Abstract

Objective

To conduct a stratified cost-utility analysis of total versus partial hip arthroplasty as a function of clinical subtype.

Method

All cases of this type of intervention were analysed between 2010 and 2016 in the Basque Health Service, gathering data on clinical outcomes and resource use to calculate the cost and utility in quality-adjusted life years (QALYs) at individual level. The statistical analysis included applying the propensity score to balance the groups, and seemingly unrelated regression models to calculate the incremental cost-utility ratio and plot the cost-effectiveness plane. The interaction between age group and American Society of Anesthesiologists (ASA) risk class was assessed in the multivariate analysis.

Results

The study identified 5867 patients diagnosed with femoral neck fracture, of whom 1307 and 4560 were treated with total and partial hip arthroplasty, respectively. In the cost-utility analysis based on the seemingly unrelated regression, total hip arthroplasty was found to have a higher cost and higher utility (2465€ and 0.42 QALYs). Considering a willingness-to-pay threshold of €22,000 per QALY, total hip arthroplasty was cost-effective in the under-80-year-old subgroup. Among patients above this age, hemiarthroplasty was cost-effective in ASA class I-II patients and dominant in ASA class III-IV patients.

Conclusions

Subgroup analysis supports current daily clinical practice in displaced femoral neck fractures, namely, using partial replacement in most patients and reserving total replacement for younger patients.

Keywords:
Cost-effectiveness; Cost-utility; Displaced femoral neck; Hip replacement; Total hip arthroplasty; Hemiarthroplasty

Resumen

Objetivo

Realizar un análisis de coste-utilidad de la prótesis total de cadera frente a la prótesis parcial.

Método

Se analizaron todos los casos intervenidos desde 2010 hasta 2016 en el Servicio Vasco de Salud, recogiendo resultados clínicos y uso de recursos para calcular individualmente el coste y la utilidad en años de vida ajustados por calidad (AVAC). El análisis estadístico incluyó el pareamiento por puntaje de propensión para balancear los grupos y modelos de regresión aparentemente no relacionados para calcular la razón de coste-utilidad incremental y el plano de coste-efectividad. La interacción de grupo de edad y riesgo según la American Society of Anesthesiologists (ASA) se incluyó en el análisis multivariante.

Resultados

Se identificaron 1307 pacientes con prótesis total y 4560 con prótesis parcial. Al hacer el análisis de coste-utilidad con modelos de regresión aparentemente no relacionados el resultado fue mayor coste y mayor utilidad para la prótesis total (2465 € y 0,42 AVAC). Para un umbral de 22.000 € por AVAC, la prótesis total fue coste-efectiva en el subgrupo de menores de 80 años. En el grupo de mayores de 80 años la parcial fue coste-efectiva en los casos con riesgo ASA I-II y dominante en los ASA III-IV.

Conclusiones

El análisis de subgrupos ratifica la práctica clínica habitual en las fracturas de cuello de fémur desplazadas de intervenir a la mayoría de los pacientes mediante prótesis parcial y reservar la prótesis total para los pacientes más jóvenes.

Palabras clave:
Coste-efectividad; Coste-utilidad; Fractura de cuello de fémur desplazada; Prótesis de cadera; Prótesis de cadera total; Hemiartroplastia

