The Polished Tapered Cemented Stem

 

 

 

INTRODUCTION

 

Since the advent, in the 1960s, of total hip replacement with cemented fixation, some designs have proven successful in the long term whereas others have not (1,2). There are two key principles to achieving long-term fixation with a cemented hip replacement, and both of these will be addressed in this chapter. Firstly, a surgeon should use a cemented stem that is designed to accommodate the properties of surgical cement, and secondly, the hip replacement should be performed with attention to detail, using a contemporary cementing technique.

Although in common parlance, use of the term “cement” to describe polymethylmethacrylate (PMMA) polymer is perhaps unfortunate because it evokes comparison with the inert grout used by the construction industry. In truth, PMMA polymer is a dynamic, viscoelastic material that exhibits important long-term properties (3) and these must be accounted for in the design of a cemented stem if long-term fixation is to be achieved. Most importantly, cement will slowly change shape over time if subjected to a sustained force, in a process known as creep, and the geometry of some stems is designed to allow for creep while others are not. Broadly speaking, cemented stems fall into two main categories, these being composite beam (sometimes referred to as shape-closed) stems and taper-slip (also known as force-closed) designs (4,5).

Taper-slip (force-closed) stems have a highly polished surface and are not bound to the PMMA polymer. They share common features in addition to their surface finish, being devoid of a collar and tapered in shape. As load is applied to these stems, they engage with the cement as a taper, and fixation is achieved by a balance of forces (6,7,8), just as it is in other scenarios where the common engineering concept of the taper is employed. The unique feature of this form of fixation is subsidence of these stems into the cement mantle over small distances. Studies using radiostereometric analysis (RSA) have shown that taper-slip stems migrate in the first year and then settle over time, with reported movement being 0.7 mm at 2 years and 1.3 mm at 10 years (8).

Such subsidence is desirable and necessary for these types of stems to engage as a taper for long-term fixation. Many designs incorporate use of a hollow distal centralizer that provides a space below the stem tip into which the stem may subside to a stable position, without creating excess stress at the distal cement mantle (9).

Subsidence of taper-slip designs seems to have an additional benefit, in that it makes them more resistant to torsional forces and therefore more rotationally stable. Studies comparing taper-slip and composite beam stems

(10) have shown that the latter also migrate distally, albeit over smaller distances than do taper-slip stems.

 

Taper-slip cemented stem designs differ from so-called composite beam implants. In the composite beam concept, the stem surface is rough or contoured to allow interdigitation of the PMMA

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polymer and the stem surface, with the expectation that the stem will be rigidly bound to the cement. In this

concept, stems may be described as “bonded” and such fixation will be intolerant of any micromotion at the stem-

cement interface. Indeed, such micromotion has been shown to initiate a damaging cycle of events in which wear occurs between the stem and cement that eventually leads to loss of stem fixation (debonding) and aseptic loosening (11,12).

An example of the taper-slip design is the Exeter hip, designed in 1969 and first implanted in 1970 (13,14). Evidence from multiple centers and joint registries shows that this stem—and others like it—have given good

results, in terms of aseptic loosening and revision rates (see literature review). Moreover, the technique offers two distinct significant advantages over most cementless designs, namely, the ease of anatomic restoration at the primary procedure and modularity at any subsequent operations.

Anatomic restoration is facilitated by the combination of features inherent in such stem designs, being as they are cemented, collarless, and available in a range of different sizes and offset. This means that a surgeon may select the appropriate offset to match the needs of the patient and then the stem size to match the dimensions of the femoral canal and finally may insert the stem into the cement to a depth that is entirely under the surgeon's control and that will restore the correct leg length. Patients with high offset and narrow canals (typically young males) are accommodated as easily as are patients with capacious canals and low offset (typically older females).

