Inferior extended fixation utilizing porous titanium augments improves primary anti-rotational stability of the acetabular component

BackgroundThe primary anti-rotational stability is critical to preventing cup tilting failure following revision total hip arthroplasty, but is frequently compromised by severe ischial bone loss. A novel technique of “inferior extended fixation” was introduced by securing a porous metal augment into the deficient ischium. This study evaluated the effect of this technique on primary anti-rotational stability in revision total hip arthroplasty.MethodsComposite hemipelvis specimens, acetabular components and “lotus” augments were used to simulate total hip arthroplasty surgeries. Three different cementless operative settings of cup implantation were simulated: (1) native ischium without defects; (2) ischium with a defect not reconstructed; (3) ischial defect reconstructed with inferior extended fixation using a lotus augment. Lever-out testing was used to examine primary anti-rotational stability, which was measured as interface stiffness and yield moment.FindingsCompared with the native ischium setting, the mean interface stiffness decreased by 53.1% in the ischial defect setting (p < 0.001). In the inferior extended fixation setting, the mean value was 110% greater than that in the ischial defect setting (p = 0.014), and comparable to that in the native ischium setting (p = 1). Similar results were observed for the yield moment (declined by 63.1%, p < 0.001; 200% higher, p < 0.001; and p = 0.395; respectively).InterpretationIn revision total hip arthroplasty with severe ischial defects, inferior extended fixation with a lotus porous titanium augment restores anti-rotational stability of the acetabular component to the level of that with a native ischium, which provides the mechanical environment for bone ingrowth and prevents cup tilting failure.