The Cemented Stem

CHAPTER 17 The Cemented Stem







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:










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.




Mar 9, 2016 | Posted by in Reconstructive surgery | Comments Off on The Cemented Stem

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