Cemented Stems
Joseph M. Statz
Rafael J. Sierra
Key Concepts
Choosing a cemented stem over an uncemented stem is largely surgeon preference in the majority of patients.
There are 2 main different design principles by which cemented stems work. Both design principles are based on obtaining fixation at the cement-bone interface through cement interdigitation with cancellous bone. However, fixation at the cement-stem interface differs.
The composite beam concept utilizes a stem with a roughened or textured surface that allows cement interdigitation with the stem, creating a solid beam composed of bone, cement, and stem.
The taper-slip concept utilizes a highly polished, tapered stem with a smooth surface that allows fixation without cement interdigitation but obtains axial stability with its tapered shape and rotational stability with its cross-sectional shape.
Advantages of cemented stems:
Survivorship: Excellent long-term survivorship in clinical series and registries
Versatility: Can be used in any case
Decreased perioperative fracture risk
Fixation with antibiotic cement may decrease infection rates
Polished stems may be easily removed from cement mantle, simplifying some revisions
Forgiving technique: Basic principles should be followed regardless of stem type; the goal is to implant the stem in appropriate alignment with a solid 2-mm cement mantle surrounding the entire stem
Disadvantages of cemented stems:
Increased operating room time compared with uncemented stem
Cement in the femoral canal can be difficult to remove at revision
“Cement implantation syndrome” caused by the pressurization of the femoral canal and fat emboli
Sterile Instruments and Implants
Routine hip retractors
Pulse lavage irrigator with femoral stem attachment
Epinephrine-soaked sponges
Cement plug
Vacuum cement mixer
Cement gun with long nozzle and pressurizing attachment
Cemented femoral component (with instrumentation)
Positioning
Positioning depends on surgeon preference for primary total hip; the author utilizes a posterolateral approach for primary and revision total hip arthroplasty (THA).
Surgical Approaches
Cemented components can be inserted through any THA approach, although this is more difficult through a direct anterior approach. Please refer to Chapters 2, 3, 4, 5.
Preoperative Planning
Template femoral component size. For cemented stems, 2 mm of cement mantle surrounding the implant is preferred, but certain cement philosophies (“French paradox”) have shown good results with less than that.
Template and clinically examine preoperative leg length discrepancy.
Choose and template an appropriate acetabular component.
Bone, Implant, and Soft Tissue Techniques
Perform the desired approach to the hip joint.
The technique described here is for the preparation and placement of a taper-slip design but can be used as a guide for placement of all cemented stems.
Perform the femoral neck osteotomy using templated preoperative plan as a guide. For a polished tapered designing a precise neck cut is less important; however, too short of a neck cut should be avoided.
Prepare and implant an appropriately sized and positioned acetabular component. This can also be done before or after femoral preparation (per surgeon preference).
Establish a femoral entry point (surgeon preference is the use of a round 6.5-mm burr), usually over the posterolateral aspect of the neck (Figure 11.1).
An AO canal finder is used as a starter to find the trajectory of the femoral canal (Figure 11.2).
Subsequent hand reaming is performed orienting the femoral stem away from varus and flexion in line with the center of the femoral canal (Figure 11.3).
Hand ream to open the canal and lateralize the starting point as needed. This helps avoid varus stem alignment, which is associated with a higher rate of loosening.
Broach the canal to the templated size, making sure to leave sufficient circumferential cancellous bone (at least 2 mm) around the canal for cement interdigitation (Figure 11.4). Work broaches against the lateral bone to avoid varus alignment. The final broach should be in line with the native femur with
respect to varus/valgus and flexion/extension with about 15° to 20° of anteversion, but optimal alignment will also depend on the patient’s native femoral version and hip stability achieved at the time of trialing the hip. The final broach should be sized to be against strong cancellous bone, which is typically near the cortex, but not so large as to have removed all the cancellous bone and be directly against the cortical bone.
Figure 11.1 ▪ A starting point for femoral stem entry can be established with a burr or box osteotome. This should generally be in the posterolateral quadrant of the cut surface of the femoral neck.
Figure 11.2 ▪ An AO starter reamer is used to palpate the canal and establish a trajectory straight down the femoral canal for subsequent reaming and broaching.
Figure 11.3 ▪ The femoral canal is reamed to an appropriate size, ensuring that 2 to 3 mm of circumferential cancellous bone is preserved in the canal. Note that the reamer is directed away from varus and flexion (A) and the canal will redirect the reamer down the canal as it is advanced (B). A posterior approach was utilized.
Place a cement restrictor down the canal. The depth of insertion can be determined by comparison with the real stem and marking the cement restrictor inserter with a marking pen at the level of the calcar. The cement restrictor should be placed about 1 cm distal to the tip of the stem (Figure 11.5).Related posts:
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