Internet-based survey on diagnosis and treatment recommendations for medial shoulder syndrome and instability in dogs.

Objective: The aim of this study was to document perceived frequency of medial shoulder syndrome and instability (MSS/MSI) among dogs, and preferred diagnostic and treatment options related to the condition, among American or European Colleges of Veterinary Surgeons (ACVS/ECVS) diplomates, American College of Veterinary Sports Medicine and Rehabilitation (ACVSMR) diplomates, and dual diplomates of ACVS/ECVS and ACVSMR (double-Boarded diplomates). Procedure: An invitation to complete an online survey was sent to diplomates via email listservs. Results: The known response rate for the survey was 15.8% (160 of 1014 email addresses). There was a difference (P = 0.006) among groups in number of cases of MSS/MSI seen, with ACVS/ECVS diplomates and double-Boarded diplomates seeing 0 to 5 cases per year (80.7 and 72.7%, respectively) and ACVSMR diplomates (32% of total respondents) seeing 11 to 26+ cases annually. The majority of all respondents (56.4%) felt the likely cause of MSS/MSI to be chronic/repetitive strain. Diagnostically, most respondents (78%) relied on shoulder abduction angles; however, most felt it was a questionable or somewhat accurate diagnostic test. The ACVSMR diplomates (88%) relied on musculoskeletal ultrasound as their preferred diagnostic modality, compared to only 35% of ACVS/ECVS diplomates and 45% of double-Boarded diplomates. Preferred treatment was rehabilitation with surgery for unresponsive cases, as reported by 86.9% of all respondents. Preferred surgical treatment was prosthetic ligament reconstruction (62.7%). Conclusion: Despite the low known response rate of this survey, there were significant differences among specialties regarding frequency of MSS/MSI cases seen per year and preferred diagnostic modalities. However, there were no differences among specialties regarding the suspected underlying causes of MSS/MSI and initial treatment strategies.

Enquête en ligne sur le diagnostic et les recommandations thérapeutiques pour le syndrome et l'instabilité médiale de l'épaule chez le chien. Objectif: Le but de cette étude était de documenter la fréquence perçue du syndrome et de l'instabilité médiale de l'épaule (MSS/MSI) chez les chiens, ainsi que les options de diagnostic et de traitement préférées liées à cette maladie, parmi les spécialistes des collèges américains ou européens de chirurgiens vétérinaires (ACVS/ECVS), les spécialistes de l'American College of Veterinary Sports Medicine and Rehabilitation (ACVSMR) et les spécialistes doubles ACVS/ECVS et ACVSMR. Procédure: Une invitation à répondre à un sondage en ligne a été envoyée aux spécialistes via des listes de diffusion de courrier électronique. Résultats: Le taux de réponse connu pour l'enquête était de 15,8 % (160 sur 1 014 adresses courriel). Il y avait une différence (P = 0,006) entre les groupes dans le nombre de cas de MSS/MSI vus, les spécialistes de l'ACVS/ECVS et les spécialistes doubles voyant 0 à 5 cas par an (respectivement 80,7 et 72,7 %) et les spécialistes de l'ACVSMR (32 % du total des répondants) voient 11 à 26+ cas par an. La majorité de tous les répondants (56,4 %) ont estimé que la cause probable du MSS/MSI était une tension chronique/répétitive. Sur le plan diagnostique, la plupart des répondants (78 %) se sont appuyés sur les angles d'abduction de l'épaule; cependant, la plupart estimaient qu'il s'agissait d'un test diagnostique douteux ou quelque peu précis. Les spécialistes de l'ACVSMR (88 %) ont eu recours à l'échographie musculosquelettique comme modalité diagnostique privilégiée, contre seulement 35 % des spécialistes de l'ACVS/ECVS et 45 % des spécialistes doubles. Le traitement préféré était la réadaptation chirurgicale pour les cas qui ne répondaient pas, comme l'ont indiqué 86,9 % de tous les répondants. Le traitement chirurgical préféré était la reconstruction ligamentaire prothétique (62,7 %). Conclusion: Malgré le faible taux de réponse à cette enquête, il existe des différences significatives entre les spécialités concernant la fréquence des cas de MSS/MSI observés par an et les modalités de diagnostic préférées. Cependant, il n'y avait aucune différence entre les spécialités concernant les causes sous-jacentes suspectées de MSS/MSI et les stratégies de traitement initiales.(Traduit par Dr Serge Messier).

Physical Rehabilitation for the Management of Canine Hip Dysplasia: 2021 Update.

