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| What are the 4 fx healing phases | coagulation (hematoma), inflammatory, repair, remodeling
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| What are the 5 impt factors in bone healing? | animal age, location of fx, stability of fx, vascularity, interfragmentary distance
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| How do interfragmentary strains relate to bone formation? | Greater interfragmentary strain, the greater the risk of nonunion. Response varies between nonunion, granulation tissue formation, cartilage formation/endochondral ossification, and primary healing (<2%)
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| How is bone healing related to fx gap? | Fx gap size dictates whether it will heal via primary or secondary healing
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| What complication may occur if vascularity, stability, or distance are unfavorable? | nonunion, delayed union, infected non-union
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| What is the most common technique to stimulate bone healing? | cancellous bone grafts
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| Describe the rad assessment of a fx. | Obtain 2 views, assess quality and posn of rads, assess surrounding ST, perform stress rad if jt instability is suspected, describe the fx
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| what is the open fracture classification system? | A method to assess open fractures suggesting tx options and prognosis. Based SOLELY on the amt of surrounding ST damage.
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| What are 3 impt plat fxns? | *Compression (DCP- compress 2 fx ends together
*neutralization- spans fx to removes load on fx; transmits load thru plate instead (not a specfic type)
*buttress/bridging- both used to stabilize; buttress at end of long bones, bridging mid-diaphyseal
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| What are 5 impt implant property requirements? | *stiffness(stress shielding) *strength (repeated load resistance) *ductility (contouring the plate to the need for the fx) *corrosion resistance (think about material properties) *biocompatibility (avoid allergies, immune rxns, etc)
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| Why is post-op rad assessment impt? 6 reasons. | 1. fx mvmt
2. bone inactivity
3. bone resorption
4. bone infection
5. loss of allignment or opposition
6. implant loosening
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| Name 2 properties of a cancellous bone graft. | osteoconductive, osteoinductive
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| Which bacterial pathogen is often associated with iatrogenic infxn? | Staphylococcus aureus
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| What are the signs and symptoms of post-op infxn of fx repair? | Acute- pain, swelling, erythema, inc temp, no rad signs, look for disruption/draining
Chronic-draining, muscle atrophy, fibrosis, contracture, lameness, rad changes
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| What is a glycocalyx? | *a carbohydrate film that is laid by the bacteria around an implant with the purpose of protecting itself from antibiotics, antibodies and phagycytosis
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| What does the open fx classification desribe? | *just the extent of surrounding soft tissue damage (nothing to do with the type of fx) and what options are good for those circumstances
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| What forces contribute to a butterfly fragment? Where are the compression and tensile forces relative to bending environment. | ???
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| If you see a fracture that has a gap between the displaced bones, what type of healing will occur? What if you put in a plate? | If you can see the gap then there will be secondary bone healing. If you put a plate in there, you will get <2% interfragmentary strain (hopefully) and get primary bone healing.
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| what is the purpose of tendons? | to distribute power exerted by more proximally located muscles to the carpus/tarsus
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| How are tendons and ligaments commonly injured? | *direct trauma
*repetitive strain
*single "Bad step"
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| How are tendon and ligament injuries diagnosed? | US
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| What are some results of tendon and ligament injuries | *prolonged disability
*failure to restore normal morphology and fxn
*loss of use during convalescence
*reduced performance
*increased risk of reinjury
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| What are the benefits of US in Dx of ligament and tendon injuries | * sensitive and specific
* cost effective (no anesthesia)
* early detection of lesions
* early intervention
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| What are the tendons and ligaments of the equine metacarpus (cannon bone)from superficial to deep? | *superficial digital flexor tendon
*deep digital flexor tendon
*inferior check ligament
*suspensory ligament
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| Histological and chemical characteristics of tendons | *more mature
*type I collagen
*fewer cells
*less GAGs
*organized collagen x-linking
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| Histological and chemical characteristics of ligaments | *more immature
*Type III collagen
*more cells
*more GAG's
*less organized x-linking
*more rapid adaptation?
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| Summarize causes of OA | *primary OA (humans & cats)- wear & tear (chronic use, aging, obesity) and genetics
*secondary OA (dogs)- developmental/congenital (elbow, hip dysplaisa, OCD), mechanical (CCL rupture), traumatic (intraarticular fx)
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| Describe basic pathway in OA development | art cart is highly specialized, gets damaged (collagen&aggregans disrupted)water/matrix protein degraded->integrity of art cart lost->matrix breakdown initiates release of products into jt fluid->inflammation->more enzymes released->more degredation->etc
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| List primary sources of OA pain | OA pain is stiff & uncomfortable.
Synovium, jt capsule, subchondral bone all have nerve endings, so its the periarticular changes that cause pain.
