Canine atlantoaxial optimal safe implantation corridors - description and validation of a novel 3D presurgical planning method using OsiriX™.

BACKGROUND: Canine 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. RESULTS: OsiriX 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. CONCLUSIONS: A 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.

A structural approach to 3D-printing arterial phantoms with physiologically comparable mechanical characteristics: Preliminary observations.

Pulse wave behavior is important in cardiovascular pathophysiology and arterial phantoms are valuable for studying arterial function. The ability of phantoms to replicate complex arterial elasticity and anatomy is limited by available materials and techniques. The feasibility of improving phantom performance using functional structure designs producible with practical 3D printing technologies was investigated. A novel corrugated wall approach to separate phantom function from material properties was investigated with a series of designs printed from polyester-polyurethane using a low-cost open-source fused filament fabrication 3D printer. Nonpulsatile pressure-diameter data was collected, and a mock circulatory system was used to observe phantom pulse wave behavior and obtain pulse wave velocities. The measured range of nonpulsatile Peterson elastic strain modulus was 5.6-19 to 12.4-33.0 kPa over pressures of 5-35 mmHg for the most to least compliant designs respectively. Pulse wave velocities of 1.5-5 m s-1 over mean pressures of 7-55 mmHg were observed, comparing favorably to reported in vivo pulmonary artery measurements of 1-4 m s-1 across mammals. Phantoms stiffened with increasing pressure in a manner consistent with arteries, and phantom wall elasticity appeared to vary between designs. Using a functional structure approach, practical low-cost 3D-printed production of simple arterial phantoms with mechanical properties that closely match the pulmonary artery is possible. Further functional structure design development to expand the pressure range and physiologic utility of dir"ectly 3D-printed phantoms appears warranted.

Evaluation of a laparoscopic technique for collection of serial full-thickness small intestinal biopsy specimens in standing sedated horses.

OBJECTIVE: To assess a technique for laparoscopic collection of serial full-thickness small intestinal biopsy specimens in horses. ANIMALS: 13 healthy adult horses. PROCEDURES: In the ex vivo portion of the study, sections of duodenum and jejunum obtained from 6 horses immediately after euthanasia were divided into 3 segments. Each segment was randomly assigned to the control group, the double-layer hand-sewn closure group, or the endoscopic linear stapler (ELS) group. Bursting strength and bursting wall tension were measured and compared among groups; luminal diameter reduction at the biopsy site was compared between the biopsy groups. In the in vivo portion of the study, serial full-thickness small intestinal biopsy specimens were laparoscopically collected with an ELS from the descending duodenum and distal portion of the jejunum at monthly intervals in 7 sedated, standing horses. Biopsy specimens were evaluated for suitability for histologic examination. RESULTS: Mean bursting strength and bursting wall tension were significantly lower in the ELS group than in the hand-sewn and control groups in both the duodenal and jejunal segments. Use of the hand-sewn closure technique at the biopsy site reduced luminal diameter significantly more than use of the stapling technique. In the in vivo part of the study, all 52 biopsy specimens collected during 26 laparoscopic procedures were suitable for histologic examination and no clinically important perioperative complications developed. CONCLUSIONS AND CLINICAL RELEVANCE: Laparoscopic collection of serial full-thickness small intestinal biopsy specimens with a 45-mm ELS may be an effective and safe technique for use in healthy adult experimental horses.

Biomechanical Properties of the 1.5 mm Locking Compression Plate: Comparison with the 1.5 and 2.0 mm Straight Plates in Compression and Torsion.

OBJECTIVES: The purpose was to compare the biomechanical properties of a 1.5 mm locking compression plate (1.5 LCP) to the 1.5 mm straight plate (1.5 P), 1.5 mm straight plate stacked (1.5 PSt) and 2.0 mm straight plate (2.0 P) in compression and torsion. We hypothesized that biomechanical properties of the 1.5 LCP would be equivalent to properties of the 1.5 P and would represent an alternative for the treatment of radial fractures in miniature breed dogs in which those plates would be used. MATERIALS AND METHODS: A 1 mm fracture gap model was created with a bone surrogate stabilized with a six-hole plate. Sixteen constructs were built for each of the four plate configurations. Eight constructs from each group were tested in compression to failure and eight constructs were tested in torsion to failure. RESULTS: In compression testing, the 1.5 LCP was stiffer than the 1.5 P, and had similar stiffness than the 1.5 PSt and the 2.0 P. The load at yield of the 1.5 LCP was slightly lower than the 1.5 P. In torsion, the 1.5 LCP and 1.5 P had similar stiffness, but 1.5 LCP was slightly stronger than 1.5 P. The 1.5 PSt and 2.0 P were overall superior to the 1.5 LCP but only marginally so for the 1.5 PSt. CLINICAL RELEVANCE: The 1.5 LCP can be considered biomechanically equivalent to the 1.5 P under the present experimental conditions. The use of the 1.5 LCP can be considered as an option for radial fracture repair in dogs in which a 1.5 P would have otherwise been used. The use of a locking plate to improve overall success rate, in these fractures, remains to be confirmed clinically.

