Fixation and loosening of the cemented Müller straight stem

Abstract

The original forged Müller straight stem (CoNiCr) has shown excellent ten- to 15-year results. We undertook a long-term survival analysis with special emphasis on radiological changes within a 20-year period of follow-up. In all, 165 primary total hip replacements, undertaken between July 1984 and June 1987 were followed prospectively. Clinical follow-up included a standardised clinical examination, and radiological assessment was based on a standardised anteroposterior radiograph of the pelvis, which was studied for the presence of osteolysis, debonding and cortical atrophy. Survival of the stem with revision for any reason was 81% (95% confidence interval (CI), 76 to 86) at 20 years and for aseptic loosening 87% (95% CI, 82 to 90). At the 20-year follow-up, 15 of the surviving 36 stems showed no radiological changes. Debonding (p = 0.005), osteolysis (p = 0.003) and linear polyethylene wear (p = 0.016) were associated with aseptic loosening, whereas cortical atrophy was not associated with failure (p = 0.008). The 20-year results of the Müller straight stem are comparable to those of other successful cemented systems with similar follow-up. Radiological changes are frequently observed, but with a low incidence of progression, and rarely result in revision. Cortical atrophy appears to be an effect of ageing and not a sign of loosening of the femoral component.

Systematic Review of Literature of Cemented Femoral Components: What Is the Durability at Minimum 20 Years Followup?

“…Kaplan-Meier survivorship at 20 years for the endpoint of revision of the femoral component for aseptic loosening ranged from 86% to 98% survival for studies reporting this data [8,14,16,22,23]. Even in the worst-case scenario analysis performed by Ling et al [16], in which all hips with unknown revision status at minimum 20 years were considered to be revised for aseptic loosening, Kaplan-Meier survivorship at 20 years was still 85.6% at the endpoint revision of femoral component for aseptic loosening.…”

“…The majority of these studies (10 of 13) were performed on the Charnley THA (Formerly Thackery, now DePuy, Leeds, UK, or Zimmer, Warsaw, IN, USA) with three additional long-term studies performed on the Harris Design-2 (Howmedica, East Rutherford, NJ, USA) [19], Exeter (Stryker, Newbury, UK) [16], and Müller straight stem (Zimmer, Winterthur, Switzerland) [8].…”

“…Only two studies speaking to our third research question (on surface finish) met our inclusion criteria [8,23]. These pertained to the Harris Design-2 (Howmedica) and the Müller straight stem (Zimmer, Winterthur, Switzerland), which have an average roughness (Ra) of 0.8 lm and 0.5 to 1.5 lm (mean, 1.0 lm), respectively, as opposed to the polished Charnley or Exeter stems in the remaining cohorts.…”

“…There were two different cohorts in this review that received a matte finished stem [8,23] as opposed to the polished Charnley or Exeter stems in the remaining cohorts. These stems were the Harris Design-2 (Howmedica) and the Müller straight stem (Zimmer, Winterthur, Switzerland), which have an average Ra of 0.8 lm and 0.5 to 1.5 lm (mean, 1.0 lm), respectively.…”

Cemented Müller straight stem total hip replacement: 18 year survival, clinical and radiological outcomes

“…Consciousness of the natural process of cortical atrophy is necessary in order not to overestimate the number of cases at risk, as cortical atrophy did not compromise the clinical and radiological results. Clauss et al [26] stated that cortical atrophy appears to be an effect of ageing and not a sign of loosening of the femoral component.…”