2015 ISAKOS Biennial Congress ePoster #1131

Reliability of a 2D Simple Image Analysis Method to Predict 3D Bony Motion of the Lateral Knee Compartment During the Pivot Shift Test

Fabio V. Arilla, MD, Estancia Velha, RS BRAZIL
Amir Ata Rahnemai Azar, MD, Pittsburgh, PA UNITED STATES
Carlos H. Yacuzzi, MD, Buenos Aires, BA ARGENTINA
Daniel Guenther, MD, PhD, Cologne GERMANY
Ben Engel
Freddie H. Fu, MD, Pittsburgh, PA UNITED STATES
Richard Debski, PhD, Pittsburgh, PA UNITED STATES
Volker Musahl, MD, Pittsburgh, PA UNITED STATES

University of Pittsburgh, Pittsburgh, PA, USA

FDA Status Not Applicable

Summary: The present study evaluated the reliability of a 2D simple image analysis method in predicting the 3D bony motion of the knee during the pivot shift test.

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Abstract:

Background

The pivot shift test is the most specific diagnostic clinical test for anterior cruciate ligament (ACL) injury and relates to patient-reported outcome (Ayeni et al., 2012). There is still a lack of prevailing quantitative measurement systems that would allow an objective and comparable evaluation of the test.

Purpose

To determine the reliability of a 2D simple image analysis method in predicting the 3D bony motion of the intact, ACL-deficient (ACLD), and ACL-reconstructed (ACLR) knee during the pivot shift test and assess the intra- and inter-observer agreement. It was hypothesized that a strong correlation would be found between both methods, as well as a high intra- and inter-observer agreement.

Methods

Seven knees from whole lower extremity (mean age 60 years) were utilized. Three experienced orthopedic surgeons performed three trials of standardized pivot shift test on intact, ACLD and ACLR knees. Two devices were used to measure motion of the lateral knee compartment simultaneously:
1) 2D image analysis: a tablet computer was used to record and analysis movement of three markers attached to skin over Gerdy’s tubercle, fibular head and lateral epicondyle during pivot shift test. Anterior translation of lateral compartment was determined by drawing vectors between the three markers and calculating the perpendicular motion of the femur relative to the tibia.
2) 3D translation of lateral compartment: electromagnetic tracking system was used to measure movement of same bony landmarks utilizing sensors attached to femur and tibia bone.
Pearson correlation, One way ANOVA and post-hoc analysis were used to analysis the data. To access the agreement between surgeons, the intraclass correlation was determined.

Results

The 2D simple image analysis demonstrated a strong correlation with the 3D bony motion in all examiners (r= 0.69-0.79, P<0.05). Knee motion during the pivot shift test was significantly greater in the ACLD group (2D= 2.7± 0.8, 3D=11.1± 3.6) compared to the intact (2D= 1.2± 0.6, 3D= 3 ± 2.8) and ACLR (2D= 0.8 ± 0.2, 3D=4.1 ± 3.8). No significant difference was found between intact and ACLR knees (p>0.05).
The intra-class correlation coefficient for the three examiners was 0.92, 0.78, and 0.76 for 3D bony motion analysis and 0.81, 0.7 and 0.71 for 2D simple image analysis. Inter-observer agreement was 0.72 for 3D bony motion analysis and 0.65 for 2D simple image analysis.

Discussion

The most significant finding of this study was that strong correlation exists between 2D simple image analysis and actual bony motion even though the 3D bony motion was almost 3 times the amount predicted by the 2D simple image analysis. Although difference exists between tracking the skin markers and bone motion but still 2D image analysis can be considered a reliable tool to predict actual bony movement. Variation exists in terms of performing pivot shift maneuver between examiners, however 2D image analysis is able to detect difference between different knee states. This technique can provide a non-invasive and clinical applicable tool to quantify pivot shift test.