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Chapter Synopsis
In this chapter, we review the indications and techniques for successful removal of the femoral components in revision total hip arthroplasty.
Important Points
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Before femoral extraction, a full workup is performed to assess component loosening.
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Cortical bone stock of the femur is evaluated preoperatively.
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An extended trochanteric osteotomy (ETO) is used to minimize bone loss and prevent perioperative fracture.
Clinical/Surgical Pearls
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The ETO should expose a large segment of bone to enable reattachment.
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Extraction of the femoral implant should preserve all bone stock for reconstruction.
Clinical/Surgical Pitfalls
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Diaphyseal bone stock is key to fixation in future revisions using tapered stems.
Introduction
Total hip arthroplasty (THA) has a success rate of more than 97% and provides significant improvement in functional status. The increased number of THAs among younger patients has produced an upsurge in revision surgery rates. This chapter discusses the indications, presurgical evaluation, and surgical techniques for femoral implant removal in revision THA.
Indications and Contraindications
Indications for removal of a stem depend on the stability of the implant. In patients with pain and a mechanically unstable femoral implant, revision requires extraction of the femoral stem. Femoral components can be retained during acetabular revision surgery if the following conditions are met: stable fixation, appropriate offset and anteversion, maintenance of acceptable hip stability, ability of the taper trunnion to accept a new femoral head, and implant availability if outdated implants were used. Use of the dual-mobility system allows retention of monoblock implants or femoral implants when larger femoral heads are not available.
Equipment
The equipment needed for femoral revision includes a high-speed bur with a metal-cutting tip, a gigli saw, trephines, osteotomes, cerclage wires or cables, femoral extraction devices (e.g., Universal extractor, slap hammer, vice grip), and bone hooks. Equipment for removal of cemented implants includes many types of curettes (e.g., reverse curettes, Moreland cement hook) and ultrasonic cement removal systems.
Surgical Techniques
Approach
The approach to the hip may be determined by the prior operation or the surgeon’s skill and comfort level. We prefer the posterior approach for revisions, but anterior and anterolateral approaches also have been described for revision THA. Previous skin incisions can be used when adequate exposure can be obtained for implant and cement removal.
Examination and Imaging
During preoperative planning for revision surgery, all records of previous procedures and prior radiographs should be reviewed. The type of femoral neck, trunnion or taper is especially important if the femoral implant will be retained and a new femoral head placed.
The preoperative clinical examination and determination of the onset of hip or thigh pain can help to ascertain whether an implant is loose. Start-up pain and thigh pain have been associated with loose femoral stems in patients undergoing revision THA.
The full workup includes anteroposterior and lateral full-length femur radiographs and an anteroposterior radiograph of the pelvis. Serial radiographs may provide the strongest evidence of implant stability. Nuclear scintigraphy is rarely necessary but can help to determine femoral stability in patients with no radiographic signs of loosening. Computed tomography (CT) can assess the bone stock available for safe removal and eventual hip reconstruction.
Bone stock assessment includes an inventory of areas with cancellous bone loss, a thick cement mantle, or a thin cortex that may be susceptible to perforation or that may complicate extraction. The original cementation technique and cement–bone interface should be evaluated before extraction in the revision procedure. Remodeling of the femur may be observed in cases of loose stems that have fallen into a varus position. Varus remodeling may necessitate an osteotomy for correction.
An extended trochanteric osteotomy (ETO) is indicated to improve visualization for implant and cement removal and to avoid iatrogenic fracture of the greater trochanter. The distal aspect of the stem or cement mantle is measured, and anatomic landmarks such as the greater trochanter can be used intraoperatively to determine the ETO position.
The anterior bow of the femur should be assessed to preclude perforation of the anterior cortex during implantation of the revision implant. The length of the femur should be templated, and the measurement should allow at least 4 cm of femoral diaphyseal cortical fit for a cylindrical revision implant or 2 cm of fit at the isthmus for long, tapered implants.
Procedure
The hip should be exposed with care to protect the sciatic nerve, which may not be in the normal location or may be encased in scar. The release should include removal of previous scar to fully mobilize the femur. Standard release of the gluteus maximus tendon should be considered. Adequate exposure is essential to prevent unanticipated bone loss or fracture. When considering an ETO, retention of the anterior extent of the vastus lateralis muscle and perforating blood vessels ensures adequate perfusion to promote healing.
For previously cemented stems, the decision to remove cement depends on the technique being considered for subsequent revision reimplantation. Two techniques can be used for removal of a cemented implant: removal of the femoral stem without disruption of the cement mantle and removal of the femoral stem with partial or complete extraction of the cement–bone interface. Some smooth stems that have been implanted for many years can be removed without altering the cement mantle. Repeat cementation may be considered for smooth femoral stems that are easily removed without fracture of the cement mantle (“tap in, tap out”). This technique can prevent fracture or bone loss during removal of the cement, and removal of the smooth stem can aid exposure for revision of the acetabular component.
Some surgeons recommend roughening the femoral cement mantle to allow integration. A femoral stem that is shorter and thinner than the previous stem should be inserted during this procedure to allow an adequate new cement mantle to bond with the old cement. Studies have reported a 98% to 100% success rate up to 15 years after use of the cement-in-cement technique for femoral reimplantation. Despite being less invasive than cement removal, perioperative proximal femur fracture and femoral shaft perforation have been reported.
