Editorial Commentary: Look Out for Internal Rotational Tibial Subluxation on Magnetic Resonance Imaging as an Indicator of High-Grade Rotatory Instability in Anterior Cruciate Ligament-Deficient Knees.

Consensus indications for adding a lateral extra-articular procedure (LEAP) to an anterior cruciate ligament (ACL) reconstruction include use of hamstring autograft, hypermobility, revision surgery, and high-grade rotatory laxity (grade 3 pivot shift). Most of these indications are related to patient characteristics or surgical factors and can be determined preoperatively. However, pivot shift grading is somewhat subjective and often relies on examination under anesthesia in the operating room. There is a paucity of objective and radiological markers of high-grade rotational instability. Recent literature has found that increased internal rotational tibial subluxation (ITRS) and axial internal tibial rotation (ITRa) on knee magnetic resonance imaging are associated with high-grade rotational instability. ITRS greater than 5.5 mm and ITRa greater than 8.1° were associated with grade 2 and grade 3 pivot shift with the ITRS cutoff of 5.5 mm showing excellent specificity (86.5%) for high grade pivot shift. These measurements offer an objective marker of rotatory instability that we should factor into our preoperative decision-making on when to add LEAP to ACL reconstruction.