Acute non-contact anterior cruciate ligament tears are associated with relatively increased vastus medialis to semimembranosus cross-sectional area ratio: a case-control retrospective MR study
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Hamstring muscle deficiency is increasingly recognized as a risk factor for anterior cruciate ligament (ACL) tears. The purpose of this study is to evaluate the vastus medialis to semimembranosus cross-sectional area (VM:SM CSA) ratio on magnetic resonance imaging (MRI) in patients with ACL tears compared to controls.
Materials and methods
One hundred knee MRIs of acute ACL tear patients and 100 age-, sex-, and sidematched controls were included. Mechanism of injury, contact versus non-contact, was determined for each ACL tear subject. The VM:SM CSA was measured on individual axial slices with a novel method using image-processing software. One reader measured all 200 knees and the second reader measured 50 knees at random to assess inter-reader variability. The intraclass correlation coefficient (ICC) was calculated to evaluate for correlation between readers. T-tests were performed to evaluate for differences in VM:SM CSA ratios between the ACL tear group and control group.
The ICC for agreement between the two readers was 0.991 (95% confidence interval 0.984–0.995). Acute ACL tear patients have an increased VM:SM CSA ratio compared to controls (1.44 vs. 1.28; p = 0.005). Non-contact acute ACL tear patients have an increased VM:SM CSA ratio compared to controls (1.48 vs. 1.20; p = 0.003), whereas contact acute ACL tear patients do not (1.23 vs. 1.26; p = 0.762).
Acute non-contact ACL tears are associated with increased VM:SM CSA ratios, which may imply a relative deficiency in hamstring strength. This study also demonstrates a novel method of measuring the relative CSA of muscles on MRI.
KeywordsAnterior cruciate ligament ACL Anterior cruciate ligament tear ACL tear Hamstring Quadriceps Vastus medialis Semimembranosus
Compliance with ethical standards
Conflict of interest
The authors state that they have no conflicts of interest.
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