Elicit: Predicting Day-Case Arthroplasty Outcomes
Predicting Day-Case Arthroplasty Outcomes
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August 7, 2025
Which patient factors best predict success/failure of day-case arthroplasty?
Increased age, female sex (OR 1.63-4.22), high ASA classification, and multiple comorbidities (OR up to 3.9) are the primary predictors of day-case arthroplasty failure.
Abstract
Day‐case arthroplasty outcomes are influenced by clear patient factors. Studies report that increased age—which in over 20 analyses shows odds ratios from 1.01 to 4.16—and female sex—with odds ratios from 1.63 to 4.22 in more than 15 investigations—predict lower same‐day discharge success. A higher body mass index (supported in 10+ studies) and non‐white race (noted in 5+ studies) similarly relate to reduced success. In addition, clinical indicators such as an ASA classification of III or IV and a comorbidity burden of three or more conditions consistently predict failure, with odds ratios up to 3.9 and highly significant p‐values. Other conditions, including hypertension, diabetes, cardiovascular disease, and chronic obstructive pulmonary disease, are also cited as contributing to poor day‐case outcomes. Although a couple of studies flag younger age (<40) as a potential risk factor, this finding remains inconsistent.
Methods
We analyzed 40 sources from an initial pool of 500, using 8 screening criteria. Each paper was reviewed for 6 key aspects that mattered most to the research question. More on methods
Papers identified with Elicit search
n = 500
Papers screened using: Study Setting, Patient Population - Age, Procedure Type, Clinical Context, Predictive Factors, Outcome Measures, Study Design, Study Focus
n = 500
Papers screened out
n = 460
Papers included for extraction
n = 40
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Paper search
Using your research question “Which patient factors best predict success/failure of day-case arthroplasty?”, we searched across over 126 million academic papers from the Semantic Scholar corpus. We retrieved the 500 papers most relevant to the query.
Screening
We screened in sources based on their abstracts that met these criteria:
- Study Setting: Does the study investigate outpatient/day-case/ambulatory arthroplasty procedures?
- Patient Population - Age: Does the study include only adult patients (≥18 years)?
- Procedure Type: Does the study examine primary (non-revision) hip, knee, shoulder, or ankle arthroplasty?
- Clinical Context: Does the study examine planned elective procedures (not emergency or trauma-related cases)?
- Predictive Factors: Does the study analyze patient-related predictive factors (such as age, BMI, comorbidities, or social support)?
- Outcome Measures: Does the study report specific outcomes related to success/failure of day-case surgery (such as same-day discharge, unplanned overnight stays, or 30-day readmissions)?
- Study Design: Is the study design either a prospective/retrospective cohort study, case-control study, RCT, or systematic review with 10 or more patients?
- Study Focus: Does the study include patient-related factors (not exclusively focusing on surgical technique, anesthetic protocol, or hospital/surgeon factors)?
We considered all screening questions together and made a holistic judgement about whether to screen in each paper.
Data extraction
We asked a large language model to extract each data column below from each paper. We gave the model the extraction instructions shown below for each column.
- Study Design:
Identify the specific type of study design used:
- Specify whether it is retrospective, prospective, or cross-sectional
- Note if it is a single-center or multi-center study
- If multiple study designs are present, list all and indicate which is the primary design
Look in the methods section for explicit statements about study design. If the design is not clearly stated, carefully review the methodology description to determine the most appropriate classification. If uncertain, note “unclear” and provide a brief explanation.
- Patient Selection Criteria:
Extract the specific inclusion and exclusion criteria used for patient selection:
- List all explicit inclusion criteria (e.g., age range, type of arthroplasty, patient health status)
- List all explicit exclusion criteria
- Note any specific screening or eligibility assessment methods
Locate this information in the methods section. If criteria are not fully detailed, extract all available information. If partial or no criteria are provided, note “insufficient information” and quote any relevant text describing patient selection.
- Patient Demographic and Clinical Factors:
Extract key patient characteristics that could predict day-case arthroplasty success:
- Age (mean and range)
- Gender distribution
- Body Mass Index (if reported)
- Comorbidities (e.g., Charnley class, ASA score)
- Previous joint surgeries
- Preoperative medication use
Locate this information in the patient characteristics section or baseline demographics table. If data is presented in multiple formats, prioritize mean/median values with standard deviation or confidence intervals. If specific factors are not fully reported, note which specific characteristics are missing.
- Reasons for Same-Day Discharge Failure:
List all documented reasons for unsuccessful same-day discharge:
- Rank reasons by frequency if provided
- Extract specific percentages or proportions for each reason
- Include both clinical and procedural reasons for failure
Search results and discussion sections for explicit statements about discharge failure reasons. If reasons are not comprehensively listed, extract all available information. Ensure to differentiate between reasons for different types of arthroplasty (THA, TKA, mUKA) if such distinctions are made.
- Predictive Factors for Same-Day Discharge Success:
Extract statistical predictors of same-day discharge success:
- List all statistically significant factors
- Record odds ratios, confidence intervals, and p-values
- Distinguish between factors that increase or decrease likelihood of successful discharge
Prioritize information from multivariable regression analyses in the results section. If multiple analyses are present, extract results from the most comprehensive analysis. If predictive factors are not statistically analyzed, note “no statistical analysis of predictive factors” and extract any descriptive observations.
- Surgical Procedure Details:
Extract specific details about surgical procedures:
- Types of arthroplasty performed (THA, TKA, mUKA)
- Surgical timing (e.g., surgery start time)
- Anesthesia type
- Surgical duration
Locate this information in methods and results sections. If details vary between procedure types, create separate entries for each. If specific details are inconsistently or partially reported, extract all available information and note any limitations.
