JBJS | The Fate of Well Fixed Cemented Femoral Components Left in Place at the Time of Revision of the Acetabular Component*

The Journal of Bone & Joint Surgery, Volume 79, Issue 5

Articles | May 01, 1997

The Fate of Well Fixed Cemented Femoral Components Left in Place at the Time of Revision of the Acetabular Component*

CHRISTOPHER L. PETERS, M.D.†; LAURA KULL, M.S., R.N.†; JOSHUA J. JACOBS, M.D.†; AARON G. ROSENBERG, M.D.†; JORGE O. GALANTE, M.D.†, CHICAGO, ILLINOIS

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Investigation performed at Rush-Presbyterian-St. Luke's Medical Center, Chicago

The Journal of Bone & Joint Surgery. 1997; 79:701-6

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Abstract

The results were reviewed for thirty-seven hips (thirty-five patients) in which a well fixed femoral component that originally had been implanted with use of a so-called first-generation cementing technique was subsequently left in place at the time of revision of the acetabular component without cement. The purpose of the study was to determine the rate of survival of the femoral component and the complications associated with revision of one side of the joint. The femoral components had been in situ for a mean duration of 102 months (range, twelve to 216 months) at the time of the revision of the acetabular component.At the time of follow-up after the revision of the acetabular component, one patient (one femoral component; 3 per cent) had died, twenty-seven femoral components (73 per cent) were in place and radiographically stable, one femoral component had been removed because of infection, six (16 per cent) had been revised because of aseptic loosening, and two (5 per cent) were definitely loose according to radiographic criteria. Excluding the failures and death, the mean duration of follow-up was sixty-five months (range, forty-eight to 121 months). The predicted survival of the femoral component after the revision of the acetabular component was 88 per cent (95 per cent confidence interval, 82 to 94 per cent) at forty-eight months and 78 per cent (95 per cent confidence interval, 67 to 89 per cent) at eighty-eight months. Dislocation occurred in three hips (8 per cent), and a trochanteric non-union occurred in five (14 per cent). The mean rate of linear polyethylene wear did not differ significantly (0.13 as compared with 0.12 millimeter per year; p = 0.74) from that for a comparable group of forty-nine hips that had had a revision of the femoral component without cement and had been followed for a similar duration.The data support the decision to retain a well fixed femoral component that has been implanted with a so-called first-generation cementing technique when the acetabular component subsequently needs a revision. The survival of the femoral component and the risk of associated complications do not appear to be appreciably altered by revision of the other side of the joint.

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Introduction

Introduction | Materials and Methods | Results | Discussion | References

Long-term follow-up studies of total hip replacements performed with cement have documented that the rate of failure of cemented femoral components is distinct from that of cemented acetabular components^{5,7-9,12,18,19,21,22,32,33,38,40}. The rate of mechanical failure of cemented femoral components has been reported to range from 1.7 per cent (three of 173 hips) to 30.4 per cent (sixty-three of 207 hips) after ten years of follow-up, whereas the rate of failure of cemented acetabular components tends to accelerate with time, especially after ten years, when the rates of loosening may approach 55 per cent (sixty-one of 111 hips) to 64 per cent (eighty-seven of 136 hips)^{1,5-9,12,13,19,21,25,33,34,38,40,41}.

A consequence of the different rates of failure is that in the second decade after the primary total hip replacement many patients have a well fixed femoral component and a loose acetabular component that is in need of revision. The surgeon therefore must decide whether to revise or retain the femoral component at the time of the revision of the acetabular component. Such a decision must be based on several factors, including the long-term prospects for survival of the implant, the condition and compatibility of the implant-bearing surface, the stability of the prosthesis (a situation made more complex by the fact that femoral components implanted with a so-called first-generation cementing technique were non-modular), and an analysis of the risks and benefits of revision.

The purpose of the current study was to determine the fate of, and the complications associated with, well fixed femoral components that had been implanted with a so-called first-generation cementing technique and left in place at the time of revision of the acetabular component. It was our hypothesis that retention of a well fixed cemented femoral component would not adversely affect the subsequent rates of survival and complications associated with the arthroplasty as compared with the rates for historical controls.

