Daniel M. Estok

Total hip arthroplasty with use of so-called second-generation cementing techniques. A fifteen-year-average follow-up study.

One hundred and forty-nine patients (162 hips) had a standard primary total hip arthroplasty with a grit-blasted femoral component and use of so-called second-generation cementing techniques. No patient was lost to follow up. Fifty-one patients (sixty hips) died within fourteen years after the index operation. The remaining ninety patients (102 hips) were followed for a minimum of fourteen years. Of the fifty-one patients (sixty hips) who died within fourteen years, three patients (three hips; 5 per cent) had had a revision: one, because of aseptic loosening of the acetabular component; one, because of aseptic loosening of the femoral component; and one because of aseptic loosening of both components. Of the ninety patients (102 hips) who were alive fourteen years or more (average duration of follow-up, fifteen years) after the arthroplasty, one patient (two hips; 2 per cent) had a revision because of bilateral aseptic loosening of the femoral component. In seven patients (seven hips; 7 per cent), the femoral component loose according to radiographic criteria but was not revised. For the entire group of 162 hips, four femoral components (2 per cent) were revised because of aseptic loosening. In contrast, the rate of aseptic loosening of the acetabular component was higher and continued to increase. Of the eighty-one hips with an all-polyethylene acetabular component in the patients who were alive at fourteen years or more, eight (10 per cent) had a revision because of aseptic loosening. In addition, twenty-eight (42 per cent) of the sixty-seven all-polyethylene acetabular components that were in place after fourteen years or more, and for which there were current radiographs, were loose. Femoral components implanted with the use of second-generation cementing techniques appear to have fared much better than acetabular components that were inserted with similar techniques in this series of patients. A thin (less than one-millimeter) mantle of cement around the femoral component and defects in the mantle of cement were associated with increased loosening of the femoral component.

Mortality After Periprosthetic Fracture of the Femur

BACKGROUND Management of periprosthetic femoral fractures is often complex, and few studies have documented its associated mortality. METHODS We retrospectively identified from our trauma and surgical registries 106 patients who underwent surgery for a periprosthetic femoral fracture. We then identified a contemporaneous age and sex-matched control cohort of 309 patients who had a hip fracture (femoral neck or intertrochanteric) and 311 patients who underwent primary hip or knee replacement. Mortality at one year was identified with use of the Social Security database. RESULTS Twelve (11%) of 106 patients died within one year following surgical treatment of a periprosthetic fracture. During the same follow-up period, fifty-one (16.5%) of 309 patients died following surgery for a hip fracture and nine (2.9%) of 311 patients died following primary joint replacement. The mortality rate after a periprosthetic femoral fracture was significantly higher (p < 0.0001) compared with that for matched patients who had undergone primary joint replacement, and it was similar to the mortality rate after a hip fracture. For periprosthetic fractures, a delay of greater than two days from admission to the time of surgery was associated with an increased mortality rate at one year (p < 0.0007). Forty-nine patients underwent revision arthroplasty for the treatment of a Vancouver type-B periprosthetic fracture, and six (12%) died. In contrast, twenty-four patients with a Vancouver type-B periprosthetic fracture were treated with open reduction and internal fixation and eight (33%) died. The difference was significant (p < 0.03). CONCLUSIONS The mortality rate within one year following surgical treatment of periprosthetic femoral fractures is high and is similar to that after treatment for hip fractures. Because revision arthroplasty for the treatment of type-B periprosthetic fractures was associated with a one-year mortality rate that was significantly less than that after surgical treatment with open reduction and internal fixation, in instances when either treatment option is feasible, revision arthroplasty may be the preferred option.

Experimental assessment of precision and accuracy of radiostereometric analysis for the determination of polyethylene wear in a total hip replacement model

The purpose of this study was to develop and test a phantom model based on actual total hip replacement (THR) components to simulate the true penetration of the femoral head resulting from polyethylene wear. This model was used to study both the accuracy and the precision of radiostereometric analysis, RSA, in measuring wear. We also used this model to evaluate optimum tantalum bead configuration for this particular cup design when used in a clinical setting.

Evaluation and management of the infected total hip and knee.

