The Journal of Bone & Joint Surgery

The Journal of Bone & Joint Surgery, Volume 88, Issue 9

Scientific Articles | September 01, 2006

Cost-Effectiveness Analysis of Unicompartmental Knee Arthroplasty as an Alternative to Total Knee Arthroplasty for Unicompartmental Osteoarthritis

Nelson F. Soohoo, MD¹; Husham Sharifi, BS, MBA¹; Gerald Kominski, PhD¹; Jay R. Lieberman, MD¹

¹ Department of Orthopaedic Surgery, University of California at Los Angeles, 10945 Le Conte Avenue, PVUB #3355, Los Angeles, CA 90095. E-mail address for N.F. SooHoo: nsoohoo@mednet.ucla.edu

View Disclosures and Other Information

The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Investigation performed at the Department of Orthopaedic Surgery, University of California at Los Angeles, Los Angeles, California

The Journal of Bone and Joint Surgery, Incorporated

J Bone Joint Surg Am, 2006 Sep 01;88(9):1975-1982. doi: 10.2106/JBJS.E.00597

5 Recommendations (Recommend) | 3 Comments | Saved by 3 Users Save Case

Article

Comments (0)

text A A A

Abstract

Background: The purpose of this study was to compare the cost-effectiveness of unicompartmental knee arthroplasty as an alternative to total knee arthroplasty in patients with degenerative arthritis limited to either the medial or lateral compartment.

Methods: A decision model was created for the treatment of end-stage unicompartmental knee arthritis. A literature review was used to identify possible outcomes and their probabilities following treatment with either unicompartmental or total knee arthroplasty. Each outcome was weighted for quality of life with use of a utility factor, and effectiveness was expressed in units of quality-adjusted life years. Gross costs were estimated from Medicare reimbursement data for the relevant Current Procedural Terminology and Diagnosis-Related Group codes.

Results: Sensitivity analysis demonstrated that the cost-effectiveness of unicompartmental knee arthroplasty is dependent on the assumption that its durability and functional outcomes approach those of total knee arthroplasty. Specifically, it is necessary for the survival of unicompartmental implants to be within three to four years of the assumed survival of total knee implants for unicompartmental arthroplasty to remain a cost-effective alternative. Under these assumptions, the use of unicompartmental arthroplasty is a cost-effective choice as it results in incremental gains in effectiveness at a cost of less than $50,000 (in 1998 United States dollars) per quality-adjusted life year gained.

Conclusions: This study supports unicompartmental knee arthroplasty as a cost-effective alternative for the treatment of unicompartmental arthritis when the durability and function of a unicompartmental replacement are assumed to be similar to those of a primary total knee replacement. This suggests that, with appropriate patient selection, the currently available literature supports unicompartmental arthroplasty as a cost-effective alternative to total knee arthroplasty.

Level of Evidence: Economic and decision analysis, Level II. See Instructions to Authors for a complete description of levels of evidence.

Figures in this Article

In patients with end-stage unicompartmental disease who have failed other treatments, total knee arthroplasty has been shown to be a highly effective treatment that results in substantial improvement in quality of life¹. Despite the excellent clinical outcomes seen with total knee arthroplasty in these patients, there are long-term concerns regarding implant wear and durability. Unicompartmental knee arthroplasty has been advocated as a technological advance in the subset of patients undergoing surgery for arthritis that involves only one compartment of the knee^2-10. The potential advantages of unicompartmental knee arthroplasty include a less invasive surgical technique, more rapid rehabilitation, and more normal knee kinematics¹.

The purpose of this study was to examine the cost-effectiveness of unicompartmental knee arthroplasty in comparison with total knee arthroplasty for the treatment of isolated end-stage unicompartmental knee arthritis. The potential benefits of unicompartmental knee arthroplasty have led to growing interest in and expanded use of unicompartmental knee arthroplasty as an alternative to total knee arthroplasty in the treatment of unicompartmental arthritis. The available literature on unicompartmental knee arthroplasty consists mainly of case series that have described the results of specific designs¹. While the results of several large series have been promising, there are few well-controlled trials that have directly compared total knee arthroplasty with unicompartmental knee arthroplasty^2-10. The present study extrapolates published data on the survival and function of unicompartmental prostheses to identify thresholds that would justify the use of unicompartmental knee arthroplasty.

View Large | Download Slide(.ppt)
Add to My JBJS

Fig. 1: Simplified schematic of the decision model for the treatment of unicompartmental arthritis of the knee. TKA = total knee arthroplasty, and UKA = unicompartmental knee arthroplasty.

Materials and Methods

Materials and Methods | Results | Discussion | Appendix | References

General Framing and Design

This cost-effectiveness analysis follows the methodological guidelines of the Panel on Cost-Effectiveness in Health and Medicine convened by the United States Public Health Service in 1993¹¹. Consistent with these reference case guidelines, the present analysis compares the cost-effectiveness of unicompartmental arthroplasty with the commonly accepted treatment alternative of total knee arthroplasty for unicompartmental arthritis. This analysis assumes a target patient population seeking treatment for unicompartmental arthritis at the age of sixty-five years. The time horizon of this analysis encompasses the remaining eighteen years of life expectancy for this target population¹². The cost-effectiveness ratios for unicompartmental and total knee arthroplasty were analyzed from the societal perspective. The boundary of the analysis is limited to the costs and health effects directly impacting the target population. Estimates of costs, effectiveness, and the probability of various outcomes were obtained from a literature review.

