Musculoskeletal joint, MR, Imaging sequences
I. S. Lee, Y. S. Song, J. W. Song; Busan/KR
Magnetic resonance imaging (MRI) is a widely used imaging modality providing information about the natural structure and injuries of the anterior cruciate ligament (ACL) (1).
Anatomic and embryologic studies show that the native ACL consists of two distinct functional bundles,
termed the anteromedial (AM) and posterolateral (PL) bundles,
based on their tibial insertions(2-4).
The ability to reliably and accurately detect AM and PL bundles on MR images is of particular interest.
The use of additional oblique planes of view for the evaluation of AM and PL bundles offers a potential means of improving evaluations,
even using low field strength magnets(5).
In this study,
we evaluated AM and PL bundles separately using oblique coronal images.
The differentiation of partial and complete tears is important because this can influence patient management and prognosis (6,
several authors (8,
9) have suggested that standard or oblique MRI slices are not sufficiently accurate to satisfactorily differentiate complete and partial tears.
chronic tears may have potentially confusing appearances due to bridging fibrosis,
which resembles the normal ACL,
although acute tears can be accurately differentiated from intact ligaments (10-12).
On the other hands,
a complete ACL tear in those with established knee osteoarthritis may arise from mechanisms that differ from those of acute ACL tears in younger persons.
Reactive bone formation in the intercondylar notch in osteoarthritic knees causes the notch to narrow and reduce in height.
This can cause damage to the ACL due to the shear forces generated during flexion and extension (13,
Although not as common or as widely studied as complete tears of the ACL,
partial ACL tears are substantial injuries that commonly progress to complete tears and resultant symptomatic knee laxity within 1 year of initial injury (6).
Therefore we undertook to investigate the statuses of AM and PL bundles including partial and complete tears,
using standard T2-weighted sequences and by T2* mapping in the oblique coronal plane in osteoarthritic knee joints.
the effective T2 shortened by phase dispersion from both main and local magnetic field inhomogeneities,
captures fast-T2 relaxations (T2* < 10 ms) that reflect spin-spin interactions between protons bound to collagen and degree of collagen fibril-alignment (15).
Similar to T2,
T2* describes the transverse relaxation of tissues.
However T2* is always shorter than T2.
T2* may provide us with different information about tissues than T2 or T1ρ (16).
T2* mapping has been used for the evaluation of cartilage,
we considered that could be beneficial for determineing the severities of ligament disruption and degeneration in patients with a partial ACL tear.
microscopic evidence of ACL degeneration is not well documented in the literature.
the purpose of this study was to investigate the efficacy of T2* mapping for the evaluation of ACL status in osteoarthritic knee joints,
and to compare this with oblique coronal T2-weighted imaging (WI) and with respect to pathologic and operative results.