Variation in outcome and ranking of hospitals: an analysis from the Swedish knee arthroplasty register

Physical Function Following Total Knee Arthroplasty for Osteoarthritis: A Longitudinal Systematic Review With Meta-analysis

OBJECTIVES: To explore the extent of functional improvement following primary total knee arthroplasty for knee osteoarthritis and to compare the trajectories of self-reported and performance-based measures of physical function. DESIGN: Longitudinal systematic review with meta-analysis METHODS: We searched 3 electronic databases from January 2005 to February 2023 for longitudinal cohort studies involving adults with knee osteoarthritis undergoing primary total knee arthroplasty. Estimates of self-reported and performance-based physical function were extracted presurgery and up to 5 years postsurgery. Risk of bias was assessed using a 6-item checklist. Self-reported function scores were converted to a 0-100 scale (higher scores indicate worse function). Mixed models provided pooled estimates after excluding low-quality studies. RESULTS: Out of 230 relevant studies, 72 (n = 19 063) of high quality were included in meta-analyses. Self-reported function significantly improved from presurgery (55.6/100; 95% confidence interval [CI], 53.1 to 58.1) to 3-6 months postsurgery (21.1; 95% CI, 17.9 to 24.3; P<.001). A small decline in self-reported function occurred at 6-12 months (31.0; 95% CI, 25.8 to 36.2; P<.001), with no further change at 12-24 months (30.9; 95% CI, 23.2 to 38.6; P = .919). Performance-based measures exhibited variable trajectories, with most estimates indicating no clinically meaningful improvement following total knee arthroplasty. CONCLUSION: Total knee arthroplasty resulted in clinically meaningful improvements in self-reported function at 3-6 months postoperatively. There was some deterioration in function after 6 months, and at no other time point did the estimate reach a clinically important change. There was limited evidence of clinically meaningful improvements in performance-based measures of physical function at any time point. J Orthop Sports Phys Ther 2025;55(1):1-11. Epub 26 November 2024. doi:10.2519/jospt.2024.12570.

Stability of hospital quality indicators over time: A multi-year observational study of German hospital data

BACKGROUND

Retrospective hospital quality indicators can only be useful if they are trustworthy signals of current or future quality. Despite extensive longitudinal quality indicator data and many hospital quality public reporting initiatives, research on quality indicator stability over time is scarce and skepticism about their usefulness widespread.

OBJECTIVE

Based on aggregated, widely available hospital-level quality indicators, this paper sought to determine whether quality indicators are stable over time. Implications for health policy were drawn and the limited methodological foundation for stability assessments of hospital-level quality indicators enhanced.

METHODS

Two longitudinal datasets (self-reported and routine data), including all hospitals in Germany and covering the period from 2004 to 2017, were analysed. A logistic regression using Generalized Estimating Equations, a time-dependent, graphic quintile representation of risk-adjusted rates and Spearman's rank correlation coefficient were used.

RESULTS

For a total of eight German quality indicators significant stability over time was demonstrated. The probability of remaining in the best quality cluster in the future across all hospitals reached from 46.9% (CI: 42.4-51.6%) for hip replacement reoperations to 80.4% (CI: 76.4-83.8%) for decubitus. Furthermore, graphical descriptive analysis showed that the difference in adverse event rates for the 20% top performing compared to the 20% worst performing hospitals in the two following years is on average between 30% for stroke and AMI and 79% for decubitus. Stability over time has been shown to vary strongly between indicators and treatment areas.

CONCLUSION

Quality indicators were found to have sufficient stability over time for public reporting. Potentially, increasing case volumes per hospital, centralisation of medical services and minimum-quantity regulations may lead to more stable and reliable quality of care indicators. Finally, more robust policy interventions such as outcome-based payment, should only be applied to outcome indicators with a higher level of stability over time. This should be subject to future research.

Hospital variation in revision rates after primary knee arthroplasty was not explained by patient selection: baseline data from 1452 patients in the Danish prospective multicenter cohort study, SPARK

PURPOSE

Revision rates following primary knee arthroplasty vary by country, region and hospital. The SPARK study was initiated to compare primary surgery across three Danish regions with consistently different revision rates. The present study investigated whether the variations were associated with differences in the primary patient selection.

