Time-dependent diagnostic value of pericruciate fat pad edema in arthroscopically confirmed anterior cruciate ligament rupture: A comparative MRI study.

Abstract

To evaluate temporal changes in pericruciate fat pad (PFP) edema as a secondary MRI sign of anterior cruciate ligament (ACL) rupture and to determine the diagnostic performance of secondary MRI findings in patients undergoing ACL reconstruction. This retrospective study included 188 patients who underwent primary arthroscopic ACL reconstruction with arthroscopically confirmed total ACL rupture. Six secondary MRI findings (anterior tibial translation, ACL-lateral tibial plateau angle, posterior cruciate ligament (PCL) angle, PCL line sign, PCL buckling, and PFP edema) were assessed using predefined criteria. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated. Intra- and inter-observer reliability were evaluated using intraclass correlation coefficients and Cohen's kappa. ROC analysis assessed the diagnostic performance of PFP edema relative to injury to MRI interval. All secondary findings were significantly associated with ACL rupture (p < 0.001). Overall sensitivity and specificity of PFP edema were 65.4% and 100%, respectively. With a 13-week injury-to-MRI cutoff, sensitivity increased to 85% while specificity and PPV remained 100% (NPV 78%). Other findings showed good diagnostic performance, including anterior tibial translation >5 mm (79.8%/92.5%), ACL-lateral tibial plateau angle <45°(88.8%/91.5%), PCL angle <107° (84.6%/94.5%), PCL line sign (70.2%/91.0%), and PCL buckling (72.3%/86.5%). PFP edema is a highly specific and time-dependent secondary MRI sign of ACL rupture, particularly within 13 weeks after injury, and may aid in diagnosis and estimation of injury chronicity when primary findings are inconclusive.