Learning Issues. Case 2. Group 13 Do Pomeranians (small breed dogs) have any musculo/skeletal predispositions? Small breed dog specific problems: Legg Perthes Disease, avascular necrosis of femoral head, clinical presentation of patient does not support this disease process. Which disorders/ injuries could subside and recurr? Fell off bed a year ago: Traumatic incident potentially compromised patellar ligaments and tendons of both the right and left rear legs. Weight bearing lameness on right leg: Trauma to right leg at time of fall induced the lameness. Perhaps the patellar ligament, lateral collateral ligament and the cranial cruciate ligament were over-extended in fall and the joint capsule was stressed, resulting in a mild inflammatory response with minor joint swelling and pain. Subluxation of the joint occurred as the ligaments stretched and this reduced the functional articular surface area. A smaller area of the joint experienced the entire weight of the dog as it landed on the floor therefore there was some cartilage damage. Chondrocytes were damaged and responded by releasing inflammatory mediators that led to mild joint effusion and joint pain (as evidenced by mild lameness). Resolving of right limb lameness after one month due to reabsorption of joint fluid and termination of the mild inflammatory response by chondrocytes. Mild right rear lameness reoccurred 6 months after fall: Perhaps the dog retraumatized right stifle through aggressive play or through another fall. Patellar ligament, lateral collateral ligament and the cranial cruciate ligament were once again over extended and the joint capsule was stressed. However this time the joint subluxation was more severe due to previous laxity in the patellar, lateral collateral and the cranial cruciate ligaments. Due to the severe subluxation that occurred there was significant cartilage damage and chondocytes responded with a strong inflammatory response. What type of disorders would NSAISDs not be effective? Treated with anti-inflammatories after lameness reoccurred and saw no improvement: Fact that previous vet put dog on anti-inflammatories could indicate that they sensed significant stifle joint inflammation. Resolving of right limb lameness after one month due to reabsorption of joint fluid and termination of the mild inflammatory response by chondrocytes. Probably due to chronic osteoarthritis because the inflammatory response will be very minimal. What is medial buttressing? Thickening of joint capsules due to chronic instability. This is indicative for a cranial cruciate rupture in small dogs. Could allergies be a factor? Persistent hypersensitivity response to antigens in lungs causes a massive IgE response and the release of inflammatory mediators by mast cells, basophils, eosinophils and neutrophils. Mast cells and basophils are bound to IgE. IgE, mast cells, basophils, eosinophils and neutrophils are present in systemic circulation and could potentially deposit in the joint space. Perhaps IgE that deposits in the joint space is cross reactive with a self antigen and this cross-reactivity results in immune complexes depositing in the joint space. IgE would stimulate the degranulation of bound mast cells and basophils as it formed immune complexes. This would result in chemotaxis of eosinophils and neutrophils. Major basic protein (from eosinophils) and many other inflammatory mediators would initiate necrosis of chondrocytes and damage to cartilage. What does medial patellar luxation indicate? Common in toy and minature poodles. Indicates the patellar ligament has ruptured on either medial or lateral side, causing luxation to the intact side. Through the traumatic incident described and above and the other speculated incident the patellar ligament was over extended and permanently stretched. The stretched patellar ligament is not effective at holding the patella in place. However the patellar ligament is definitely still in tact because when the joint is flexed the patella returns to the trochlear groove. If the patellar ligament was ruptured there would be no forces to pull the patellar back into it appropriate anatomic position. Which disorders might only effect stifles?Bilaterily? Compensatory? Cranial cruciate ligament rupture-young, active dogs. Non-weight bearing lameness for at least a week. Recurring lameness possible with stress, age, meniscal injury. Collatoral Ligament injuries- Associated with significant trauma, internal dearangement of the stifle, valgus or varus laxity. Caudal cruciate ligaments- injuries cause minimal clinical effects, diagnosis rests on caudal drawer sign which is negative in this case. Meniscus- Associated with concurrent stifle ligament injury, 70-80% of chronic cranial cruciate ligaments have a meniscal tear or it is folded and torn. Can palpate and hear a ÒclickÓ or ÒpopÓ during flexion and extension. Sudden lameness after cranial cruciate ligament recovery. Congenital patellar luxation- See above to see this as rule-out. Biliateral injury could occur if the dog landed equally hard on both stifles, but unlikely. Most probable cause is compensatory weight bearing for the injured stifle in opposite leg. This could lead to chronic osteoarthirtis in both stifle joints. What signifigance does a pain response on dorsal reflexion of the tail? Probable direct trauma to tail in the past since there is no palpable pain response in the spine and lumbo-sacral joint. Maybe the dog got its tail caught in a door? Perhaps there was a subluxation of spinal vertebrae from the traumatic incident the spinal cord recovered and but the tail didnÕt. Perhaps the etiology of this pain in the tail stems from an immune-mediated response described above?