2025 ISAKOS Biennial Congress Paper
Increased Lateral Tibial Slope is Correlated with Increased Baseline Tibial Position in Intact Knees and Increased Side to Side Anterior Tibial Translation on ACL Stress Radiographs for Knees with ACL Tears
Luke V. Tollefson, BS, Edina, MN UNITED STATES
Jace Robert Otremba, BSc, Fargo, ND UNITED STATES
Claire Knowlan, BS, Omaha, Nebraska UNITED STATES
Nicholas Kennedy, MD, Yakima, WA UNITED STATES
Christopher M. Larson, MD, Edina, MN UNITED STATES
Robert F. LaPrade, MD, PhD, Edina, MN UNITED STATES
Twin Cities Orthopedics, Edina, MN, UNITED STATES
FDA Status Not Applicable
Summary
This study found a significant positive correlation between posterior tibial slope (PTS) and the baseline tibial position (BTP) in ACL-intact knees and for side-to-side differences (SSD) in anterior tibial translation (ATT) in ACL injured knees.
Abstract
Background
Stress radiographs are highly accessible and can provide additional diagnostic information to assess anterior cruciate ligament (ACL) and ACL graft integrity. The degree of preoperative anterior tibial translation (ATT) may be useful in guiding treatment for judging if additional treatments, such as an anterolateral complex (ALC) augmentation, may be necessary.
Purpose
The purpose was to evaluate the effect of posterior tibial slope (PTS) on baseline tibial position (BTP) and side-to-side differences (SSD) in ATT. A secondary purpose was to perform subgroup analysis for patients with PTS ≥12° or <12°, as well as for acute versus chronic ACL tears. The hypothesis was that increased PTS would lead to increased BTP and SSD in ATT.
Methods
A retrospective, IRB approved analysis of consecutive patients with primary ACL and ACL graft tears were assessed between March 2023 and March 2024. Bilateral “ACL stress views” were obtained by single leg weight-bearing in 20° of knee flexion and assessed by two observers. The BTP and ATT were measured using a perpendicular line drawn between the posterior margins of the lateral femoral condyle and the lateral tibial plateau. Measurements of lateral PTS were assessed by the anatomic tibial axis. Acute tears were defined as tears <6 weeks from injury and chronic tears >6 weeks from injury or ACL graft tears. Statistical analysis using linear regression and t-tests was used.
Results
Seventy-two patients were analyzed using ACL stress radiographs. The average age of the patients was 25.7±10.6 years and there were 31 females (43%). There was a significant positive correlation between increased PTS and increased BTP for the ACL-intact knees (P<<0.001, r=0.476) with an increase of 0.67 mm of BTP for every degree increase of PTS. There was a significant increase in the SSD in ATT of 1.73 mm with a positive correlation between increased PTS and increased SSD in ATT of ACL-deficient knees (p<0.001, r=0.397) with a 0.52 mm increase in SSD in ATT for every degree increase of PTS. Subgroup analysis reported that ACL-injured knees with a PTS ≥12° had a significantly increased SSD in ATT of 3.28 mm (SD=4.50) compared to those with PTS <12° (mean=0.43 mm, SD=3.51) (p=0.004). Additionally, the chronic group had significantly increased SSD in ATT of 3.76 mm (SD=3.90) compared to patients in the acute group with a SSD in ATT of -0.19 mm (SD=3.60) (p<0.001). The average ICC between reviewers was 0.96.
Conclusions
This study found a significant positive correlation between PTS and the BTP in ACL-intact knees, and for SSD in ATT between ACL-injured and ACL-intact knees. While primary ACL tears with a PTS <12° had < 0.5 mm of increased ATT, the SSD in ATT was significantly increased for ACL-injured knees with a PTS ≥12° and for chronic ACL tears. The increased ATT associated with an increased PTS ≥12° or for chronic cases may have implications for the addition of an ALC augmentation procedure during an ACLR, while acute ACL tears with a PTS <12° may be less likely to need an ALC procedure.