Abstract
Introduction
During THA in lateral position, keeping accurate lateral position is very important for obtaining good cup position. We normally use two kinds of hip positioner, but sometimes we can only use universal positioner provided with operational table. The pelvic tilt can be changed by surgical procedures such as traction, dislocation, reduction and so forth. In the present study, pre-op and post-op pelvic tilt was assessed using Kinect (Xbox 360′s sensor) as 3D scanner.
Materials and Methods
As a 3D scanner, “Kinect®” was used (Fig. 1) with scanning software “Artec Studio 9 ®”. First, accuracy of the scanning system was validated, then 6 postero-lateral approach hip replacement with lateral position surgery cases (Fig.2) (1 male and 5 female, average 55.5 y.o., average BMI 27.6, IMP® positioner: 3 cases, Kyocera positioner: 2 cases, universal fixator provided with surgical table: 1 case), one direct anterior approach case, and one supine antero lateral case (Fig. 3) were scanned pre and post operatively. Pelvic tilts were assessed using tableside rails or edges of positioner that is tightly fixed to the table, as the reference.
Results
As for the accuracy, 199.2mm length object was 3 dimensionally assessed 5 times the result was 198.7 0+/− 0.87mm, 45.0 degree angle object was assessed 44.59 +/− 0.48 degree. The pelvis was frontally tilted 4.33 +/− 4.03 (0–10) degree after surgery. Correlation between BMI and tilt change was not significant in all 6 cases. But when the fattest person; whose A-P diameter is bigger than M-L diameter around stomach and unexpectedly stable in lateral position; was excluded, correlation of R2=0.68 was observed.
In the DAA case and AL supine case, the pelvis was not moved by extending hip joint.
Discussion
Even using hip positioner, at maximum 10 degree tilt was observed. So we have to be very careful for it. In the supine cases, the pelvis was not moved by hip hyperextension. However, during cup impaction, the pelvis can move. We must also be careful for it. In this study, position during surgery was not assessed.
