MRI-determined anterolateral capsule injury did not affect the pivot-shift in anterior cruciate ligament-injured knees
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The purpose of this study was to quantitatively compare the results of pivot-shift test between knees with anterior cruciate ligament (ACL) injury with and without anterolateral capsule (ALC) injury detected on MRI. ALC injury was hypothesized to worsen rotatory knee laxity.
82 patients with unilateral ACL injury were enrolled in this study. The pivot-shift test was performed under anesthesia before ACL reconstruction. Two evaluations were conducted simultaneously: IKDC clinical grading and the quantitative evaluation using an electromagnetic measurement system that determined tibial acceleration (m/s2). Two examiners identified the ALC injury on magnetic resonance imaging (MRI) and stratified patients into two groups: ALC-injured (ALC+) and ALC-intact (ALC−). ALC injury was diagnosed if the signal intensity on coronal T2-weighted sequences is increased. After confirming the reliability of the MRI, the difference in the pivot-shift between two groups was assessed.
Because of the poor agreement between examiners with respect to the ALC evaluations (κ coefficient of 0.25 and 58.5% concordance), the result from each examiner was analyzed separately. Examiner 1 found ALC injury in 42/82 knees (51%). The two groups had similar clinical grading (glide/clunk/gross: ALC+ group 21/18/3cases vs. ALC− group 21/16/3cases) (n.s.). Tibial acceleration during pivot-shift was also similar in the ALC+ (1.4 ± 1.2 m/s2) and ALC− (1.7 ± 1.3 m/s2) groups (n.s.). Examiner 2 found ALC injury in 28/82 knees (34%). Differences in clinical grading were not observed (glide/clunk/gross: ALC+ group 16/9/3 vs. ALC− group 26/25/3) (n.s.). However, the tibial acceleration in the ALC+ group (1.2 ± 0.8 m/s2) was significantly lower than that in the ALC− group (1.7 ± 1.3 m/s2, p = 0.03).
Concomitant ALC injury in knees with ACL injury was not consistently detected on MRI and did not affect rotatory knee laxity.
Level of evidence
Case–control study, level III.
KeywordsAnterior cruciate ligament Anterolateral capsule Pivot-shift Quantitative measurement MRI Electromagnetic measurement system
NM, YH, TM, and RK contributed to the study concept and design. NM, YH, TT, KN, DA, and TM contributed to the acquisition, analysis, and data interpretation. NM and YH drafted the article, and NM, YH, KN, TM, and RK critically revised the article for important intellectual content. All authors had final approval of the version to be submitted for publication. NM, YH, and RK agreed to be held accountable for all aspects of the work to ensure that questions related to the accuracy or integrity of any part of the work are appropriately addressed.
This study was supported by JSPS KAKENHI Grant number JP16K10902.
Compliance with ethical standards
Conflict of interest
We have no conflicts to disclose.
This study was approved by the institutional review board of Kobe University (ID no. 341).
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