Long-Term Results Using the Anatomic Medullary Locking Hip Prosthesis
C. Anderson Engh, Jr., MD; * Alexandra M. Claus, MD, PhD;** Robert H. Hopper, Jr., PhD;* and 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
To be published in Clinical Orthopaedics and Related Research, December, 2001.
Summary: At mean 13.9-year followup, the overall loosening rate for femoral components was 3% (seven of 204) for Anatomic Medullary Locking femoral components and 5% (11 of 204) for Anatomic Medullary Locking acetabular components, indicating long-term durability of these components. The results also raised questions regarding the relationship between osteolysis and loosening of components.
Since the introduction of cementless total hip arthroplasty in the early 1980s, concern has shifted from component loosening toward polyethylene wear and osteolysis. The current review of 223 consecutive unselected Anatomic Medullary Locking femoral and acetabular components extends the followup on a series of patients previously reported on at 5 and 10 years. The purposes are to describe the reasons for revisions and to assess the onset and size of osteolytic lesions, with the hypothesis that osteolysis represents an important cause of loosening.
The population included 211 hips (204 patients) with mean followup of 13.9 years (range, 2-18 years). Among them, 129 hips (122 patients) had minimum 15-year followup. Minimum 2-year radiographs with a mean radiographic followup of 12.2 years (range, 2-18 years) were available for 204 hips (197 patients). Of the entire study group, 39 hips (38 patients) had 44 component revisions, increasing the number of revisions by 24 since this series was reported previously.
Twenty-six patients (27 hips) had their first revision surgery more than 10 years after the primary surgery. The most common reason for revision of original components was wear or osteolysis occurring in 22 of the 39 hips (21 of 38 patients).
The overall loosening rate for components at mean 13.9-year followup was 3% (seven of 204) for femoral components and 5% (11 of 204) for acetabular components. Twenty-four percent of hips (48 of 204) had evidence of femoral or pelvic osteolytic lesions larger than 1.5 square centimeters. Of note, osteolysis was not associated with any case of femoral loosening, whereas seven of the 11 loose acetabular components were associated with pelvic lesions larger than 1.5 square centimeters. The results indicated that the relationship between osteolysis and component loosening remains to be defined.
This research was funded, in part, by Inova Health Care Services, Virginia.