Revision Total Hip Arthroplasty Via Extended Trochanteric Osteotomy

Scott M. Sporer, MD, MS

Wayne G. Paprosky, MD, FACS

Dr. Sporer or an immediate family member serves as a paid consultant to or is an employee of Smith & Nephew and Zimmer and has received research or institutional support from Central DuPage Hospital. Dr. Paprosky or an immediate family member has received royalties from Wright Medical Technology and Zimmer; is a member of a speakers’ bureau or has made paid presentations on behalf of Zimmer; serves as a paid consultant to or is an employee of Biomet and Zimmer; and serves as a board member, owner, officer, or committee member of The Hip Society.

INTRODUCTION

Total hip arthroplasty (THA) predictably provides pain relief and improved function in patients with degenerative hip arthritis. Despite the overwhelming success of THA, several situations necessitate the revision of the femoral implant. The extended trochanteric osteotomy (ETO) is an essential surgical tool for the revision arthroplasty surgeon. To obtain a successful surgical result during femoral revision, the femoral stem must be removed with minimal bone loss, the remaining host bone must be prepared without inadvertent perforation, and a femoral implant must be inserted concentrically with adequate axial and rotational stability. The ETO, which allows exposure of the proximal femur through a controlled cortical fracture, can facilitate these goals by allowing (1) improved access to the implant-bone or implant-cement interface, (2) concentric reaming of the distal femur in patients with proximal femoral deformity, (3) appropriate abductor tensioning, (4) improved acetabular visualization, and (5) predictable healing of the osteotomy. In general, an ETO should be performed if it is being considered as an option because this technique often will minimize surgical time and surgical complications and ultimately will minimize undersizing of the femoral implants, improve initial implant stability, and minimize the risk of cortical perforation. Familiarity with the ETO technique is crucial for surgeons who frequently perform revision THA or primary THA in patients with proximal femoral deformity.

PATIENT SELECTION

Indications

The most common indications for ETO include removal of a well-fixed femoral implant, removal of retained distal cement, insertion of a femoral implant in patients with proximal femoral remodeling, and the need for improved surgical exposure.¹

Removal of a well-fixed cemented, proximally coated, or extensively coated femoral implant can be very challenging. Indications for removing a well-fixed femoral implant may include sepsis; recurrent dislocation due to femoral implant malposition, inadequate offset, or both; an implant with damage from or a poor track record of excessive corrosion or fatigue failure; and the need to improve acetabular exposure.² Extensive bone damage can occur while attempting to remove a well-fixed implant because of 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 require a longer stem to bypass the stress riser (Figure 1).

The removal of well-fixed distal cement is equally challenging, especially when proximal femoral remodeling has occurred or the previous implant was cemented
into a varus position. Proximal exposure alone (with the femoral canal intact) has been shown to result in a higher prevalence of cortical perforation when removal of distal cement is attempted in such instances. The length of the ETO can be planned to allow easy visual access to the distal cement plug so that standard drills, taps, and curets can be used to disrupt the bone-cement interface and facilitate the removal of retained cement (Figure 2).

FIGURE 1 AP radiograph of the hip shows a well-fixed femoral implant with a fracture of the proximal modular neck.

FIGURE 2 AP radiograph of the hip depicts a loose femoral implant with severe femoral osteolysis. Note the large amount of well-fixed distal cement.

Proximal femoral varus remodeling is observed in up to 30% of patients with a loose femoral stem. Although implant extraction may be relatively easy in these patients, the subsequent surgical reconstruction often is challenging because of the deformed proximal bone. An ETO will allow concentric reaming of the femoral canal. Attempts to obtain distal fixation in a femur with proximal deformity will result in a high likelihood of cortical perforation, undersizing of the femoral implant, or varus malposition³^,⁴ (Figure 3).

Additional relative indications for an ETO include the need for improved acetabular exposure because of heterotopic bone formation (Figure 4) or the need to visualize both the anterior and posterior columns. An ETO also may be helpful during femoral revision in patients with severe trochanteric osteolysis, to minimize inadvertent fracture. Rarely, an ETO may be used in the primary setting in the patient with a prior osteotomy, malunion, or proximal femoral deformity due to congenital dysplasia.⁵

FIGURE 3 Intraoperative AP radiograph demonstrates varus proximal femoral remodeling. An extended trochanteric osteotomy at the apex of the deformity is required to allow concentric placement of a distally fixed implant.

FIGURE 4 AP radiograph of a hip following total hip arthroplasty shows severe heterotopic bone formation.

PREOPERATIVE IMAGING

Standard AP pelvis radiographs and AP and lateral radiographs of the femur are required for preoperative planning of an ETO. The AP pelvis radiograph can be used to estimate the limb-length discrepancy, and the AP radiograph of the femur can be used to determine the apex of the deformity in a varus-remodeled femur.⁶

VIDEO 60.1 Revision Total Hip Arthroplasty via Extended Trochanteric Osteotomy. Scott M. Sporer, MD, MS; Wayne G. Paprosky, MD, FACS (6 min)

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Video 60.1

PROCEDURE

Preoperative Planning

The length of the proposed osteotomy will depend on the surgical indication. Varus remodeling of the proximal femur occurs 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 implant alignment cannot be achieved in these situations from a proximal starting position. The inability to place a femoral implant in neutral position because of varus remodeling is termed a “conflict” (Figure 5). In these situations, the length of the ETO should extend at least to the apex of the deformity. Failure to reach the level of the deformity will necessitate the femoral preparation remaining in a varus alignment.

When the ETO is performed for removal of retained distal cement, the length of the ETO needs to be within a few centimeters of the distal cement plug (Figure 6). A shorter osteotomy can be performed if the indication is to improve surgical exposure or the distal cement mantle is loose; however, a sufficient length of cortical bone below the lesser trochanter is required to securely reattach the osteotomy fragment at the completion of the procedure. At least two cables are required to fix the trochanteric fragment securely at the completion of the procedure. In general, an ETO should be located a minimum of 14 cm below the tip of the greater trochanter.

The length of the osteotomy also depends on the implant chosen for the reconstruction. Preoperative templates are essential in determining the length of the osteotomy required 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 to obtain sufficient axial and rotational stability⁷ (Figure 7). If a tapered stem is chosen, it is important that the osteotomy does not extend past the distal metaphyseal/diaphyseal flare. Once the position of the osteotomy is determined, the location of the transverse limb is measured from a fixed bony landmark, such as the tip of the greater trochanter or the lesser trochanter.

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