Results
Characteristics of Included Studies
Study
Study Design
Sample Size
Setting Type
Primary Outcome Definition
Full text retrieved
Velichala et al., 2024
Retrospective
31,347
No mention found
30-day readmission after outpatient Total Knee Arthroplasty (TKA)
No
Murrell et al., 2023
Retrospective, single-center
606
Single-center
24-hour discharge after elective hip/knee arthroplasty
Yes
Keulen et al., 2020
Retrospective
525
No mention found
Same-day discharge after outpatient hip/knee arthroplasty
No
Foley et al., 2023
Retrospective analysis of prospectively collected data, single-center
466
Single-center
Failure to achieve planned same-day discharge after Total Joint Arthroplasty (TJA)
No
Sher et al., 2017
Retrospective, multi-center
120,847
Multi-center
Same-day discharge and post-discharge complications after TJA
No
Radtke et al., 2024
Retrospective, single-center
3,093
Single-center
Failure to launch (discharge home) after scheduled same-day discharge TJA
No
Danielsen et al., 2024
Prospective, multicentre cohort
6,142
Multicenter
Day-case success after Total Hip Arthroplasty (THA), TKA, Medial Unicompartmental Knee Arthroplasty (mUKA)
Yes
Gong et al., 2023
Retrospective, single-center
753
Single-center
Reasons/risk factors for failed same-day discharge after TKA/THA
No
Kort et al., 2017
Review
14 studies
N/A
Patient selection criteria for outpatient joint arthroplasty
No
Jaibaji et al., 2020
Systematic review
6,519
N/A
Complication/reoperation rates after outpatient arthroplasty
No
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Study Design:
- 30 retrospective studies
- 4 prospective studies
- 5 systematic reviews (including meta-analyses)
- 1 review
Setting Type:
- 17 studies in single-center settings
- 10 studies in multi-center settings
- No mention found for 9 studies
- 5 reviews or systematic reviews without a setting
Sample Size:
- 1 study with fewer than 100 participants
- 10 studies with 100–500 participants
- 4 studies with 500–1,000 participants
- 15 studies with 1,000–10,000 participants
- 7 studies with more than 10,000 participants
- No mention found for 3 studies (excluding reviews and systematic reviews, which reported number of studies rather than participants)
Primary Outcome Category:
- 25 studies focused on same-day discharge (SDD) or day-case success/failure
- 11 studies focused on complications, readmission, or reoperation
- 17 studies focused on predictors or risk factors (for same-day discharge, length of stay, etc.)
- 7 studies focused on other outcomes such as patient selection, safety, or general outcomes
Some studies addressed more than one outcome category. We did not find detailed outcome definitions for all studies, but most focused on same-day discharge, complications/readmission, or predictors.
Effects
Patient Demographics
Factor
Effect Size Range
Direction of Effect
Number of Supporting Studies
Age (older)
Odds Ratio (OR) 1.01–4.16, Relative Risk (RR) 1.44, OR 0.935 (inverse)
Decreases same-day discharge success
20+
Female sex
OR 1.63–4.22, RR 2.76
Decreases same-day discharge success
15+
Body Mass Index (higher)
OR 1.06, OR 0.491 (inverse)
Decreases same-day discharge success
10+
Non-white race
OR 1.31–2.19, OR 0.456 (inverse)
Decreases same-day discharge success
5+
Marital status (non-married)
p=0.007
Decreases same-day discharge success
2
Younger age (<40)
Increased risk in some studies
Decreases same-day discharge success (inconsistently)
2
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Key findings from these studies:
- Older age:Supported by more than 20 studies as decreasing the likelihood of same-day discharge success.
- Female sex:Supported by more than 15 studies as decreasing same-day discharge success.
- Higher body mass index:Supported by more than 10 studies as decreasing same-day discharge success.
- Non-white race:Supported by more than 5 studies as decreasing same-day discharge success.
- Non-married marital status:Supported by 2 studies as decreasing same-day discharge success.
- Younger age (<40):Reported in 2 studies as decreasing same-day discharge success, but this finding was inconsistent.
For most factors, the direction of effect was consistent (decreased same-day discharge success), except for younger age, where results were inconsistent. Odds ratios were the most commonly reported effect size, with some studies also reporting relative risks or p-values. We did not find standardized effect size reporting for all factors in the available abstracts or full texts, and some effect sizes were only described narratively.
Clinical Characteristics
Factor
Effect Size/Statistical Significance
Direction of Effect
Number of Supporting Studies
American Society of Anesthesiologists (ASA) class III/IV
OR 1.42–3.9, OR 0.378 (inverse)
Decreases same-day discharge success
15+
Comorbidity burden (≥3)
OR 0.507 (inverse), p<0.001
Decreases same-day discharge success
10+
Hypertension
OR 1.11–2.5, RR 2.5
Decreases same-day discharge success
8+
Diabetes
OR 1.25–4.06
Decreases same-day discharge success
7+
Cardiovascular disease
OR 1.67–12.06
Decreases same-day discharge success
6+
Chronic Obstructive Pulmonary Disease (COPD)
OR 1.30–2.4
Decreases same-day discharge success
6+
Bleeding disorders
OR 1.32–2.56
Decreases same-day discharge success
5+
Poor functional status
p<0.001
Decreases same-day discharge success
4+
Preoperative opioid use
OR 1.82, p=0.046
Decreases same-day discharge success
3+
Multiple allergies
p<0.001
Decreases same-day discharge success
2+
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Summary of findings:
- All 11 patient factors listed above were associated with decreased same-day discharge success.
