Global epidemiology of ovarian cancer: patterns, trends, and risk factors.

Lesions of the cervical spine are rare in both dogs and cats (). The most commonly affected vertebrae are C1 and C2 (, ), and abnormalities in this region are referred to as atlantoaxial instability (AAI) or atlantoaxial subluxation (AAS). These conditions can be either congenital or acquired (4–6). Acquired, trauma-related fractures, dislocations, or dislocated fractures usually result from car accidents (, , ). Both congenital and developmental lesions of the cervical spine can predispose animals to AAI (). AAI is primarily observed in toy-breed dogs, but it also rarely occurs in larger dogs and cats (, ). Causes of AAI may include hypoplasia or aplasia of the dens of the axis (8,9,14), malformations of the atlantoaxial ligamentous apparatus (), incomplete ossification of the neural arch (), or block vertebrae (). Both conservative and surgical treatment methods have been described for these conditions (, , ). For AAI in particular, both dorsal and ventral surgical approaches have been reported (, , , , ), with ventral fixation frequently employing plates and screws (, , , , , ). Surgical treatment is particularly challenging in small-breed dogs and cats due to their delicate bone structures (), as complications such as implant fracture or loosening occur relatively frequently following surgical intervention (, , ). In human medicine, trabecular structural parameters are known to influence implant stability (, ). In contrast, no studies investigating the trabecular and cortical microarchitecture of the cranial cervical spine in dogs and cats have been published in the accessible veterinary literature to date. Therefore, one objective of the present study was to fill this gap and examine the microarchitecture of the first and second cervical vertebrae (C1-C2) compared to the 3rd and 4th cervical vertebrae (C3, C4). In addition, potential differences between toy-breed dogs and small-breed dogs, as well as cats, were evaluated. Furthermore, the size ratio between the dens and the axis was calculated and compared. The results are intended to contribute to a better understanding of the anatomy and, consequently, to the improved selection of implant placement and, thereby, vertebral fixation. The cervical spines examined in this study were obtained from 20 dogs and 20 cats weighing between 1.3 and 10.8 kg that died or were euthanized for reasons unrelated to cervical spine disorders at the Clinic for Small Animal Surgery and Reproduction, Ludwig Maximilians University of Munich (LMU). The animal carcasses were donated to the clinic by their owners for scientific purposes. The study was approved by the Ethics Committee of the Faculty of Veterinary Medicine at Ludwig Maximilian University of Munich under file number AZ 348–31-01-2023. Only adult animals were included in the study, and the gender distribution was balanced across all groups to minimize differences in age and sex. The median age was comparable across all groups to minimize age-related differences (). Animals with diseases that could reduce bone integrity, such as chronic kidney disease (CKD) or hyperadrenocorticism (HAC), were excluded as far as possible based on their medical histories.