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The ACS® total knee system includes cementless and cemented femoral and tibial components in 5 sizes each. The tibial polyethylene inserts are available in 5 thicknesses. Due to the highly congruent contact area a retaining or scarifying of the posterior cruciate ligament can be performed.
Since the beginning of 2006 the semi constrained version ACS® SC is available to perform revisions or treat patients with insufficient collateral ligaments and bone loss.
To resurface the femoro patellar joint there are cementless and cemented patella components. The ACS® total knee system was designed to minimize the problems of wear of the polyethylene within the implant in order to provide maximum longevity of the prosthesis.
Cobalt Chromium alloy is the material of choice for the femoral and tibial component because of its optimal wear characteristics and mechanical properties. Adding a Titanium Nitride coating contributes to further reducing the wear of the polyethylene component and at the same time the risk of metal allergic reaction is reduced.
Wear of polyethylene has been acknowledged as the major cause for implant failure [2,3,4,5]. Wear tests performed at the University of Munich (Prof. Dr H.J. Refior and Dipl. Ing. J. Huber) [1], show superior wear characteristics when Cobalt Chromium alloy is combined with a ceramic Titanium Nitride coating. The design of the ACS® /CCI® has proven its advantages in terms of wear characteristics compared to a non-coated prosthesis.
The optimal femoral-tibial congruency provided by the ACS® protects the polyethylene from wear and damage during millions of cycles. Furthermore, the contact stress is reduced by perfectly matching articulating radii in three planes. This principle distributes loads over a large area [1].
Literatur
1. Huber J., Refior H, J. wear test, Ludwig Maximilians-Universität München Labor für Biomechanik und Experimentelle Orthopädie, Germany, 2002 data on file.
2. Feng E.L., Stulberg S.D., Wixson R.L. Progressive Subluxation and Polyethylene wear in total knee replacements mit flat articular surfaces. Clin. Orthop. and Rel. Res, 299, Feb. 1994.
3. Eng G.A., Dwyer K.A., Hanes C.K. Polyethylene Wear of Metal Backed Tibiakomponentes in Total and Unicompartmental Knee Prostheses. J. Bone Joint Surgery, 74-B;9, 1992.
4. Lewis P., Rorabeck C.H., Bourne R.B., Devane P, Posteromedial Tibial Polyethylene Failure in Total Knee Replacements. Clin. Orthop. and Rel. Res, 299, Feb. 1994.
5. Collier J, Mayor, M.B., McNamara, J.L., Suprenant, V. A., Jensen, R.E., Analysis of the failure of 122 Polyethylene Inserts from unzementpflichtig tibial knee components, Clin. Orthop and rel research, 273, December 1991.
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