The geometric triangle relationship between the Blumensaat line and tibial plateau may be an auxiliary indicator for diagnosing and evaluating anterior cruciate ligament injuries.

PURPOSE: To study whether the geometric triangle relationship between the Blumensaat line and tibial plateau may be an auxiliary indicator for diagnosing and evaluating anterior cruciate ligament (ACL) injuries to improve the diagnostic accuracy.

METHODS

This is a retrospective self-controlled study. Patients with unilateral ACL injuries who were diagnosed by arthroscopy and received ACL reconstruction in Qingdao Municipal Hospital from January 2023 to August 2023 were recruited. Inclusion criteria were patients aged 15 - 60 years with MRI-confirmed unilateral ACL injury without concomitant knee ligament or soft tissue injuries (e.g., collateral ligaments, meniscus, posterior cruciate ligament, or cartilage), arthroscopically verified and reconstructed, having a Kellgren-Lawrence grade of knee osteoarthritis ≤1, and who provided informed consent to participate. Exclusion criteria included patients with MRI images blurry for measurement, a history of ACL reconstructive surgery, or an open ACL injury. Preoperative MRI images of affected knees and healthy knees were collected separately for the ACL injury group and the control group. In these MRI images, the most anterior point, the last point, and the midpoint of the Blumensaat line were defined as point C, point D, and point E, respectively. The turning point of the anterior margin and the posterior margin of the tibial plateau were defined as point A and point B, respectively. The intersection of the DC extension line and the AB line was defined as point C'. Based on these points, ∠DAB, ∠CEB, ∠DC'B, and ∠CDB were established. Analyzed the intraclass correlation coefficients to assess the reproducibility of measurement. Compared the differences between the above-mentioned angles and calculated the area under the receiver operating characteristic curve to evaluate the diagnostic efficacy.

RESULTS

Sixty-three patients were evaluated, and 40 of them were included in the study. For ∠CDB, ∠DC'B, ∠CEB, and ∠DAB, the intra-group and inter-group intraclass correlation coefficients were all above 0.80, indicating good reproducibility. Compared to the control group, the ∠CDB, ∠CEB, and ∠DAB of the ACL injury group were decreased significantly (p < 0.001). ∠DAB may be an optimal indicator for diagnosing and evaluating ACL injuries, with an area under the curve of 0.825, a cutoff value of 42.2°, a sensitivity of 0.825, and a specificity of 0.800.

CONCLUSION

The geometric triangle relationship between the Blumensaat line and the tibial plateau on MRI images, particularly ∠DAB, may serve as an auxiliary indicator for diagnosing and evaluating ACL injuries, thereby improving diagnostic accuracy.