Markerless Three Dimensional Measurement of Knee Kinematics Using Single-Plane Fluoroscopy

Abstract

Kinematics of the normal, injured, or prosthetically replaced knee joint are a complex combination of rolling, gliding and rotational motions which are significantly influenced by the activity undertaken, the integrity of the ligaments and capsular structures, muscle activity, and articular geometry. Accurate kinematic information is critical to understanding the function and pathogenesis of the knee, particularly during weight bearing dynamic activities. The present study was undertaken to characterize the accuracy of a non-invasive fluoroscopic technique for measuring dynamic three-dimensional (3D) knee motions in individuals whose knees have not been prosthetically replaced. This technique utilizes orthogonal planar radiographic views of the knee to create a 3D contour model of consistently identifiable bony features for both the tibia and femur. The measurement technique is implemented by projecting the contour model onto digitized fluoroscopic images of the moving knee, and determining the translations and rotations which give the best correspondence between the projected contour model and the radiographic projection of the bone. Controlled in vitro assessment of the technique resulted in a rotational accuracy of 1.8 degrees and a sagittal plane translational accuracy of 1.2 mm.

Weight-bearing knee kinematics in subjects with two types of anterior cruciate ligament reconstructions

“…The average accuracy of this measurement technique calculated in the in vitro study is ±0.8° for rotations about the three orthogonal axes, ±1.2 mm for sagittal plane translations, and ±4.0 mm for medial/lateral translations [3]. For all of the knees tested both the medial and the lateral femoral condyles translated posteriorly with knee flexion.…”

“…The measurement accuracy of this technique was characterized using controlled in vitro conditions [3, 4]. An intact frozen knee specimen was rigidly mounted to a biaxial (linear/rotary) servohydraulic testing machine (Instron model 8521, verified to ASTM E4 and E74 standards).…”

“…The purpose of this study was to determine whether normal three‐dimensional (3D) weight‐bearing knee kinematics were restored in two groups of subjects with different ACL reconstructions. To measure the dynamic weight‐bearing movements of the knee accurately, we used a technique described by Banks et al [3, 4]. This 3D measurement technique, which is a based on an established technique for measuring kinematics in patients with total knee arthroplasty [2], uses lateral fluoroscopy and provides an accurate noninvasive in vivo dynamic measurement of joint kinematics.…”