- The most frequently supported factors were higher ASA class (15+ studies), greater comorbidity burden (10+ studies), hypertension (8+ studies), diabetes (7+ studies), and cardiovascular disease (6+ studies).
- All reported effect sizes and statistical significance values indicated a negative impact on same-day discharge success for these factors.
- We did not find mention of any factors in this table that were associated with increased same-day discharge success, nor did we find inconsistent or positive associations.
Perioperative Factors
Factor
Effect Size/Statistical Significance
Direction of Effect
Number of Supporting Studies
Later surgical start time
OR 1.22–6.03, p<0.001
Decreases same-day discharge success
8+
General anesthesia (vs. spinal)
p<0.0001
Decreases same-day discharge success
3+
Longer surgical/anesthesia duration
OR 1.04, OR 4.28 per 30 min, p<0.001
Decreases same-day discharge success
10+
Higher blood loss
p<0.0001
Decreases same-day discharge success
2+
Not ambulating on day of surgery
OR 3.9–4.09, p<0.001
Decreases same-day discharge success
3+
Not receiving preoperative nerve block (Total Knee Arthroplasty)
Associated with failure
Decreases same-day discharge success
1
Higher postoperative pain
OR 1.93–5.85
Decreases same-day discharge success
2+
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Key findings:
- Longer surgical or anesthesia duration:Most frequently supported, with more than 10 studies reporting a negative association with same-day discharge success.
- Later surgical start time:Reported in more than 8 studies as decreasing same-day discharge success.
- General anesthesia (compared to spinal):Associated with decreased same-day discharge success in more than 3 studies.
- Not ambulating on the day of surgery:Reported in more than 3 studies as decreasing same-day discharge success.
- Higher intraoperative blood loss:Associated with decreased same-day discharge success in more than 2 studies.
- Higher postoperative pain:Reported in more than 2 studies as decreasing same-day discharge success.
- Not receiving a preoperative nerve block (in Total Knee Arthroplasty):Associated with decreased same-day discharge success in 1 study.
All reported effect sizes and statistical significance values indicated a negative impact on same-day discharge success for these factors. We did not find mention of any factors in this table that were associated with increased same-day discharge success.
Success Rates and Risk Patterns
Overall Success Rates
Study
Same-Day Discharge Success Rate
Notes
Velichala et al., 2024
98.14% (1.86% readmission)
Outpatient Total Knee Arthroplasty
Murrell et al., 2023
7.4% (<24h discharge)
Elective hip/knee arthroplasty
Keulen et al., 2020
79%
Outpatient hip/knee arthroplasty
Foley et al., 2023
99.7% (Ambulatory Surgery Center), 66.7% (hospital)
Total Joint Arthroplasty
Danielsen et al., 2024
59–72% (eligible, by procedure)
Total Hip Arthroplasty, Total Knee Arthroplasty, Medial Unicompartmental Knee Arthroplasty
Bayoumi et al., 2022
88% (Unicompartmental Knee Arthroplasty)
Systematic review
French et al., 2024
85% (overall)
Systematic review
Delfosse et al., 2024
97.2%
High-volume center
Others
74–93%
Varies by procedure, setting
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Distribution of same-day discharge success rates:
- 3 studies reported same-day discharge success rates ≥95%
- 3 studies reported rates between 80–94%
- 4 studies reported rates between 60–79%
- 2 studies reported rates <60%
Procedure type:
- 3 studies reported on Total Knee Arthroplasty
- 1 study reported on Total Hip Arthroplasty
- 2 studies reported on Unicompartmental or Medial Unicompartmental Knee Arthroplasty
- 1 study reported on Total Joint Arthroplasty
- 2 studies reported on hip/knee arthroplasty without further specification
- We didn’t find mention of procedure details for 2 studies
Setting:
- 3 studies reported on outpatient or Ambulatory Surgery Center settings
- 1 study reported on a hospital setting
- 1 study reported on a high-volume center
- We didn’t find mention of setting details for 4 studies
We didn’t find mention of same-day discharge success rates that were not directly comparable across studies; all studies reported either same-day discharge or eligibility rates.
Common Failure Patterns
Study
Most Common Reasons for Failure
Frequency/Proportion
Danielsen et al., 2024
Mobilization issues, prolonged spinal anesthesia, postoperative nausea and vomiting (PONV)
9–14% by reason
Gong et al., 2023
Failure to clear Physical Therapy, hypotension, urinary retention
33%, 20.5%, 16.9%
Bayoumi et al., 2022
Inability to mobilize, pain, nausea/vomiting
34%, 8%, 11%
Lieberman et al., 2021
Hypotension, delayed spinal anesthesia, nausea
24.4%, 24.4%, 11.1%
Vermaak et al., 2024
Mobilization, nausea/vomiting, social issues
16, 14, 11 cases
Delfosse et al., 2024
Urinary retention, orthostatic hypotension, pain
28.6%, 28.6%, 14.3%
Fraser et al., 2018
Patient preference, dizziness/hypotension, Physical Therapy
12, 8, 5 cases
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Most common reasons for failure (number of studies in which each reason was cited):
- Hypotension (including orthostatic and dizziness/hypotension):4 studies
- Nausea/vomiting (including postoperative nausea and vomiting):4 studies
- Mobilization issues (including inability to mobilize):3 studies
- Urinary retention:2 studies
- Pain:2 studies
- Physical Therapy issues:2 studies
- Prolonged or delayed spinal anesthesia:2 studies
- Social issues:1 study
- Patient preference:1 study
Frequency/proportion reporting:
- Frequencies were reported as percentages in 5 studies and as case counts in 2 studies.
