Anthropometric Factors on Safe Distances between Popliteal Vessels to the Femur for Cerclage Wiring of the Distal Femoral Fracture: A Magnetic Resonance Imaging Study

Abstract

Background and Objectives: The proximity of the popliteal vessels in the distal femur may increase the risk of iatrogenic vascular injury during cerclage wiring. In this study, the closest location and distance of the popliteal vessels to the femur was examined using magnetic resonance imaging (MRI). The associations between anthropometric factors and the distance that would guide the placement of wires safely during surgery were also identified. Materials and Methods: We reviewed adult knee magnetic resonance images and recorded: (1) the relation and the shortest horizontal distance (d-H) from the femoral cortex to the popliteal vessels in axial images and (2) the vertical distance (d-V) from the adductor tubercle to the axial level of the d-H values in coronal images. The effects of anthropometric factors (sex, age, body height, body weight, body mass index, thigh circumference, femoral length and femoral width) on these distances were analysed. Results: Analysis of 206 knee magnetic resonance images revealed that the closet locations of popliteal vessels were at the posteromedial aspect of the femur. The d-H and d-V were 7.38 ± 3.22 mm and 57.01 ± 11.14 mm, respectively, and were both shorter in women than in men (p < 0.001). Multivariate analysis identified thigh circumference and femoral length as the most influential factors for the d-H and d-V, respectively (p < 0.001). Linear regression demonstrated a strong positive linear correlation between the thigh circumference and the d-H and between the femoral length and the d-V (Pearson's r = 0.891 and 0.806, respectively (p < 0.001)). Conclusions: The closet location and distance of the popliteal vessels to the femur provide useful information for wire placement during distal femoral fracture surgery while minimising the risk of vascular injury. Given that patients with a smaller thigh circumference and a shorter femoral length are more likely to have a smaller d-H and a shorter d-V, respectively, cautious measures should be taken in such cases.

Keywords: cerclage wiring; distal femoral fracture; magnetic resonance imaging; popliteal vessel; vascular injury.

Figure 1

Magnetic resonance images demonstrating the views used for measuring the distances from the popliteal vessels to the femur: (a) in the axial views, the closest distance (d-H) between the popliteal vessels and the femoral cortex; (b) in the coronal views, the distance (d-V) between the adductor tubercle (AT) and the axial level of “d-H”; (c) in the axial views, the posterior condyles axis (PCA) in the femur used as a reference line (0°); (d) in the axial views, the posterior half of the femur divided into eight sections labelled from A to H and from posteromedial to posterolateral.

Figure 2

The example of the measurements in magnetic resonance images of a 28-year-old male: (a) the closest distance (d-H) between the popliteal vessels and the femoral cortex is 1.22 mm, and the position of the popliteal vessels adjacent to the femoral cortex is section C; (b) the distance (d-V) between the AT and the axial level of “d-H” is 66.98 mm.

Figure 3

The example of the measurements in magnetic resonance images of a 56-year-old female: (a) the closest distance (d-H) between the popliteal vessels to the femoral cortex is 14.65 mm, and the position of the popliteal vessels adjacent to femoral cortex is section C; (b) the distance (d-V) between the AT and the axial level of “d-H” is 41.08 mm.

Figure 4

(a) The simple linear regression model describing the relationship between thigh circumference and d-H; (b) the simple linear regression model describing the relationship between femur length and d-V.