CT-Free Registration Method for Finding Accurate Orientation of Acetabular-Cup in Total Hip Replacement Surgery / 대한정형외과연구학회지

ABSTRACT

PURPOSE: This paper is proposing an improved CT-free registration method which may provide us an accurate and reliable placement of acetabular cup without CT/MRI images. DESIGN AND METHODS: The proposed method employs a T-bar shaped gauge placed on the anatomical landmarks of the pelvis for the registration. The T-bar shaped gauge has its own LED markers and the position of the gauge is obtained through OPTOTRAK3020 system. These landmark points are the anterior superior iliac spines and the symphysis pubis defining anterior pelvic plane. Two subjects were tested to compare the landmark based registration and the proposed T-bar based registration. RESULTS: The measurement deviations of the pelvic obliquity in the frontal plane, tilt in the sagittal plane, and rotation in the transverse plane were 2.08, 1.41, and 2.51 degrees respectively in the point based registration. The T-bar based registration produced 40% smaller deviations(p<0.05) the pelvic obliquity in the frontal plane, tilt in the sagittal plane, and rotation in the transverse plane were 0.84, 0.81, and 1.17 degrees respectively in the T-bar based registration. There was no outlier exceeding 5 degrees in measurement deviation by the T-bar based registration while the outliers were found by the landmark based registration. CONCLUSIONS: We found that T-bar based CT free registration method is more reliable and accurate than the landmark based registration for the acetabular cup navigation. Also, the new method produced more precise registration(p<0.05). We are expecting some offset error of the new registration method due to the skin thickness existing between the T-bar frame and the bony pelvic frame, which may be compensated if we may accumulate sufficient database of the offset.