METHODS

A prospective observational cohort study included patients scheduled Sep 2016 Dec 2017 for primary knee arthroplasty (total, medial/lateral unicompartmental or patellofemoral) at three high-volume hospitals, representing regions with 2-year cumulative revision rates of 1, 2 and 5%, respectively. Hospitals were compared with respects to patient demographics, preoperative patient-reported outcome measures, motivations for surgery, implant selection, radiological osteoarthritis and the regional incidence of primary surgery. Statistical tests (parametric and non-parametric) comprised all three hospitals.

RESULTS

Baseline data was provided by 1452 patients (89% of included patients, 56% of available patients). Patients in Copenhagen (Herlev-Gentofte Hospital, high-revision) were older (68.6 ± 9 years) than those in low-revision hospitals (Aarhus 66.6 ± 10 y. and Aalborg (Farsø) 67.3 ± 9 y., p = 0.002). In Aalborg, patients who had higher Body Mass Index (mean 30.2 kg/m² versus 28.2 (Aarhus) and 28.7 kg/m² (Copenhagen), p < 0.001), were more likely to be male (56% versus 45 and 43%, respectively, p = 0.002), and exhibited fewer anxiety and depression symptoms (EQ-5D-5L) (24% versus 34 and 38%, p = 0.01). The preoperative Oxford Knee Score (23.3 ± 7), UCLA Activity Scale (4.7 ± 2), range of motion (Copenhagen Knee ROM Scale) and patient motivations were comparable across hospitals but varied with implant type. Radiological classification ≥ 2 was observed in 94% (Kellgren-Lawrence) and 67% (Ahlbäck) and was more frequent in Aarhus (low-revision) (p ≤ 0.02), where unicompartmental implants were utilized most (49% versus 14 (Aalborg) and 23% (Copenhagen), p < 0.001). In the Capital Region (Copenhagen), the incidence of surgery was 15-28% higher (p < 0.001).

CONCLUSION

Patient-reported outcome measures prior to primary knee arthroplasty were comparable across hospitals with differing revision rates. While radiographic classifications and surgical incidence indicated higher thresholds for primary surgery in one low-revision hospital, most variations in patient and implant selection were contrary to well-known revision risk factors, suggesting that patient selection differences alone were unlikely to be responsible for the observed variation in revision rates across Danish hospitals.

LEVEL OF EVIDENCE

II, Prospective cohort study.

Patients in high- and low-revision hospitals have similar outcomes after primary knee arthroplasty: 1-year postoperative results from the Danish prospective multicenter cohort study, SPARK

PURPOSE

It is well-known that revision rates after primary knee arthroplasty vary widely. However, it is uncertain whether hospital revision rates are reliable indicators of general surgical quality as defined by patients. The SPARK study compared primary knee arthroplasty surgery at three high-volume hospitals whose revision rates differed for unknown reasons.

METHODS

This prospective observational study included primary knee arthroplasty patients (total, medial/lateral unicompartmental and patellofemoral) in two low-revision hospitals (Aarhus University Hospital and Aalborg University Hospital Farsø) and one high-revision hospital (Copenhagen University Hospital Herlev-Gentofte). Patients were followed from preoperatively (2016-17) to 1-year postoperatively with patient-reported outcome measures including Oxford Knee Score (OKS), EQ-5D-5L and Copenhagen Knee ROM (range of motion) Scale. The surgical outcomes were compared across hospitals for patients with comparable grades of radiographic knee osteoarthritis and preoperative OKS. Statistical comparisons (parametric and non-parametric) included all three hospitals.

RESULTS

97% of the 1452 patients who provided baseline data (89% of those included and 56% of those operated) responded postoperatively (90% at 1 year). Hospitals' utilization of unicompartmental knee arthroplasties differed (Aarhus 49%, Aalborg 14%, and Copenhagen 22%, p < 0.001). 28 patients had revision surgery during the first year (hospital independent, p = 0.1) and were subsequently excluded. 1-year OKS (39 ± 7) was independent of hospital (p = 0.1), even when adjusted for age, sex, Body Mass Index, baseline OKS and osteoarthritis grading. 15% of patients improved less than Minimal Important Change (8 OKS) (Aarhus 19%, Aalborg 13% and Copenhagen 14%, p = 0.051 unadjusted). Patients with comparable preoperative OKS or osteoarthritis grading had similar 1-year results across hospitals (OKS and willingness to repeat surgery, p ≥ 0.087) except for the 64 patients with Kellgren-Lawrence grade-4 (Aarhus 4-6 OKS points lower). 86% of patients were satisfied, and 92% were "willing to repeat surgery", independent of hospital (p ≥ 0.1). Hospital revision rates differences diminished during the study period.