Modularity at revision procedures is a valuable advantage to the surgeon conferred by these stems and is a consequence of their polished, tapered geometry and the associated taper-slip fixation. Exposure of the hip during a revision is facilitated by stem removal achieved by clearing the cement over the stem shoulder after which the stem can be tapped out of the cement mantle to allow access to the acetabular component. At the end of the revision operation, the same size or a smaller stem can be recemented into the old cement mantle without compromising the cement-bone interface and without the need to remove the well-fixed cement mantle.

As already discussed, the best long-term results will be produced by the combination of a proven stem design with a modern cementing technique. The aim of the surgical technique is to create close contact between cement and living bone (osseointegration (15)), without an intervening cellular layer, and this can only be achieved through meticulous surgical technique. Initial fixation is ensured by adequate bone preparation prior to the application of cement—it is important to leave strong trabecular bone in the proximal femur and to clean it well with the use of a pressurized lavage system. After retrograde filling of the plugged canal with PMMA polymer, pressurization of the PMMA is maintained prior to, during, and after insertion of stem until the polymer has completely cured. The techniques to achieve this are described below.

 

INDICATIONS FOR THE USE OF A CEMENTED STEM AT PRIMARY ARTHROPLASTY

Cemented femoral stems may be considered for any patient who requires a hip arthroplasty, but in choosing a stem for use, the surgeon should be aware that force-closed or taper-slip designs have generally given better results than shape-closed implants (4). There is no limitation to the age or diagnoses that may be suitable for cemented stem fixation, and in complex cases where there is distortion of the anatomy, femoral shortening procedures and derotation osteotomies can be carried out. After fixation of the osteotomy, the endosteal aspect of the osteotomy site should be impaction-grafted with autogenous bone chips to protect the osteotomy from cement intrusion during cement pressurization. For cases of displaced fractures of the femoral neck, cemented hemiarthroplasties or cemented femoral components in total hip replacements are indicated. There is a further advantage to using cement for fixation in cases of previous septic arthritis of the hip, since the cement can be loaded with appropriate antibiotic to reduce the risk of recrudescence of infection.

 

CONTRAINDICATIONS

There are no specific contraindications to the use of cement fixation in any patient for whom a hip arthroplasty is indicated.

 

 

 

 

PREOPERATIVE PREPARATION/PLANNING

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Preoperative planning is an essential part of the operation and helps the surgeon predict the size, offset, and depth of insertion of the femoral prosthesis. Templating can be performed on traditional films or on digitized PACS (picture archiving and communication software) films using appropriate software, but it is important to ensure that the magnification of the radiograph is known and corrected for. The true offset is shown when the radiograph is taken with the lower limb internally rotated by approximately 15 degrees.

For templating of conventional radiographs:

 

 

Place the concentric rings on the templates centrally within the femoral head to locate and mark the femoral center of rotation.

 

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 (Fig. 14-1).

 

If the patient's offset is between the prosthetic offset ranges available, the series of stems with the closest offset is chosen, and plus or minus heads can be then used to fine-tune the offset.

 

The stem size is identified by sequentially using templates with the femoral head and prosthetic head aligned. The stem size that will produce a 2 to 3 mm of cement mantle is chosen.

 

Leg length is controlled by the depth of insertion of the implant, and it is therefore independent of the choice of stem size and offset. The template is placed overlying the radiograph with the prosthetic head over the femoral center of rotation, and the stem centered in the canal. The outline of the neck, shoulder, and the stem is marked on the radiograph. The distance between tip of trochanter and shoulder of prosthesis is marked and noted. This insertion level will reproduce the patient's anatomy and will achieve the correct leg length (16) (Fig. 14-2).

 

 

 

FIGURE 14-1 Radiograph with stem template overlying. Note adequate offset and cement mantle.

 

 

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FIGURE 14-2 Distance from the shoulder of the prosthesis to the tip of the greater trochanter is marked.

