A threshold value of 3.5 mm of passive anterior tibial subluxation on MRI is highly specific for complete ACL tears

Abstract

Purpose To identify and quantify passive anterior tibial subluxation on MRI using a standardized measurement protocol and determine the diagnostic threshold of subluxation for complete anterior cruciate ligament tears. Methods A retrospective case-control study was performed. Patients who underwent surgery for a complete isolated ACL tear between 2009 and 2015 were matched for age and gender to controls with an intact ligament on knee MRI. All subjects underwent 1.5 T closed field MR imaging with the same protocol. Measurements were performed on axial sequences to evaluate translation of the medial and lateral condyles compared to the tibial plateau. Each compartment was measured between the vertical tangent to the posterior femoral condyles and the most posterior part of the tibial plateau. The main criterion was global passive subluxation measurements on MRI, corresponding to mean medial and lateral compartment subluxation. The reproducibility and diagnostic value of passive subluxation were calculated. Results Sixty (30/30) subjects were included, mean age 27.1 ± 1.7 years, 20 women and 40 men. Patients had a significantly higher global passive subluxation than controls (3.3 ± 0.6 mm vs 0.6 ± 0.2 mm, respectively p < 0.00001). Reproducibility was excellent and the diagnostic value of passive subluxation for a complete ACL tear was fair. A passive subluxation threshold of 3.5 mm had a sensitivity of 55.2%, a specificity of 100% and 77.6% of well-classified subjects. ConclusionThe calculated cutoff value for global passive subluxation to identify patients with a complete ACL tear was 3.5 mm, with excellent specificity and a high positive likelihood ratio. Suboptimal clinical results following ACL reconstruction could be partially due to failure to restore an anatomical femorotibial relationship. Level of evidence III.

Value of passive anterior tibial subluxation on axial MRI in identifying anterior cruciate ligament functional deficiency in patients with advanced anteromedial osteoarthritis of the knee: a case-control study

“…However, there is still a lack of standardized or reproducible methods to evaluate ACL functional integrity before UKA. PATS on MRI has been moderately investigated for distinguishing a complete ACL tear in young patients suffered from acute knee injuries and showing a good diagnostic value in this population [ 13 – 15 ]. But in elderly patients diagnosed with advanced AMOA, the PATS, as a quantitative parameter in assessing ACL status, is little studied.…”

“…Measurements were performed on the axial plane of MRI to evaluate the translation of the tibial plateau relative to the medial and lateral femoral condyles. According to Alexandre et al [ 13 ], the most posterior points of the femoral condyles and the tibial plateau were determined using axial and sagittal sequences. A line was drawn through the posterior points of the tibial plateau, and the distance from the medial and the lateral condyles to this line was measured as medial PATS and lateral PATS, respectively (Fig.…”

“…In the setting of an acute complete ACL tear, the anterior subluxation of the tibia relative to the femur is prominent compared to that of intact ACL [ 12 , 13 ]. The quantitative parameter for assessing the degree of such subluxation is generally called the passive anterior tibial subluxation (PATS) [ 14 , 15 ].…”

“…The quantitative parameter for assessing the degree of such subluxation is generally called the passive anterior tibial subluxation (PATS) [ 14 , 15 ]. PATS measured on the axial sequence of MRI is more reliable compared with sagittal sequence, and a threshold of 3.5 mm for axial global PATS is highly specific for diagnosing a complete ACL tear [ 13 ]. However, the ability of axial PATS to assess ACL integrity in patients with AMOA is unknown for the moment.…”

Top-Ten Tips for Imaging the ACL

“…The clinical significance of exaggerated tibiofemoral translation is that it seems to be associated with increased clinical laxity of the knee joint in that patients with tibiofemoral translation on MRI have a greater feeling of clinical instability and giving way than patients without exaggerated tibiofemoral translation. [12][13][14] It is potentially feasible that patients with exaggerated tibiofemoral translation may be more suitable candidates for ACL reconstruction.…”