Hip dysplasia is one of the most common orthopedic conditions affecting dogs. Initially, laxity of the femur leads to subluxation, and subluxation can lead to an abnormal development or to progressive degeneration of the femoral head and dorsal acetabular rim. Osteoarthritis and its clinical impact progress over time. Changes to the femoral head and neck and the acetabulum and the impact on joint motion and pain vary widely among dogs. The rehabilitation of dogs with hip dysplasia includes rehabilitation therapy in dogs managed conservatively and the rehabilitation of dogs managed with surgery.

Combined center of rotation of angulation-based leveling osteotomy and tibial tuberosity transposition: An ex vivo mechanical study.

OBJECTIVE: To describe the technique of combined center of rotation of angulation (CORA)-based leveling osteotomy (CBLO) with tibial tuberosity transposition (TTT) and to compare the load to failure between CBLO combined with TTT and CBLO or TTT alone. STUDY DESIGN: Ex vivo study. SAMPLE POPULATION: Twelve pairs of cadaveric pelvic limbs. METHODS: Six pairs of cadaveric tibia were tested in each group (CBLO-TTT versus CBLO) and (CBLO-TTT versus TTT) with each limb randomly assigned to a treatment group. Construct stability was determined by applying a tensile force to each patellar tendon until failure occurred. Load at failure and mode of failure were recorded for each specimen. RESULTS: No difference in mean load to failure was identified between CBLO-TTT (897 N) and CBLO alone (943 N) (P = .81). There was also no difference in the mean load to failure between the CBLO-TTT (928 N) and TTT alone (1046 N) (P = .12). CONCLUSION: Performing a TTT in combination with a CBLO does not weaken the construct failure to load when compared with each procedure performed alone. CLINICAL SIGNIFICANCE: A combined CBLO and TTT could be considered a viable option for concurrent management of a cranial cruciate ligament deficient stifle and medial patella luxation.

What Is Your Diagnosis?

In collaboration with the American College of Veterinary Radiology.

Center of rotation of angulation-based leveling osteotomy for stifle stabilization in skeletally immature dogs.

OBJECTIVE: To describe short-term outcomes of center of rotation of angulation (CORA)-based leveling osteotomy (CBLO) in skeletally immature dogs with cranial cruciate ligament (CrCL) injury. STUDY DESIGN: Retrospective case series. ANIMALS: Fifteen skeletally immature dogs (16 stifles). METHODS: Medical records of dogs with CrCL injury and radiographically documented open proximal tibial physis and tibial tuberosity apophysis managed with CBLO were reviewed. Clinical assessment, radiographic assessment, and complications were reviewed. RESULTS: Fifteen dogs (16 stifles) with radiographically documented open proximal tibial physis and tibial tuberosity apophysis and CrCL injury underwent a CBLO. Mean tibial plateau angle (TPA) was 26° preoperatively, 9° postoperatively, and 9° at final recheck. One dog developed 10° recurvatum of the proximal tibia secondary to inadvertent over rotation of the tibial plateau (TPA 3°) to protect primary repair of an insertional CrCL avulsion. Correction of the recurvatum was declined as the dog had full limb function. Two dogs developed a valgus deformity secondary to a plate screw engaging the distolateral aspect of the proximal tibial physis. Owners of these dogs reported normal function but requested surgical revision to prevent long-term problems secondary to abnormal weight bearing. Both dogs regained full function following recovery from revision surgery. At a mean time of 23 months following surgery, all dogs continued to have full function as per phone conversation with owners. CONCLUSION: With proper preoperative planning, CBLO is an option for skeletally immature dogs with CrCL injury.

Ex vivo biomechanical comparison of four Center of Rotation Angulation Based Leveling Osteotomy fixation methods.

OBJECTIVE: To compare the strength of four constructs used to secure an osteotomy in a Center of Rotation Angulation (CORA)-Based Leveling Osteotomy (CBLO) in an ex vivo model. STUDY DESIGN: Ex vivo study. SAMPLE POPULATION: Thirty-two canine tibiae from 17 skeletally mature cadavers weighing between 18 and 33.2 kg. METHODS: Thirty-two paired tibiae with patella and patellar tendon were collected. Each tibia was randomly allocated to a construct group: plate and pin (Plate), plate with countersink compression screw (HCS), plate with tension band (TB), or plate with HCS and TB (HCSTB). Samples were loaded by distraction until failure. The stiffness, yield load, and ultimate load were compared between each fixation method. RESULTS: No difference in stiffness of the constructs was detected between groups (p = .6937). Yield load for the HCSTB group (1211.06 N) was greater than the TB group (1016.41 N), the HCS group (907.20 N), and the Plate group (787.73 N) (p = .0069). The ultimate load for the HCSTB group (1387.82 N) was greater than the TB group (1076.36 N), HCS group (926.62 N), and the Plate group (774.35 N) (p = .0004). CONCLUSIONS: CBLO fixation augmented with a TB and HCS provided a stronger construct that withstood a greater yield load and ultimate load than either augmentation strategy alone. CLINICAL SIGNIFICANCE: Augmenting a CBLO fixation with a TB and a HCS can provide increased construct strength.

