Gervásio Mikami, MD
Terms: knee, injury, snapping, anterior cruciate ligament.
Abbreviations: ACL = anterior cruciate ligament, PCL = posterior cruciate ligament, ML = lateral meniscus, MRI = magnetic resonance imaging.
PURPOSE: To study the value of MRI combined with dynamic study of stress femorotibial for the accuracy of indirect sign of the tibial anterior translational and exposure of the posterior horn of the lateral meniscus.
MATERIALS AND METHODS: We studied 135 patients (140 knees) aged 12-72 years who underwent MRI scans of the knee and subsequently were submitted to arthroscopy or were monitoring 18 months after the date of the examination. We evaluated the previous translation of the tibia and exposure of the posterior horn of the lateral meniscus compared the images with the knee in a neutral position and during the implementation of stress femorotibial.
RESULTS: There were 47 injuries and 93 of ACL ligaments intact. The sensitivities and specificities of the signs of anterior drawer was 62% and 75% respectively and the exposure of the lateral meniscus was 72% and 70% respectively. When used both indirect signs while the values obtained were 76% for sensitivity and 82% for specificity. The accuracy of these signals was 71% for the drawer front and exposure of the lateral meniscus and 56% for both signals simultaneously.
CONCLUSION: The maneuver of stress femorotibial increases the sensitivity of indirect signs, with the tibial anterior translational and exposure of the posterior horn of the lateral meniscus in the diagnosis of the anterior cruciate ligament injury.
The anterior cruciate ligament (ACL) presents oblique path in the knee, leading to the lateral femoral condyle and inserting in the anterior portion of the spine Tibialis. Also has two bands, an anterior-medial and posterior-lateral and other presents intrinsic signal larger than the posterior cruciate ligament (PCL).
Magnetic resonance imaging (MRI) is the best non-invasive method to evaluate the ACL. The sensitivity of the method varies from 92 to 94% and specificity is between 95 and 100% (6). The ACL injuries can be diagnosed through direct and indirect signs. The direct signs include complete or partial disruption or change in tone and the contours of the ligament.
When there is no direct signs of injury or when they are inconclusive, the indirect signs may be useful in the evaluation of ACL injury. These indirect signs are: loss of orientation of the ACL, verticalization of the posterior cruciate ligament (PCL), change the line of the PCL or the curvature of the ligament, increasing the depth of the lateral femoral sulcus, lesion of the medial collateral ligament, bone contusion, translation previous tibia and exposure of the posterior horn of the lateral meniscus (3).
These indirect signs can be used for diagnosis of ACL injury, even when this ligament can not be seen. The earlier translation of the tibia and exposure of the posterior horn of the lateral meniscus have the same diagnostic value, because the show anterior dislocation of the lateral tibial plateau in relation to the lateral femoral condyle (2).
The combination of the tibial anterior translational and bone contusion, has a sensitivity of 82% and specificity of 90% in acute injuries (2).
Approximately 30% of patients with chronic ACL injury may be apparent continuity, the presence of tissue fibrocicatricial with low signal, which can be wrongly interpreted as a full ligament (5).
The ACL prevents the full translation of the tibia earlier. If the ACL is ruptured or weak, there is anterior dislocation of the tibia on the femur, which can be demonstrated clinically with the previous drawer test and Lachman. The earlier translation of the tibia can be measured, and abnormal when there is a translation of more than 5 or 7 mm. This signal has high specificity (91%) but low sensitivity (41%), when used as a reference the distance of at least 7 mm of anterior dislocation of the tibia (1).
It is a sign of low specificity, there is a need to increase the signal through a dynamic assessment, that is combining MR with the maneuvers used in physical examination, as the test of Lachman and drawer.
Purpose:
Studying the value of MRI combined with dynamic study of stress femorotibial for the accuracy of indirect sign of the tibial anterior translational and exposure of the posterior horn of the lateral meniscus.
Materials and methods:
We studied prospectivamente135 patients (140 knees) aged between 12 and 72 years, with 92 males and 43 females, who underwent MRI scans of the knee in the period from February 2006 to April 2007 and subsequently were submitted to arthroscopy or were monitoring 18 months after the date of the examination. The MRI examinations were performed on the equipment 1.5T (Gyroscan Inter 1.5T Software Release 11, Philips Medical Systems, Best, Netherlands).
