Avoiding rotational malalignment after fractures of the femur by using the profile of the lesser trochanter: an in vitro study

Introduction Intramedullary (IM) nailing has become the preferred method of treatment for femoral shaft fractures in adults. Rotational malalignment is an important complication, established during operation. The incidence of rotational malalignment (>= 15 degrees) has been reported to be between 20% and 30%. It might be avoided intra-operatively by using quantitative imaging techniques, with the profile of the contralateral lesser trochanter serving as a reference. Materials and methods With the help of a C-arm image intensifier five surgeons tried to determine the neutral state of ten prepared cadaver femora. They could only look at the C- arm screen and were blinded to the actual femur. Per observer three measurements were done per femur. The first measurement ( method I) was done without a reference, while the second ( method II) used a reference image of the femur in a neutral state. The third method ( method III) added a lesser trochanter quantifying computer program. After positioning of the femur, the difference in rotational state compared with the neutral state was measured with an inclinometer. Results Without reference, malrotations up to 27 degrees were found. Methods II and III proved to be significantly better ( p< 0.0001). These two methods showed malrotation of 2.2 degrees ( +/- 1.5 degrees) and 2.3 degrees ( +/- 1.7 degrees), respectively. External or internal malrotation occurred with all three methods equally frequently. No difference was found between observers. Conclusions Using the contralateral lesser trochanter as a reference is an accurate method to minimize malrotation of a femur. Quantifying the profile of the lesser trochanter with computer assistance did not improve these results. Clinical results in the future still have to support these in vitro findings.