A Retrospective Comparison of ACL Tear and Mucoid Degeneration MRI Findings and an Emphasis on Evaluating of ACL, Blumensaat, and PCL Angles

Abstract

To determine MRI findings that can differentiate anterior cruciate ligament (ACL) tears from mucoid degeneration. Material and Methods: Thirty-seven patients with complete ACL tears and 43 with ACL mucoid degeneration were included in this study. Discontinuity, the abnormal signal intensity of the ACL on fat-saturated-PD weighted images, contusions, a deep lateral femoral notch, anterior tibial translation, uncovered posterior horn of the lateral meniscus, a celery stalk appearance, thickening, ganglion cysts, intraosseous cysts, the ACL, Blumensaat, and posterior cruciate ligament (PCL) angles were evaluated. Optimum threshold values, sensitivity, specificity, and 95% CIs for the angles were calculated to predict the tear. Results: The prevalence of the significant findings in a tear versus mucoid degeneration, respectively, was as follows: discontinuity (97% vs. 0%, p < 0.001), contusions (65% vs. 2%, p < 0.001), the deep lateral femoral notch (22% vs. 0%, p = 0.001), anterior tibial translation (70% vs. 14%, p < 0.001), uncovered the lateral meniscus (46% vs. 7%, p < 0.001), a celery stalk appearance (0% vs. 66%, p < 0.001), thickening (19% vs. 100%, p < 0.001), ganglion cysts (14% vs. 70%, p < 0.001), and intraosseous cysts (8% vs. 63%, p < 0.001). Threshold values of ACL, Blumensaat, and PCL angles to predict the tear were ≤36° (78% sensitivity, 91% specificity), >11° (84%, 81%), and ≤96° (65%, 91%), respectively. Conclusion: A celery stalk appearance in the mucoid degeneration and discontinuity in an ACL tear are important in the differential diagnosis. ACL, Blumensaat, and PCL angles can be helpful in settings of diagnostic uncertainty.

Ancillary findings in distinguishing between anterior cruciate ligament mucoid degeneration and sprain on MRI: a practical approach

“…We found different results in previous studies on this subject. While Kwee et al (12) found bone marrow lesion more prevalent in ACL MD, in the study by Celikyay et al (19) on the distinction between ACL MD and tear, bone contusions were found more frequent (65% vs. 2%) in the tear group.…”

“…In our study, although no significant difference was found in bone marrow edema, intraosseous cyst formation in the tibial plateau was found to be an independent risk factor for ACL MD by increasing the probability of ACL MD 41.2 times. It was reported that intraosseous cyst may accompany ACL MD and is detected more frequently in ACL MD than tear cases (11,19). This may be due to the extension of myxoid material into the bone at the ligament attachment sites or the development of cystic changes due to degeneration.…”

“…Increased posterior tibial slope has been shown to be associated with ACL MD and ACL tears (8,16,35–37). In addition, the criteria of ACL angle ≤36°, Blummensaat angle >11°, and PCL angle ≤96° were found to be helpful in the diagnosis of tear in the differentiation of ACL MD and tears (19). Yigman and Toprak found that the prevalence of ACL MD increased in patients with trochlear dysplasia (38).…”

“…Although the frequency of ACL MD varies depending on the patient population and MRI magnet strength in different studies, it has been reported to be in the range of 1-13.8% (11)(12)(13)(14)(15). There are studies related to knee joint structural characteristics such as intercondylar notch morphology, posterior tibial slope, and ACL, and Blumensaat and posterior cruciate ligament (PCL) angles (16)(17)(18)(19). Both ACL MD and ACL sprain have been associated with altered biomechanics as a result of aging and osteoarthritis (12,20,21).…”

Steep posterior slope of the medial tibial plateau and anterior cruciate ligament degeneration contribute to medial meniscus posterior root tears in young patients

“…Collagen fiber degeneration was described as the appearance of high‐signal‐intensity ACL with low‐signal‐intensity fibers running parallel to its long axis (celery stalk sign) (Fig. 3b) [5, 28]. ACL degeneration was considered positive if one or both of these findings were present.…”