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Pattern of Osteolysis Around Two Different Cementless Metal-Backed Cups: Retrospective, Radiographic Analysis at Minimum Ten-year Follow-up

Authors

Alexandra M. Claus, MD, PhD** Christi J. Sychterz, MS* Robert H. Hopper, Jr., PhD* Charles A. Engh, MD*

*Anderson Orthopaedic Research Institute, Alexandria, VA 22307
** Fakultaet fuer Klinische Medizin der Universitaet Heidelberg, Klinikum Mannheim gGmbH, Orthopaedische Universitaetsklinik, Mannheim, Germany

Abstract:

In this retrospective study we analyzed the formation of osteolysis with two cementless cups to evaluate if surface holes in metal shells influence the radiographic pattern of osteolysis. At minimum 10-year 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 which can effect polyethylene wear and osteolysis rates, the incidence of osteolysis between the groups was coincidentally similar (47.3%, Arthropor; 47.6%, AML). Surprisingly, the time of onset of osteolysis (mean 7.5 and 7.4 years, respectively) was also similar. However, 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.

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