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54 Cards in this Set
- Front
- Back
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How does fetal cartilage differ from mature articular cartilage?
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Fetal cartilage is well vascularized by vessels running through cartilage canals
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What does ossification of primary centers of ossification result in at birth?
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diaphyses of long bones are all are bony
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What does ossification of secondary centers of ossification result in at birth?
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Epiphyses, apophyses, and cuboidal bones are partly cartilaginous
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What process results in longitudinal bone growth?
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Endochondral ossification
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How are chondrocytes arranged for endochondral ossification?
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longitudinal columns which are parallel to the long axis of the bone
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Zones of ossification:
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From closest to the epiphysis to the diaphysis the zones are the zone of resting cartilage, the zone of proliferation, the pre-hypertrophic zone, the hypertrophic zone, and the zone of calcification
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Describe zone of resting cartilage:
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least metabolically active, and contains active chondrocytes
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Describe zone of proliferation:
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chondrocytes divide in a plane perpendicular to the long axis of the bone to increase bone length
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Describe pre-hypertrophic zone:
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chondrocytes become round and become encased in extracellular matrix
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Describe hypertrophic zone:
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chondrocytes stop dividing, increase in size and hypertrophy
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Describe zone of calicification:
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hypertrophied chondrocytes are replaced by mineralized bone and bone marrow
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How does replacement of hypertrophied chondrocytes occur?
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vascular invasion, resorption of cartilaginous maxtrix, recruitment of osteoblasts, osteoblasts deposit bone matrix
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What influences the remodeling of cartilage to bone?
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Biomechanical loading according to wolfe’s law
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Wolfe’s law:
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If loading on a particular bone increases, the bone will remodel itself over time to become stronger to resist that sort of loading, if the loading on a bone decreases, the bone will become weaker due to turnover
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How does articular cartilage develop?
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Thick cartilage mass at the articular side of the epiphysis acts as a type of growth plate with simultaneous growth, remodeling, and ossification take place that results in a thinner layer of articular cartilage
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What does disturbance of endochondral ossification result in?
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irregularities in thickness of epiphyseal cartilage, creating areas of weakness
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What exacerbates weakened areas in epiphyseal cartilage?
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Regression of or occlusion of cartilage vascular canals preventing nutritional supply to deeper layers of the retained cartilage that are too deep to receive nourishment from the synovial fluid
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When do cartilage vascular canals regress?
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By 7 months of age
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What leads to the formation of fissues or cartilage flaps?
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Biomechanical shearing forces on the weakened areas of the epiphyseal cartilage
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What is a manifestation of compressive biomechanical forces on weakened areas of epiphyseal cartilage?
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Infolding of cartilage to form subchondral bone cyst
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Most common OC of the tarsocural joint:
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DIRT (1st), distal lateral trochlear ridge (2nd), medial malleolus of tibia (3rd)
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Most common OC of FP joint:
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lateral trochlear ridge of the femur (1st) other: medial trochlea of femur, trochlear groove, distal end of patella
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Most common OC of MFT joint:
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subchondral cyst of medial femoral condyle
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Most common OC in fetlock:
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dorsal end of sagittal ridge of MC/MT3
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How does cartilage repair differ from bone repair?
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Bone can remodel throughout life but cartilage metabolism ceases early in juvenile period
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What is the consequence of cessation of cartilage metabolism?
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There is no capacity for substantial remodeling or repair and lesions that manifest late or are large are not repaired
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What is osteochondrosis?
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Disturbance of endochondral ossification linked with rapidly changing metabolisc status of articular cartilage in juveniles
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What etiologic factors are associated with OC?
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Biomechanical influences, exercise, failure of vascularization, nutritional imbalances, and genetics
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What nutritional factors may contribute to OC?
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Low copper levels (either low Cu intake or antagonism by Zn or cadmium), high P inducing a 2ndary hyperPTH, increased easily digestable CHO leading to increased insulin & IGF-1
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What effect does insulin & IGF-1 have on endochondral ossification?
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Mitogens for chondrocytes, stimulate chondrocyte survival & suppress apoptosis, decreases T3 & T4 which are involved in final chondrocyte differentiation and in metaphyseal blood vessel invasion of cartilage
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How does growth rate related to OC?
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Rapid growth rate correlated with increased OC but could be from high plane of nutrition or genetic influences
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Radiographic characteristics of SCL:
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radiolucent area with a thin well demarcated sclerotic rim
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Where are SCL usually located?
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SCB underlying articular cartilage in weight bearing area of joint or less commonly in metaphysis close to the growth plate
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How are OC and SCL different?
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OC lesions are usually at transition from weight bearing to not weight bearing articular surface and SCL are at weight bearing surfaces
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What are the theories of SCL development?
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Hydraulic, inflammatory
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What is the hydraulic theory?
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Primary cartilage damage followed by intrusion of synovial fluid, which put mechanical pressure on SCB during weight bearing and resulted in necrosis
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What is the inflammatory theory?
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Fibrous tissue & cystic fluid from SCL have increased proinflammatory mediators and cytokines such as PGE2, IL-1, IL-6
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Most common location of SCL:
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medial femoral condyle of femur (1st) phalanges (2nd)
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What is the source of lameness with SCL?
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Intracystic or intraosseous pressure
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How often do SCL communicate with the joint?
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Approximately 30%
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What is tissue inside the SCL composed of?
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Dense fibrous tissue, myxomatous tissue, with necrotic bone, calcified or mineralized areas, sometimes fibrocartilage
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What is the lining of the SCL composed of?
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Elongated fibroblasts parallel to collagen bundles, macrophages, PMN cells
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SCL radiographic grades:
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grade 1: lesion less than 10mm, dome shaped; grade 2a: lesion more than 10mm in depth with narrow cloaca; grade 2b: lesion more than 10mm in depth with wide cloaca; grade 3: condylar flattening or small defect in SCB; grade 4: lucency in condyle with no radiographic evidence cloaca
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Non-surgical management of SCL:
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rest, NSAIDs, vitamin supplementation, anabolic drugs
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Surgical approaches to SCL:
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arthroscopic, transosseous
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Surgical treatments for SCL:
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curettage & debridement, intralesional corticosteroid injection, grafting
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How is surgical curettage & debridement performed?
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Arthroscopic- remove overlying cartilage then curet; transosseous- drill into cyst first with 2.5mm pilot hole then 5.5 drill then curet
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What is success of surgical curettage & debridement related to?
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Better in younger horses (< 3 years) and better with less than 15mm of surface defect
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What is success of intralesional corticosteroid injection related to?
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Better for unilateral lesions than bilateral
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What are the different grafting options?
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Cancellous bone graft, mosaic arthroplasty, tricalcium phosphate granules (TPC), hydrogels +/- parathormone, autogenous fibrin plugs +/- allogenic chondrocytes or IGF-1, BMC + PrP +TCP
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What are the best graft donor sites for the medial femoral condyle?
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Trochlear groove and axial lateral trochlear ridge of the femur
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What are the best graft donor sites for the lateral femoral condyle?
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Trochlear groove, axial aspect of the medial femoral condyle
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What has been used clinically as a donor site for MFC SCL mosaic arthroplasty?
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Abaxial border of medial femoral trochlea of unaffected limb
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