Is the Lesser Trochanter Profile a Reliable Means of Restoring Anatomic Rotation After Femur Fracture Fixation?

Abstract

Background: Restoring normal femoral rotation is an important consideration when managing femur fractures. Femoral malrotation after fixation is common and several preventive techniques have been described. Use of the lesser trochanter profile is a simple method to prevent malrotation, because the profile changes with femoral rotation, but the accuracy of this method is unclear.

Questions/purposes: The purposes of this study were (1) to report the rotational profiles of uninjured femora in an adult population; and (2) to determine if the lesser trochanter profile was associated with variability in femoral rotation.

Methods: One hundred fifty-five consecutive patients (72% female and 28% male) with a mean age of 32 years (range, 12-56 years) with a CT scanogram were retrospectively evaluated. Patients were included if CT scanograms had adequate cuts of the proximal and distal femur. Patients were excluded if they had prior hip/femur surgery or anatomic abnormalities of the proximal femur. CT scanogram measurements of femoral rotation were compared with the lesser trochanter profile (distance from the tip of the lesser trochanter to the medial cortex of the femur) measured on weightbearing AP radiographs. These measurements were made by a single fellowship-trained orthopaedic surgeon and repeated for intraobserver reliability testing. Presence of rotational differences based on sex and laterality was assessed and correlation of the difference in lesser trochanter profile to the difference in femoral rotation was determined using a coefficient of determination (r).

Results: The mean femoral rotation was 10.9° (SD ± 8.8°) of anteversion. Mean right femoral rotation was 11.0° (SD ± 8.9°) and mean left femoral rotation was 10.7° (SD ± 8.7°) with a mean difference of 0.3° (95% confidence interval [CI], -1.7° to 2.3°; p = 0.76). Males had a mean rotation of 9.4°(SD ± 7.7°) and females had a mean rotation of 11.5° (SD ± 9.1°) with a mean difference of 2.1° (95% CI, -0.1° to 4.3°; p = 0.06). Mean lesser trochanter profile was 6.6 mm (SD ± 4.0 mm). Mean right lesser trochanter profile was 6.6 mm (SD ± 3.9 mm) and mean left lesser trochanter profile was 6.5 mm (SD ± 4.0 mm) with a mean difference of 0.1 mm (-0.8 mm to 1.0 mm, p = 0.86). The lesser trochanter profile varied between the sexes; males had a mean of 8.3 mm (SD ± 3.4), and females had a mean of 5.9 mm (SD ± 4.0). The mean difference between sexes was 2.5 mm (1.5-3.4 mm; p < 0.001). The magnitude of the lesser trochanter profile measurement and degree of femoral rotation were positively correlated such that increasing measures of the lesser trochanter profile were associated with increasing amounts of femoral anteversion. The lesser trochanter profile was associated with femoral version in a linear regression model (r = 0.64; p < 0.001). Thus, 64% of the difference in femoral rotation can be explained by the difference in the lesser trochanter profile. Intraobserver reliability for both the femoral version and lesser trochanter profile was noted to be excellent with intraclass correlation coefficients of 0.94 and 0.95, respectively.

Conclusions: This study helps define the normal femoral rotation profile among adults without femoral injury or bone deformity and demonstrated no rotational differences between sexes. The lesser trochanter profile was found to be positively associated with femoral rotation. Increasing and decreasing lesser trochanter profile measurements are associated with increasing and decreasing amounts of femoral rotation, respectively.

Clinical relevance: The lesser trochanter profile can determine the position of the femur in both anteversion and retroversion, supporting its use as a method to restore preinjury femoral rotation after fracture fixation. Although some variability in the rotation between sides may exist, matching the lesser trochanter profile between injured and uninjured femora can help reestablish native rotation.

Fig. 1

A flowchart displays those patients included and excluded from the study. SCFE, Perthes, and lesser trochanter (LT) fractures were excluded from the study.

Fig. 2A-B

An example measurement of femoral rotation as determined on CT scanogram is shown. (A) An axial CT image of the pelvis was used to measure the rotation of the proximal femur (β). A line was drawn through the center of the femoral neck and an angle made relative to the horizontal plane (ψ) in a single CT cut (β = femoral neck rotation). (B) An axial CT image of the distal femur was used to measure the rotation of the distal femur (α). A tangent line was drawn across the axis of the posterior femoral condyles and an angle made relative to the horizontal plane (ψ) in that CT cut (α = distal femur rotation). The difference in these measurements is equal to femoral rotation (femoral rotation = β - α). β = Femoral neck rotation; α = distal femur rotation; ψ = horizontal plane.

Fig. 3

Example measurement of the lesser trochanter profile (X) as determined on a plain film radiograph. The lesser trochanter profile was measured from the apex of the lesser trochanter to the edge of a line drawn along the medial border of the femoral cortex. The horizontal plane (ψ) was established using a transteardrop horizontal line.

Fig. 4

Linear regression demonstrates the correlation in difference in femoral version to the difference in lesser trochanter profile across the study cohort.

Fig. 5

Total counts are noted as a distribution of femoral version differences across the study cohort.

Fig. 6A-B

Examples demonstrate symmetric and asymmetric lesser trochanter profiles. (A) An asymmetric lesser trochanter profile correlates with the patient’s asymmetric CT scanogram rotational measurements. (B) A symmetric lesser trochanter profile correlates with the patient’s symmetric CT scanogram rotational measurements.