Introduction of 3.5mm and 4.5mm cortex screws into the equine distal sesamoid bone with the help of the VetGate Computer Assisted Surgery Systems and comparison of the results with the previously reported ones, acquired with the SurgiGATE 1.0 System – an in vitro study

The in vitro experimental study was performed to evaluate the functionality and accuracy of the VetGate Computer Assisted Surgery (CAS) System and compare the results with those achieved with the SurgiGATE System previously reported.On ten cadaveric equine limb pairs free of major phalangeal pathologies (n = 20) either a 3.5 mm or 4.5 mm cortex screw was inserted in lag fashion across a virtual midsagittal fracture of the distal sesamoid bone under real-time supervision by the VetGate CAS-System.Care was taken to avoid penetration of the distal interphalangeal joint and the navicular bursa, as well as avoid damage of the articular cartilage.The placement within the bone was perfect for all 20 screws.The results for the 3.5 mm screws were good in all aspects, whereas the screw head of the 4.5 mm screws jeopardized the edge of the articular surface of the navicular bone in 8 out of 10 cases.The difference between the screw length determined by the VetGate system during the planning phase and the actually inserted screw length was significantly smaller than with the one experienced with the SurgiGATE 1.0 CAS-System.In conclusion standard 4.5mm screws are not feasible in Thoroughbreds and Warmblood horses of average size, mainly because of the screw head that is too large (8mm), whereas 3.5mm cortex screws serve the purpose very well.The use of the 4.0mm cortex screws is preferred because this screw has the same screw head diameter as the 3.5mm cortex screw and a thicker core diameter, which makes it more resistant towards implant breakage.The latter screw was not tested, but even 4.5 mm cortex screws could be inserted without damaging any vital structure.The VetGate CAS-System allows precise screw placement at this difficult location without damaging neighboring structures.