 

OPERATIVE TECHNIQUE

The longevity of the hip replacement depends on the surgeon establishing adequate initial mechanical interlock between the implant and the bone. 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 the time of initial injection until polymerization is complete, good cement intrusion into bone is assured and blood is prevented from accumulating at the interface (17,18,19).

 

Surgical Steps

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

 

Femoral Neck Cut

Because the stem is collarless and the stem depth of insertion is flexible, the level of the neck cut is not critical with this type of stem. However, the resection line usually runs from a point midway between the upper margin of the lesser trochanter and the inferior aspect of the head to the upper surface of the base of the neck where it meets the greater trochanter (Fig. 14-3).

 

 

 

FIGURE 14-3 The neck cut is performed. A cobra retractor is placed to protect the soft tissues.

 

 

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Femoral Exposure

The leg is internally rotated and the hip flexed to visualize the proximal femur. In routine cases, neither the anterior capsule nor the iliopsoas tendon requires release. Additionally, the piriformis muscle can often be preserved. A femoral elevator is placed on the anteromedial aspect of the neck to deliver the femur into the

wound (Fig. 14-4). A gluteal retractor is then passed around the greater trochanter to retract the gluteus medius and minimus (Fig. 14-5). Exposure should be sufficient to allow access down the midline of the femoral canal.

 

 

 

FIGURE 14-4 The femoral elevator is placed around the anterior neck to elevate the femur out of the wound.

 

 

 

FIGURE 14-5 The gluteal retractor is placed to expose the piriformis fossa.

 

 

 

Canal Preparation

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The critical step is to ensure that the correct entry point in the proximal end of the medullary canal is utilized. For a straight stem, this is made posterolaterally into the piriformis fossa to allow the insertion of taper-pin reamers and rasps in the midline axis of the medullary canal. A slot in the trabecular bone of the proximal femur is made using a box chisel or specific gouges and osteotomes (Fig. 14-6). A lateral cortical ridge usually remains, which could prevent stem insertion at the correct entry point (Fig. 14-7), and this is removed using a combination of gouges and rongeurs or a high-speed burr (Fig. 14-8). The medullary canal and “true calcar” are then expanded using taper-pin reamers (Fig. 14-9). The canal is washed and aspirated, and the plug sounds are used to check the size of the canal at a level immediately distal the stem tip (Fig. 14-10). A distal PMMA plug of the measured diameter can be opened ready for implantation. Throughout preparation of the canal, care is taken to irrigate after every instrument passage to reduce the intramedullary fat load, which could otherwise embolize to the pulmonary bed. We believe this is why in a review of 9,082 consecutive patients over a 10-year period only one intraoperative death was found to have occurred, dispelling the widely accepted “myth” that cement embolization and cardiovascular collapse are common phenomena (20).

 

 

 

FIGURE 14-6 The box cut has been performed in the femoral neck.

 

 

 

FIGURE 14-7 A lateral ridge is present after the box cut has been performed.

 

 

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FIGURE 14-8 The lateral ridge is taken down with a burr or side-biting nibblers.

 

 

 

FIGURE 14-9 Taper-pin reamers are used to open the canal.

 

 

 

FIGURE 14-10 The canal is sized to ensure a canal plug fits snuggly preventing cement egress distally and loss of proximal pressurization.

 

 

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The appropriate offset rasps, determined from preoperative templating, are then used sequentially to prepare the canal for the stem and its PMMA mantle. The first rasp used is usually one smaller than the anticipated size from templating and acts as a broach to further develop the slot on the posterolateral aspect of the trochanter.

Subsequent rasps are then used to expand the canal, stopping at the smallest rasp size that achieves rotational and axial stability within the canal. The aim is to create a cavity lined with strong cancellous bone that will form the bed into which PMMA is pressurized. The strongest cancellous bone is within 3 to 4 mm of the endosteal surface of the femur (21). Oversized reamers should not be used as they will remove this bone. The height of the greater trochanter above the shoulder of the rasp is noted to compare with the radiographs and the final rasp is seated at the predetermined depth decided from the templates (Figs. 14-11 and 14-12).

