Biomechanical Comparison of a Closed-Loop Double Endobutton to a Lag Screw in Fixation of Posterior Malleolar Fractures

Abstract

Anteroposterior (AP) lag screw, posteroanterior (PA) lag screw, or posterior buttress plate are usually performed for posterior malleolar fixation, but the biomechanically strongest technique is unclear. The aim of our study was to biomechanically compare 3 different fixation methods for posterior malleolar fractures; AP lag screw, PA lag screw, and closed-loop double endobutton. Fracture models were created using a thin blade power saw after drawing the fracture line. The resultant fracture involved 30% of the joint on the distal tibial joint surface and extends with an angulation of approximately 50 degrees using 15 tibia composite bone samples. After anatomical reduction, fixation was achieved with 3.5 mm cortical screw in PA direction and in AP direction for group PA and AP, respectively. In Group DL, fixation was achieved with a closed-loop double endobutton (double lift loop, Orthomed, Turkey). The highest compression force to generate all displacement amounts was required for the double loop group (Group DL). The strongest fixation against compression was a double loop. The PA group was the second strongest fixation, and the AP group was the biomechanically weakest among these 3 fixation techniques. The closed-loop double endobutton technique was found biomechanically superior to anterior to posterior or posterior to anterior screw fixation techniques for posterior malleolar fracture.