Description
Aim
The aim of this study is to evaluate whether ultrasound evidence of lateral meniscus extrusion (ME) can accurately predict the presence of lateral meniscus posterior root tears (LMPRTs).
Methods
A cohort of 24 patients with complete anterior cruciate ligament (ACL) tears was prospectively evaluated using ultrasound in order to detect the presence of lateral ME. For each patient, the lateral ME was recorded in supine position at 30° of knee flexion and in bipedal weightbearing position at full knee extension, both in the injured and uninjured side. The following data were collected for each patient: 1) ME in supine position of the injured side, 2) ME in weightbearing position of the uninjured side, 3) the difference of ME between injured and uninjured side in supine position, 4) the difference of ME between injured and uninjured side in weightbearing position, as well as 4) the difference of ME between weightbearing and supine position of the injured side. The prevalence of LMPRTs was confirmed during arthroscopic evaluation. A Receiver Operating Characteristic (ROC) curve analysis was constructed for each finding, determining the diagnostic performance in terms of sensitivity and specificity. Statistically significant differences among patients with isolated ACL tears, patients with concomitant LMPRTs and patients with other lateral meniscus tears were calculated using the ANOVA one way test. A p <0.05 was defined as statistically significant.
Results
Five patients (20.8%) had a concomitant LMPRT, while 4 patients (16.7%) had other types of concomitant lateral meniscus tears. All the evaluated figures were found to have a poor diagnostic performance according to the ROC curve analysis. Indeed, patients with LMPRT presented no significantly greater extrusion when compared with patients with isolated ACL tears. Patients with other concomitant lateral meniscus tears had greater meniscus extrusion both in supine (p=0.0043) and in weightbearing position (0.0003) when compared to isolated ACL tear. At the same time, patients with other lateral meniscus tears had greater meniscus extrusion than patients with LMPRTs in weightbearing position (p=0.0017) but not in supine position (p>0.05). The difference of meniscus extrusion between weightbearing and supine position did not significantly disclose among the three evaluated groups.
Conclusion
Ultrasound evidence of lateral meniscus extrusion should alert the surgeon to the possibility of associated lateral meniscus tears, but it is not a sufficiently specific sign for diagnosis of LMPRTs.
