Proximal Femoral Deformity
Daniel J. Berry
The most common reasons for total hip arthroplasty (THA) in the presence of proximal femoral deformity include posttraumatic conditions, previous proximal femoral osteotomy, developmental abnormalities, and metabolic abnormalities.
Proximal femoral deformities make THA more difficult because of the challenges in fitting a femoral component into the femoral canal, challenges in accessing the femoral canal, and challenges in creating optimal hip biomechanics to provide good function and hip stability.
Key goals of THA in the presence of deformity are (1) to avoid allowing the deformity to create circumstances that lead to poor hip biomechanics or (2) avoid problems with femoral component short- or long-term fixation.
Deformities may be categorized in different ways: according to the etiology, the anatomy of the deformity, or the location of the deformity.
For technical purposes the most valuable methods of categorization involve identifying the site of the deformity and the anatomy of the deformity. A practical method of doing this is to consider 3 main sites (levels) of deformity (Figure 18.1): proximal femoral deformity, subtrochanteric deformity (Figure 18.2), and more distal deformities (Figure 18.3). Each presents different challenges and can be treated differently.
Most proximal deformities can be managed with implants that allow satisfactory implant position and fixation despite the deformity or by using implants that allow the deformity to be excised.
Most more distal deformities, that is, those that occur below the stem tip level, can be ignored.
Subtrochanteric deformities are the most difficult to manage. Strategies for management, including use of special implants and corrective femoral osteotomies, are discussed in this chapter.
This chapter will not concentrate on 2 types of deformity that are covered in more detail elsewhere in this text: deformity mainly involving the greater trochanter (see Chapter 5) and rotational (anteversion) deformities of the femur (see Chapter 15).
Deformities mainly involving the greater trochanter typically are most problematic when the greater trochanter is positioned to impede access to the femoral canal. Such deformities when mild may be managed with femoral implants that can be inserted by more medial access to the canal, or for more severe deformities, with trochanteric osteotomy (conventional or slide) or extended greater trochanteric osteotomy (Figure 18.4) (both discussed in Chapter 23).
Rotational abnormalities of the proximal femur are most common in hip dysplasia, and management is discussed in detail in Chapter 15. Most can be managed with cemented components or uncemented components that provide for femoral component anteversion adjustment independent of the rotational relationship between the femoral metaphysis and diaphysis (such as modular stems or conical tapered fluted stems). Rarely derotational osteotomy is needed (discussed in this chapter).
Preoperative planning in proximal femoral deformity cases is essential to choose the best techniques to manage the specific deformity.
Routine hip instrumentation for the planned prosthesis (based on careful preoperative planning).
If diaphyseal femoral osteotomy is planned:
Small oscillating saw
Narrow ribbon retractors
Pointed and serrated jaw bone clamps
Figure 18.4 ▪ A, Radiograph of patient with proximal femoral deformity and greater trochanter overhanging the femoral canal. B, Postoperative radiograph after exposure using greater trochanteric osteotomy.
Cerclage wires or cables
Intraoperative radiography and/or fluoroscopy
Choose a femoral implant system that provides fixation in the proximal and distal fragments of the femur. This is essential to the success of the procedure. Typically, the component should be one that provides good rotational control of the proximal fragment with a triangle or sleeve that fits in the metaphysis and good rotational control of the distal fragment with flutes, very sharp corners, or extensive porous coating. Implants that have a round proximal geometry typically will not provide good rotational control of the proximal fragment. The implant chosen must be long enough to gain good fixation in the distal fragment below the planned osteotomy level.