JBJS | Effect of the Elevated-Rim Acetabular Liner on Loosening after Total Hip Arthroplasty*

The Journal of Bone & Joint Surgery, Volume 79, Issue 9

Articles | September 01, 1997

Effect of the Elevated-Rim Acetabular Liner on Loosening after Total Hip Arthroplasty*

T. K. COBB, M.D.†; B. F. MORREY, M.D.†; D. M. ILSTRUP, M.S.†, ROCHESTER, MINNESOTA

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Investigation performed at the Mayo Clinic and Mayo Foundation, Rochester

The Journal of Bone & Joint Surgery. 1997; 79:1361-4

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Abstract

Elevated-rim acetabular liners recently were shown to be associated with improved stability of total hip prostheses in a large clinical series. However, the effect of this design on loosening remains unknown. To address this question, we reviewed the results of 5167 primary and revision total hip arthroplasties that had been performed at our institution from September 1, 1985, through December 31, 1991; 2469 of the acetabular components had an elevated-rim liner (10 degrees of elevation), and 2698 had a standard liner. Five-year follow-up data were available for 1237 hips (174 that had an elevated-rim acetabular liner and 1063 that had a standard acetabular liner). The cumulative probability of revision because of loosening of the implant was estimated as a function of time since the operation with use of the Kaplan-Meier survivorship method. The five-year probability of survival of the acetabular component was 98.8 per cent (95 per cent confidence interval, 97.9 to 99.6 per cent) for the prostheses that had an elevated-rim liner and 98.3 per cent (95 per cent confidence interval, 97.7 to 99.0 per cent) for those that had a standard liner (p = 0.87). The effect of the elevated-rim acetabular liner on the probability of revision because of loosening of the acetabular or the femoral component was analyzed for several subgroups: components inserted with cement, components inserted without cement, primary total hip arthroplasties, revision total hip arthroplasties, male patients, and female patients. With the numbers available, no significant differences were found in the probability of survival of the acetabular or the femoral component in any of the subgroups. Theoretical considerations suggest that the geometric design of the elevated-rim acetabular liner may have biomechanical characteristics that predispose the implant to early loosening. However, our initial review of the results of total hip arthroplasties after a mean follow-up period of five years (range, 0.25 to ten years) failed to demonstrate any difference in the cumulative probability of revision because of loosening of the implant. Continued surveillance is warranted and ongoing.

Figures in this Article

Introduction

Introduction | Materials and Methods | Results | Discussion | References

Elevated-rim acetabular liners recently were shown to improve stability of total hip prostheses in a large clinical series^3,9. However, the potential adverse effects of the liner on the generation of wear debris and loosening remain unknown. Some investigators have suggested that the geometric design of the elevated-rim acetabular liner may have biomechanical characteristics that predispose the implant to early loosening¹¹. An extended acetabular wall has even been implicated as the cause of loosening of the femoral component¹. Yet, as far as we know, no clinical studies have been performed to compare the probability of loosening associated with elevated-rim acetabular liners with that associated with standard acetabular liners. To address this question, we retrospectively reviewed data regarding 5167 primary and revision total hip arthroplasties performed with either an elevated-rim acetabular component or a standard acetabular component from 1985 through 1991. Our purpose was to compare the prevalences of revision because of loosening of the implant.

*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

†Departments of Orthopedic Surgery (T. K. C. and B. F. M.) and Biostatistics (D. M. I.), Mayo Clinic and Mayo Foundation, 200 First Street S.W., Rochester, Minnesota 55905.

*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

†Departments of Orthopedic Surgery (T. K. C. and B. F. M.) and Biostatistics (D. M. I.), Mayo Clinic and Mayo Foundation, 200 First Street S.W., Rochester, Minnesota 55905.

