Poster 360: Long-Leg Lateral Monopodal Stress Radiographs for the Assessment of Anterior Tibial Translation with Anterior Cruciate Ligament Injury: A Prospective Study

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Objectives: The purpose of this study is to use standing anterior cruciate ligament (ACL) stress radiographs to evaluate how posterior tibial slope (PTS) compared to anterior tibial translation (ATT) in an injured knee. A secondary purpose was to determine how posterior tibial slope (PTS) affects ATT side-to-side difference. Our hypothesis was that anterior tibial translation would be higher in the injured knee compared to the contralateral side and posterior tibial slope will have a positive effect on anterior tibial translation. Methods: A retrospective study of ACL stress radiographs was assessed from patients with primary ACL reconstructions with no concomitant ligamentous injury between January 2023 and August 2023. Institutional Review Board approval was obtained. The bilateral radiographs were long-leg lateral “stress views” which was accomplished by monopodal weight-bearing in 20° flexion and are a part of the initial patient workup. Stress radiographs were utilized to measure the anterior tibial translation (ATT) and posterior tibial slope (PTS) for both knees. Differences in ATT between knees and the correlation between PTS and ATT was assessed via paired t-tests and regression analysis. Results: A final cohort of 39 patients were analyzed using preoperative ACL stress radiographs. The results reported a significant regression with positive correlation between posterior tibial slope (PTS) and anterior tibial translation for the injured knee using both anatomic (Figure 1, P<0.001, R2=0.302) and mechanical (Figure 2, P=0.038, R2=0.111) PTS measurements. Anatomic PTS measurements are better at predicting ATT for the injured knee compared to mechanical PTS measurements. Conclusions: The findings of this study report a significant regression with a positive correlation between posterior tibial slope (PTS) and anterior tibial translation (ATT) of the injured knee, with anatomic PTS measurements being a better predictor of ATT than mechanical PTS measurements. This indicates an important relationship between PTS and ATT with higher PTRS predicting higher ATT.