INVESTIGATION OF BIOABSORBABLE SCREW USAGE FOR LONG-BONE FRACTURE REPAIR IN THE HORSE - INTERFRAGMENTARY COMPRESSION AND AXIAL LOAD RESPONSE IN EQUINE CADAVER LONGBONE FRACTURES

The purpose of the study was to compare biomechanical features of bioa bsorbable, self-reinforced poly-L-lactic acid (SR-PLLA) and stainless steel (ASLF) 4.5 mm cortical screws. Tests were conducted in equine ca daver third metacarpal bones in which a simulated complete and displac ed condylar fracture had been created by osteotomy. An evaluation of t he amount of interfragmental compression achieved with each screw type was performed using electrical resistance strain gauges placed in pro ximity to the osteotomy. This revealed a substantial increase in inter fragmental compression when ASIF screws were used compared to the SR-P LLA screw. A hybrid of the two screw types did however achieve adequat e interfragmental compression. Comparison of the strength of fracture fixation through response to axial loading revealed significant differ ence between use of three ASIF screws and a hybrid of one SR-PLLA and two ASIF screws (p = 0.04) or two ASIF (p = 0.01) screws alone. It app eared that the hybrid configuration did have a mechanical advantage ov er the two ASIF screw arrangement. The results indicate that the SR-PL LA screw is inferior to the stainless steel screw as a means of primar y fracture reduction in the horse. A less mechanically demanding role may yet enable usage of the bioabsorbable screws in equine fracture re pair, although they proved inadequate in this testing environment.