The results of uncemented acetabular components at followup times of 10 years and longer are dependent on a number of implant factors, including fixation ingrowth surface, adjuvant fixation, polyethylene fabrication, and polyethylene liner locking mechanism. This second-generation titanium fiber-metal-coated acetabular component had a new unique polyethylene locking mechanism and a polished, more congruent inner surface. In our previous report of 111 hips at 7 to 13 years, we noted no loosening or dissociation, no revisions for wear, and only two cases of pelvic osteolysis [19
]. We asked the following questions: (1) Is the risk of revision surgery for loosening, wear, or liner dissociation low with the second-generation acetabular component? (2) Is the rate of pelvic osteolysis low? (3) Can the liner be exchanged without bone cement?
This study has several limitations. First, we had no control group comparing these patients with the second-generation component with those having the first two versions of the first-generation titanium fiber-metal acetabular component. Second, 87 patients (39%) had died and 33 patients (15%) were lost to followup before 10 years. However, this is to be expected in a 10-year followup study. Third, we did not perform oblique pelvic radiographs or computerized axial tomography and the rate of pelvic osteolysis might be underestimated. Fourth, polyethylene wear measurements [21
] using digital techniques with computerized edge detection [2
] were not performed, because we did not have digital radiography. In our previous study [19
], we reported a difference in the rate of polyethylene wear between the two types of standard polyethylene (irradiated in air and irradiated in nitrogen gas) used with this component, and we did not repeat the analysis for this study. Fifth, we had a single observer for our radiographic findings and had no way to assess the reliability of our findings. A final limitation is that we did not measure the size of the osteolytic lesions on the plain radiographs, because we believe this would be unreliable.
A number of studies reported 10-year results of first-generation uncemented acetabular components [1
] (Table ). It is difficult to directly compare the results of those studies with the present study as a result of the lack of consistency in defining the cohorts, differences in followup time, and lack of survivorship data using the three end points defined in this study. In addition, none of the reported components is considered a second-generation component, and most, if not all, are not in use any more. Thus, the question of whether the design changes solved the problems can only be inferred by generally comparing the rates of shell revision and osteolysis. Our findings are similar to the two short-term followup studies of this second-generation component. Della Valle et al. reported the minimum 4-year results of 308 acetabular components (77% without screws) [9
]. Only one component was revised for aseptic loosening and pelvic osteolysis was seen in 12 hips (5%). The mean age of the patients in that study (64 years) was greater than the patients in the present study. In a subgroup of the same cohort study, 65 hips followed for a mean of 5.7 years, Della Valle et al. reported one case of pelvic osteolysis [8
]. In our study of 118 hips with the second-generation titanium fiber-metal acetabular component with a mean followup time of 12 years (range, 10–16 years), there were only two hips (1.8%) revised for symptomatic polyethylene wear and osteolysis and there were eight hips (7%) with pelvic osteolysis.
Uncemented acetabular component survival
Liner exchange for wear, recurrent dislocation, or at the time of femoral revision was effectively performed without cement in eight hips of this cohort. While we again note the difficulty of comparing the various series (Table ), these rates appear improved from the historical results with the first two versions of the titanium fiber-metal acetabular component.
Based on our observations, we question the need for new acetabular components with more expensive coatings, different polyethylene locking mechanisms, or monoblock (nonmodular) designs. Loosening did not occur with this titanium-fiber metal-coated component fixed with screws. Pelvic osteolysis was still seen with this acetabular component but at a very low rate at 10 to 16 years. However, this cohort used “conventional” polyethylene liners. The author continues to use this acetabular component for primary THAs but now uses highly crosslinked polyethylene liners in all patients.