Fully Porous Coated Stems

Key Concepts

Meticulous preoperative planning and templating are essential to the success of revision femoral reconstruction using fully porous coated stems.
Liberal use of extended proximal femoral osteotomies will facilitate all aspects of femoral revision surgery and are invaluable in the management of any coexisting femoral deformity.
Following removal of the existing femoral implant(s), the patient’s femur must have at least 4 cm or more of supportive diaphyseal bone to achieve the necessary axial and rotational stability required for bone ingrowth.
- In the setting of more severe bone loss, alternative methods of reconstruction, such as fluted tapered stems, impaction bone grafting, allograft-prosthetic composites, or megaprostheses, should be considered.

Sterile Instruments and Implants

Surgical approach-specific hip retractors
Stem and/or cement extraction tools
Small saw blades, pencil-tip routers, osteotomes (for extended osteotomy)
Cerclage wires/cables/instruments (for prophylactic cerclage, osteotomy fixation)
Instruments and trial implants specific to the selected femoral component

Surgical Approaches

The surgeon must consider what is needed both to remove the existing implants and to insert the revision fully porous-coated stem, when making the final determination of surgical approach.
In the absence of significant deformity or the need to access the femur more distally (implant and/or cement removal), both the posterolateral approach and the direct lateral approach may be successfully utilized.
- In the presence of one or more of these features, the surgeon should have a very low threshold to perform an extended proximal femoral osteotomy.

Preoperative Planning

The intended hip center is first determined from an analysis of the acetabular side of the hip reconstruction. If the existing acetabular component is to be retained, the hip center will be unchanged; however, if the existing acetabular component is to be revised, the new hip center must be taken into account.
The existing femoral component planned for revision must then be assessed. If needed for deformity correction or for improved access to the distal femur (implants and/or cement extraction), an extended proximal femoral osteotomy should be planned (Figures 29.1 and 29.2).
- The length of this osteotomy must be planned to preserve the necessary 4 cm or more of supportive bone in the diaphysis.
  
  Figure 29.1 ▪ Preoperative anteroposterior (AP) radiograph demonstrating a loose femoral stem with significant varus remodeling of the proximal femur.
  
  Figure 29.2 ▪ Preoperative AP radiograph with a superimposed template demonstrating the extent of the deformity that will necessitate extended trochanteric osteotomy.
The stem diameter and stem length are then determined to best achieve diaphyseal contact over ≥4 cm (Figures 29.3, 29.4, 29.5).
- Most fully porous-coated revision stems are available in several lengths, with the longer devices typically also slightly curved to account for the natural femoral bow.

Figure 29.3 ▪ Preoperative AP radiograph of a patient with a debonded cemented stem, polyethylene wear, and progressive femoral osteolysis. Note the well-fixed cement more distally in the femoral canal.

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