Background

Biomechanical cadaveric studies have recently shown that Kaplan fibers (KF) of the iliotibial band (ITB) play a role in controlling anterolateral rotatory laxity of the knee. Other studies have also reported that KF injury can be detected on MRI in the setting of anterior cruciate ligament (ACL) tears. However, the contribution of injury to KF on anterolateral rotatory laxity remains unclear in the clinical setting.

Purpose

The purpose of the present study was to investigate the effect of MRI-detected concomitant injury to KF in ACL injured knees on anterolateral rotatory knee laxity measured by quantitative pivot-shift test in the clinical setting. It was hypothesized that the ACL-injured knees with concomitant KF injury would exacerbate tibial acceleration and manual grading of the pivot-shift test.

Methods

Eighty-five patients with primary acute ACL tears (age: 26 ± 12 years, 44 male/41 female), whose MRI was taken within 90 days after the injury, were enrolled in this study. The presence of KF injury was assessed using MRI as previously described, and the subjects were allocated into the KF injury group and non-KF injury group. At the time of ACL reconstruction, the pivot-shift test was performed under anesthesia; the tibial acceleration (m/s^2) during the pivot-shift test was quantitatively measured using an electromagnetic measurement system as previously reported. The manual grading of the pivot-shift test was also assessed according to the International Knee Documentation Committee’s guidelines. Patient demographics including the rate of concomitant meniscal injury were compared between two groups. Tibial acceleration of pivot-shift test was compared using Mann-Whitney U-test, and Manual grade of the pivot-shift test was compared between two groups using Pearson’s chi- squared test. (p < 0.05).

Results

KF injury was detected in 20 patients (age: 29 ± 13 years; 9 male/11 female; period from injury to MRI, 8.0 ± 14.0 days) while no KF injuries were observed in 65 patients (age: 25 ± 11 years; 35 male/30 female; period from injury to MRI, 8.9 ± 12.1 days). The rate of KF injury was 23.5%. No significant differences were observed in terms of demographic data including age, sex, the period from injury to MRI between two groups. The rate of meniscal injury was not significantly different between the KF injury group (50.0 %) and non-KF injury group (53.8 %). Moreover, no significant differences were observed in tibial acceleration or manual grade of the pivot-shift test between the KF injury group (1.4 ± 1.2 m/s^2) and non-KF injury group (1.2 ± 0.8 m/s^2).

Conclusion

Concomitant KF injury did not significantly affect the pivot-shift phenomenon in acute ACL-injured knees. The findings suggest that the contribution of KF injury to anterolateral rotatory knee laxity may be limited in the clinical setting.