 

 

 

FIGURE 14-11 The broach handle is marked with a surgical marker at a distance corresponding to Figure 14-2.

 

 

 

FIGURE 14-12 The broach is impacted until the line drawn is adjacent to the tip of the greater trochanter.

 

 

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A trial femoral head is placed over the spigot and the hip is reduced (Fig. 14-13). Correct restoration of leg length is assessed by comparing predetermined landmarks such as the relative positions of the femoral condyles or by use of a proprietary leg length measuring device. If the leg is found to have been shortened, the stem can be left proud to compensate. Leg lengthening is corrected by impacting the rasp further into the femur and repeating the trial reduction. A smaller rasp with the same offset may be required, and sometimes, the neck may need to be cut shorter to allow deeper seating of the rasp. The range of motion and stability of the hip is checked in all positions. Soft tissue tension is also assessed. If bone-on-bone impingement of tissues is found to compromise stability, it may be caused by inadequate restoration of the patient's offset and this must be addressed. When the correct leg length has been achieved, the hip is dislocated and the trial head removed. The femoral neck is marked to note the alignment and the depth of the rasp (Fig. 14-14). To save time, cement mixing may be started at this stage while the final preparation of the femur is carried out.

Bone cement containing antibiotics is routinely used at our institution, mixed at approximately 1 Hz in a low

vacuum, to prevent the fumes of the monomer getting into the operating room. We do not employ full-vacuum mixing or any other measures to reduce porosity in the cement, since this has not been found to confer any advantage in the medium term (22,23), especially if a force-closed design of stem is used. It is customary to use two 40-g mixes of cement in the cement gun; in larger canals, three mixes may be needed for adequate pressurization of the cement.

 

 

 

FIGURE 14-13 The trial reduction is performed utilizing the trial heads.

 

 

 

FIGURE 14-14 The neck is marked to ensure the stem is sunk to a depth corresponding to the broach.

 

 

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The appropriate intramedullary plug is then introduced (Fig. 14-15) and this should be a tight fit in the canal, approximately 1 cm beyond the point at which the tip of the stem will eventually be sited. The plug introducer bears the same three marks on its anterior and posterior surfaces as those found on the rasps and stems, which help to ensure accurate positioning of the plug (Fig. 14-16). The medullary canal is washed with a power lavage system, which serves to clean the interstices of the strong trabecular bone of marrow and fat and thereby allow cement intrusion (Fig. 14-17). A fine-bore suction catheter is inserted into the canal. The canal is then packed firmly with ribbon gauze soaked in hydrogen peroxide (Fig. 14-18) to assist in achieving hemostasis and further clean the trabecular bone (18) (Fig. 14-19). Alternatively, adrenaline-soaked gauze or ice-cold gauze rolls may be used. The resulting trabecular surface should be clean and free of blood (Fig. 14-20).

 

 

 

FIGURE 14-15 The cement plug is placed.

 

 

 

FIGURE 14-16 The plug introducer has a series of marks corresponding to the preceding broach.

 

 

 

FIGURE 14-17 The canal is thoroughly lavaged with pulsatile saline.

 

 

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FIGURE 14-18 Peroxide-soaked gauze is packed down the femur with a taper-pin reamer once the femur has been vented with a retrograde suction catheter.

 

 

 

FIGURE 14-19 The peroxide gauze is fully packed while the suction catheter aids canal drying.

 

 

 

FIGURE 14-20 Once removed, the clean trabecular bone, devoid of blood or debris, can be observed just prior to cementing.

