BackgroundCanine ventral atlantoaxial (AA) stabilization is most commonly performed in very small dogs and is technically challenging due to extremely narrow bone corridors. Multiple implantation sites have been suggested but detailed anatomical studies investigating these sites are lacking and therefore current surgical guidelines are based upon approximate anatomical landmarks. In order to study AA optimal safe implantation corridors (OSICs), we developed a method based on computed tomography (CT) and semi-automated three-dimensional (3D) mathematical modelling using OsiriX™ and Microsoft®Excel software. The objectives of this study were 1- to provide a detailed description of the bone corridor analysis method and 2- to assess the reproducibility of the method. CT images of the craniocervical junction were prospectively obtained in 27 dogs and our method of OSIC analysis was applied in all dogs. For each dog, 13 optimal implant sites were simulated via geometrical simplification of the bone corridors. Each implant 3D position was then defined with respect to anatomical axes using 2 projected angles (ProjA). The safety margins around each implant were also estimated with angles (SafA) measured in 4 orthogonal directions. A sample of 12 simulated implants was randomly selected and each mathematically calculated angle was compared to direct measurements obtained within OsiriX™ from 2 observers repeated twice. The landmarks simulating anatomical axes were also positioned 4 times to determine their effect on ProjA reproducibility.ResultsOsiriX could be used successfully to simulate optimal implant positions in all cases. There was excellent agreement between the calculated and measured values for both ProjA (ρc = 0.9986) and SafA (ρc = 0.9996). Absolute differences between calculated and measured values were respectively [ProjA = 0.44 ± 0.53°; SafA = 0.27 ± 0.25°] and [ProjA = 0.26 ± 0.21°; SafA = 0.18 ± 0.18°] for each observer. The 95 % tolerance interval comparing ProjA obtained with 4 different sets of anatomical axis landmarks was [−1.62°, 1.61°] which was considered appropriate for clinical use.ConclusionsA new method for determination of optimal implant placement is provided. Semi-automated calculation of optimal implant 3D positions could be further developed to facilitate preoperative planning and to generate large descriptive anatomical datasets.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0824-3) contains supplementary material, which is available to authorized users.

Case summaryA 10-year-old neutered male domestic shorthair cat presented for evaluation of acute onset of paraplegia with loss of nociception and thoracolumbar spine hyperesthesia and no history of trauma. Activated partial thromboplastin time (aPTT) was markedly prolonged, and specific coagulation factor testing revealed a factor IX level of 4% of normal activity, confirming the presence of mild hemophilia B. Prior abnormal bleeding had occurred at the time of castration as a kitten, as well as with laceration to a toe. Advanced imaging, including computed tomography (CT) and magnetic resonance imaging (MRI) of the thoracolumbar spine, confirmed the presence of multifocal intradural and intramedullary spinal cord hemorrhage through demonstration of focal ring enhancement on CT and multifocal areas of signal void on gradient echo T2* images on MRI. Despite factor IX supplementation through the use of fresh frozen plasma transfusions and normalization of the aPTT time, the cat’s neurological status did not improve. Owing to repeated urinary tract infections, with increasing resistance to antibiotic therapy, the cat was ultimately euthanized. Post-mortem examination showed no evidence of another underlying primary pathology for the hematomyelia.Relevance and novel informationTo our knowledge, this case demonstrates the first reported occurrence of spontaneous hematomyelia secondary to hemophilia B in a cat.

Background Although the presence of seizures in dogs with meningoencephalitis of unknown origin (MUO) has been associated with shorter survival times, data regarding the prevalence and risk factors for postencephalitic epilepsy (PEE) is lacking. Objectives To describe the clinical features, prevalence, risk factors, and long‐term outcome of PEE in dogs with MUO. Animals Sixty‐one dogs with presumptive diagnosis of MUO based on the clinicopathological and diagnostic imaging findings. Methods Retrospective study. Cases were identified by search of hospital medical records for dogs with suspected or confirmed MUO. Medical records of dogs meeting inclusion criteria were reviewed. Signalment, seizure history, clinicopathologic, and magnetic resonance imaging (MRI) findings were recorded. Results Among 61 dogs at risk of PEE, 14 (23%) dogs developed PEE. Three of 14 dogs with PEE (21%) developed drug‐resistant epilepsy. Dogs with PEE were younger (P = .03; ORadjusted = 0.75; 95% confidence interval [CI], 0.58‐0.98) and had significantly shorter survival times (log‐rank test P = .04) when compared to dogs that did not develop epilepsy. The risk factors associated with the development of PEE were the presence of acute symptomatic seizures (ASS; P = .04; ORadjusted = 4.76; 95% CI, 1.11‐20.4) and MRI lesions in the hippocampus (P = .04; ORadjusted = 4.75; 95% CI, 1.07‐21.0). Conclusions and Clinical Importance Dogs with MUO and seizures at the early stage of the disease (ASS) seem to be at a higher risk of developing PEE.

Dorsal atlantoaxial stabilisation (DAAS) has mostly been described to treat atlantoaxial instability using low stiffness constructs in dogs. The aim of this study was to assess the feasibility and surgical outcome of a rigid cemented DAAS technique using bone corridors that have not previously been reported. The medical records of 12 consecutive dogs treated with DAAS were retrospectively reviewed. The method involved bi-cortical screws placed in at least four of eight available bone corridors, embedded in polymethylmethacrylate. Screw placement was graded according to their position and the degree of the breach from the intended bone corridor. All DAAS procedures were completed successfully. A total of 72 atlantoaxial screws were placed: of those, 51 (70.8%) were optimal, 17 (23.6%) were suboptimal, and 4 (5.6%) were graded as hazardous (including 2 minor breaches of the vertebral canal). Surgical outcome was assessed via a review of client questionnaires, neurological examination, and postoperative CT images. The clinical outcome was considered good to excellent in all but one case that displayed episodic discomfort despite the appropriate atlantoaxial reduction. A single construct failure was identified despite a positive clinical outcome. This study suggests the proposed DAAS is a viable alternative to ventral techniques. Prospective studies are required to accurately compare the complication and success rate of both approaches.