Dog and Cat 7 Flashcards
Hereditability index for elbow dysplasia and how related to screening programs
- Heritability index appears to be quite low
- Heritability indices are not available for each of the four manifestations of the condition
- Fragmentation of the coronoid process (FCP)
- HI 0.06 - 0.24 - VERY LOW - will this screening program work???
What is involved with the radiographic screening for elbow dysplasia
- > 12 months of age
- Single FLEXED MEDIOLATERAL PROJECTION of both elbows
- Radiographs must contain permanent patient ID and L/R marker, date when taken, and clinic where taken
Elbow Score allocated according to severity of secondary OA - Score allocated based on detecting secondary osteoarthritis
○ osteophyte formation on proximal margin of AP
○ sclerosis at base of MCP
○ Sclerosis of ulna trochlea
○ osteophyte formation on radial head, humeral condyle, medial humeral epicondyle - Grade 0, 1, 2, or 3
Hip dysplasia what is it, cause, breed and heritability
= OA caused by joint laxity
- Inherited condition
- High prevalence among GSD, Golden Retriever, Labrador Retriever, Newfoundland
- Virtually unrecognised in breeds such as Greyhound and Borozoi
- Polygenic trait, with phenotypic expression strongly influenced by environmental factors
- restricted feeding resulted in lower prevalence of OA and later onset of clinical signs
- Heritability estimates for Hip Dysplasia range from 0.2 to 0.6
what does the radiographic screening of HD and list the 2 main screening programs
- on detecting joint laxity &/or secondary OA
- Accurate patient positioning is crucial for repeatability of assessments - GA or heavy sedation required
- Radiographs must contain:
○ permanent patient ID
○ L/R marker
○ date when taken
○ clinic where taken
Screening programs
1) ANKC CHEDS
2) PennHIP scheme
ANKC CHEDS what is it, what age, how to ensure positioned correctly and how to score what score used for
One of the 2 screening programs for hip dysplasia
- Relies on the ‘hip extended’ projection
- Dog must be >12 months of age
- Features to check for good positioning:
○ include pelvis and stifle joints
○ obturator foramen similar size
○ femurs parallel to each other
○ femurs parallel to table
○ patellas superimposed over the femoral trochlea
- Score = sum of scores attributed to nine key indicators of joint laxity and osteoarthritis
○ Joint laxity : Norberg angle, subluxation, rounding of acetabular margin
○ OA : osteophytes, enthesophytes (‘Morgan’s Line’), sclerosis, shallow acetabulum, modelling of femoral head & neck, flattening of dorsocranial acetabular margin
- Each hip scored out of 53, total of 106 per dog
- Score of a dog is compared to the breed average - worse than average -> probably don’t breed from
PennHIP scheme what is it, what does it rely on, positioning, taken by who, how old and other important factors
- Relies on the ‘distraction’ view
- hip distraction
○ Extending the hips causes spiral tensioning of joint capsule - masks laxity
○ Distraction techniques reveal maximal laxity of the hip joint - Relies on distraction of the coxofemoral joints, where a fulcrum force is applied to the hip joints to reveal the maximal passive joint laxity. This is achieved by placing the dog in dorsal recumbency, holding the hips in a neutral ‘stance’ angle, placing a radiolucent fulcrum
- Only taken by trained & accredited vets
- Dog must be > 16 weeks
- MANDATORY submission of films
- DI > 0.3 -> increased risk of developing OA later in life
List 11 ways to compare CHD screening schemes
- ANKC CHEDS well established, widely used, and well supported by breed clubs
- Hip extended view easy to take
- Any vet can take ANKC CHEDS radiographs
- ANKC CHEDS has perceived slow progress in eliminating CHD
- Little concrete research/science behind the ANKC CHEDS
- PennHIP DI has higher heritability estimate than Norberg Angle or signs of OA (Leighton et al. 1998)
○ HI for NA : 0.43 - 0.46
○ HI for radiographic OA : 0.03 - 0.37
○ HI for DI : 0.46 - 0.92 - DI appears to be a more repeatable scoring method than the schemes based on hip extended view
○ more repeatable between evaluators
○ more repeatable within the one animal, over time - PennHIP can be performed from 16 weeks of age, ANKC CHEDS must be 12 months of age
- Mandatory submission for PennHIP scheme, voluntary submission for ANKC CHEDS
- PennHIP views are more technically challenging to perform, more personnel, close to primary x-ray beam
- Must be trained for PennHIP, accredited, and have purchased the patented ‘distractor’ device
