Use of a Modified Intramedullary Pinning Technique for Distal Femoral Physeal Salter-Harris Type I and II Fracture Management: A Retrospective Study of 31 Cats.

OBJECTIVE: To report a modified intramedullary pinning technique, and associated outcomes, for distal femoral physeal Salter-Harris type I and II fracture management in cats. STUDY DESIGN: Retrospective study including client-owned cats presented between November 2014 and February 2022 with distal femoral physeal fractures treated with an intramedullary pin and one antirotational pin inserted in the lateral femoral condyle. Collected data included signalment, fracture characteristics according to the Salter-Harris classification, surgical data (intramedullary and antirotational pin sizes), and outcome data (radiographic and functional outcomes and complications). RESULTS: Thirty-one cats were included in this study. Bone healing was radiographically confirmed 6 to 8 weeks postoperatively in all cases. The majority of cats (30/31) were classified as full functional outcomes at mid-term follow-up. The overall mid-term complication rate was 3% (1/31). Implant migration was not observed and implant removal was not needed in any case. CONCLUSION: The modified intramedullary pinning technique for distal femoral Salter-Harris I and II fracture management in cats was associated with an full functional outcome.

Metastatic extradural melanoma of the lumbar spine in a cat.

A 7-year-old neutered male Domestic shorthair cat, with a 1.5-year history of left eye enucleation secondary to a diffuse iris malignant melanoma, was evaluated for progressive onset of pelvic limb paresis and ataxia with severe thoracolumbar hyperaesthesia and dysorexia. Neurological examination localised a lesion to the T3-L3 spinal cord segments. Magnetic resonance imaging of the thoracolumbar spine showed a well-defined extradural T1-weighted hyperintense non-contrast-enhancing mass, initially suggesting a potential haemorrhagic component. Exploratory surgery revealed a brownish extradural lumbar mass. Histologic examination concluded to a melanoma, most probably metastatic given the animal's previous medical history. This report highlights the importance of collecting a complete medical history, which can help in obtaining a preliminary differential diagnosis in cats with clinical signs of myelopathy. Although the location of this metastasis is particularly unusual both in human and veterinary medicine, making optimal treatment challenging for neurosurgeon, our increased understanding of immune and tumour cell biology during the past decade is likely to improve the future treatments of feline melanoma and its metastases.

The Effects of Housing Density on Social Interactions and Their Correlations with Serotonin in Rodents and Primates.

Population density has been suggested to affect social interactions of individuals, but the underlying neural mechanisms remain unclear. In contrast, neurotransmission of monoamines such as serotonin (5-HT) and dopamine (DA) has been demonstrated to play important roles in social behaviors. Here, we investigated whether housing density affected social interactions of rodents and non-human primates housed in groups, and its correlations with monoamines. Japanese macaques exhibited higher plasma 5-HT, but not DA, concentrations than rhesus macaques. Similarly, C57BL/6 mice exhibited higher plasma and brain tissue 5-HT concentrations than DBA2 mice. Under crowding, C57BL/6 mice and Japanese macaques exhibited more prominent social avoidance with mates than DBA2 mice and rhesus macaques, respectively. Although DBA2 mice and rhesus macaques in crowding exhibited elevated plasma stress hormones, such stress hormone elevations associated with crowding were absent in C57BL/6 mice and Japanese macaques. Administration of parachlorophenylalanine, which inhibits 5-HT synthesis, increased social interactions and stress hormones in C57BL/6 mice under crowding. These results suggest that, animals with hyperserotonemia may exhibit social avoidance as an adaptive behavioral strategy to mitigate stress associated with crowding environments, which may also be relevant to psychiatric disorder such as autism spectrum disorder.