title: The PCL index is correlated with the control of rotational kinematics that is achieved after anatomic anterior cruciate ligament reconstruction.
abstract: BACKGROUND
  The posterior cruciate ligament (PCL) index quantifies the curvature of the PCL seen on magnetic resonance imaging (MRI) that is caused by a change in tibiofemoral alignment in the anterior cruciate ligament (ACL)-deficient knee. It has been proposed that the PCL index may be useful in assessing the success of ACL reconstruction (ACLR). Hypothesis/
  
  
  OBJECTIVE
  The purpose of this study was to test if the PCL index is predictive of in vivo rotational kinematics and joint laxity measures in knees of patients after single-bundle ACLR. The hypothesis was that the PCL index is predictive of rotational knee kinematics and objective laxity scores.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  At a mean of 18.1 months postoperatively, the PCL index was defined on MRI in 16 patients prospectively followed up after anatomic single-bundle ACLR and in 16 matched controls. The patients were evaluated with 3-dimensional motion analysis during (1) descending and pivoting as well as (2) landing and pivoting tasks. The side-to-side difference in tibial rotation range of motion between the reconstructed knee and the contralateral intact knee was calculated. The side-to-side difference in anterior tibial translation was measured with a KT-1000 arthrometer. Linear regression models were used with the PCL index as a predictor of the side-to-side difference in tibial rotation for each task and the side-to-side difference in anterior tibial translation.
  
  
  RESULTS
  The PCL index of the reconstructed knees was significantly lower compared with that of the control knees (P < .001). The index was predictive of the side-to-side difference in tibial rotation during both tasks (R (2) = 0.472 and 0.477, P = .003), with a lower index being indicative of increased rotational laxity. It was not predictive of anterior tibial translation (at 134 N: R (2) = 0.13, P = .17; at maximum force: R (2) = 0.009, P = .726).
  
  
  CONCLUSIONS
  The PCL index after anatomic single-bundle ACLR using a bone-patellar tendon-bone graft is predictive of rotational kinematics during in vivo dynamic pivoting activities. The results show that the PCL index is correlated with the postoperative ability to control rotational kinematics of the knee joint.
  
  
  CONCLUSIONS
  This study provides evidence regarding the interplay between restoration of the native ACL's anatomy and the PCL's appearance and suggests that the effective restoration of tibiofemoral alignment after ACLR that is reflected in the PCL index translates into better functional outcomes as measured by tibial rotation during pivoting activities.
authors: Franceska Zampeli, Orthopaedic Sports Medicine Center, Department of Orthopaedic Surgery, University of Ioannina, Papanastasiou, Arta, 47100, Greece. frangeska_zam@yahoo.gr.
authors: Franceska
authors: F
authors: Zampeli
authors: Aikaterini
authors: A
authors: Ntoulia
authors: Dimitrios
authors: D
authors: Giotis
authors: Ristanis
authors: R
authors: Stavros
authors: Grigorios
authors: G
authors: Mitsionis
authors: Evangelos
authors: E
authors: Pappas
authors: Anastasios D
authors: AD
authors: Georgoulis
mesh_terms: D000293:Adolescent; D000328:Adult; D059549:Anterior Cruciate Ligament Reconstruction; D053587:Arthrometry, Articular; D001696:Biomechanical Phenomena / Q000502:physiology; D050376:Bone-Patellar Tendon-Bone Grafting; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007593:Joint Instability / Q000473:pathology / Q000503:physiopathology; D007719:Knee Joint / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D016014:Linear Models; D008279:Magnetic Resonance Imaging; D008297:Male; D016119:Posterior Cruciate Ligament / Q000473:pathology*; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D013977:Tibia / Q000473:pathology / Q000503:physiopathology*; D055815:Young Adult
keywords: MRI; anterior cruciate ligament (ACL) reconstruction; motion analysis; posterior cruciate ligament (PCL) index; tibial rotation