Ultrasound for musculoskeletal imaging, what type of frequency used for different structures and what can you visualise and the 4 main things it is used for
- High frequency linear transducer >7.5MHz for superficial structures
- Low frequency curvillnear <5MHz for deep structures
- Can visualise the following
○ Bone surface
○ Synovium
○ Joints space
○ Menisci
○ Muscles
○ Dynamic assessment
○ Guided aspirates/biopsy
Used for with equine
1. Tendon and ligament injuries
2. Pelvis - hard to visualise in radiograph
3. Stifle joint
4. Septic joint
Tendon injury with ultrasound what is normal and what occurs with injury
Normal tendon - Discrete fibre packets ○ Linear striations in longitudinal ○ Dots in transverse Injuried • Altered size and shape • Reduced echogenicity (hypoechoic) - fluid in tendon shealth • Altered fibre alignment
Large tendon injuries seen with ultrasound prognosis and why, how to know if large
- Large lesions = poor prognosis ○ Haematoma leads to: -> Granulation tissue -> Fine fibre bundles -> Irregular linear striations - Need to measure lesion -> measure the tendon and the lesion -> what percentage of tendon is the lesion
Small animals how is ultrasound used for musculoskeletal injury
- Not used as commonly as in equine patients
- Soft tissue structures in shoulder
- Common calcaneal tendon injury (Achilles tendon)
Joints - Normal synovial fluid: anechoic
- Synovial tissue: hyperechoic
- Articular cartilage: hypoechoic
- Bone surface hyperechoic with profound distal shadow
- Can target the joint via ultrasound to get out fluid and to put in medications
Meniscal injury
Ultrasound muscle what is normal and injury and disease
- Hypoechoic with internal hyperechoic striations
- Injury
○ Enlarged, disrupted fibres -> oedematous
○ +/- pockets of fluid - Fibrosis
○ Reduced size
○ Increased echogenicity
What is another important function of ultrasound and the 5 limitations
Foreign body identification - Especially grass seeds -> can dug up into soft tissue - Direct clinician to where it is Limitations of ultrasound 1. High quality machine required 2. Operator dependent 3. Limited information on bone lesion 4. Other modalities have increased sensitivity 5. Can't access some areas -> lungs
Sctintigraphy what is it mainly used for and what excellent and poor with, list the 4 main limitations
Mainly used for: - Equine lameness investigation - Some small animal applications - Excellent sensitivity for bone lesions - Spatial resolution poor Limitations 1. Referral institutions 2. Radiation licensing requirements 3. Low spatial/anatomic resolution 4. Poor specificity
Sctintigrahy what are the 3 phases in image acquisition and what can you assess in each stage
- Vascular phase
- Acquired immediately - as injected IV
- Assess blood flow
- Can be used in limbs where tourniquet -> is there blood flow to the distal limbs? - Soft tissue phase
- 5-10mins after injection
- Increase uptake may be due to trauma, infection, rhabdomyolysis
- Sensitive but NOT SPECIFIC - Bone Phase
- 2 hours pot injection
- Increase uptake in areas of increase bone turnover
- Screening for skeletal metastases
Computed tomography advantages and limitation especially with Equine CT
- Superior detail of bone and soft tissue
- More sensitive for bone loss
- Eliminates superimposition
- Improved lesion characterisation with reconstruction in different planes and 3D reformats
Limitations of Equine CT - Cannot get whole body within -> head and distal limb
- Need special table to hold the weight of the horse
What are the 6 main reasons to use CT for musculoskeletal injuries
- Elbow dysplasia complex
- Equine condylar fracture
- Foal osteomyelitis
- Pelvic fracture - BEST FOR THIS
- Foreign body - may have multiple draining tracts within the soft tissue
- CT guided biopsy especially in vertebrae and skull
MRI what is it goof for and limitations
- BEST soft tissue detail
- Good for detecting bone lesions
- Commonly used in humans
- Increased popularity for assessment of equine foot
- Underutilised in small animals
Limitations of MRI- Very expensive
- Limited availability
- Long scan times
- Usually required GA
What are the 3 main uses of MRI
- Canine shoulder - damage to the soft tissue around the bones
- Hip luxation - soft tissue surrounding the hip resulting in unstable hip joint -> luxation in and out
- Muscle injury -> muscle change
Osteochondrosis define, pathogenesis and main cause
- A focal defect in endochondral ossification in articular-epiphyseal growth cartilage
