68.OA Flashcards
define arthritis
disease process within the synovial jointClassified as noninflammatory vs inflammatorybut all display some form of inflammation
“noninflammatory” arthritis
- OSTEOARTHRITIS (DJD, OA, osteoarthrosis)almost always SECONDARY20% adult dogs; 60% adult cats (can be primary in cats)key tissue = ARTICULAR CARTILAGE2. Traumatic3. Coagulopathic
Etiology of osteoarthritis
G-A-B-O-G-E1. Genetics: multiple genes2. Age: incr age= less aggrecans, slow responsiveness to anabolism3. BW: Boxer w hi birthweight, incr risk hip dysplasia/CCL4. Obesity: Lab cohort study signs of OA/HD w ad libitum feeding 42 vs 4% @ 2 YO 5. Gender: neutered boxer 1.5 x risk HD; neutering male/female incr risk CCLR6. Environment: leash exercise (exercise increases VI, PVF in OA patients), diet, housing (slippery floors)
van Hagen et al Incidence, risk factors, and heritability estimates of hind limb lameness caused by hip dysplasia in a birth cohort of Boxers. Am J Vet Res. 2005
neutering at least 6 months before making a dx of clinical hip dysplasia influenced the risk of clinical HD developing over timeneutered Boxers were 1.5 x more likely to develop clinical HD
Beraud, R, Moreau, M, Lussier, B Effect of exercise on kinetic gait analysis of dogs afflicted by osteoarthritis. Vet Comp Orthop Traumatol 2010
force platform GAcontrol and OA dogsbaseline and post exerciseno change with control grouppeak, impulse, and propulsion vertical force values were sign lower post exercise (exercise actually improved limb use)
central theme to pathogenesis of osteoarthritis
alterations in metabolism/morphology articular cartilagechanges in subchondral bone metabolism/architecture (sclerosis)osteophyte/enthesiophyte formationsynovial inflammation and fibrosis
3 overlapping stages of articular cartilage pathogenesis in OA
- ECM degrades, incr water content, decr aggrecan/P size, damage to collegen network–>reduce compressive stiffness2. chondrocytes compensate–prolif (anabolic–thickness stage)3. chondrocytes depleted, complete loss of cartilage tissue (ulcer, eburnation, erosion)
what substance/protein br eaks down type II collagen
intact triple helix of type II collagen can be degraded by MMP 1 and 13 (+/- 8, 14)and aggrecanases
arthroscopic outerbridge classification for OA
0 normal cartilageI softening and swelling of cartilageII fragment/fissuring of area < 0.5 inIII Fragment/fissuring of area > 0.5 inIV cartilage erosion/ eburnated bone
surgical mgmt for OA
- joint debride/micropick (abrasion chondroplasty)–stimulate fibrocartilage2. joint replacement (hip, elbow, knee)3. arthrodesis/salvage excision arthroplasty4. amputation5. euthanasia
normal synovial fluid analysis
< 2n x 10^9 TNCC94-100% mononuclear0-6 % PMN
OA synovial fluid
< 2-5 x 10^9 TNCC88-100% mononuclear0-12 % PMN(similiar to normal OA) mild inflammatory
RA (erosive) synovial fluid
< 8-38 x 10^9 TNCC20-80% mononuclear20-80 % PMN
nonerosive IMPA synovial fluid
< 4-37 x 10^9 TNCC5-85% mononuclear15-95 % PMN
infective arthritis synovial fluid
< 40-267 x 10^9 TNCC 1-10% mononuclear90-100% PMN
medical mgmt for OA
- weight mgmt-exercise, rx diet, rx (microsomal triglyceride transfer P inhibitor)2. exercise–regular, moderate, controlled3. RX–symptom (NSAID) vs structural (stop cartilage damage) rx4. Nutrition (nutraceutical vs functional food J/D)5. Mesenchymal (multi potent) stem cell tx
MOA of NSAIDs
- Cyclooxygenase (COX) inhibitionwith COX inhibition, AA does not convert to PG (PGE2) thus no vasodilation, edema, incr pain noted2. Lipoxygenase (LIPOX) inhibitionif COX path is blocked, incr LIPOX path to make leukotrienes (proinflm, incr PMN, hyperalgesia)Ideally, NSAID would be LIPOX/COX inhibitors
COX 1 vs COX 2
COX 1 constitutive, in many tissues (makes PGs important for normal physiologic function)COX 2 inducible, upregulated w inflm; IS CONSTITUTIVE in kidney, brain and is cytoprotective to GI mucosaselective inhibition of COX 2 without affecting COX 1 will allow analgesia WITHOUT unwanted side effects of Cox 1 inhibitionGOAL: inhibition of COX2 at lower concentration than the concentration needed to inhibit COX1 (either a HIGH COX1:COX2 ratio or LOW COX2:COX1 ratio) pg 1057 Boothe
adverse effects of NSAIDs
GI–vomiting, diarrhea, inappetanceimpaired platelet activity–decr thromboxane (COX 1 selective action)nephrotoxic–PGE2/PGE1 maintain renal BF (COX 1 and COX2 actions)hepatotoxic
prostaglandins and their role for GI integrity
NSAIDS inhibit COX and decrease PG synthesisnatural GI integrity protected by PG mediated: 1. bicarbonate rich mucus2. gastric epithelial cell turnover at apical membrane3. high blood flow to release bicarbonate and neutralize any acid (decr H); also brings oxygen and nutrientsPGE2 maintains mucosal layer, mucus layer, blood flow, and gastric acid production and is made through COX 1 path
carprofen
propionic acid derived NSAIDconsidered COX 2 selective (COX1:COX2 ratio = 17)