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FIG1-A:: Figs. 1-A and 1-B: Graphs showing the cumulative Kaplan-Meier probability of survival of the acetabular (Fig. 1-A) and the femoral component (Fig. 1-B) after arthroplasties performed with an elevated-rim acetabular liner (solid line) and those performed with a standard (neutral) liner (dotted line). No significant differences were detected for either the acetabular or the femoral component at five years. THA = total hip arthroplasty.

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FIG1-B:: Figs. 1-A and 1-B: Graphs showing the cumulative Kaplan-Meier probability of survival of the acetabular (Fig. 1-A) and the femoral component (Fig. 1-B) after arthroplasties performed with an elevated-rim acetabular liner (solid line) and those performed with a standard (neutral) liner (dotted line). No significant differences were detected for either the acetabular or the femoral component at five years. THA = total hip arthroplasty.

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TABLE I SURVIVAL OF THE COMPONENTS AFTER FIVE YEARS ACCORDING TO THE DESIGN OF THE ACETABULAR CUP*

*The probability of survival of the components was calculated with use of Kaplan-Meier analysis. The values are given as the percentage, with the 95 per cent confidence interval in parentheses.

	Rim of Acetabular Cup
	Elevated	Standard	P Value
Acetabular component
All hips	98.8 (97.9 to 99.6)	98.3 (97.7 to 99.0)	0.87
Fixat. with cement	98.5 (97.1 to 100)	98.4 (97.6 to 99.2)	0.52
Fixat. without cement	98.9 (97.8 to 100)	98.2 (97.3 to 99.2)	0.66
Primary arthroplasties	99.3 (98.6 to 100)	99.0 (98.5 to 99.5)	0.98
Revision arthroplasties	95.7 (90.7 to 100)	95.7 (93.5 to 97.9)	0.64
Male patients	99.4 (98.4 to 100)	98.6 (97.8 to 99.4)	0.11
Female patients	98.2 (96.8 to 99.6)	98.1 (97.2 to 99.0)	0.15
Femoral component
All hips	91.9 (89.9 to 93.9)	92.8 (91.7 to 94.0)	0.23
Primary arthroplasties
Fixat. with cement	95.1 (92.5 to 97.7)	94.9 (93.6 to 96.2)	0.98
Fixat. without cement	94.1 (91.6 to 96.6)	95.0 (93.1 to 96.9)	0.28
Revision arthroplasties
Fixat. with cement	91.9 (85.2 to 99.2)	85.3 (80.3 to 90.6)	0.52
Fixat. without cement	76.1 (66.2 to 87.5)	84.2 (79.5 to 89.1)	0.21

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TABLE I SURVIVAL OF THE COMPONENTS AFTER FIVE YEARS ACCORDING TO THE DESIGN OF THE ACETABULAR CUP*

*The probability of survival of the components was calculated with use of Kaplan-Meier analysis. The values are given as the percentage, with the 95 per cent confidence interval in parentheses.

	Rim of Acetabular Cup
	Elevated	Standard	P Value
Acetabular component
All hips	98.8 (97.9 to 99.6)	98.3 (97.7 to 99.0)	0.87
Fixat. with cement	98.5 (97.1 to 100)	98.4 (97.6 to 99.2)	0.52
Fixat. without cement	98.9 (97.8 to 100)	98.2 (97.3 to 99.2)	0.66
Primary arthroplasties	99.3 (98.6 to 100)	99.0 (98.5 to 99.5)	0.98
Revision arthroplasties	95.7 (90.7 to 100)	95.7 (93.5 to 97.9)	0.64
Male patients	99.4 (98.4 to 100)	98.6 (97.8 to 99.4)	0.11
Female patients	98.2 (96.8 to 99.6)	98.1 (97.2 to 99.0)	0.15
Femoral component
All hips	91.9 (89.9 to 93.9)	92.8 (91.7 to 94.0)	0.23
Primary arthroplasties
Fixat. with cement	95.1 (92.5 to 97.7)	94.9 (93.6 to 96.2)	0.98
Fixat. without cement	94.1 (91.6 to 96.6)	95.0 (93.1 to 96.9)	0.28
Revision arthroplasties
Fixat. with cement	91.9 (85.2 to 99.2)	85.3 (80.3 to 90.6)	0.52
Fixat. without cement	76.1 (66.2 to 87.5)	84.2 (79.5 to 89.1)	0.21

