The anatomical study of safe zones of the screw fixations in acetabular revision surgery / 中华外科杂志

<p><b>OBJECTIVE</b>To evaluate the safe zones of screw fixations of Jumbo cup and reinforcement rings in acetabular revision surgery.</p><p><b>METHODS</b>From December 2006 to January 2008, 11 fresh frozen human cadaver pelvises were prepared by removing all soft tissues except the medial neurovascular structures, each specimen was held in supine position with clamps. The anteroposterior radiographs were taken after the Jumbo cups or reinforcement rings were fixed in places. Left sides of acetabulum were used to create the models to evaluate the safe zones of the high hip center and Jumbo cups. Right sides were used to evaluate the safe zones of 3 different designs of acetabular reinforcement rings (Müller, Ganz, Burch-Schneider cage).</p><p><b>RESULTS</b>Jumbo cups: screws in the superoanterior and anteroinferior quadrants could cause neurovascular injuries. High hip center: neurovascular injuries could be expected in all quadrants except the inferoposterior and posterior half of superoposterior quadrant. Müller ring: screws placed in the intra-acetabular and extra-acetabular areas of the superoanterior quadrant could cause neurovascular injuries. Ganz ring:the screws placed in superoanterior quadrant and apex area were dangerous. The insults were confirmed in all of the specimens. Burch-Schneider cage: the medial nervous and vasculature structures were injured in all of the specimens if the screws placed in the superoanterior (intra-acetabular and extra-acetabular) quadrant. Screws for ischial fixation could cause sciatic nerve injury.</p><p><b>CONCLUSIONS</b>In revision acetabular surgery, the superoanterior quadrant, the anterior half of the superoposterior quadrant and the implant's central area are unsafe for screw fixation, especially when the exposed thread is longer than 15 mm.</p>

A cadaveric study of relationships among rotational alignment reference axes of distal femur and tibial mechanical axis / 中华外科杂志

<p><b>OBJECTIVES</b>To investigate the relationships among rotational alignment reference axes of distal femur and tibial mechanical axis, and determine the safest rotational alignment reference axis.</p><p><b>METHODS</b>Digital photos were taken of 30 cadaveric lower extremities with knee in extension and flexion at 90 degrees , angles were measured among tibial mechanical axis and a line perpendicular to clinical epicondylar axis, a line perpendicular to surgical epicondylar axis, Whiteside's line and femoral mechanical axis. Statistical analysis of relationships among those axes were performed.</p><p><b>RESULTS</b>The angles among the tibial mechanical axis and a line perpendicular to the clinical epicondylar axis, a line perpendicular to the surgical epicondylar axis, Whiteside's line and femoral mechanical axis were 0.6 degrees varus, 3.9 degrees varus, 0.2 degrees valgus and 3.0 degrees varus respectively. The angle between the femoral mechanical axis and the tibial mechanical axis was significantly larger than the angles among the tibial mechanical axis and a line perpendicular to the clinical epicondylar axis, the Whiteside's line (P < 0.05). There was no significant difference compared with the angle between a line perpendicular to the surgical epicondylar axis and the tibial mechanical axis. Angles of the clinical epicondylar axis, the surgical epicondylar axis and the Whiteside's line between knee extension and flexion were 2.3 degrees valgus, 0.9 degrees varus and 3.1 degrees valgus respectively.</p><p><b>CONCLUSION</b>The surgical epicondylar axis rather than the clinical epicondylar axis or the Whiteside's line is the safest femoral rotational alignment reference axis intraoperatively.</p>