Developing a Technique for the Imaging-Based Measurement of ACL Elongation: A Proof of Principle.

Robert Csapo,Dieter Heinrich,Andrew D Vigotsky,Christian Marx,Christian Fink,Shantanu Sinha

doi:10.3390/diagnostics11112126

Abstract

Towards the goal of obtaining non-invasive biomarkers reflecting the anterior cruciate ligament’s (ACL) loading capacity, this project aimed to develop a magnetic resonance imaging (MRI)-based method facilitating the measurement of ACL elongations during the execution of knee stress tests. An MRI-compatible, computer-controlled, and pneumatically driven knee loading device was designed to perform Lachman-like tests and induce ACL strain. A human cadaveric leg was used for test purposes. During the execution of the stress tests, a triggered real-time cine MRI sequence with a temporal resolution of 10 Hz was acquired in a parasagittal plane to capture the resultant ACL elongations. To test the accuracy of these measurements, the results were compared to in situ data of ACL elongation that were acquired by measuring the length changes of a surgical wire directly sutured to the ACL’s anteromedial bundle. The MRI-based ACL elongations ranged between 0.7 and 1.7 mm and agreed very well with in situ data (root mean square errors, RMSEs ≤ 0.25 mm), although peak elongation rates were underestimated by the MRI (RMSEs 0.19–0.36 mm/s). The high accuracy of elongation measurements underlines the potential of the technique to yield an imaging-based biomarker of the ACL’s loading capacity.

Highlights

There was gen gations and elongation rates between the data obtained in situ and through magnetic resonance imaging (MRI)
We here propose a measurement technique to perform Lachman-like knee stress tests in magnetic resonance (MR) scanners and measure the resultant anterior cruciate ligament (ACL) elongations
The measurement system consists of a pneumatically driven, computer-controlled, and MR-compatible knee stress test device that generates trigger impulses to synchronize the acquisition of gated cine-images with stress-relaxation cycles

Summary

Introduction

Tears of the anterior cruciate ligament (ACL) represent one of the most frequent orthopedic injuries in physically active cohorts. According to research investigating the mechanisms and risk factors for non-contact ACL injuries, various anatomical (e.g., decreased intercondylar notch width or increased tibial plateau slope), hormonal (pre-ovulatory phase in women), and neuromuscular (decreased hamstring, hip abductor, and knee external rotator strength) factors, as well as specific genetic predispositions (COL1A1 polymorphism or COL3A1 AA genotype), may increase a subject’s susceptibility to ACL tears [1,2]. With respect to the morphology of the ACL, ACL-injured subjects typically feature longer and narrower ligaments than healthy controls [3]. Of even greater significance are the ACL’s mechanical properties, which are related to [4] but not solely determined by the ligament’s dimensions

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