Abstract
BackgroundThe diagnosis of incomplete acute and chronic posterior cruciate ligament (PCL) tears can be challenging with conventional magnetic resonance (MR) imaging, particularly for injuries in which the ligament appears continuous as occurs with chronic PCL tears that have scarred in continuity. Quantitative mapping from MR imaging may provide additional useful diagnostic information in these cases. The purpose of this study was to assess the feasibility of quantifying transverse relaxation time (T2) mapping values at 3 Tesla (T) in a prospectively enrolled patient cohort with chronic PCL tears.MethodsTwelve subjects with acute or chronic functionally torn PCL, confirmed on clinical exam and posterior knee stress radiographs (with 8 mm or more of increased posterior tibial translation), were enrolled prospectively over a span of 4 years (age: 28–52 years, injury occurred 2 weeks to 15 years prior). Unilateral knee MR images were acquired at 3 T, including a multi-echo spin-echo T2 mapping scan in the sagittal plane. For the six subjects with a continuous PCL on MR imaging the PCL was manually segmented and divided into proximal, mid and distal thirds. Summary statistics for T2 values in each third of the ligament were compiled.ResultsAcross the six patient subjects with a continuous ligament, the mean T2 for the entire PCL was 36 ± 9 ms, with the highest T2 values found in the proximal third (proximal: 41 ms, mid 30 ms, distal 37 ms). The T2 values for the entire PCL and for the proximal third subregion were higher than those recently published for asymptomatic volunteers (entire posterior cruciate ligament: 31 ± 5 ms, proximal: 30 ms, mid: 29 ms, distal: 37 ms) with similar methodology.ConclusionMean T2 values were quantified for acute and chronic PCL tears in this prospectively enrolled patient cohort and were higher than those reported for asymptomatic volunteers. This novel approach of using quantitative mapping to highlight injured areas of the posterior cruciate ligament has potential to provide additional diagnostic information in the challenging case of a suspected posterior cruciate ligament tear which appears continuous, including chronic tears that have scarred in continuity and may appear intact on conventional magnetic resonance imaging.
Highlights
The diagnosis of incomplete acute and chronic posterior cruciate ligament (PCL) tears can be challenging with conventional magnetic resonance (MR) imaging, for injuries in which the ligament appears continuous as occurs with chronic PCL tears that have scarred in continuity
The regional mean Transverse relaxation time (T2) values in the PCL patients were higher than previously reported for the uninjured PCL in asymptomatic volunteers using the same T2 mapping protocol in the entire PCL and the proximal subregion (Wilson et al, 2016)
While studies on a larger cohort are needed for further evaluation, the present results demonstrate the potential for T2 mapping to be a useful biomarker in the diagnosis and localization of a chronic PCL tear with ligament continuity
Summary
The diagnosis of incomplete acute and chronic posterior cruciate ligament (PCL) tears can be challenging with conventional magnetic resonance (MR) imaging, for injuries in which the ligament appears continuous as occurs with chronic PCL tears that have scarred in continuity. For chronic PCL injuries, the ligament may scar in continuity and produce an intact-appearing yet insufficient/lax ligament, complicating diagnosis with conventional MR imaging and resulting in poor sensitivity for chronic PCL tears (DePhillipo et al, 2018; Servant et al, 2004). This outcome has been identified for acute PCL injuries, with authors reporting a high incidence of cases in which the PCL appeared continuous as a single structure on conventional MR imaging following an acute tear (Akisue, Kurosaka, Yoshiya, Kuroda, and Mizuno, 2011; Rodriguez et al, 2008)
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