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

Detailed clinical and functional data regarding all total hip arthroplasties performed at our institution from September 1, 1985, through December 31, 1991, were assessed. Of the 7105 hip procedures, those that involved use of a bipolar prosthesis, fixed-head endoprosthesis, custom-designed prosthesis, or acetabular liner with the rim elevated 15 or 20 degrees, as well as those performed for reconstruction after resection of a tumor, were excluded from the review. With use of these criteria, 5167 arthroplasties were selected for the study: 2469 that had been performed with use of an elevated-rim acetabular component and 2698 that had been done with use of a standard (neutral) acetabular component. The study included arthroplasties performed with cementing of the femoral and acetabular components, those performed without cement, primary procedures, and revision procedures. The selection of the type of liner was not standardized; it was made at the discretion of the surgeon. Because it was difficult to interpret the radiolucent lines around the acetabular component, revision due to loosening of either the acetabular or the femoral component was used as the discrete failure end point. This approach has been used previously, and a detailed analysis of the rationale for this decision has been described⁹. The group was analyzed according to type of operation (primary or revision), gender, and type of fixation (with or without cement). The risk of revision because of loosening was assessed on the basis of the design of the acetabular cup. Follow-up data were obtained with a physical examination (2739 arthroplasties; 53 per cent), with use of a questionnaire (1808 arthroplasties; 35 per cent), or with a telephone interview (620 arthroplasties; 12 per cent). As the end point was defined as the replacement of the component, a valid conclusion can be drawn from any of these methods of analysis.

Because the degree of elevation of the rim of the acetabular liner varies according to the design and the manufacturer, only implants with 10 degrees of elevation of the rim were assessed. All liners typically were placed with the elevated portion of the rim in a superior (twelve to one o'clock), posterosuperior (two o'clock [left hip] or ten o'clock [right hip]), or posterior (three o'clock [left hip] or nine o'clock [right hip]) position.

Statistical Methods

The cumulative probability of revision because of loosening of a component was estimated as a function of time since the operation with use of the Kaplan-Meier survivorship method. Comparisons of the survivorship curves were made with the log-rank test¹³. In order to adjust for known selection bias, separate comparisons of the survival rates of the implants with the elevated-rim acetabular liner and those with the standard acetabular liner were made according to variables, which included insertion of the implant with cement, insertion of the implant without cement, the gender of the patient, primary total hip arthroplasty, and revision total hip arthroplasty. All significance tests were two-sided, and p values of less than 0.05 were considered to be significant. Ninety-five per cent confidence intervals were calculated for survivorship estimates. With the size of the sample used in this study, there was at least an 80 per cent chance of detecting a difference of 3 percentage points in the five-year rate of survival (for example, 98 per cent compared with 95 per cent).

Surveillance

Over-all, the mean duration of surveillance for all of the patients in our study was five years (range, 0.25 to ten years). The patients who were alive and had not had a revision operation (had the implant in situ) were followed for a mean of 3.1 years (median, 2.3 years; range, 0.25 to 7.6 years). Five-year follow-up data were available for 1237 (83 per cent) of the 1495 hips (174 [81 per cent] of the 215 hips that had an elevated-rim acetabular liner and 1063 [83 per cent] of the 1280 hips that had a standard acetabular liner) that were potentially eligible for at least five years of follow-up.

