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 (> or = 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.