*One or more of the authors have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article. In addition, benefits have been or will be directed to a research fund or foundation, educational institution, or other non-profit organization with which one or more of the authors are associated. Funds were received in total or partial support of the research or clinical study presented in this article. The funding source was Zimmer, Incorporated, Warsaw, Indiana.

†Department of Orthopaedic Surgery, University of Utah School of Medicine, 50 North Medical Drive, Salt Lake City, Utah 84132. Please address requests for reprints to Dr. Peters. E-mail address for Dr. Peters: chris.peters@hsc.utah.edu.

‡Department of Orthopaedic Surgery, Rush-Presbyterian-St. Luke's Medical Center, 1725 West Harrison Street, Suite 1063, Chicago, Illinois 60612.

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Fig. 1 Kaplan-Meier²⁰ survivorship curve for the well fixed cemented femoral components that were left in place at the time of the revision of the acetabular component. Failure is defined as revision or definite loosening of the femoral component. The dotted lines represent the confidence interval.

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

From April 1984 to October 1990, 381 consecutive revisions of the acetabular component were performed without cement at Rush-Presbyterian-St. Luke's Medical Center in Chicago. The patients were followed prospectively with use of a computerized database. Two hundred and ninety-six hips (78 per cent) had revision of both the acetabular and the femoral component; 190 revisions of the femoral component were performed without cement, and 106 were performed with cement. Eighty-five hips (22 per cent) had revision of only the acetabular component. In forty-eight of these hips, a modular femoral component that originally had been implanted with or without cement was left in place. In the other thirty-seven hips, a non-modular femoral component that had been implanted with a so-called first-generation cementing technique was left in place. This subgroup was chosen for analysis because there was no opportunity to exchange the femoral bearing surface. First-generation cementing methods were characterized by finger-packing of the cement without lavage of the femoral canal, no use of porosity-reduction techniques, no pressurization of the cement, and the absence of an intramedullary plug or a centralization device.

All revisions of the acetabular component were performed with use of a hemispherical porous-ingrowth socket made of commercially pure titanium (Harris-Galante; Zimmer, Warsaw, Indiana). Twelve hips (32 per cent) were exposed through an anterolateral approach, and twenty-five (68 per cent) were exposed through a standard trochanteric osteotomy or a trochanteric slide osteotomy.

The criteria that we established for retention of the femoral component were determined retrospectively and included (1) no complete radiolucent line at the cement-bone interface and no radiolucent line at all at the stem-cement interface, as seen on the preoperative anteroposterior and lateral radiographs of the femur, and no evidence of increased radionuclide uptake in the proximal part of the femur, as seen on a technetium bone scan; (2) no evidence of motion of the implant or the mantle of cement, as seen intraoperatively; (3) no evidence of excessive wear or deformation of the femoral head as seen intraoperatively; and (4) adequate stability of the implant after revision of the acetabular component. The patient's age, medical condition, and level of activity were not generally considered in the decision whether to retain a well fixed component.

Excluding the patients who had failure of the revision and the patient who died, the thirty-five patients (thirty-seven hips [two revisions were bilateral]) were followed for a mean of sixty-five months (range, forty-eight to 121 months) after the revision of the acetabular component. There were twenty-eight women (mean weight, sixty-two kilograms; range, forty-two to ninety-five kilograms) and seven men (mean weight, seventy-eight kilograms; range, forty-two to ninety-two kilograms); the mean age of the patients was fifty-three years (range, twenty-eight to eighty-three years). The revision involved sixteen right hips and twenty-one left hips. The primary condition that had led to the original arthroplasty was osteoarthrosis for twenty-four hips, rheumatoid arthritis for five, aseptic necrosis for four, a femoral fracture for two, and takedown of a fusion for two. One patient who had a well fixed femoral component and a well functioning hip died thirty-eight months after the revision of the acetabular component. In a second patient, both the revised acetabular component and the retained femoral component were removed because of infection twelve months after the revision of the acetabular component.

The femoral replacement had been performed with a Charnley-Müller component (Protek, Bern, Switzerland) in twelve hips; a Charnley component (Thackray, Leeds, England) in nine hips; an Aufranc-Turner component (Howmedica, Rutherford, New Jersey) in five hips; a Müller component (Protek) in four hips; a Harris Design-2 component (Howmedica) in two hips; and a Trapezoidal-28 component (Zimmer), a 6-Ti-32 component (Zimmer), a calcar-replacement Harris component (Zimmer), a computer-assisted-design (CAD) component (Howmedica), and a Bechtol component (Richards, Memphis, Tennessee) in one hip each.

