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Abstract
Background The long-term results of uncemented total hip arthroplasties vary widely due to differences in design, metal alloy, coating, surface structure, and porosity.
Patients and methods We retrospectively studied 75 cementless Zweymüller SL stems in combination with Endler titanium-backed threaded cups (Z-E) in 70 patients. 35 patients were women, and the mean age at surgery was 52 (24–68) years. 16 patients died and 1 emigrated, 7 patients (of which 1 later died) subsequently underwent revision, and the remaining 47 patients with 50 original arthroplasties were followed up after a median of 16 (15–18) years.
Results Revision of 8 hips resulted in an 18-year Kaplan-Meier estimated overall survival rate of 88% (CI: 79–96). 6 of 7 cup revisions were due to liner wear and osteolysis, and 1 was due to aseptic loosening. 2 of 3 stem revisions were due to femoral loosening and 1 was due to fracture of the neck of the stem. The clinical results were good, with a mean Harris hip score of 89 (54–100). Half of 70 hips in 65 patients had ectopic bone formation. All unrevised implants were radiographically stable, with a mean liner wear of 0.07 mm/year.
Interpretation These long-term results demonstrate that the combination of a Zweymüller SL stem and an Endler titanium-backed screw cup is a good hip arthroplasty in young and active patients. A prefixed polyethylene liner is a drawback, necessitating exchange of the whole cup in cases with polyethylene wear.
Contributions of authors
OR: planning and execution of the study, collection and analysis of data, and writing of the manuscript. PS: planning and execution of the study, and collection of the data. MR and BE: contributed to the interpretation of the data and the statistics, and to the preparation and revision of the manuscript.
No benefits have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.