Literature Review

A literature review was used to construct the event pathways following initial treatment with unicompartmental knee arthroplasty and total knee arthroplasty. We identified 345 articles, published from 1975 through 2004, using the following keywords: unicompartmental, unicondylar, knee arthroplasty, results, outcomes, cost, and effectiveness. We included articles published in the years 1994 through 2004 in order to best reflect the results from the current clinical use of unicompartmental knee arthroplasty. We excluded studies involving fewer than fifty subjects. Additional criteria used to select articles included the selection of patients with an intact anterior cruciate ligament and documented unicompartmental disease and the exclusion of patients who had a prior patellectomy or tibial osteotomy. A total of nine studies were identified and selected for abstraction with use of these criteria^2-10. The abstracted data, including the study design, number of subjects, results, and complications reported in each study, are provided in the Appendix.

Decision Model

Decision-tree software (TreeAge Pro; TreeAge Software, Williamstown, Massachusetts) was used to create a model for the treatment of unicompartmental arthritis^13-19. A simplified schematic of the decision tree is shown in Figure 1, and the full decision model is presented in the Appendix. The model begins with the decision for either unicompartmental or total knee arthroplasty. A literature review was used to identify possible outcomes and their probability following each of these treatment alternatives.

The event pathways following unicompartmental knee arthroplasty and total knee arthroplasty were constructed following the literature review. A wide range of results has been reported on the effectiveness of unicompartmental knee arthroplasty (see Appendix)^1-10. The reference case assumes a period of twelve years for the durability of a unicompartmental arthroplasty. This assumption is consistent with results of unicompartmental knee arthroplasty in the nine studies selected for data abstraction^2-10. Sensitivity analysis was used to examine the effects on the cost-effectiveness of unicompartmental knee arthroplasty of both shorter and longer assumptions for its durability. Total knee replacement was assumed in the reference case to have a survival of fifteen years. This value is longer than the survival assumed for unicompartmental knee replacement and reflects the fact that long-term outcomes have been more thoroughly documented for total knee replacement²⁰.

Subsequent events following unicompartmental knee arthroplasty and total knee arthroplasty were modeled to include the potential need for revision total knee arthroplasty as well as complications over the lifetime of the target population. Complications included infection and death²⁰. The rates of these complications were selected to fall in the midrange of estimates reported in the literature. Most studies have described rates of infection leading to implant failure near the value of 1% used in the reference case of this study^20-22. The reference case of 0.5% for mortality is consistent with the low rates generally reported²².

Effectiveness

Utility factors were assigned to all health states in the model to adjust survival for quality of life. The reference case guidelines define utility along a continuum with a factor of 1.0 representing perfect health and a factor of 0.0 representing death¹¹. Specific utility values for each health state in this study were assigned following a literature review (Table I). Arthritis has consistently been shown to have a utility value near 0.7^23-26. Knee and hip arthroplasty have been shown to increase quality-of-life weightings close to normal values. On the basis of these studies, this analysis uses a utility value of 0.9 for successful unicvompartmental and total knee arthroplasty^23-26. Revision arthroplasty is given a lower utility value to reflect the diminished clinical results compared with primary arthroplasty. Previously published data were used to assign a utility value of 0.6 for resection arthroplasty and 0.5 to periods of surgery and postoperative recovery following complications²⁴. Sensitivity analysis was used to examine the effect of uncertainty about the utility values for unicompartmental knee arthroplasty and total knee arthroplasty on the cost-effectiveness results.

View Larger

TABLE I Utility Values for Health States Occurring in the Reference Case of the Decision Model

Health State	Utility Value
Primary total knee arthroplasty	0.9
Unicompartmental knee arthroplasty	0.9
Treatment of infection	0.5
Surgery and postoperative recovery	0.5
Death	0.0
Revision total knee arthroplasty	0.85
Resection knee arthroplasty	0.6

Add to My JBJS

TABLE I Utility Values for Health States Occurring in the Reference Case of the Decision Model

Health State	Utility Value
Primary total knee arthroplasty	0.9
Unicompartmental knee arthroplasty	0.9
Treatment of infection	0.5
Surgery and postoperative recovery	0.5
Death	0.0
Revision total knee arthroplasty	0.85
Resection knee arthroplasty	0.6

Costs

Gross-costing methodology was used to estimate the direct life-time treatment costs following both unicompartmental and total knee arthroplasty¹¹. The surgical interventions occurring in the decision model were assigned their appropriate ICD-9 (International Classification of Diseases—Ninth Revision), DRG (Diagnosis-Related Group), and CPT (Current Procedural Terminology) codes. Gross-cost estimates for acute care hospitalizations were determined from mean hospital costs for the DRG associated with each intervention. The mean hospital costs were based on data from the Centers for Medicare and Medicaid Services reported for 1998²⁷. These costs are derived by applying Medicare cost-to-charge ratios to the data from the Medicare Provider Analysis and Review File (MEDPAR) data source²⁷. The MEDPAR data source is released annually by Medicare and provides cost estimates for each DRG^27,28. The gross costs for physician services were determined from the mean Medicare reimbursement for the CPT code associated with each surgical intervention (Table II)²⁹.

