| Anterior cruciate ligament (ACL),which attaches to the medial plane of the lateral femoral condyle and the bone plane before the tibal intercondyle apophysis ,has certain angles to the sagital plane and coronary plane . It plays an important role in restraining the tibial from excessive anterior displacement and it also can control the rotatory stabilities of the knee joint . The knee joint loses its stabilities with ACL tears.With refined tissue resolving power and high space resolving power MRI play an important role in the diagnosis of ACL tears.In some patients 1 or 2 clear and full-lengh MR images of ACL can present in the section near medial sagtial plane.It shows a dark low signal intensity zonal structure ,which is about 1 centimeter. In coronary and axial plane it shows dark low signal intensity sections with clear inserted sites.The routine observation of ACL is mainly depend on sagtial plane with reference to the coronary and axial plane. In clinical practice the posterior cruciate ligament (PCL) usually can show its full-length in 1 to 2 consecutive sections,which is easily to identify. On the contrary ACL sometimes can not show its full-lengh in a single section, whicn may improve the difficulty to identify it. Furthermore the diagnostic ratio of partial ACL tears and dated ACL tears is still low. So it is needed to do something to improve the MR imaging of ACL.This study was undertaken to find new resonable scan method to improve the MR imaging of ACL.Methods: We measured the length , thickness ,width and the angle to the coronary and sagital planes of ACL in 6 Chinese aldult cadavers and the measurments in the MR images had performed before that .We randomly measured the length , thickness and the angle to the coronary plane of ACL in 120 patients' MR images . Based on the angle to the coronary we measured we set up an oblique coronary scan method . We measured the length , width and the angle to the sagital plane in 60 oblique coronary scan MR images . Then we compared the data we gained directly in cadavers with data we gained in MR images in stastics and the anlyse also did . And we prospectively used the additonal oblique coronary scan method in 39 patient ,who also underwent arthroscopic examination or treatment.The anlyses were committed . Results:1. MR imaging is a very good method to collect the data of knee joint. The data of thickness and the angle gained in MR images approach to those gained directly in cadaver . There are no sigficant differences between them (p>0.05) .Both the length and width approach to the latter too , however there is an obvious trend of being smaller (p<0.01).2. In oblique sagital scan MR images the angle to the coronary plane is different for woman and man . They are respective 35.4(2.5°,36.4(2.5°,0.010.05. Because the angles are comparatively certain we can commit scan in certain angles in order to parallel the axis of ACL. The additional oblique coronary ,which commit scan at a certain angle to the coronary plane, is a very good method to show ACL.3. The sensitivity, specificity and accuracy values for MR imaging of ACL using additional oblique coronary scan were as followed :92.3% sensitivity,76.9% specificity and 87.2% accuracy . This study confirmed that MR imaging of the knee was highly sensitive and accurate. There was a no significant difference in the concordance rates between surgical and MRI findings. The additional oblique coronary scan is a new method and can be an important complementarity for routine MR imaging .Conclusions: MR imaging can be a good way in the use of collecting the data of the knee joint . In the posture of knee joint extension for Chinese adult the angle to the coronary plane is relatively certain. The additional oblique coronary scan at that certain angle is a new method and can be an important complementarity for routine MR imaging... |
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