Lateral meniscal slope negatively affects post-operative anterior tibial translation at 1 year after primary anterior cruciate ligament reconstruction.

PURPOSE: The aim of this study was to assess the correlation between posterior tibial slope and meniscal slope over postoperative anterior tibial translation during the first 18 months after primary anterior cruciate ligament (ACL) reconstruction. The main hypothesis was that PTS and MS would be positively correlated with post-operative ATT-SSD after ACL reconstruction. METHODS: Patients (28 males and 15 females) with confirmed ACL tears were selected from an in-house registry and included if they were over 16 years old, had primary ACL-reconstruction and healthy contralateral knee. Patients meeting one of the following criteria were excluded: previous knee surgeries, intraarticular fractures, associated ligamentous lesions, previous or concomitant meniscectomy or extraarticular procedures. Lateral posterior tibial slope, medial posterior tibial slope, lateral meniscal slope and medial meniscal slope were measured using preoperative MRIs. The side-to-side-difference in anterior tibial translation was evaluated 9-18 months postoperatively. RESULTS: Forty-three patients were included, (28 males/15 females; mean age 25 +/- 8 years). Mean postoperative anterior tibial translation was 1.0 +/- 1.1 mm at a mean time of 12 +/- 1 months. Mean slope values were: lateral posterior tibial slope 4.7 degrees +/- 2.2 degrees , medial posterior tibial slope 4.0 degrees +/- 2.8 degrees , lateral meniscal slope 3.0 degrees +/- 2.2 degrees and medial meniscal slope 2.0 degrees +/- 2.8 degrees . The anterior tibial translation was significantly correlated with lateral meniscal slope (r = 0.63; p < 0.01). For each 1 degrees increase in lateral meniscal slope, a 0.3 mm 95% CI [0.2, 0.4] (p < 0.01) increase in anterior tibial translation was observed. A lateral meniscal slope greater or equal to 4.0 degrees was estimated as optimal threshold for increased risk of abnormal side-to-side difference in postoperative anterior tibial translation (>/= 1.2 mm). CONCLUSION: The lateral meniscal slope was positively correlated to side-to-side difference in anterior tibial translation after primary ACL reconstruction. A lateral meniscal slope greater or equal to 4.0 degrees was detected as threshold for an increased risk of abnormal side-to-side difference in postoperative anterior tibial translation in patients who underwent primary ACL reconstruction. This confirms that soft tissue slopes have an impact on the outcomes after reconstructive surgery. Level of evidence III.