In Revision-THR the great variability of acetabular defects requires a revision-cup-system, which enables the surgeon to treat even extensive unexspected bone losses with a load stable reconstruction during the surgery.

For these cases a modular revision support cup (MRS-Titan) has been developed. It allows the reconstruction of the geometric rotation centre and prevents the applied autologous or homologous bone graft in the healing phase from overlaoding. Beyond that an individual adjustment of the differently large flexible straps guarantees the solid anchoring of the revision support cup to the vital bone. The individual anatomy can be preserved in every case of acetabular destruction due to the high range of modularity the system provides. Because of the intraoperatively synthesis of all parts of the MRS-cup the approach and the traumatization of the soft tissue can be minimized.

Since 1995 we implanted 95 MRS-Titan-cups out of 250 which were implanted world wide. In all cases a stable anchoring of the implant has been reached. We will report about our own follow-up and complications. In 4 MRS revisions a revitalized acetabular bone graft has been found able to host a noncemented hemispherical cup in three cases.

Conclusion: The MRS-System is able to bridge mechanically stable damaged or missing parts of the acetabulum and allows immediate partial loading. A solid bone remodeling can be achieved. The costs could be minimized by reduction of store-keeping and simple but well considered instruments.

A stem revision system was developed by a group of orthopedic surgeons and bioengineers. Implant specific instruments have been created to make the operation as easy as possible. The stem of the MRP prosthesis is conical and forged of a Titanium Aluminium Niobium alloy. It consists of 2 modular elements, a diaphysical and a trochantical part that can be supplemented by a head. Stem lengths from 140 mm and 200 mm are aviable with different length of diaphysical and prolongation elements so that each stem length could be realized in small steps. Also the anchoring of th diaphysical prosthesis elements in the bone makes a free construction of the total prosthesis to the femur with choice of the length and a variable adjustment of the rotation position of the neck of the femur prosthesis. Eight longitudinal ridges on the stem elements guarantee a rotation stability and the curved stems allow a reconstruction of the physiological antecurvation of th thigh also in case of fractures and segmental resections.

Since 1993 the members of the clinical working team implanted 1500 MRP prosthesis. We think that the best way for an optimal anchoring is the preservation of a great deal of the solid bone structures also in the section of the primary anchoring with partial bone resorption. The proximal anchoring of the femoral isthmus up to the middle third of the femur guarantees the most reliable long-term results. Indications for revision operations are given by resorptive bone defects up to a considerable bone loss on the proximal femur, for intraoperative stem fractures, for primary subtrochantar long distance fractures with simultaneous coxarthritis and for defect zones after bone tumor treatments. The very variable new design facilitates the revision operation and shortens the operation time.

The MRP prosthesis is able to bridge mechanically stable, damaged or missing parts of the proximal femur with revision operations and it makes an immediate partial loading possible for the patient. Defected zones of the bone fill with bone structures as a basis for the local anchored musculature. The modularity of the prosthesis lightens the revision operation.