- We didn’t find frequency/proportion data in a consistent format across all studies.
- We didn’t find mention of other reasons for failure in these studies.
Risk Stratification Models
Study
Model/Tool
Predictive Value
Notes
Meneghini et al., 2017
Outpatient Arthroplasty Risk Assessment (OARA) score
OR 2.0–2.7 for early discharge
More predictive than American Society of Anesthesiologists (ASA)/Charlson Comorbidity Index (CCI)
Crawford et al., 2022
OARA score
Accurate for same-day discharge, poor for failure
May be too restrictive
Goltz et al., 2021
13-variable model
Area Under the Curve (AUC) 0.762
Shoulder arthroplasty
Turcotte et al., 2021
Logistic regression
AUC 0.773
Total Knee Arthroplasty
Wei et al., 2021
Artificial Neural Network (ANN) model
AUC 0.801
Total Knee Arthroplasty
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Summary of findings:
- Model/Tool types:
- OARA score was used in 2 studies.
- 13-variable model, logistic regression, and Artificial Neural Network model were each used in 1 study.
- Predictive Value metrics:
- 3 studies reported Area Under the Curve values (0.762, 0.773, and 0.801).
- 1 study reported an odds ratio (2.0–2.7 for early discharge).
- 1 study provided a qualitative assessment of accuracy (accurate for same-day discharge, poor for failure).
- Model comparisons and limitations:
- 1 study found OARA more predictive than ASA/Charlson Comorbidity Index.
- 1 study noted that OARA may be too restrictive.
- Procedure types:
- 2 studies focused on Total Knee Arthroplasty, and 1 on shoulder arthroplasty; we didn’t find mention of procedure information for the other 2 studies.
We didn’t find mention of Area Under the Curve or odds ratio values for 1 study, which instead described predictive value qualitatively.
References
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August 7, 2025 11:20 AM
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500 sources found
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40 sources included
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Extract data
240 data points extracted
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Successful same-day discharge in 88% of patients after unicompartmental knee arthroplasty: a systematic review and meta-analysis
T. Bayoumi, J. P. van der List, L. Ruderman, H. Zuiderbaan, G. Kerkhoffs, A. Pearle
Knee Surgery, Sports Traumatology, Arthroscopy·
2022·
13 citations
SourceDOI
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Study Design
Systematic review with meta-analysis; Multi-center study
Patient Selection Criteria
- Inclusion criteria: UKA performed as day-case procedure, reporting of successful SDD, complication, readmission, or reoperation rates, minimum 30-days follow-up. - Exclusion criteria: revision procedures or simultaneous bilateral cases, studies not reporting outcomes separately, cohorts with incidental SDD, publications based on the same cohort or database. - Specific screening or eligibility assessment methods: Not fully detailed; some studies report criteria such as ASA score, age, BMI, and social environment.
Patient Demographic and Clinical Factors
- Age: Mean 66 years (SD 9) - Gender distribution: 61% female - Body Mass Index: Mean 29 (SD 5) - Comorbidities: 85% ASA 1-2 - Previous joint surgeries: Not mentioned - Preoperative medication use: Not mentioned
Reasons for Same-Day Discharge Failure
- Inability to mobilize: 34% - Pain control: 8% - Nausea and vomiting: 11% - Logistical issues: 8% - Wound issues: 8% - Urinary retention: 3% - Patient confidence or social environment: 10% - Other: 19%
Predictive Factors for Same-Day Discharge Success
no statistical analysis of predictive factors; descriptive observations include inability to mobilize, nausea, uncontrolled pain, lack of patient confidence, logistical issues, older age, female gender, higher ASA scores as factors associated with failed SDD
Surgical Procedure Details
- Types of arthroplasty performed: Unicompartmental knee arthroplasty (UKA) - Surgical timing: Not explicitly mentioned - Anesthesia type: General anesthesia (GA) and regional anesthesia (RA) - Surgical duration: Not explicitly mentioned
PURPOSE
The purpose of this study was to evaluate the effectiveness of day-case unicompartmental knee arthroplasty (UKA) by assessment of successful same-day discharge (SDD), readmission, complication and reoperation rates in the recent literature.
METHODS
For this systematic review and meta-analysis, PubMed, Embase and Cochrane Library were comprehensively searched to identify all eligible studies reporting outcomes of day-case UKA. Studies with intended same-day home discharge after UKA were included. A meta-analysis of proportions, using a random-effects model, was performed to estimate overall rates of successful SDD and adverse events. Subgroup analyses were performed for studies including selected patients (i.e., patients had to meet certain patient-specific criteria to be eligible for day-case UKA) and unselected patients (i.e., no additional criteria for day-case UKA), as well as for clinical and registry-based studies. Additional outcomes included reasons for the failure of SDD and patient satisfaction.
RESULTS
A total of 29 studies and 9694 patients were included with a mean age of 66 ± 9 years and mean follow-up of 59 days (mean range 30-270 days). Based on 24 studies (2733 patients), the overall successful SDD rate was 88% (95% confidence interval [CI] 80-92). These rates were 91% (95% CI 84-95) across studies with selected patients and 76% (95% CI 55-89) across studies with unselected patients. Overall readmission, complication and reoperation rates were 3% (95% CI 1.9-4.4), 4% (95% CI 2.8-5.2) and 1% (95% CI 0.8-1.3), respectively. Inability to mobilize, nausea and uncontrolled pain were frequently reported reasons for failed SDD. The overall patient satisfaction rate was 94%.
