Safe Sawing Conditions to Prevent Popliteal Artery Injury in Various Distal Femoral Osteotomies: Three-dimensional Simulation Analysis

Abstract

Background: Distal femoral osteotomy (DFO) use is increasing in popularity, and popliteal artery injury during DFO can be devastating.

Purpose: To determine the safe sawing angles in DFO to prevent popliteal artery injury by analyzing the artery's course and the distances from key structures within the osteotomy plane.

Study design: Descriptive laboratory study.

Methods: Three-dimensional images of the healthy popliteal artery and femur were reconstructed from computed tomography angiography scans of 27 patients, and medial and lateral closing-wedge DFO (MCW-DFO and LCW-DFO) was simulated. Specifically, after formation of the osteotomy plane that passes the designated hinge point and primary cutting start point, the plane was rotated by 5° and 10° to create the 0°, 5°, and 10° osteotomy planes. Minimal distances to the popliteal artery from the posterior cortex and posterior cortical line (dPA-PC, dPA-PCL) were measured in each osteotomy plane. A distance <10 mm was defined as "at risk." Frontal safe sawing index (FSSI), maximal safe sawing angles (MSSAs), and maximal safe osteotomy angles (MSOAs) were analyzed to evaluate the safety margin.

Results: The FSSI was significantly higher in MCW-DFO than LCW-DFO across all osteotomy planes (P < .001). In MCW-DFO, FSSI decreased with higher-degree upper cuts (P < .001), while in LCW-DFO, it was maintained. The mean minimal distance to the popliteal artery from the posterior cortex ranged from 13 to 14 mm in all DFO simulations. MCW-DFO and LCW-DFO showed a decrease in dPA-PC with higher-degree cuts (P < .001), and dPA-PCL was consistently shorter than dPA-PC (P < .001). The at-risk ratio of dPA-PCL was higher than that of dPA-PC in all conditions, favoring cutting along the normal curvature of the cortex over cutting straight. The MSSA for MCW-DFO was around 5°, with no significant variation between osteotomy planes. LCW-DFO had a smaller safety margin when compared with MCW-DFO, considering the 95% confidence interval of MSSAs. However, MSOA values were higher in LCW-DFO than MCW-DFO (P < .001). The dPA-PC was correlated with height, weight, body mass index, and transepicondylar distance (P < .05).

Conclusion/clinical relevance: The safety margin during osteotomies in various DFO scenarios may vary. When DFO is performed, it is essential to be aware of safety tips related to the course of the popliteal artery and the normal curvature of the femoral posterior cortex.