Ex vivo torsional properties of a 2.5 mm veterinary interlocking nail system in canine femurs. Comparison with a 2.4 mm limited contact bone plate.

OBJECTIVE: To evaluate the torsional properties of the Targon® Vet Nail System (TVS) in small canine femurs and to compare these properties to those of the 2.4 mm LC-DCP® plates. METHODS: Thirty-six cadaveric femurs were allocated to three groups (n = 12). In all bones, points just distal to the lesser trochanter and just proximal to the fabellae were marked and a midshaft transverse osteotomy was performed. Group 1: bones were fixed with the 2.5 mm TVS with the bolts applied at the pre-identified marks. Group 2: A TVS system with 25% shorter inter-bolt distance was used. Group 3: A 7-hole 2.4 mm LC-DCP® plates were applied. All constructs were tested non-destructively for 10 cycles, followed by an acute torsion to failure. RESULTS: Torque at yield was 0.806 ± 0.183 and 0.805 ± 0.093 Nm for groups 1 and 2 and 1.737 ± 0.461 Nm for group 3. Stiffness was 0.05 ± 0.01, 0.05 ± 0.007, and 0.14 ± 0.015 Nm/° for groups 1 to 3 respectively. Maximal angular displacement under cyclic loading was 16.6° ± 2.5°, 15.6° ± 2.1°, and 7.8° ± 1.06° respectively. There was no significant difference for any of the parameters between groups 1 and 2. Both torque at yield and stiffness were significantly greater between group 3 and groups 1 and 2. CLINICAL SIGNIFICANCE: The TVS had approximately half the torsional strength and approximately 1/3 of the stiffness of the 2.4 mm bone plate. Slippage of the locking mechanism was probably the cause of the early failure. The system should be considered as a low-strength and low-stiffness system when compared to bone plates.

Development of a technique for determination of pulmonary artery pulse wave velocity in horses.

Calcification of the tunica media of the axial pulmonary arteries (PA) has been reported in a large proportion of racehorses. In humans, medial calcification is a significant cause of arterial stiffening and is implicated in the pathogenesis of cardiac, cerebral, and renal microvascular diseases. Pulse wave velocity (PWV) provides a measure of arterial stiffness. This study aimed to develop a technique to determine PA-PWV in horses and, secondarily, to investigate a potential association between PA-PWV and arterial fibro-calcification. A dual-pressure sensor catheter (PSC) was placed in the main PA of 10 sedated horses. The pressure waves were used to determine PWV along the PA, using the statistical phase offset method. Histological analysis of the PA was performed to investigate the presence of fibro-calcified lesions. The mean (±SD) PWV was 2.3 ± 0.7 m/s in the proximal PA trunk and 1.1 ± 0.1 m/s further distal (15 cm) in a main PA branch. The mean (±SD) of mean arterial pressures in the proximal PA trunk was 30.1 ± 5.2 mmHg, and 22.0 ± 6.0 mmHg further distal (15 cm) within the main PA branch. The mean (±SD) pulse pressure in the proximal PA trunk was 15.0 ± 4.7 mmHg, and 13.5 ± 3.3 mmHg further distal (15 cm) within the main PA branch. Moderate to severe lesions of the tunica media of the PAs were observed in seven horses, but a correlation with PWV could not be established yet. Pulmonary artery PWV may be determined in standing horses. The technique described may allow further investigation of the effect of calcification of large PAs in the pathogenesis of equine pulmonary circulatory disorders.NEW & NOTEWORTHY Pulmonary artery pulse wave velocity was determined safely in standing sedated horses. The technique described may allow further investigation of the effect of calcification of large pulmonary arteries in the pathogenesis of pulmonary circulatory disorders in horses.

Computed Tomographic Analysis of Ventral Atlantoaxial Optimal Safe Implantation Corridors in 27 Dogs.

Objectives Ventral atlantoaxial stabilization techniques are challenging surgical procedures in dogs. Available surgical guidelines are based upon subjective anatomical landmarks, and limited radiographic and computed tomographic data. The aims of this study were (1) to provide detailed anatomical descriptions of atlantoaxial optimal safe implantation corridors to generate objective recommendations for optimal implant placements and (2) to compare anatomical data obtained in non-affected Toy breed dogs, affected Toy breed dogs suffering from atlantoaxial instability and non-affected Beagle dogs. Methods Anatomical data were collected from a prospectively recruited population of 27 dogs using a previously validated method of optimal safe implantation corridor analysis using computed tomographic images. Results Optimal implant positions and three-dimensional numerical data were generated successfully in all cases. Anatomical landmarks could be used to generate objective definitions of optimal insertion points which were applicable across all three groups. Overall the geometrical distribution of all implant sites was similar in all three groups with a few exceptions. Clinical Significance This study provides extensive anatomical data available to facilitate surgical planning of implant placement for atlantoaxial stabilization. Our data suggest that non-affected Toy breed dogs and non-affected Beagle dogs constitute reasonable research models to study atlantoaxial stabilization constructs.