Timing of and risk factors for deep surgical site infection requiring implant removal following canine tibial plateau leveling osteotomy.

OBJECTIVE: To identify demographic risk factors for deep surgical site infection (SSI) requiring tibial plateau leveling osteotomy (TPLO) implant removal and time to implant removal. ANIMALS: Four hundred and thirty-three dogs that underwent a TPLO (144 that developed a deep SSI and required implant removal, 289 that did not). STUDY DESIGN: Retrospective case-control study. METHODS: Records of dogs undergoing implant removal due to a deep SSI after TPLO between 2006 and 2018 at two referral centers were reviewed. These records were frequency-matched by date to dogs undergoing TPLO that did not require implant removal. Multivariable analyses tested associations between demographics and implant removal as well as timing of implant removal. RESULTS: Deep SSI and implant removal occurred in 144 of 4813 (3.0%; 95% CI: 2.5, 3.5) dogs treated with TPLO. Implant removal was performed at a median of 279 days (range 49-2394 days) postoperatively. Male dogs (OR 1.8; 95% CI: 1.2, 2.7) and German Shepherd dogs (GSDs) (OR 7.4; 95% CI: 2.6, 20.5) were associated with plate removal. Earlier TPLO plate removal was associated with GSDs only (HR 2.4; 95% CI: 1.4, 4.1). CONCLUSION: Implant removal due to SSI after TPLO was uncommon, although male dogs and GSDs seemed predisposed to this complication. SIGNIFICANCE: These demographic risk factors can be used to educate owners regarding perioperative management.

The Shoulder Joint and Common Abnormalities.

The shoulder is a complex joint composed mostly of static and dynamic capsuloligamentous structures and plays an important role in forelimb lameness. Its complex anatomy and biomechanics necessitate thorough examination and diagnostic work-up for accurate diagnosis. This article provides an updated review of common canine shoulder pathologies, including osteochondrosis, bicipital and supraspinatus tendinopathies, infraspinatus contracture, medial shoulder syndrome, and luxation.

Arthroscopic tenotomy for treatment of biceps tendon luxation in two apprehension police dogs.

CASE DESCRIPTION: A 7.5-year-old 37.8-kg (83.2-lb) sexually intact male German Shepherd Dog (dog 1) and a 2.6-year-old 28.2-kg (62.0-lb) sexually intact male Dutch Shepherd (dog 2), both apprehension police dogs, were admitted for evaluation of left and right thoracic limb lameness, respectively. CLINICAL FINDINGS: In both dogs, signs of pain were elicited on palpation of the shoulder joint in the affected limb, and a distinct popping of the biceps brachii tendon (BT) was palpable on the craniomedial aspect of the affected joint on flexion and extension and was associated with moderate signs of pain. Biceps brachii tendon luxation (BTL) was diagnosed with dynamic musculoskeletal ultrasonography (both dogs) and MRI (dog 1). TREATMENT AND OUTCOME: Arthroscopic BT release by tenotomy was performed in both dogs. Lameness appeared to have resolved by 8 weeks after surgery and had not recurred by the last follow-up communications at 36 and 9 months after surgery for dogs 1 and 2, respectively. Both dogs successfully returned to their level of work performed before their injury. CLINICAL RELEVANCE: Our findings for the dogs of the present report suggested that arthroscopic BT release could be considered a viable treatment option for BTL in dogs, including police dogs or other high-performance athletic dogs. Although our findings provided encouraging results, further research, best conducted with a multicenter prospective randomized study, would be needed to establish the most reliable treatment of BTL in high-performance athletic or working dogs.

Stance and weight distribution after tibial plateau leveling osteotomy in fore limb and hind limb amputee dogs.

