INDICATIONS AND CONTRAINDICATIONS

Cemented femoral stems can be considered for any patient who requires a hip arthroplasty. Force-closed or taper-slip designs have generally given better results than shape-closed implants.¹ In complex cases in which there is distortion of the anatomy, femoral shortening procedures and derotation osteotomies can be carried out. The osteotomy sites should be cleared of cement or protected from cement intrusion by the use of impacted bone chips. Cemented hemiarthroplasties or cemented femoral components in total hip arthroplasties are indicated for displaced fractures of the femoral head. In cases of previous septic arthritis of the hip, cement can be loaded with an appropriate antibiotic to reduce the risk of recrudescence of infection.

Other than an active ongoing infection there are no specific contraindications to the use of cement fixation in any patient for whom a hip arthroplasty is indicated.

PREOPERATIVE PLANNING

Preoperative planning is essential to help the surgeon identify the size, offset, and depth of insertion of the femoral prosthesis. This can be performed on the traditional films or on digitized picture archiving and communications system (PACS) films using appropriate software. It is important to ensure that the correct magnification is used for templating. The true offset is shown when the radiograph is taken with the hip internally rotated.

For templating of conventional radiographs:

1. Using the concentric rings on the templates, the center of the femoral head is marked.

2. The desired offset of the stem is then identified. The templates are placed on the radiographs with the stem in the middle of the femoral canal. The offset that reproduces the patient’s anatomy (center of prosthetic head overlying or closest to the center of the femoral head) is chosen (Figs. 17-1 and 17-2).

3. If the patient’s offset is between the prosthetic offset ranges available, the series of stems with the closest offset is chosen. Plus or minus heads can be then used to fine tune the offset. Leg length is determined by the depth of insertion of the implant with the correct femoral head and is therefore independent of the choice of stem and neck length.

4. The stem size is identified by sequentially using templates with the femoral head and prosthetic head aligned. The maximum size with a 2- to 3-mm cement mantle is chosen.

5. The template is placed behind the radiograph with the prosthetic head overlying the femoral head and the stem centered in the canal. The outline of the neck, shoulder, and stem is drawn over the radiograph. The distance between the tip of the trochanter and shoulder of the prosthesis is marked and noted. This insertion level will reproduce the patient’s anatomy and will achieve the correct leg length.

FIGURE 17-1 Template of implant with inadequate offset.

FIGURE 17-2 Template of stem with correct offset.

TECHNIQUE

The longevity of the femoral stem depends on establishing adequate initial mechanical interlock between the implant and the bone. A stable interface and osseointegration of the cement has been described in the long term.² With cemented stems, a satisfactory interface is achieved by creating a “closed cavity” and then using contemporary cementing techniques to introduce and pressurize cement. By applying pressure on cement from initial injection up to the moment polymerization is complete, good cement intrusion into bone is ensured and blood is prevented from accumulating at the interface. A closed cavity is obtained by occluding the distal femoral canal with a plug. The strong cancellous bone that remains after broaching is thoroughly lavaged, and the canal is then filled in a retrograde fashion with the use of a cement gun. The proximal opening of the canal is sealed to allow the cement to be pressurized by continued use of the gun through the seal. Application of pressure is continued until the femoral component has been inserted and the cement has fully polymerized.

The femur can be approached and prepared for cementing by any of the routine surgical exposures of the hip. For the operative technique described here the posterior approach is used.