View Larger

TABLE II Costs for DRG and CPT Codes in Decision Model with Use of 1998 Medicare Data*

	DRG			CPT
Procedure	Code	Cost	Code	Cost
Unicompartmental knee arthroplasty	209	$9183	27446	$1445
Primary total knee arthroplasty	209	$9183	27447	$1951
Revision total knee arthroplasty	209	$9183	27487	$2298
Resection arthroplasty	210	$8086	27488	$1348
Operative treatment of infection around knee prosthesis	210	$8086	27310	$797

Values are based on 1998 United States dollars. DRG = Diagnosis-Related Group, and CPT = Current Procedural Terminology.

Add to My JBJS

TABLE II Costs for DRG and CPT Codes in Decision Model with Use of 1998 Medicare Data*

	DRG			CPT
Procedure	Code	Cost	Code	Cost
Unicompartmental knee arthroplasty	209	$9183	27446	$1445
Primary total knee arthroplasty	209	$9183	27447	$1951
Revision total knee arthroplasty	209	$9183	27487	$2298
Resection arthroplasty	210	$8086	27488	$1348
Operative treatment of infection around knee prosthesis	210	$8086	27310	$797

Values are based on 1998 United States dollars. DRG = Diagnosis-Related Group, and CPT = Current Procedural Terminology.

Discounting

Cost-effectiveness analysis requires that all future costs and health consequences be discounted and stated in terms of their present-day values. Discounting is performed to correct for the fact that costs that are deferred to the future are preferable to immediate expenditures. Costs and health effects were discounted in the reference case at a constant rate of 3% annually^11,13.

Sensitivity Analysis

Sensitivity analysis was used to determine the impact of varying the assumed values for key variables on the conclusions generated by this cost-effectiveness analysis. Cost-effectiveness analysis combines information from several data sources in order to generate estimates of the probability of different outcomes and to assign values to their utility and costs. Uncertainty about the true values of these underlying parameters results in uncertainty about the cost-effectiveness ratios generated in the reference case. Sensitivity analysis was performed with use of different assumptions for the values of the underlying variables¹¹. Several key variables that were selected for sensitivity analysis included the durability of unicompartmental knee replacements relative to total knee replacements, the functional utility following unicompartmental arthroplasty, and the cost of unicompartmental knee arthroplasty.

Results

Materials and Methods | Results | Discussion | Appendix | References

Reference Case Results

Areference case was created with use of the assumption that unicompartmental arthroplasty results in a high level of function for twelve years. The assumption of twelve years of function is consistent with that in published clinical series, but there are limited data available that directly compare the durability of unicompartmental knee replacement and total knee replacement^1-10. Given the uncertainty of this assumption, the impact on the cost-effectiveness of unicompartmental arthroplasty of both shorter and longer assumptions for its effectiveness is examined in the sensitivity analysis.

In the reference case, the pathway of unicompartmental knee arthroplasty resulted in a small gain in effectiveness to 12.21 quality-adjusted life years compared with 12.19 quality-adjusted life years when total knee arthroplasty is chosen. There was minimal change in costs, with an increase from $18,995 to $19,000 (in 1998 United States dollars). The incremental cost-effectiveness ratio for unicompartmental knee arthroplasty under the reference case assumption is negligible with a cost of $277 per quality-adjusted life year gained. This ratio indicates that unicompartmental knee arthroplasty was more effective than total knee arthroplasty, and this increased effectiveness required a minimal additional cost.

Sensitivity Analysis

Effect of the Durability of Unicompartmental Knee

Replacement Compared with Total Knee Replacement The durability of unicompartmental knee replacements remains uncertain relative to total knee replacements. Sensitivity analysis was used to evaluate the effects of this uncertainty by varying the underlying assumption for the durability of unicompartmental knee replacements and determining the changes to the cost-effectiveness ratio. The cost-effectiveness of unicompartmental knee arthroplasty is lost as the durability of the implant is assumed to decrease. The reference case assumes a survival of fifteen years for primary total knee replacement. The assumption of a longer survival for total knee replacement compared with unicompartmental knee replacement reflects the longer experience and more complete documentation of the durability of total knee replacement. The cost-effectiveness of unicompartmental knee arthroplasty relies largely on its ability to produce clinical results approaching those of total knee arthroplasty. In sensitivity analyses that assume unicompartmental knee replacement has a survival of eleven years, it becomes both less effective (12.16 compared with 12.19 quality-adjusted life years) and more costly than standard total knee arthroplasty ($19,233 compared with $18,995). This scenario results in total knee arthroplasty becoming a dominant choice. Specifically, total knee arthroplasty becomes both more effective and less costly when unicompartmental knee replacement is assumed to have a survival below the threshold of eleven years (Table III).

View Larger

TABLE III Incremental Costs, Effectiveness, and Cost-Effectiveness Ratios with Use of Reference Case and Sensitivity Analyses*

Values Used in Sensitivity Analysis	Incremental Cost of Unicompartmental Compared with Total Knee Arthroplasty	Incremental Effectiveness of Unicompartmental Compared with Total Knee Arthroplasty (QALY)	Incremental Cost-Effectiveness Ratio of Unicompartmental Compared with Total Knee Arthroplasty (Cost/QALY)
Reference case	+$5	+0.02	$277
Unicompartmental knee replacement
survival assumed to be 12 yr
Total knee replacement survival
assumed to be 15 yr
Scenario 1	+$238	-0.03	Total knee replacement is dominant†
Unicompartmental knee replacement
survival assumed to be 11 yr
Total knee replacement survival
assumed to be 15 yr
Scenario 2	+$6,236	+0.13	$45,958
Unicompartmental knee replacement
survival assumed to be 17 yr
Total knee replacement survival
assumed to be 20 yr
Scenario 3	+$6,859	+0.05	$117,103
Unicompartmental knee replacement
survival assumed to be 15 yr
Total knee replacement survival
assumed to be 20 yr
Cost of unicompartmental knee arthroplasty increased by 25%	+$2,661	+0.02	$165,354
Cost of unicompartmental knee arthroplasty decreased by 25%	-$2,652	+0.02	Unicompartmental knee replacement is dominant‡

