Use of Lesser Trochanter Profile as a Rotational Alignment Guide in Intramedullary Nailing for Femoral Shaft Fracture.

BACKGROUND

Malrotation after nailing of femoral shaft fractures occurs in about 25% of cases. It can cause substantial functional problems. The lesser trochanter (LT) profile has been used to assess rotational alignment. However, the extent to which the LT profile is symmetrical between limbs, whether the LT profile varies as a function of age or sex, and the efficacy of the LT profile technique remain unknown. The purpose of this study was to determine if there was a significant side-to-side length difference in the LT profile (LTD) according to age and sex.

METHODS

We attempted to determine the amount of medial prominence of the lesser trochanter relative to the medial cortex of the femoral shaft (the LT profile) using 3-dimensional computed tomography (3D-CT) images of normal femora obtained bilaterally (366 subjects) in anatomic positions. We also compared the left and right sides to determine the amount of natural asymmetry by age and sex. In addition, we compared the side-to-side difference in the LT version with the LTD to determine whether the LTD represented the difference in femoral rotation.

RESULTS

The LTD was <4 mm (meaning an LT version difference of <10°) in 83% of the subjects, but was ≥4 mm (an LT version difference of ≥10°) in 17%. Subset analysis demonstrated that the differences were greatest in women >70 years of age. The largest LTD (both sexes) was observed in individuals over 70 years of age (2.62 ± 1.37 mm, compared with <55 years: 1.55 ± 1.36 mm and 55 to 70 years: 2.27 ± 1.70 mm). There was no significant difference between sexes in the under-70 age groups. However, the LTD was significantly greater in women over 70 years than in men over 70 years (3.10 ± 1.42 versus 2.41 ± 1.30 mm).

CONCLUSIONS

Since the LTD demonstrated side-to-side symmetry within 4 mm, or 10° of rotation, in 83% of all subjects, we consider the LT profile to be useful as a guide to assess rotational reduction clinically. However, surgeons should recognize that, in 17% of cases, using this technique could result in malrotation of ≥10°. The rate of malrotation may be even higher in women over 70, for whom supplemental techniques to ensure correct rotation may be appropriate.