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. 2021 Feb 25;9(2):2325967120979986.
doi: 10.1177/2325967120979986. eCollection 2021 Feb.

Relationship of Anterior Cruciate Ligament Volume and T2* Relaxation Time to Anterior Knee Laxity

Hsin-Min Wang  1 , Sandra J Shultz  2 , Scott E Ross  2 , Robert A Henson  3 , David H Perrin  4 , Randy J Schmitz  2
Affiliations

Relationship of Anterior Cruciate Ligament Volume and T2* Relaxation Time to Anterior Knee Laxity

Hsin-Min Wang et al. Orthop J Sports Med. .

Abstract

Background: High anterior knee laxity (AKL) has been prospectively identified as a risk factor for anterior cruciate ligament (ACL) injuries. Given that ACL morphometry and structural composition have the potential to influence ligamentous strength, understanding how these factors are associated with greater AKL is warranted.

Hypothesis: Smaller ACL volumes combined with longer T2* relaxation times would collectively predict greater AKL.

Study design: Cross-sectional study; Level of evidence, 3.

Methods: College-aged active male (n = 20) and female (n = 30) participants underwent magnetic resonance imaging (MRI) and AKL testing. T2-weighted MRI scans were used to assess ACL volumes, and T2* relaxation times were used to assess ACL structural composition. AKL was measured via a commercial knee arthrometer. Forward stepwise linear regression with sex and weight (first step; suppressor variables) as well as ACL volume and T2* relaxation time (second step; independent variables) was used to predict AKL (dependent variable).

Results: After initially adjusting for sex and weight (R 2 = 0.19; P = .006), smaller ACL volumes combined with longer T2* relaxation times collectively predicted greater AKL (R 2 = 0.52; P < .001; R 2 Δ = 0.32; P Δ < .001). A smaller ACL volume was the primary predictor of greater AKL (R 2 Δ = 0.28; P < .001), with a longer T2* relaxation time trending toward a significant contribution to greater AKL (R 2 Δ = 0.04; P = .062). After adjusting for ACL volume and T2* relaxation time, sex (partial r = 0.05; P = .735) and weight (partial r = 0.05; P = .725) were no longer significant predictors.

Conclusion: AKL was largely predicted by ACL volume and to a lesser extent by T2* relaxation time (and not a person's sex and weight). These findings enhance our understanding of how AKL may be associated with a structurally weaker ACL. The current study presents initial evidence that AKL is a cost-effective and clinically accessible measure that shows us something about the structural composition of the ACL. As AKL has been consistently shown to be a risk factor for ACL injuries, work should be done to continue to investigate what AKL may tell a clinician about the structure and composition of the ACL.

Keywords: ACL size; MRI; knee; relaxation times.

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Conflict of interest statement

One or more of the authors has declared the following potential conflict of interest or source of funding: This work was supported by the Gateway MRI Center at the University of North Carolina at Greensboro. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Figures

Figure 1.
Figure 1.
Flow chart of screened and included participants. ACL, anterior cruciate ligament; ACLR, ACL reconstruction; AKL, anterior knee laxity; F, female; M, male.
Figure 2.
Figure 2.
Anterior cruciate ligament volume manual segmentation on sagittal image. Red area represents the anterior cruciate ligament segmentation.
Figure 3.
Figure 3.
T2* relaxation time map.
See this image and copyright information in PMC

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