Radiographic Outcomes using a Diaphyseal Engaging Femoral Stem for Revision Total Hip Arthroplasty

Diaphyseal engaging femoral stems are often required for revision total hip arthroplasty (THA) due to complex anatomy. However, no studies have been performed to identify the best implant or intraoperative radiographic parameters of stability. We sought to evaluate the rate of complications and radiographic parameters of an uncemented diaphyseal engaging femoral stem in revision THA. We retrospectively reviewed 54 patients who underwent revision THA using an uncemented diaphyseal engaging modular femoral stem between 2012 and 2019 with mean follow-up of 1.4 years. Mean age was 66.3 years (range 23-90), and 47.2% of patients were female. 36 (73.5%) hips were classified as a Paprosky 3a and 13 (26.5%) patients were classified as a Paprosky 3b. We calculated the radiographic subsidence, canal fill ratio, and complete cortical contact percentage, defined as the sum of anterior, posterior, medial, and lateral cortical contact. Chi-square related-samples t-test, and Pearson’s correlation coefficient were used to compare values. Significance was set at <0.05. Postoperative periprosthetic infection occurred in 4 patients (7.41%) and was the most common complication. There were no revisions for aseptic loosening or failure of the diaphyseal engaging femoral stem. Canal fill ratio (mean=85.85%, p<0.001) and complete cortical contact (mean=71.74%, p<0.001) were less than the expected, while subsidence was higher than the expected (mean=2.07mm, p<0.001). Complete cortical contact was not associated with canal fill ratio (p=0.07) or subsidence (p=0.50). This uncemented diaphyseal engaging femoral stem had a low complication rate (11.11%) when used for revision THA. While canal fill ratio and complete cortical contact was less than the expected mean of 100%, it was not correlated with subsidence. It is important for surgeons to know that this uncemented diaphyseal engaging femoral stem can be well fitting despite low canal fill ratio and cortical contact.