Injuries to the Kaplan fibers complex (KFC) are not routinely assessed in the anterior cruciate ligament (ACL)-deficient knee using preoperative magnetic resonance imaging (MRI). As injuries to the KFC lead to anterolateral rotatory instability (ALRI) in the ACL-deficient knee, preoperative detection of these injuries on MRI may help surgeons to individualize treatment and improve outcomes along with reduction of failure rates.
To retrospectively determine the rate of initially overlooked Kaplan Fiber Complex injuries in isolated primary ACL-deficient knees on routine MRI.
Patients who underwent isolated ACL reconstruction between 08/2013 and 12/2019 were identified. Preoperative knee MRIs (minimum 1.5 T) were reviewed and injuries to proximal and distal Kaplan fibers (KFs) were recorded by 3 independent reviewers. KF length and distance to nearby anatomic landmarks (lateral joint line and lateral femoral epicondyle) were measured. Additional radiological findings including bleeding, lateral femoral notch sign, and bone marrow edema (BME) were identified to detect correlations with KFC injury.
The intact KFC could reliably be identified by all three reviewers (85.9% agreement; Kappa 0.716). Fifty-three – Fifty-six % of the patients with initially diagnosed isolated ACL-ruptures showed initially overlooked injuries to the KFC. Injuries to the distal KFs were more frequent (48.1%, 53.8 % and 43.3% for Reviewer 1, 2 and 3, respectively) than injuries to the proximal KFs (35.6 %, 47.1 %, and 45.2% for Reviewer 1, 2 and 3, respectively). Bleeding in the lateral supracondylar region was associated with KFC injuries (p=0.023). Additionally, there was a positive correlation between distal KFs injuries and lateral tibial plateau BME (p=0.035). No associations were found with lateral femoral notch sign or other patterns of BME, including pivot-shift BME.
KF integrity and injury can be reliably detected on routine knee MRI. Fifty-three – Fifty-six % of the patients presenting with initially diagnosed isolated ACL ruptures had concomitant injuries to the KFC. This is of clinical relevance, as current routine MRI diagnostic may come along with a high number of occult or hidden KFC injuries. As injuries to the KFC contribute to persistent ALRI, which may influence ACL failure or reoperation rates, significant improvements in pre-operative diagnostic are required, in order to determine the exact injury pattern and to assist in surgical decision-making.