Cemented Long Stems for Revision Total Hip Arthroplasty: Do’s and Don’ts






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CHAPTER SYNOPSIS:




  • 1

    Cemented femoral revision serves as an option for patients who are elderly, are low demand, have poor femoral bone stock, are at high risk for fracture, and have limited potential for biologic fixation (e.g., Gaucher disease, radiation therapy).


  • 2

    Cement within cement is an option when a well-fixed cemented stem requires revision.


  • 3

    The use of cement in revision total hip arthroplasty allows the placement of antibiotics within the cement, resulting in high-dose elution of the antibiotics. Antibiotic-laden cement typically is used in reimplantation or cases suspected of infection.


  • 4

    In addition, cemented femoral revision can be done in conjunction with impaction grafting in younger patients with significant bone loss, particularly when rotational stability would be difficult to obtain with use of a cementless device.





INTRODUCTION


Total hip arthroplasty (THA) has become one of the most common and successful orthopedic procedures performed, with approximately 200,000 replacements being done annually in the United States. Given the fact that THA is being performed on younger, more active patients, and recognizing the increased life span of typical patients, implant survival is critical to attaining a successful clinical outcome. That being said, the rate of revision THA will inevitably increase as younger patients undergo hip replacement procedures.


Dating back to the middle of the twentieth century, Sir John Charnley’s experience with early THA resulted in a high degree of failure from a multitude of mechanisms, primarily sepsis. Regarding the acetabular component, the most common aseptic cause for failure was loosening. As the issue of environmental sterility was addressed and the technique of acetabular component press-fit implantation changed to cementation, acetabular issues resulting in revision surgery decreased. Switching focus to the femoral component, certain issues became more apparent as the incidence of mechanical failure increased, resulting in aseptic loosening, periprosthetic fracture, and pericomponent osteolysis; these modes of failure were early indications for revision surgery.


Serial radiographs were soon recognized to be an excellent tool for detecting mechanical failure of the femoral component. Radiographs were evaluated for component migration, cement mantle defects with component subsidence within the cement or subsidence of the cement within the femoral canal, and evidence of progressive widening or presence of radiolucent lines surrounding the prosthesis. As loosening became a clear indication for revision surgery, cement technique for femoral component fixation began to play a critical role in the success of revision THA.


In the early era of hip replacement surgery in the United States, low-demand and elderly patients typically were considered ideal candidates for primary THA. As a result, symptomatic mechanical failure of the femoral component was less commonly seen during the 1960s and 1970s. As the surgical indications for primary THA widened, a concomitant rise occurred in the need for surgical techniques for hip revision procedures. The goals of revision THA have always been to achieve a durable construct, implant a stable device, preserve joint stability, and restore proximal bone stock. Because primary cemented femoral components had performed reasonably well and better than most first-generation cementless components, most femoral revision procedures initially were managed with cemented femoral revision. Since the early experience with cemented femoral revision, however, cementless devices have been developed that have allowed excellent long-term fixation with cementless devices that allow bone ingrowth or ongrowth on the entire prosthetic surface or are modular and allow biologic fixation in compromised bone.


This chapter is designed to depict the appropriate use of cement in revision THA, specifically femoral component revision. With a focus on factors such as proximal femoral bone quality, improved cementation technique, use of long stems, appropriate patient selection, optimized cement mantle biomechanics, and the use of enhanced component technology, methods by which to achieve clinical success with the use of cemented femoral fixation are reviewed. A revolution has taken place over the past half-decade, resulting in the currently accepted indications and techniques for the use of cement in femoral revision THA.




