P ITFALLS

• Presence of active infection is a contraindication to prosthesis implantation.

• Underlying femoral deformity.

• Metaphyseal-diaphyseal mismatch (dysplasia).

Cementless Femoral Stems

Indications

• Symptomatic arthritis in patients who have failed conservative measures.

• Patients should have suitable proximal femoral morphology for implantation of an uncemented stem, champagne flute shaped and funnel shaped.

  Examination/Imaging

  Controversies

  • The best stem shape, tapered or cylindrical distal fit, remains a topic of debate. Both techniques are described.

   

• A standard hip examination, including assessment of preoperative limb length discrepancy, should be done. Assessing the patient’s perception of any limb length discrepancy is essential.

• Plain radiographs:

  • Anteroposterior (AP) radiograph of the pelvis, AP and lateral radiographs of the hip (Fig. 1A and 1B).

    Treatment Options

    • Nonoperative measures utilizing a combination of analgesics, nonsteroidal anti-inflammatory drugs, walking aids, and activity modification to control the patient’s symptomatology are effective in early stages of the disease.

    • Other techniques for implanting modular uncemented stems or cemented prostheses, or for resurfacing arthroplasty, are available in addition to the cementless stem described here.

     

  • Proximal femoral morphology can be evaluated to assess suitability for implantation of uncemented stem (Fig. 2). As seen in Figure 2, Dorr type A and type B femoral canals are suitable for uncemented fixation, whereas type C may be more challenging. Appropriate templating should be performed for the implant chosen. This has been described in Procedure 4.

    Surgical Anatomy

• The greater trochanter lies slightly posterior and lateral to the axis of the femur. The gluteus medius tendon attaches to the lateral border and minimus tendon anteriorly.

• The piriformis tendon attaches to a fossa on the medial aspect of the greater trochanter—this is the landmark for accessing the femoral canal.

• The sciatic nerve leaves the pelvis through the greater sciatic foramen, below the piriformis, and traverses the thigh in the posterior aspect. Care must be taken when placing retractors behind the trochanter, to elevate the proximal femur in the wound, that the nerve is protected.

   

   

   

   

  Cementless Femoral Stems

   

  A

   

   

   

  177

   

  FIGURE 1 B

   

   

  FIGURE 2 A B C

   

  178

   

   

  P EARLS

  • Ensuring that the contralateral knee and foot can be palpated through the drapes and are not obscured by padding helps determine limb lengths intraoperatively.

     

    P ITFALLS

  • Care should be taken to ensure that the pelvis is securely fixed because otherwise the patient can tilt intraoperatively, leading to loss of the fixed position of bony landmarks, which can affect acetabular component positioning.

   

  Cementless Femoral Stems

   

  Positioning

• Lateral positioning of the patient is used, with the affected side uppermost and the pelvis fixed with anterior and posterior bolsters.

• The limb is draped free, and a “dislocation bag” is attached to the drapes to keep the foot sterile.

• The femur should be rotated internally (posterior approach) or externally (lateral approach) so that the tibia is perpendicular to the floor and the proximal femur is delivered into the wound (Fig. 3).

  Portals/Exposures

  Controversies

  • Patients can be placed supine on the table for the procedure.

   

  Equipment

  • Anterior and posterior positioning bolsters

   

• Exposures for total hip arthroplasty have been described in Procedures 5 and 6.

FIGURE 3

179

P EARLS

• An osteotomy guide can be positioned on the proximal femur to determine the level of the femoral neck resection.

   

  P ITFALLS

• Care should be taken of the surrounding soft tissues, and two Hohmann retractors should be placed around the femoral neck prior to neck sectioning.

Cementless Femoral Stems

Procedure

Step 1

• During the exposure and prior to dislocation of the hip, the limb length and offset are assessed using a leg length/offset guide. The hip is positioned so that the knees and feet of both limbs are aligned.

• A transverse mark is made with diathermy and a marking pen on the highest point of the greater trochanter.

• A short pin with a guide stop is then inserted into the iliac wing through a small stab incision.

  Instrumentation/ Implantation

  • A limb length and offset guide and appropriate pin may be used for accurate measurement.

  • A power saw is used to make the femoral neck osteotomy.

   

• The limb length and offset guide is then set for the patient’s preoperative leg length and hip offset (Fig. 4). The guide is then placed on the back table and not adjusted; it will be required for assessing the limb length and offset after reconstruction of the joint.