Values are based on 1998 United States dollars. QALY = quality-adjusted life year. †Unicompartmental knee arthroplasty increases cost and decreases quality-adjusted life years. ‡Unicompartmental knee arthroplasty decreases cost and increases quality-adjusted life years.

Add to My JBJS

TABLE III Incremental Costs, Effectiveness, and Cost-Effectiveness Ratios with Use of Reference Case and Sensitivity Analyses*

Values Used in Sensitivity Analysis	Incremental Cost of Unicompartmental Compared with Total Knee Arthroplasty	Incremental Effectiveness of Unicompartmental Compared with Total Knee Arthroplasty (QALY)	Incremental Cost-Effectiveness Ratio of Unicompartmental Compared with Total Knee Arthroplasty (Cost/QALY)
Reference case	+$5	+0.02	$277
Unicompartmental knee replacement
survival assumed to be 12 yr
Total knee replacement survival
assumed to be 15 yr
Scenario 1	+$238	-0.03	Total knee replacement is dominant†
Unicompartmental knee replacement
survival assumed to be 11 yr
Total knee replacement survival
assumed to be 15 yr
Scenario 2	+$6,236	+0.13	$45,958
Unicompartmental knee replacement
survival assumed to be 17 yr
Total knee replacement survival
assumed to be 20 yr
Scenario 3	+$6,859	+0.05	$117,103
Unicompartmental knee replacement
survival assumed to be 15 yr
Total knee replacement survival
assumed to be 20 yr
Cost of unicompartmental knee arthroplasty increased by 25%	+$2,661	+0.02	$165,354
Cost of unicompartmental knee arthroplasty decreased by 25%	-$2,652	+0.02	Unicompartmental knee replacement is dominant‡

Multivariate sensitivity analysis was also performed with use of a broader range of fifteen to twenty years for the expected durability of total knee replacement. These analyses indicated that it is necessary for the assumed survival of the unicompartmental knee replacement to be within three to four years of the assumed survival of the total knee replacement in order to maintain the cost-effectiveness of choosing unicompartmental knee arthroplasty. This is demonstrated by analyses that assume that total knee replacement survival is twenty years. With use of this assumption, the incremental cost-effectiveness ratio of unicompartmental knee arthroplasty is $45,958 per quality-adjusted life-year gained compared with total knee arthroplasty when a unicompartmental knee replacement is assumed to survive for seventeen years. This is below the commonly accepted threshold of $50,000 per quality-adjusted life year often used to determine cost-effective procedures^11,30. In contrast, when the survival of a unicompartmental knee replacement is assumed to be fifteen years and the survival of a total knee replacement is assumed to be twenty years, the incremental cost-effectiveness ratio increases to more than $100,000 per quality-adjusted life-year gained (Table III). The incremental cost-effectiveness ratio continues to increase, and the cost-effectiveness of unicompartmental knee arthroplasty decreases as the survival of a unicompartmental knee replacement is assumed to be lower relative to the survival of a total knee replacement.

Effect of Function Following Unicompartmental Knee Arthroplasty

The initial published findings indicate that unicompartmental knee arthroplasty results in function that is at least comparable with that seen after total knee arthroplasty^2-10. The reference case reflects these results by assuming that both unicompartmental knee arthroplasty and total knee arthroplasty result in a high level of function and pain relief. However, there are a limited number of controlled studies that have directly compared the clinical function after unicompartmental knee arthroplasty and total knee arthroplasty. This uncertainty was addressed in a sensitivity analysis that examined the effect of higher and lower values for the utility of unicompartmental knee arthroplasty on its cost-effectiveness.

The reference case results show a small gain of 0.02 quality-adjusted life years when unicompartmental knee arthroplasty is chosen over total knee arthroplasty. These gains are lost when the utility of unicompartmental knee arthroplasty is assumed to be less than that of total knee arthroplasty. Conversely, there is a further incremental increase in the cost-effectiveness when the utility of unicompartmental knee arthroplasty is assumed to be >0.9. When unicompartmental knee arthroplasty is assigned the maximal value of 1.0, it results in a total of 13.20 quality-adjusted life years as opposed to 12.19 quality-adjusted life years for a gain of 1.01 quality-adjusted life years. Unicompartmental knee arthroplasty becomes a more cost-effective choice under these assumptions, as the gains in incremental effectiveness increase with no additional cost relative to the reference case.

