Stability Analysis of the Pelvis after Type I Resection of Iliac Tumor

The purpose of this study is to analyze the pelvic stability after type I resection of iliac tumor. Six adult cadaveric specimens were tested. The iliac subtotal resection models were established according to Ennecking' s type I resection. Markers were affixed to the key regions of the pelves. Axial loading from proximal lumbar was applied by MTS load cell in the gradient from ON to 500 N in the double feet standing state. Images in front view were obtained using CCD (charge coupled device). Based on Image J software, displacements of SI (the first sacral vertebrae) of the resected pelves and the intact pelves were calculated respectively using digital marker tracing method with center-of-mass algorithm. Serious instabilities were found in the resected pelves. The rotational movements SI around the normal side femoral head of the resected pelvis were found. The average vertical displacement of SI of the resected pelvis was 6.951plusmn3.384 mm under vertical load of 500 Newton, which were 8.34 times compared with the intact pelvis. The average rotational angle of SI around the normal side femoral head of the resected pelvis was 4.055 plusmn 1.843deg, which were 12.5 times compared with the intact pelvis. Biomechanical model of type I resection of iliac tumor was established. Essential pelvic reconstruction must be introduced because of the serious instability of the pelvis after tumor resection. Digital marker tracing method with center-of-mass algorithm based on Image J software has good perspective for application in biomechanical research, which is a simple method with high precision.