• The femoral neck should be osteotomized at the appropriate level as determined by preoperative templating for the prosthesis to be implanted (normally a finger breadth above the level of the lesser trochanter).

FIGURE 4

Controversies

• Leg length can also be assessed by placing both feet together and assessing the relative position of the knees, although this is less accurate than using a guide. The relative abduction/ adduction positions of the legs must be taken into account if using this method.

• Various designs of stems are available, such as tapered, cylindrical, and anatomic. Step 1 is the same for all. Tapered and cylindrical stem femoral preparation and implantation are discussed separately below.

  • The tapered stem type is designed with a proximal-to-distal taper to wedge into the metaphyseal region of the femur. The proximal part of the stem has a porous coat to enhance initial stability and allow for bone ingrowth. The geometric design of this stem means it can subside into a position of maximal fit, which improves load sharing of the device with proximal bone.

  • The cylindrical stem gains initial stability with tight diaphyseal fit. The canal is machined to accommodate the stem, which maximizes its potential for bone ingrowth by being fully porous coated.

180

P EARLS

• Clearing the soft tissue from the piriformis fossa aids in establishing the correct entry point for the box osteotome, ensuring that this is lateralized appropriately.

   

• Placing blunt retractors around the femoral shaft at the level of the calcar can help to “gunsight” a straight passage down the canal.

   

  P ITFALLS

• Care must be taken to stay lateral with the box osteotome to ensure that subsequent reaming and broaching are in alignment with the femoral axis.

Cementless Femoral Stems

Procedure: Tapered Stem Technique

Step 2

• The piriformis fossa is identified and the femoral canal is opened with a box osteotome (Fig. 5). The femoral canal is opened.

• A canal finder can then be inserted down the canal to identify a straight passage down the femur (Fig. 6).

   

  Instrumentation/ Implantation

  • A box osteotome is required to open the femoral canal.

   

   

  FIGURE 5

   

   

   

  P EARLS

  • Ensure that the reamer remains lateral and in alignment with the femoral canal to ensure placement in the center of the medullary canal.

     

  • Creating a groove in the medial aspect of the greater trochanter will allow axial canal reaming.

     

    P ITFALLS

  • Varus placement of the reamer will result in undersizing of the implant.

     

  • Care must be taken while using the reamer to avoid damage to the abductor muscles.

   

   

   

  Tapered reamer

   

  Greater trochanter

   

   

  Cementless Femoral Stems

   

  Lesser trochanter

   

  Cortical bone of femoral diaphysis

  Reamer seated in varus contacting lateral femoral cortex as entry point to medial in neck

   

  181

   

  FIGURE 6

   

  Step 3

  Instrumentation/ Implantation

  • Sequentially sized femoral canal reamers

   

  • The smallest tapered reamer is used to begin reaming the femoral canal. Insert the reamer starting slightly posterolaterally to ensure access to the center of the medullary canal.

  • Sequential reamers are then used to enlarge the canal until firm cortical reaming is felt. The depth of adequate insertion, in relation to the greater trochanter, is usually marked on the reamer (Fig. 7).

     

     

     

    FIGURE 7

     

    182

     

    Cementless Femoral Stems

     

    The decision regarding the final component size is based on the fit of the broach, not the reamer.

    Reaming should be stopped once resistance is felt to avoid using a reamer size that will be oversized relative to the final broach size.

• If intraoperative sizing is found to be much less than templated sizing, there is a high probability that the femoral preparation is in varus.

   

  P EARLS

  • Occasionally backing the broach out of the canal a short distance before further advancement, which cleans the broach teeth of bone, allows easier advancement.

     

    P ITFALLS

  • Care is required to maintain the broach laterally in alignment with the femoral canal to prevent varus positioning.

     

  • The abductor musculature should be protected to prevent damage from the broach.

     

  • Care must be taken on removing the broach to ensure that the greater trochanter is not fractured. Placing a slight varus force on the broach handle when it is being removed will help minimize the risk of fracture.

   

  Step 4

• The femoral canal is then broached to remove cancellous bone, maintaining the axis in alignment with the axis of the femur. The broach should be inserted maintaining the required anteversion of the femoral neck. An anteversion guide can be attached to the broach handle to ensure that appropriate anteversion is achieved (Fig. 8).

