Intraprosthetic Dislocation of Dual-Mobility Total Hip Arthroplasty: The Unforeseen Complication.

Total hip arthroplasty (THA) is one of the most successful and widely accepted orthopedic procedures. Instability after THA is one of the most significant postoperative complications. Dual-mobility THA components were introduced in 1974 to overcome the risk of instability by increasing the jump distance. Dual-mobility bearings couple two articulations, namely, one between a 22-28 mm prosthetic head and polyethylene liner and another larger articulation between the polyethylene liner and the metal cup. Dislocation of the polyethylene liner and the consequent direct articulation between the prosthetic head and metal cup is recognized as intraprosthetic dislocation (IPD). This mode of THA failure is specific to dual-mobility implants. Despite the reduced incidence of IPD in modern dual-mobility implants compared to the early designs, iatrogenic IPD can occur during closed reduction of dislocated polyethylene liner-metal cup articulation. IPD requires timely diagnosis and early surgical intervention to minimize the necessity of major revision surgeries. This study presents a comprehensive review for dual-mobility-bearing THA, including the history and biomechanics, and focuses on the pathomechanics, diagnosis, and management of IPD.