 

 

 

Cement Insertion and Pressurization

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The PMMA mixture is poured into the cement-gun barrel between 1.5 and 2 minutes after the polymer powder and liquid monomer are combined (Simplex cement with an operating room temperature of 21°C, although some surgeon may warm their cement to 24°C to speed polymerization). The ribbon gauze is removed from the canal and retrograde cement injection is carried out (Fig. 14-21). The suction catheter is withdrawn as soon as it is blocked by cement. Once the canal is filled, the nozzle of the gun is cut level with the distal femoral seal (Fig. 14-22), which is pushed firmly into the open end of the canal. Cement injection through the seal is initially pulsatile through repeated, sharp squeezes on the trigger. This process should be accompanied by the steady extrusion of fat and marrow through the proximal femoral cortex (Fig. 14-23). Pressure is then maintained through the slow continued injection of cement until its viscosity is judged appropriate for stem insertion. This is not usually less than 5 minutes after the start of mixing, depending on the operating room and cement temperature, and is best judged by the feel of a bolus of cement retained in the surgeon's hand.

 

 

 

FIGURE 14-21 The canal is filled with a cement gun in a retrograde fashion (note the suction catheter that is maintained until it becomes blocked, at which point it is removed).

 

 

 

FIGURE 14-22 The cement is pressurized with a gun; the proximal femur is sealed using a “half-moon” seal.

 

 

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FIGURE 14-23 Marrow extrusion is noted is pressurization is adequate. This indicates a clean cement-bone interface.

 

Stem Insertion

The stem may be immersed in a saline bath at 60°C for a few minutes prior to insertion, to heat the metal, which helps to accelerate PMMA polymerization and to reduce porosity at the stem-cement interface (24,25), but this is not an essential step. If done, the stem is thoroughly dried prior to its insertion into the femoral canal.

Once the surgeon is satisfied that the viscosity of the cement has reached an appropriate state, the stem is inserted down the midline axis of the canal. The point of entry into the cement should be near the posterior margin at the cut surface of the femoral neck. Because of the normal anteversion of the femoral neck and the

bow of the femur in the sagittal plane, this posterior entry point reduces the chance of mantle deficiencies in the lower part of zone 8 and the upper part of zone 9 (anteriorly). Anteroposterior centralization of the stem at the level of the cut surface of the neck is likely to lead to an incomplete mantle of cement unless the level of neck section is extremely low. Particular care should be taken with the entry point if a direct lateral approach to the hip is used.

Throughout the period of stem insertion, the opening of the canal medial to the stem is occluded by the surgeon's thumb so as to maximize the cement-bone interface pressure, especially in the proximal femur. Halfway through this process, the rotation and alignment of the stem are checked. If required, these can be corrected at this stage before stem insertion is completed (Fig. 14-24).

 

 

 

FIGURE 14-24 The stem version is checked as it is implanted.

 

 

 

After Stem Insertion

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When the stem has reached its final position, the stem must not be moved within the mantle while the cement is polymerizing. The introducer is removed, the “horse collar” proximal seal is applied to the cut surface of the femoral neck around the stem, and firm pressure is maintained on the cement column until the latter has cured (Fig. 14-25). This seal slows the fall of pressure within the canal and prevents blood accumulating at the cement-bone interface until polymerization is complete. Once the cement has polymerized, a further trial reduction is performed (Fig. 14-26) and then the definitive head is inserted. The hip is reduced, the capsule and rotators are reattached through drill holes in the greater trochanter (Fig. 14-27), and further wound lavage is performed.

 

 

 

FIGURE 14-25 The horse collar is applied maintaining proximal pressurization until the cement has set.

 

 

 

FIGURE 14-26 A final trial reduction is performed; leg length, tissue tension, and stability are checked.

 

 

 

FIGURE 14-27 After copious chlorhexidine lavage, the short external rotators and capsule are reattached to the trochanter via drill holes (Savory technique).

 

 

 

PEARLS AND PITFALLS

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Sufficient time should be spent on templating (see Chapter 11). This will give an indication of not only the stem size and offset but also the depth of insertion of the prosthesis.

