Head material influences survival of a cemented total hip prosthesis in the Norwegian Arthroplasty Register

Abstract

Background: High prosthesis survival is reported for total hip prostheses with metal and alumina heads, but direct comparisons of a single prosthesis design with one of two different head materials has seldom been studied. Prostheses with zirconia heads are less commonly used than metal and alumina heads, and the few reports suggest variable results with zirconia heads.

Questions/purposes: We therefore asked: (1) Would metal heads provide better survival of a cemented total hip arthroplasty (THA) than alumina heads? (2) Would metal heads provide better survival of a cemented THA than zirconia heads?

Methods: We searched in the Norwegian Arthroplasty Register for cemented primary THA cup/stem combinations that simultaneously had been used with different head materials. The only THA that fulfilled these inclusion criteria was the cemented Reflection All-Poly/Spectron EF (cup/stem) that had during 2001 to 2006 been used both with alumina (n = 448) and cobalt-chromium (n = 5229) heads; that implant had also been used with zirconia (n = 275) and cobalt-chromium heads (n = 3195) during 1997 to 2003, and we included patients with this THA from these two time intervals in the study. All cups were conventional polyethylene. We estimated prosthesis survival and relative revision risks adjusting for age, sex, and diagnosis. The followup in the two study materials was until December 2010.

Results: The survival at 8 years of the Spectron EF/Reflection THAs, inserted with alumina and cobalt-chromium heads during 2001 to 2006, was 92.3% and 94.0%, respectively. The Reflection/Spectron EF THA had inferior survival with zirconia heads compared with cobalt-chromium heads (relative risk, 1.7). At 12 years, the survival rate was 88.1% with cobalt-chromium heads and 74.8% with zirconia heads.

Conclusions: Alumina femoral heads provided no advantage over cobalt-chromium heads on midterm prosthesis survival. THAs with zirconia heads had inferior survival.

Level of evidence: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Fig. 1

Survival curves (Cox) are shown of Spectron EF/Reflection THAs according to femoral head material (CoCr or alumina) adjusted for age, sex, and diagnosis with any revision as the end point. The survival with this end point was not affected by the choice of alumina or CoCr heads. Prosthesis survival with alumina and CoCr heads at 8 years was 94% and 92% (p = 0.84), respectively.

Fig. 2

With aseptic cup loosening as the end point, survival curves (Cox) are shown of Spectron EF/Reflection THAs according to femoral head material (CoCr or alumina) adjusted for age, sex, and diagnosis. Prosthesis survival with alumina and CoCr heads at 8 years was 94% and 98% (p = 0.003), respectively.

Fig. 3

Survival curves (Cox) are shown of Spectron EF/Reflection THAs according to femoral head material (CoCr or zirconia) adjusted for age, sex, and diagnosis with any revision as the end point. Prosthesis survival with zirconia heads was inferior to the survival with CoCr heads. At 12 years, the survival rates were 88% and 75% (p = 0.002) with CoCr and zirconia heads, respectively.

Fig. 4

With aseptic cup loosening as the end point, survival curves (Cox) are shown of Spectron EF/Reflection THAs according to femoral head material (CoCr or zirconia) adjusted for age, sex, and diagnosis. Prosthesis survival with zirconia heads was inferior to the survival with CoCr heads. At 12 years, the survival was 92% and 75% (p = 0.003) with CoCr and zirconia heads, respectively.