CONCLUSION
This systematic review with meta-analysis found an overall successful SDD rate of 88% after UKA in a heterogeneous cohort of selected and unselected patients. Readmission, complication and reoperation rates suggest UKA can be performed safely and effectively as a same-day discharge procedure.
LEVEL OF EVIDENCE
Level IV, systematic review of level III and IV studies.
© 2022. The Author(s) under exclusive licence to European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).
Introduction
Unicompartmental knee arthroplasty (UKA) is a successful procedure for reducing pain and improving the function of patients with isolated compartment osteoarthritis of the knee [23,34]. The consistently growing demand for knee arthroplasty [37] and recent disruptions of elective orthopedic programs worldwide due to the Covid-19 pandemic [6] demonstrate a need for reorganization of clinical pathways in orthopedics.
Same-day discharge protocols or so-called day-case pathways are designed to discharge elective patients on the day of surgery and could allow for better resource allocation, improved quality of care, reduced costs and alleviation of a burden on healthcare systems [8,24,36]. Due to its minimally invasive character and potential for rapid recovery [34], UKA lends itself well to a day-case setting. Indeed, multiple studies have demonstrated satisfactory outcomes following day-case UKA, reporting high patient satisfaction and low complication rates [5,8,15,18]. Some systematic reviews have described successful outcomes following day-case hip and knee arthroplasty [3,19]. However, these reviews mostly present combined outcomes for joint arthroplasty or only a small, separate subset of UKA procedures. Considering the recent proportional growth of day-case UKA [16], a systematic review of successful sameday discharge (SDD), readmission and complication rates would be of interest to identify evidence with regard to the effectiveness and safety of this relatively new clinical pathway. Such an overview could facilitate surgeons in clinical and shared decision-making and serve as a supportive aid to provide realistic expectations for patients. Additionally, a better understanding of success rates and complications could help to further refine day-case pathways and promote a widespread practice.
The purpose of this systematic review and meta-analysis was to evaluate the effectiveness of day-case UKA and provide an overview of reported success, readmission, complication and reoperation rates. Based on prior reports [3,16], it was hypothesized that day-case UKA would yield high SDD rates with low readmission and complication rates.
Methods
This systematic review with meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement [33]. This systematic review was not registered.
Literature search
A systematic search of the literature was performed in the databases of PubMed, Embase and Cochrane library since inception. The last search was performed on June 18, 2022. Search algorithms were designed for each database to identify all relevant original clinical studies or registry studies reporting on clinical outcomes after day-case UKA. The algorithms included various combinations of key terms: "unicompartmental knee arthroplasty", "same-day discharge," "day-case," "outpatient surgery," "ambulant," "fast-track," and "enhanced recovery." The complete search strategy is provided in Appendix I. After combining search results and removing duplicates, studies were screened independently by two reviewers (TB and LR) by title and abstract. Eligible studies were evaluated for inclusion by full-text review according to the inclusion and exclusion criteria. References of included studies were screened for additional studies. Inclusion criteria consisted of: (I) UKA performed as day-case procedure (i.e., intended discharge on the day of surgery with a description of the day-case pathway, or registry-based studies compiled from such studies), (II) reporting of rates of successful SDD, complication, readmission or reoperation, and (III) a minimum 30-days follow-up for studies reporting complications, readmissions or reoperations. Studies were excluded if they: (I) included revision procedures or simultaneous bilateral cases, (II) did not report outcomes separately for the study arm of interest, (III) were based on cohorts with incidental SDD, or (IV) were publications based on the same cohort or database. Systematic reviews, case reports, commentary letters and abstracts were not considered. If publications were based on the same cohort or database, the largest study was selected for inclusion.
Methodological quality assessment
Methodological quality of studies was assessed by one reviewer (TB) using the Methodological Index for Non-Randomized Studies (MINORS) criteria [41]. Non-comparative studies were graded using the first 8 criteria and all 12 criteria were used to grade comparative studies. Level of evidence was determined for each study using the Oxford Centre for Evidence-Based Medicine [45].
Data extraction
Data were extracted and collected in a standardized format in Excel 2019 (Microsoft Corp) by one reviewer (TB). Data verification was performed on a random sample by a second reviewer (LR). First author, publication year, journal, study design, study period, follow-up, number of UKA daycases, clinical setting, type of UKA, anesthesia, selection criteria for day-case surgery, reasons for failed SDD and patient characteristics (gender, age, body mass index [BMI] and American Society of Anesthesiology [ASA] score) were recorded. Additionally, rates of successful SDD, readmission, complication, reoperation and patient satisfaction were extracted.
Statistical analyses
Proportions of successful SDD were calculated as the number of patients successfully discharged on the day of surgery, divided by the total number of day-case patients. Similarly, rates of readmission, complication and reoperation were calculated. A meta-analysis of proportions, a method that allows estimation of an overall proportion from studies reporting a single proportion, was used to combine proportional outcomes across studies. To allow for variance stabilization and an accurate estimate of summary proportions, a logit transformation was first applied to the observed proportions [26]. Studies containing proportions equal to zero were augmented with 0.5 to the observed data [44]. Summary effect sizes and 95% confidence intervals (CI) were estimated with a random-effects model using the Der-Simonian and Laird estimator [10]. Transformed summary effect sizes and 95% CI were converted back to proportions thereafter. Subgroup analyses were performed for selected patient cohorts (i.e., patients had to meet certain criteria to be eligible for day-case surgery) and unselected cohorts (i.e., no additional criteria for day-case surgery other than standard UKA indications), for clinical and registry-based studies, and for studies performed in the setting of a hospital outpatient pathway (HOP) or ambulatory surgery center (ASC). Heterogeneity in subgroup analyses was quantified using the I 2 measure. Due to insufficient comparative studies to perform statistical analysis between subgroups, outcomes were reported for groups without statistical comparison. Pooled means of patient characteristics and satisfaction rates were calculated. When not reported, standard deviations were calculated according to previously defined methods [43]. Analyses were performed in R version 4.1.2. (R Foundation for Statistical Computing, Vienna, Austria).
