Mid-term results of titanium–titanium modular neck femoral stem in primary total hip arthroplasty

Abstract Background Modular neck femoral stems are advantageous because they can accurately restore the ideal hip geometry using various options in terms of offset, length, and version. However, there are concerns regarding junctional problems. Despite several reports on such issues, there is a lack of study on mid- to long-term results of these stems. The current study evaluated the mid-term results of patients who underwent primary total hip arthroplasty using a titanium – titanium (Ti–Ti) modular neck femoral stem. Methods In total, data on 47 hips (42 patients) that could be followed-up for ≥ 5 years after primary total hip arthroplasty using the Ti–Ti modular neck femoral stem from 2011 to 2015 were reviewed. There were 22 male and 20 female patients, and their mean age was 56.3 (range: 31–76) years. The mean follow-up period was 8 (range: 5–12) years. Functional and radiological outcomes, complications, and reoperations were investigated. In addition, we conducted a comparative analysis of the outcomes between those who underwent surgery using the Ti–Ti modular neck femoral stem and 41 hips (35 patients, 19 males and 16 females) that underwent primary total hip arthroplasty using nonmodular femoral stems as a control. Results In all Ti–Ti cases, the mean Harris Hip Scores were 50.6 (range: 6–59) preoperatively and 92.7 (range: 78–99) at the last follow-up ( P < 0.001). Regarding the neck component’s modularity, straight neck components were used in all Ti–Ti cases, and an anteverted or a retroverted neck was not used in any case. Stem revision was performed in one hip due to aseptic loosening. One hip underwent open reduction and internal fixation due to periprosthetic fracture without stem loosening. There were no cases of osteolysis and periprosthetic joint infection and clinically detectable junctional problems. The stem survival rate, with any stem revision as the endpoint, at 12 years was 96.6%. No significant difference was observed in the functional and radiological outcomes beween the Ti–Ti and nonmodular groups. Conclusions The Ti–Ti modular neck femoral stem had comparable results with broadly used nonmodular femoral stems; hence, it can be a reliable option in primary total hip arthroplasty. However, in terms of the modularity itself of the modular neck femoral stem, whether the modular neck femoral stem is useful in uncomplicated primary total hip arthroplasty is unclear.