RM Pressfit – Cementless monoblock press-fit cup
Today, most surgeons use press-fit cups for hip arthroplasty. The RM Pressfit Cup is based on a proven concept of elasticity and particle coating and provides the following outstanding properties:
- The implants are made completely of UHMW-PE. The thus achieved modulus of elasticity of about 1'000N/mm2 is very similar to that of the human bone.
- An optimal primary stability and a reliable secondary stabilisation – the oversizing at the cup's equator ensures an optimal primary press-fit fixation of the implant in the acetabulum (fig. 1). This minimizes movement between the implant and the bone and provides the physiological conditions necessary for the osseointegration of the implant. The combination of an optimal primary stability, minimised movement and osseointegration provides the mechanism for the secondary fixation. This is the basis of a durable implant. The proven titanium-powder coating enhances this objective.
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 Fig. 1 |
- The elliptical design and a slight polar flattening (fig. 2) permit secure placement of the cup into the acetabulum without early jamming.
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 Fig. 2 |
- A reproducible surgical technique and user-friendly instruments – the few instruments and operating steps guarantee a reproducible and easy technique.
- An implant for minimal invasive implantation – the monoblock implant with specially developed instruments (preparation of the acetabulum, placement and impaction of the cup) is particularly suitable for minimal invasive implantation (fig. 3-5).
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 Fig. 3: MIS impactor |
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 Fig. 4: MIS universal post-impactor |
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 Fig. 5: MIS Post-impactor with brim |
A development of our proven RM Classic Cup
With a mean survival rate of 94.4 % after 20 years11, the RM Classic Cup ranks among the most successful acetabular cups. The RM Classic Cup is made of UHMW-PE and its elasticity is therefore very similar to that of bone. The non-interconnected, but individually anchored particles characterise the thin coating and have no structural stiffness of their own. The elasticity of the UHMW-PE body of the cup provides the elastic behaviour to the acetabular cup. This ensures that the biomechanical behaviour of the acetabular cup in the acetabular zone remains physiological after implantation.
The following table includes the survival rates of the RM Classic Cup from different publications, registered data and lectures. Compared to the results of the Swedish hip register, the medium and long-term results of the RM Classic Cup are among the best of all the documented cups.
Survival rates of the RM Classic Cup in percent after a number of years
(In brackets are the survival rates exclusively for aseptic loosening, as far as available)
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The latest publication of Ihle et al11 reports a survival rate of aseptic loosening of 94.4 % after 20 years.
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 click to enlarge |
11 Ihle M., Mai S., Pfluger D. H., Siebert W.; The results of the titanium-coated RM acetabular component at 20 years. A long-term follow-up of an uncemented primary total hip replacement, JBJS (Br) 2008; 90-B: 1284-1290
Proven concept of elasticity and particle coating
The biomechanical investigations show the important role that the concepts of elasticity and of particle coating play in these outstanding clinical results.
The RM Pressfit Cup persists in carrying on the concepts of the elasticity and of the particle coating.
Concept of elasticity
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 By R. Mathys senior: Isoelastic hip endoprostheses. Hans Huber publishers, 1992 |
The modulus of elasticity of UHMW-PE is very similar to that of the human bone, as the following table shows.
Concept of particle coating
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 RM Pressfit Cup with TiCP coating |
The particle coating prevents the direct contact between the bone and the polyethylene and guarantees an optimal biological compatibility. In addition, the microstructure of the coating improves the mechanical compound of the cup and the bone. The RM Pressfit Cup coated with TiCP is remarkable for its bio inertness and the well known capacity of osteointegration of titanium, which is due to the outstanding corrosion resistance and the spontaneously forming surface oxide film.
Pure titanium particles (TiCP) are used as coating material. The warmed titanium-powder particles get hot pressed into the polymer surface of the acetabular cup. This guarantees that the cup material does not experience any structural change and that the coating material remains unchanged. The resulting particles are individually anchored in the UHMW-PE substrate.
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 Macroscopic picture of the TiCP coating |
Implants
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The RM Pressfit Cup for 28 mm articulations is available in diameters of 46 to 64 mm in 2 mm increments. The diameters of 52 to 64 mm in 2 mm increments are available as well for 32 mm articulations. These acetabular cups can be used with heads of stainless steel, CoCrMo or Bionit®2.
The metal-on-metal (metamys®) RM Pressfit Cup for 28 mm articulations is available in diameters of 46 to 64 mm, for 32 mm articulation it is available of 52 to 56 mm and for 36 mm articulation it is available of 56 to 64 mm. One should combine these acetabular cups exclusively with the metal-on-metal (metamys®) heads of Mathys Ltd Bettlach.
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 4.0 mm Special Screw |
Special 4.0 mm screws are available if the RM Pressfit cup requires an additional fixation.
Reference clinics
Prof. Boisgard & Dr Levai
CHU - 58 rue Montalembert
FR-63003 Clermont-Ferrand CEDEX 1
Dr Guido Giussani
Ospedale G. Salvini
V. le Forlarini 121
IT-20020 Garbagnate Milanese (MI)
Dr Alec McAuslan
Southern Cross Hospital
232 Wairau Road
NZ-Auckland
Dr Thilo John
Universitätsklinikum Charitè
Campus Benjamin Franklin
Hindenburgdamm 30
DE-12200 Berlin
Dr Peter Kägi
Regionalspital Langnau
Dorfbergstrasse 10
CH-3550 Langnau im Emmental
Literature
Other innovative products
Our company has several other innovated products which are not
published on this website. Please refer to your Mathys contact person
for further information.