Optimal positioning for acetabular cup and cancellous fixation screws in Total Hip Replacement Surgery

Resumen

Acetabular cup positioning in total hip arthroplasty has become the most problematic part in this type of orthopedic surgery, given that there are a series of factors which are difficult to control, such as age, gender, medical conditions, reduced space and approach chosen. In this article, twelve cadaveric pelvises were analyzed by image processing and CAD software, to find the optimal combinations between the fundamental angles involved in cup orientation. The results of this work show that cup rotation between the first and third quadrants of safe zones could withhold longer screws without putting at risk important structures surrounding the pelvis. Optimal anteversion and abduction angles also help to avoid danger areas and a more serious complication such as dislocation in a hip replacement. The analyses show that 30 - 40 mm screws fit without risk with 15° ± 5° anteversion and 45° ± 5° abduction angles, if they are in the first and third quadrants of the pelvis. Any screw outside this area could seriously risk one or more structures near the pelvis, with dangerous consequences to the patient.