Effect of Cost of Unicompartmental Knee Arthroplasty

There is a small incremental additional cost from unicompartmental knee arthroplasty with use of the reference case assumptions for the relative costs of unicompartmental and total knee arthroplasty. The minimal cost increase in the reference case results from the assumption that there is a decrease in the physician's fee for unicompartmental knee arthroplasty relative to the fee reimbursement for total knee arthroplasty. Unicompartmental knee arthroplasty becomes a less cost-effective alternative in a sensitivity analysis in which the cost of unicompartmental knee arthroplasty is assumed to be higher than the cost of total knee arthroplasty. An increase of 25% resulted in an incremental cost-effectiveness ratio of $165,354 per quality-adjusted life year gained when unicompartmental knee arthroplasty was chosen over total knee arthroplasty. This indicates that the cost-effectiveness of unicompartmental knee arthroplasty may be lost if it requires a large relative increase in cost compared with total knee arthroplasty (Table III).

The use of gross costing based on Medicare reimbursement does not account for the potential savings of unicompartmental knee arthroplasty from implant costs or decreased hospital length of stay. This is due to the fact that both unicompartmental knee arthroplasty and primary total knee arthroplasty are assigned the same DRG, resulting in a similar cost assumption for the hospital stay. A sensitivity analysis was performed to examine the effect of a 25% cost-savings in a comparison of unicompartmental knee arthroplasty with total knee arthroplasty. A decrease of 25% in the assumed costs of unicompartmental knee arthroplasty resulted in an overall savings of $2652 in the lifetime treatment costs compared with those of primary total knee arthroplasty (Table III).

Discussion

Materials and Methods | Results | Discussion | Appendix | References

The use of unicompartmental knee arthroplasty is expanding as an alternative to total knee arthroplasty for patients with end-stage arthritis limited to either the medial or lateral compartment¹. Total knee arthroplasty is widely accepted as a highly cost-effective treatment for knee arthritis²⁰. This study confirms the intuitive conclusion that unicompartmental knee arthroplasty is a potentially cost-effective choice in patients with unicompartmental arthritis as long as it results in levels of durability and function comparable with those after total knee arthroplasty. Under these assumptions, unicompartmental knee arthroplasty results in a small improvement in effectiveness at a minimal increased cost compared with total knee arthroplasty. These cost-effectiveness gains are lost when unicompartmental knee arthroplasty is assumed to have a functional life that is more than three to four years shorter than that of total knee arthroplasty.

The main sources of uncertainty in this analysis arise from the estimation of the costs, effectiveness, and utilities of health states included in the decision model. This study identified key variables that require further study, including the relative durability of unicompartmental knee replacement and total knee replacement as well as the relative long-term utility of these procedures. The reference case relies on the assumption that unicompartmental knee arthroplasty results in a high level of functional improvement for twelve years. Conversely, when unicompartmental knee arthroplasty is assumed to result in substantially worse function or survival shorter than twelve years, total knee arthroplasty becomes a more cost-effective alternative. There have been several promising studies that have indicated that rates of survival and function following unicompartmental knee arthroplasty are comparable with those after total knee arthroplasty in selected groups of patients^2-10. Longer-term results are also encouraging, with a recent study by Berger et al. who described sixty-two patients who were managed with unicompartmental knee arthroplasty and were followed for a minimum of ten years. The Kaplan-Meier survivorship analysis in that study demonstrated a survival rate of 98% at ten years and 96% at thirteen years³¹. Similar results were recently described by Naudie et al. in a study of 113 unicompartmental knee replacements that had a mean follow-up of ten years³². They reported a ten-year survival rate of 90% in a group of patients with a mean age of sixty-eight years at the time of the index arthroplasty. The present cost-effectiveness analysis indicates that those clinical findings support the use of unicompartmental knee arthroplasty in carefully selected patients.

There is also uncertainty about several of the utility values used in this study. Ethgen et al. reviewed the literature to determine the effect of total hip and knee arthroplasty on health-related quality of life³³. The observed preoperative utility value for patients managed with a total knee arthroplasty ranged from 0.45 to 0.91; the mean postoperative utility values after total knee arthroplasty ranged from 0.57 to 0.99 in the six studies reviewed. The utility values used in the present study for knee arthritis, unicompartmental knee arthroplasty, and total knee arthroplasty fall in these ranges and were extrapolated from studies that determined the utility value for arthritis and lower-extremity impairment^23-26. Sensitivity analyses were used to identify threshold values for these uncertain variables that would indicate the cost-effectiveness of unicompartmental knee arthroplasty. Sensitivity analysis demonstrated that unicompartmental knee arthroplasty must result in a level of function and utility similar to that achieved with total knee arthroplasty to remain cost-effective. This analysis would benefit from empirical studies that more directly measure the long-term utility of both unicompartmental knee arthroplasty and total knee arthroplasty.

The relative costs of unicompartmental knee arthroplasty and total knee arthroplasty are also key variables that could impact the potential cost-effectiveness gains of unicompartmental arthroplasty. The gross-costing methods used in this study may not provide as precise an estimate of costs as would more detailed micro-costing techniques¹¹. However, the use of the gross-cost method has the advantage of relying on the uniform reimbursements provided by Medicare. Bozic et al. highlighted the variability in the actual cost of total joint arthroplasty that results from differences in patient and procedure characteristics^34,35. While Medicare reimbursement may overestimate or underestimate the actual costs of care, the cost estimates derived from this method for the present study are in the range of previously published estimates of the cost of primary and revision total knee arthroplasty derived with use of micro-costing techniques^36,37. The effect of the uncertainty about the cost variables was examined with use of sensitivity analysis. Sensitivity analyses with use of a range of values for these cost estimates indicate that the cost of unicompartmental knee arthroplasty needs to be comparable with that of total knee arthroplasty to support it as a cost-effective alternative. The reference case assigns a surgeon's fee to unicompartmental knee arthroplasty that is lower than that for total knee arthroplasty on the basis of Medicare reimbursement. A large change in the relative reimbursement for either procedure would require a reassessment of the cost-effectiveness findings of this analysis. For example, cost savings due to a decreased length of stay, implant charges, or more rapid rehabilitation would result in a cost savings when unicompartmental knee arthroplasty is chosen over primary total knee arthroplasty. In addition, improved surgical techniques and implant design may lead to enhanced longevity. This analysis does not include differences in implant costs, hospital length of stay, and post-discharge costs related to rehabilitation. All of these factors seem to favor the cost-effectiveness of unicompartmental knee arthroplasty as it is currently performed. Future studies will aid in our understanding of the proper value of the aforementioned variables and their role in determining the cost-effectiveness of unicompartmental arthroplasty.