Introduction

Hip fractures are currently a public health problem, evidenced by a high and growing incidence. In Spain they increased from 26,834 in 2000 to 35,997 in 2012, with the respective impact in terms of mortality that this entails, as one in six patients dies during the first year.¹1. Etxebarria-Foronda I, Arrospide A, Soto-Gordoa M, et al. Regional variability in changes in the incidence of hip fracture in the Spanish population (2000-2012). Osteoporos Int. 2015;26:1491-7.^,22. Caeiro JR, Bartra A, Mesa-Ramos M, et al. Burden of first osteoporotic hip fracture in Spain: a prospective, 12-month, observational study. Calcif Tissue Int. 2017;100:29-39. Further, those who survive experience a significant reduction in quality of life and autonomy measured by EuroQol-5D-3L (EQ-5D) and Barthel index, respectively.²2. Caeiro JR, Bartra A, Mesa-Ramos M, et al. Burden of first osteoporotic hip fracture in Spain: a prospective, 12-month, observational study. Calcif Tissue Int. 2017;100:29-39. As the incidence is expected to increase in the near future due to population ageing, such a scenario will be associated with an even greater burden in terms of both, loss of health and loss of social and healthcare costs.¹1. Etxebarria-Foronda I, Arrospide A, Soto-Gordoa M, et al. Regional variability in changes in the incidence of hip fracture in the Spanish population (2000-2012). Osteoporos Int. 2015;26:1491-7.^,22. Caeiro JR, Bartra A, Mesa-Ramos M, et al. Burden of first osteoporotic hip fracture in Spain: a prospective, 12-month, observational study. Calcif Tissue Int. 2017;100:29-39. In Europe, with over 610,000 cases, hip fractures accounted for more disability-adjusted life years lost than many common cancers.³3. Johnell O, Kanis JA. An estimate of the worldwide prevalence and disability associated with osteoporotic fractures. Osteoporos Int J Establ Result Coop Eur Found Osteoporos Natl Osteoporos Found USA. 2006;17:1726-33. At the same time, their management entails high costs to address surgical care, medical care, and rehabilitation treatment.⁴4. Ojeda-Thies C, Saez-Lopez P, Currie CT, et al. Spanish National Hip Fracture Registry (RNFC): analysis of its first annual report and international comparison with other established registries. Osteoporos Int. 2019;30:1243-54. The social impact is also noteworthy, as denoted by the high percentage of community-dwelling patients which cannot be discharged to home.⁵5. Beaupre L, Sobolev B, Guy P, et al. Discharge destination following hip fracture in Canada among previously community-dwelling older adults, 2004-2012: database study. Osteoporos Int. 2019;30:1383-94.

Displaced femoral neck fractures usually require replacement, most commonly with partial hip replacement, also called hip hemiarthroplasty (HA), given that it is less aggressive, achieves similar results in terms of health-related quality of life and is less expensive than total hip arthroplasty (THA).⁴4. Ojeda-Thies C, Saez-Lopez P, Currie CT, et al. Spanish National Hip Fracture Registry (RNFC): analysis of its first annual report and international comparison with other established registries. Osteoporos Int. 2019;30:1243-54.^,66. Bhandari M, Einhorn TA, et al., HEALTH Investigators. Total hip arthroplasty or hemiarthroplasty for hip fracture. N Engl J Med. 2019;381:2199-208. THA tends to be indicated for younger patients who have a better quality of life and longer life expectancy, as this type of replacement is more durable and associated with greater mobility.⁷7. Zhang B-F, Wang P-F, Huang H, et al. Interventions for treating displaced intracapsular femoral neck fractures in the elderly: a bayesian network meta-analysis of randomized controlled trials. Sci Rep. 2017;7:13103. Nonetheless, patients of advanced age with good quality of life also receive THA.⁴4. Ojeda-Thies C, Saez-Lopez P, Currie CT, et al. Spanish National Hip Fracture Registry (RNFC): analysis of its first annual report and international comparison with other established registries. Osteoporos Int. 2019;30:1243-54. Questions arise regarding the indications for this type of replacement given that THA renders better health-related quality of life but with greater surgical morbidity and higher cost.⁶6. Bhandari M, Einhorn TA, et al., HEALTH Investigators. Total hip arthroplasty or hemiarthroplasty for hip fracture. N Engl J Med. 2019;381:2199-208.^,77. Zhang B-F, Wang P-F, Huang H, et al. Interventions for treating displaced intracapsular femoral neck fractures in the elderly: a bayesian network meta-analysis of randomized controlled trials. Sci Rep. 2017;7:13103. Carroll et al.⁸8. Carroll C, Stevenson M, Scope A, et al. Hemiarthroplasty and total hip arthroplasty for treating primary intracapsular fracture of the hip: a systematic review and cost-effectiveness analysis. Health Technol Assess. 2011;15:1-74. carried out a systematic review concluding that THA seems more cost-effective than HA. Nonetheless, they suggest the need for a cost-effectiveness analysis stratified as a function of various different clinical profiles.

