Comparison of wiring techniques for bone fracture fixation in total hip arthroplasty

The objective of this study was to investigate the effect of cerclage wire position and determine the number of wires necessary to prevent crack opening and stem subsidence following a proximal femoral fracture in cementless total hip arthroplasty. A cementless femoral stem one size larger than the templated size was inserted into each femur to initiate a proximal crack. A cerclage wire was wrapped around the fracture in one of two orientations: 1) parallel to the osteotomy (PO) and 2) normal to the fracture line (NF). The femur was compressed to a load of 890 N, 1780 N and 2670 N while crack opening and stem subsidence were measured. A second cerclage wire was placed parallel to NF wire and inferior to the lesser trochanter and a third wire was placed 1 cm distal and parallel to the second wire. The loading was repeated again. The mechanical evaluation of stem subsidence were verified by various computer simulations even using four wires. We have found that placement of the cerclage wires normal to the fracture line prevents stem subsidence and crack opening better than placement of the wires parallel to the osteotomy. Three cerclage wires, placed normal to the fracture line at three locations: 1) adjacent to the superior of the lesser trochanter, 2) adjacent to the inferior of the lesser trochanter and 3) 10 mm distal to the bottom of the lesser trochanter were necessary to achieve stability under higher loads.