The applicability of these findings must also be guided by an understanding of the assumptions about the reference case used in this study. The reference case of this study assumes a patient age of sixty-five years. However, in many instances, a unicondylar knee replacement is implanted in patients who are eighty years old or older. The literature has demonstrated a high rate of survival for unicompartmental knee replacements in this elderly population^2-10. If a successful implant survives for the remaining lifespan of such patients, the cost-effectiveness of the unicondylar arthroplasty is likely to be improved. Additional analysis will also be helpful as the indications for unicompartmental arthroplasty are expanded to younger, more active patients^1,20. This study does not address the cost-effectiveness of unicompartmental knee arthroplasty in this patient population. The cost-effectiveness of unicompartmental knee arthroplasty in younger patients should be reexamined when more data on survival and function are available from controlled long-term trials. A key assumption of this analysis is that a revision arthroplasty after a unicondylar knee arthroplasty will not function as well as a primary total knee arthroplasty or be as durable. In the past, the bone cuts on the tibia when performing a unicondylar arthroplasty were more extensive, and subsequent revision to a total knee arthroplasty could require metal augments and/or a stemmed tibial component. Newer surgical techniques for unicompartmental knee arthroplasty have been adapted to minimize bone resection, and, as a result, subsequent revision to total knee arthroplasty generally requires standard implants. Therefore, the assumptions in the model may underestimate the cost-effectiveness advantage associated with unicondylar arthroplasty. Further long-term follow-up will clarify the function and durability of conversion to total knee arthroplasty following unicondylar arthroplasty.

Unicompartmental knee arthroplasty has been advocated as a potential technological advance in the treatment of unicompartmental knee arthritis. Despite a lack of long-term data directly comparing total knee arthroplasty with unicompartmental knee arthroplasty in these patients, the interest in implementing this new technology is growing. This analysis demonstrates the potential for unicompartmental knee arthroplasty to be a cost-effective alternative to total knee arthroplasty. These results depend on the assumption that the cost as well as the durability and function of a unicompartmental knee replacement are similar to those observed with total knee arthroplasty. The data suggest that these are valid assumptions in carefully selected patients. The dissemination of unicompartmental knee arthroplasty will be better justified if long-term clinical trials confirm levels of prosthetic survival and function that meet or exceed the thresholds identified in this study. These thresholds can help orthopaedic surgeons to evaluate the results of clinical trials as they become available and help them to decide whether to perform unicompartmental knee arthroplasty. Controlled, long-term studies will be useful in more clearly delineating the cost-effective indications for this procedure, particularly when used in younger patients.

Appendix

Materials and Methods | Results | Discussion | Appendix | References

A table listing the literature review on outcomes in unicompartmental knee arthroplasty, a figure of the detailed decision model, and a summary of the results of the literature review are available with the electronic versions of this article, on our web site at (go to the article citation and click on Supplementary Material) and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM). ?

References

Materials and Methods | Results | Discussion | Appendix | References

Iorio R, Healy WL. Unicompartmental arthritis of the knee. J Bone Joint Surg Am. 2003;85: 1351-64.851351 2003 [PubMed]

Newman JH, Ackroyd CE, Shah NA. Unicompartmental or total knee replacement? Five-year results of a prospective, randomised trial of 102 osteoarthritic knees with unicompartmental arthritis. J Bone Joint Surg Br. 1998;80: 862-5.80862 1998 [PubMed][CrossRef]

Murray DW, Goodfellow JW, O'Connor JJ. The Oxford medial unicompartmental arthroplasty: a ten-year survival study. J Bone Joint Surg Br. 1998;80: 983-9.80983 1998 [PubMed][CrossRef]

Berger RA, Nedeff DD, Barden RM, Sheinkop MM, Jacobs JJ, Rosenberg AG, Galante JO. Unicompartmental knee arthroplasty. Clinical experience at 6- to 10-year followup. Clin Orthop Relat Res. 1999;367: 50-60.36750 1999

Argenson JN, Chevrol-Benkeddache Y, Aubaniac JM. Modern unicompartmental knee arthroplasty with cement: a three to ten-year follow-up study. J Bone Joint Surg Am. 2002;84: 2235-9.842235 2002 [PubMed]

Weale AE, Murray DW, Crawford R, Psychoyios V, Bonomo A, Howell G, O'Connor J, Goodfellow JW. Does arthritis progress in the retained compartments after `Oxford' medial unicompartmental arthroplasty? A clinical and radiological study with a minimum ten-year follow-up. J Bone Joint Surg Br. 1999;81: 783-9.81783 1999 [PubMed][CrossRef]

