Feasibility of Using Orthogonal Fluoroscopic Images to Measure In Vivo Joint Kinematics

Abstract

Accurately determining in vivo knee kinematics is still a challenge in biomedical engineering. This paper presents an imaging technique using two orthogonal images to measure 6 degree-of-freedom (DOF) knee kinematics during weight-bearing flexion. Using this technique, orthogonal images of the knee were captured using a 3-D fluoroscope at different flexion angles during weight-bearing flexion. The two orthogonal images uniquely characterized the knee position at the specific flexion angle. A virtual fluoroscope was then created in solid modeling software and was used to reproduce the relative positions of the orthogonal images and X-ray sources of the 3-D fluoroscope during the actual imaging procedure. Two virtual cameras in the software were used to represent the X-ray sources. The 3-D computer model of the knee was then introduced into the virtual fluoroscope and was projected onto the orthogonal images by the two virtual cameras. By matching the projections of the knee model to the orthogonal images of the knee obtained during weight-bearing flexion, the knee kinematics in 6 DOF were determined. Using regularly shaped objects with known positions and orientations, this technique was shown to have an accuracy of 0.1 mm and 0.1 deg in determining the positions and orientations of the objects, respectively.

Investigation of in vivo 6DOF total knee arthoplasty kinematics using a dual orthogonal fluoroscopic system

“…Because fluoroscopic resolution is typically between 0.3 and 0.5 mm, it would be difficult to detect out-of-plane translations on the order of 5 mm using only a single image. 7 However, motion of the projected points that would not be discernable in the in-plane projection would be easily detected using an orthogonal image as demonstrated by the dual orthogonal imaging system (Fig. 3B).…”

“…7 Using sphere and cylinder models, the study showed that translation and rotation errors were within 0.1 mm and 0.18, respectively, for all DOF. The study of Li and colleagues suggests that a biplane fluoroscopic technique has an advantage over a single-plane technique due to the ability to detect out-of-plane translation and rotation.…”

“…While 3D model matching can theoretically be achieved using a single image, studies have found that the use of just a single image may not result in the same accuracy in the out-of-plane degrees-of-freedom (DOF) compared to the in-plane motion. 6,7 These studies usually reported anteroposterior motion of the tibiofemoral contact in the medial and lateral compartments. Currently, determination of TKA kinematics in 6DOF still presents a challenge in the field of biomechanics.…”

In‐vivo patellar tendon kinematics during weight‐bearing deep knee flexion

“…18,24 At flexion angles <608, as previous investigators pointed out, the internal rotation of the tibia relative to the femur caused by the quadriceps loads could be responsible for the decreasing coronal plane angle. 22,30 At higher flexion angles, the patellar tendon forms a smaller angle with the long axis of the tibia, where a smaller change in rotation with knee flexion was observed. 22,30 The patellar tendon demonstrated an increasing external rotation of its patellar insertion site with respect to the tibial attachment site as the knee flexed.…”

“…The decreasing sagittal plane angle of the patellar tendon with flexion might correspond to the posterior translation of the femur relative to the tibia during weight-bearing flexion. 22,30 However, the increasing internal tibial rotation (external femoral rotation) with flexion 22,30 corresponds to the less posterior orientation of the medial portion compared to the other portions. The data on the coronal plane orientation were also consistent with observations in the literature.…”