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TDK conference 2022

Ex vivo study of P1 sagittal fracture fixation with two different screw implants in cadaver horses
Mergl Balázs Márk - year 5
University of Veterinary Medicine Budapest, Department and Clinic of Equine Medicine
Supervisor: Dr. Izing Simon


In equine medicine, surgical procedures and implants have significantly developed in the last few decades. In this paper, we will deal with tensile screw fracture treatment. The horse fracture treatment most often follows human and small animal principles, so in general, innovation also comes from these areas. Therefore, absorbable screws, which are already used in human medicine, also raise the possibility of their use in equine medicine. Among other things, these screws reduce the number of surgical procedures since the implant does not need to be removed later, thus reducing the cost of surgery and the risk of possible septic complications.

This study aimed to compare the biomechanical properties of the INION FreedomScrew™and the metal cortical (Synthes) screw's pullout strength. During the experiment, an artificially formed sagittal fracture of the P1 bone of 20 anterior limbs of 10 cadaver horses was drilled and fixed with ten metal and ten absorbable screws. During the execution of the experiment, we randomly selected which of the two P1 bones belonging to a particular horse should use metal and which should use a bioabsorbable cortical screw. The parameters of all 20 screws used were the same regarding thread angle, major diameter (4.5mm), and pitch; only the material was different. In all cases, the screws were inserted by surgeon Dr.Izing Simon, following the rules of the cortical screw in a lag fashion. Each specimen was embedded in 10mm epoxy resin to make it suitable for the test. In the interest of reliable pressure testing, we used the corresponding metacarpus for each P1 bone as a wedge. Biomechanical pressure tests were observed with the same equipment each time; the Zwickk Z250 is a computer-controlled universal material testing machine for tensile tests. During the test, steadily increasing pressure was applied to the metacarpal wedge until a 20% drop was detectable in terms of resistance, which we considered a fracture.

Our experiment measured and investigated the maximum applied force (N), deformations, and the extent of fracture opening (mm) during compression. Based on our results, the bioabsorbable screws could withstand a large amount of resistance. However, based on the data collected, their use looks more promising for foals or interventions subjected to a lower load. At the same time, these implants reduce the number of surgical procedures since there is no need to remove implants later, the risk of septic complications or irritation of permanently inserted screws by their absorption over time. These listed benefits are essential for surgical interventions in equine medicine, especially for foals and sports horses. Overall, we can say that with this examination, it can be proved that absorbable screws have an encouraging chance of being used mainly for the treatment of partial or minor fractures in foals or transcortical drilling of cysts.

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