Squire MW, Callaghan JJ, Goetz DD, Sullivan PM, Johnson RC. Unicompartmental knee replacement. A minimum 15 year followup study. Clin Orthop Relat Res. 1999;367: 61-72.36761 1999 [PubMed]

Kumar A, Fiddian NJ. Medial unicompartmental arthroplasty of the knee. Knee. 1999;6: 21-3.621 1999 [CrossRef]

Svard UC, Price AJ. Oxford medial unicompartmental knee arthroplasty. A survival analysis of an independent series. J Bone Joint Surg Br. 2001;83: 191-4.83191 2001 [PubMed][CrossRef]

Lewold S, Robertson O, Knutson K, Lidgren L. Revision of unicompartmental knee arthroplasty: outcome in 1,135 cases from the Swedish Knee Arthroplasty study. Acta Orthop Scand. 1998;69: 469-74.69469 1998 [CrossRef]

Gold MR, Siegel JE, Russell LB, Weinstein MC. Cost-effectiveness in health and medicine. New York: Oxford University Press; 1996. 1996

Anderson RN, DeTurk RB. United States life tables 1999. National Vital Statistics Reports. 2002;50: 1-40.501 2002 [PubMed]

Weinstein MC, Stason WB. Foundations of cost-effectiveness analysis for health and medical practices. N Engl J Med. 1977;296: 716-21.296716 1977 [CrossRef]

Bozic KJ, Rosenberg AG, Huckman RS, Herndon JH. Economic evaluation in orthopaedics. J Bone Joint Surg Am. 2003;85: 129-42.85129 2003

Detsky AS, Naglie G, Krahn MD, Naimark D, Redelmeier DA. Primer on medical decision analysis: Part 1—Getting started. Med Decis Making. 1997;17: 123-5.17123 1997 [PubMed][CrossRef]

Detsky AS, Naglie G, Krahn MD, Redelmeier DA, Naimark D. Primer on medical decision analysis: Part 2—Building a tree. Med Decis Making. 1997;17: 126-35.17126 1997 [PubMed][CrossRef]

Naglie G, Krahn MD, Naimark D, Redelmeier DA, Detsky AS. Primer on medical decision analysis: Part 3—Estimating probabilities and utilities. Med Decis Making. 1997;17: 136-41.17136 1997 [CrossRef]

Krahn MD, Naglie G, Naimark D, Redelmeier DA, Detsky AS. Primer on medical decision analysis: Part 4—Analyzing the model and interpreting the results. Med Decis Making.1997;17: 142-51.17142 1997 [CrossRef]

Redelmeier DA, Detsky AS, Krahn MD, Naimark D, Naglie G. Guidelines for verbal presentations of medical decision analyses. Med Decis Making. 1997;17: 228-30.17228 1997 [PubMed][CrossRef]

Archibeck MJ,White RE Jr. What's new in adult reconstructive knee surgery. J Bone Joint Surg Am. 2004;86: 1839-49.861839 2004 [PubMed]

Hervey SL, Purves HR, Guller U, Toth AP, Vail TP, Pietrobon R. Provider volume of total knee arthroplasties and patient outcomes in the HCUP-nationwide inpatient sample. J Bone Joint Surg Am. 2003;83: 1775-83.831775 2003

Katz JN, Barrett J, Mahomed NN, Baron JA, Wright RJ, Losina E. Association between hospital and surgeon procedure volume and the outcomes of total knee replacement. J Bone Joint Surg Am. 2004;86: 1909-16.861909 2004

Fryback DG, Dasbach EJ, Klein R, Klein BE, Dorn N, Peterson K, Martin PA. The Beaver Dam Health Outcomes Study: initial catalog of health-state quality factors. Med Decis Making. 1993;13: 89-102.1389 1993 [CrossRef]

Tengs TO, Wallace A. One thousand health-related quality-of-life estimates. Med Care. 2000;38: 583-637.38583 2000 [PubMed][CrossRef]

Gold MR, Franks P, McCoy KI, Fryback DG. Toward consistency in cost-utility analyses: using national measures to create condition-specific values. Med Care. 1998;36: 778-92.36778 1998 [PubMed][CrossRef]

Gold M, Franks P, Erickson P. Assessing the health of the nation. The predictive value of a preference-based measure and self-rated health. Med Care. 1996;34: 163-77.34163 1996 [PubMed][CrossRef]

HCIA, Ernst and Young. The DRG Handbook. Comparative clinical and financial standards. Baltimore: HCIA, Ernst and Young; 1999. 1999

Lave JR, Pashos CL, Anderson GF, Brailer D, Bubolz T, Conrad D, Freund DA, Fox SH, Keeler E, Lipscomb J. Costing medical care: using Medicare administrative data. Med Care. 1994;32(7 Suppl): JS77-89.32JS77 1994 [PubMed][CrossRef]

Health Care Finance Administration. Final rule of medicare program's fee schedule for physicians' services for calendar year 1998. Fed Regist. 1997. 1997

Chang RW, Pellissier JM, Hazen GB. A cost-effectiveness analysis of total hip arthroplasty for osteoarthritis of the hip. JAMA. 1996;275: 858-65.275858 1996 [PubMed][CrossRef]