CONCLUSIONS

Patients in hospitals with a history of differing revision rates had comparable patient-reported outcomes 1 year after primary knee arthroplasty, supporting that surgical quality should not be evaluated by revision rates alone. Future studies should explore if revision rate variations may depend as much on revision thresholds and indications as on outcomes of primary surgery.

LEVEL OF EVIDENCE

Level II (Prospective cohort study).

Ranking hospitals: do we gain reliability by using composite rather than individual indicators?

Background

Despite widespread use of quality indicators, it remains unclear to what extent they can reliably distinguish hospitals on true differences in performance. Rankability measures what part of variation in performance reflects ‘true’ hospital differences in outcomes versus random noise.

Objective

This study sought to assess whether combining data into composites or including data from multiple years improves the reliability of ranking quality indicators for hospital care.

Methods

Using the Dutch National Medical Registration (2007–2012) for stroke, colorectal carcinoma, heart failure, acute myocardial infarction and total hiparthroplasty (THA)/ total knee arthroplasty (TKA) in osteoarthritis (OA), we calculated the rankability for in-hospital mortality, 30-day acute readmission and prolonged length of stay (LOS) for single years and 3-year periods and for a dichotomous and ordinal composite measure in which mortality, readmission and prolonged LOS were combined. Rankability, defined as (between-hospital variation/between-hospital+within hospital variation)×100% is classified as low (<50%), moderate (50%–75%) and high (>75%).

Results

Admissions from 555 053 patients treated in 95 hospitals were included. The rankability for mortality was generally low or moderate, varying from less than 1% for patients with OA undergoing THA/TKA in 2011 to 71% for stroke in 2010. Rankability for acute readmission was low, except for acute myocardial infarction in 2009 (51%) and 2012 (62%). Rankability for prolonged LOS was at least moderate. Combining multiple years improved rankability but still remained low in eight cases for both mortality and acute readmission. Combining the individual indicators into the dichotomous composite, all diagnoses had at least moderate rankability (range: 51%–96%). For the ordinal composite, only heart failure had low rankability (46% in 2008) (range: 46%–95%).

Conclusion

Combining multiple years or into multiple indicators results in more reliable ranking of hospitals, particularly compared with mortality and acute readmission in single years, thereby improving the ability to detect true hospital differences. The composite measures provide more information and more reliable rankings than combining multiple years of individual indicators.

Hospital variation in allogeneic transfusion and extended length of stay in primary elective hip and knee arthroplasty: a cross-sectional study

OBJECTIVES

Outcomes in total hip and knee arthroplasty (THA and TKA), such as allogeneic transfusions or extended length of stay (LoS), can be used to compare the performance of hospitals. However, there is much variation in these outcomes. This study aims to rank hospitals and to assess hospital differences of two outcomes in THA and TKA: allogeneic transfusions and extended LoS, and to additionally identify factors associated with these differences.

DESIGN

Cross-sectional medical record review study.

SETTING

Data were gathered in 23 Dutch hospitals.

PARTICIPANTS

1163 THA and 986 TKA patient admissions.

OUTCOMES

Hospitals were ranked based on their observed/expected (O/E) ratios regarding allogeneic transfusion and extended LoS percentages (extended LoS was defined by postoperative stay >4 days). To assess the reliability of these rankings, we calculated which percentage of the existing variation was based on differences between hospitals as compared with random variation (after adjustment for variation in patient characteristics). Associations between hospital-specific factors and O/E ratios were used to explore potential sources of differences.

