Pattern of osteolysis around two different cementless metal-backed cups: retrospective, radiographic analysis at minimum 10-year follow-up.

In this retrospective study, we analyzed the formation of osteolysis with 2 cementless cups to evaluate if surface holes in metal shells influence the radiographic pattern of osteolysis. At a minimum of 10 years' follow-up, serial radiographs of 112 hips with Arthropor cups (having multiple shell holes) and 126 hips with Anatomic Medullary Locking (AML) cups (with no holes) were reviewed. Despite differences in variables other than cup design that can affect polyethylene wear and osteolysis rates, the incidence of osteolysis between the groups was coincidentally similar (47.3%, Arthropor; 47.6%, AML). The time of onset of osteolysis (mean, 7.5 and 7.4 years) also was similar. The radiographic pattern of the osteolytic lesions, which is largely a factor of cup design, differed. The Arthropor group had significantly larger lesions in Charnley zone I and significantly more hips with retroacetabular lesions (Charnley zones I and II); however, these lesions did not compromise cup stability. Patients with AML cups had more and larger lesions in the greater trochanter.