INDICATIONS

Femoral component removal is the extraction of the metal stem from the intramedullary femur, where it will be firmly fixed to bone by osseous ingrowth, fibrous tissue, or an intervening layer of bone cement. With fibrous ingrowth the femoral stem may demonstrate motion relative to the femur but may still require additional dissection in order to be safely removed from bone.

The indications for femoral component removal during revision THA, with or without acetabular component removal, are varied. These reasons include hip instability, aseptic loosening, deep sepsis, component failure, prosthesis impingement, periprosthetic fracture, bearing wear, periprosthetic osteolysis, and failure of modular connections.

CONTRAINDICATIONS

Femoral component removal (and revision THA) is contraindicated in the setting of medical illness or severe comorbidities that preclude any major surgical intervention. In such situations, alternative treatments must be considered. For example, bracing for hip instability, chronic suppressive antibiotics for infection, conservative management or limited internal fixation of periprosthetic fractures, and assistive devices such as wheelchairs, walkers, or crutches for debilitated patients with aseptic loosening and osteolysis are alternatives that can help selected patients who are deemed unsuitable for major surgery.

The relative contraindications to removing the femoral component during revision THA are the finding of a well-fixed femoral stem, in the absence of deep sepsis, and severe component malpositioning. In such instances, replacing proximal modular subcomponents, such as the femoral head or modular neck segment, is preferable if limb length and soft-tissue tension can be restored.

TECHNIQUE

Preoperative Planning and Preparation

Independent of surgeon experience, preoperative planning, team communication, and adequate preparation will determine the efficiency of femoral component removal. These steps cannot be overemphasized. The specific goal of preoperative planning is to anticipate and plan for the worst-case scenario during the revision procedure.

Every successful revision total hip procedure requires careful planning and templating based on preoperative radiographs obtained with high-quality equipment, and in sufficient view to demonstrate the pathology. For femoral component revision, an anteroposterior (AP) view of the pelvis and AP and lateral views of the femur are the minimum radiographs required for planning. The radiographs of the femur should include the entire prosthesis and the distal extent of any existing bone cement in the femur. Because revision usually requires a longer implant, it is best to have the entire femur included on radiographs to understand the normal curvature of the femoral shaft, the structural integrity of the bony cortex, and the shape and dimensions of the canal.

Radiographs and clinical history are ideally reviewed in a team conference. This conference should include all key personnel who will participate in the procedure. At a minimum, this will include the surgeon, the surgical assistants who will help during the procedure, and the implant representative. Preferably, the circulating staff, the scrub technician, and the anesthesia staff should be aware of the anticipated duration and complexity of the operation, the expected blood loss, and the need for special equipment, bone grafts, and intraoperative fluoroscopy.

Old femoral implants should be identified using stickers or operative reports from the previous operation. Experienced implant representatives can be a very good resource in accomplishing this. If there is any doubt whether the entire femoral stem will need to be removed, then proximal subcomponents specific to the stem design should be available, such as modular neck pieces and femoral heads compatible with the specific taper dimensions. The tools and equipment needed to remove the old femoral implant should be reviewed at this planning session, along with the stem design to be implanted, bone grafts, and other augments required for reconstruction.

Proper planning and communication are critical components of the revision procedure. A properly educated support staff and implant representative can communicate details of the procedure to the operating room staff and can contribute greatly to a smooth and efficient procedure. Details of the planning session should be captured in writing, preferably using a standard form, such that all members of the operative team have access to this information.

Tools and Specialized Equipment

Once the mode of fixation (i.e., cemented stem versus porous ingrowth) has been identified, the proper tools for the stem removal should be anticipated. With few exceptions the Moreland cemented and cementless revision sets (DePuy, Warsaw, IN) are sufficient for most femoral revision procedures. Similar sets of hand-held instruments are made by other implant companies and can be used with equally effective results..

In some cases, power tools may be necessary for safe femoral stem extraction, and representative examples are available from Anspach (Lake Park, FL) and Midas Rex (Fort Worth, TX). Special courses are available to teach surgeons the proper technique for using these high-speed, low-torque tools that are very useful in some revision THA procedures. Power oscillating and reciprocating saw blades in various small sizes can be used very effectively to quickly develop a plane between the proximal femur and the implant.

Ultrasonic tools are sometimes useful for removing cement from the intramedullary femoral canal.¹ Specially designed tool tips convert electrical energy to mechanical energy that is concentrated at the cement mantle, thereby breaking it down. When cortical bone is contacted instead of cement, auditory and tactile feedback can prevent canal perforation.^2,³ Because more force is required to break cortical bone than cement, the ultrasonic system is generally safe, and this has been validated clinically.⁴ Limitations include a learning curve and the expense of purchasing or renting the ultrasonic equipment. If the equipment is not available, alternatives to removing retained cement in the femoral canal include the use of hand tools, facilitated by an extended osteotomy of the femoral canal that can expose the entire cement mantle.

In some revision procedures the existing cement mantle may have separated from the femoral cortices and fragmented into loose pieces. In such situations, one removal strategy is to introduce new cement into the femoral canal that can bond to the old cement and remove it in 1- to 2-cm–long segments with an extraction rod anchored in the new cement mantle (Fig. 40-1). If indicated, this strategy requires the availability of special equipment (SEG-CES, Zimmer, Warsaw, IN).