As delivery of care should differ based on patients' characteristics, the hypothesis was that the evaluation of resources used for hip replacement and their correspondence with patients' needs would contribute to a better decision-making in the Basque Health Service. Moreover, the economic evaluation of hip replacement based on real-world data would allow to cover the gap of studies seeking to evaluate the efficiency of orthopaedic treatments using recommended methodologies.⁹9. Ara R, Basarir H, Keetharuth AD, et al. Are policy decisions on surgical procedures informed by robust economic evidence? A systematic review. Int J Technol Assess Health Care. 2014;30:381-93. The objective of the study was to carry out a stratified cost-utility analysis as a function of the clinical subtypes of patients who underwent THA versus HA for the treatment of femoral neck fractures.

Method

The clinical trial continues to be considered the research design providing the highest level of evidence. However, there are few economic studies of THA using individual patient data from randomised clinical trials and observational studies.¹⁰10. Glick HA, Doshi JA, Sonnad SS, et al. Economic evaluation in clinical trials. Oxford, UK. Oxford University Press; 2014.^,1111. Garrison LPJ, Neumann PJ, Erickson P, et al. Using real-world data for coverage and payment decisions: the ISPOR real-world data task force report. Value Health. 2007;10:326-35. Instead, the development of electronic health records has facilitated the creation of databases of clinical data linked to administrative data, enabling the recording of all patients' interactions with the health system and the use of resources by individual patients (at different levels: primary care, emergency department, inpatient care, home care and outpatient specialist care).¹¹11. Garrison LPJ, Neumann PJ, Erickson P, et al. Using real-world data for coverage and payment decisions: the ISPOR real-world data task force report. Value Health. 2007;10:326-35. Such databases allow for the analysis of large samples of cases from clinical practice as a function of surgical procedure.⁹9. Ara R, Basarir H, Keetharuth AD, et al. Are policy decisions on surgical procedures informed by robust economic evidence? A systematic review. Int J Technol Assess Health Care. 2014;30:381-93.^,1111. Garrison LPJ, Neumann PJ, Erickson P, et al. Using real-world data for coverage and payment decisions: the ISPOR real-world data task force report. Value Health. 2007;10:326-35. But the analysis of samples of cases from clinical practice requires the use of procedures that improve the validity of the results, particularly regarding selection bias.¹²12. Berger ML, Dreyer N, Anderson F, et al. Prospective observational studies to assess comparative effectiveness: the ISPOR good research practices task force report. Value Health. 2012;15:217-30.

Design

The cost-utility study design was observational, based on statistical analysis using regression models like those employed in clinical trials with patient-level data.¹⁰10. Glick HA, Doshi JA, Sonnad SS, et al. Economic evaluation in clinical trials. Oxford, UK. Oxford University Press; 2014. The study was conducted from Spanish National Health System perspective, implying that the costs included are those associated with hospital care.

All cases of femoral neck fracture treated by HA or THA between 2010 and 2016 in the Basque Health Service were analysed. Cases were identified considering International Classification of Disease 9th edition Clinical Modification (ICD-9-CM) code 820** for the diagnosis of femoral neck fracture and ICD-9-CM code 81.51 and 81.52 for THA and HA, respectively. Patients were followed up until 31 December 2018, ensuring a follow-up period of at least 2 years in all cases.¹³13. Lopez-Bastida J, Oliva J, Antonanzas F, et al. A proposed guideline for economic evaluation of health technologies. Gac Sanit. 2010;24:154-70.

