Assessment of Early Biological Fixation of Cementless Tapered-Wedge Stems Using Digital Tomosynthesis

Background We aimed to compare radiographic and digital tomosynthesis assessments of early biological fixation of a cementless stem in primary total hip arthroplasty and to investigate the factors associated with early biological fixation. Methods Seventy-three patients underwent total hip arthroplasty using cementless short tapered-wedge stems. Both radiography and digital tomosynthesis were performed at 6 weeks and 3, 6, 12, and 24 months after surgery. The presence of spot welds (SW) was evaluated at each postoperative period to assess biological fixation between the stem and the femur. The area of contact between the femur and the stem was divided into seven zones based on Gruen’s zone classification. Results All 73 patients had no SW 6 weeks after surgery on radiography and digital tomosynthesis. Three months postoperatively, there was no SW on radiography; however, digital tomosynthesis revealed SW in 31 (42%) patients. Six months postoperatively, radiography showed 22 SW in 18 (24.7%) patients and digital tomosynthesis showed 94 SW in 48 patients (65.8%). Conclusion Digital tomosynthesis detected biological fixation between the stem and femur earlier than radiography; biological fixation may appear within 3 months after surgery.