BACKGROUND: Little is known about the weight distribution to the remaining limbs for amputee dogs that undergo orthopedic surgery. The objective of the paper was to describe stance and weight distribution after tibial plateau leveling osteotomy (TPLO) in forelimb and in hind limb amputees (AmpTPLO) and to compare them to four-legged TPLO patients (4LTPLO) and amputees without TPLO (Amp). Weight bearing distribution at a stance was compared between groups. Joint angles of forelimb and hind limb joints in a sagittal plane, hind limb orientation in a frontal plane, and pelvic orientation in a transverse plane (pelvic tilt) were measured and compared between groups. RESULTS: Joint angles, hind limb abduction, and pelvic tilt of AmpTPLO and Amp did not differ statistically. Mean weight bearing in the operated hind limb was higher for AmpTPLO than 4LTPLO. Mean weight bearing for thoracic limbs of AmpTPLO and 4LTPLO did not differ statistically. Weight bearing of the hind limb of AmpTPLO and Amp did not differ statistically. CONCLUSIONS: The position of the center of mass and posture of AmpTPLO and Amp does not differ. The weight distribution and posture of Amp is not impacted negatively by TPLO.

Average Tibial Plateau Angle of 3,922 Stifles Undergoing Surgical Stabilization for Cranial Cruciate Ligament Rupture.

OBJECTIVE: The aim of this study was to report the average tibial plateau angle (TPA) from a large sample of dogs and to determine if breed or gonadectomy had a significant association with abnormal TPA. STUDY DESIGN: This was a retrospective case study. MATERIALS AND METHODS: Medical records from 2006 to 2015 were reviewed for dogs that were diagnosed with cranial cruciate ligament (CrCL) rupture and underwent dynamic surgical stabilization. Signalment, examination findings, preoperative TPA and surgical report were reviewed. RESULTS: A total of 3,249 dogs underwent CrCL stabilization surgery from 2006 to 2015. Of the 3,249 dogs, 3,054 dogs met the inclusion criteria for a total of 3,922 stifles to be evaluated. The average preoperative TPA was 29° ± 3.7°. Average breed-specific preoperative TPA ranged from 27° to 35.1°, with four breeds having significantly lesser TPA and four breeds significantly greater TPA than the overall mean of dogs. Neutered dogs had a higher TPA of 28.87° ± 3.8° than non-neutered dogs with an average TPA of 26.88° ± 4.0°, p < 0.001. There was not a significant difference in average TPA between females and males, regardless of the neuter status. CONCLUSION AND CLINICAL RELEVANCE: Our reported preoperative TPA in a large sample of dogs is higher than what has been previously published. In reviewing 3,922 stifles, the average preoperative TPA was 29°. We report the average preoperative TPA in specific breeds and report that neutered dogs have a significantly higher TPA than intact dogs. This updated information may guide clinicians in management decisions regarding treatment for CrCL rupture.

Sensitivity and Specificity of a Weight Distribution Platform for the Detection of Objective Lameness and Orthopaedic Disease.

INTRODUCTION: Weight distribution and off-loading at the stance are commonly used subjective assessments during the orthopaedic examination. The clinical relevance, sensitivity and specificity of limb off-loading have not yet been established. The aim of the study was to assess off-loading on a weight distribution platform (WDP) and determine the sensitivity and specificity at various cut-off points for the detection of objective lameness (OL) and orthopaedic disease (OD). MATERIALS AND METHODS: The total pressure index was used to determine OL on a pressure-sensitive walkway (PSW). Normal weight distribution on both the PSW and WDP was considered 30/30/20/20. A total pressure index standard deviation of 2 was used. The sensitivity and specificity of the WDP for the identification of OL and OD was determined at cut-off points 1 to 6 below normal weight distribution values. RESULTS: All patients in the study (n = 50) had confirmed OD. The PSW identified 36/50 (74%) patients as OL; these were deemed to be OL for sensitivity and specificity analysis of WDP data. At cut-off point 1, the WDP had the highest sensitivity for OD (84%) and OL (97%). At cut-off point 6, the WDP had the highest specificity for OD (98%) and OL (98%). The highest combination of sensitivity and specificity for both OD (1.65) and OL (1.80) was at cut-off point 2. DISCUSSION/CONCLUSION: The WDP provided the highest combined sensitivity and specificity at cut-off point 2 below the normal value for the detection of both OL and OD.

Physical Rehabilitation for the Management of Canine Hip Dysplasia.