• Start with a broach three sizes smaller than the largest reamer used. Insert the broach until the top reaches the level of the neck resection. Sequential broaches should be inserted until the templated size is reached. This should be seated so that the top of the broach is level with the neck resection. The selected final broach should be rotationally stable within the femoral canal, and this should be assessed by attempting to rotate the broach within the femur.

   

   

  Instrumentation/ Implantation

  • Sequentially sized femoral canal broaches, a broach handle, anteversion handle, and mallet

  • Calcar planar reamer

   

   

  FIGURE 8

   

  183

   

  Cementless Femoral Stems

   

• Stability can be checked by attempting to retrovert the stem using the broach handle. Stability is indicated if there is no movement at the bone-broach interface.

• If the size of broach selected does not achieve stability in the bone, it should be removed, the next-sized reamer inserted to the appropriate depth, and then the canal broached again using the corresponding-sized broach. Stability should then be rechecked. For example, if a size 3 broach did not achieve rotational stability, remove the broach, ream with a size 4 reamer, and insert a size 4 broach before rechecking stability.

• The broach handle is removed, leaving the broach in the femoral canal, and the calcar is reamed using the planar reamer, which fits over the broach trunion.

   

  P EARLS

  • If the femoral head is equatorial in the acetabulum with the limb in 20° of flexion and 30° of internal rotation, then component position is correct.

     

  • If trial placement demonstrates leg length to be perfect with the shortest available head, be wary, as the femoral component final position will normally be 2–

  3 mm proud from the final broach position. If trial placement demonstrates this finding, rebroach to seat the broach (and therefore the femoral implant) a few millimeters further.

   

  Step 5

• A trial neck, standard or high offset as determined by templating, is placed on the broach. A trial femoral

  head of the chosen diameter and length is applied and the hip is reduced.

• Hip stability is then checked with the hip in full extension and external rotation, and in full flexion and internal rotation. The feet are then opposed and the limb length and offset checked with the guide that was set previously. Instability is an indication of

  the joint being too loose, bony impingement, or component malposition.

• The hip can be retrialed using different options of neck offset and neck length until the desired stability, offset, and limb length are achieved.

Instrumentation/ Implantation

• Offset options for different broach sizes and selection of femoral heads of required head diameter with different neck lengths

184

P EARLS

• If the stem cannot be inserted by hand to the desired level (to within one finger breadth of porous coat) before using the mallet, remove the stem and rebroach using the last size of broach. This will ensure safe stem implantation without femoral fracture.

   

• During stem insertion, an occasional break from hammering allows the femoral bone (and surgeon) to relax.

   

• It is a common and normal finding that the fixed stem position will be 2–3 mm proud of the final broach position.

   

  P ITFALLS

• Tapered stem insertion, if too vigorous, can split the femoral canal. If the stem is not advancing and has not been seated, it should be removed and the canal rebroached.

Cementless Femoral Stems

Step 6

• The selected femoral stem is now implanted after removing the broach. The stem is attached to the stem inserter and entered into the femoral canal. Hand insertion should enable the stem to be inserted to within one finger breadth of the proximal extent of the porous coating (Fig. 9). The stem can then be seated fully by gentle mallet blows.

• The selected trial head is then placed on the Morse taper and the hip reduced to reassess stability and limb length. The Morse taper is washed and dried and the definitive selected head is implanted.

• The hip joint is thoroughly washed, taking care to ensure there is no debris in the acetabulum, and the hip is reduced.

• The capsule should be sutured. The hip approach is then closed in layers.

   

  Instrumentation/ Implantation

  • Femoral stem introducer and mallet

   

   

  FIGURE 9

   

   

  P EARLS

  • Care must be taken to make the pilot hole lateral and posterior to ensure that reaming and broaching are in alignment with the femoral axis.

     

  • The final one to two reamers should have evidence of cortical bone within their cutting flutes. If not, beware of being undersized.

   

  Procedure: Cylindrical Stem Technique

  Step 2

  • A pilot hole is placed in the piriformis fossa.

  • The canal is then reamed with sequential reamers until a good bite of the endosteal cortical bone is

    felt. The aim is to ream the diaphyseal canal to obtain 5 cm of cortical fit with a reamer that is 0.5 mm smaller than the proposed stem size (Fig. 10).

