Diagnostic potential of the Sagittal-Oblique MRI technique for Injuries of the Anterior Cruciate Ligament in the Knee
Background. MRI examination of the anterior cruciate ligament (ACL) of the knee gives valuable information for conventional, physiatrist and/or arthroscopic micro-invasive treatment. Three planar MRI examination and 3D reconstructions are highly precise in the analysis of the intra and periarticular structures, with the exception of anterior cruciate ligament. Direct contact with the roof of the intercondylar fossa (in the full extension during the examination) and its specific orientation makes visualization of ACL diagnostically problematic.
Methods. The study goal was to draw a comparison between Sagittal-Oblique MR technique of ACL imaging versus flexion MR technique of ACL imaging and, versus ACL imaging obtained with standard MR protocol of the knee. We analysed diagnostic value of data related to ACL trauma, especially detection of partial tears, number of images per technique showing the whole ACL, duration of applied additional protocols, ergonomics and reproducibility of examination.
In this prospective study we included 149 patients who were sent to MRI examination in Centre for Diagnostic Radiology in Clinical Centre of Montenegro during the 12 month period, due to trauma of knee soft tissue structures.
Results. Sensitivity of the standard MRI protocol of the knee, with respect to both additional techniques is identical in detection of a complete ACL rupture. Both the Flexion MRI technique and the Sagittal-Oblique technique are obviously more valid in diagnosing the partial rupture of ACL, although without proven high statistical difference (p = 0.05, t = 1.744, p<0.081, df=148).
The frequency of direct presentation of the partial rupture of ACL using Standard MR protocol of 47.89% was less effective by 30.02% than the direct presentation using Flexion technique, which is a very high statistical significance, on the level of probability p = 0.001 ( t = 3.875, p<0.001, df=155).
Also, higher frequency of direct presentation of ruptured ACL of 34.67% using Sagittal-Oblique technique compared to standard knee MR examination was statistically very significant (t = 4.781, p<0.001, df=155). The frequency of direct presentation of ruptured ACL using Sagittal-Oblique technique, in relation to Flexion technique was without statistical significance (t = 0.083, p> 0.65).
Conclusions. Sagittal-Oblique technique provides a higher number of radiologically valid tomograms that show the whole course of ACL. The necessity of repositioning the patient to perform Flexion technique reduces reproducibility in possible subsequent examinations. Shorter scan time of 1.9 minutes required for Sagittal-Oblique technique (1 minute 54 seconds) compared to the duration of Flexion technique is statistically very significant difference (t = 20.243, p<0.001).Additional Sagittal-Oblique technique is superior for valid presentation of ACL partial rupture. It should be performed in addition to the standard MR protocol of the knee.