A 3D Kinematic Measurement of Knee Prosthesis Using X-ray Projection Images(Countermeasure to the Overlap between the Tibial and Femoral Silhouettes)

Abstract

We have developed a technique for estimating 3D motion of knee prosthesis from its 2D perspective projections. As Fourier descriptors were used for compact representation of library templates and contours extracted from the prosthetic X-ray images, the entire silhouette contour of each prosthetic component was required. This caused such a problem as our algorithm did not function when the silhouettes of tibio and femoral components overlapped with each other. Here we planned a novel method to overcome it; which was processed in two steps. First, the missing part of silhouette contour due to overlap was interpolated using a free-formed curvature such as Bezier. Then the first step position/orientation estimation was performed. In the next step, a clipping window was set in the projective coordinate so as to separate the overlapped silhouette drawn using the first step estimates. After that the localized library whose templates were clipped in shape was prepared and the second step estimation was performed. Computer model simulation demonstrated sufficient accuracies of position/orientation estimation even for overlapped silhouettes; equivalent to those without overlap.

Predicting 3D pose in partially overlapped X-ray images of knee prostheses using model-based Roentgen stereophotogrammetric analysis (RSA)

“…Hirokawa et al [4] attempted to fit the overlapped outlines and reported poorer RSA results than other studies, which removed the overlapped outlines. The current authors attribute this to the fact that in Hirokawa's method, only the continuity of the outline curvatures is considered in the vicinity of the intersected points.…”

“…If the projected images of femoral and tibial prostheses are overlapped with each other, it is more difficult for the clinician to evaluate the prosthetic misalignment and wear (Fig. 1b) [4,6,9,12,13,26].…”

“…However, manual manipulation might not be precise enough, and it is highly time-consuming, especially for fluoroscopic images [1,12]. Hirokawa et al [4] calculated changes in curvature to automatically define the overlapped regions. They assumed that the intersected outlines form an edge and the curvature approaches −∞.…”

A 3D kinematic estimation of knee prosthesis using X-ray projection images: clinical assessment of the improved algorithm for fluoroscopy images

“…As the details of the technique have been fully described elsewhere [9], a brief explanation will be given below.…”

“…Although several researchers [3,9,22] have noted that displacement of the knee prosthesis components along the medico-lateral (z) axis is unlikely, the errors in z-translation result in errors of other kinds of rotation/translation. Then it was verified that incorporation of the articulation model improved estimation accuracies well, especially as for z-translation estimation accuracy to a remarkable extent (Fig.…”