Dual-mobility with modular components for primary total hip arthroplasty in bilateral bony ankylosis of the hips: A case report

Introduction and importance: Primary total hip arthroplasty (THA) is a procedure performed in the United States for a variety of indications, with operation rates slated to increase over 275 % by 2040 when compared to 2014 (Thilak et al., 2015). Dual-mobility (DM) implants have gained popularity in the United States since gaining approval in the early 2010s (Heckmann et al., 2020). It has been well reported that DM implants decrease the risk of dislocation after primary and revision THA (Vielpeau et al., 2011; Donovan et al., 2022; Heifner et al., 2023; Foissey et al., 2023; Schmidt et al., 2020; Neri et al., 2019). Case presentation: We present the case of a 33-year-old male with a suspected ankylosing spondylitis (AS) diagnosis and bilateral bony ankylosis of the hips who underwent staged THA with modular dual-mobility (MDM) implants. At one year post-operatively, the patient is walking without the use of an assistive device and reports a VAS pain score of 0 at rest and 2 with activity and HHS of 90. Clinical discussion: Implant selection is important in this patient population due to the increased risk of dislocation. Contemporary reports reveal MDM implants have demonstrated a substantial reduction in dislocation risk compared to fixed-bearing implants in patients with a high risk of dislocation. We opted to place the acetabular component inside the safe zone to improve stability and use the dual-mobility prosthesis to achieve our desired range of motion. Conclusion: The improved stability of DM implants allows for a greater range of acetabular positions in patients who have a highly unpredictable functional outcome at the time of surgery. Our preliminary results contribute to the growing list of indications for MDM total hip arthroplasty.