Results

Introduction | Materials and Methods | Results | Discussion | References

Cumulative Survival of the Acetabular and Femoral Components

One hundred and seventy-nine (7 per cent) of the 2698 hips with a standard acetabular liner and 108 (4 per cent) of the 2469 hips with an elevated-rim acetabular liner had a revision because of loosening of either the acetabular or the femoral component. The cumulative Kaplan-Meier probability of survival without revision because of loosening of either component at five years was 92.8 per cent (95 per cent confidence interval, 91.6 to 93.9 per cent) for the implants with a standard acetabular liner and 91.8 per cent (95 per cent confidence interval, 89.9 to 93.8 per cent) for those with an elevated-rim acetabular liner. No significant difference was found between the groups (p = 0.22).

Survival of the Acetabular Components

The five-year probability of survival of the acetabular component was 98.8 per cent (95 per cent confidence interval, 97.9 to 99.6 per cent) in the group that had an elevated-rim liner and 98.3 per cent (95 per cent confidence interval, 97.7 to 99.0 per cent) in the group that had a standard liner (p = 0.87) (Fig. 1-A). With the numbers available, no significant differences were detected between the rates of survival of the two types of acetabular component in any of the subgroups (components fixed with cement [p = 0.52], those fixed without cement [p = 0.66], primary arthroplasties [p = 0.98], revision arthroplasties [p = 0.64], male patients [p = 0.11], and female patients [p = 0.15]) (Table I).

Survival of the Femoral Components

The five-year probability of survival of the femoral component was 91.9 per cent (95 per cent confidence interval, 89.9 to 93.9 per cent) in the group that had an elevated-rim liner and 92.8 per cent (95 per cent confidence interval, 91.7 to 94.0 per cent) in the group that had a standard liner (p = 0.23) (Fig. 1-B). Similarly, with the numbers available, no significant difference in the rates of survival could be found between the femoral components articulating with an elevated-rim acetabular component and those articulating with a standard acetabular component in any subgroup (primary components fixed with cement [p = 0.98] and without cement [p = 0.28], and revision components fixed with cement [p = 0.52] and without cement [p = 0.21]) (Table I).

Discussion

Introduction | Materials and Methods | Results | Discussion | References

Acetabular augmentation was introduced by Charnley^2,4, who, in an attempt to prevent posterior dislocation of the femoral head, extended the posterior aspect of a high-density polyethylene acetabular cup designed to be inserted with cement. It is of interest that no studies to our knowledge have assessed the impact of this design modification.

The modularity of the separate cup and the ultra-high molecular weight polyethylene liner introduced into systems designed to be inserted without cement was ideal for further application of the design concept because the extended wall of the liner could be precisely positioned to the desired location after the cup had been secured in place. Until recently, however, studies on the effect of this design on the stability of the component have been limited to a few case reports^5,8,12. In a more detailed analysis, we demonstrated an association between elevated-rim acetabular liners and improved stability³. However, the growing concern about the long-term effects of this design on wear and loosening have not been studied in the clinical setting as far as we know. Such investigations of the potential complications of this type of cup are of particular interest because of the number of total hip arthroplasties performed and the time-dependent nature of the variables. Because these potential problems are of considerable concern to us and to the orthopaedic community, we performed the present study to assess our experience to date with the elevated-rim acetabular liner.

Furthermore, speculation continues about the long-term effect of the more constrained articular design of the elevated-rim acetabular component. Three potential problems are wear debris from the ultra-high molecular weight polyethylene, loosening from the increased rotatory moment introduced by force being transmitted at the point of contact of the augmented rim, and a combination of debris and increased torque that possibly could potentiate the adverse effects and lead to loosening of the cup.

Wear of the elevated portion of the rim has been reported in isolated instances^2,10. Murray found severe erosion of four of ten elevated-rim components obtained at the time of revision, and similar wear problems also have been observed by the senior one of us (B. F. M.). An association between wear of the polyethylene acetabular liner and osteolysis after total hip arthroplasty recently has been demonstrated⁷. Furthermore, a recent case report has implicated osteolysis induced by particles of polyethylene wear debris from an elevated-rim acetabular liner as a cause of loosening of the femoral stem¹. A discrete semilunar trough, eight millimeters deep and ten millimeters long, had been worn into the elevated portion of the acetabular liner in the patient in that report. Histological analysis of the membrane and the pseudocapsule retrieved at revision demonstrated a foreign-body giant-cell reaction with intracellular polyethylene. Although this is a single case report, it raises the concern of an increased risk of osteolysis and capsular distention from wear debris.

