RECONSTRUCTION 2023, Jan, 08 | 12:00 am

The Cemented Femoral Stem

Indications

  • Relative indications for a cemented femoral stem include:

    • Smaller, less active patients

    • Dorr type C femoral canals

    • Osteopenic bone

    • Prior sepsis in which the use of antibiotic-impregnated cement is desired

      Examination/Imaging

  • The preoperative evaluation should first include a thorough history and physical examination. Particular attention should be given to note any previous operations on the affected hip, leg length discrepancy, or history of cardiopulmonary medical problems.

  • Proper radiographs must be obtained, including anteroposterior (AP) pelvis, AP hip, and lateral hip radiographs. Note significant deformity, osteopenia, or leg length difference.

  • Carefully template the position of the cup and femoral stem on all views (Fig. 1). Choose a femoral implant that will allow a circumferential cement mantle of 2–3 mm.

 

 

 

 

FIGURE 1

 

 

 

149

 

Cemented Femoral Stem

 

FIGURE 2

 

Surgical Anatomy

  • A key landmark for the femoral neck osteotomy is the lesser trochanter. This cut is typically made 1.5–2 cm proximal to the lesser trochanter.

  • The piriformis fossa (Fig. 2) is the anatomic starting point for entry of the femoral stem into the canal, and its identification is critical for producing a well-aligned implant with a good cement mantle.

    Positioning

  • Hypotensive anesthesia improves visualization by reducing blood loss during the operation and facilitates excellent cement-bone interdigitation by minimizing back-bleeding from the cancellous bony surface of the proximal femur.

  • Regardless of approach, the patient should be positioned directly lateral on the operating table. If the table position changes during the operation, the surgeon must be cognizant of the position of the patient’s pelvis throughout the operation.

 

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P ITFALLS

  • Because of the overlying abductors, the direct lateral and anterolateral approaches may make exposing and accessing the piriformis fossa starting point more difficult. The end result moves the entry point of the femoral stem anteriorly, producing a cement mantle defect anteriorly and proximally as well as posteriorly and distally (Fig. 3).

 

Cemented Femoral Stem

 

Portals/Exposures

  • The procedure may be done through the posterolateral, anterolateral, direct lateral, or transtrochanteric approach.

     

    P EARLS

    • If the tip of the canal finder does not pass easily, the entry point is likely wrong. If too medial a starting point is chosen, the tip of the instrument will be placed in varus and will contact the lateral cortex. If too anterior a point is chosen, the tip of the instrument will contact the posterior cortex and an anterior cement mantle defect will result.

       

      P ITFALLS

    • Proper entry of the femoral canal can be a problem in obese patients and patients operated on through the lateral and anterolateral approaches.

     

    FIGURE 3

     

    Procedure

    Step 1: Femoral Head Resection

  • Preoperative planning and templating should guide selection of the level for the femoral neck osteotomy.

  • The level of the osteotomy is marked using the femoral neck osteotomy guide (Fig. 4).

     

     

     

     

    FIGURE 4

     

    151

     

    Cemented Femoral Stem

     

    Step 2: Opening the Medullary Canal

    • Open the medullary canal through the cortical bone overlying the piriformis fossa using a trocar awl or rongeur.

    • Working posterolaterally will allow proper placement of the femoral stem by allowing the most direct path to the femoral diaphysis.

       

      P ITFALLS

      • Failure to remove this lateral bone will result in medial placement of the femoral stem and varus alignment.

       

    • A T-handle canal finder is inserted into the proximal femur to a depth that approximates the length of the femoral stem. Care is taken to insert the instrument through the same posterolateral starting point, and it should pass easily into the femur.

      Step 3: Preparation of the Proximal Femur

    • Bone overlying the lateral femoral neck and any medial bone of the greater trochanter impeding direct passage to the femoral canal is removed with a box osteotome (Fig. 5A and 5B). Alternatively, a lateralizing reamer may be used to accomplish this.

       

       

       

      A

       

      B

       

       

       

       

      FIGURE 5

       

      152

       

       

      P EARLS

      • With cemented femoral stems, it is important to maintain a rim of cancellous bone to allow for cement interdigitation. This means not trying to fit the largest broach size possible, as in cementless implants, which would leave only cortical bone and result in a less optimal cement mantle.