Study variables

The clinical research ethics committee of the Basque Country approved the study on 14 February 2019 (reference number PI2019010). Data were collected from the corporative database, which contains administrative and clinical records of the Basque Health Service in an anonymized form,¹³13. Lopez-Bastida J, Oliva J, Antonanzas F, et al. A proposed guideline for economic evaluation of health technologies. Gac Sanit. 2010;24:154-70. ncluding the variables: age, sex, socioeconomic status, hospital size, diagnoses required for calculating the Charlson comorbidity index,¹⁴14. Charlson ME, Pompei P, Ales KL, et al. A new method of classifying prognostic comorbidity in longitudinal studies: development and validation. J Chronic Dis. 1987;40:373-83. American Society of Anesthesiologists (ASA) class, history of antithrombotic drug use, type of anaesthesia, type of prosthesis, time to surgery in days, surgical time in minutes, hospital stay, complications up to 1 year after surgery (pulmonary thromboembolism, deep vein thrombosis, heart failure and/or pneumonia), life-long complications after surgery (loosening, luxation, fracture and/or infection of the prosthesis), date of death and place of residence. Regarding antithrombotic drugs, patients' prescription history was searched from before hospitalisation for the following Anatomical Therapeutic Chemical Classification (ATC) codes: B01AA (vitamin K antagonists), B01AB (heparin and derivatives) and B01AC (platelet aggregation inhibitors). The costs of the prosthesis, 1minute of operating room time for the trauma unit, the hospital stay, and complications by diagnosis-related group point were obtained from the accounting system of the Basque Health Service in euros for 2018. To estimate utility, data from the scientific literature¹⁵15. Garcia-Perez L, Ramos-Garcia V, Serrano-Aguilar P, et al. EQ-5D-5 L utilities per health states in Spanish population with knee or hip osteoarthritis. Health Qual Life Outcomes. 2019;17:164. was used, based on the generic questionnaire EQ-5D.¹⁶16. EuroQol Group. EuroQol - A new facility for the measurement of health-related quality of life. Health Policy. 1990;16:199-208. Quality-adjusted life years (QALYs) were then obtained for each patient by multiplying the years of life by the utility score for the period.¹⁷17. Drummond M, Sculpher M, Torrance G, et al. Methods for the economic evaluation of health care programmes. Oxford, UK: Oxford University Press. 2005. For patients who died during the follow-up, the date of death determined the duration of follow-up, and they were assigned a utility score of 0 at that point.¹⁰10. Glick HA, Doshi JA, Sonnad SS, et al. Economic evaluation in clinical trials. Oxford, UK. Oxford University Press; 2014. Data on unit costs and quality of life are shown in Table I of the online ^AppendixAppendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.gaceta.2021.02.006..

Cost-effectiveness

The efficiency of THA compared to HA was assessed by calculating the incremental cost-utility ratio (ICUR), that is, the incremental cost in euros divided by the incremental effectiveness measured in QALYs.¹³13. Lopez-Bastida J, Oliva J, Antonanzas F, et al. A proposed guideline for economic evaluation of health technologies. Gac Sanit. 2010;24:154-70.^,1717. Drummond M, Sculpher M, Torrance G, et al. Methods for the economic evaluation of health care programmes. Oxford, UK: Oxford University Press. 2005. Given that studies in the literature have not found clinical differences between THA and HA,⁶6. Bhandari M, Einhorn TA, et al., HEALTH Investigators. Total hip arthroplasty or hemiarthroplasty for hip fracture. N Engl J Med. 2019;381:2199-208. the same utilities were used for both cases and obtained from a previous Spanish study.¹⁵15. Garcia-Perez L, Ramos-Garcia V, Serrano-Aguilar P, et al. EQ-5D-5 L utilities per health states in Spanish population with knee or hip osteoarthritis. Health Qual Life Outcomes. 2019;17:164. Individual treatment costs for each patient were calculated by adding the costs of the resources used, namely, the costs of the prosthesis, the operating room, hospitalisation, and 1-year and life-long complications. For each resource, costs were calculated by multiplying the rate of use by the unit cost, and unit costs were provided by the Basque Health Service accounting department. Given that in the scientific literature, HA is associated with less operating room time and a shorter hospital ward stay, the costs of hospitalisation for surgery were broken down into operating room costs and costs associated with hospital ward stay.¹⁸18. Mar J, Anton-Ladislao A, Ibarrondo O, et al. Cost-effectiveness analysis of laparoscopic versus open surgery in colon cancer. Surg Endosc. 2018;32:4912-22. The costs of complications during this hospitalisation were assigned based on the extent of any increase in the surgical time and/or hospital ward stay.

