OBJECTIVE. Coronal tibiofemoral (TF) subluxation has generated interest in the last several years due to newfound clinical implications of its presence. However, controversy within the literature concerning how to measure and calculate coronal TF subluxation on radiographic imaging remains. The purpose of this study was to describe how coronal TF subluxation is being measured and calculated in the literature with the goal of describing a reproducible and validated technique for clinical adoption. MATERIALS AND METHODS. A PubMed literature search was performed in March 2020 according to PRISMA guidelines. The terms "tibiofemoral subluxation" and "tibial femoral subluxation" were included in the search. Criteria of interest included radiographic view and evaluation, anatomic landmarks used, and measurement validity. RESULTS. Review of relevant literature resulted in 744 articles, 16 of which met our inclusion criteria. A wide range of measuring techniques, anatomic landmarks, and radiographic views were used with varying validity. Full-limb radiographic views were the most common. Six studies measured the translation of the mechanical axes of the tibia and femur. Eight studies measured the translation of either femoral condyle in reference to the tibial plateau. Coordinate-based software with the iterative closest point algorithm was used in two studies. Whether coronal TF subluxation should be divided by tibial plateau width to account for knee size was controversial. CONCLUSION. A variety of approaches exist for diagnosing and quantifying coronal TF subluxation because of the lack of clear anatomic landmarks within the TF joint that can be used to measure coronal TF subluxation in the horizontal plane. Even when using the same anatomic landmarks, studies varied on how to measure coronal TF subluxation radiographically and whether knee size should be accounted for. Further studies are necessary to standardize (via inter- and intraobserver validation with a control group) an easy, reproducible, and minimally biased approach to measuring coronal TF subluxation on radiographic imaging. We believe our systematic review succinctly provides the necessary information to either develop such a tool or encourage future studies to compare existing techniques to find the most reliable and clinically useful approach for evaluating coronal TF subluxation.
Keywords: coronal tibiofemoral subluxation; horizontal translation; systematic review.