Large lateral tibial slope and lateral-to-medial slope difference are risk factors for poorer clinical outcomes after posterolateral meniscus root tear repair in anterior cruciate ligament reconstruction

(2022) 23:247 Wong et al. BMC Musculoskeletal Disorders https://doi.org/10.1186/s12891-022-05174-3 Open Access RESEARCH Large lateral tibial slope and lateralto-medial slope difference are risk factors for poorer clinical outcomes after posterolateral meniscus root tear repair in anterior cruciate ligament reconstruction Cham Kit Wong1,2†, Gene Chi Wai Man1†, Xin He1, Jonathan Patrick Ng1,2, Alex Wing Hung Ng3, Michael Tim Yun Ong1* and Patrick Shu Hang Yung1 Abstract Background: Meniscus root tear is an uncommon but detrimental injury of the knee. Hoop stress is lost during meniscus root tear, which can lead to excessive tibiofemoral contact pressure and early development of osteoarthritis. Posterolateral meniscus root tears (PLRT) are more commonly associated with anterior cruciate ligament (ACL) tears. As the lateral compartment is less congruent than the medial compartment, it is more susceptible to a shearing force, which is increased in the ACL-deficient knee. In accordance with the compressive axial load, the increase in the tibial slope would generate a greater shearing force. The additional lateral compartment mobility caused by ACL tear should be reduced after ACL reconstruction (ACLR). However, there is a lack of evidence to conclude that ACLR can sufficiently limit the effect of large tibial slope (LTS) on the healing after PLRT repair. This study aimed to evaluate whether a steep LTS would be a risk factor for poorer clinical outcomes after PLRT repair concomitant with ACLR. Methods: In this retrospective study, a chart review was conducted to identify patients with concomitant unilateral primary ACLR and PLRT repair. Patients with a partial tear or healed tear were excluded. Postoperative MRI and clinical assessments were performed at a mean follow up of 35 months. MRI data was used to measure the LTS, medial tibial slope (MTS), coronal tibial slope (CTS), the lateral-to-medial slope difference (LTS-MTS) and meniscus healing and extrusion. Functional outcomes were evaluated by patient-reported outcomes (International Knee Documentation Committee [IKDC], Lysholm and Tegner scores) and KT-1000 arthrometer assessment. Interobserver reproducibility was assessed by two reviewers. Results: Twenty-five patients were identified for the analysis. Patients with larger LTS and larger LTS-MTS differences were shown to be correlated with poorer IKDC scores after surgery (R = -0.472, p = 0.017 and R = -0.429, p = 0.032, respectively). Herein, patients with LTS ≥ 6° or LTS-MTS ≥ 3° demonstrated poorer IKDC scores. *Correspondence: † Cham Kit Wong and Gene Chi Wai Man contributed equally to this manuscript. 1 Department of Orthopaedics and Traumatology, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, SAR, China Full list of author information is available at the end of the article © The Author(s) 2022. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativeco mmons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Wong et al. BMC Musculoskeletal Disorders (2022) 23:247 Page 2 of 11 Conclusion: A large LTS (≥ 6°) and a large difference of LTS-MTS (≥ 3°) were shown to be risk factors for poorer functional and radiological outcomes for PLRT repair in patients after ACLR. Clinically, closer monitoring and a more stringent rehabilitation plan for patients with LTS ≥ 6° or LTS-MTS ≥ 3° would be recommended. Keywords: Meniscus root tear, Anterior cruciate ligament, Lateral tibial slope, Meniscal extrusion, Posterolateral meniscus root tear, Functional outcomes Background Meniscus root tears are defined as tears that are located within 1 cm of the meniscus insertion or as avulsion of the insertion site [1]. Although less common than meniscal body tears and frequently unrecognized, it can occur in 0.8 to 15% of knee injuries, with a higher incidence associated with an anterior cruciate ligament (ACL) injury [2–4]. Posterolateral meniscus root tears (PLRT) are more common in patients with ACL tears, which occur 10.3 times more likely than posteromedial meniscus root tears (PMRT) [5]. A meniscus root tear is biomechanically comparable to a total meniscectomy as both would lead to compromised hoop stresses. This further results in the decreased tibiofemoral contact area and increased contact pressures in the involved compartment [6, 7], which may eventually lead to the early development of osteoarthritis [8–10]. An intact lateral meniscus is an important secondary stabilizer of ACLdeficient knee under pivot shift loading, whereas PLRT can further increase rotational instability to promote the onset and progression of osteoarthritis [11]. Moreover, the lateral compartment was found to be more susceptible to shearing force. As shown in a previous study, the ACL-deficient knee would cause a significant increase in both anterior tibial translation and internal tibial rotation at a low knee flexion angle [12]. The lateral compartment is less congruent than the medial compartment, which can result in a greater degree of anterior tibial translation. In accordance with the compressive axial load, the increase in the tibial slope would generate a greater shearing force. Based on Kolbe et al’s finding, it was demonstrated that a steep lateral tibial slope (LTS) and lateral-to-medial slope difference are risk factors for concomitant PLRT in patients with ACL injuries [13]. However, the association of these risk factors with the poorer outcome after PLRT repair concomitant with anterior cruciate ligament reconstruction (ACLR) remains to be elucidated. Ideally, the stability of the injured knee is expected to be largely restored after ACLR and lateral compartmental mobility caused by ACL tear would be reduced. However, there is no conclusive evidence to support that ACLR is sufficient to limit the effect of large LTS on clinical outcomes after PLRT repair concomitant with ACLR. Herein, this study aims to evaluate whether a large LTS is a risk factor for poorer outcomes after PLRT repair concomitant with ACLR. We hypothesized that (...truncated)