Statistical analysis

The statistical analysis was carried out using R (version 3.3.2) and Stata (version 13) statistical programmes. A variant of the propensity score based on the genetic matching algorithm was applied to balance the populations such that the characteristics of the two groups did not differ significantly at baseline.¹⁹19. Kreif N, Grieve R, Radice R, et al. Methods for estimating subgroup effects in cost-effectiveness analyses that use observational data. Med Decis Making. 2012;32:750-63. This technique involves selecting individuals from each of the groups with the same characteristics as a function of the chosen variables with the goal of comparing homogenous groups and thereby reducing selection bias.²⁰20. Diamond A, Sekhon JS. Genetic matching for estimating causal effects: a general multivariate matching method for achieving balance in observational studies. Rev Econ Stat. 2012;95:932-45. The following variables were balanced at baseline: age, sex, socioeconomic status and ASA class. A cost-utility analysis was carried out before and after applying the propensity score, taking into account the effect of ASA class and age.

Once the sample groups had been balanced, a combined multivariate analysis for total cost and QALYs was carried out using seemingly unrelated regression (SUR) models.¹⁰10. Glick HA, Doshi JA, Sonnad SS, et al. Economic evaluation in clinical trials. Oxford, UK. Oxford University Press; 2014. The following variables were used as covariates: procedure, sex, age, socioeconomic status, hospital size, history of antithrombotic drug use, type of anaesthesia, Charlson index, ASA class and time to surgery. Initially, a model was built without interactions, and the ICUR was calculated as the ratio of the coefficients of the procedure variables in the cost and effectiveness regressions (incremental cost as the numerator and incremental effectiveness as the denominator).¹⁰10. Glick HA, Doshi JA, Sonnad SS, et al. Economic evaluation in clinical trials. Oxford, UK. Oxford University Press; 2014. This ICUR describes the additional costs for each additional QALY adjusted for the factors included in the cost and effectiveness models of the intervention. Subsequently, a subgroup analysis was carried out combining ASA class with age. Further, the SUR analysis assessed the uncertainty in the ICUR using the cost-effectiveness plane and the confidence ellipse, as it includes the correlation between the parameters of the two regressions (costs and QALYs) in the analysis using the variance-covariance matrix.²¹21. Willan AR, Briggs AH. Statistical analysis of cost-effectiveness data. Chichester: Wiley; 2006. The cost-effectiveness plane is a scatter plot in which the vertical axis represents the incremental costs and the horizontal axis the incremental effectiveness. In this plane, the ICUR is the slope of a line that joins any point to the origin.¹⁷17. Drummond M, Sculpher M, Torrance G, et al. Methods for the economic evaluation of health care programmes. Oxford, UK: Oxford University Press. 2005. The results of the regressions draw an ellipse of points in the plane establishing the confidence intervals. When the ellipse crosses the axes, it means that the differences are not statistically significant, as the confidence interval includes zero for the incremental cost or effectiveness.

Results

The study identified 5867 patients diagnosed with femoral neck fractures, of whom 1307 and 4560 were treated with THA and HA, respectively. As shown in Table 1, the mean age of patients treated was 75.41 years for THA and 84.79 years for HA. Notably, 49% of patients below 80 years of age underwent THA and 51% HA. In contrast, only 12% of those ≥80 years old underwent THA. The univariate analysis did not show significant differences by sex or socioeconomic status between the two groups. Instead, significant differences were detected in ASA class, Charlson index, and age, the HA group patients having a higher Charlson index (mean 2.59 vs 1.97), as well as higher ASA class and age than those in the THA group. There were also significant differences in mortality, the rate being higher in the HA group (66.7% vs 35.8% in the THA group), despite the longer follow-up of patients who underwent THA (4.12 years vs 3.02 years in the HA group).

During follow-up, the percentage of patients with any type of complication during the first year after surgery was lower in the THA group than in the HA group, while the percentage of patients with some long-life complication was higher.Table 2 indicates that the costs were significantly higher for patients who underwent THA than for those who underwent HA.

Table 3 shows the cost-utility analysis carried out before and after genetic matching. In both cases, THA is more costly and more effective than HA, with incremental differences after balancing the groups of €1825 and 0.55 QALYs. In the analysis by ASA class and age subgroups, the same results for ASA class I and II patients were found. In contrast, HA was dominant for patients aged ≥80 years old and classified as ASA class III or IV.

