Correction of lag screw guide pins inappropriately placed during intramedullary hip nailing

Abstract

Lag screw position is one of the most important controllable factors in trochanteric fracture fixation. However, it is sometimes difficult to handle the lag screw guide pin during intramedullary hip nailing. In this study, causes of guide pin shift and correction of malposition were investigated. The movements of guide pins during fracture fixation were traced fluoroscopically using 35 embalmed, mainly anteverted femora, angles were measured in the anteroposterior and lateral planes and necessary corrections calculated. In the proximal anteverted femur, posterior correction of an inappropriately placed guide pin in the lateral plane led to an inferior shift in the anteroposterior fluoroscopic view, and vice versa. Mean anteversion, alpha, beta, and beta' angles were 13.1 degrees (5-29 degrees ), 10.9 degrees (4-18 degrees ), 4.6 degrees (0-10 degrees ) and 4.4 degrees (0-9 degrees ), respectively. The beta' angle was directly proportional to the anteversion angle only, i.e. Y=0.27X+0.65 (R(2)=0.79), p<0.001. In the proximal anteverted femur, guide pin shift in the anteroposterior fluoroscopic view occurred during correction of pin position in the lateral plane. The amount of shift was directly related to the amount of anteversion.