Pathogenesis
§ At least one secondary ossification centre generally at proximal end
□ Has junction with articular cartilage -> WHERE ISSUE IS IN THIS CASE
® Bone is meant to take over the articular-epiphyseal growth cartilage leaving only the permanent articular cartilage left - DOESN’T OCCUR
Cause - Anatomic factors - failure of blood supply locally
In terms of osteochondrosis what happens for the failure of blood supply
- Blood supply -> most cartilage is avascular
○ Permanent articular cartilage = avascular
○ Articular epiphyseal growth cartilage = vascular
§ THEREFORE -> vascular disruption leading to cartilage necrosis can occur in this region
□ Necrotic -> no hyperkeratotic chondrocytes -> not sending signals and preparing the region to endochondral ossification - Necrotic/retained cartilage results
○ Can resolve itself - no clinical manifestations
○ Other situations result in fissures from the articular surface -> leading to osteochondrosis dissecans -> joint mice
How would you best localise the problem within the limb and once localised what do you do next, if suspect OCD what best to diagnose
○ Orthopaedic examination -> BEST FOR LOCALISATION
- Radiography - need to always radiogrpah contralateral limb
Arthroscopy (DIAGNOSE AND TREAT THE JOINT)
What is the best radiographic view for lesion affected lateral trochlear ridge, whick joints tolerate OA best and when would you do a total elbow replacement
□ Flexed craniocaudal or dorsolateral plantar medial views -> uncommon
- More proximally joints tolerate OA best
- Total elbow replacement - NOT POINT UNLESS BOTH LATERAL AND MEDIAL CONDYLE AFFECTED
What are the 7 main complications of fracture repair
1) delayed union
2) malunion
3) non-union - viable and nonviable
4) osteomyelitis
5) open fracture and infection
6) implant fracture
7) refracture after implant removal
Delayed union define, and how is it defined and treatment
- Fracture where healing is progressing more slowly than expected
○ Define
§ young - 10 weeks should heal - if not delayed union
§ Older cat - 10 weeks not healed, normal - Intervention may be required to prevent nonunion or wait and see
Treatment: - Monitoring healing by sequential radiographs
- Revision of the stabilization - Rigid fixation
- Adding agents to improve healing ability:
- Cancellous bone graft, DBM, BMPs -> Osteoinduction
○ Add agents to improve healing ability
Malunion define, 4 main types and what may result in
- Healing of the bone due to initial malposition or malalignment during the fracture repair or early implant failure and eventual union
- Four types:
1. Frontal – varus/vargus
2. Axial - rotational -> when bandaging and the limb rotations
3. Sagittal – pro-/recurvatum -> opposite way to what is normal or what you want
4. Shortening - 10% difference in length between right and left limb well tolerated - Varus/vargus, rotational deformity and curvatum may produce secondary change
Malunion what are the consequences in mandibular/maxillary, pelvic and long bone fractures and treatment
- Mandibular/maxillary fractures - malocclusion of the mouth
- Pelvic fractures - constipation, dystocia
- Long bones – malalignment, OA, tendon/ligament damage due to abnormal weight
Treatment - CORA
- Stabilisation
○ Plates/screws
○ ESF - Open or Closed wedge
- CT and 3D printing
Non-union define and the 2 types with types within
- Fracture where healing has ceased and fracture healing is not possible without some form of intervention
○ Just filling in the gap with fibrous tissue
Viable non-union
1. Hypertrophic non-union - considerable callus present
2. Moderately hypertrophic non-union - moderate callus visible
3. Oligotrophic non-union - no callus but still viable cells present
Nonviable non-union
1. Dystrophic non-union - radiographic appearance similar to oligotrophic non-union but no blood supply so no viable cells
2. Necrotic non-union - presence of a sequestrum surrounded by involucrum (reactive new bone
3. Defect non-union - fracture gap is too large
4. Atrophic non-union - resorption of the fracture ends leading to rounding of bone ends and osteoporosis
List the 5 main causes of non-union
1) instability
2) stress protection
3) too much gap
4) poor blood supply
5) infection
Describe how instability and stress protection leads to non-union and what type of non-union do they lead to
Instability – hypertrophic nonunion
○ Caused by fracture repair that does not provide adequate stability
○ Too much stress and strain leads to formation of fibrous tissue