Hip dysplasia is among the most common orthopedic conditions affecting dogs. Joint laxity is responsible for abnormal development of the femoral head and acetabulum, leading to excessive wear of the articular cartilage. Wear leads to secondary osteoarthritis. Rehabilitation is either conservative or after surgical management. Conservative rehabilitation therapies are directed at decreasing pain, improving hip range of motion (ROM), and building or maintaining muscle mass. Postoperatively, rehabilitation focuses on decreasing postoperative pain and inflammation, improving comfort and limb use, and protecting the surgical site. Once the patient has healed, rehabilitation is directed at improving ROM and promoting muscle mass.

Adhesive Capsulitis in Eight Dogs: Diagnosis and Management.

OBJECTIVE: To describe clinical and diagnostic findings as well as management of adhesive capsulitis in dogs. BACKGROUND: Adhesive capsulitis, also known as frozen shoulder, is a syndrome defined by loss of range of motion of the shoulder and may be the end-stage manifestation of several primary conditions. EVIDENTIARY VALUE: This is a case series report of eight dogs with chronic forelimb lameness diagnosed with adhesive capsulitis. METHODS: Medical records (June 1, 2010-September 1, 2015) including, physical examination findings, radiographic findings, magnetic resonance imaging (MRI) findings, arthroscopy findings, and treatment plans were reviewed. RESULTS: All dogs presented with a chronic, grade III-VI/VI forelimb lameness. On orthopedic examination, all dogs had moderate to significant discomfort on shoulder extension and flexion and severe restriction of range of motion. Six of the eight dogs had evidence of bone remodeling and sclerosis in the affected shoulder on radiographs. Six of the dogs had an initial diagnostic ultrasound performed, which revealed evidence of fibrous scar tissue. Five dogs had MRI performed that revealed moderate shoulder effusion and enhancement of the synovial lining of the shoulder. Arthroscopy was performed in five of the eight patients. Three were noted to have significant contracture, adhesions, and fibrous scar tissue of the joint capsule. Severe inflammation was noted throughout the synovium of two patients. All eight patients tried conservative management consisting of oral medications and rehabilitation therapy. Five of the eight patients received extracorporeal shockwave therapy. Three patients received regenerative medicine treatment in the affected supraspinatus and shoulder. Regardless of the treatment elected, none of the dogs were reported to have significant improvement. CONCLUSION: Adhesive capsulitis is an uncommon cause of chronic forelimb lameness. Further investigation is needed to describe the etiology and pathogenesis of adhesive capsulitis in dogs to evaluate the effectiveness of both non-surgical and surgical treatment modalities, establish treatment protocols, and evaluate short- and long-term clinical outcome of patients. APPLICATION: Adhesive capsulitis should be considered in patients with chronic forelimb lameness and moderate to significant discomfort and restriction on shoulder range of motion.

Traumatic fracture of the medial coronoid process in 24 dogs.

OBJECTIVE: To describe traumatic fracture of the medial coronoid process in dogs as a clinically distinct disease unrelated to congenital elbow dysplasia. METHODS: Clinical records of dogs with acute, traumatic, unilateral lameness attributable to medial coronoid process disease were reviewed retrospectively. Clinical interpretation included findings on physical examination, orthopaedic examination, and subjective gait analysis. Radiographs of the affected and contralateral elbows were obtained and reviewed for pathology. Arthroscopy of the elbow joints was performed by one of three surgeons and findings were compared to preoperative diagnostics. Postoperative follow-up was continued for 16 weeks. RESULTS: Twenty-four dogs were included in this study. All dogs in this study were free of radiographic evidence of medial coronoid pathology. All dogs were diagnosed with a single, large, displaced or non-displaced fracture of the medial coronoid process, with no other joint pathology. Dogs generally had an excellent short-term outcome following arthroscopic treatment of the fractured medial coronoid process. CLINICAL SIGNIFICANCE: Traumatic fracture of the medial coronoid process should be considered a clinical disease distinct from dysplasia-related fragmentation and should be considered as a differential diagnosis in dogs that are presented with the complaint of acute unilateral elbow discomfort or lameness, especially after concussive activities involving the forelimb. .

Surgical and Medical Treatment of Pyloric and Duodenal Pythiosis in a Dog.