RESULTS

The variation in O/E ratios between hospitals ranged from 0 to 4.4 for allogeneic transfusion, and from 0.08 to 2.7 for extended LoS. Variation in transfusion could in 21% be explained by hospital differences in THA and 34% in TKA. For extended LoS this was 71% in THA and 78% in TKA. Better performance (low O/E ratios) in transfusion was associated with more frequent tranexamic acid (TXA) use in TKA (R=-0.43, p=0.04). Better performance in extended LoS was associated with more frequent TXA use in THA (R=-0.45, p=0.03) and TKA (R=-0.65, p<0.001) and local infiltration analgesia (LIA) in TKA (R=-0.60, p=0.002).

CONCLUSIONS

Ranking hospitals based on allogeneic transfusion is unreliable due to small percentages of variation explained by hospital differences. Ranking based on extended LoS is more reliable. Hospitals using TXA and LIA have relatively fewer patients with transfusions and extended LoS.

Hospital quality variation matters - A time-trend and cross-section analysis of outcomes in German hospitals from 2006 to 2014

Awareness of care variation and associated differences in outcome quality is important for patients to recognize and leverage the benefits of hospital choice and for policy makers, providers, and suppliers to adapt initiatives to improve hospital quality of care. We examine panel data on outcome quality in German hospitals between 2006 and 2014 for cholecystectomy, pacemaker implantation, hip replacement, percutaneous coronary intervention (PCI), stroke, and acute myocardial infarction (AMI). We use risk-adjusted and unadjusted outcomes based on 16 indicators. Median outcome and outcome variation trends are examined via box plots, simple linear regressions and quintile differences. Outcome trends differ across treatment areas and indicators. We found positive quality trends for hip replacement surgery, stroke and AMI 30-day mortality, and negative quality trends for 90-day stroke and AMI readmissions and PCI inpatient mortality. Variation of risk-adjusted outcomes ranges by a factor of 3-12 between the 2nd and 5th quintile of hospitals, both at the national and regional level. Our results show that simply measuring and reporting hospital outcomes without clear incentives or regulation - "carrots and sticks" - to improve performance and to centralize care in high performing hospitals has not led to broad quality improvements. More substantial efforts must be undertaken to narrow the outcome spread between high- and low-quality hospitals.

Annual revision rates of partial versus total knee arthroplasty: A comparative meta-analysis

BACKGROUND

Utilization of unicompartmental knee arthroplasty (UKA) and patellofemoral arthroplasty (PFA) as alternatives to total knee arthroplasty (TKA) for unicompartmental knee osteoarthritis (OA) has increased. However, no single resource consolidates survivorship data between TKA and partial resurfacing options for each variant of unicompartmental OA. This meta-analysis compared survivorship between TKA and medial UKA (MUKA), lateral UKA (LUKA) and PFA using annual revision rate as a standardized metric.

METHODS

A systematic literature search was performed for studies quantifying TKA, MUKA, LUKA and/or PFA implant survivorship. Studies were classified by evidence level and assessed for bias using the MINORS and PEDro instruments. Annual revision rates were calculated for each arthroplasty procedure as percentages/observed component-year, based on a Poisson-normal model with random effects using the R-statistical software package.

RESULTS

One hundred and twenty-four studies (113 cohort and 11 registry-based studies) met inclusion/exclusion criteria, providing data for 374,934 arthroplasties and 14,991 revisions. The overall evidence level was low, with 96.7% of studies classified as level III-IV. Annual revision rates were lowest for TKA (0.49%, CI 0.41 to 0.58), followed by MUKA (1.07%, CI 0.87 to 1.31), LUKA (1.13%, CI 0.69 to 1.83) and PFA (1.75%, CI 1.19 to 2.57). No difference was detected between revision rates for MUKA and LUKA (p=0.222).

CONCLUSIONS

Revisions of MUKA, LUKA and PFA occur at an annual rate of 2.18, 2.31 and 3.57-fold that of TKA, respectively. These estimates may be used to inform clinical decision-making, guide patient expectations and evaluate the cost-effectiveness of total versus partial knee replacement in the setting of unicompartmental OA.

Statistical analysis of arthroplasty data. II. Guidelines

It is envisaged that guidelines for statistical analysis and presentation of results will improve the quality and value of research. The Nordic Arthroplasty Register Association (NARA) has therefore developed guidelines for the statistical analysis of arthroplasty register data. The guidelines are divided into two parts, one with an introduction and a discussion of the background to the guidelines (Ranstam et al. 2011a, see pages x-y in this issue), and this one with a more technical statistical discussion on how specific problems can be handled. This second part contains (1) recommendations for the interpretation of methods used to calculate survival, (2) recommendations on howto deal with bilateral observations, and (3) a discussion of problems and pitfalls associated with analysis of factors that influence survival or comparisons between outcomes extracted from different hospitals.