 

Make a note of neck angle on the preoperative radiographs. A patient with coxa vara may be at an increased risk of limb lengthening and this should be explained to the patient preoperatively. In such cases, the neck cut should be lower than usual and the stem needs to be inserted further distally than normal. In cases with coxa valga, the opposite is true. The neck cut is left slightly longer than normal to support the prosthesis, which will need to be left more proud than in standard cases.

 

If the predetermined size of broach is unexpectedly tight, check the entry point and direction of the rasp. The entry point may not be lateral and posterior enough and the rasp may be sitting in varus, with the tip lying up against the lateral femoral cortex.

 

It is important to preserve the strong cancellous bone along the calcar. After final broaching, there should be 4 to 5 mm of cancellous bone available for cement interlock.

 

If the canal is too tight to take even the smallest sized broach from the appropriate offset, try using smaller

offset broaches to start off the process. Also consider the use of a shorter stem prosthesis of the same offset, if available, rather than reverting to power reamers to expand the canal.

 

Pressurization of the cemented canal should be maintained prior to, during, and after insertion of stem and until the cement has completely cured.

 

POSTOPERATIVE MANAGEMENT

A straightforward cemented arthroplasty does not require different postoperative care from any other primary total hip replacement. Full weight-bearing mobilization can be commenced on the day of surgery, and thromboprophylaxis is prescribed depending on the choice of surgeon. Check radiographs, including anteroposterior pelvis with hips, and lateral of the operated hip, are obtained prior to discharge.

 

COMPLICATIONS

The femoral canal is instrumented in any conventional hip arthroplasty, and therefore, there is a risk of fat embolism. The risk is minimized by taking adequate precautions: the canal is washed and aspirated prior to inserting any instrument including canal sizers.

Intraoperative complications specific to cemented stems:

 

Transient drop in blood pressure. The incidence is now less compared with historic figures, probably due to better cleaning of the bone prior to cementing and better anesthetic techniques. The anesthetist is warned prior to cement insertion and any fluctuation in pressure is easily corrected.

 

Cement setting early with incomplete seating of the stem. This should not occur if the cement is kept in the operating room at a constant temperature. However, if this complication should happen, the stem is introduced as far as possible and held in the final position with correct rotation and alignment until the cement has set. If any cement has gone over the shoulder of the implant, it is cleared with a high-speed burr. The stem is then tapped out of the mantle. A cement-in-cement revision (26,27) can then be performed using a shorter stem inserted to the correct depth. If a short stem of the same offset is not available, then the burr should be used to expand and deepen the cavity so that a conventional length stem can be inserted. It is not necessary to disturb the cement-bone interface.

 

Cement escape into the soft tissues. This can occur beneath the abductors during pressurization if the proximal femoral seal is not tight. A finger should always be passed under the abductor muscles at the end of the procedure to check for this. If a cemented stem is to be inserted after removal of a fracture-fixation device (the fixation device should not be removed prior to dislocation of the hip to reduce the risk of intraoperative femoral fracture during dislocation), cement may extrude pressurized through lateral screw holes during pressurization. This is prevented by replacing the removed screws through the lateral cortex only, prior to cement injection. Usually, a membrane has formed around the medial screw holes preventing extrusion. If a dynamic hip screw has been removed, its track through the lateral cortex can be closed using bone graft taken from the femoral head.

The risks to the patient of using a cemented stem are no greater than with the use of a cementless stem. Since aggressive broaching of the canal is not usually necessary and a cemented stem is inserted without the use of a mallet, the risk of intraoperative femoral fracture is less than with a cementless device (28).

 

 

 

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RESULTS

 

Registry Data

The authors will discuss results of one polished tapered cemented stem design, but the reader should be aware that other stem designs with similar properties also have exhibited favorable results. The long-term results of the Exeter stem are excellent regardless of patient age group. Registry data from the National Joint Registry of England and Wales have shown that the Exeter has an early revision rate that is less than half that associated with the best-performing uncemented alternatives at 3 years (0.9% vs. 1.9%) (29). In longer-term analyses, lower overall revision rates were found in the Norwegian Arthroplasty Register in which the Exeter is the best performing cemented stem at 10+ years (30). Independent analysis of data from the National Joint Registry of England and Wales at 5-year follow-up found the Exeter to be functionally the best stem of any design or fixation method, with the lowest revision risk, the best cost-effectiveness, and low mortality in all age groups (31).

