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Consider an extended trochanteric osteotomy for the removal of well-fixed implants, for the removal of retained distal cement, and for patients demonstrating varus femoral remodeling.
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The length of the extended trochanteric osteotomy should be minimized to use the shortest femoral revision stem possible yet should be long enough to bypass the apex of the femoral remodeling, to achieve component and cement removal, and to allow at least two cerclage cables to be placed around the osteotomy.
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When levering the osteotomy anteriorly, multiple wide osteotomes should be used simultaneously to distribute the stress along the greatest distance.
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A prophylactic cerclage can be placed distal to the osteotomy before femoral preparation and stem insertion to minimize the risk of fracture.
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The osteotomy fragment should be advanced distally and posteriorly before it is secured to the remaining shaft of the femur. This will provide appropriate abductor tension and minimize the risk of impingement.
Total hip arthroplasty can provide predictable pain relief and improve function in patients with degenerative arthritis and is now recognized as one of the most cost-effective surgical interventions. Despite the overwhelming success and long-term reliability of total hip arthroplasty, several situations necessitate the revision of the femoral component. The use of an extended trochanteric osteotomy is a method that allows exposure of the proximal femur through the use of a controlled cortical fracture. This surgical technique is extremely helpful to facilitate the removal of a well-fixed femoral implant, to provide increased surgical exposure, and to permit concentric placement of a new implant. Familiarity with this surgical technique is crucial for surgeons who frequently perform revision arthroplasty or primary total hip arthroplasty in patients with proximal femoral deformity.
INDICATIONS
The most common indications for the use of an extended trochanteric osteotomy include removal of a well-fixed femoral implant; removal of retained distal cement; insertion of a femoral component in patients with proximal femoral remodeling; and improved surgical exposure ( Fig. 37-1 ).
Removal of a well-fixed femoral implant can be very challenging. Indications for removing a well-fixed implant include sepsis, recurrent dislocation due to femoral component malposition and/or inadequate offset, an implant with a poor track record, and the need to improve acetabular exposure. Extensive bone loss can occur during attempts to remove a well-fixed implant owing to the inability to disrupt the bone-prosthesis interface distally with proximal exposure alone. Although a cortical window can be helpful, this technique will weaken the remaining host bone and will require a longer stem to bypass the stress riser.
The removal of well-fixed distal cement is equally challenging. Isolated proximal exposure has been shown to result in a higher prevalence of cortical perforation during attempts to remove distal cement. The length of the extended trochanteric osteotomy can be planned to allow easy visual access to the distal cement plug such that standard drills, taps, and curets can be used to disrupt the bone-cement interface and facilitate the removal of retained cement.
Proximal femoral varus remodeling is observed in up to 30% of patients with a loose femoral stem. Although component extraction may be relatively easy in these patients, the subsequent surgical reconstruction is challenging because of the deformed proximal bone. The surgical options in patients with proximal femoral deformity include accepting the deformity and cementing a femoral component into the deformity, or performing an extended trochanteric osteotomy, which will allow concentric reaming of the femoral canal. Cementing a femoral stem into a varus remodeled femur is recommended only in a low-demand patient because of the poor results of cement femoral revisions. Attempting to insert an extensively coated stem in a patient with varus remodeling without the use of an extended trochanteric osteotomy will result in a high prevalence of cortical perforation, undersizing of the femoral component, and a varus malposition.
Additional relative indications for the use of an extended trochanteric osteotomy include the need for improved acetabular exposure because of either heterotopic bone formation or severe acetabular deficiencies requiring extensive visualization of the anterior and posterior column. An extended trochanteric osteotomy may also be helpful during femoral revision in patients with severe trochanteric osteolysis to minimize inadvertent fracture. Rarely, an extended trochanteric osteotomy may be used in the primary setting in patients with prior osteotomies, malunions, or proximal femoral deformity due to congenital dysplasias.
PREOPERATIVE PLANNING
Standard anteroposterior (AP) radiographs of the pelvis and AP and lateral radiographs of the femur are required for preoperative planning for an extended trochanteric osteotomy. The AP pelvis radiographs can be used to estimate the leg length discrepancy, and the AP radiographs of the femur can be used to determine the appropriate length of the osteotomy and determine the apex of the deformity in a varus remodeled femur. The length of the osteotomy will be dependent on the indication.
Varus remodeling of the proximal femur will occur in up to 30% of femoral revisions and is most frequently observed at the tip of a loose femoral stem. Because of the remodeling, neutral component alignment is unable to be achieved in these situations from a proximal starting position. The inability to place a femoral component in neutral position because of varus remodeling has been termed a “conflict.” In these situations the length of the extended trochanteric osteotomy should extend to the apex of the deformity. Failure to reach the level of the deformity will necessitate that the femoral preparation remain in a varus alignment.
When the extended trochanteric osteotomy is performed for removal of retained distal cement, the length of the extended trochanteric osteotomy will need to be within a few centimeters of the distal cement plug. A shorter osteotomy can be performed if the indication is to improve surgical exposure. However, a sufficient length of cortical bone below the lesser trochanter is required in order to securely reattach the osteotomy fragment at the completion of the procedure.
The length of the osteotomy is also dependent on the implant chosen for the reconstruction. Preoperative templates are essential in deciding the length of the osteotomy in order to obtain a stable implant. If an extensively porous-coated stem is used, a minimum of 4 to 5 cm of “scratch-fit” will be required in order to obtain sufficient axial and rotational stability. If a tapered stem is chosen, it is important that the osteotomy not extend past the distal metaphyseal-diaphyseal flare. Once the position of the osteotomy is marked, the length is measured from a fixed bony landmark such as the tip of the greater trochanter or the lesser trochanter ( Fig. 37-2 ).