Despite the case reports and the theoretical concerns, our initial review of the results of a large sample of total hip arthroplasties after a modest duration of follow-up failed to substantiate an increased rate of loosening. Our study included the full complement of procedures performed at our institution, even those followed by less than two years of surveillance. The Kaplan-Meier algorithm requires input of all observations, regardless of duration in situ, for an accurate calculation of the statistical probability of survival. Hence, all procedures are considered in the calculation, regardless of the actual or potential duration of surveillance. Elevated-rim acetabular liners do not appear to predispose a patient to catastrophic loosening of the acetabular or femoral component within the first five years after total hip arthroplasty. It should be noted, however, that when revision because of loosening is used as the end point radiographic evidence of lucency or impending failure before revision is not taken into account. Additional surveillance is necessary to address more fully the long-term risk of loosening.

Nevertheless, we are concerned about and continue to monitor the implications of this design with regard to the survival of the implant. The senior one of us (B. F. M.) continues to use the elevated-rim acetabular liner primarily in revision operations performed because of loosening. A standard liner is used in virtually all primary procedures.

References

Introduction | Materials and Methods | Results | Discussion | References

Bosco, J. A., and Benjamin, J. B.: Loosening of a femoral stem associated with the use of an extended-lip acetabular cup liner. A case report. J. Arthroplasty,8: 91-93, 1993.891 1993 [PubMed]

Charnley, J.: Low Friction Arthroplasty of the Hip. Theory and Practice. New York, Springer, 1979.

Cobb, T. K.; Morrey, B. F.; and Ilstrup, D. M.: The elevated-rim acetabular liner in total hip arthroplasty: relationship to postoperative dislocation. J. Bone and Joint Surg.,78-A: 80-86, Jan. 1996.78-A80 1996

Eftekhar, N. S.: Dislocation and instability complicating low friction arthroplasty of the hip joint. Clin. Orthop.,121: 120-125, 1976.121120 1976 [PubMed]

Graham, G. P.; Jenkins, A. I. R.; and Mintowt-Czyz, W.: Recurrent dislocation following hip replacement: brief report. J. Bone and Joint Surg.,70-B(4): 675, 1988.70-B(4)675 1988

Kaplan, E. L., and Meier, P.: Nonparametric estimation from incomplete observations. J. Am. Statist. Assn.,53: 457-481, 1958.53457 1958

Livermore, J.; Ilstrup, D.; and Morrey, B.: Effect of femoral head size on wear of the polyethylene acetabular component. J. Bone and Joint Surg.,72-A: 518-528, April 1990.72-A518 1990

Mogensen, B.; Arnason, H.; and Jonsson, G. T.: Socket wall addition for dislocating total hip. Report of two cases. Acta Orthop. Scandinavica,57: 373-374, 1986.57373 1986

Morrey, B. F., and Ilstrup, D.: Size of the femoral head and acetabular revision in total hip replacement arthroplasty. J. Bone and Joint Surg.,71-A: 50-55, Jan. 1989.71-A50 1989

Murray, D. W.: Impingement and loosening of the long posterior wall acetabular implant. J. Bone and Joint Surg.,74-B(3): 377-379, 1992.74-B(3)377 1992

Nicholas, R. M.; Orr, J. F.; Mollan, R. A. B.; Calderwood, J. W.; Nixon, J. R.; and Watson, P.: Dislocation of total hip replacements. A comparative study of standard, long posterior wall and augmented acetabular components. J. Bone and Joint Surg.,72-B(3): 418-422, 1990.72-B(3)418 1990