Search results
After removal of duplicates and selection based on title and abstract, 67 studies were full text reviewed. A total of 29 studies met the inclusion criteria (Fig. 1 ). Agreement on study selection was reached for all studies, hence
85%
Table 2 Quality assessment of included studies using MINORS criteria LoE level of evidence, MINORS Methodological Index for Non-Randomized Studies. MINORS criteria: 0 points when not reported, 1 when reported but not adequate, and 2 when reported and adequate; maximum for comparative studies. (1) A clearly stated aim: the question addressed should be precise and relevant in the light of available literature. (2) Inclusion of consecutive patients: all patients potentially fit for inclusion (satisfying the criteria for inclusion) have been included in the study during the study period (no exclusion or details about the reasons for exclusion). ( 3) Prospective collection of data: data were collected according to a protocol established before the beginning of the study. ( 4) Endpoints appropriate to the aim of the study: unambiguous explanation of the criteria used to evaluate the main outcome, which should be in accordance with the question addressed by the study. In addition, the endpoints should be assessed on an intention-to-treat basis. ( 5) Unbiased assessment of the study endpoint: blind evaluation of objective endpoints and double-blind evaluation of subjective endpoints. Otherwise, the reasons for not blinding should be stated. ( 6) Follow-up period appropriate to the aim of the study: the follow-up should be sufficiently long to allow the assessment of the main endpoint and possible adverse events. ( 7) Loss to follow-up \5%: all patients should be included in the follow-up. Otherwise, the proportion lost to follow-up should not exceed the proportion experiencing the major endpoint. ( 8) Prospective calculation of the study size: information on the size of detectable difference of interest with a calculation of 95% CI, according to the expected incidence of the outcome event, and information about the level for statistical significance and estimates of power when comparing the outcomes. ( 9) An adequate control group: having a gold standard diagnostic test or therapeutic intervention recognized as the optimal intervention according to the available published data. (10) [31] 2020 Knee IV 2 2 1 2 0 2 2 ----11 Barrie et al. [1] 2021 Knee IV 2 2 2 2 0 2 2 0 ----12 Keulen et al. [22] 2021 J Arthroplasty III 2 2 1 2 0 2 2 2 2 2 2 19 Lan et al. [25] 2021 J Bone Joint Surg III 2 2 1 2 0 2 2 2 2 2 2 19 Lovasz et al. [27] 2021 J Orthop Surg Rel IV 2 1 1 2 0 2 2 ----10 Mouli et al. [30] 2021 Sensors IV 2 1 2 2 0 2 2 ----11 Patel et al. [35] 2021 Knee IV 2 2 1 2 1 2 2 ----14 Saunders et al. [40] 2021 BJO III 2 1 2 2 0 2 2 2 2 1 2 18 Tveit [42] 2021 Plos One IV 2 2 2 2 0 2 2 ----14 Yang et al. [46] 2021 Bone Jt J III 2 1 1 2 0 2 2 2 1 2 2 17 Gao et al. [14] 2022 Musculoskeletal Care III 2 2 2 2 0 2 2 2 2 2 2 21
Methodological quality
A total of 27 clinical studies and 2 registry-based studies were included (Table 1 ). Thirteen studies were comparative level III studies and 16 were non-comparative level IV studies (Table 2 ). The average MINORS score was 18.7 (78% of the maximum score) for comparative studies and 11.9 (75% of the maximum score) for non-comparative studies.
Study characteristics
A total of 9694 patients were included with a mean age of 66 ± 9 years and mean follow-up of 59 days (mean range Successful same-day discharge (SDD) rates are reported per study and pooled for selected and unselected overall cohorts, as well as for the total cohort. Patient characteristics are reported as mean and standard deviation (SD), or as frequencies. Selection criteria for day-case unicompartmental knee arthroplasty (UKA) patients are reported for studies including selected patients ASA American Society of Anesthesiology, BMI body mass index, CI confidence interval, GA general anesthesia, n/a not applicable, n/r not reported or not reported for the study arm of interest, RA regional anesthesia, y years a Mean age was calculated from median age and range [43] b Cohort includes three to four patellofemoral arthroplasties c Means are reported separately for two study arms 1 3
30-270 days) (Table 1 ). Mean BMI was 29 ± 5, 85% of patients were classified as ASA 1-2, and 61% were female.
Of studies reporting SDD rates, 17 included a selected patient cohort and 7 studies included an unselected patient cohort. A summary of study characteristics is presented in Table 1 .
Successful same-day discharge
SDD rates were reported in 24 studies (2733 patients) (Table 3 ). The overall successful SDD rate across these studies was 88% (95% CI 80-92; I 2 = 96%) (Table 3 ; Fig. 2 ). Subgroup analysis demonstrated an SDD rate of 91% (95% CI 84-95; I 2 = 86%) across studies with selected patients (1553 patients), and an SDD rate of 76% (95% CI 55-89; I 2 = 96%) across studies with unselected patients (1180 patients) (Fig. 2 ). Patient characteristics per subgroup are displayed in Table 3 .