       

      Cemented Femoral Stem

       

      Step 4: Broaching

  • Femoral broaches are then sequentially inserted, being sure to apply constant pressure posteriorly and laterally to avoid stem malalignment (Fig. 6A and 6B). Care should be taken to control the desired amount of version with each successive broach inserted.

  • Preservation of at least 3 mm of cancellous bone medially and anteriorly is recommended (Fig. 7). If there is little remaining cancellous bone, downsize the femoral component.

  • After the final broach is placed, the broach handle is removed and a trial reduction is performed. When stability and limb length have been properly restored, the hip is dislocated and the version of the stem is marked on the medial femoral neck with electrocautery or a marker. Trial components are then removed.

     

     

    A

    B

     

     

    FIGURE 6

     

     

     

    153

     

     

    P EARLS

    • Have several sizes of cement restrictor plugs available. Attempting to insert a plug that is too large may result in fracture of the femur. If necessary, radial slits may be made in the outer plastic rings to decrease the hoop stresses created when inserting the plug.

       

    • The most important factor in obtaining good cement interdigitation with the remaining cancellous bone is proper cleansing. Carefully performed pulsatile lavage is the key to obtaining this result.

     

    Cemented Femoral Stem

     

    FIGURE 7

    Step 5: Final Preparation of the

    Medullary Canal

    • A femoral brush is used to remove any debris or loose pieces of cancellous bone.

    • Selection of a cement restrictor is based on the size of the femoral canal (Fig. 8A and 8B). Sounds included in the instrumentation may be used to determine canal diameter and the size of the distal stem centralizer. The cement plug should be at least 2 mm larger than the largest sound that passes and

       

      A

      B

       

       

      FIGURE 8

       

       

       

      154

       

      Cemented Femoral Stem

       

      FIGURE 9

       

      is placed approximately 1.5–2 cm distal to the tip of the femoral stem (Fig. 9).

  • The proximal femoral bone is then thoroughly cleansed with a pulsatile lavage system with a long nozzle, spraying perpendicular to the long axis of the femur (Fig. 10A and 10B). The remaining cancellous

 

 

 

B

 

 

FIGURE 10 A

 

 

 

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Cemented Femoral Stem

 

A B

FIGURE 11

 

bone is irrigated until no blood or marrow tissue remains, which facilitates cement interdigitation and subsequent pressurization of the cement mantle (Fig. 11A and 11B).

  • After a thorough lavage, the canal is suctioned completely dry, and the cement prepared in step 6 is immediately introduced.

    Step 6: Cement Mixing

  • The surgeon and the operating room team should be familiar with the behavioral characteristics of the cement being used as well as with the equipment used to prepare the cement.

  • Cement is mixed in a container under vacuum or with a centrifuge. Typically, two 40-mg packages of cement are mixed for a femoral stem. Occasionally patients with extremely wide “stovepipe” femurs will require three to four packages of cement to fill the canal.

  • In patients with prior sepsis or with diabetes mellitus, or patients on chronic steroid therapy, consider using antibiotic-impregnated cement.

    Step 7: Cement Application

  • Cement behavior is dependent on the room temperature and humidity, as well as the type of cement and any additives.

 

156

 

 

 

Cemented Femoral Stem

 

FIGURE 12

 

P EARLS

  • Alerting the anesthetist prior to cement application allows him or her to prepare for any change in the patient’s hemodynamic status during this time.

     

    P ITFALLS

  • The surgeon should be aware of any screw holes or cortical defects that were the result of prior hardware or preparation of the femur for the stem to prevent cement extrusion into the soft tissues.

 

  • In general, a medium-viscosity cement is preferred. When the cement delivered from the nozzle tip has lost its sheen and does not stick to the surgeon’s glove, it is ready for application.

  • The cement is delivered in a retrograde manner, starting just above the cement restrictor (Fig. 12). Care is taken not to bury the nozzle tip within the advancing cement, as this can create voids in the

    mantle.

     

  • After filling the femur, the cement is pressurized by applying the proximal femoral seal and continuing to deploy cement. Cement is delivered in a slow, steady manner over 2–3 minutes. Appropriate pressurization is evidenced by cement extrusion from the exposed proximal femoral cortex and a complete lack of back-bleeding.

