High Rate of Initially Overlooked Kaplan Fiber Complex Injuries in Patients With Isolated Anterior Cruciate Ligament Injury

Abstract

Background: Injuries to the Kaplan fiber complex (KFC) are not routinely assessed for in the anterior cruciate ligament (ACL)-deficient knee during 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 scans may help surgeons to individualize treatment and improve outcomes, as well as to reduce failure rates. Purpose: To retrospectively determine the rate of initially overlooked KFC injuries on routine MRI in knees with isolated primary ACL deficiency. Study Design: Case series; Level of evidence, 4. Methods: Patients who underwent isolated ACL reconstruction between August 2013 and December 2019 were identified. No patient had had Kaplan fiber (KF) injury identified on the initial reading of the MRI scan or at the time of surgery. Preoperative knee MRI scans (minimum 1.5 T) were reviewed and injuries to the proximal and distal KFs were recorded by 3 independent reviewers. KF length and distance to nearby anatomic landmarks (the lateral joint line and the 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. Results: The intact KFC could reliably be identified by all 3 reviewers (85.9% agreement; Kappa, 0.716). Also, 53% to 56% 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% by the first, second, and third reviewers, respectively) than injuries to the proximal KFs (35.6%, 47.1%, and 45.2% by the first, second, and third reviewers, respectively). Bleeding in the lateral supracondylar region was associated with KFC injuries ( P = .023). Additionally, there was a positive correlation between distal KF injuries and lateral tibial plateau BME ( P = .035), but no associations were found with the lateral femoral notch sign or other patterns of BME, including pivot-shift BME. Conclusion: KF integrity and injury can be reliably detected on routine knee MRI scans. Also, 53% to 56% of the patients presenting with initially diagnosed isolated ACL ruptures had concomitant injuries to the KFC. This is of clinical relevance, as ACL injuries diagnosed by current routine MRI examination protocols may come with a high number of occult or hidden KFC injuries. As injuries to the KFC contribute to persistent ALRI, which may influence ACL graft failure or reoperation rates, significant improvements in preoperative diagnostic imaging are required to determine the exact injury pattern and to assist in surgical decision making.

High Rate of Initially Overlooked Kaplan Fiber Complex Injuries in Patients With Isolated Anterior Cruciate Ligament Injury: Letter to the Editor

“…In the present study by Berthold et al, 5 the only associated radiographic marker with a statistically significant correlation suggestive of KFC injury was bleeding in the lateral femoral supracondylar region. The authors once again reference the proximity of the superior genicular artery to the KFC, which is valid.…”

“…Importantly, an association between radiological KF injury and increased anterolateral rotatory laxity or higher rates of ACL reconstruction (ACLR) failure has not been shown in any clinical series. 1,8 In the current study by Berthold et al, 5 a high prevalence of injury to the Kaplan Fiber Complex (KFC) (either proximal, distal, or both fibers) was reported, varying between 35.6% and 53.8% among different raters. The study concluded that, ''KF integrity and injury can be reliably detected on routine knee MRI.''…”

“…In the current study by Berthold et al, 5 a high prevalence of injury to the Kaplan Fiber Complex (KFC) (either proximal, distal, or both fibers) was reported, varying between 35.6% and 53.8% among different raters. The study concluded that, “KF integrity and injury can be reliably detected on routine knee MRI.” In addition, the authors stated that, “As injuries to the KFC contribute to persistent anterolateral rotatory instability, which may influence ACL failure or reoperation rates, significant improvements in preoperative diagnostic criteria are required to determine the exact injury pattern and to assist in surgical decision-making.” As far as we are aware, there are no clinical studies that demonstrate an association between KF injury and subjective symptoms of persistent anterolateral rotatory instability after ACLR.…”

“…7 The high forces generated with eccentric muscle contraction are also a recognized cause of muscle injury, particularly in the quadriceps muscle group, as a result of ligamentous injury to the knee. 4,18 As detailed in the discussion by Berthold et al, 5 much of our knowledge related to the role the KFs play in controlling anterolateral rotatory laxity of the knee is derived from cadaveric sectioning studies with various biomechanical testing methods. 11,23 Indeed, sectioning of the KFs, in addition to the anterolateral capsule, is frequently used as a model to simulate anterolateral rotatory laxity and to assess the efficacy of various lateral extra-articular augmentation procedures.…”

High Rate of Initially Overlooked Kaplan Fiber Complex Injuries in Patients With Isolated Anterior Cruciate Ligament Injury: Response

“…As such, we believe that improvement in preoperative diagnosis, such as implementing 3-dimensional T1- and T2-weighted turbo spin echo sequences, 6 which could be included in routine protocols, may be helpful in assisting the surgeon’s choice if an additional LET should be discussed. 5 Finally, as correctly stated by Drs Devitt and Batty, bleeding or edema in this region may not be pathognomy for KFC injuries; however, if present, the surgeon should maintain special awareness for injuries in the anterolateral complex.…”