Infection should be in the differentia for any painful total hip or knee. A thorough history and physical, complete set of radiographs and appropriate labs including C-reactive protein and erythrocyte sedimentation rate are essential in the initial evaluation. Ancillary tests such as aspiration and nuclear imaging may be helpful in unclear cases or when labs are concerning for infection. It is essential that all antibiotics are discontinued several weeks prior to gram stain and culture, if possible, to reduce the number of false negative test results. Classifying infection into acute versus late infection aids in the treatment plan. For acute infections presenting within 2 to 4 weeks of symptom onset, irrigation and debridement with polyethylene liner exchange and retention of components may be possible. When attempting component retention, thorough debridement and rapid treatment of the infection prior to the accumulation of any biofilm is paramount for a successful outcome. Other important prognostic factors to consider include the virulence of the microorganism as well as the immune status of the host. Despite expeditious management, irrigation and debridement of acute total hip and knee infections frequently leads to recurrent infection. Thus, patients should be counseled accordingly. Further management may be needed following an initial attempt at component retention. These options include resection arthroplasty with or without re-implantation, long term antibiotic suppressive therapy, arthrodesis and even above the knee amputation in rare circumstances. For chronic infections, a successful outcome depends on several factors including the baseline health status of the patient, implant removal with a thorough debridement followed by culture specific antibiotic treatment. Furthermore, methods of monitoring for persistent infection include following laboratory values such as the C-reactive protein, erythrocyte sedimentation rate, and cultures from joint aspirations. Whether to perform a direct exchange versus a delayed revision arthroplasty for chronic total hip and knee infections can be debated. Several published series have reported successful outcomes with single stage procedures when patients are carefully selected. However, the majority of chronic infections in the United States are treated with two stage resection, since this method has consistently provided the highest cure rates, with many current studies demonstrating >90% success.

Total Hip Arthroplasty with Use of Second-Generation Cementing Techniques. An Eighteen-Year-Average Follow-up Study*

In this report, we present the results of a further follow-up of a series of 140 consecutive patients (161 hips) who had had a primary total hip arthroplasty with insertion of a bead-blasted monoblock femoral component with use of so-called second-generation cementing techniques. The average age of the patients at the time of the arthroplasty was sixty-one years (range, twenty-one to eighty-five years). Sixty-seven patients (seventy-seven hips) died less than seventeen years after the index operation. The remaining seventy-three patients (eighty-four hips) were followed for an average of eighteen years (range, seventeen to twenty years). No patient was lost to follow-up. In the entire group of 161 hips, over the twenty-year span of the study, eight femoral components (5 percent) and twenty-eight acetabular components (17 percent) had been revised because of aseptic loosening. Of the seventy-seven hips in the sixty-seven patients who died, four had been revised because of aseptic loosening of the acetabular component only; one, because of aseptic loosening of the femoral component only; and one, because of aseptic loosening of both components. Of the eighty-four hips in the seventy-three patients who were alive at least seventeen years after the index arthroplasty, twenty-four hips (29 percent) in twenty-one patients had had revision of one or both components for any reason. Twenty-three acetabular components (27 percent) and six femoral components (7 percent) had been revised because of aseptic loosening. An additional two hips (2 percent) in two patients were loose according to radiographic criteria but had not been revised. Of the sixty-five all-polyethylene acetabular components that had been inserted with cement and were in patients who were alive at least seventeen years postoperatively, fifteen (23 percent) had been revised because of aseptic loosening. An additional seventeen cups (26 percent) were loose according to radiographic criteria. Thus, a total of thirty-two cups (49 percent) had been revised because of loosening or were loose but had not been revised at the time of the latest follow-up. The femoral components that had been inserted with use of second-generation cementing techniques fared better than did the acetabular components that had been inserted with these techniques during the same time-period. We found that assessment of all postoperative radiographs rather than only those that had been made immediately postoperatively increased the accuracy of the grading of the cement around the femoral component. Subsequent radiographs frequently had been made at different projections, which revealed new findings, consisting primarily of previously undetected voids, areas of thin cement, and defects in the cement mantle. Thus, we now use all available radiographs to determine the grade of the cement.

Factors affecting cement strains near the tip of a cemented femoral component

A generic three-dimensional finite-element model of the upper half of the femur containing a cemented femoral stem of a total hip arthroplasty was developed to study those factors influencing cement strains near the tip of a cemented femoral component. This generic model was verified through another three-dimensional finite-element model that had been created based on the precise geometry of a cadaver femur implanted with a contemporary cemented femoral component. This cadaveric femoral reconstruction had been created with strain gauges embedded in the cement mantle and was then loaded under conditions simulating single leg stance and stairclimbing. By use of the cement strains measured experimentally in the cadaver femur, and comparison of them with those obtained from the finite-element model of that cadaver femur, it was possible to establish proper material properties, boundary conditions, and loading conditions for the generic model. The generic model was then modified parametrically to determine those factors that influence the strains occurring within the cement mantle near the tip of a cemented femoral component. These models suggest that the single factor that most adversely influenced peak strains at or near the tip of the prosthesis was a thin cement mantle. This effect was present both when the cement mantle was reduced in thickness and when a similar effect occurred by virtue of a varus or valgus placement of the stem. Factors that decreased the peak cement strains near the tip of the femoral stem included a more flexible stem and thicker cement mantles. This effect of a more flexible stem could be obtained by changing the modulus of the metal implant by uniformly reducing the thickness of the stem, or by tapering the stem within the same bone geometry. Thicker cement mantles reduced both the axial and the shear strains occurring at the tip of the prosthesis. The presence or absence of a hole in the tip of the prosthesis per se, as for a centralizer, had no significant effect on the peak cement strains seen around the tip of the prosthesis; however, truncating the tip of the prosthesis from a hemisphere to a flat profile, which resulted in a sharp corner at the tip of the prosthesis, produced a 35% increase in cement strains at the tip as a result of a stress concentration effect. Thus, the common way of modifying the tip to have a hole for a centralizer, which involved truncating the tip, increased the cement strains occurring near the tip of the prosthesis.

