Abstract
Background:
Metal-on-metal total hip arthroplasty (THA) implants have been widely debated due to the adverse wear issue related to the bearing surfacing. However, more recent studies have shown that the high metal ion problems that occur after surgery with this type of implant may not be exclusively related to the all metal bearing surfaces, but mainly due to the recently modified connecting tapers. Biomet is one of few companies who have not changed their original taper design for their THA implants. The purpose of this study was to present our up to eight-year clinical results.
Method:
Between November 2004 and April 2011, all of the 196 cases in 167 patients (77 male vs. 89 female) performed by a single surgeon were included in this study. The Biomet Magnum/Jumbo metal-on-metal total hip arthroplasty implants were utilized for all of the cases. The average age was 59 ± 11 years at the time of surgery. Thirteen patients deceased from causes unrelated to THA. The primary diagnosis was OA in 124 cases; followed by AVN in 41 cases, dysplasia in 12 cases and other causes in the remaining 19 cases. The average acetabular component sizes were 54 ± 4 mm. Clinical and radiographic examinations were performed prospectively, and the results were analyzed.
Results:
The mean duration of follow-up was 5 ± 2 years. There were four revisions: 1) one was due to an adverse wear issue with a cobalt level of 109 μg/l and a chromium level of 77 μg/l. The primary diagnosis was OA for this case. The acetabular inclination angle was 65°. The acetabular component was revised using the Biomet Magnum Tri-Spike component with the acetabular inclination angle of 41°; one year after the surgery, the metal ion level results showed a cobalt level of 2.4 μg/l and a chromium level of 9.7 μg/l with a Harris hip score of 100. This patient also has a total knee replacement on the same side. 2) one due to acetabular component loosening; the HHS was 100 two years after the revision 3) twodue to deep infection; the HHS was 93 at one year and 100 atbthree years after the revision correspondingly. The metal ion results were available for 114 patients at the time of this study. Four patients had metal ion levels ≥ 7 μg/l; three out of these four patients' levels were ≥10 μg/l and one out of these four had levels ≥15 μg/l. Using failure of any component as the end point, the Kaplan-Meier Survival rate was 99.5% at five years and 96.7% at eight years for the whole group.
Conclusions:
This study suggests that Biomet metal-on-metal THA showed a high success rate with a low adverse wear rate. Our clinical results may suggest that all metal bearing surfaces may not be the key to the recent adverse wear issue. The surgical technique and taper problems in other implants may be the major causes. Further studies need to confirm our results.
