Comparison between straight- and curved-stem M�ller femoral prostheses

Abstract

Between 1977 and 1982, 545 cemented femoral prostheses were implanted, in combination with a noncoated cementless polyethylene acetabular component (RM cup). Three hundred and eighty-one straight-stem and 76 curved-stem Müller femoral components were implanted, as well as 88 collared components with a 130-mm stem and a 130 degrees neck-shaft angle, derived from a long-stem steel prosthesis. Survivorship analysis of revisions for aseptic loosening at 10 years revealed 97% straight-stem survival, 91.6% curved-stem survival, and 88.3% 130 degrees stem survival. "Survival" curves were also constructed for radiological loosening, and the survival rates (patients without radiological evidence of loosening) were 69.8%, 78.8%, and 63.1% respectively at 10 years. The 130 degrees collared stem was associated with significantly less acetabular loosening than the other prostheses. This resulted in less calcar resorption, but there was a higher rate of stem loosening. Acetabular loosening and associated wear products appear to be responsible for calcar resorption, and stress shielding of the calcar appears to be of minor importance in the pathogenesis of aseptic stem loosening. Better cementing techniques have improved survivorship of the curved-stem prosthesis, and early fears of high rates of radiological loosening with the straight stem have not been substantiated.

Subsidence of titanium straight stems in combination with highly viscous bone cement

“…Good results were also reported in other studies with shorter follow-up examination intervals [11,22,25]. Generally, a high rate of subsidence of up to 50% or 56% and a rate of osteolysis up to 10% is attributed to the chromiumcobalt straight stem design [22,25]. Other studies with chromium-cobalt stems report distal radiolucent lines without reference to osteolysis [6,11].…”

“…In another institution for the same stem, two loosenings in 126 stems were reported after 9.1 years [1]. These results are better than those of a control group with chromium-cobalt stems from the same hospital [25]. However, a 10% rate of osteolysis and a 30% rate of subsidence were also observed [1].…”

“…In other studies, a 15-year survival rate of 88% and a 10-year survival rate of 94% were found for the chromium-cobalt design [7,19]. Good results were also reported in other studies with shorter follow-up examination intervals [11,22,25]. Generally, a high rate of subsidence of up to 50% or 56% and a rate of osteolysis up to 10% is attributed to the chromiumcobalt straight stem design [22,25].…”

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

“…The Müller straight stem was designed to achieve a press fit fixation in the anteroposterior radiological view with a self-centering effect (shape-closed). A close stembone contact is established in the coronal plane, resulting in a thin or even incomplete cement mantle [1,12,13] which has been described in the literature as the "French paradox" [13] . It is well known that it is desirable to have a complete cement mantle around the stem [14] .…”

“…There are no data for third-generation techniques (jet lavage, vacuummixed cement) and it must be questioned whether these techniques can further improve the cement penetration for an implant with high introduction forces. The use of ceramic heads was associated with a decreased wear rate and the use of modern bearing surfaces might further improve survival [10,12,13] . The use of a femoral seal or finger-packing might improve the proximal sealing and reduce access of polyethylene particles at the interface, thus reducing the risk of osteolysis for the Müller straight stem.…”