We describe two cases of breakage of expansion
cups in a CLS uncemented total hip arthroplasty without traumatic
etiology. Both cases occurred six years after the surgery
and none had breakage or polyethylene wear. We postulate
that the lack of contact between the polar area of the
cup and the acetabulum produces a zone of instability in the
segments of the prosthesis and increases the risk of fatigue of
the material. In our opinion acetabular revision is mandatory
in this situation, even in asymptomatic cases, because cup
rupture leads to implant loosening with secondary short-term
osteolysis.

We describe two cases of breakage of expansion
cups in a CLS uncemented total hip arthroplasty without traumatic
etiology. Both cases occurred six years after the surgery
and none had breakage or polyethylene wear. We postulate
that the lack of contact between the polar area of the
cup and the acetabulum produces a zone of instability in the
segments of the prosthesis and increases the risk of fatigue of
the material. In our opinion acetabular revision is mandatory
in this situation, even in asymptomatic cases, because cup
rupture leads to implant loosening with secondary short-term
osteolysis.