20-year experience with cemented primary and conversion total hip arthroplasty using so-called second-generation cementing techniques in patients aged 50 years or younger

We present the 20-year experience of 47 hips in 40 patients aged 50 years or younger with cemented primary total hip arthroplasty using second-generation femoral cementing techniques. Average follow-up duration in the 23 patients living at least 17 years was 18.2 years. Overall, 18 hips (38%) had components revised or removed for any reason, at an average duration of 12.6 years. Every revision or reoperation involved removing the acetabular component. Of these 18 acetabular components, 15 (32%) were revised for aseptic loosening. Eleven additional acetabular components were loose by radiographic criteria at final follow-up, yielding prevalence of aseptic acetabular loosening (55%). Four femoral components (8%) were revised for osteolysis without loosening, and 3 (6%) were revised for aseptic loosening. Femoral osteolysis, with or without component loosening, led to revision in 5 ( 11%) hips compared with 6% for aseptic loosening alone. Osteolysis was the primary problem leading to acetabular and femoral component revision in this series of people < or = 50 years old over the first 20 years after the index operation.

Long-term results of cemented femoral revision surgery using second-generation techniques : an average 11.7-year follow-up evaluation

From a group of 43 hips in 41 patients, previously reported at an average of six years of follow-up evaluation, in whom second-generation cementing techniques were used during femoral revision hip surgery, 38 hips in 36 patients were rereviewed at an average follow-up period of 11.7 years (range, 118-172 months). The average age of the patients at the time of revision surgery was 52.8 years. Only four femoral components (10.5%) required rerevision for aseptic loosening. Of those not rerevised, the average Harris hip score at the time of follow-up evaluation was 81. Four additional hips (10.5%) had radiographic evidence of definite femoral component loosening. The survival of 90% of the implants of cemented femoral revision surgery and the 79% incidence of well-fixed femoral components for more than 11.7 years is attributed to the improved cementing techniques and modern stem design.

Comparison of femoral head penetration using RSA and the Martell method.

Radiostereometry has high precision and accuracy measuring polyethylene wear in total hip arthroplasty but requires a specialized setup. The Martell method is simpler and can be used on larger populations. The hypothesis that the radiostereometry analysis and the Martell analysis would yield comparable wear data from the same group of patients having total hip arthroplasty was tested. A group of twenty-five total hip arthroplasty patients who had both radiostereometry and standard anterior-posterior pelvic and cross-table lateral radiographs of sufficient quality for analysis were identified. The films were taken at postoperative periods of 6 weeks, 1 year, 2 years, and 5 years. Femoral head penetration was measured by both methods at each time point. The median penetration rates measured by each method decreased over time. Penetration results were affected by method of analysis, time, and dimension, with greater penetration for Martell compared with radiostereometry at each time point, greater penetration with increasing time for each method, and larger three-dimensional magnitude compared with two-dimensional analysis. Level of Evidence: Case series Level IV. See Guidelines for Authors for a complete description of levels of evidence.

Interprosthetic fractures of the femur: treatment with a single-locked plate.

Interprosthetic fractures of the femur, those between an ipsilateral hip and knee arthroplasty, are challenging to treat secondary to limited bone available for fixation, osteopenic bone, a compromised intramedullary blood supply, and an often elderly patient population. From 2002 to 2006, 22 consecutive patients with an interprosthetic femur fracture were treated with a single-locking plate. Follow-up averaged 17.7 months, with fracture union achieved an average of 13.8 weeks postoperatively. All patients regained their preoperative ambulatory status and subjectively reported unchanged function of their hip and knee arthroplasties. Single-locked plating is an effective method of treatment of interprosthetic fractures of the femur. Emphasis on preservation of the soft tissue envelope and sufficient cortical purchase both above and below the fracture is of paramount importance.