Olerud, S., and Karlström, G.: Recurrent dislocation after total hip replacement. Treatment by fixing an additional sector to the acetabular component. J. Bone and Joint Surg.,67-B(3): 402-405, 1985.67-B(3)402 1985

Peto, R., and Peto, J.: Asymptomatically efficient rank invariant test procedures. J. Roy. Statist. Soc., Series A,135: 185-206, 1972.135185 1972

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TABLE I SURVIVAL OF THE COMPONENTS AFTER FIVE YEARS ACCORDING TO THE DESIGN OF THE ACETABULAR CUP*

*The probability of survival of the components was calculated with use of Kaplan-Meier analysis. The values are given as the percentage, with the 95 per cent confidence interval in parentheses.

	Rim of Acetabular Cup
	Elevated	Standard	P Value
Acetabular component
All hips	98.8 (97.9 to 99.6)	98.3 (97.7 to 99.0)	0.87
Fixat. with cement	98.5 (97.1 to 100)	98.4 (97.6 to 99.2)	0.52
Fixat. without cement	98.9 (97.8 to 100)	98.2 (97.3 to 99.2)	0.66
Primary arthroplasties	99.3 (98.6 to 100)	99.0 (98.5 to 99.5)	0.98
Revision arthroplasties	95.7 (90.7 to 100)	95.7 (93.5 to 97.9)	0.64
Male patients	99.4 (98.4 to 100)	98.6 (97.8 to 99.4)	0.11
Female patients	98.2 (96.8 to 99.6)	98.1 (97.2 to 99.0)	0.15
Femoral component
All hips	91.9 (89.9 to 93.9)	92.8 (91.7 to 94.0)	0.23
Primary arthroplasties
Fixat. with cement	95.1 (92.5 to 97.7)	94.9 (93.6 to 96.2)	0.98
Fixat. without cement	94.1 (91.6 to 96.6)	95.0 (93.1 to 96.9)	0.28
Revision arthroplasties
Fixat. with cement	91.9 (85.2 to 99.2)	85.3 (80.3 to 90.6)	0.52
Fixat. without cement	76.1 (66.2 to 87.5)	84.2 (79.5 to 89.1)	0.21

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TABLE I SURVIVAL OF THE COMPONENTS AFTER FIVE YEARS ACCORDING TO THE DESIGN OF THE ACETABULAR CUP*

*The probability of survival of the components was calculated with use of Kaplan-Meier analysis. The values are given as the percentage, with the 95 per cent confidence interval in parentheses.

	Rim of Acetabular Cup
	Elevated	Standard	P Value
Acetabular component
All hips	98.8 (97.9 to 99.6)	98.3 (97.7 to 99.0)	0.87
Fixat. with cement	98.5 (97.1 to 100)	98.4 (97.6 to 99.2)	0.52
Fixat. without cement	98.9 (97.8 to 100)	98.2 (97.3 to 99.2)	0.66
Primary arthroplasties	99.3 (98.6 to 100)	99.0 (98.5 to 99.5)	0.98
Revision arthroplasties	95.7 (90.7 to 100)	95.7 (93.5 to 97.9)	0.64
Male patients	99.4 (98.4 to 100)	98.6 (97.8 to 99.4)	0.11
Female patients	98.2 (96.8 to 99.6)	98.1 (97.2 to 99.0)	0.15
Femoral component
All hips	91.9 (89.9 to 93.9)	92.8 (91.7 to 94.0)	0.23
Primary arthroplasties
Fixat. with cement	95.1 (92.5 to 97.7)	94.9 (93.6 to 96.2)	0.98
Fixat. without cement	94.1 (91.6 to 96.6)	95.0 (93.1 to 96.9)	0.28
Revision arthroplasties
Fixat. with cement	91.9 (85.2 to 99.2)	85.3 (80.3 to 90.6)	0.52
Fixat. without cement	76.1 (66.2 to 87.5)	84.2 (79.5 to 89.1)	0.21