Individual Studies

The original Exeter series reached 33-year follow-up in 2008. Although only small numbers of survivors remained, the survivorship of 433 hips at 33 years was 93.5% despite the fact that these cases had been performed with a more primitive cement technique than currently practised (32).

Longer-term follow-up of the modern Exeter stem with a contemporary cementing technique was reported by Carrington who reviewed 325 hips in 309 patients from the Exeter unit. Stem survivorship for aseptic loosening was 100% at 17 years (14) and such excellent results are not restricted to the originating center. Hook et al. (33) reported on a cohort of 142 Exeter stems at mean 12.7 years' follow-up and found aseptic stem loosening in only one case. Young looked at the Exeter stem with an all-polyethylene cemented cup following up 215 patients out to 13 years. Their all-cause survivorship for both components combined was 94.4% at 13 years, and there were no stems revised for aseptic loosening (34).

The excellent results with the Exeter stem are not confined to Western populations. A multicenter study from Japan of 1,000 hips in 881 patients showed a survivorship (for reoperation for any reason) of 98.8% at 5 years. The age range in this group was 23 to 89 years with a mean of 62.3 (35). Chiu et al. (36) highlighted the dangers of oversizing stems in patients from Southeast Asia, for whom the so-called Asia Pacific range of Exeter stems was developed. Shorter, narrower Exeter stems are available with stem length ranging from 90 to 125 mm and with offset of 30, 33, and 35.5 mm. Tai et al. (37) were the first to report the results of these smaller stems, which had an all-cause revision survivorship at 10 years of 95.7% and a survivorship for aseptic loosening of 100%. In an analysis of results from the Australian register, Choy et al. (38) confirmed that the results of the short stems were comparable to those seen with standard-length prostheses.

While the Exeter stem is suitable for young patients, there is a widely held misconception that these patients are better suited to uncemented components. One series of 26 patients with Exeter stems, all of whom were under 40 years old, analyzed survivorship and found 100% stem survivorship at 11 years (39). Similar findings were published by Lewthwaite who assessed the outcome of 130 hips in 107 pts with a mean age of 42 years at the index procedure. At 12.5 years, stem survivorship was 99% (13). De Kam et al. in 2009 reviewed the literature for both cemented and uncemented stem usage in patients less than 50 years of age. They used the criteria set by the National Institute for Clinical Excellence (NICE) on stem choice in total hip arthroplasty (90% survivorship at 10 years) and found 37 series had follow-up of greater than 10 years. Of these, 13 reported on cemented stems that fulfilled the NICE criteria, but only one report concerned the use of uncemented prostheses (and this series used a custom-made prosthesis). They concluded that the most reliable results related to cemented implants.

 

 

CONCLUSIONS

Polished tapered cemented stems are, in our view, the ideal choice for patients undergoing primary hip arthroplasty regardless of age or activity levels. They offer a consistent reproducible technique and longterm results, with control by the surgeon of a patient's offset, leg length, and component anteversion as independent variables. Excellent outcomes have been reported for stems with both a double tapered design and for those with polished triple tapered geometry (6,7,40).

 

 

 

 

ACKNOWLEDGMENTS

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We wish to thank Sophie Kolowska, Media Manager, Hip Unit, Dept of Orthopedics, PEOC, Royal Devon and Exeter Hospital, Exeter, UK, for photography and manuscript layout and Mr. J. Charity, Associate Specialist, Exeter Hip Unit, PEOC, Royal Devon and Exeter Hospital, Exeter, UK, for recent intraoperative images.

 

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