Bipolar prostheses subassembly and bipolar prostheses assembly

A bipolar prosthesis subassembly comprising:

• an outer shell;
• an inner liner configured to dispose inside of the outer shell in a manner of non-interference fit, the inner liner is provided with a circumferential groove;
• and
• a split lock ring configured to elastically snap into the circumferential groove of the inner liner,
• wherein the inner liner defines a sphere-shaped cavity defining an equator, the circumferential groove of the inner liner extends from a first position below and in proximity to the equator to a second position above the equator and tapers from the first position to the second position, the split lock ring is movable in the circumferential groove between an assembly position and a locking position along the longitudinal axis, in the assembly position, the split lock ring can be expanded to an inner diameter lager than an outer diameter of a femoral head so that the femoral head can be inserted into the sphere-shaped cavity, in the locking position, the split lock ring elastically returns to an inner diameter less than the outer diameter of the femoral head so as to securely hold the femoral head in place inside the inner liner.