The possibility for developing much higher stresses at the shell-bone or liner-shell interface, also it decreased range of motion before impingement compared to the non-constrained component with possible adverse effects on polyethylene wear and osteolysis. Various modes of failure were reported; Type I: in the shell-bone interface, Type II: in the shell-liner interface, Type III: the locking mechanism, Type IV: bipolar-femoral head interface. In primary hip arthroplasty, its incidence has been reported to be between 0.6% and 9.9%. With revision surgery, it can be as high as 20%.