Femoral Component Removal

CHAPTER 40 Femoral Component Removal






Revision total hip arthroplasty (THA) consists of three basic steps. First, the hip joint must be exposed adequately using the surgical approach that is most familiar to the surgeon and best suited for the procedure. Second, previous components must be removed safely and with minimum host bone loss, and the joint cavity must be débrided to remove foreign material. Third, new components must be implanted in a mechanically stable configuration, followed by wound closure.


The overall goal of revision THA is to perform each of these steps as efficiently as possible while minimizing surgical trauma to the patient. Each step, its complexity, the time invested in completing it, and the challenges encountered can vary dramatically from one operation to the next and are influenced by the skill of the surgeon. With this background, the goal of this chapter is to present a framework to accomplish femoral component removal during revision THA as efficiently and safely as possible.





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).



Extraction tools that can help pull the femoral implant out of the canal include modular femoral head and neck detachment devices and femoral stem extractors. Universal femoral extractors for modular and nonmodular components and special extractors that insert into a hole in the prosthesis or fit tightly around the prosthetic femoral neck can greatly facilitate implant removal and save operative time. In addition to extractors, a set of long-handled bone punches with and without offset built into the instrument should be available to impact the stem against the collar (if any) and assist in stem extraction (Fig. 40-2).


Mar 10, 2016 | Posted by in Reconstructive surgery | Comments Off on Femoral Component Removal

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