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

The objective of this study mas to investigate the effect of cerclage wire position and determine the number of wires necessary to prevent crack openi ng 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 mere measured. A second cerclage wire was place d parallel to NF wire and inferior to the lesser trochanter and a third wir e was placed 1 cm distal and parallel to the second mire. The loading was r epeated again. The mechanical evaluation of stem subsidence were verified b y various computer simulations even using four wires. We have found that pl acement of the cerclage wires normal to the fracture line prevents stem sub sidence and crack opening better than placement of the mires parallel to th e osteotomy. Three cerclage mires, placed normal to the fracture line at th ree locations: 1) adjacent to the superior of the lesser trochanter, 2) adj acent to the inferior of the lesser trochanter and 3) 10 mm distal to the b ottom of the lesser trochanter were necessary to achieve stability under hi gher loads.