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| Describe common clinical findings of OA | muscle atrophy, decreased ROM, pain on manipulation, jt effusion, +/-crepitation/grinding
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| Flexor tendon fxn | support during stance phase
flexion during swing phase
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| Extensor tendons | advance limb in prep of stance phase
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| Bursa | large bony protuberance
low motion of tendon over joint
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| tendon sheaths | high motion joint
small bony protuberance
retinacula and annular ligaments
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| Ligament fxn | provide link btw bones
support load
provide stability to joint
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| Pathophys of tendon/ligament injury in athletes | multifactorial
cyclical loading, repetitive weakening
excercise accelerates degenerative change
no CS
increased type III collagen and GAGs
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| pathophys of tendon/ligament injury in non-athletes | sudden overloading
degeneration (e.g. degenerative suspensory ligament desmitis)
CS: pain, heat, swelling, synovial
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| palpation of tendon/ligament injury | heat
swelling
pain/sensitivity
synovial structures palpable
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| definition of OA | Syndrome that affects synovial jt causing pain and dysfxn. Caused by degeneration of articular cartilage and changes in periarticular tissues.
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| Lameness exam with tendon/ligament injury | may be mild and transient, even with moderate injury
hard work --> swelling --> quickly abates
doesn't mean it's not injured
abnormal limb position, happens in more severe injuries
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| What is the diff visually of normal and damaged articular cartilage? | normal- white, smooth, continuous, shiny
damaged-rough, can see underlying structures, see proliferation of synovium (synovitis)
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| what are the basic parameters of tendon/ligament US | X-sectional area
Echogenicity
fiber pattern
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| what does an injured tendon/ligament look like on US | increased x-sectional area
decreased echogenicity
disruption of normal fiber pattern
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| CS of mild tendon/ligament injury | mild transient lameness
+/- heat and sensitivity
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| CS of moderate tendon/ligament injury | heat and swelling
increased lameness
peritendinous/periligamentous swelling
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| CS of severe tendon/ligament injury | severe swelling
heat
lameness
+/- abnormal limb position
joint instability
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| With OA, what is the one radiographic change you will see? | osteophytosis (bone spurs) but if see OA on rads, then means it is endstage OA
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| How does OA affect pt? | art cart is lost, then fxn of jt is lost->secondary periarticular changes which cause pain and dysfxn.
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| response to acute tendon/ligament injury | fiber disruption -> hemorrhage, edema and fibrolysis
inflammatory cells -> proteases & collagenases -> further fibrolysis
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| compartment syndrome | pressure from the hemorrhage, edema and fibrolysis of tendon injury --> pressure necrosis of fibers
worst case scenario of an acute injury
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| early healing of tendon/ligament (1-6mo) | granulation tissue replaces fibrin clot
fibroblasts produce more type III collagen
-weaker than type I
-fibers not well aligned with longitudinal axis
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| remodeling phase of tendon/ligament healing (>6mo) | type III collagen gradually replaced by type I
some Type III persists
fibers gradually realign along long axis
may take years
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| how long does repair and remodeling of tendon/ligaments take | 9-12mo if there are no setbacks or if it's not a severe injury
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| what do peritendon/ligament calcifications signify | chronic strain injury
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| traumatic injuries involving synovial structures | req aggressive med and or sx tx
guarded prognosis
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| what are some differentials for tendon/ligament injury | peritendinous/periligamentous inflammation w/o tendon/ligament injury
secondary joint dz +/- fibrosis of joint capsule
tumoral calcinosis
calcinosis circumscripta
neoplasia
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| goals of treating tendon and ligament injuries | decrease inflammation in acute phase
maintain tendon length and strength
decrease adhesion formation
return to previous level of performance without reinjury
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| how do you decrease inflammation in tendon/ligament injury | hydrotherapy
standing bandages
NSAIDS (1-2wks)
Corticosteroids (limit to 1-2 doses)
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| Tendon splitting | decompression of acute core lesion
reduces pressure necrosis
use only if US evidence of anechoic lesion
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| Superior check ligament desmotomy | transection of the SCL to elongate the superficial digital flexor tendon
makes it less susceptible to reinjury
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| Annular ligament desmotomy | (annular ligament may compress the tendon)
to tx severe tendinitis in the distal metacarpal region
increases patient comfort
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| How does OA cause poor fxn? | *painful, lose fxn
*stiff due to fibrosis, osteophytosis, lose smooth mvmt
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| How can you prevent OA? | *stop breeding dogs with dysplasia, OCD, CCL ruptures
*dx and tx early
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| What is current OA tx? | 1. set goal with owner for what is expected fxn
2. do conservative measures
3. if conservative measures don't work OR OA has progressed too far already, do salvage sx procedures
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| How do you dx OA? | 1. PE, Hx, Sig, CS, rads
2. r/o more severe dz like neoplasia, septic arthritis, immune-mediated arthropathy (these are scary, don't miss them)
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| OA CS | Stiffness, difficulty getting up, reluctance to exercise, +/- lameness, may present as behavioral changes
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| Sx repair of severed or ruptured tendons/ligaments | debride devitalized portions
suture with enough bite to hold, but not to strangle the vascular supply
