The Incidence of Kaplan Fiber Injury Associated With Acute Anterior Cruciate Ligament Tear Based on Magnetic Resonance Imaging

Abstract

Background: Kaplan fibers are distinct deep layers of the distal iliotibial band (ITB) that anchor the ITB to the distal femur and have a role in rotational stability of the knee. However, the incidence of Kaplan fiber injury in the setting of acute anterior cruciate ligament (ACL) tear is unknown. Purpose: To determine the reliability of identifying and evaluating Kaplan fibers on magnetic resonance imaging (MRI) examinations based on previously reported characteristics and to report on the incidence of combined ACL and Kaplan fiber injuries based on MRI examinations. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: Patients with an acute primary ACL tear who obtained a postinjury MRI scan at our institution and were treated with ACL reconstruction between January 1, 2007, and May 31, 2012, were identified from an institutional registry. Each patient’s postinjury MRI scan was reviewed by 2 musculoskeletal radiologists, who identified Kaplan fibers and graded them as intact, injured, or not visualized. Intrarater reliability was measured using the intraclass correlation coefficient (ICC), and interrater reliability was measured using the kappa statistic. Results: A total of 72 patients were identified. For the proximal Kaplan fibers, 50% versus 58% were identified as injured, 32% versus 29% were identified as intact, and 18% versus 13% were not visualized by radiologist 1 and 2, respectively. For the distal Kaplan fibers, 46% versus 60% were identified as injured, 43% versus 28% were identified as intact, and 11% versus 12% were not visualized by radiologist 1 and 2, respectively. The ICC intrarater reliability measurements were 0.89 (95% CI, 0.83-0.93) for proximal Kaplan fibers and 0.66 (95% CI, 0.51-0.78) for distal Kaplan fibers. The interrater reliability measurements for both radiologists showed substantial agreement (kappa = 0.7) for proximal Kaplan fibers and moderate agreement (kappa = 0.51) for distal Kaplan fibers. Conclusion: Kaplan fibers were visualized on MRI studies in the majority of cases, with substantial reliability for the proximal fibers and moderate reliability for the distal fibers. There was an associated injury to either the proximal or distal or both Kaplan fibers in the majority of acute primary ACL tears.

Injuries to the anterolateral ligament are observed more frequently compared to lesions to the deep iliotibial tract (Kaplan fibers) in anterior cruciate ligamant deficient knees using magnetic resonance imaging

“…Khanna et al [ 21 ] reported in a cohort of 20 patients an injury rate of 82% to the proximal- and 29% to the distal fibers, respectively. Recently, Marom et al [ 32 ] identiefied with moderate to good inter- and intrarater reliablity injuries to the Kaplan fiber complex in 51% of the examined patients. However, no clear differentiation between periligamentous edema, partial or compleate tear was made.…”

“… 0.94 0.94 Berthold et al [ 3 ] 2020 10 Knee specimens Proximal and distal fibers inserting distal to the lateral intermuscular septum at the metaphysis of the posterolateral femur 100% proximal fibers 90% distal fibers n.a. Excellent Excellent Marom et al [ 32 ] 2020 72 Patients with acute ACL surgery Discrete fibrous band with appropriate anatomic course and expected relationship to anatomic landmarks identified in at least 2 consecutive slices 82%/87% a 64%/71% b Proximal fibers: 0.7 Distal fibers: 0.51 Proximal fibers: 0.89 Distal fibers: 0.66 n.a. not applicable, n.s.…”

“…The Kaplan fibers have been further distinguished in proximal and distal supracondylar fibers connecting the ITT to the postero-lateral femur approximately 28–41 mm above the lateral femoral epicondyle [ 16 , 17 , 29 , 42 ]. Recent articles examining both healthy individuals and knee specimens reported good MRI visibility of the dITT ranging between 60.6 and 100% [ 2 , 3 , 28 , 32 ].…”

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

“…11,24 Encouragingly, independent research groups have been consistent in the radiological identification of the KFs. 1,6,22,27,30 It remains unclear, however, as to what constitutes a clinically relevant KF injury on magnetic resonance imaging (MRI) and how wide the ''goalposts'' should be set when diagnosing an injury. In the emerging literature, different rates of KF injury have been reported based on the differences in diagnostic criteria.…”

“…8,17,25 In a recent editorial from The American Journal of Sports Medicine, the editor-in-chief, Dr Reider, stated that ''orthopaedic surgeons continue their quest for ways to increase the success rate of ACL reconstruction, the use of an adjunctive lateral extra-articular procedure is enjoying a renaissance.'' 27 Also, 38% of the members of the American Orthopaedic Society for Sports Medicine use some type of LET for selected cases. 30 Consequently, it feels that the orthopaedic society is currently divided, as considerable disagreement exists regarding the anatomic and biomechanical importance of the anterolateral complex, 13,27 and whether an LET is needed or not.…”