The Restoration of Passive Rotational Tibio-Femoral Laxity after Anterior Cruciate Ligament Reconstruction

RESEARCH ARTICLE The Restoration of Passive Rotational TibioFemoral Laxity after Anterior Cruciate Ligament Reconstruction Philippe Moewis1*, Georg N. Duda1, Tobias Jung2, Markus O. Heller3, Heide Boeth1, Bart Kaptein4, William R. Taylor5 a11111 1 Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Berlin, Germany, 2 Knee Surgery and Sports Traumatology, Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Berlin, Germany, 3 Bioengineering Research Group, University of Southhampton, Southhampton, United Kingdom, 4 Department of Orthopaedic Surgery, Biomechanics and Imaging Group, Leiden University Medical Center, Leiden, Netherlands, 5 Department of Health Sciences and Technology, Institute for Biomechanics, ETH Zürich, Zürich, Switzerland * Abstract OPEN ACCESS Citation: Moewis P, Duda GN, Jung T, Heller MO, Boeth H, Kaptein B, et al. (2016) The Restoration of Passive Rotational Tibio-Femoral Laxity after Anterior Cruciate Ligament Reconstruction. PLoS ONE 11(7): e0159600. doi:10.1371/journal.pone.0159600 Editor: John Rudan, Queen's University, CANADA Received: February 3, 2016 Accepted: June 1, 2016 Published: July 28, 2016 Copyright: © 2016 Moewis et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper. Additional information concerning study EA1/167/08 is available at the institutional database of the Charité—Universitätsmedizin Berlin and can be made available by the corresponding author. Funding: The study was supported by the European Union Seventh Framework Programme (FP7/20072013 ICT-2009.5.2MXL 248693). While the anterior cruciate ligament (ACL) is considered one of the most important ligaments for providing knee joint stability, its influence on rotational laxity is not fully understood and its role in resisting rotation at different flexion angles in vivo remains unknown. In this prospective study, we investigated the relationship between in vivo passive axial rotational laxity and knee flexion angle, as well as how they were altered with ACL injury and reconstruction. A rotometer device was developed to assess knee joint rotational laxity under controlled passive testing. An axial torque of ±2.5Nm was applied to the knee while synchronised fluoroscopic images of the tibia and femur allowed axial rotation of the bones to be accurately determined. Passive rotational laxity tests were completed in 9 patients with an untreated ACL injury and compared to measurements at 3 and 12 months after anatomical single bundle ACL reconstruction, as well as to the contralateral controls. Significant differences in rotational laxity were found between the injured and the healthy contralateral knees with internal rotation values of 8.7°±4.0° and 3.7°±1.4° (p = 0.003) at 30° of flexion and 9.3°±2.6° and 4.0°±2.0° (p = 0.001) at 90° respectively. After 3 months, the rotational laxity remained similar to the injured condition, and significantly different to the healthy knees. However, after 12 months, a considerable reduction of rotational laxity was observed towards the levels of the contralateral controls. The significantly greater laxity observed at both knee flexion angles after 3 months (but not at 12 months), suggests an initial lack of post-operative rotational stability, possibly due to reduced mechanical properties or fixation stability of the graft tissue. After 12 months, reduced levels of rotational laxity compared with the injured and 3 month conditions, both internally and externally, suggests progressive rotational stability of the reconstruction with time. Competing Interests: The authors have declared that no competing interests exist. PLOS ONE | DOI:10.1371/journal.pone.0159600 July 28, 2016 1 / 14 Restoration of Passive Rotational Tibio-Femoral Laxity Introduction Although a natural amount of passive joint laxity exists within healthy joints, excessive laxity is often a direct consequence of failure of one or more musculoskeletal structures, particularly after traumatic injury [1]. In the knee, passive laxity is primarily governed by the ligaments. While the primary function of the anterior cruciate ligament (ACL) is to stabilize against excessive tibial translation relative to the femur [2], it is also thought to play a secondary role in controlling axial rotation, particularly internally, and hence contribute towards rotational stabilization of the knee joint [3]. As a result, injuries of the ACL have a direct repercussion on knee joint laxity and kinematics, resulting in both increased anterior-posterior (A-P) tibial displacement and axial rotation [4]. Although patients with ACL rupture present passive instability or excessive laxity, some individuals are able to actively stabilize their knees during activities of daily living [5]. As a result of the altered kinematics, together with the associated prevalence of degenerative changes in the longer term [6], reconstruction of the ACL becomes the primary option for restoring normal function and kinematics of the injured knee. However, it is plausible that rotational instability after ACL reconstruction could be a contributing factor towards graft failure [7], and might also play a role in the initiation of biological and mechano-degenerative processes such as osteoarthritis (OA) [8–10]. The quest for effective reconstruction of knee rotational stability therefore represents a key challenge for surgeons [11], where an understanding of rotational laxity in healthy knees, as well as after ACL reconstruction, is clearly required. Typically, rotational laxity is assessed in the clinic using the pivot shift test [12], however this test lacks objectivity and is dependent upon the examiner’s experience [13, 14]. Although a range of devices for analysing rotational laxity have been employed, including goniometers [15], electromagnetic sensors [16, 17], light-emitting diode (LED)-markers [18], electronic sensors [19], inclinometers [20], and magnetic resonance imaging (MRI) [21, 22], these approaches are generally subject to soft tissue artefact (and thus inaccurate or over-estimate the real skeletal rotation [23]) or may be limited due to the extended periods of time required for image capture. Here, MRI approaches have been used to good effect in the comparison of axial rotation between ACL reconstructed and healthy knees, and have demonstrated a postreconstruction reduction in the axial rotational range of motion (RoM) [22], albeit only at 15° of knee flexion. On the other hand, a study using electronic sensors attached to the skin to assess tibio-femoral motion reported no significant differences between the ACL reconstructed and healthy contralateral knees [24]. These reports suggest that the outcome of ACL reconstruction (...truncated)