At the time of the revision of the acetabular component, the femoral component had been in place for a mean of 102 months (range, twelve to 252 months). Twenty-nine femoral components had been placed in a primary procedure; three, in a revision performed because of a failed surface replacement; and five, in a revision performed because of a failed primary total hip replacement.

The patients were followed prospectively after the revision of the acetabular component. Clinical assessment was performed at six weeks, three months, six months, twelve months, and annually thereafter with use of the Harris hip score (maximum score, 100 points)¹⁶. The results were classified as excellent (90 to 100 points), good (80 to 89 points), fair (70 to 79 points), or poor (less than 70 points). The clinical evaluation also included an analysis of complications, including reoperation, dislocation, trochanteric non-union, and secondary operative procedures.

Preoperatively and at the follow-up intervals, the radiographs were evaluated with regard to the position of the femoral component relative to the long axis of the femur (on the anteroposterior radiograph), subsidence of more than two millimeters or an angulatory change of more than 2 degrees within the mantle of cement, a radiolucent line at the stem-cement or bone-cement interface in the zones described by Gruen et al.¹⁴ (on the anteroposterior and lateral radiographs), fracture of the stem, evidence of osteolysis, and the rate of linear wear of the polyethylene liner²³. On the basis of the radiographic appearance, the femoral component was classified as stable, definitely loose, probably loose, or possibly loose, as described by Harris et al.¹⁷. The acetabular component was evaluated for migration, radiolucent lines, and osteolysis, in the manner described by Padgett et al.²⁷.

In addition to the preoperative plain radiographs of the femoral components, a technetium bone scan was made, at the discretion of the attending surgeon, for thirty-one hips. All thirty-one had increased radioisotope uptake surrounding the loosened acetabular component without increased uptake surrounding the femoral component. These data were used, in conjunction with the preoperative clinical and radiographic data, to support the decision to leave the femoral component in place at the time of the revision of the acetabular component.

Statistical analysis with use of the Wilcoxon rank-sum test was performed to determine if the fate of the femoral component was related to the patient's preoperative age and weight, the duration that the femoral component had been in situ, the preoperative Harris hip score, or the preoperative position of the femoral component. The Wilcoxon rank-sum test also was used to determine the significance of differences in the mean annual Harris hip score for the entire population of patients. Survivorship analysis was performed according to the method of Kaplan and Meier²⁰.

Results

Introduction | Materials and Methods | Results | Discussion | References

Eight (22 per cent) of the thirty-seven femoral components either were revised because of aseptic loosening or were definitely loose and were considered to have failed mechanically. Six femoral components (16 per cent) were revised because of aseptic loosening, and two (5 per cent) were definitely loose but had not yet been revised. At the time of the revision of the acetabular component, there was no difference in the mean duration in situ for the femoral components that subsequently needed a revision as compared with that for the femoral components that did not (107 as compared with 103 months; p = 0.42).

The Harris hip score for the over-all population of patients improved from a mean value of 50 points (range, 25 to 73 points) preoperatively to a mean value of 77 points (range, 35 to 100 points) at the latest follow-up evaluation (p < 0.001). There was also a significant improvement in the individual scores for pain (from a mean of 21 [of a possible 44] points preoperatively to a mean of 38 points postoperatively; p < 0.001), limp (from a mean of 2.6 [of a possible 11] points to a mean of 7 points; p < 0.001), and the need for support when walking (from a mean of 6 [of a possible 11] points to a mean of 8 points; p = 0.01). There was no significant difference in the preoperative total score between the patients who subsequently did not have failure of the femoral component and that of the patients who had failure of the femoral component (mean, 48 points [range, 25 to 73 points] as compared with 55 points [range, 37 to 76 points]; p = 0.16). Although there was a difference in the Harris hip score at the latest follow-up evaluation between the patients in whom the femoral component had not failed and those in whom it had (mean, 81 points [range, 45 to 100 points] as compared with 67 points [range, 35 to 99 points]), the difference only approached significance (p = 0.08). In addition, there was a noticeable deterioration in the mean Harris hip score for the total population of patients at annual intervals after the acetabular revision; the decrease in this score between the first and fourth years and between the first and fifth years was significant (p = 0.04).

