A BIOMECHANICAL STUDY OF 3 WIRING TECHNIQUES FOR CERCLAGE-PLATING

Transverse fractures at the distal tip of a well-fixed femoral prosthe sis are difficult to stabilize using plates and screws due to the pres ence of the underlying intramedullary stem. The attachment of plates u sing cerclage wires obviates the need for screws, but the stability pr ovided by cerclage plating is a clinical concern, In this study we com pared the mechanical performance of three wire-cerclage plating techni ques: (a) simple cerclage (each wire wrapped around the bone and plate once); (b) double cerclage (each wire wrapped around the bone and pla te twice); and (c) a new method that used small stainless steel insert s that fit into the plate holes and permit the direct coupling of the cerclage wires to the plate. To compare the performance of the three f ixation constructs, synthetic femora were osteotomized, stabilized wit h a wire cerclage plating technique, and subjected to monotonic and cy clic loading using a Materials Testing System (Minneapolis, MN) servo- hydraulic testing system. The performance of each construct was evalua ted using seven different mechanical parameters (four monotonic, three cyclic). Double cerclage performed significantly better than did simp le cerclage for three of the seven mechanical parameters. The insert t echnique performed significantly better than did the simple and double cerclage techniques for all seven of the measured mechanical paramete rs. For both monotonic and cyclic loading, the use of inserts resulted in an improvement in fixation strength and stability in comparison wi th conventional simple and double cerclage plating techniques. The ins ert technique shows promise in the treatment of this difficult type of fracture at the distal tip of a well-fixed femoral prosthesis.