EARLY RESULTS OF CEMENTED AND CEMENTLESS REVISION FEMORAL STEMS


Early results of cemented femoral stems in the setting of revision THA were disappointing. With relatively new emerging surgical techniques and ill-defined surgical indications for cemented femoral revision, initial results were poor, especially with the use of first-generation cementing technique. Hunter et al reported an infection rate of 32% after 140 THA revisions over a 10-year period. In 22% of cases resection arthroplasty was required for treatment and only 24% of patients exhibited good to excellent clinical outcomes. Amstutz et al also demonstrated discouraging results in 66 patients followed up for a mean of 2.1 years. The repeat revision rate was 9%, and radiographic changes predicted an additional 29% of cases would require future revision. Wroblewski found that 28% of 94 cases followed up for more than 2 years showed radiographic evidence of future mechanical failure. This study further highlighted the concern of radiographic evidence of loosening and its effect on the potential need for future revision.


Several subsequent studies reported similar short-term results after cemented femoral revision. Pellicci et al, Kavanagh et al, and Callaghan et al reported repeat revision rates of 4.3% to 6.3% and radiographic loosening of 12% to 44%, with a mean time to follow-up ranging from 3.4 to 4.5 years. A follow-up report by Pellicci et al demonstrated more than double the rate of repeat revision (19%) and radiographic loosening (13.6%) seen with the original cohort of patients studied in 1982.


Callaghan et al used improved cement technique with the addition of an intramedullary plug and a cement gun for introduction of the cement into the femoral canal. Regardless of improved cement technique, these authors reported mechanical failure in nearly 16% after revision THA. They attributed mechanical failure with progressive radiolucent lines to poor proximal femoral bone quality.


The initial results after revision of the femoral component were poor, with a high degree of mechanical failure and radiographic evidence of loosening. At this early stage the factors associated with poor outcomes after revision THA were assumed to include more than simply an inadequate bone-cement interface. Well-preserved proximal femoral bone stock also was determined to be critical to implant longevity. The combination of improved cement technique with adequate cancellous bone for cement interdigitation would be the ideal scenario for revising the femoral component.


The suboptimal results after cemented femoral revisions led to an increased enthusiasm for cementless femoral stems in revision THA. However, mid-term results with cementless stems also were unsatisfactory. Studies demonstrated failure rates as high as 27% 5 years after revision, femoral osteolysis rates of nearly 70% at 2 years, and minimal or completely absent bone/biologic ingrowth in 80% of cases. Engh et al reported stem loosening rates after cementless revision as high as 18%. In addition, repeat revision rates were as high as 16% nearly 3 years after revision surgery. Several other authors portrayed similar results with various cementless devices.


Simultaneously, orthopedic surgeons also continued to perform cemented femoral revisions and began to report improving clinical outcomes. Raut et al reviewed 351 cemented femoral revisions done for aseptic loosening. At an average 6 years of follow-up, more than 70% of patients were pain free, and radiographic evidence showed definite femoral component loosening in only 10 hips (2.8%). A total of 20 hips (5.7%) required repeat revision, of which nine (2.6%) were attributable to mechanical failure. With repeat revision as an end point, femoral stem survival was calculated to be 97% at 8 years and 91.6% at 11 years. As a result, emphasis was again placed on future studies for the use of cemented femoral revision components with a focus on improved cement techniques, optimizing remaining proximal femoral bone stock, use of long stems, patient age, and biomechanics of the cement-prosthesis interface.




CEMENT TECHNIQUE


Over the past half-century, significant changes have been made to how cement is used to secure implants in THA. Initial first-generation techniques involved finger packing of cement and no canal preparation or placement of a cement plug. The cement was introduced into the canal without using a cement gun and without pressurization. The early 1970s experienced the advent of a cement gun, which was used to introduce the cement into the femoral canal, and arthroplasty surgeons began to prepare the canal with a brush, irrigated the canal with pulsatile lavage, and thoroughly dried it before introducing the cement. A cement restrictor was routinely placed in the canal and a collared stem typically was used to prevent subsidence of the stem within the cement mantle. These changes were classified as second-generation cement technique. During the next decade a subsequent set of changes constituted third-generation cement technique. The addition of vacuum mixing of the cement reduced the degree of porosity while the cement was pressurized during introduction into the femoral canal. A stem centralizer was used to facilitate stem placement within the cement, allowing a uniform mantle to surround the prosthesis. In the setting of primary THA, cement technique was recognized as an important factor for achieving long-term implant fixation. Third-generation cement technique is still currently used as the ideal method for femoral component cementation.