2. Stress protection – atophic non-union
○ Some strain is necessary to stimulate stem cells to differentiate so if the fracture repair is too rigid this doesn’t occur
nterfragmentary strain <1%
- Typically an antebrachium of toy breed dogs due to large implants relative to its small skinny radius
○ Too rigid stabilisation cause osteopenia of bone underneath and atrophic non-union of ulna
Describe how too much gap, poor blood supply and infection leads to non-union and which type of non-union do they lead to
Too much gap – defect non-union
○ 1.5x the diameter of the bone -> will not unite at this point
Poor blood supply – delayed union, malunion, defect, necrotic and atrophic non-union
○ Invasive surgical approach, lack of soft tissue coverage (antebrachium of toy breeds), loose implants especially cerclage wire
○ Lack of soft tissue coverage (antebrachium of toy breeds)
Infection – necrotic non-union
○ Sequestrum and biofilm - infection can lodge into this areas -> prolong the inflammatory phase
○ Bone can heal in the presence of infection
Treatment of viable non-union
- Address the underlying problem
○ Remove loose implants
○ Improve stability if secondary to instability
○ Destabilise if due to stress protection
○ Treat infection if present - Remove fibrous tissue from the fracture site and restore access to the medullary canal via drilling/reaming
- Apply autogenous cancellous bone graft or allografts, DBM, rhBMPs
○ Provides factors -> however if infection osteoblasts may not survive
What are 4 ways to prevent non-union
- Staged destabilisation
- Circular or hybrid ESF
- Use of titanium implants instead of stainless steel
- Locking system and MIPO to preservation of surrounding soft tissue and vascularity
Treatment of nonviable non-union
- Treat underling problem -> Remove sequestra
- Remove fibrous tissue from the fracture site and restore access to the medullary canal via drilling/reaming
- Application of autogenous cancellous bone graft or similar
- Rigid fixation and compression typically with a plate
- If a large defect is present can be addressed by:
○ Cortical autograft or allograft, DBM, rhBMPs
○ Bone transport – distraction osteosynthesis
Osteomyelitis as a complication of fracture repair what damage does it lead to and 3 main clinical signs
- The damage associated with osteomyelitis and its response to treatment is influenced by:
1. The viability and stability of the bone
2. The virulence and antimicrobial sensitivity of the organism
3. The condition of the soft tissue envelope - Clinical signs:
○ Excessive/cloudy/purulent discharge
○ Pyrexia
○ Systemic signs
Open fracture and infection as a complication of fracture repair what leads to and how occurs
- Tissue trauma and ischemia
- Subsequent bone necrosis
- Biofilm formation
○ Conditioning film on top of the internal fixation
○ Glycocalyx -> gel like structure that is the problem -> produced by the bacteria that live within
§ Mechanical barrier to antibiotics
§ Low activity
§ Harsh environment
clinical signs and treatment for acute fracture repair infection
Acute: - Localised swelling and localised pain - Frequently febrile and various systemic illness including lethargy and inappetence - Systemic inflammation (leucocytosis) Treatment: - Debridement - Rigid stabilisation - Appropriate Abs - Better prognosis than chronic
clinical signs and treatment for chronic fracture repair infection
- Localised disease
- Rarely present with systemic changes (draining tracts and lameness)
Treatment: - Tissue ischemia is the major issue
- Removal of infected bone, soft tissue, implants
- Appropriate Abs (i.e., localised AB impregnated PMMA)
Soft tissue coverage and blood supply
Implant failure define and the 3 main causes
- Inadequate implant selection or application
- A race between fracture union and the implant failure during healing time
Causes
1. Fatigue failure:
○ repetitive lower loads
○ Most common
2. Overload failure:
○ single large load more than the yield stress of the implant or bone implant interface
3. Biological failure (secondary):
○ Tissue trauma and ischemia due to initiating injury or an inappropriate surgical technique
○ poor postoperative management (inadequate confinement of a patient)
Implant failure treatment
- Implant removal, revision of construct and consideration of the local healing environment
- Improve healing environment by attempting to improve the blood supply of the region
- Stimulate bone formation through Cancellous bone grafts or addition of exogenous products such as DBM and BMPs
