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Biomechanics and Robotics Division


Clinical Outcomes and
Applied Research Studies


Under the direction of Frank R. Noyes, MD and Edward S. Grood, PhD (Professor Emeritus, University of Cincinnati Department of Biomedical Engineering) the Biomechanics and Robotics Division conducts in-vitro studies on cadaveric knees using a highly sophisticated, custom designed robotic system based on the Grood-Suntay coordinate system. The robotic system applies precise motions and loads determining three dimensional motions and tibiofemoral compartment displacements. The purpose of these investigations is to better understand knee ligament function, surgical reconstructions to restore knee stability after injury, and replacement.

Our research is performed on a custom 6 degree-of-freedom robotic simulator that was developed and built by Edward S. Grood, PhD. Measurements of translations, rotations, and loads on all 3 axes are displayed and recorded in real-time.

2020 has seen the culmination of 2 years of research on ACL graft conditioning. This important research was published this year in the American Journal of Sports Medicine and benefited from the work of fellows Brad Ashman (2017) and Michael Palmer (2018).

The goal of this study was to determine a practical conditioning protocol for two of the most common ACL graft constructs: semitendinosus-gracilis and bone-patellar tendon-bone. One of the major findings of this study is that graft-board tensioning prior to graft implantation is not effective in minimizing post-operative graft elongation, as significant increases in anterior translation occur after implantation and subsequent cycling. In addition, this manuscript recommends to surgeons a simple conditioning protocol after implantation but prior to graft fixation that involves cycling the knee with an applied anterior force. Our research showed that this cyclic loading of the knee produced a properly conditioned graft that restored rotational knee stability at time-zero with minimal elongation.

Currently we are preparing a manuscript that uses data from 40+ knee specimens tested on the robot after ACL deficiency. This set of knee specimens represents one of the largest compilations of robotic biomechanical data to date. The use of a large historical data set allows us to characterize the biomechanical attributes of ACL deficiency with greater power than if we were to use a smaller sample size. For the current manuscript, we are using the large data set to explore the biomechanical relationship between the Lachman and pivot shift tests. These two tests are commonly used to diagnose ACL deficiency, but the pivot-shift test is performed differently surgeon-to-surgeon and is more subjective than the Lachman test. Because of this, it is important to determine at what degree of abnormal anterior translation in the Lachman test corresponds to a positive pivot-shift and, therefore, an ACL deficiency. In addition, the ACL graft tension at surgery is set using the Lachman test (millimeters of anterior tibial translation). The question being investigated is the correlation of the Lachman to a negative Pivot Shift subluxation after surgery. This research is currently being compiled into a manuscript and

will be submitted for review this year.

Current Studies:

1. Correlative function of a BPTB ACL reconstruction in restoring normal anterior tibial translation and normal lateral tibiofemoral compartment translations in a pivot shift test.

2. Development of the predictability of the relationship between the Lachman and pivot shift tests in the ACL-deficient knee using historical data.

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Publications

Noyes FR, Huser LE, Ashman B, Palmer M. Anterior cruciate ligament graft conditioning required to prevent an abnormal Lachman and pivot shift after ACL reconstruction: A robotic study of 3 ACL graft constructs. Am J Sports Med 2019;47(6):1376-1384.

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