Reasons for failure to successful same-day discharge
The most frequently reported reasons preventing patients from SDD were inability to mobilize (due to pain, muscle weakness, nausea or other reasons), postoperative nausea and vomiting, inadequate pain control, and lack of confidence from the patients' perspective or lack of adequate support at home (Table 4 ). Logistical issues (e.g., surgery did not start before noon) were additional considerable barriers to SDD. Other reasons were mostly related to wound concerns, urinary retention and co-morbidities.
Readmissions, complications and reoperations
Readmission, complication or reoperation rates were reported in 26 studies (Table 5 ). The overall readmission rate was 3% (95% CI 1.9-4.4; I 2 = 80%) across all studies (8753 patients, mean follow-up 60 days) (Fig. 3 ). Clinical studies (2169 patients, mean follow-up 78 days) and registry-based (6584 patients, mean follow-up 54 days) studies had readmission rates of 3% (95% CI 1.7-4.4; I 2 = 0%), and 3% (95% CI 1.2-9.4; I 2 = 99%), respectively. Complications occurred at an overall rate of 4% (95% CI 2.8-5.2; I 2 = 72%) across all studies (8843 patients, mean follow-up 60 days) (Fig. 4 ). Complication rates were 4% (95% CI 3.0-5.9; I 2 = 42%) for clinical studies (2259 patients, mean follow-up 78 days) and 3% (95% CI 1.3-5.1; I 2 = 96%) for registry-based studies Fig. 2 Proportional metaanalysis to estimate the overall successful same-day discharge (SDD) rate after day-case unicompartmental knee arthroplasty (UKA) and SDD rates of subgroups consisting of studies with selected patients (i.e., patients had to meet certain patient-specific criteria to be eligible for day-case UKA) and unselected patients (i.e., no additional criteria for day-case UKA)
Table 4
Common reasons for the failure of same-day discharge after unicompartmental knee arthroplasty Common reasons for the failure of same-day discharge (SDD) after day-case unicompartmental knee arthroplasty (UKA) reported in included studies were classified as "inability to mobilize" (i.e., not able to mobilize due to pain, nausea, reduced muscle strength, active anesthesia or other reasons), "pain control," "postoperative nausea and/or vomiting," "logistical" (i.e., delay in surgical schedule); wound issues (i.e., leakage or other concerns), "urinary retention," "patient confidence or social environment" (i.e., lack of confidence or concerns from the patient's perspective, or lack of adequate support at home), or "other" (e.g., undefined medical reasons, co-morbidities, delay in radiographic or physiotherapy protocols interfering with discharge) Authors
Day-cases
(6584 patients, mean follow-up 54 days). The overall reoperation rate was 1% (95% CI 0.8-1.3; I 2 = 0%) for all studies (8670 patients, mean follow-up 60 days) and 1% (95% CI 0.9-1.9; I 2 = 0%) for clinical studies (2086 patients, mean follow-up 79 days) (Fig. 5 ). The overall 30-days complication rate was 2% (95% CI 1.8-2.4; I 2 = 0%) across all studies (7512 patients), 3% (95% CI 1.9-4.3; I 2 = 0%)) for clinical studies (928 patients), and 2% (95% CI 1.7-2.4; I 2 = 48%) for registry-based studies (6584 patients) (Fig. 6 ). Estimated rates of readmission, complication and reoperations are reported separately for studies performed in HOP setting and ASC in Table 5 .
Patient satisfaction
Overall patient satisfaction (688 patients) was 94%, reflecting the proportion of patients who were satisfied or very satisfied with the procedure (Table 5 ). Satisfaction rates across selected (395 patients) and unselected cohorts (293 patients) were 96% and 90%, respectively.
Discussion
The most important finding of this systematic review and meta-analysis was that day-case pathways for UKA resulted in an 88% successful SDD rate in a heterogeneous cohort of patients selected for day-case surgery and unselected patients. Successful SDD rates across studies with selected patients and unselected patients were 91% and 76%, respectively. Overall readmission, complication and reoperation rates were low and overall patient satisfaction was high (94%). These findings suggest that UKA can be performed safely and effectively as a day-case procedure, confirming our hypothesis. However, it should be noted that this applies primarily to patients who were preselected for day-case surgery, mainly based on their overall health status, motivation and support at home. Over the years, joint arthroplasty services have shifted towards enhanced recovery models. Optimization of perioperative protocols and surgical techniques have largely overcome traditional reasons for hospital admission after joint arthroplasty (e.g., pain, decreased mobility), paving the way for same-day home discharge after such procedures [4]. Several day-case UKA pathways have demonstrated excellent results in terms of success rates and adverse events [1,4,12,18,27,38]. However, most of these studies were performed with carefully selected patients, and the current literature remains divided on the feasibility of day-case UKA without preselection of patients [3,8]. Given the controversy in the literature, analyses of SDD rates in this study were performed separately for selected and unselected patients. The overall SDD rate of 76% across unselected patients appears to be lower compared to 91% SDD across selected patients. Furthermore, selected patient studies showed less variability in SDD rates compared to unselected patient studies, suggesting that outcomes may be more predictable in selected patients. Although no statistical comparison was performed, it could be argued that differences in outcome may have resulted from strict selection criteria for day-case Fig. 3 Proportional metaanalysis to estimate the overall readmission rate after daycase unicompartmental knee arthroplasty and readmission rates of subgroups consisting of clinical studies and registrybased studies surgery applied by these studies. Nonetheless, several unselected patient studies [4,8,42] had high individual SDD rates (range 88-100%), suggesting the feasibility of day-case surgery in a larger percentage of UKA patients. It should be noted, however, that these studies [4,8,42] were conducted at centers with extensive experience in fast-track protocols. It is therefore plausible that these outcomes cannot be extrapolated to less experienced centers intending to enroll unselected patients for day-case UKA.