Table 4 summarises the results of the multivariate SUR model for the incremental cost and effectiveness without any type of interaction. These results are in line with those of the univariate analysis, indicating that THA was more costly and more effective than HA, with an incremental cost of €2,465 and an incremental effectiveness of 0.42 QALYs. The analysis of the subgroups derived from the interaction between ASA class and age in the SUR model (Table 5 and Fig. 1) revealed that THA was not cost effective in ASA class III-IV patients aged ≥ 80 years old. It should be noted that Table 4 and Table 5 show the results of the SUR models in a summarised way. Nevertheless, the complete SUR models results are available in Tables II-IV of the online ^AppendixAppendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.gaceta.2021.02.006..

Discussion

The main contribution of this economic assessment is to provide evidence that it is more efficient to perform HA in most patients with displaced femoral neck fracture and reserve THA for the youngest patients and those classified as low risk.²²22. Guyen O. Hemiarthroplasty or total hip arthroplasty in recent femoral neck fractures? Orthop Traumatol Surg Res OTSR. 2019;105:S95-101. This analysis has been possible thanks to the disaggregation of cost-effectiveness by subgroups as a function of age and ASA class. To restrict the economic assessment to the entire sample would have led to a misleading result, since it would not have addressed the clinical heterogeneity of patients. Further, the importance of adjusting the results is even more evident if the high cost of the surgical procedures studied is considered and that the already elevated incidence of femoral fractures is expected to grow in the future due to population ageing.²³23. Stronach BM, Bergin PF, Perez JL, et al. The rising use of total hip arthroplasty for femoral neck fractures in the United States. Hip Int J Clin Exp Res Hip Pathol Ther. 2020;30:107-13. It is also noteworthy that this is the first cost-utility analysis using individual clinical information extracted from corporate databases (real-world data) in Spain.¹¹11. Garrison LPJ, Neumann PJ, Erickson P, et al. Using real-world data for coverage and payment decisions: the ISPOR real-world data task force report. Value Health. 2007;10:326-35.

The unstratified results indicated that THA was more expensive and associated with more QALYs than HA and that the ICUR was lower than the €22,000 per QALY willingness-to-pay threshold or cut-off value.²⁴24. Sacristan JA, Oliva J, Campillo-Artero C, et al. What is an efficient health intervention in Spain in 2020? Gac Sanit. 2020;34:189-93. Although the incremental cost and effectiveness were lower once the groups were balanced, the ICUR remained practically stable, only changing from €2912 per QALY to €3310 per QALY. When the SUR model was used to adjust the incremental cost-effectiveness as a function of the different variables, the results were similar, THA being more expensive and more effective than HA, with an ICUR of €5869 per QALY. On the other hand, when the interaction between ASA class and age was included, this conclusion only held for the subgroups of patients under 80 years of age. In these patients, THA was cost-effective, with both the ICUR and the confidence intervals below the cut-off value and not crossing the axes of the cost-effectiveness plane. In contrast, the results in the subgroups of patients ≥ 80 years old are harder to interpret. THA was not cost-effective in the low risk (ASA class I-II) group, the confidence intervals being above the cut-off, and was dominated by HA in the high risk (ASA class III-IV) group. As can be observed in the cost-effectiveness plane, in this subgroup, the two surgical procedures have the same effectiveness but THA has an incremental cost of €2576. In economic assessments, an intervention is considered dominated when it has a lower utility for the patient at a higher cost.¹⁷17. Drummond M, Sculpher M, Torrance G, et al. Methods for the economic evaluation of health care programmes. Oxford, UK: Oxford University Press. 2005.