Early studies in the literature demonstrated rates as high as 30% to 40% at 10 years for femoral component loosening with the first-generation cement technique. Improved cement techniques reduced the rate of femoral loosening to as low as 3% at 11-year follow-up. The increased risk of femoral component loosening with first-generation cementation was suspected to be attributable to inadequate microinterlock with the patient’s host bone.


During the early era of cemented revision THA in the United States, first-generation cement technique was considered a significant factor resulting in the limited success seen with index femoral revision. With increased surgeon experience with revision surgery and the advent of technologic advances in cement technique, researchers began to look at the effect of technical improvements on clinical and radiographic outcomes in revision THA. The hypothesis was that the reduction in femoral component loosening seen in primary THA as a result of improved cement techniques also would hold true for femoral revisions, yielding an increased overall longevity of the implant.


Rubash and Harris reported on a consecutive series of 41 patients (43 hips) who underwent a femoral component revision with second-generation cement technique. Mid-term follow-up at 6 years demonstrated only one patient (2%) requiring repeat revision and three additional patients with radiographic evidence of aseptic loosening. Estok and Harris reviewed 36 patients (38 hips) after revision THA with second-generation cement technique. This was a follow-up study, with mean follow-up time of 11.7 years, of the original cohort of 41 patients (mean age, 52.8 years) assessed at 6 years. Six patients in the original group had died, but one of these patients was seen 2 months before his death and was included in the data. At final evaluation, an additional three or a total of four femoral components (10.5%) required repeat revision for aseptic loosening, and an additional three stems or four total (10.5%) were radiographically loose. The authors concluded that the 90% implant survival and 79% incidence of well-fixed femoral components was attributable to improved cement technique.


This same cohort of patients was evaluated at an average 15.1 years after revision THA. Three additional patients were dead at time of final follow-up, leaving a total of 33 surviving patients for final assessment. Seven patients (20%) with a mean age of 51 years underwent repeat revision of the femoral component for aseptic loosening. Two additional patients had radiographic evidence of loosening, resulting in an overall loosening rate of 26% at 15 years. The decreased prevalence of aseptic loosening after femoral component revision when compared with prior short-term studies was attributed to improved second-generation cement technique.


The concept of enhanced implant longevity as a result of improved cement technique was further supported by Katz et al. In this study the authors reported a minimum of 10-year follow-up data on 73 patients (47 patients with radiographs at final follow-up) after revision THA with second-generation cement technique. The mean patient age was 64 years and average follow-up time was 11.9 years. The repeat revision rate was 9.5% and radiographic evidence of femoral component loosening was present in 26.1% of patients. One patient underwent repeat revision for septic failure within 1 year of the index revision THA. Comparing this data to historic controls with early cement techniques, the use of second-generation cementation resulted in improved clinical and radiographic results. Thorough removal of the neocortex or fibrous membrane along the prosthesis-bone interface at the time of revision was recognized as critical to allow the cement to better interdigitate with host bone. This led to the speculation that improved cement techniques in conjunction with adequate cement interdigitation were responsible for the improved clinical outcomes observed with femoral component revision.


Third-generation cement technique in the mid-1980s brought about the addition of vacuum mixing to minimize cement porosity before implantation. Eisler et al reviewed 83 consecutive femoral component revisions with third-generation cement technique. At a median follow-up of 3.6 years (range, 1.5 to 6.6 years), the failure rate for the femoral component was 39% based on the number requiring repeat revisions and radiographs suggesting aseptic loosening. When radiographic loosening was used as an end point, the data showed that the quality of the cement-bone interface obtained at the time of the index revision was the only significant factor in predicting durability of the stem, with an odds ratio of 1.8. This study showed that the addition of vacuum mixing did not have a significant impact on the longevity of femoral component revisions.


