Abstract
Introduction: From September 1999 to September 2000, 75 consecutive primary cementless total hip arthroplasties (THA) were performed by two surgeons. All acetabular components implanted were the Interop ™ shell manufactured by Sulzer Intermedics. In September 2000, due to unexplained early aseptic loosening of several acetabular shells, use of this component was abandoned by the authors. In December 2000 Sulzer recalled certain lot numbers of the component. This study examines the to date performance of this group of patients.
Methods: Of the 75 patients, 42 patients were identified as being in the recall group and 33 were not. Patients were seen at routine post-operative follow-up and as indicated secondary to pain. All patients were examined clinically and radiographically. Hallmarks of early failure were moderate to severe weight bearing start-up pain and a circumferential lucent zone (without a sclerotic line) seen best on the Lowenstein lateral view.
Results: The timing of the failure was early (less than 6 months from implantation). In the recalled group eight patients have undergone revision and five are pending revision, resulting in a 33% (13/40) failure rate. Of those patients undergoing revision surgery, seven were found to have loose prostheses. One patient was revised due to unexplained pain and was found to have a well-fixed component. His pain has subsided. In the non-recalled group one patient had pain beginning at six months post-operatively, and radiographic signs of loosening. At revision the prosthesis was found to be loose.
Discussion: The purported cause of this early aseptic loosening is attributed to a mineral oil residue left after manufacturing of the component, causing inflammation and inhibiting bone ingrowth. The failure and subsequent revision rate is expected to rise. Our experience to date indicates that patients in the recalled group and symptomatic patients in the non-recalled group need to be closely followed. This high incidence of early failure of a cementless acetabular component has never before been reported.
The abstracts were prepared by Nico Verdonschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, University Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