Performance evaluations and league tables: do they capture variation between organizational units? An analysis of 5 Swedish pharmacological performance indicators

BACKGROUND

The use of league tables during the last decade has frequently been employed to assess quality in health care. However, few studies have attempted to assess quality by quantifying the variability across the organizational units or attempted to investigate whether the units are the correct context that really influences the outcome under study.

OBJECTIVES

To quantify the variation between different organizational units regarding 5 different Swedish national pharmacological performance indicators and to examine whether the organizational units under study are a valid construct of the context that influences the specific outcome.

RESEARCH DESIGN

A multilevel model with patients nested within health care units that in turn were nested within County councils was used. By using measures of variance (intraclass correlation [ICC]), we quantified the extent to which the 5 indicators of health care quality were conditioned by the specified units.

RESULTS

For all 5 studied indicators, the variation between county councils was small (ICC ranged from 2% to 7%), whereas the variation among health care units seemed to be more important (ICC ranged from 20% to 40%).

CONCLUSION

As the variation between county councils was small, using league tables for performance evaluation seems to be inappropriate. If league tables are to be presented, the relative size of the variation at the higher levels and an analysis regarding the possible influence of the context for the specific outcome should be included. This approach provides useful information for identifying relevant contexts to capture health care variation.

Fluid pressure and flow as a cause of bone resorption

BACKGROUND

Unstable implants in bone become surrounded by an osteolytic zone. This is seen around loose screws, for example, but may also contribute to prosthetic loosening. Previous animal studies have shown that such zones can be induced by fluctuations in fluid pressure or flow, caused by implant instability.

METHOD

To understand the roles of pressure and flow, we describe the 3-dimensional distribution of osteolytic lesions in response to fluid pressure and flow in a previously reported rat model of aseptic loosening. 50 rats had a piston inserted in the proximal tibia, designed to produce 20 local spikes in fluid pressure of a clinically relevant magnitude (700 mmHg) twice a day. The spikes lasted for about 0.3 seconds. After 2 weeks, the pressure was measured in vivo, and the osteolytic lesions induced were studied using micro-CT scans.

RESULTS

Most bone resorption occurred at pre-existing cavities within the bone in the periphery around the pressurized region, and not under the piston. This region is likely to have a higher fluid flow and less pressure than the area just beneath the piston. The velocity of fluid flow was estimated to be very high (roughly 20 mm/s).

INTERPRETATION

The localization of the resorptive lesions suggests that high-velocity fluid flow is important for bone resorption induced by instability.

Statistical analysis of arthroplasty register data

Data from arthroplasty registers are often analyzed using survival methods. Several methodological problems exist, for example relating to competing events, non-random censoring, non-proportional hazards and dependent observations. League tables and ranking of specific survival results leds to further methodological difficulties. Most of these problems are, however, well known and a number of methods for dealing successfully with the problems have been developed. These methods are usually accessible in commercially available statistical software packages. The statistical analysis and reporting of data from arthroplasty registers can thus be improved. Development of arthroplasty register guidelines for statistical analysis could play an important role in making these registers even more useful.

Health-care quality registers: outcome-orientated ranking of hospitals is unreliable

Public disclosure of outcome-orientated ranking of hospitals is becoming increasingly popular and is routinely used by Swedish health-care authorities. Whereas uncertainty about an outcome is usually presented with 95% confidence intervals, ranking's based on the same outcome are typically presented without any concern for bias or statistical precision. In order to study the effect of incomplete registration of re-operation on hospital ranking we performed a simulation study using published data on the two-year risk of re-operation after total hip replacement. This showed that whereas minor registration incompleteness has little effect on the observed risk of revision, it can lead to major errors in the ranking of hospitals. We doubt whether a level of data entry sufficient to generate a correct ranking can be achieved, and recommend that when ranking hospitals, the uncertainties about data quality and random events should be clearly described as an integral part of the results.