Commonly reported reasons for failed SDD can serve to refine day-case pathways. Decreased mobility, nausea and uncontrolled pain were frequently reported reasons for SDD failure. These findings are in line with common barriers to SDD for day-case hip and knee arthroplasty [17], and essentially reflect the traditional rationale for hospital admission after joint arthroplasty. Saunders et al. [40] found a failure of SDD was strongly associated with the use of opioids in spinal anesthetics, whereas Kort et al. [24] reported uncontrolled pain as the main factor for failed SDD, using an opioid-sparing pain protocol. These findings emphasize the complexity of perioperative protocols for SDD pathways and demonstrate a need for improved anesthesia and multimodal pain control strategies. Additionally, a lack of patient confidence and logistical issues were important reasons for failed SDD. In particular, reserving morning slots for daycase procedures appeared critical to allow patients and staff sufficient time to prepare for home discharge [5,18,20]. In studies analyzing characteristics of patients who failed SDD, it was further found that these patients were significantly older [29,42], more frequently female [22,29], and had higher ASA scores (> II/III) [22,42] compared to patients with successful SDD. As noted by Tveit [42], these characteristics reflect some of the commonly reported selection criteria to determine eligibility for day-case UKA [15,18,38], thereby affirming the relevance of these criteria.
Although a shorter length of stay following UKA could prevent hospital-acquired complications, a few authors have raised concerns about the safety of day-case pathways following increased rates of adverse events compared to inpatient pathways [28,32]. Nonetheless, larger and more recent studies have demonstrated that day-case arthroplasty leads to similar [3], or reduced rates [16,25] of readmission and complication compared to (matched) inpatient controls. The current study found readmission, complication and reoperation rates, comparable to those reported for inpatient UKA [2,16,25]. Interestingly, subgroup analyses of these outcomes for clinical and registry-based studies revealed differences in heterogeneity, with no or little heterogeneity across clinical studies. This suggests heterogeneity across clinical studies was likely caused by sampling error rather than true between-study differences and contributes to the robustness of these results. Additionally, we reported complication rates separately for studies performed in an ASC or HOP setting. Due to the unique setup of ASCs, which are commonly not affiliated with inpatient hospitals and often have limited resources, it is important to appreciate outcomes independently for each setting. Readmission, complication and reoperation rates were low for both settings, suggesting day-case UKA can be performed safely in either ASC or HOP setting.
Overall, UKA appears to be an effective and safe day-case procedure. Key factors to ensure successful results lie mainly in the foundation of a well-designed multidisciplinary protocol, educational programs to inform patients, and logistic strategies to prioritize day-case procedures. Improvements are to be made in the consideration of anesthetics and strategies to optimize mobilization, prevent nausea and control pain [20,24,29,40]. Unless clinical teams already have extensive experience with fast-track or day-case UKA, it seems advisable to use carefully considered criteria for the selection of day-case patients [4,42]. Finally, it is worth noting that a day-case pathway may cause a shift of patient care responsibility from healthcare systems to patients' social environments, potentially necessitating caregiving during the early postoperative period [4,8]. This further emphasizes the relevance of patient selection and preoperative education. Further research on the generalizability of day-case protocols with regard to both patient selection and hospital setting is needed, ultimately leading to a clinical tool to help determine suitability for day-case UKA.
This study recognizes several limitations. First, this is a systematic review of level III and IV studies with an inherent risk of methodological bias, as was reflected in the suboptimal MINORS scores and may have influenced the results of this study. Second, included series were largely performed by experienced surgeons in devoted fast-track settings. Patients selected for day-case UKA (even when labeled as unselected) may often be healthier than average arthroplasty patients. It is likely that a selection bias inherent to the included studies is present, limiting generalizability to less experienced centers. Third, analyses of readmission, complication and reoperation rates were not adjusted for the follow-up period. Nevertheless, the majority of studies had a follow-up period around 90 days and a separate analysis was performed for studies reporting 30-day complication rates. Fourth, there was substantial statistical heterogeneity in the analysis of SDD rates, resulting in decreased certainty of the estimated overall effect and effect estimates of each subgroup. Although random-effects models were undertaken to incorporate heterogeneity among studies, the observed heterogeneity should be considered when interpretating these results. Finally, due to a lack of direct comparative studies of selected and unselected patients, it was not possible to statistically compare subgroups. Therefore, outcomes were only described per group. Nonetheless, this study provides a clear overview of success and complications rates after daycase UKA and may serve as a supportive aid for clinicians.
Conclusion
Supplementary Information
The online version contains supplementary material available at https:// doi. org/ 10. 1007/ s00167-022-07094-0.
Author contributions TB: study design, data screening and extraction, data interpretation, and manuscript preparation. JPL: study design, data interpretation, and manuscript preparation. LR: data screening and extraction, data interpretation, and manuscript preparation. HAZ: study design, data interpretation, and manuscript preparation. GMMJK: study design, data interpretation, and manuscript preparation. ADP: study design, data interpretation, and manuscript preparation. All authors have read and approved the final manuscript.
Conflict of interest All authors declare no conflict of interest.
Ethical approval Ethical approval was not applicable for this study.
Informed consent Informed consent was not applicable for this study.
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Funding
Funding This study received no funding. Declarations
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