The type of stem and the method and location of fixation are determined before surgery. A cemented or well-fixed, ingrowth, press-fit stem can be removed by many methods. Specialized tools are available to disengage the stem without invasive exposure techniques. After dislocation of the femoral implant, the femoral head is removed from the trunnion. It is important to remove all soft tissue to prevent a false sense of stability with a loose stem. The stem should be manually assessed for motion after the bone–implant interface is visible. A loose stem may be amenable to manual removal. A gentle tap on the loose stem may help to completely dislodge it.
Regardless of the tools used for extraction of the femoral stem, the proximal femoral metaphysis should be disengaged from the surrounding cement or bone. Flexible osteotomes can be used on the anterior and posterior cortices. A back-and-forth motion should be used to prevent wedging of the osteotome or levering of the cortex, leading to fracture. The osteotome should be pointed at the implant and skirted along the edge to prevent fracture of the metaphysis. The shoulder of the implant should be disengaged using a curved osteotome. The last area that must be inspected is the calcar–prosthesis interface. Care must be taken to disengage the calcar without fracturing the proximal metaphysis. A pencil-tip bur can be used to safely remove the cement–bone interface.
Several extraction techniques can be used for stems that are well fixed or cemented. After the proximal body is disengaged from the metaphysis, extraction can be attempted with a vice grip with or without an attached slap hammer. The lateral proximal body should be cleared of all soft tissue and the greater trochanter protected during removal of the femoral component. If the manufacturer’s insertion devices are available, an insertion device can be screwed into the femoral component and back-slapped. A third option for removal of the femoral stem is a bone hook inserted into the shoulder of the implant through a hole. An offset punch can be impacted under the neck to remove the femoral stem, especially for smooth, cemented stems.
For stems that cannot be removed using these techniques, a cortical window can be made distal to the femoral stem. Preoperative measurement of the length of the stem from the tip of the trochanter assists in identifying a location distal to the femoral stem. A small cortical window can be opened using an osteotome and the distal stem visualized. An offset bone tamp can be used to impact the stem. The distal femur can be protected with a cerclage cable if the cortical window propagates distally. The femur can also be protected with a long reconstruction stem spanning the cortical window during revision. The cortical window can be reattached to its original location after femoral stem extraction.
Cement removal can be difficult if the proximal femoral metaphysis is intact. Preoperative templating of previous areas of cement fixation allows assessment of the cement mantle, cement restrictors, and thin outer cortex. Care must be taken to prevent femoral fracture and perforation of the femoral cortex during extraction. After removal of the femoral stem, the cement mantle is addressed. The proximal cement can be chipped away using osteotomes, with care taken not to perforate the cortex. The distal cement plug can be removed by drilling through the cement restrictor and using a Moreland cement hook to extract the plug in a retrograde fashion.
Alternative tools can be used for cement removal in revision THA. Ultrasound devices convert electrical energy to mechanical dynamic stress waves. This vibration causes friction when it contacts the bone–cement interface, preferentially affecting the cement. However, the friction can cause heat, and the increased temperature may lead to complications. The high temperatures have been shown in cadaver models of the humerus to reach dangerous levels around the radial nerve. In hip revision surgery, vibration in proximity to the sciatic nerve may lead to an elevated temperature and nerve damage. Methods for protecting the cortex and surrounding tissue include irrigation, intermittent pausing, and judicious use of the ultrasound machine.
An ETO is recommended for well-fixed, uncemented components; extensive cementation; and femoral deformity. Preoperative assessment of femoral loosening helps to define the necessary equipment for implant removal and the need for an ETO. Measurement of the femoral stem length on radiographs allows accurate placement of the distal osteotomy. The ETO is a separate exposure from the other techniques described, including the trochanteric slide osteotomy and standard trochanteric osteotomy, which do not include the metaphyseal portion of the femur.
At the inception of total hip surgery, early surgeons such as Sir John Charnley routinely used a trochanteric osteotomy for primary THA. The ETO for revision THA was popularized by Peters and Paprosky more than 20 years ago. The use of a controlled osteotomy helps to prevent cortical perforation and fracture of the femoral shaft during stem extraction. Femoral shaft deformity prohibiting distal cement removal also may require an ETO. This method has become a successful alternative when removal of a femoral stem is difficult in the revision setting.
The previous skin incision, except anterior skin incisions, is used for the ETO exposure. After identification of the femoral head and neck, greater trochanter, and lesser trochanter, the distal aspect of the femur is exposed to the measured length of the stem. The hip is placed in internal rotation, and the vastus lateralis is dissected along its posterior border. The key for adequate blood supply and proper healing is to retain the abductors and vastus lateralis attachment to the osteotomy fragment. The osteotomy is marked from the base of the posterior greater trochanter to the distal aspect of the intended osteotomy. The osteotomy then is marked just anterolateral to the linea aspera, leaving a soft tissue sleeve for repair. The trochanteric osteotomy should measure approximately one third of the circumference of the femoral shaft involving the posterolateral portion of the femur.
Several techniques can be employed to create the osteotomy in a safe, controlled fashion. A pencil-tip bur can be used to make cortical perforations along the anterior and posterior lateral osteotomy site. The perforations are then connected with a saw, pencil-tip bur, or osteotome. An osteotome is placed on the proximal femur to complete the osteotomy anterior and posterior to the greater trochanter. The osteotomy site can then be levered open by stacking osteotomes. Figure 47.1 shows the femoral stem still engaged after displacement of the posterior ETO fragment. The implant or cement mantle can be disengaged from the cortex with flexible osteotomes at the cement–bone or implant–bone interface. The medial interface often is intact, and a gigli saw can be used to disengage the medial cortex. A distal cerclage cable should be placed distal to the osteotomy site to prevent propagation of a fracture from the osteotomy site during cement removal or revision implant placement.
