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Modular, Fluted, Tapered, Grit-Blasted Titanium Stems for Femoral Revision
CASE STUDY
A 75-year-old woman presented with a loose cemented stem ( Fig. 65.1 , A ). Evaluation of the radiographs showed that despite appropriate overall bone quality, osteolysis had compromised the bone stock down to the isthmus. Confronted with this Paprosky type IIIB femoral deficiency, it was decided to revise the femur with a modular, fluted, tapered, grit-blasted titanium stem (Revitan, Zimmer, Warsaw, Ind.) (see Fig. 65.1, B ). After the loose stem was extracted, an extended trochanteric osteotomy was performed to facilitate removal of the remaining well-bonded cement mantle and to enable safe and straightforward preparation of the area of primary fixation. A cerclage wire was added prophylactically around the distal femur first. The cup was revised, and a 40-mm head was chosen to reduce the risk of postoperative dislocation.
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Chapter Synopsis
The use of a modular, tapered, fluted, grit-blasted titanium stem for femoral revision is an attractive option. These titanium stems are versatile, provide excellent primary stability, and offer unequaled performance in the setting of major femoral defects. After careful preoperative planning, a cone is prepared in the femoral canal to accept the taper of the stem, and the proximal part is built to obtain appropriate stability and leg length. An extended trochanteric osteotomy (ETO) can be used to facilitate extraction of the previous stem and safe insertion of the new stem. Long-term functional and mechanical results are excellent.
Important Points
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Preoperative planning is an extremely important part of the operation.
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The decision to perform an ETO should be made during surgical planning because of its effect on the level of fixation of the stem.
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Taper fixation is the goal to obtain primary diaphyseal stability.
Clinical/Surgical Pearls
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An ETO is commonly performed to facilitate extraction of the previous stem and to ensure safe insertion of the new stem.
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A larger stem is preferred to a longer one, provided there is adequate bone stock at that level.
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A more aggressive taper should be considered to obtain fixation below the isthmus.
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A guidewire and intraoperative radiographs should be used routinely to rule out a perforation.
Clinical/Surgical Pitfalls
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Three-point fixation should not be the primary mode of fixation of the implant.
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Wedging the definitive implant stem and body significantly higher than the reamer suggests proximal three-point fixation.
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Distal perforation of the anterior cortex can be caused by using a stem that is too long.
Introduction
Approximately 50,000 revision hip arthroplasties are performed each year in the United States, and this number is expected to double by 2030. Fifty percent of these procedures require a revision of the femoral component. Cementless femoral revision prostheses have demonstrated favorable survivorship and clinical performance over the long term. Two uncemented stem designs—the modular, tapered, fluted, grit-blasted titanium stem and the monobloc, cylindrical, diaphyseal, porous-coated cobalt-chrome stem —are frequently used, and both have proponents and opponents. Tapered components have gained attention in North America after having enjoyed popularity in Europe for more than 2 decades based on the work of Wagner and others.
The increased popularity in North America is based on the many mechanical advantages of tapered, fluted titanium stems. The prosthesis obtains axial stability through the wedging effect of the taper in the femoral canal and excellent rotational stability as a result of the flutes rigidly engaging the femur throughout the circumference of the stem. The modularity of some designs allows versatility and fine-tuning of fixation, leg length, and stability. Titanium reduces the amount of stress shielding and facilitates proximal bone restoration. These mechanical advantages have been verified by Böhm and Bischel and Weiss and colleagues, and Richards and co-workers have described excellent clinical outcomes. Due to their versatility, these stems are more suitable than cylindrical, diaphyseal, porous-coated stems in cases with femoral deficiencies that extend beyond the isthmus. Paprosky and asociates failed to demonstrate adequate results with diaphyseal, porous-coated stems for such demanding femoral deficiencies. Despite these advantages, the use of tapered, modular stems requires precise knowledge of the surgical technique, implant nuances, and technical pitfalls.
Indications and Contraindications
Tapered revision stems are indicated for revisions of failed cemented and uncemented femoral components when proximal metaphyseal bone does not provide enough support to use a modular, proximally coated, uncemented stem, such as the S-ROM (DePuy, Warsaw, Ind.). Indications include Paprosky type II, IIIA, IIIB, and IV femoral deficiencies and Vancouver type B2 and B3 periprosthetic femoral fractures.
Medical conditions rendering a major surgical procedure inappropriate and ongoing infection are contraindications. There must be adequate quantity and quality of distal femoral bone to enable axial and rotational stability of the tapered stem. If not, a modular oncology system or allograft prosthetic stem should be considered.
Equipment
In addition to the equipment necessary for revision surgery and the extraction of components in situ, we recommend having a high-speed bur, wires or cables, and the complete kit for implantation of the components chosen. Blood should be available, and a cell saver may be used at the discretion of the surgeon, although our experience suggests that there is insufficient blood loss to retransfuse after the cell saver is primed. The surgeon can also consider the adjuvant use of a tranexamic acid infusion to reduce blood loss and transfusion risk.
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