Three hips (8 per cent; three patients) had a dislocation in the postoperative period. Two of these hips did not need an additional operation, and one needed a revision later because of loosening and a periprosthetic fracture. Five hips (14 per cent; five patients) had evidence of a trochanteric non-union after a trochanteric osteotomy was performed. One of these hips was symptomatic and needed a second operation for reattachment of the trochanter, and the other four were asymptomatic.

According to the criteria proposed by Harris et al.¹⁷, two femoral components (5 per cent), which had been in place for eighty-eight and 252 months at the time of the revision of the acetabular component, were definitely loose at forty-four and 132 months after the revision. These femoral components had not yet needed to be revised at the time of writing. No femoral component had evidence of probable loosening, and four (11 per cent) had evidence of possible loosening.

The position of the femoral component in the coronal plane averaged 0.6 degree of varus (range, 3 degrees of valgus to 9 degrees of varus). Although the femoral stems that subsequently failed had a greater tendency for varus placement (mean, 1.3 degrees of varus angulation) compared with the femoral stems that survived (mean, 0.4 degree of varus angulation), the difference was not significant (p = 0.14).

Progressive osteolysis of the proximal aspect of the femur was noted in five hips (14 per cent). The osteolysis involved zone 1 or 7, or both, of Gruen et al.¹⁴ in four hips and zones 1, 2, 6, and 7 in one hip. Non-progressive osteolysis limited to zone 1 or 7, or both, was evident in two additional hips (5 per cent). Three of the five hips that had progressive osteolysis subsequently were revised because of loosening; in the other two, the implant was not radiographically loose or symptomatic.

Only two hips (5 per cent) had evidence of an osteolytic lesion, which did not appear to be progressive, in the superolateral portion of the acetabulum.

At a mean of seventy-one months after the revision, the mean rate of linear wear was 0.13 millimeter per year (range, 0.0 to 0.43 millimeter per year) for the thirty-one acetabular components for which it was calculated.

With failure defined as revision or definite loosening of the femoral component, survivorship analysis demonstrated that the probability of survival of the femoral component at forty-eight months after the revision of the acetabular component was 88 per cent (95 per cent confidence interval, 82 to 94 per cent) (Fig. 1). At eighty-eight months, the predicted survival was only 78 per cent, but the standard error was large (95 per cent confidence interval, 67 to 89 per cent) because of the small size of the sample at this interval.

No significant relationship was found between the patient's age (p = 0.39) or weight (p = 0.23), the duration that the femoral component had been in situ (p = 0.48), or the preoperative Harris hip score (p = 0.16) and failure of the femoral component.

Discussion

Introduction | Materials and Methods | Results | Discussion | References

Ultimately, the decision to retain a well fixed femoral component that originally was implanted with a so-called first-generation cementing technique should be based on the prognosis for survival of the implant. It is possible, however, that the probability of survival of a retained femoral component after revision of the acetabular component is different from that of a primary femoral component not associated with such a revision. Moreover, because the retained implants are non-modular, the potential for complications, such as perioperative dislocation and accelerated wear of the articulating surfaces, may be increased. Therefore, by comparing our results with those for historical controls, we attempted to determine whether the survival of a femoral component implanted with a first-generation cementing technique was altered by revision of the acetabular component. We also attempted to determine whether the rate of polyethylene wear was notably altered by revision of one side of the joint and retention of a cemented non-modular femoral component that had been in service for approximately a decade.

Excluding the stems that had been revised or that were definitely loose, all but one femoral component in the current series had been in place for at least ten years (mean, 13.7 years; range, 101 to 252 months) at the time of the latest follow-up evaluation. To our knowledge, the best results, at similar durations of follow-up, with regard to femoral components placed with a so-called first-generation cementing technique have been obtained with the Charnley prosthesis, with rates of mechanical failure ranging from 1.7 per cent (three of 173 hips) to 30.4 per cent (sixty-three of 207 hips)^{3,5-7,11,15,19,21,22,26,36,38}. The ten to fifteen-year results of use of the Charnley-Müller and Müller prostheses have been less favorable, with rates of mechanical loosening as high as 40 per cent (forty of 100 hips) to 58.0 per cent (297 of 512 hips)^10,28,29,37. Although sixteen (43 per cent) of the thirty-seven femoral components in the current series were either of the Charnley-Müller or of the Müller design, only one of the eight femoral components that failed mechanically was one of these types. Thus, the rate of mechanical failure of the femoral component in this study (22 per cent; eight of thirty-seven) appears to be in the range of expected failure and to have not been appreciably altered by revision of the acetabular component.