     

     

     

    Cementless Femoral Stems

     

    Reamer

     

    Instrumentation/ Implantation

    • Pilot hole drill

    • Sequentially sized intramedullary reamers

     

    Greater trochanter

     

     

    185

     

     

    P ITFALLS

    • Failure to seat the broach to the appropriate level may be due to inadequate canal reaming or reaming the canal in varus.

     

    Lesser trochanter

     

    Instrumentation/ Implantation

    • Femoral broaches and a mallet

    • Trial necks for broach and assorted heads

     

    Reamer has appropriate isthmic cortical fit

     

     

    Femoral canal

     

    FIGURE 10

     

    Step 3

  • Begin with the smallest broach and increase until broach size matches the component size (based on the size of the distal reaming).

     

    P EARLS

    • If the stem cannot be introduced by hand to 5 cm of final position, the appropriate-size line-to-line reamer and broach should be inserted again.

       

    • Stem introduction can take many mallet blows.

     

  • The appropriate-size broach is selected and impacted into the femoral canal, maintaining the correct anteversion, to the level of the neck cut. The rotational plane for the broach is that of the femoral neck cut.

  • A trial neck and head are then applied to the broach

    trunion and a trial reduction of the hip is performed. Limb length and offset and hip stability are tested as for the tapered stem. Appropriate adjustments are made to ensure that the hip is stable and there is adequate restoration of limb length and offset.

     

    186

     

    Cementless Femoral Stems

     

    Step 4

• The chosen definitive stem is then implanted following broach removal. It should be possible to insert the stem by hand pressure to a depth requiring 5 cm advancement (to achieve diaphyseal fixation over 4–6 cm) by mallet blows on the introducer.

  Controversies

  • Restricting weight bearing during the first 6 weeks of rehabilitation is controversial.

   

  Postoperative Care and Expected Outcomes

• An abduction pillow is placed between the patient’s legs to prevent adduction and potential dislocation. This may be maintained while the patient is in bed for the first 6 weeks.

• Mobilization is commenced on day 1. Weight bearing may be limited to 50% for the first 6 weeks as bone ingrowth commences.

• The patient is discouraged from flexing the hip beyond 90° or hip adduction (crossing the legs) for the first 6 weeks as the soft tissues heal.

• Abductor strengthening exercises are commenced after 6 weeks.

• Following radiographs taken at 6 weeks to ensure implant stability, the patient increases to full weight bearing and is weaned off walking aids.

• Patients should anticipate return to normal activities unaided by 12 weeks.

Evidence

Bourne RB, Rorabeck CH, Patterson JJ, Guerin J. Tapered titanium cementless total hip replacements. Clin Orthop Relat Res. 2001;(393):112–20.

This study is a retrospective review of 307 total hip replacements with a tapered titanium cementless stem. It reports good survivorship of the femoral stem at minimum 10 years’ follow-up. [Case series]

Chen CJ, Xenos JS, McAuley JP, Young A, Engh CA Sr. Second-generation porous coated total hip arthroplasties have high survival. Clin Orthop Relat Res.

2006;(466):66.

This retrospective review of 157 consecutive hip replacements with a fully porous-coated cylindrical femoral component reports 99% survivorship at 5 years with bone ingrowth evident in 99% of stems. [Case series]

Dorr LD, Faugere MC, Mackel AM, Gruen TA, Bognar B, Malluche HH. Structural and cellular assesssment of bone quality of proximal femur. Bone. 1993;14:231–42.

This clinical study describes radiographic measurement of proximal femoral morphology and correlates it to bone histomophometry. It describes radiographic features that are favorable for uncemented stem implantation. [Grade 1 recommendation]

187

Cementless Femoral Stems

Engh Jr CA, Claus AM, Hopper RH, Engh CA. Long term results using anatomic medullary locking hip prosthesis. Clin Orthop Relat Res. 2001;(393):137–46.

This study reviews 223 consecutive hips using a cylindrical femoral component with a mean 13.9-year follow-up. [Case series]

Mallory TH, Lombardi AV, Leith JR, Fujita H, Hartman JF, Capps SG, Kefawa CA, Adams JB, Vorys GC. Minimal 10-year results of a tapered cementless femoral component in total hip arthroplasty. J Arthroplasty. 2001;16(Suppl 1):49–54.

This paper reports a series of 120 hips with a dual-tapered femoral component. Results show a survivorship of 97.5% at a mean follow-up of 12.2 years. [Case series]