How to optimize the use of MRI in anatomic ACL reconstruction

Abstract

Purpose: Magnetic resonance imaging (MRI) is the most current diagnostic imaging procedure for suspected ACL injuries. It is an accurate, highly sensitive and specific tool for the diagnosis of ACL tears, graft tears and associated injuries. However, it can also be used for various other aspects of anatomic ACL reconstruction.

Methods: Special sequences as the oblique sagittal plane should be obtained from a parallel line to the lateral epicondyle, ensuring a proper visualization of both bundles of the ACL. Another special set of images, the oblique-coronal sequence, allows for the ACL long-axis evaluation. The coronal-oblique sequence increases the sensitivity and specificity of diagnosing isolated AM or PL bundle injuries and also helps to visualize the proximal insertion of the bundles for haemorrhage and rupture.

Results: Quantitative measurements can be taken from a proper MRI protocol, so as to determine the rupture pattern; measure insertion site size, inclination angle and autograft size; and evaluate for post-operative complications. These parameters help surgeons to objectively decide for a better graft and technique for an individualized approach and to evaluate the anatomic placement of the graft.

Conclusions: MRI can be used in different ways, serving as a very valuable tool in anatomic ACL reconstruction. Special protocols can provide accurate visualization of the double-bundle anatomy. Objective parameters to aid in pre-operative decisions and graft's anatomic placement evaluation can be also extracted from the MR images.

Fig. 1

a Sagittal oblique view of the intact ACL. b Coronal-oblique view of the intact ACL

Fig. 2

a MRI showing absence of PL bundle with AM bundle intact. b Arthroscopic picture confirming the absence of the PL bundle. c PL bundle augmentation

Fig. 3

a MRI showing AM bundle isolated tear. b Six months later, MRI showing complete healing

Fig. 4

a Sagittal MRI cut best showing the ACL attachment to the tibia; b the most anterior and most posterior fibres attaching the tibia are connected by a line that represents the insertion site size

Fig. 5

a MRI sagittal cut best showing tibial and femoral insertion sites is chosen; b tibial insertion site is highlighted; c femoral inserion site is highlighted; d the distance between the mid-portion of the tibial and femoral insertion sites are connected and measured to know ACL length

Fig. 6

a Sagittal MRI showing the ACL and physeal scar; b line drawn over the physeal scar; c Line a, parallel to the physeal scar; d half of the line a; e and f Line b is drawn proximally to the line a in half of its distance; g and h half of the distance of Lines a and b are used as parameter to create Line c representing the long axis of the tibia; i tibial Horizontal Line; j. inclination Angle of the ACL

Fig. 7

The quadriceps and patellar tendon thicknesses are measured 15 mm proximal and distal, respectively, from the patellar poles