A 5 yr old, male, neutered mixed-breed dog was referred for persistent vomiting 2 wk following a pyloric biopsy for a pyloric outflow obstruction. Histopathology at the time of initial surgery was suggestive of pythiosis. Following referral, the dog underwent radical surgical treatment with a Billroth II procedure, partial pancreatectomy, and cholecystoduodenostomy. Histopathology and serology confirmed the diagnosis of pythiosis and medical treatment consisting of itraconazole and terbinafine was started postoperatively. Serology titers were checked again at 8, 12, and 24 wk postoperatively revealing a positive response to treatment and no reoccurrence of pythiosis. Since surgery, the patient experienced waxing and waning elevations of liver values and laparoscopic liver biopsies 10 mo postoperatively revealed hepatic cirrhosis with fibrosis, bile duct hyperplasia, and chronic inflammation. This report documents successful treatment of pyloric/duodenal pythiosis and the long-term (17 mo) consequences associated with the Billroth II, partial pancreatectomy, and biliary rerouting in the dog.

In-vitro comparison of 3 knotting techniques for lateral fabellotibial suture stabilization.

This study evaluated the biomechanical characteristics of a single self-locking knot (sSLK) and a double self-locking knot (dSLK) compared with the square knot (SQ) for stabilization of cranial cruciate ligament rupture. Each knot underwent monotonic tensile and cyclical loading. Starting tension, elongation, stiffness, and load to failure were all evaluated. A value of P < 0.05 was considered significant. Starting tension, overall stiffness, and load to failure were all significantly greater in both the sSLK and dSLK compared with the SQ. There was no difference in elongation among the knots. There were no significant differences in starting tension, elongation, stiffness, and load to failure between the sSLK and the dSLK. The self-locking knots were stronger and stiffer than the SQ; there is no biomechanical advantage in using the dSLK compared with the sSLK.

Comparaison in vitro de 3 techniques de nœuds pour la stabilisation des sutures fabello-tibiales latérales. Cette étude a évalué les caractéristiques d'un nœud auto-serrant unique (NASu) et d'un nœud auto-serrant double (NASd) comparativement à un nœud plat (NP) pour la stabilisation d'une rupture d'un ligament croisé crânial. Chaque nœud a subi un effort de tension monotonique et cyclique. La tension de départ, l'élongation, la rigidité et la charge avant la rupture ont toutes été évaluées. Une valeur de P < 0,05 était considérée significative. La tension de départ, la rigidité générale et la charge avant la rupture ont toutes été de beaucoup supérieures avec NASu et NASd comparativement à NP. Il n'y avait pas de différence au niveau de l'élongation parmi les nœuds. Il n'y avait pas de différences importantes dans la tension de départ, l'élongation, la rigidité et la charge avant rupture entre NASu et NASd. Les nœuds auto-serrants étaient plus forts et plus rigides que le NP; il n'y avait pas d'avantage biomécanique à utiliser le NASd comparativement au NASu.(Traduit par Isabelle Vallières).

Modulation of inflammation and oxidative stress in canine chondrocytes.

OBJECTIVE: To determine whether oxidative stress could be induced in canine chondrocytes in vitro. SAMPLE: Chondrocytes obtained from healthy adult mixed-breed dogs. PROCEDURES: Harvested chondrocytes were maintained at 37°C with 5% CO2 for 24 hours. To assess induction of oxidative stress, 2 stimuli were used: hydrogen peroxide and a combination of interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α). To determine the effect of hydrogen peroxide, a set of chondrocyte-seeded plates was incubated with control medium alone or hydrogen peroxide (100, 200, or 300µM) for 24 hours. For inhibition of oxidative stress, cells were incubated for 24 hours with N-acetylcysteine (NAC; 10mM) before exposure to hydrogen peroxide. Another set of chondrocyte-seeded plates was incubated with control medium alone or with IL-1ß (10 ng/mL) and TNF-α (1 ng/mL) for 24 hours. Supernatants were obtained for measurement of prostaglandin E2 production, and cell lysates were used for measurement of superoxide dismutase (SOD) activity and reduced-glutathione (GSH) concentration. RESULTS: Chondrocytes responded to the oxidative stressor hydrogen peroxide with a decrease in SOD activity and GSH concentration. Exposure to the antioxidant NAC caused an increase in SOD activity in hydrogen peroxide-stressed chondrocytes to a degree comparable with that in chondrocytes not exposed to hydrogen peroxide. Similarly, NAC exposure induced significant increases in GSH concentration. Activation with IL-1ß and TNF-α also led to a decrease in SOD activity and increase in prostaglandin E2 production. CONCLUSIONS AND CLINICAL RELEVANCE: Canine chondrocytes responded to the oxidative stress caused by exposure to hydrogen peroxide and cytokines. Exposure to oxidative stress inducers could result in perturbation of chondrocyte and cartilage homeostasis and could contribute to the pathophysiology of osteoarthritis. Use of antioxidants, on the other hand, may be helpful in the treatment of arthritic dogs.