As a result, factors other than cement technique alone were postulated to be integral in obtaining long-term success in femoral revision surgery. A prospective study looked at the effect of several different patient and implant factors, excluding cement technique, on the longevity of femoral component revision. A total of 109 consecutive femoral stem revisions were assessed at a minimum follow-up of 7 years (range, 7 to 13 years). Specifically, patient age, use of standard versus long stems, and the presence of radiolucent lines on postoperative radiographs were evaluated. Patients were clinically and radiographically monitored, with repeat revision, prosthesis removal, or patient death defined as end points. Revisions were done with second- or third-generation cement techniques (third-generation cementation was used in the late 1980s). A statistically significant increase in the risk for repeat revision was seen with younger patients ( P = .0001) and the use of standard stems ( P = .002). Radiographic evidence showed an increased risk for developing mechanical failure in younger patients ( P = .0001), presence of proximal femoral bone defects ( P < .005), use of standard stems ( P < .0005), and presence of radiolucent lines on postoperative radiographs ( P < .01). No differences were found in the clinical or radiographic outcomes in patients who received second- or third-generation cemented stems. The authors concluded that cemented revision was a durable option for older patients when longer stems were implanted with improved cement technique.


Additional studies also confirmed favorable outcomes after revision THA with the use of long stems. Turner et al evaluated 165 long-stem (more than 200 mm) cemented femoral revisions for clinical and radiographic success at a mean follow-up of 6.7 years. They reported a repeat revision rate of only 10%, with an average time to failure of 4.6 years. At final follow-up 10% of patients had radiographic evidence of radiolucency involving 50% of the cement-bone interface. The authors concluded that long-stem cemented femoral components minimized the degree of radiolucency and decreased the progression of radiographic loosening, leading to lower rates of future mechanical failure.


Retpen and Jensen similarly reported clinical success with long-stem femoral devices. The authors postulated that recurrent loosening was more likely if the revision stem did not bypass any residual femoral cortical defects by at least one cortical diameter. Subsequent reports in the literature did not support this hypothesis. Kavanagh and Fitzgerald documented a radiographic loosening rate of 40% versus 20% for long stems and standard-length stems, respectively. Regardless of these somewhat conflicting reports, the revision stem was determined to need to bypass any cortical defects by two cortical diameters to minimize the risk for periprosthetic fracture.


Patient age at time of revision also was discovered to be an important factor in determining the success of femoral revision. Young patient age was identified as being a risk factor for recurrent loosening after cemented femoral revision. Izquierdo and Northmore-Ball reported 10-year results on 148 consecutive second-generation technique cemented femoral component revisions in patients with an average age of 67 years. The overall survival rate was 95%, with repeat revision defined as the end point. The success rate was determined to be attributable to improved cement technique in conjunction with elderly patients.


Stromberg et al further addressed the issue of patient age as it related to cement technique. The authors reviewed 70 hips (68 patients) 7 years after first-time cemented revision THA with second-generation cement technique. The average age of the patient at time of revision was 47 years, and repeat revision for aseptic loosening was the end point for survival analysis. The overall survival rate was 76% compared with 62% ( P = .0458) for the authors’ previous study, which used first-generation cement technique. This trend was maintained when assessing the revision of the femoral component alone, with an improvement in success rates from 69% to 85% ( P = .079). These outcomes were attributed to improved cement technique because the average patient age was less than 55 years for both studies.


Estok and Harris reported very satisfactory results at 12-year follow-up of 36 patients with an average age of 53 years. The authors reported 90% survival of the revised femoral component with second-generation cement technique. The long-term success was speculated as being a function of cement technique and not patient age because nine cases (24%) with radiographic evidence of localized osteolysis were reported but not classified as being loose.

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Jan 26, 2019 | Posted by in ORTHOPEDIC | Comments Off on Cemented Long Stems for Revision Total Hip Arthroplasty: Do’s and Don’ts
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