The results of the economic evaluation fit well with the distribution of replacement type in the subsample of patients above 80 years old, only 12% of these patients undergoing THA. On the other hand, they may seem inconsistent with the distribution in under-80-year-olds, THA being the procedure of choice in 49% of cases. It is plausible that surgeon experience at the local level to carry out a more complex procedure such as THA helps to explain these differences.⁸8. Carroll C, Stevenson M, Scope A, et al. Hemiarthroplasty and total hip arthroplasty for treating primary intracapsular fracture of the hip: a systematic review and cost-effectiveness analysis. Health Technol Assess. 2011;15:1-74. It has been reported that HA procedures are performed by a wide range of surgeons, while THA procedures in fractures tend to be carried out by fewer surgeons, with considerable experience.⁸8. Carroll C, Stevenson M, Scope A, et al. Hemiarthroplasty and total hip arthroplasty for treating primary intracapsular fracture of the hip: a systematic review and cost-effectiveness analysis. Health Technol Assess. 2011;15:1-74. The results are in line with this. Specifically, when analysing the differences in the distribution of the replacement type as a function of hospital size, it was found that the procedures corresponded to THA in 17% of cases in large hospitals and 32% of cases in small hospitals. It is likely that one of the reasons for this difference is that patients with more comorbidities are referred to large hospitals.⁴4. Ojeda-Thies C, Saez-Lopez P, Currie CT, et al. Spanish National Hip Fracture Registry (RNFC): analysis of its first annual report and international comparison with other established registries. Osteoporos Int. 2019;30:1243-54.

The results of studies reported in the literature are similar to ours, although they have not estimated cost-effectiveness as a function of clinical subgroup.⁸8. Carroll C, Stevenson M, Scope A, et al. Hemiarthroplasty and total hip arthroplasty for treating primary intracapsular fracture of the hip: a systematic review and cost-effectiveness analysis. Health Technol Assess. 2011;15:1-74.^,2525. Slover J, Hoffman MV, Malchau H, et al. A cost-effectiveness analysis of the arthroplasty options for displaced femoral neck fractures in the active, healthy, elderly population. J Arthroplasty. 2009;24:854-60. Based on Markov models, Slover et al.²⁵25. Slover J, Hoffman MV, Malchau H, et al. A cost-effectiveness analysis of the arthroplasty options for displaced femoral neck fractures in the active, healthy, elderly population. J Arthroplasty. 2009;24:854-60. calculated that the ICUR of THA vs HA was $1960 per QALY in the USA. They based themselves on a previous study by Keating et al.²⁶26. Keating JF, Grant A, Masson M, et al. Randomized comparison of reduction and fixation, bipolar hemiarthroplasty, and total hip arthroplasty Treatment of displaced intracapsular hip fractures in healthy older patients. J Bone Joint Surg Am. 2006;88:249-60. that indicated a better quality of life after 24 months in patients who underwent THA. The same data were used in another Markov model in the context of a systematic review to estimate an ICUR of £7952 per QALY in the United Kingdom.⁸8. Carroll C, Stevenson M, Scope A, et al. Hemiarthroplasty and total hip arthroplasty for treating primary intracapsular fracture of the hip: a systematic review and cost-effectiveness analysis. Health Technol Assess. 2011;15:1-74. On the other hand, the improvement described by Keating et al. has not been confirmed in other studies;⁶6. Bhandari M, Einhorn TA, et al., HEALTH Investigators. Total hip arthroplasty or hemiarthroplasty for hip fracture. N Engl J Med. 2019;381:2199-208. hence, in our study, the same utilities were assumed in both options.¹⁵15. Garcia-Perez L, Ramos-Garcia V, Serrano-Aguilar P, et al. EQ-5D-5 L utilities per health states in Spanish population with knee or hip osteoarthritis. Health Qual Life Outcomes. 2019;17:164. In the aforementioned studies, the great difference in utility scores is a key factor in the ICUR for THA being below the €22,000 per QALY cut-off, and hence, this intervention being considered cost-effective.²⁶26. Keating JF, Grant A, Masson M, et al. Randomized comparison of reduction and fixation, bipolar hemiarthroplasty, and total hip arthroplasty Treatment of displaced intracapsular hip fractures in healthy older patients. J Bone Joint Surg Am. 2006;88:249-60.^,2727. Vallejo-Torres L, Garcia-Lorenzo B, Serrano-Aguilar P. Estimating a costeffectiveness threshold for the Spanish NHS. Health Econ. 2018;27:746-61. Notably, in another study that assessed the long-term functional capacity of patients who underwent one of these two surgical interventions,²⁸28. Tol MC, van den Bekerom MP, Sierevelt IN, et al. Hemiarthroplasty or total hip arthroplasty for the treatment of a displaced intracapsular fracture in active elderly patients: 12-year follow-up of randomised trial. Bone Jt J. 2017;99-B:250-4. there were no differences in the results at 12 years after surgery. Nonetheless, this study has been criticized for the methodology used to assess the functional status of patients, the lack of assessment before surgery and the fact that less than a quarter of the patients in both groups were alive at the end of the follow-up period.²⁹29. Abdel MP. Hemiarthroplasty and total hip replacement for displaced intracapsular fracture in active elderly patients did not differ for function at 12 years after surgery. J Bone Joint Surg Am. 2017;99:1942.

