Effect of Ovariohysterectomy at the Time of Tumor Removal in Dogs with Mammary Carcinomas: A Randomized Controlled Trial.

BACKGROUND: Ovarian hormones play crucial roles in mammary carcinogenesis. However, whether ovarian ablation by ovariohysterectomy (OHE) improves the prognosis in dogs with mammary carcinomas is unclear. OBJECTIVES: Determine if OHE at the time of mastectomy improves the prognosis in dogs with mammary carcinomas and evaluate if hormonal factors influence the effect of OHE. ANIMALS: Sixty intact dogs with mammary carcinomas. METHODS: Dogs were randomly assigned in a 1:1 ratio to undergo OHE (n = 31) or not (n = 29) at the time of tumor removal. Peri-surgical serum estradiol (E2) and progesterone concentrations were measured, tumor diagnosis was confirmed histologically, and tumor estrogen and progesterone receptor status was immunohistochemically determined. The dogs were monitored for recurrence and metastases every 3-4 months for at least 2 years. Uni- and multivariable survival analyses were performed with relapse and all-cause death as endpoints in addition to univariable subgroup analyses. RESULTS: Overall, OHE did not significantly decrease hazard of relapse (hazard ratio [HR], 0.64; P = .18) or all-cause death (HR, 0.87; P = .64) in univariable analyses. In multivariable analysis OHE did not significantly influence the hazard of relapse (HR, 0.54; P = .12), but an interaction effect was identified between ER status and E2 (P = .037). Subgroup analysis identified decreased hazard of relapse in the OHE group compared to the non-OHE group in the subsets of dogs with increased E2 (HR, 0.22; P = .012) or grade 2 tumors (HR, 0.26; P = .02). CONCLUSION: Dogs with grade 2, ER-positive tumors, or with increased peri-surgical serum E2 concentration represent a subset of dogs with mammary carcinomas likely to benefit from OHE.

Canine mammary gland tumours; a histological continuum from benign to malignant; clinical and histopathological evidence.

This study describes the clinical and histopathological findings in dogs with mammary gland tumours, and compares the histopathological and clinical evidence consistent with progression from benign to malignant to human breast cancer epidemiology. Clinical and histopathological data on 90 female dogs with 236 tumours was included. Dogs with malignant tumours were significantly older than dogs with benign tumours (9.5 versus 8.5 years), P = 0.009. Malignant tumours were significantly larger than benign tumours (4.7 versus 2.1 cm), P = 0.0002. Sixty-six percent had more than one tumour, and evidence of histological progression was noted with increasing tumour size. Dogs with malignant tumours were significantly more likely to develop new primary tumours than dogs with benign tumours, P = 0.015. These findings suggest that canine mammary tumours progress from benign to malignant; malignant tumours may be the end stage of a histological continuum with clinical and histopathological similarities to human breast carcinogenesis.

Biomechanical characterization of passive laxity of the hip joint in dogs.

OBJECTIVE: To investigate the in vitro load/displacement characteristics of the hip joints in dogs as a function of joint position. SAMPLE POPULATION: 10 hip joints from 5 healthy dogs. PROCEDURE: A material test system was used to generate load/displacement curves for each joint. Joints were mounted in a custom-designed jig that held the joint in fixed anatomic orientations while plotting displacement and corresponding applied loads. All hips were cycled between 40 N of compression and 80 N of distraction. Each hip was tested at 10 degrees increments from 30 degrees flexion to 70 degrees extension. RESULTS: When the hips were in a neutral orientation (approximately a standing position), load/displacement curves were characteristically sigmoidal (tri-phasic), indicating that, in this position, displacement was not highly dependent on load. The curves had a central low-stiffness region in which most of the lateral displacement took place. In contrast, when hips were positioned at the extremes of flexion and extension, this central, low-stiffness region was less distinct, and load/displacement curves were more linear, indicating a proportional relation between load and displacement. The load/displacement curve of 1 hip joint in the study deviated markedly from the others in a pattern consistent with cavitation of the synovial fluid. CONCLUSIONS: When the hip joint is positioned in a neutral position, load-displacement behavior is sigmoidal, whereas when the hip joint is in an extended position, load/displacement behavior is more linear. CLINICAL RELEVANCE: Establishing load/displacement behavior of the hip joints in dogs was an important exercise in establishing the position for and estimating the repeatability of a clinical stress-radiographic method for quantitating joint laxity in dogs.

Biomechanical study of the effect of coxofemoral positioning on passive hip joint laxity in dogs.

Ten coxofemoral joints from 5 dog cadavers were used to study the effect of coxofemoral positioning on passive hip laxity. A material test system was used to measure lateral translation when force was between 20 N of compression and 40 N of distraction. Using the orthogonal coordinate system imposed in this study, neutral position was empirically defined at 15 degrees of extension and 10 degrees of abduction, relative to the plane of the pelvis, and no internal or external rotation of the femur. The hips were mounted in a custom-designed jig that allowed 1 rotational degree of freedom (ie, either flexion/extension, adduction/abduction, or internal/external rotation), while holding the other 2 constant. Lateral translation of the hips was tested at 10 degrees intervals from 30 degrees of flexion to 70 degrees of extension, 40 degrees of adduction to 60 degrees of abduction, and 30 degrees of internal rotation to 40 degrees of external rotation. Lateral displacement was maximal at 10 degrees of extension, 20 degrees of abduction, and 10 degrees of external rotation, approximating the neutral coxofemoral position during stance. As the hips were rotated into extreme positions, the amount of lateral displacement occurring with the same applied load decreased significantly to 32.0 to 65.3% of the maximal displacement. Determining the position of the hip associated with maximal passive laxity in vitro is essential to the design of a precise and accurate clinical stress-radiographic method to quantitate joint laxity in dogs. Our results confirm earlier work that passive hip joint laxity is at a maximum with the hip approximately in a neutral weight-bearing position.

Unilateral and bilateral stifle arthrodesis in eight dogs.

Nine stifle arthrodeses in eight dogs were reviewed retrospectively to evaluate use of the limb, each dog's comfort, complications, and factors that may have influenced the final outcome. Ability to use the limb after unilateral fusion was good (limb used at all times) in three dogs, fair (limb used at all gaits except a gallop) in three dogs, and poor (limb used only when running) in one dog. Factors that appeared to affect the outcome included angle at which the stifle was fused and lesions in the ipsilateral coxofemoral joint. One dog with bilateral arthrodesis had a good outcome with minor limitations. The only potentially devastating complications occurred in one dog in which infection and premature implant loosening jeopardized the fusion. None of the dogs exhibited signs of pain and all owners were satisfied with the results.