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| What does acoustic shock wave therapy do? | pressure waves generated outside the body are focused at a specific site and release kinetic energy
increase cell permeability
stimulate cell division
stimulate cytokine production
neovascularization at tendon-bone jxn
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| should you completely immobilize a patient recovering from a tendon/ligament injury? | no, it will result in loss of tendon strenght
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| rehab of SA patients with tendon/ligament injuries vs LA patients | SA - passive range of motion exercises
LA - controlled exercise program and stall rest
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| what are the benefits of controlled exercise programs for tendon/ligament rehab? | stimulates maturation of granulation tissue
encourages longitudinal alignment of fibers
decreases adhesion formation (which increase risk of reinjury)
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| what affects the prognosis of a tendon/ligament injury | severity of initial injury and structure affected
adherence to controlled exercise program
desired use of the animal
attitude and behavior of P and O
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| What is osteochondrosis? | A condition of cartilage and bone; a failure of endochondral ossification (remember this is when cartilage is laid first then replaced with bone)
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| What is OCD? | Thickened cartilage where have the cartilage flap
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| Where does osteochondrosis occur? |
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| how do we dx osteochondrosis? |
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| how do we tx osteochondrosis? |
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| how do we prevent it without developing other problems in the breed? |
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| What is the process of osteochondrosis to the point of a jt mouse? | failure of endochondral ossification (bone not replacing cartilage)-> cartilage thickens->get cartilage folds->get cartilage flaps (OCD)->flap free in jt is a jt mouse
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| what things contribute an animal to having developed the dz? | multifactorial- nutrition, genetics(dogs and horses), biomechanical (some interactions playing a role in disrupting blood supply), growth rate (rapidly growing animals), gender (males are more prone to developing osteochondrosis)
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| where does osteochondrosis occur in a pig? | most common- end of femur, humerous
also in shoulder, hip, hock
"weak leg syndrome"
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| where does osteochondrosis occur in a dog? | -male, large breeds
-most common site: shoulder, cranial aspect of humeral head; elbow, stifle, hock
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| where does osteochondrosis occur in a horse? | most serious- shoulder
hock, stifle, fetlocks
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| what things contribute an animal to having developed the dz? | multifactorial- nutrition, genetics(dogs and horses), biomechanical (some interactions playing a role in disrupting blood supply), growth rate (rapidly growing animals), gender (males are more prone to developing osteochondrosis)
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| where does osteochondrosis occur in a pig? | most common- end of femur, humerous
also in shoulder, hip, hock
"weak leg syndrome"
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| where does osteochondrosis occur in a dog? | -male, large breeds
-most common site: shoulder, cranial aspect of humeral head; elbow, stifle, hock
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| where does osteochondrosis occur in a horse? | most serious- shoulder
hock, stifle, fetlocks
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| What would you use to detect if there is synovitis? | Joint tap- should have nice stringy characteristic; if inflammation, will be watered down.
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| if suspect osteochondrosis, what is the first thing you want to do diagnostically? | radiographs, and always do both side bc often osteochondrosis is bilateral
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| what is the classic site for osteochondrosis in a dog shoulder? | caudal humeral head see a loss of articular cartilage
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| most common site in horse for osteochondrosis? | lateral trochlear ridge of distal femur
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| How do you image art cart? | Rads, double contrast study (to ID flap location, MRI (but hard to do, U/S (esp stifle OCD), arthroscopy (look directly)
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| When, if signs of osteochondrosis, do you radiograph all limbs? | when the fetlock (metacarpal, metatarsal) jts are invovled
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| How do you tx osteochondrosis? | 1. prevent it from happening?
2. if clinical, do sx: arthrotomy (open approach to jt), arthroscopy (smaller incision and visualize with camera),
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| What do you do if you dx osteochondrosis in a young foal/puppy? | If you are seeing early lesions, let them go on to grow. They usually heal as they grow.
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| Prevention for osteochondrosis. | 1. don't breed affected animals, but be careful in horses bc performance and osteochondrosis is related
2. nutrition
3. prevent xs traumatic or heavy exercise in young animals
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| Sx repair of severed or ruptured tendons/ligaments | debride devitalized portions
suture with enough bite to hold, but not to strangle the vascular supply
🗑
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| What does acoustic shock wave therapy do? | pressure waves generated outside the body are focused at a specific site and release kinetic energy
increase cell permeability
stimulate cell division
stimulate cytokine production
neovascularization at tendon-bone jxn
🗑
|
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| should you completely immobilize a patient recovering from a tendon/ligament injury? | no, it will result in loss of tendon strenght
🗑
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| rehab of SA patients with tendon/ligament injuries vs LA patients | SA - passive range of motion exercises
LA - controlled exercise program and stall rest
🗑
|
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| what are the benefits of controlled exercise programs for tendon/ligament rehab? | stimulates maturation of granulation tissue
encourages longitudinal alignment of fibers
decreases adhesion formation (which increase risk of reinjury)
🗑
|
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| what affects the prognosis of a tendon/ligament injury | severity of initial injury and structure affected
adherence to controlled exercise program
desired use of the animal
attitude and behavior of P and O
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