All patients were performed the following sequences in the normal position (rest), without stress femorotibial: Sagital, coronal and axial turbo spin-echo (TSE), with and without fat suppression. The following parameters were used: FOV of 160-180 mm, echo time of 10 to 50 ms, time to recurrence of 500 to 2300 ms, matrix of 512 x 512 and a cutoff thickness of 3.5 mm gap of 1, 0 mm.
At the end of the examination, after detailed guidance to patients about the procedure, they were subjected to a traction device on the knee (photos 1 to 7), placing a rigid support under the proximal tibia and applying a force of leverage in the distal tibia, which determines the tibial anterior drawer, keeping fixed the patella and femur against the base, simulating an anterior drawer test (force of approximately 9 to 15 kg). Coils were used without flex-average or small, is acquiring images with the sequence of turbo spin-echo in the sagittal plane, similar to the sequence at rest.
Later images were analyzed in the workstation using the OsiriX Imaging Software version 3.2, by an experienced radiologist, who measured the distance in the anteroposterior plane between two vertical lines, a tangential contour the back of the lateral femoral condyle and the other tangential contour later the lateral tibial plateau and also the extent of exposure of the posterior horn of the lateral meniscus.
Figure 1: Plank support the knee with strips for fixing.
Figure 2. Plank with the reels syn small and medium-flex.
Figure 3. Positioning the patient on board, with a base under the proximal tibia.
Figure 4. Positioning the patient and placing the coils in the knee. Side view.
Figure 5. Positioning the patient and placing the coils in the knee. Frontal view.
Figure 6. Positioning the patient, with the coils and strips for fixing the thigh and leg in the distal the traction, making lever mechanism. Side view.
Figure 7. Positioning the patient, with the coils and strips for fixing the thigh and leg in the distal the traction, making lever mechanism. Frontal view.
Results:
Of the 140 magnetic resonance imaging of the knees examined, the direct signs indicate complete rupture of the ligament in 11 (eleven) examinations (7.8%). Of these, all showed the difference in distance between the femoral condyle and tibial plateau before and after application of traction device, larger than 5.0 mm (drawer positive) and nine of these eleven (81.8%) showed less difference greater than 7.0 mm (Figure 8). There was partial exposure of the posterior horn of the lateral meniscus after the operation of stress in 10 of 11 (90.9%) exams (Figure 9).
Of the total of 140 tests, 25 (17.8%) examinations showed the ligament integrity preserved through direct signs, and in 23 (92.0%) examinations of the 25 examinations, the difference in distance between the femoral condyle and tibial plateau before and after application of traction device, was equal to or less than 4.0 mm (negative drawer) and two (8.0%) examinations had this difference of 5.0 mm. None of the 25 tests showed exposure of the lateral meniscus after the operation of stress.
The total number of ligaments with a change of 104 was the MRI examinations. Of these 104 tests, 41 (39.4%) examinations showed positive drawer (difference equal to or greater than 5.0 mm) and 9 (8.6%) had positive drawer with a difference equal to or greater than 7.0 mm. Sixty-three tests (60.6%) had negative drawer (difference less than 5.0 mm) and, of these 104 tests, 52 (50.0%) had partial exposure of the lateral meniscus and the other 50.0% This had negative sign. Twenty-seven (27) of these 104 tests (26.0%) had both positive signals simultaneously and 44 (42.3%) examinations showed the two negative signals simultaneously, totaling 71 (68.3%) patients with both signals concordant.
All patients were followed for a period of at least 18 months after the test. Of the 11 patients with direct signs of rupture, seven underwent arthroscopy for the reconstruction of the ACL and four, despite the surgical indication conduct were conservative.
Of the 104 tests that had direct signs of injury or doubtful with a change of the LCA, 36 (34.6%) examinations had confirmation of ligament damage to the arthroscopy. Of these 36 examinations, 18 (50.0%) had indirect signs of positive drawer, 24 (66.7%) had exposure of the posterior horn of the lateral meniscus and 15 (41.7%) had both positive signs.
