What Is the Long-term (27- to 32-year) Survivorship of an Uncemented Tapered Titanium Femoral Component and Survival in Patients Younger Than 50 Years?

Abstract

Background: Uncemented femoral components in primary THA are in widespread use, especially in patients younger than 50 years, but few studies have evaluated their survival into the late third and early fourth decade.

Questions/purposes: We evaluated (1) survivorship using femoral revision for any reason as the endpoint, (2) survivorship using femoral revision for aseptic loosening as the endpoint, (3) survival in patients younger than 50 years, (4) cumulative incidence of stem revision for periprosthetic femoral fracture and (5) the overall risk of revision (change of any part of the implanted components) at a minimum of 27 years of follow-up with an uncemented tapered titanium stem still in clinical use today.

Methods: We reviewed the clinical and radiographic results of 326 THAs performed in 326 patients (for 28 patients with bilateral THA, only the first hip was included in the analysis to ensure independent observations) using an uncemented grit-blasted, tapered collarless titanium alloy (TiAl6Nb7) stem between January 1985 and December 1989. In that same timeframe, we performed 1038 primary THAs. During that time, we used cementless stems in patients without severe femoral canal deformity and adequate bone stock for uncemented femoral fixation as determined by using the indication criteria described by the developer. In all, 34% (354 of 1038) were cementless; all cementless stems implanted during that time were the stem being studied here. No others were used. The mean (range) age at the time of surgery was 56 years (13-81 years). Sixty-seven patients were younger than 50 years at the time of primary THA. A competing risk survivorship analysis was used to estimate long-term survival. The minimum follow-up was 27 years (mean 28 years; range 27-32 years); at that time, 169 patients had died, and four patients were lost to follow-up.

Results: Survivorship at 28 years with revision of the femoral component for any reason as the endpoint was 87% (95% CI 83 to 90). Survivorship for femoral revision for aseptic loosening as the endpoint was 94% at 28 years (95% CI 90 to 96). Survival in patients younger than 50 years at the time of primary THA was 89% (95% CI 78 to 95) and 95% (95% CI 86 to 98) at 28 years for the endpoints of all stem revisions and aseptic stem loosening, respectively. The overall cumulative incidence of stem revision for periprosthetic femoral fracture was 4% (95% CI 2 to 7) at 28 years. The overall THA survival rate at 28 years with revision for any reason as the endpoint was 57% (95% CI 51 to 62).

Conclusions: Uncemented femoral fixation of a tapered collarless titanium alloy stem was reliable into the early fourth decade, especially in patients younger than 50 years. Late stem failures in the third and early fourth decade were mainly because of periprosthetic femoral fracture, while aseptic loosening occurred in undersized stems during the early second decade.

Level of evidence: Level IV, therapeutic study.

Fig. 1

The photograph shows the uncemented straight titanium alloy (TiAl₆Nb₇) CLS Spotorno (Zimmer, Warsaw, IN, USA) femoral component with proximal fins and a grit-blasted surface finish.

Fig. 2

This flowchart demonstrates the distribution of hips at the final follow-up examination.

Fig. 3

This graph shows the competing risk survivorship curve and 95% CI with femoral revision for any reason as the endpoint. Twenty-eight-year survival was estimated as 87% (95% CI 83 to 90; 78 hips at risk).

Fig. 4

This graph shows the competing risk survivorship curve and 95% CI with femoral revision for aseptic loosening as the endpoint. Twenty-eight-year survival was estimated as 94% (95% CI 90 to 96; 78 hips at risk).

Fig. 5

This graph shows the competing risk survivorship curve and 95% CI with femoral revision for any reason as the endpoint in patients younger than 50 years at the time of primary THA. Twenty-eight-year survival was estimated as 89% (95% CI 78 to 95; 29 hips at risk).

Fig. 6

This graph shows the competing risk survivorship curve and 95% CI with femoral revision for aseptic loosening as the endpoint in patients younger than 50 years at the time of primary THA. Twenty-eight-year survival was estimated as 95% (95% CI 86 to 98; 29 hips at risk).

Fig. 7

This figure illustrates the distribution of radiologic osteolysis in zones according to Gruen et al. [12] and its mean area and SD at a minimum of 27 years of follow-up.