Berger RA, Meneghini RM, Jacobs JJ, Sheinkop MB, Della Valle CJ, Rosenberg AG, Galante JO. Results of unicompartmental knee arthroplasty at a minimum of ten years of follow-up. J Bone Joint Surg Am. 2005;87: 999-1006.87999 2005 [PubMed][CrossRef]

Naudie D, Guerin J, Parker DA, Bourne RB, Rorabeck CH. Medial unicompartmental knee arthroplasty with the Miller-Galante prosthesis. J Bone Joint Surg Am. 2004;86: 1931-5.861931 2004 [PubMed]

Ethgen O, Bruyere O, Richy F, Dardennes C, Reginster JY. Health-related quality of life in total hip and total knee arthroplasty. A qualitative and systematic review of the literature. J Bone Joint Surg Am. 2004;86: 963-74.86963 2004

Bozic KJ, Durbhakula S, Berry DJ, Naessens JM, Rappaport K, Cisternas M, Saleh KJ, Rubash HE. Differences in patient and procedure characteristics and hospital resource use in primary and revision total joint arthroplasty: a multicenter study. J Arthroplasty. 2005;20(7 Suppl 3): 17-25.2017 2005 [CrossRef]

Bozic KJ, Katz P, Cisternas M, Ono L, Ries MD, Showstack J. Hospital resource utilization for primary and revision total hip arthroplasty. J Bone Joint Surg Am. 2005;87: 570-6.87570 2005 [PubMed][CrossRef]

Healy WL, Finn D. The hospital cost and the cost of the implant for total knee arthroplasty. A comparison between 1983 and 1991 for one hospital. J Bone Joint Surg Am. 1994;76: 801-6.76801 1994 [PubMed]

Reuben JD, Meyers SJ, Cox DD, Elliott M, Watson M, Shim SD. Cost comparison between bilateral simultaneous, staged, and unilateral total joint arthroplasty. J Arthroplasty. 1998;13: 172-9.13172 1998 [PubMed][CrossRef]

Topics

osteoarthritis ; knee replacement arthroplasty ; cost-effectiveness analysis ; sensitivity analysis

Username

Password

Access for Patients

Forgot Password?

Have a subscription to the print edition?

Not a Subscriber?

Buy this Article

Get online access for 30 days for $35

New to JBJS?

Subscribe to the online edition for 30 days for $75

Register for a FREE limited account to get full access to all CME activities, to comment on public articles, or to sign up for alerts.

Have a subscription to the print edition?

Current subscribers to The Journal of Bone & Joint Surgery in either the print or quarterly DVD formats receive free online access to JBJS.org.

Activate your online account now

Forgot your password?

Enter your username and email address. We'll send you a reminder to the email address on record.

Username:*

Email Address:*

Forgot your username or need assistance? Please contact customer service at subs@jbjs.org. If your access is provided
by your institution, please contact you librarian or administrator for username and password information. Institutional
administrators, to reset your institution's master username or password, please contact subs@jbjs.org

References

Accreditation Statement

These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.

CME Activities Associated with This Article

Submit a Comment

Please read the other comments before you post yours. Contributors must reveal any conflict of interest.
Comments are moderated and will appear on the site at the discretion of JBJS editorial staff.

* = Required Field

Comment Author(s) * (if multiple authors, separate names by comma)

Example: John Doe

Affiliation & Institution*

Comment Title*

Comment*

Cancel

Print
PDF
Email

Recipient(s) will receive an email with a link (good for 5 days) to 'Cost-Effectiveness Analysis of Unicompartmental Knee Arthroplasty as an Alternative to Total Knee Arthroplasty for Unicompartmental Osteoarthritis'.
Your Name:*
Example: John Doe

Email Address:* CC Me:
Enter your valid email address. Example: jdoe@example.com

Recipient's Email Address:*

Separate multiple email address with semi-colons (up to 5).

Subject:* 's The Journal of Bone & Joint Surgery: 'Cost-Effectiveness Analysis of Unicompartmental Knee Arthroplasty as an Alternative to Total Knee Arthroplasty for Unicompartmental Osteoarthritis'
Subject for your email.

Message:

(Optional, message will truncate at 1000 characters)

Processing your request... Please Wait...

Copyright © in the material you requested is held by The Journal of Bone & Joint Surgery, Inc. (unless otherwise noted). This email ability is provided as a courtesy, and by using it you agree that that you are requesting the material solely for personal, non-commercial use, and that it is subject to Journal of Bone & Joint Surgery, Inc.'s Terms of Use. The information provided in order to email this topic will not be used to send unsolicited email, nor will it be furnished to third parties. Please refer to The Journal of Bone & Joint Surgery Inc.'s Privacy Policy for further information.

Copyright © The Journal of Bone & Joint Surgery Inc. All rights reserved.
Share
Get Citation

Nelson F. Soohoo, Husham Sharifi, Gerald Kominski, Jay R. Lieberman; Cost-Effectiveness Analysis of Unicompartmental Knee Arthroplasty as an Alternative to Total Knee Arthroplasty for Unicompartmental Osteoarthritis. The Journal of Bone & Joint Surgery. 2006 Sep;88(9):1975-1982.

Download citation file:

RIS (Zotero)

EndNote

BibTex

Medlars

ProCite

RefWorks

Reference Manager

Copyright © The Journal of Bone and Joint Surgery, Inc.
Rights & Permissions
Article Alerts

Processing your request... Please Wait.
Submit a Comment
Data Supplements