Of the remaining 78 examinations with integrity of the ACL, 65 (62.5%) had negative sign of the drawer, 52 (66.7%) had exposure of the lateral meniscus negative and 36 (45.3%) had both negative signals.
Table 1. Correlation between positive and negative in relation to the finding of arthroscopy of all the 140 tests of the study.
Table 2. Values of sensitivity (S), specificity (E), positive predictive value (PPV), negative predictive value (NPV) and Accuracy (%) obtained in the study of 140 tests.
Figure 8. Patient with complete rupture of the ACL, with positive drawer of 7.0 mm.
Figure 9. Patient with complete rupture of the ACL, with partial exposure of the posterior horn of the lateral meniscus in sequence with stress femorotibial (picture left) compared to the sequence without stress (picture right). This patient shows signs of positive meniscus drawer and exposure simultaneously.
Discussion:
The purpose of this study to assess the potential for indirect signs of ACL injury, as the sign of the drawer and previous exposure of the posterior horn of the lateral meniscus, through the use of a traction device, simulating the maneuvers of the physical examination and appliances as the KT-1000, was reached. There was increased sensitivity of these signs, but with slight reduction of specificity in comparison with the studies without the use of this device (1).
There was a limitation of the impossibility of accurate measurement of the intensity of force applied to the test of stress during the acquisition of sequences of RM. These MRI scans of 140 with application of traction device of the knee were performed by a group of technicians and nursing assistants, (at least 10 different business), so with a possible and probable variability of application of forces between these professionals.
We were in this study, male and female, athletes and non-athletes, finally, as a range of physical biotypes that in many cases it was found some difficulty in traction mainly in patients with hypertrophied muscles or with a certain degree of protection antálgica, as in athletes High-performance and with acute injuries respectively.
The evaluation of the anterior cruciate ligament injuries by using Magnetic Resonance femorotibial the operation of stress, increases the sensitivity of indirect signs (the tibial anterior translational and exposure of the posterior horn of the lateral meniscus), compared with previous studies that evaluated these signs, without the stress of maneuvering femorotibial.
We believe that the evaluation of LCA through this maneuver of stress femorotibial can offer not only anatomical details of the ligament, but also a functional, as is often the ligament may present an apparent morphological continuity, especially in those cases of chronic injuries, where around 30% of the MRI examinations can demonstrate this false continuity (5).
There is a need to improve the device femorotibial traction, so it can be applied using special coils for the study of the knee, in which the parameters of force applied are objective and measurable, moreover, it is easily managed and professional installation for any paramedic specialist in the area and apply to any biotype of the patient.
Our group is tweaking the device to pull femorotibial, and even necessary, detailed studies with application of force with varying degrees of intensity, to learn about the strength needed to better study these indirect signs of ACL injury for each group of patients, divided by sex, by the time of the episode history of sprain (whether acute or chronic injury) and degrees of development of the muscles around the knee of the patient (athletes and non athletes). Still, further studies are needed to assess the applicability of this feature in patients with ligament grafts, after the ACL reconstruction.
References:
1. Gentile, A. Anterior cruciate ligament Loom: Indirect Signs at MR Imaging.
2. Brands, EA. MR Imaging of Anterior cruciate ligament Injury: Independent Value of Primary and Secondary Signs.
3. Robertson, PL. Anterior cruciate ligament Tears: Evaluation of Multiple Signs with MR Imaging.
4. Vahey, TN. Previous translocation of the Tibia at MR Imaging: A Sign of Secondary Anterior cruciate ligament tear.
5. Vahey, TN. Acute and Chronic Tears of the Anterior cruciate ligament: Differential features at MR Imaging.
6. Ha, TPT. Anterior cruciate ligament Injury: Fast Spin-Echo MR Imaging with Arthroscopic Correlation in 217 Examinations.
7. Rijke, AM. Stress Examination of the cruciate Ligaments: The Radiologic Lachman Test.
Gervásio Mikami, MD
Radiologist
gmikami@proimagem.biz
gmikami@proimagem.biz
