Fluted Tapered Modular Stems

Nicholas M. Hernandez

Matthew P. Abdel

Key Concepts

Modular fluted tapered (MFT) stems have become popular in the last decade because of favorable reported results, ease of use, and versatility (Figures 30.1, 30.2, 30.3, 30.4).
Preoperative templating is essential for planning the diameter and length of the fluted tapered portion of the stem, as well as the length and offset of the proximal modular components.
A prophylactic cable around the femoral shaft may be utilized before preparation or implantation of the fluted tapered portion of the stem to minimize risk of failure. Hoop stresses are high during implantation.
Obtaining immediate axial and rotational stability with the fluted tapered portion is key to success and preventing implant subsidence or loosening.
The proximal modular portion of the component is used to optimize anteversion, length, femoral offset, and hip stability.
An extended trochanteric osteotomy (ETO) helps provide good exposure for optimal femoral canal preparation, especially when there is proximal femoral deformity, a large femoral bow, and/or overhanging greater trochanter (please see Section 1-B, Chapter 4). The ETO allows canal preparation under direct vision, creation of a well-reamed supportive cone of bone, and optimal axial and rotational stability of the implant. The goal is for a supportive cone of bone to support the tapered stem, not for the stem to wedge by 3-point fixation (which provides less support against subluxation and less surface area for bone ongrowth).
Intraoperative radiographs in orthogonal planes should be obtained with trial components in place, particularly to assess for diameter and length of the fluted tapered portion.
Modular fluted tapered stems can be used for most femoral revisions so long as femoral diaphyseal bone is sufficient to be reamed to a supportive tapered cone of bone that will provide good axial support and rotational stability of the implant (Figures 30.1, 30.2, 30.3, 30.4).

Sterile Instruments and Implants

Instruments

Routine hip retractors
Routine hip instruments to remove preexisting uncemented or cemented femoral components
Routine instrumentation for the fluted tapered stem
Small and large oscillating saw if ETO is required
Pencil-tip burr if ETO is required
Multiple wide osteotomes if ETO is required
Cerclage cables (one prophylactic cable and additional cables if ETO is required)

Figure 30.1 ▪ A, Radiograph of hip with loose subsided uncemented stem with good proximal bone. B, Radiograph after revision with mid-length modular fluted tapered stem. (Courtesy of Daniel J. Berry, MD.)

Implants

Trial and real fluted tapered stems of various diameters and lengths
Trial and real proximal bodies with various lengths and offsets
Appropriate femoral heads with the size and composition at the surgeon’s discretion
Dual-mobility implants may be considered in those patients at high-risk for postoperative dislocations

Figure 30.2 ▪ A, Radiograph of hip with well-fixed uncemented dual-modular neck stem and severe lysis due to taper corrosion. B, Radiograph after revision with mid-length modular fluted tapered stem. Note the stem obtained good axial and rotational stability distal to the osteolytic lesions and the ETO. (Courtesy of Daniel J. Berry, MD.)

Figure 30.3 ▪ A, Radiograph of hip with loose stem and damaged proximal bone. B, Radiograph after reconstruction with modular fluted tapered stem. (Courtesy of Daniel J. Berry, MD.)

Figure 30.4 ▪ A, Radiograph of hip with loose femoral component and notable proximal bone loss. B, Radiograph after reconstruction with long modular fluted tapered stem. The poor proximal bone has been bypassed, and the prosthetic axial and rotational stability is gained in the mid-diaphysis. (Courtesy of Daniel J. Berry, MD.)

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