The observational design used in the study does not have the internal validity of clinical trials.¹¹11. Garrison LPJ, Neumann PJ, Erickson P, et al. Using real-world data for coverage and payment decisions: the ISPOR real-world data task force report. Value Health. 2007;10:326-35. Patient recruitment from databases that are representative of clinical practice can be seen as a limitation, given that the decision regarding type of surgery has been based on the judgement of different orthopaedic surgeons. On the other hand, seeking to support surgical decision making, observational studies that analyse real-world data are increasingly common, given their high external validity.¹⁸18. Mar J, Anton-Ladislao A, Ibarrondo O, et al. Cost-effectiveness analysis of laparoscopic versus open surgery in colon cancer. Surg Endosc. 2018;32:4912-22.^,3030. Mar J, Anton-Ladislao A, Ibarrondo O, et al. Stage- and age-adjusted costeffectiveness analysis of laparoscopic surgery in rectal cancer. Surg Endosc. 2020;34:1167-76. The current availability of information from electronic medical records presents an ideal opportunity for measuring the real effectiveness and cost of different treatments. Nonetheless, given the non-random design of the study, the clinical characteristics of the two groups differ due to the selection bias. To overcome this, the recommendations of expert groups were followed regarding the use of real-world data in economic assessments.¹¹11. Garrison LPJ, Neumann PJ, Erickson P, et al. Using real-world data for coverage and payment decisions: the ISPOR real-world data task force report. Value Health. 2007;10:326-35. This approach includes propensity score analysis to ensure that the observed baseline distribution of the covariates is similar in both groups. In our case, the potential bias was addressed using a genetic matching algorithm.¹⁹19. Kreif N, Grieve R, Radice R, et al. Methods for estimating subgroup effects in cost-effectiveness analyses that use observational data. Med Decis Making. 2012;32:750-63. Now that the electronic health records and administrative registries facilitate access to real data from health systems, it is essential to develop and apply procedures that overcome their weaknesses and improve the validity of results obtained from their analysis.¹²12. Berger ML, Dreyer N, Anderson F, et al. Prospective observational studies to assess comparative effectiveness: the ISPOR good research practices task force report. Value Health. 2012;15:217-30.

The main limitation of the study is the lack of information regarding utilities at the patient level. Given that the Basque Health Service does not systematically record utility scores for patients with hip prostheses, the data concerning utilities used for the calculation of QALYs was taken from a study that measured the quality of life of patients with hip prostheses.¹⁵15. Garcia-Perez L, Ramos-Garcia V, Serrano-Aguilar P, et al. EQ-5D-5 L utilities per health states in Spanish population with knee or hip osteoarthritis. Health Qual Life Outcomes. 2019;17:164. The same values were used in both groups of surgical patients, given that an international randomised controlled trial did not identify any significant difference in clinical improvement between THA and HA.⁶6. Bhandari M, Einhorn TA, et al., HEALTH Investigators. Total hip arthroplasty or hemiarthroplasty for hip fracture. N Engl J Med. 2019;381:2199-208. In the future, the systematic recording of patient-reported outcome measures in clinical databases will allow us to standardise the use of economic assessments with data from clinical practice and enable decisions to be informed by specific data from each healthcare system.

The conclusion of this cost-utility study is that subgroup analysis supports current daily clinical practice in displaced femoral neck fractures, namely, using partial hip replacement in most patients and reserving total hip replacement for younger patients. Further, this study opens the use of real-world data for the economic evaluation of surgical procedures.

Acknowledgements

We would like to acknowledge the help of Ideas Need Communicating Language Services in improving the use of English in the manuscript.

References

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