We were unable to find an association between failure of the femoral component and any clinical factor, such as the patient's age, weight, or gender; the preoperative Harris hip score; or the length of time that the femoral component had been in place before the revision of the acetabular component.

Radiographically, the alignment in the coronal plane of the femoral components that did not fail differed from that of those that failed, with the latter group having a greater tendency for varus alignment. This difference was not significant, probably because of the small size of the sample. However, other authors have noted a strong relationship between varus placement of the femoral component and premature failure of the implant. For example, Callaghan et al. found that 50 per cent of 146 failed prostheses that had been inserted with cement were associated with a varus position of the stem⁴. Similarly, Pellicci et al. found that fifty-six of sixty-seven cemented femoral components that were revised for loosening had been placed in a varus position^29,30. Russotti et al., in a study of the results at least five years after 251 consecutive total hip arthroplasties performed with cement, also demonstrated a significant (p = 0.036) relationship between varus placement of the femoral component and new or progressive radiolucent lines around that component³³. Therefore, serious consideration should probably be given to revision of a well fixed cemented femoral component that is in varus alignment and has been in place for more than ten years at the time of revision of the acetabular component.

There were few complications in the current series, and the risk of complications did not appear to be increased by the retention of a non-modular femoral component. The rate of dislocation of 8 per cent (three of thirty-seven hips) falls in the range of 4.8 per cent (158 of 3259 hips) to 19 per cent (sixteen of eighty-five hips) reported by other authors for hips that have been revised or that have been operated on previously^24,39. The relatively low rate of dislocation after revision of the acetabular component without cement may be a reflection of the ability of the hemispherical acetabular component to restore the center of rotation of the hip to a more anatomical location, thereby improving soft-tissue tension around the hip. The rate of trochanteric non-union of 14 per cent (five of thirty-seven hips) is higher than the rate of 5 per cent (thirty-five of 728 hips) reported by Amstutz and Muki² for primary arthroplasty and the rate of 9 per cent (ten of 110 hips) reported by Pellicci et al.²⁹ for revision arthroplasty. Undoubtedly, poor bone quality and reduced bone-to-bone contact secondary to interposed cement make trochanteric fixation more difficult in the revision setting.

The clinical and radiographic results with regard to the acetabular components used for revision in the current series were reported previously by Padgett et al.²⁷ and, more recently, by Silverton et al.³⁵. Retention of a non-modular femoral component does generate concern regarding the condition of the implant-bearing surface and eventual polyethylene wear. However, the rate of linear wear of 0.13 millimeter per year in the current study was not significantly different (p = 0.74) from the measured rate of 0.12 millimeter per year, after a similar duration of follow-up (mean, sixty-four months; range, forty-five to eighty-seven months), for the forty-nine hips that had had simultaneous revision of the femoral and acetabular components without cement at our institution between 1985 and 1989³¹.

Some surgeons may consider a rate of mechanical failure of 22 per cent (eight of thirty-seven femoral components) five years after revision of the acetabular component to be unacceptably high. However, the ultimate survival of the implant and the increased morbidity after revision of the femoral component must be considered. Over a similar time-period (1985 through 1989) at our institution, forty-nine femoral components that had been inserted without cement were revised with use of a curved long-stem proximally porous-coated component because of aseptic loosening; with use of revision or progressive subsidence as the end point, there was only a 37 per cent chance of survival of the component at seventy-two months³¹. Undoubtedly, revision of a well fixed cemented femoral component involves even greater technical demands, operating time, and morbidity than revision of a similar implant that is loose^1,4,29,30. Thus, although more effective femoral components may be available for revisions, we believe that a well fixed femoral component that has been inserted with a so-called first-generation cementing technique should be retained at the time of revision of the acetabular component in most patients.

References

Introduction | Materials and Methods | Results | Discussion | References

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