     

    P ITFALLS

    • An improper starting point will result in a stem positioned in varus or a deficient cement mantle in Gruen zones 8/9.

     

    Step 8: Femoral Stem Insertion

  • Selection of a femoral stem implant should be based on surgeon’s preference, a review of the literature, and stem availability.

  • To prevent stem malalignment and cement mantle defects, the same posterolateral starting point used for opening the femoral canal is used for stem insertion.

  • The stem is slowly inserted using a stem inserter. The inserter should not be rigidly attached to the stem, but should allow for controlling stem version.

     

     

     

    157

     

    Cemented Femoral Stem

     

    FIGURE 13 A B

    • Cement should generally be of medium viscosity during stem insertion. Larger stems should be inserted early as they displace a larger volume of bone cement.

    • Figure 13 shows the final appearance of the femoral stem in AP (Fig. 13A) and lateral (Fig. 13B) radiographs.

      Postoperative Care and Expected Outcomes

    • Patients are typically allowed to get out of bed and weight bear as tolerated on the day after surgery. For the first 4 weeks after surgery, patients use a walker or crutches and then graduate to a cane until their balance and strength have recovered.

    • Pain control begins in the operating room, with infiltration of soft tissues with local anesthetic prior to closure. Patients are routinely given patient-controlled analgesia pumps overnight after surgery and started on oral narcotic agents on postoperative day 1 if they are tolerating an oral diet.

       

      158

       

      Cemented Femoral Stem

       

  • Every patient receives some form of deep venous thrombosis prophylaxis. Low-molecular-weight heparin products are most commonly used and are begun approximately 8 hours after surgery and then dosed daily for 2 weeks. Patients wear T.E.D. hose and pneumoboots while in bed and in the hospital.

  • Physiotherapy is begun on the day after surgery and focuses on early mobilization and precautions specific to the surgical approach.

Evidence

Barrack RL, Mulroy RD, Harris WH. Improved cementing techniques and femoral component loosening in young patients with hip arthroplasty: a 12 year radiographic review. J Bone Joint Surg [Br]. 1992;74:385–9.

 

The authors reviewed their series of cemented femoral stems in patients younger than 50 years of age using second-generation cementing techniques, including a distal cement plug, retrograde cement delivery, and an irrigated femoral canal. Results at 12 years demonstrated that no stem had been revised for aseptic loosening, and only one stem was loose radiographically.

 

Majkowski RS, Miles AW, Bannister GC, Perkins T, Taylor GJS. Bone surface preparation in cemented joint replacement. J Bone Joint Surg [Br]. 1993;75:459–63.

 

In this study using bovine cadaver femora, the effect of nine different techniques for preparing the femur were compared with regard to cement penetration and shear strength at the cement-bone interface. The use of pressurized lavage either in a continuous or pulsed mode resulted in the greatest final cement penetration and shear strength.

 

McKaskie AW, Barnes MR, Lin E, Harper WM, Gregg PJ. Cement pressurization during hip replacement. J Bone Joint Surg [Br]. 1997;79:379–84.

 

Cement pressurization using finger-packing or a cement gun was compared in both clinical and laboratory models in this study. Cement delivery using a gun consistently produced greater maximum cement pressurization in both models. Insertion of the femoral stem produced greater pressurization than either delivery method.

 

Rasquinha VJ, Ranawat CS, Dua V, Ranawat AS, Rodriguez JA. A prospective, randomized, double-blind study of smooth versus rough stems using cement fixation. J Arthroplasty. 2004;19(7):2–9.

 

This randomized, clinical trial compared one surgeon’s intermediate-term results using either rough (Ra-170) or smooth (Ra-17) stems. At a minimum of 5 years, there were no reported differences in clinical or radiographic outcomes.

 

Settecerri JJ, Kelley SS, Rand JA, Fitzgerald RH. Collar versus collarless cemented HD-I femoral prostheses. Clin Orthop Relat Res. 2002;(398):146–52.

 

In this study, 84 patients were randomized to receive either a collared or collarless femoral stem. Among the 43 patients available for follow-up at an average of 9.6 years after surgery, there were no significant differences between the groups with respect to pain, Harris Hip Score, or implant survival.