Abstract
Objectives:
Routine, non-contrast knee MRIs were used to assess the prevalence of popliteal artery branching variants. Distances from typical instrumentation in sports medicine operations to the aberrant anteiror tibial artery were measured
Methods:
A retrospective series of 236 consecutive knee MRIs obtained at a single academic center between March 2022 and May 2022 was compiled. Exclusion criteria included substantial artifact impairing interpretation of the imaging, lesion with mass effect on posterior structures, fracture with significant displacement of the distal femur or tibial plateau, or meniscal injury with displacement of the meniscus. Popliteal artery branching was classified as described by Kim et. al. Measurements were obtained using the imaging software Sectra (Sectra, Linkoping, Sweden). The lateral meniscus was measured in the axial plane at the level of the meniscus. Points representing the posterior-most aspects of the root and posterior horn were selected and these were measured to the popliteal artery. The HTO measurement was performed using the axial plane. A 3D rendering of the MRI was created using the imaging software in Sectra. The axial plane was then reoriented to mimic the oblique cut of the osteotomy. The cut was selected at the level of the proximal extent of the osteotomy just proximal to the fibular head roughly 1.5 cm from the plateau. A point along the posterior tibial cortex closest to the vessel during the procedure was selected as long as it was medial to the lateral most extent of the osteotomy (1 cm from the lateral cortex). The distance from this point to the nearest point of the popliteal artery or its branch was measured. Lastly the proximal tibial tunnel of the posterolateral corner (PLC) reconstruction was measured in the axial plane at a level just above the fibular head. The tunnel was set to have a radius of 5mm to approximate a 10 mm graft tunnel. Statistics were calculated with Excel (Microsoft, Redmond, Washington).
Results:
200 patients with 222 knee MRIs were obtained. The average age was 31.5 years, and 51% were male. 48% of images were of the right knee. 92/222 of the knees did not have branching of the anterior tibial artery within the imaging study, which was presumed to represent a distal takeoff. There were 8 (3.6%) of type II popliteal artery variants off which 7 (3.15%) were type IIA-2 with the anterior tibial artery anterior to the popliteus. Amongst the type I anterior tibial arteries, average distance from vessel to lateral meniscus posterior horn and root was 9.7 (+/-2.7) mm and 15.7 (+/-3.0) mm, respectively. The edge of the tibial tunnel for PLC reconstruction was 14.5 (4.0) mm and distance from saw cut of HTO was 7.9 (2.8) mm. For type II-A2, these values were 7.7 (+/-3.0) mm, 11.1 (+/-3.6) mm, 11.8 (+/-4.8) mm, and 0.6 (+/-0.3) mm, respectively. Type II-A2 anterior tibial arteries were signifcantly closer to the lateral meniscus posterior root (p=0.015) and the cut for high tibial osteotomy (p<0.01) when compared to type 1 vessels. Type II-A2 variants were not closer to the posterior horn of the lateral meniscus (p=0.13) or tibial tunnel for PLC reconstruction (p=0.19) when compared to type 1 vessels.
Conclusions:
Standard MRIs are sufficient for identification of aberrant anterior tibial artery branching patterns and useful for surgical planning around patient specific anatomy. One in thirty patients in our study had proximal type II anterior tibial artery branching anterior to the popliteus. In particular, instrumentation around the proximal poster tibial cortex and lateral meniscus root are at increased risk.This is especially important with the rise of outpatient surgery centers, it is crucial to understand patient-specific anatomy to minimize the risk of vascular injury.
